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HomeMy WebLinkAbout1980-81Geotech Report Volume 2 App G-AcresF16:11AMM c MUM a no WTAI 11: 9 1 [01 IN 1. VOLUME 2 APPENDIX G - DEVIL CANYON BORROW SITE INVESTIGATION G,1 - BORROW SITE G H - SEISMIC REFRACTION SURVEY - 1980 I - SEISMIC REFRACTION SURVEY - 1981 J - AIR PHOTO INTERPRETATION K - RESERVOIR SLOPE STABILITY APPENDIX G DEVIL CANYON BORROW AREA INVESTIGATION EXPLANATION OF SELECTED SYMBOLS MORGANIC MATERIAL ® CLAY ® SILT [>:<1 SAND 12GRAVEL STANDARD SYMBOLS COBBLES B 8OULDERS �-A<y IGNEOUS ROCK 000NGLOMERATE EM METAMORPHIC ROCK SANDSTONE IN ICE, MASSIVE MUDSTONE ICE - SILT ® LIMESTONE ® ORGANIC SILT SANDY SILT SILT GRADING TO SANDY SILT Eg'�eQ SANDY GRAVEL, SCATTERED COBBLES (ROCK FRAGMENTS) 'qoa' INTERLAYERFD SAND 9 SANDY GRAVEL SILTY CLAY w/TR. SAND SAMPLER TYPE SYMBOLS St. 1.4" SPLIT SPOON WITH 47 # HAMMER Ts . SHELBY TUBE Ss . 1.4" SPLIT SPOON WITH 140# HAMMER Tm.. , , µOWFIED SHELBY TUBE SI ..... 2.5" SPLIT SPOON WITH 140# HAMMER Pb ... , PITCHER BARREL Sh . ... . 2.5" SPLIT SPOON WITH 340# HAMMER Cs .... CORE BARREL WITH SINGLE TUBE SA ..... 2.0" SPLIT SPOON WITH 140# HAMMER C0 .. .. CORE BARREL WITH DOUBLE TUBE Si , .. .. L4" SPLIT SPOON WITH 3400 HAMMER Bs .. . BULK SAMPLE Sp ..... 2.5" SPLIT SPOON, PUSHED , A. .. AUGER SAMPLE Hs .. ... 1,41" SPLIT SPOON DRIVEN WITH AIR HAMMER G. , . GRAB SAMPLE HI , , 2.5" SPLIT SPOON DRIVEN WITH AIR HAMMER NOTE: SAMPLER TYPES ARE EITHER NOTED ABOVE THE BORING LOG OR ADJACENT TO IT AT THE RESPECTIVE SAMPLE DEPTH, BORING NUMBER,T H. 30- I DATE ORILLED_10-21-60 SAMPLER TYPE Ss WATER TABLE �� s 9#— W. D. Ss FROZEN GFt7UNO -� Cd TYPICAL BORING LOG S El., 274,E—ELEVATION IN FEET All Samples SssSAMPLER TYPE ORGANIC MATERIAL 0' nva. Visible Ice 0-T ICE+ML I ICE -SILT !imate 65% Visible Ice 90, 56.2% STRATA CHANGE 7 SANDY SI LT — 'APPROxluATE STRATA cHAAe6e 12, Little IaNOVisible Ice 13-30` Vs —ICE, DESCRIPTION a CLASSIFICATION 2 72, 573 a/ , 85.9 p e f, 2 8 ° GP (CORPS OF ENGINEERS METHOD) p ``UNIf7EDORFAA CLASSIFICATION \TEMPERATURE, F DRY DENSITY WATER CONTENT BLOWS/FOOT SAMPLE NUMBER SANDY GRAVEL 95 2G SCHIST —GENERALIZED SOIL OR ROCK DESCRIPTION IPLE LOCATION 30' TO. —TOTAL DEPTH DRILLING SYMBOLS WD: While Drilling AIl: After Boring WL: Water Level TD: Total Depth. WS. While Sampling Note: Water levels indicated on the boring logs are the levels measured in the boring at the times indicated. In pervious unfrozen soils, the indicated elevations are considered to represent actual ground water conditions. In impervious and frozen soils, accurate determinations of ground water elevations cannot be obtained within alimited period of observation and other evidence on ground water elevations and conditions are required, PREPARED BY, PREPARED FOR, 0. ::►: :% EXPLANATION OF SELECTED SYMBOLS R&M CONSULTANTS, INC. SOI LS CLASSIFICATION AND CONSISTENCY CLASSIFICATION: Identification and classification of the soil is accomplished in accordance with the Unified Soil Classification System. Normally, the grain size distirbution determines classification of the soil. The soil is defined according to major and minor constituents with the minor elements serving as modifiers of the major elements. Minor soil constitutents may be added to the classification breakdown in accordance with the particle size proportions listed below; (i.e., sandy silt with some gravel, trace clay). no call - 0-3% trace - 3-12% some - 13-30% sandy, silty, gravelly - >30% Identification and classification of soil strata which have a significant cobble and boulder content is based on the unified classification of the minus 3 inch fraction augmented by a description (i.e., cobbles and boulders) of the plus 3 inch fraction. Where a gradation curve, which includes the plus 3 inch fraction, exists (samples from test trenches and pits) a modifier is used to describe independently the percentage of each of the two plus 3 inch components, If there is no gradation curve incorporating the plus 3-inch fraction (as in auger holes), the plus 3-inch material is described as a single component (i.e., cobbles and boulders), and a modifier is used to indicate the relative percentage of the plus 3-inch fraction based on the field logs. The modifiers in each case are used as follows: Scattered - 0-40% Numerous - >40% SOIL CONSISTENCY - CRITERIA: Sail consistency as defined below and determined by normal field and laboratory methods applies only to non -frozen material. For these materials, the influence of such factors as soil structure, i.e. fissure systems, shrinkage cracks, slickensides, etc., must be taken into consideration in making any correlation with the consistency values listed below. In permafrost zones, the ' consistency and strength of frozen soils may vary significantly and unexplainably with ice content, thermal regime and soil type. Cohesioniess Soils N Cohesive Soils N blows/ft Relative Density (blows/ft) qu - (tsf) Very Loose 0 - 4 20% Very Soft 0 - 2 0 - 0.25 Loose 4 - 10 20 to 40% Soft 2 - 4 0.25 - 0.5 Medium Dense 10 - 30 40 to 60% Medium 4 - 8 0.5 - 1.0 Dense 30 - 50 60 to 80o Stiff 8 - 15 1.0 - 2.0 Very Dense >50 >80% Very Stiff 15 - 30 2.0 - 4.0 Hard >30 >4.0 * Standard Penetration "N": Blows per foot of a 140-pound hamster falling 30 inches on a 2-inch OD split -spoon except where noted. Often the split -spoon samplers do not reach the total intended sample depth. Where this occurs the graphic log notes a refusal (Ref.) and give an indication of the cause of the refusal. Tight soils are indicated by a blow count value followed by a penetration length in inches. The presense of large rock fragments is indicated by a cobble and boulder callout following the refusal callout. In certain instances a blow count of 100+ may be listed to indicate tight soils where total sampler penetration is possible with more than 100 blows per foot. PREPARED By PREPARED FOR, R&M CONSULTANTS, INC. G.] BORROW SITE G AUGER HOLE LOGS AH-G4 7-22-80 Sp I ORGANIC flATERIAL SP 2 Seasonal Frost S' Sl 3 53 SILTY SAND AND SAND W/TRACE SILT Gray -Tan —3' 'T 4 -9 4 Si P S 1 U5 89 SANDY GRAVEL W/TRACE SILT Brown to Grav, Subangular to Subrounded S1 Refusal Scattered Cobbles, 6'-11' Sl 1'1%1_". V) Refusal S1 Refusal Boulder at 11', Refusal ll'T.D. WATER TABLE NOT ENCOUNTERED PREPARED BYE PREPARED FOR, 0 BORROW AREA G R&M CONSULTANTS, INC. AUGER HOLE AH-G4 Scale 1"=2' AH-G9 Elevation 982.0' 8-22-81 0.0' Sp ^• l ORGANIC MATERIAL 0,5' Sp • ,, 2 SILT WITH SOME ORGALNTCS AND 'TRACE SAND Gray -Brown l . 5 ' SAND WITH SOME GRAVEL Im AND TRACE SILT Gray Tm 4 Sh 5 8, Sp-SM ;e. Sh © 10,SP-SM o .p• Sh 09, Sp-SM Sh O 13: SP-SM r.� 12.5' Cobble Sh -o 15.0 Ref., Cobble_ T SANDY GRAVEL Gray 15,0'-22.0' Scattered to Numerous Cobbles and Boulders -- - --- --- •'---3 0. 0' 30.0 Sh o o. 1 Ref., 32/2" o'Q .v 4. .:6aA '0 Sh 4 a 0° 95 a 22.0'-39.0. Scattered d' CoiDbles d o.�•a d SANDY GRAVEL lJa• d d Sit 49 T13 a 42. 0' --44. 0' Cobble Layer .o a Sh .: u 0104, 3 . 7 0 , 130.9 Pcf . , C[I-GP d•b vodu 44.0'-50.0' Scattered 0 -'X Cobbles . a.p. :;;r; Sh 5 34, 6.8% 98.7 pcf.,SP SAND WITH TRACE rIL'Z' BRAY 52.0'-55.0' Cobble •� Layer Water Table Not Encountered. T,D. PREPARED BY; PREPARED FOR= BORROW AREA G AUGER HOLE AH-G9 R&M CONSULTANTS, INC. Scale: 1"-4 AH-G10 Elevation 980.0' 8-26-81 0.01 Sp 1 ORGANIC MATERIAL Sp SILTY SAND WITH SOME ORGANICS ' Gray Brown 1.5` Tm 3 SILTY SAND Gray Sh ®4, 30.90, 72.7 pcf.,SM Sh O 10, 15.7%, 89.6 pcf., SM _ 6.01 Sh 6 11, 11.7%, 94.8 pcf., Sp-SM SAND WITH TRACE SILT ' Gray Sh 06, 22.90, 90.2 pcf., Sp-SM Sh 8 Sp -SIB 9.0' Sh Q• 9 Ref., Cobble • b• P.' .o SA14DY GRAVEL WITH SCATTERED TO Q NUMEROUS COBBLES AND BOULDERS o Grey � o o� d p Sh0 Ref., Cobble P", 19.0'T.D. Water Table Not Encountered. PREPARED BY PREPARED FOR1 16 BORROW AREA G R&M CONSULTANTS, INC. AUGER HOLE AH-G10 Scale: 1"=3 AH-Gil 8-26-81 0.0' Sp vZ'� 1 ORGANIC 2IATERIAL 0.4' Sp ' SILT WITH SOME ORGANICS AND TRACT: SAND Brown Tm Sh ® Ref., Cobble Sh 3 16 Sh ®: 6 15, 16.326, 110.8 pcf.,SM o � Sh 7�32, 14.70, 119.6 pcf.,SM SAND WITH SOME SILT AND A, ► GRAVEL Light Gray 'per as. •'i O •: 2 .i• — —15.0' _15.0' Sh' ®32, 11.2%, 128.9 pcf.,SM ' t ' ' GRAVELLY SAND WITH SOPS SILT Light Gray 0. Sh �• O 51 SM Q' Sh 80 SM b �a• •A. Sh� 110 sM 1.0' T.D. Thermal Probe Installed to 31.0' Water Table Not Encountered. PREPARED BY S PREPARED FORt BORROW AREA G AUGER 130LE AH-Gll R&M CONSULTANTS, INC. Scale: 1"-3 All-G12 0.01 8-27-81 0.0' Sp ORGANIC MA'1TERIAL 0.3' Sp 2 SILT WITH SOME ORGANICS AND TRACE SAND Brown Sh 0 9 Sh ® 8 4.0' 8.:a Sh 5 14, SP GRAVELLY SAND a Grav Sh °..D: GO 8, Sp 6.01 o• Sh J� Oa . 7053, 6.8%, 137.2 pcf. . , GV-G'M Sh.!!.a': 8 5[i 143 . 2 Pc . GP-GMr 0 7 . 1, Sh $'p ® 52, GP --GM •a• ° SANDY GRAVEL WITH TRACE. Or SILT a 0•. •Q;c� Gray 4 Sh 0 ARGILLITE Sh i L//1 1 * Blow Counts Not Available Thermal Probe Installed to 13.5 ft. PREPARED 8Y; PREPARED FOR ' BORROW AREA G AUGER HOLD: All-G12 R&M CONSULTANTS, INC. Scale: 1"=3' AH --G13 8-28-81 0.0' Sp zzz 1 ORGANIC MATERIAL 0.31 Sp • 2 SAND WITH SOME ORGANICS AND TRACE SILT Gray Tni.' 3O 3.01 Sh '•".:_;'•. ®24, 24.74, 98.6 pcf . , SW--SM Sh •::'.• SO13, 180, 101.6 pcf. , Si -SM 7.01 a Sh O 3, 20.2%, 100.7 pcf.,Sw-SM Sh O 36, 25.50, 97.1 pcf.,SW-SM SAAD WITH TRACE SILT AND GRAVEL Gray 11.5'-13.5' Scattered Cobbles SILT WITH SOME SAND Gray Sh.' ® 10 , ML -ME Iw A SILT WITH SOME SAND AND SOME TO TRACE CLAY Gray .r �. -20.0' — 2 0.0 ' Sh a'�. 9 12, GM-SM� o• SANDY GRAVEL WITH SOME SILT -q 'O V Gray d�; - •o —2 5. 0 ' S,- 35 , Sw-SM O_ p o� GRAVELLY SAND WITH ° • TRACE SILT a•o. ° ®f-6O Gray o V' o Sh o �Fl 1 95 Sh 2 106 , SW-SM o• 26 5' --35 0' Scattered . s.s . . Cobbles p�s o • . b p O 6 • 35.0' T.D. Thermal Probe Installed to 33.0' PREPARED BY; PREPARED FOR; BORROW AREA G AUGER HOLE AH-G13 R&m CONSUL7A1dTS, INC. Scale: 1"=3' AH-G14 t3-29-81 .0 -- - - -- —�3.0' Sp N ry 1 ORGANIC MATERIAL 0-5 � SILT WITH SOME SAND, Sp O SOME TO TRACE CLAY AND ...... PEAT Brown TRACE GRAVEL. Sp .. ,.. Gray Sh 67, 23.5%, 101.4 pcf.,ML-MH Sp /1v ni ... 4 N N Sp N O 4.5' ^—��— 27.5' Sp SILT WITH SOME ORGANICS r; � 27 . 5' -29 . 0' Gravel Brown 5.3' — — e and Boulders. Sp 7 29.01 Sh,': 8 27, SM T.D. SAND WITH SOME GRAVEL Water Table Not Encountered ,_. AND SILT Gray Thermal Probe Installed to 29.0' Shy-.,-`. 9U19, .9.20, 135.5 pcf.,SM Sh '; .': 10 44, 9,90, 129.5 pcf. ,8P-SM .rr SAND WITH SOME GRAVEL ji AiiD TRACT; SILT 4' Gray d- O�A Sh 1 Ref.,Cobble, SP-SM v qp .4 -0. 12.0'-18.5' Scattered Cobbles Sh �...Q 2 89, 7.0%, 138.1 pcf. SP-SM b•'n d� ,Q 23.0' PREPARED BY PREPARED FOR: BORROW AREA G AUGER HOLE AH-G14 R&M CONSULTANTS, INC. Scale ;1"=3' TEST PIT/TEST TRENCH LOGS -LV o �o ao O -2b } C) w -30 47° DISTURBED SLOPE 0 V 42' DISTURBED O SLOPE a -35 B WA ^ •I -40 _ter.^. � - - �'�s !f -45 I 120+00 160+00 150�D0 l4D+DO 130+00 100%ORGANICS F- w 2 O J w 100°Y,SAMD 100%SILT 100%GRAVEL AZIMUTH _� I80e OF SECTIONS A A. 'cJ••• 70a00 80+00 90+00 100400 GRAIN SIZE ANALYSIS DATA IOD%cgBBLEs LABORATORY AND FIELD ESTIMATED GRAIN SIZE DATA, FOR EACH SOIL STRATA, HAVE BEER PLOTTED ON THE ADJACENT TRIANGULAR DIAGRAMS. INDIVIDUAL SAMPLES APPEAR AS SMALL TRIANGLES AND THE DASHED LINE AREAS ARE USED TO ESTIMATE THE RANGE OF TEXTURES THAT MAY OCCUR WITHIN EACH STRATA, THE DIAGRAM PROVIDES A BASIS FOR GRUUPING THE SOILS AND REVEALS THE SIGNIFICANCE OF DIFFERENCES BETWEEN GROUPS. AS THE ENERGY OF THE FLUVIAL ENVIRONMENT DECREASES (FROM A RIVERBED TO OVERBANK DEPOSITION) THE SOILS FOLLOW A "W" SHAPED PATTERN, INITIATED BY A DECREASE IN THE COBBLE CONTENT AND AN INCREASE IN GRAVEL, CONTINUED DECREASES IN THE ENERGY OF THE DEPOSITIONAL ENVIRONMENT CAUSES, LN-TURN, A RELATIVE DECREASE IN THE GRAVEL CONTENT, THEN THE SAND CONTENT AND INCREASES IN THE SILT CONTENT, DURING AND AFTTR THE DEPOSITION OF THE SANDY AND SILTY OVERBANK DEPOSITS, ORGANIC MATERIALS ACCUMULATE IN SURFICIAL LAYERS OF THE MINERAL SOILS AND AS AN ORGANIC MAT. 5 C 10 20400 37°DISTURBED SLOPE 30+00 40+00 DESCRIPTION ORGANIC MAT (PT), BLACK TO DARK BROWN PARTIALLY 50+0o A DECD:IPOSE➢ AND UNDECOMPOSED VEGETATIVE MATTER; COMPARABLE TO THE "0' SOIL HORIZON, 60+00 ORGANIC SILT (OL). RUSTY BROWN SILT CONTAINING THE © SAMPLE LOCATIONS SAMPLE NUMBER EXTENSIVE ROOT SYSTEM OF TUE SURFACE BRUSH; COM- "B" & PARABLE TO THE SOIL HORIZON, SILT WITH SOME SAND AND SANDY SILT (ML). INTER- / LAYERED (11" TO 3" LAYERS) WITH BROWN OVERBANK BOULDER (FLOOUPLAIN COVER) ALLUVIAL DEPOSITS, SAND (SP), VERY WELL SORTED, GRAY, SAND LENSES OCCURRING WITH THE SILTS OF STRATA C. STRATA CONTACT ORGANIC SILTY SAND (SH), SLIGHTLY MORE COARSE- GRAIALD EQUIVALENT OF STRATA B, CONTAINING A ROOT SYSTEM; COMPARABLE TO THE "B" SOIL HORIZON, GRADATIONAL S7itATA CONTACT SAND WITH SOME SILT (SMI, BROWN, SLIGHTLY MORE COARSE-6RAINED EQUIVALENT OF STRATA C, AND OVERBANK CONTACT BETWEEN UNDISTURBED FLUVIAL DEPOSIT OF THE SUSTTNA AND CHEECHAKO STREAM STRATA AND DISTURBED (FAILING) SYSTE,`1S, TRENCH WALL DOES NOT CORRESPOND TO A STRATA CHANGE. SANDY GRAVEL (GP-GW). BROWN TO GRAY SANDY AND ;i GRAVELLY FLUVIAL DEPOSITS, PROBABLY GRADATIONAL BETWEEN THE RIVERBED AND OVERBANK DEPOSITS OF THE SUSITKA AND CHEECHAKO STREAM SYSTEMS, SANDY GRAVEL WITH SCATTERED TO NUMEROUS COBBLES AND SCATTERED BOULDERS (GP, GW, SP,.SW), VERY COARSE - GRAINED lUP TO ABOUT 501 COBBLES AND BOULDERS) RFVER- BE➢ AND/OR ALLUVIAL FAN DFPOSITS OF THE SUSITNA AND CHEECHAKO STREAM SYSTEMS, SANDY GRAVEL AND GRAVELLY SAND WITH TRACE SILT AND y NUMEROUS COBBLES AND SCATTERED BOULDERS (SW, SP, GP, GW), EXTREMELY COARSE GRAINED (OVER 602 COBBLES AND BOULDERS) RIVERBED AND/OR ALLUVIAL FAN DEPOSITS OF THE SUSITNA AND CHEECHAKO STREAM SYSTEM: SIMILAR TO STRATA 0, 5 NOTES: A 0 1, REFLRENCE ELEVATIONS FOR EACH TRENCH ARE ARBITRARY C AND INDEPENDENT (0,0 FT, ELEVATION IN TT-51 DOES R I NOT CORRESPOND TO THE 0.0 FT, ELEVATION IN TT-G2), F 0 0 D -s 2, THE UNIFIED SOIL CALL -OUTS ARE BASED ON THE F { �}'" •, D MINUS ;-INCH FRACTION, AND WHERE APPROPRIATE r , M ARE AUGMENTED BY DESCRIPTIONS (1,E, SCATTERED w • -)0 & NUMEROUS) OF THE PLUS 3-INCH FRACTION, THE TERM SCATTERED IS USED WHEN LESS THAN 40% OF THE SOIL IS COMPOSED OF COBBLES OR BOULDERS, WHILE NUMEROUS IS USED FOR COBBLE AND BOULDER -15 CONCENTRATIONS ABOVE 401. -20 0 5 10 FEET SCALE EXPLORATORY TRENCH NO. TT-G2 I 20+DO I 30+D0 1 50,00 40+00 60+00 70.00 00+00 90+00 E I10+00 100+00 F.. 1 120+00 130+00 10+00 0 00 LABORATORY TEST DATA M O 0 OD 0 z LE c7 o a � a » tU z° 0 z w } F- a o a Q Q n U �- Z f11 Ld N ~ I- Z Q m O a Q N cr x O 0 m U Q J LL Wm O F� O U .r.l 0� O to w U o a z z F- U w � N O .r4 O a a E-+ � H ae r` oo A p O rn �0 H a 2 F- z rn r �o w U Q w O 00 CI Ol c p[ w SEES 0 SOME MEN 9515,60111'. 01, -.1m. S 1. MEN 1 u in I Ommmils will Ill.. long commusimmingle �e F- 0 z N Y tr a w W IN M tH 0 N 6 r1 z co � W a O r-I N O Z O W } �- Ir a ¢ 0 0. U H z CO W N F' I- z a � I- O J F, � a N cc z O O m U a J LL O Cn U • rl H N O Id U � •rl O �4 � Lf -P (A •rl Ln N O U] Q) � UW FC� < O ¢ z z U U 0 H 0 Ir a 11. 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This report reflects your comments and those of Acres American to our draft report dated October 23, 1980. As requested by Mr. Robert Henschel of Acres American in our meeting earlier this month, we are preparing a set of recommended additional surveys to investigate areas where uncertainties still exist. These recommendations will be forwarded under separate cover. Mr. Henschel also requested revision of the profile figures in this report to reflect true elevations rather than relative elevations. We will make the appropriate changes and forward revised drafts when datum elevations become available. We have enjoyed working with you on this project. Please call us if you have any questions or comments. Very truly Jan D. Rietman, Ph.D. Deputy Director of Geophysics JDR:DEJ/ab Enclosures Dennis E. Jensen Project Geophysicist TABLE OF CONTENTS Page LETTER OF TRANSMITTAL TABLE OF CONTENTS 1.0 INTRODUCTION ................................ 1--1 1.1 Purpose ................................ 1-1 1.2 Scope of Work .......................... 1-2 2.0 DATA ACQUISITION ............................ 2-1 3.0 DATA REDUCTION PROCEDURES ................... 3--1 4.0 DISCUSSION OF RESULTS ....................... 4--1 4.1 Traverse 80-1.......................... 4-1 4.2 Traverse 80-2.... V..$.................. 4-3 4.3 Traverse 80-3.......................... 4-5 4.4 Traverse 8 0 - 6 . . . . . . . . . . . . . • . . . . . . . . . . . . 4-6 4.5 Traverse 8 0 - 7 . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8 4.6 Traverse 80-8.......................... 4-9 4.7 Traverse 8 0 -- 9 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1 0 4.8 Traverse 80--11......................... 4-10 4.9 Traverses 80-12, 80-13, and 80--15 ............................ 4-11 5.0 GENERAL OBSERVATIONS AND CONCLUSIONS........ 5-1 REFERENCES FIGURES APPENDIX A 1.0 INTRODUCTION This report presents the results of a seismic refraction survey performed during June and July, 1980, on the Upper Susitna River, Alaska, approximately 125 miles north of Anchorage. The survey was performed under contract with R & M Consultants as part of their subcontract with Acres American Incorporated. Most of the survey was performed on the abutments and in borrow areas for the proposed earth and rockfill dam near the confluence of Watana Creek and the Susitna River. The locations of lines run at the Watana site are shown on Figures 1 and 2. The remainder of the survey was performed across a possible saddle dam location adjacent to a proposed concrete dam at Devil Canyon, approximately 27 miles west of the Watana site. The locations of lines at the Devil Canyon site are shown on Figure 3. 1.1 Purpose The purpose of this survey is to provide additional data for the continuing feasibility studies for the Susitna Hydroelectric Project proposed by the Alaska Power Au- thority. This survey is to supplement borings, geologic mapping, and previous geophysical surveys accomplished over the past several years. Line locations were selected by Acres American based on previous studies. Line lengths, geophone spacing and field procedures were designed to investigate the nature and distribution of bedrock and overburden materials. 1-2 1.2 Scope of Work A total of 27,800 feet of seismic line was run as 11 separate traverses. Thirty-six geophone spreads were tested at 122 shot points. The scope of the field work was limited by several factors including planned duration of the program, weather, and logistics. Several lines were deleted or altered with the concurrence of Acres and R & M field representatives. A few additional lines were added. In particular, lines planned across the river at both darn sites were not considered feasible because of the high rate of flow at that time. Deleted line locations are shown on Figures 1, 2, and 3. R&M personnel laid out and brushed all seismic lines and provided a survey of relative elevations and spacing of geophone and shot locations which had been flagged during seismic testing. The accumulated data Were reduced and interpreted in the orange, California office of Woodward -Clyde Consul- tants , Previous seismic studies by Dames & Moore, 1975, and by Shannon and Wilson, 1978, were used as background for the present interpretation. Field observations and the judgment of a Woodward -Clyde consultants' geologist, who was part of the survey crew, were included in the intotpte•- tation. 2.0 DATA ACQUISITION The majority of geophone spreads for this survey were 1,100 feet long with 100 feet spacing between geophones. Shorter spacing of 10, 20, 25, 40, and 50 feet were used where terrain limited the length of a particular spread or where greater detail was desired. For traverses of more than one spread, end geophones on adjustment spreads were located at the same point. For most spreads, shots were placed at half-geophone spacing beyond the end geophones and at the middle of the line. Explosive charges of one pound provided sufficient seismic energy for lines as long as 1100 feet. For about half of the spreads, greater depths to bedrock required shots at greater offsets from the ends to achieve re- fraction from deeper interfaces. The largest offsets were 1,000 feet from the end geophone, resulting in a shot to furthest geophone distance of 2,100 feet. Usually, an explosive charge of two pounds was required for these longer shots. For short lines explosives were not neces- sary and a hammer and plate were used as the energy source. The signature of seismic waves arriving at geophones from each shot was recorded on a geoMetrics/Nimbus model ES- 121OF 12-channel stacking seismograph. Recording gains were selected by trial and error and filters were used when background noise levels were high such as during heavy rain or near the river. The stacking feature of the seismograph employs an analog/ digital converter and an internal memory which stores wave traces from each geophone separately. A digital/analog converter is then used to display the stored traces on an 2-2 oscilloscope. The input from multiple shots can be summed into the memory and the summed or "stacked" traces dis- played on the oscilloscope. Stacking of multiple shots tends to enhance cohereht seismic signals while the in- fluence of random background noise is reduced by de- structive interference. Stacking was used on this survey for shorter lines where multiple hammer blows provided seismic energy instead of explosives. The overall ampli- tude of the single or stacked wave traces can be amplified or reduced by the seismograph before a hard copy of the record is produced by an electrostatic printer. For each shot, a field plot was made of distance to each geophone versus the time of arrival of the compressional seismic wave picked from the recorded wave trace. This was done to assure that sufficient information had been ob- tained for later interpretation. At the same time, notes were made as to terrain and exposed geologic features. 3.0 DATA REDUCTION PROCEDURES Methods of reducing raw data to values suitable for inter- pretation were generally those described by Redpath (1973). These general techniques have been augmented to some degree through our experience on past projects. First, field records were reviewed and picks of arrival times tabulated. Final time -distance plots were con- structed to reflect changes in arrival times from those used for field plots. These plots are shown in Appendix A, Figures Al through A10. Apparent layering, apparent seismic velocities, and variations in arrival times from those expected from a particular layer, were used to direct subsequent data reduction. Representative "true" velocities were calculated from differences in arrival times at each geophone from shots at opposite ends of the line. Where sufficient data were available, delay times were calculated beneath each geo- phone for each layer. Layer thicknesses were then cal- culated using the representative velocity. If sufficient information was not available for rigorous delay -time determination, approximation methods were used to estimate depths. In many cases, a layer which was well expressed on one spread, or believed to be present from previous investi- gations, would not be apparent on an adjacent spread. In these cases, a judgment was made as to the continuation of the layer, as a hidden layer or blind zone, beneath the spread in question to produce the most geologically reason- able interpretation. This often required adjustment of other layer thicknesses to account for the total delay time. 4.0 DISCUSSION OF RESULTS The locations of the seismic lines are shown on Figures 1 through 3. Profiles along each seismic line illustrating subsurface conditions interpreted from the survey are presented as Figures 4 through 13. On these profiles, layer thicknesses and surface topography are shown at a twofold vertical exaggeration. This distortion is required to illustrate the interpreted thickness of thin, shallow layers. Lines of contact between layers of differing velocities vary on the profiles according to the confidence placed on the interpretation. Solid lines represent a well con- trolled contact with depths shown probably within 15 percent of the true total depth. Dots on the line repre- sent points of control where the depth is well constrained by the data. Dashed lines are less well controlled. Short dashed lines with no control -point dots represent assumed contacts based on information other than that resulting directly from data reduction. The following paragraphs discuss the setting of each traverse, the results of our interpretation, and anomalous or ambiguous conditions which became apparent during data reduction and subsequent review of data from borings, test trenches, and surficial geologic mapping. 4.1 Traverse 80-1 This traverse consists of six 1,100 foot geophone spreads and three 225 foot detail spreads. As shown on Figure 1, the line extends northward about 3300 feet from the right abutment downstream from the proposed Watana Dam, and then northeastward an additional 3300 feet across the proposed spillway alignment. Topography is relatively steep at both ends of the line and relatively gentle elsewhere. 4--2 The interpreted profile for traverse 80-1 is shown on Figure 4'. Bedrock velocities along the line appear to be relatively uniform, ranging from 14,500 fps (feet per second) to 16,000 fps. Intermediate layer velocities range from 5,250 fps to 13,000 fps and shallow layer velocities from 1,300 fps to 3,600 fps. The lower velocities repre- sent loose surficial materials and possibly, in part, fine --grained lake deposits such as encountered in boring DR-6 (the location of borings designated DR are shown in U. S. Army Corps of Engineers [19791)• At the southern end of the line, a 50--foot-thick layer of 10,000 fps material probably represents weathered bedrock. Near the northern end of spread 80-1E, this layer thickens to over 100 feet and may represent an anomaly similar to that shown on Shannon and Wilson (1978), line 2 (SW2) to the southeast. We understand that a prominent gouge zone is exposed on the steep slopes near the anomaly shown on SW2, The anomaly on line 80--1E may represent a continu- ation of that zone in which case, its trend would be approximately N40W. A thick 13,000 fps layer is present near the center of the traverse, It probably represents weathered diorite bedrock but may be a different lithology such as volcanic rock which has been mapped in the vicinity, Another possibility is that the 13,000 fps material is part of a vertical tabular fractured or altered zone which extends from the intersection of traverses 80-2 and SW2 where material of the same velocity has been detected. Although the 13,000 fps zone is shown to be underlain by higher velocity mater- ial on Figure 5, the higher velocity material may instead be to the side. Additional refraction lines or borings will be required to resolve this possibility. 4-3 The thin irregular edges of the relict channel discussed in previous reports are apparent on spreads 80-1A and 80-1B. Channel fill beneath these lines, which is probably boul- dery glacial detritus, ranges from 7000 to 9000 fps. The configuration of the channel beneath line 80-1B is probably much more complicated than shown on Figure 4. The profile shows depths which are based on approximation reduction methods because of the complexity of the time -distance plot (Figure A-1, Appendix A) for which no reasonable mathe- matical solution could be found. Depth to bedrock is shown to be more than 150 feet but is probably highly irregular and much shallower especially near the center of the line. Boring DR-6 just southeast of the center of the line encountered bedrock at a depth of 65 feet. The channel appears to be the same as that documented by the 1975 Dames and Moore survey and on line 5W3. It is also well expressed on lines 80-2 and 80-6 which are dis- cussed in later paragraphs. The southwestern edge of the channel and the apparent thalweg are shown by dashed lines on Figure 1. The eastern edge of the channel appears to be immediately north of line 80-7 and appears to be expressed at the northern end of 80-8. 4.2 Traverse 80-2 Traverse 80-2 consists of five 1100 foot spreads on the right abutment extending from near the toe of the proposed Watana Dam, northward across the proposed spillway. It roughly parallels Traverse 80-1 between 1,800 and 2,200 feet to ,the east and southeast (Figure 1). The topography is relatively steep at the southern end and moderate to gentle elsewhere. The interpreted profile for traverse 80-2 is shown on Figure 5. 4-4 Bedrock velocities are similar to those of 80-1 ranging from 14,000 to 17,000 fps. Intermediate layers consist of thick 13,000 fps layers beneath the southern slopes and channel fill at the northern end of the line ranging from 6,000 to 8,000 fps. Near surface velocity layers range from 1250 to 2800 fps. The lowest bedrock velocity encountered on the traverse is beneath spread 80-2D and underlies an anomalously deep portion of the relict channel. Borings DR-18 and DR-19, northwest and southeast of the spread respectively, confirm the depth to bedrock shown on the profile and indicate that the rock in that area is highly fractured diorite with apparent clay gouge zones. This low velocity zone may represent a continuation of a shear zone known as "The Fins" exposed adjacent to the river to the southeast. The trend of this possible continuation projects toward the northeastern end of spread 80-1B which, as previously discussed, produced a highly irregular seismic record. The 13,000 fps layer at the southern end of the traverse appears to be weathered bedrock based on the shape and location of the layer. Line SW2 which crosses the traverse near its southern end (see Figure 1), also shows the 13,000 fps layer and the same depth to bedrock at the inter- section. A 6,000 fps layer shown on SW2 was not detected on 80-2. The 13,000 fps layer is shown on SW2 as contin- uous for about 2400 feet parallel to the river. The shape of the material shown on the profile of 80-2 (Figure 5) is not inconsistent with the suggestion by Shannon and Wilson (1978) that it may be involved in landsliding. I'M The channel fill at the northeastern end of the line consists of two distinct velocity zones similar to those detected on traverse 80-1. The southern portion of the fill ranges from 6,500 to 8,000 fps. Boring DR-20 appears to have encountered this material southeast of the line where it consists of saturated sandy gravels with finer grained interlayers. Boring DR-18, northwest of the line, appears to have penetrated lower velocity material detected at the northeasternmost end of the traverse. This mater- ial, ranging from 5,400 to 6,000 fps, appears to be mostly silty sands and sandy silts with some clay and scattered gravels and boulders. Surficial materials near borings DR-18 and DR-20 appear to be sandy silts. Seismic velocities of the surface layer near the borings are generally less than 2,000 fps. Velocities to the south along the traverse range are up to 2,800 fps and interpreted as representing more gravelly or better compacted sediments than those near the borings. 4.3 Traverse 80-3 Traverse 80-3 was run on the rugged steep slopes of the abutments across the proposed upstream portion of the dam. The profile, shown as Figure 6, is based on one 1,000 foot spread on the left abutment and three spreads, 1,000 feet, 265 feet, and 300 feet respectively, on the right abut- ment. A proposed segment of the traverse across the river was not considered feasible at the time of the survey due to high water levels, and was therefore not performed. Bedrock is shallow on both abutments. On the south side, bedrock appears to be of a uniform 15,000 fps velocity. The top of the southern slope is underlain by 5,200 fps material which may reflect frozen soil exposed in a shallow trench in that area. Farther down the slope, surficial 4-6 velocities drop to about 2,200 fps. This appears to be very loose talus on the slope, at least at the center shot point. The base of the slope is underlain by 7,000 fps material which appears to be highly weathered bedrock. Representative bedrock velocities on the north side range from about 15,000 fps near the top to as high as 22,000 fps lower on the slope. Surficial material on the north side is generally about 15-foot-thick and between 1,500 and 2,200 fps on the upper slope. Surficial material is thinner and lower in velocity near the bottom. Most of the upper slope is covered with loose talus. Geophone spread 80-3D was run parallel to the river along the north bank. This line detected a 7,000 fps layer 50-foot-thick which probably projects beneath the river. This layer was not apparent on spread 80--3C near the base of the north slope. It appears as if 80-3C was run above a resistant bedrock spur and that the 7,000 fps material is present to each side of the spur near the base of the slope. Lines 80-4 and 80-5 which were planned across the river at the proposed dam axis and beneath the upstream toe, re- spectively, were not run due to high water conditions. It may be possible to complete these lines after the river has frozen. 4.4 Traverse 80-6 This traverse consisted of one 11100 foot spread and a coincident shorter 600 foot detail spread across an appar- ently anomalous topographic depression approximately 4,000 feet upstream from the proposed dam axis on the north side of the river. The profile presented as Figure 71 shows the edge of the relict channel discussed in conjunction with Traverses 80-1 and 80-2. 4--7 Bedrock velocity ranges from 11,500 fps near the western end of the line to 20,000 fps beneath the channel. The channel appears to be filled with 7,000 fps material which also is thinly distributed beneath the western portion of the line. Overlying this is a layer of 2,300 fps material and, in part, a thin surface layer of 1,100 fps material. The increase in bedrock velocity across the traverse from west to east may be related to effects of "The Fins" shear zone which is exposed about 700 feet southwest of the end of spread 80-6A. This increase in bedrock velocity east of the shear zone is also expressed on the 1975 seismic line and on SW-3 which are both to the northwest of 80-06. Progressively higher velocity zones on those three trav- erses are roughly correlatible and appear to form bands generally parallel to the shear zone. The nearest borings to traverse 80-6 are more than 1,000 feet away. The channel fill material is therefore inter- preted to be similar to that interpreted for line SW-3 and for traverses 80-1 and 80-2 as previously discussed. The 7,000 fps velocity of the fill is more uniform than seen elsewhere and probably represents an averaging of both higher and lower velocity materials such as saturated alluvium and glacial detritus. The Shannon and Wilson, 1978, interpretation of nearby line SW-3 shows a shallower channel containing 4,500 fps mater- ial within the larger relict channel feature. This layer can also be interpreted to underlie 80-6 based on the time -distance plot (see Appendix A, Figure A-5). However, the present interpretation of a slight thickening of the 2,300 fps layer is also reasonably consistent with the data. HIR Surficial materials are probably similar to those at depth but less saturated. The 2,300 fps layer may also be finer grained. The low velocity of the 1,100 fps layer suggests it is very loose and probably dry. 4.5 Traverse 80-7 Traverse 80-7 consists of two 1,100 foot spreads oriented north -south across the western end of Borrow Area D. The line is shown on both Figures l and 2. Ground surface rises gently to the north along the line. velocity analysis indicated that bedrock was uniformly 15,500 fps even though the time -distance plots showed higher values. The differences are attributed to geometry of the bedrock surface and not to lateral changes. The interpreted profile for traverse 80-7 is shown on Figure 8. The line appears to be located over the northeastern side of the relict channel. Channel fill material ranges from 7,400 to 9,000 fps. It is generally about 200-feet-deep but is shallower near the north end. At the south end, it may deepen to as much as 400 feet. Line SW3, which crosses spread 80-7A near its northern end, shows a similar depth and velocity for bedrock at that point. The velocity of the channel fill is given as 7,000 fps on SW3. Boring DR-26, which is located west of the north end of line 80-7B, encountered silty sand, clayey silty gravels, and sandy silt with boulders at depths equivalent to the channel fill material interpreted from seismic data, The velocity of surface materials along the line appears to be uniformly 1,850 fps. Several exposures along the line indicate that the upper portion of this unit consists of 4-9 boulder accumulations with little or no matrix. Borings and trenches in the vicinity have encountered gravelly sands below the immediate surface. 4.6 Traverse 80-8 The two 1,000 foot lines that comprise Traverse 80-8 extend southward from the end of line SW5 at the edge of Borrow Area D near Deadman Creek across proposed Quarry Source B as shown on Figure 2. The line crosses moderate and then very steep topography southward. Four continuous layers are interpreted on the profile presented as Figure 9. These include a shallow 1,350 to 1,600 fps layer and intermediate velocity layers of 5,000 to 7,000 fps and 8,400 to 9,000 fps. Bedrock appears to change laterally from 12,500 fps near the north end to 23,500 fps at the center, and to 16,500 fps near the south end. The highest bedrock velocity is at the middle of the traverse where the rock apparently forms a buried resistant ridge. The bedrock surface may be as deep as 500 feet at a point below the middle of spread 80-8A. At the north end of the line bedrock does not appear to be as deep as shown in Shannon and Wilson, 1978, line SW5. However, this location is near the end of both lines and additional control is lacking. It does not appear likely that hard rock is near enough to the surface to provide an adequate quarry source along the line of the profile. We have no information as to possible outcrops elsewhere within the designated area. The inter- mediate velocity layers appear to be similar to those filling the relict channel to the west as previously dis- cussed. The 5,000 to 7,000 fps layer probably represents a 4-10 younger episode of channeling and filling similar to that shown on traverses 80-1 and 80-2. Both intermediate units probably consist of saturated alluvial deposits and boul- dery glacial detritus. A number of test pits in the vicinity of the traverse indicate that the shallow materials 1,350 to 1,600 fps surface layers are highly variable. Most pits encountered loose, unsaturated silty gravely sands. 4.7 Traverse 80-9 Traverse 80-9 was a single 1,100-foot-line at the western end of Borrow Area H extending upslope from previous line SW14. The present interpretation, shown on Figure 10, is in good agreement with that line. A relatively uniform mantle of low velocity material (1,100 to 1,800 fps) appears to cover the slope 30 to 50 feet deep. Shallow exposures suggest that the 1,100 fps ma- terial at the base of the hill is a loose gravel. Higher on the hill, the surface is mantled by organic soil. A higher velocity layer (6,000 to 7,250 fps) underlies the surficial deposits and thickens northward. These vel- ocities are similar to those of saturated alluvium and glacial detritus found elsewhere. Bedrock with an approxi- mate velocity of 15,000 fps, is about 100 feet below the surface at the base of the hill and may be as deep as 300 feet at the north end of the line, 4.8 Traverse 80-11 This traverse was run North and west of Tsusena Creek near the eastern end of. Borrow Area E. The alignment was changed from east of the creek when surface reconnaissance showed that area to be underlain primarily with boulclery glacial deposits, 4-11 Spread 80-11A was run from the bank of Tsusena Creek northward 1,100 feet across gentle topography to the base of a hill (Figure 2). A second 1,100 foot spread, 80-11B, was run from the center of the first in a northeasterly direction. This line hd not been previously staked or brushed and when surveyed later, was found to bend to the north as shown on Figure 2. Two shorter detail spreads (80--11C and 80-11D) were also run near the middle of spread 80-11A. On the southern end of the traverse 80--11A, a 2,800 fps layer of loose surficial deposits appears to be about 30 feet thick and thins to the north. This appears to be underlain by a 11,000 fps weathered bedrock layer about 100 feet thick which also thins to the north. Bedrock velocity beneath the area is between 16,000 and 17,000 fps. in the northern part of the area the 11,000 fps layer wedges out beneath an apparent relict channel filled with 5,000 fps material which may be loose saturated sands and gravels. A 7,000 fps intermediate zone at the north end of spread 80-11A is not apparent on 80-118. Instead, the northern part of 80-11B shows shallow bedrock beneath about 20 feet of 1,400 fps surficial deposits. The 7,000 fps material may be similar to the relict channel fill detected on lines previously discussed. 4.9 Traverses 80-12, 80-13, and 80-15 These three traverses were run across a small lake and on the adjacent slopes above the left abutment of the proposed Devil Canyon Dam as shown on Figure 3. Traverse 80--12 consisted of a 250 foot hydrophone spread across the western part of the lake and two 500 foot geophone spreads 4-12 Up steep adjacent slopes to the north and south. Traverse 80-13 consisted of a similar combination across the eastern part of the lake. Traverse 15 was a single hydrophone line, 500 foot long; extending northwest to southeast across the lake. The profiles shown on Figures 12 and 13 indicate similar bedrock velocities of between 16,800 and 18,800 fps. Profile 80-12 shows a distinct intermediate layer beneath the slopes of between 7,000 and 10,000 fps. This may be highly weathered bedrock or glacial deposits. A 5,000 fps intermediate layer beneath the relatively flat north end of 80-13, probably indicates water table in otherwise low velocity sediments. Surficial deposits on the slopes are generally between 1,400 and 2,200 fps. The 4,000 fps indicated beneath the north -facing slope on line 80-13 probably represents partically frozen ground. A layer of approximately 5,000 fps underlies the lake on all three profiles. This is probably saturated soft sediments which may be as deep as 50 feet near the center of the lake as shown on profile 80-15, Time -distance plots from all three spreads run across the lake are very ir- regular and subject to alternative interpretations. Data from spread 80-15 appear to indicate that high -velocity bedrock directly underlies the saturated sediments beneath most of the lake. The other two profiles, However, indi- cate that only weathered rock is present beneath part of the area. The possibility of a shear zone trending apprdkimately east -west beneath the lake Was suggested by dhalhoh and Wilson (1978) based on results of liho 8W-171 which par- allels 80-121 400 feet to the west, Oh that line; bedrock 4--13 velocities underlying 7,000 fps channel fill near the center of the line were interpreted to be lower than beneath the slopes to either side. Three of 5 borings drilled along that line encountered highly fractured or sheared phylltic bedrock. The results of the present survey can neither confirm nor deny the presence of a shear zone. Although the time - distance plots appear to be anomalously irregular, reason- able mathematical interpretations were obtained from the data. Lower velocities were obtained for bedrock beneath the lake than on the adjacent slopes (as on SW-17) but the reason for these lower velocities is not clear from the data. They may indicate sheared material or, alterna- tively, dense fill material or weathered, surficially fractured bedrock. 5.0 GENERAL OBSERVATIONS AND CONCLUSIONS Materials represented by velocity layers interpreted for this report have been assigned, at least in general terms, where boring and test pit data have been available. In areas where this control has not been available, similari- ties in layering and velocities with better controlled areas have allowed assignment of material types with a reasonable degree of confidence. In general, bedrock velocities near the Watana site vary between 14,000 and 23,000 fps. Velocities of 18,000 to 23,000 fps are representative of hard, unfractured diorite as exposed in the immediate site vicinity. Lower veloci- ties indicate increasing degrees of fracturing and weather- ing if the rock is indeed diorite. These lower velocities may also represent other lithologies such as metamorphic zones or volcanics such as have been mapped on the right abutment downstream from the dam. Velocities as low as 10,000 fps in intermediate layers overlying higher velocity bedrock may represent highly weathered diorite. Apparent layers of 13,000 fps material found near the middle of traverse 80-1 and at the south end of 80-2 have been interpreted as weathered bedrock but may represent a different lithology. Lateral changes in bedrock velocity have been noted on several lines for this and previous surveys near the Watana site. These changes appear to form bands of increasing velocity eastward from "The Fins" shear zone as presently interpreted, and may also form northwest trending bands farther to the west. Present data, however, is insufficient to verify this pattern. 5-2 Portions of the relict channel at the Watana site have been defined by the present interpretation. The channel is apparent on traverses 80-1, 80-2, 80-6; 80-71 and 80-8. Channel fill material ranges from 5,000 to 9#000 fps and has been shown by borings to be highly variable but pre- dominantly alluvial sands and gravels, bouldery glacial silts and sands, and to a lesser extent lacustrine silts and clays. Two episodes of channeling are apparent on traverses 80-1, 80-2, and 80-8. Materials on traverses 80-9, and 80-10 with similar velocities appear to be lithologically similar to those in the relict channel. At the Devil Canyon site, the highest bedrock velocity detected was nearly 18,000 fps. This is the velocity reported for fresh phyllite in the area by Shannon and Wilson (1978). Lower velocity bedrock interpreted from the present survey may reflect weathering or lateral lithologic changes. Intermediate layer velocities at the Devil canyon site range from 5,000 to 10,000 fps. Velocities as loW as 7,000 fps could represent weathered bedrock in the metamorphic terrain. The 5,000 fps layers interpreted from this survey appear to be equivalent to the 1,000 fps layer on SW-17 to the west of the lake. Borings in that area shoWed the material to be predominantly sand with some gravel and boulders. Surficial deposits are highly variable in the area of the survey and are therefore difficult to discuss in g6heral terms. Surficiai materials are best investigated With short lines and small geophone spacing: Since Moet Of the lines for this surrey used wide geophone spacinq, the information obtained about surficial layers is highly 5--3 generalized. Most of the surficial velocities reported herein are probably averages of several smaller distinct layers and are more related to the distance from shot point to the first geophone than to the velocity of any par- ticular material. With regard to structure, two possible shear zones have been interpreted from this survey. These are northwest trending zones extending from the right abutment at the Watana site and are discussed with respect to traverses 80-1, and 80-2 in earlier sections. Information regarding a possible shear zone beneath the saddle dam site at Devil Canyon was indeterminate. The data from the present survey were sufficient to make .fairly definite interpretations. However, specific depths and material types should be confirmed by borings in critical areas. We suggest that when sufficient boring control becomes available, that all three refraction surveys be re-evaluated to more accurately portray con- ditions between borings. The interpretation resulting from the present survey are considered the most reasonable based on available information. They are not the only interpretations possible. The limitations of the seismic method and the present data are discussed further in Appendix A and the references. REFERENCES Dames and Moore, 1975, Subsurface exploration, proposed Watana Dam site on the Susitna River, Alaska: Report for Department of the Army, Alaska District, Corps of Engineers, Contract DACW85-C-0004. Redpath, B. B., 1973, Seismic refraction exploration for engineering site investigations: U. S. Army Engineer Waterways Experiment Station, Explosive Excavation Research Laboratory, Livermore, California, Technical Report E-73-4, 55 p. Shannon and Wilson, Inc., 1978, Seismic refraction survey, Susitna Hydroelectric Project, Watana Dam site: Report for Department of the Army, Alaska District, Corps of Engineers, Contract DACW85-78-C-0027. U. S. Army Corps of Engineers - Alaska District, 1979, Southcentral Railbelt Area, Alaska Upper Susitna River Basin - Supplemental Feasibility Report: Appendix Part z. 2�L 27 5 FLOW FOG ,CRC. GOLD CREEK WATANA �... \�Ek SU ]�14 R'N£ \ I y DAM ✓' -� DEVIL 33 34 35 3fi 37 38 39 4D 41 qZ IF �j� ... �r � YON DAM FOG LAKES TRAVERSE qq qs L \ 4` \ tV ��P? q6 47 4� JJJ 'ley Q § S 1' SCALE 0 a e MILES ti ti ti ti a LOCATION MAP w w w w w w w w w w 2200— � H 3224,000 �1L1 ... N 3226,000 �J N_3,.228.000 ��'• SL 8€-3 sL8€-4 N 3,230DW 7\� sL w I lTOO � 180p y \gOO t900 sag` -is N 3,232,OOp ,_ CFO m Z 8t ie r ��2100 m ,54 m 2200 SL .i9 e�U N m P .N 3�234,Ow .. .- CR EEK 2300•-, �26 j oR-€s O � DR-27 a / SL st-2a WW_€ —. SW-€ s�o 3 77. SDSITNA'.._j ...� RIVER sL81''—� 0 \ �, l� J SW-2 f600 -� y / s A lTU) r o 000 — oR-€s m DR-2� dap G O oR-rr �zoo C c'� c :C ' WATANA DETAIL AREA / LOCATION OF SEISMIC REFRACTION LINKS SCALE', 1000 2000 FEET TIJN NOT SHOWN FIGURE I AGES PREPARED BY WOODWARD-CLYDE CONSULTANTS 0 1 2 3 SCALE IN MILES Foy Lakes Refraction Traverse Lines 81—FL-1 to 81—FL-48 11 / 6 f/ 5 23 1 12 �FL�W PREPARED BY WOODWARD — CLYDE CONSULTANTS 4�r_ -- `��� 33 34 41 42 28 29 48 DM-s �F06...—�R. WATANA DETAIL AREA i (Figure 1 I WATANA DAM SL-81-8 SL-81— SW-14 f / SW-13 SL 80-9 i Devil Canyon 16 Miles �a SL-81 _12 A mile A ON WATANA VICINITY MAP -- APPROXIMATE LOCATION OF REFRACTION LINES OUTSIDE DETAIL AREA p FIGURE 2 0 200 400 600 SCALE IN FEET 7450 \ 1400 1360 1300 1200 1000 $00 sW-15 SUSITNA RIVER LOCATION OF DEVIL CANYON SEISMIC REFRACTION LINES a' SL 80 15 w r 00 0 m S L-81--22 FIGURE 3 PREPARED By WOODWARD —CLYDE CONSULTANTS 008 _._......__,.�._..�... _ .lam_.-..___. -`- .�--^ _� .�.- � !__•_� 1�_�--�'--_ a +fib gI�T4?lid - 23W J �401 OA9'139 DIM212 ,k Q4r� OQP offi: 0 81 -V�J of - VV2.- .'7kUTJU,3M0:J 70YJo - oRdi".�000W 't�3 ojgA93ilq - c 0 co Q) N W 2300 2150 2000 1850 1700 1550 80---1 E 80--1 D Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 300 feet Vertical Scale: 1 inch = 150 feet SEISMIC REFRACTION PROFILE 80-1 SHEET I OF 2 2300 2150 2000 a� a� C O m 61 1850 Lu 1700 1550 NOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO RaM CONSULTANTS, 3/19/81. PRirpApr 1 Av wnnnwnon ni vnr ...,......, t... �.. FIGURE 4 a 2300 N35E 80-1A 2300 80--1 B 80-1 C 80-1G 1 12 2150 — 2150 12 1 1700 12 tz- 7000 ~ 456- \ 2000 1700 8000 12 1600 ? q1 1 2000 +� 7 .2 16000,, \ 1 5250 9000 6050 7 .2 Lu 1850 m 1850 Lu ii 14800 a� c 1700 U M 1700 14500 1550 1550 NOTE: Compressional wave velocities in feet per second ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO RaM CONSULTANTS, 3/19/81. Horizontal Scale: 1 inch = 300 feet Vertical Scale: 1 inch = 150 feet SEISMIC REFRACTION PROFILE 80-1 SHEET 2 OF 2 RC�ES FIGURE 4 b PREPARED BY WOODWARD-CLYDE CONSULTANTS North 2450 2450 802A 80-213 End of 802C 2250 2300 2100 ' 1 12 2300 2250 16900 I 16700 1v 15700 I `~ 0 2150 � � (51 2150 C • 1250 f� CM co w i -- w 13000 r • CI 2 �/ -I 2000 2000 i +L) ca 16700 I 1850 1850 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 300 feet Vertical Scale: 1 inch = 150 feet SEISMIC REFRACTION PROFILE 80- 2 SHEET I OF 2 FIGURE 5a PREPARED BY WOODWARD-CLYDE CONSULTANTS N35E —*­ 2450 1 Abuts 80-2B 80-2C Lu 15400 a7 c 2000 r U Y CO C 1850 12 ® 17 805( 13900 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 300 feet Vertical Scale: 1 inch = 150 feet SEISMIC REFRACTION PROFILE 80- 2 SHEET 2 OF 2 1 _ 1400 80-2E 2450 2300 12 c 2150 w 2000 1850 NOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO R 8, M CONSULTANTS, 3/19/81. REPARED BY WOODWARD-CLYDE CONSULTANTS FIGURE 5b North 2100 2000 1900 1800 aD a� C O ca () w 1700 1600 1500 1400 tion 11 20000 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet SEISMIC REFRACTION PROFILE 80-3 Crosses SW2 2100 1900 MORE•E a) a� C O 1700 w 1600 1500 1400 NOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO R8i M CONSULTANTS, 3/19/81. FIGURE 6 PREPARED BY WOODWARD-CLYDE CONSULTANTS 2200 2150 2100 0 2050 4.1 cc a� w 2000 1950 1900 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 50 feet SEISMIC REFRACTION PROFILE 80-6 N78E 2200 2150 2100 2050 Lu 2000 1950 1900 DOTE-. ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO RaM CONSULTANTS, 3/I9/81. FIGURE , A6NfS� PREPARED BY WOODWAAD-CLYDE CONSULTANTS 2400 - 2300 - 2200 - c 2100 0 cc a� uj 2000 1900 — 1800 — North Rn--7A Qn- -713 Cornoressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet SEISMIC REFRACTION PROFILE 80-7 1000` from Sta gwi 2300 2200 a� a� 2100 m a� w 2000 1900 1800 (VOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO Ra M CONSULTANTS, 3/19/81, FIGURE a ACBE3 --11- ui nvvu nnnu-l.L1VL IVIYJVLIANIZi 2300 - 2200 - 2100 -- c m 7 w 1900 :11 1700 - 1600 - 23500 1 1 � 12500 16 500 (j Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet SEISMIC REFRACTION PROFILE 80 m8 - 2300 - 2200 - 2100 c M - 1900 w 1800 - 1700 - 1600 (VOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO R&M CONSULTANTS, 3/19/81. FIGURE s �CBE3 'REPARED BY WOODWARD-CLYDE CONSULTANTS 1900 1900 12 1800 1800 1800 80-9 1700 1700 7250 a End of line SW14 w 1500� 0 1600 . 1600 0 iv w ` w 1500 \ \ i 1500 \ 1100 6000 1400 15000 \ 1400 1300 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet Note: Elevations adjusted to true values according to R&M Consultants, 3/19/81 SEISMIC REFRACTION PROFILE 80 - 9 I FIGURE 0 �II North 80-11A 1500 1500 Crosses 80-11 B,C,D —..- 12 1500 �.-- — 1000 ^ �— 1450 280o r —r r � — � — 5000 /� 7000 1450 0 l 1 11000 I r f ~ I 1 1 > W 1400 f 16000 I 17000 1400 i I i 16000 1350 0 � 1350 80-11B 1500 N40E �— N30E North 1500 Crosses 80---11 A 2500 1400 1000 20 1450 —�-- �_ .` 5000 16000 1450 1400 I 16000 1400 1350 1 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 50 feet SEISMIC REFRACTION PROFILE 80®11 1350 c 0 .�p w .. NOTE= ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO Ra M CONSULTANTS, 3/19/81. PREPARED BY WOODWARD-CLYDE CONSULTANTS FIGURE It �CII�S N7W`. 1500 1450 1400 L" 1350 1300 1250 N o S80E�� 1350 +, 1300 c 0 m LU 1250 16800 1350 1300 c 0 1250 LU 1200 SEISMIC REFRACTION PROFILES 80-12 81; 80-15 1500 1450 1400 c 0 +, CZ a� 1350 W 1300 1250 Compressional wave velocities in feet per second' Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 50 feet Notes: Elevations adjusted to true values according to R&M Consultants, 3/19/81 NOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO R 8, M CONSULTANTS, 3/19/81. FIGURE 12 :rAntU UY WDODWARD-CLYDE CONSULTANTS 1450 N7W --Y _ 1450 80-13C 80-13B 80-13A. 1400 1750 1400 +, 5000 } 16800 4000 0 1350 18800 c Crosses 80---15 1350 0 Lu Lake El. 1327' a`ii w LAKE �;� 1300 i 5000 1300 I 12300 1250 1250 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 50 feet NOTE: ELEVATIONS ADJUSTED TO TRUE VALUES ACCORDING TO RaM CONSULTANTS, 3/19/81, SEISMIC REFRACTION PROFILE 80- 13 FIGURE 13 PREPARED BY WOODWARD-CLYDE CONSULTANTS APPENDIX A* This appendix deleted from Task 5, Appendix H. Refer to project files for Woodward -Clyde Consultants report. APPENDIX I SEISMIC REFRACTION SURVEY-1981 SUSITNA HYDROELECTRIC PROJECT SEISMIC REFRACTION SURVEYS 1981 Submitted to R & M Consultants 5024 Cordova Anchorage, Alaska 99502 6 January 1982 R & M Consultants 5024 Cordova Anchorage, Alaska 99502 Attention: Mr. Gary Smith Gentlemen: SUBJECT: SUSITNA HYDROELECTRIC PROJECT SEISMIC REFRACTION SURVEYS - 1981 Enclosed are five copies of the subject report which docu- ments geophysical work in support of site engineering studies during 1981. At the request of Acres American Incorporated, we are also sending five copies directly to their office in Buffalo, New York. We have enjoyed working with you on this project and hope we can be of further service in the future. If you have questions regarding the material contained in this report, please call at your convenience. Very truly yours, Dennis E. Jensen Project Geologist DEJ/md Enclosure Jan D. Rietman, Ph.D. Deputy Director of Geophysics TABLE OF CONTENTS LETTER OF TRANSMITTAL TABLE OF CONTENTS LIST OF ILLUSTRATIONS Page 1.0 INTRODUCTION ................................... 1-1 1.1 Purpose ................................... 1-1 1.2 Scope of Work ............................. 1-2 2.0 DATA ACQUISITION AND REDUCTION ................. 2-1 3.0 LIMITATIONS .................................... 3-1 4.0 SPRING TRAVERSES ............................... 4-1 4.1 Traverse 81-1............................ 4-1 4.2 Traverse 81-2............................ 4-2 4.3 Traverse 81-3............................ 4-3 4.4 Traverse 81-4............................ 4-3 4.5 Traverse 81-5............................ 4-4 4.6 Traverse 81-6............................ 4-4 4.7 Traverse 81-7............................ 4-5 4.8 Traverse 81-8............................ 4-6 4.9 Traverse 81-9............................ 4-6 4.10 Traverse 81-10........................... 4-7 4.11 Traverse 81-11........................... 4-8 4.12 Traverse 81-12........................... 4-8 5.0 SUMMER 1981 SURVEYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5.1 Traverse 81-13........................... 5-1 5.2 Traverse 81-14........................... 5-2 5.3 Traverse 81-15........................... 5-3 5.4 Traverse 81-16..... ..... I ... I............ 5-4 TABLE OF CONTENTS Continued 5.5 Traverse 81-17........................... 5-5 5.6 Traverse 81-18........................... 5-5 5.7 Traverse 81-19..... 6..................... 5-6 5.8 Traverse 81-20.....................6..... 5-6 5.9 Traverse 81-21........................... 5-7 5.10 Traverse 81-22.....................6..... 5-8 6.0 FALL TRAVERSES -FOG LAKES AREA .................. 6-1 7.0 MAGNETOMETER SURVEYS......... 6................. 7-1 8.0 GENERAL OBSERVATIONS AND CONCLUSIONS........... 8-1 REFERENCES APPENDICES Appendix A Time -Distance Plots - Spring Surveys Appendix B Time -Distance Plots - Summer Surveys Appendix C Time -Distance Plots - Fall Surveys (Fog Lake) LIST OF ILLUSTRATIONS Table 1 1980 - 1981 Seismic Refraction Line Data Figure 1 Location of Seismic Refraction Lines - Watana Detail Area Figure 2 Watana Vicinity Map - Approximate Location of Refraction Lines Outside Detail Area Figure 3 Location of Devil Canyon Seismic Refraction Lines Figure 4 Seismic Refraction Profiles 81-1 and 81-2 Figure 5 Seismic Refraction Profiles 81-3, 81-4, and 81-5 Figure 6 Seismic Refraction Profiles 81-6 and 81-7 Figure 7 Seismic Refraction Profiles 81-8 and 81-9 Figure 8 Seismic Refraction Profiles 81-10 and 81-11 Figure 9 Seismic Refraction Profile 81-12 Figure 10 Seismic Refraction Profile 81-13 Figure 11 Seismic Refraction Profile 81-14 Figure 12 Seismic Refraction Profiles 81-15 and 81-16 Figure 13 Seismic Refraction Profiles 81-17 and 81-18 Figure 14 Seismic Refraction Profile 81-19 Figure 15 Seismic Refraction Profiles 81-20 and 81-21 Figure 16 Seismic Refraction Profile 81-22 Figure 17 Fog Lakes Seismic Refraction Profiles - Sheet 1 Figure 18 Fog Lakes Seismic Refraction Profiles - Sheet 2 Figure 19 Fog Lakes Seismic Refraction Profiles - Sheet 3 Figure 20 Fog Lakes Seismic Refraction Profiles - Sheet 4 Figure 21 Fog Lakes Seismic Refraction Profiles - Sheet 5 Figure 22 Fog Lakes Seismic Refraction Profiles - Sheet 6 Figure 23 Fog Lakes Seismic Refraction Profiles - Sheet 7 1.0 INTRODUCTION This report presents the results of geophysical surveys performed during the spring, summer, and fall of 1981 on the Upper Susitna River, Alaska, approximately 125 miles north of Anchorage. These surveys were performed under contract with R & M Consultants (R & M) as part of their subcontract with Acres American Incorporated (AAI). The 1981 geophysical program was essentially a continuation of surveys performed during 1980 under the same contract. Results of the 1980 surveys were submitted to R & M in a report dated 19 December 1980. Interpretations included in this report are based in part on the 1980 work, on previous seismic refraction surveys (Dames and Moore, 1975; Shannon and Wilson, 1978), and on limited boring and surface mapping information. Locations of all refraction traverses from 1975 through 1981 are shown in Figures 1, 2, and 3. Figure 1 covers the immediate area of the proposed Watana Dam site and Figure 2 shows line locations outside of the immediate site area but in the same vicinity. Figure 3 shows line locations near the proposed Devil Canyon Dam site. 1.1 Purpose Geophysical surveys from 1981 and from past years were accomplished as part of feasibility studies for the Susitna Hydroelectric Project proposed by the Alaska Power Authority. Seismic refraction and limited magnetometer surveys were intended to investigate the nature and distribution of bedrock and overburden materials and to supplement data from other sources such as borings and geologic mapping. 1-2 For all surveys run during 1980 and 1981, line locations were specified by AAI. Some of the 1981 locations were recommended by Woodward -Clyde Consultants at the close of the 1980 season, and incorporated in the 1981 program. 1.2 Scope A total of 72,900 ft of refraction line was run in 1981 during three separate field efforts (spring, summer, and fall) to bring the two-year total to approximately 100,000 linear feet. In addition, approximately 3,000 ft of magnetometer line was run near Devil Canyon in an unsuc- cessful attempt to detect buried mafic dikes. The spring seismic refraction survey consisted of 21,900 ft of line at 12 locations (Lines 81-1 through 81-12) across the river and adjacent low-lying areas near the Watana site (Figures 1 & 2). Field work was accomplished between 1 April and 14 April 1981 when the river was frozen. The low water level and low water velocity plus access afforded by ice allowed refraction surveys to be run in areas where they would be infeasible later in the year. A draft report of the results of the spring work was submitted to R & M dated 18 June 1981. A total of 22,200 ft of refraction line was run during the month of July as 10 separate traverses (Lines 81-13 through 81-22). Nine of these were run at the Watana site (Figure 1), some as continuations of existing lines. One traverse was run on the proposed south abutment at Devil. Canyon (Figure 3). From 26 October to 15 November, 1981, a 28,800 ft traverse was run from rock outcrops near the proposed Watana south abutment to a point approximately 5 miles to the east. The 1-3 locations of lines 81-FL-1 through 81-FL-48 are shown on Figures 1 & 2. This traverse crossed an area of suspected buried channels in the Fog Lakes area. The alignments of all traverses were flagged by R & M or AAi personnel prior to refraction surveying. During refraction work, the location of all shot points and geophones were flagged. The coordinates and elevations of each of the shot and geophone points for spring and summer traverses were subsequently surveyed by R & M. For the fall work (Fog Lakes) R & M provided coordinates and elevations at all turning points and breaks in slope. Data for all seismic refraction traverses accomplished during 1980 and 1981 are summarized in Table 1. The table includes line numbers used in this report, line numbers used by R & M for coordinate and elevation surveys, presen- tation data, line configuration data, and comments. This report discusses the interpretation of 1981 traverses in detail and references 1980 lines where they are in proxi- mity to the 1981 survey lines. 2.0 DATA ACQUISITION AND REDUCTION Field procedures used during the 1981 season were similar to those of the 1980 survey (Woodward -Clyde Consultants, 1980). A Geometrics/Nimbus model ES-1210F twelve -channel stacking seismograph and an explosive energy source was used for all lines. Line lengths and geophone spacing varied as discussed later in separate sections. Data reduction for the 1981 surveys was accomplished in a similar manner as for the 1980 lines, essentially following the procedures of Redpath (1973). Rigorous delay time methods were used for only a few lines for which data was sufficient and too complex for adequate interpretation by approximation methods. Time -distance plots of the data are included in Appendix A (spring surveys), Appendix B (summer surveys), and Appendix C (fall --Fog Lakes surveys). Interpretation of these lines are shown as Figures 4 through 23 and are discussed in Sections 4.0, 5.0, and 6.0. These sections discuss the setting of each traverse, our interpretation, and anomalous or ambiguous conditions which became apparent during data reduction and subsequent review of all available data. Our confidence in the contacts between layers of differing velocities on the figures is variable. Solid lines repre- sent well controlled contacts with the depths shown prob- ably within 20 percent of the true total depth. Dots on a line represent depths calculated by the delay time method or by approximation techniques. Dashed lines are less well controlled with an estimated possible deviation from true depths on the order of 30%. Queried dashed lines are 2-2 assumed contacts that are based on assumed velocities and information other than that resulting directly from data reduction, or that are inferred by the data but are not mathematically explicit. 3.0 LIMITATIONS Seismic refraction is a widely used and well suited exploration tool for engineering projects but is subject to certain limitations which should be kept in mind when evaluating the interpretations presented in the following sections. The effects of inhomogeneities, irregular contacts, "blind zones" and hard -over -soft conditions are discussed below. Other limitations which result from the site environment and from the specified scope of these surveys apply particularly to seismic work performed at the Susitna sites. The seismic refraction technique depends upon measuring the first arrival of a seismic wave at geophones placed on the ground surface progressively further from an explosive charge or other seismic source. Arrivals at nearest phones generally indicate travel directly through low -density surface materials. At points further from the source, the seismic wave arrives sooner than would be expected from travel through surface materials, having traveled in part through deeper, more dense, and therefore higher velocity layers. If subsurface layers are uniform, horizontal and the seismic velocities progressively increase with depth, a mathematical model can be developed from the arrival time data that approximates actual conditions. Several condi- tions exist in nature, however, which make interpretation of the data less precise and introduce ambiquity into the model. In ideal situations, plots of arrival times versus distance (see Appendices A, B, and C) produce straight lines, the inverse slopes of which represent the seismic velocity of the subsurface material. Deviations of the data from straight lines indicate inhomogeneity within layers, 3-2 irregular layer contacts, or inaccuracy in identification of first arrival time. Sufficient data is seldom available to distinguish amoung these possibilities. It is also difficult to determine if irregularities occur in near - surface layers or at depth. In many cases, the data resulting from local or lateral velocity changes can also be interpreted as contact irregularities. Thin layers at depth also present a problem. Ideally each layer is represented on a time --distance plot as a separate straight line. Thin layers may produce no indication of their existance in the data regardless of the detail of the survey. Such "blind zone" cases can affect the calculated depth to deeper layers, such as bedrock, by a theoretical maximum of 30 percent. Layers with seismic velocities less than overlying layers are not detectable by refraction. This situation is suspected to exist in several areas, at the Watana site in particular, where less dense sediments may underlie frozen, more dense ground. Non -seismic information, such as boring data, is required to resolve hard -over -soft conditions, enabling correction of the refraction model, which is otherwise likely to be in error by as much as 30 percent for the depth of deeper layers. Several conditions occur which preclude collection of the optimum quantity and quality of data. These include weather, ground conditions and, of course, the time available to resolve operational problems which may arise. For the Susitna work, field data reduction was performed to assure the sufficiency of results from each line. In some cases, however, time and budget constraints precluded running additional lines which may have resolved some uncertainties. 3-3 In interpreting data which is less than straight forward, the tendency is to produce as simple a model as possible without violating the restraints of the data. In these cases, the experience and judgement of the interpreter is important in producing a geologically reasonable picture. The presence of an experienced geologist during shooting of the lines and during interpretation, combined with the results of previous investigations, increased the likeli- hood that profiles presented herein reflect a fairly accurate model of existing conditions suitable for evalua- tion of the feasibility of the project. Further explora- tion is required to resolve the uncertainties identi- fied during these surveys. 4.0 SPRING TRAVERSES The twelve traverses (lines 81-1 through 81-12) run during April each crossed the Susitna River, which was almost completely frozen at the time. Geophones at ice locations were placed in holes bored through the ice to soil or, in some cases, water. The phones were then firmly affixed to the soil or river bottom by weights. Explosive charges were detonated away from the river to provide the seismic energy source. During the surveys, ice thickness ranged up to four feet with only a few open leads. The Susitna River was at its low point for the year but still retained sufficient velocity to interfere with seismic signals. Explosive charges up to 20 lbs were required to overcome the river noise in some cases. Also, seismic signals traveling through the ice at 11,000 fps ( feet per second) often masked first arrivals through shallow, less dense sedi- ments. The locations of lines 81-1 through 81-6 are shown in Figure 1. Lines 81-7 through 81-12 are shown in Figure 2. 4.1 Traverse 81-1 This traverse consists of one 1,000 ft geophone spread and three shotpoints. The line crosses the Susitna River near the mouth of Deadman Creek. The south terminus is at the base of the steep slope on the southern bank of the Susitna River while the northern terminus is at the toe of the slope at the northern side of the valley. The southern third of this line is over the ice -covered Susitna River. The interpretated profile for traverse 81--1 is shown in Figure 4. Bedrock has a calculated velocity of 16,700 fps. Bedrock appears to be very near the surface at the 4--2 southern end of the profile and reaches a depth of about 120 ft near the northern end of the profile. There is a bedrock high in the center of the profile which brings bedrock to within 70 ft of the surface at that point. An average velocity of 4,600 fps was found for the sur- ficial materials. In our experience, this velocity is typical of recent river deposits of varying saturation and grain size. 4.2 Traverse 81-2 This traverse consists of two 1,000 ft spreads and six shotpoints. The line setting is similar to that of traverse 81-1 but is 3,000 ft further west, downstream. The northern half of the traverse was over the active river channel at the time of the survey. River ice with a velocity of about 11,000 fps, effectively masked the arrivals from the surficial materials under the river. The interpreted profile for traverse 81-2 is shown in Figure 4. The calculated bedrock velocity on this profile averages about 16,000 to 18,000 fps but is not well con- strained due to the masking effect of the ice. Bedrock is near surface on the south end of the profile and becomes deeper towards the north to a postulated depth of about 150 feet. There appears to be a bedrock high similar to that noted on profile 81-1, which brings bedrock to within 100 ft of the surface. Surficial layer velocities vary from 5,000 fps on land to possibly 8,000 fps under the river. These velocities probably represent recent water saturated river deposits. 4-3 4.3 Traverse 81-3 This traverse consists of one 500 ft spread and two shot - points. The line crosses the Susitna River approximately 3,000 ft downstream from traverse 81-2 in the area where the river and valley are narrow. The southern traverse terminus is on exposed bedrock and the northern terminus is near the base of steep northern valley slope. The interpreted profile for traverse 81-3 is shown in Figure 5. Ice velocities of 11,100 fps were encountered. The bedrock velocity and depth is unknown. A minimum depth calculation indicates there is probably at least 50 ft of 5,000 fps overburden under the center of the river. The bedrock gradient noted on the upstream profiles (81-1 and 81-2) suggests that the probable depth is more likely to be at least 100 ft. 4.4 Traverse 81-4 This traverse consists of one 1,100 ft spread and three shotpoints. A prominent structural feature on the north abutment, the "Fins", trends toward the location of the line. Rock is exposed near both ends of the line. Virtually the entire length of the line is over the ice - covered river. The interpreted profile for traverse 81-4 is shown in Figure 5. Bedrock appears to be shallow and to have a relatively low velocity of 14,000 fps. This velocity is similar to that measured across the "Fins" on the north abutment (Shannon and Wilson, 1979, and line 81-15, this report). It is also possible that the 14,000 fps material is unusually high velocity frozen gravels and boulders derived from local talus slopes and that competent bedrock may be present at a greater depth. A minimum thickness calculation was made which assumed a higher bedrock velocity (e.g., 17,000 fps). This calculation shows that the depth of such high velocity material would have to be greater than 120 feet. This deeper contact places bedrock at an elevation similar to that both upstream and down- stream from this traverse. It is also possible that the boulder deposit, which is exposed at the surface, has approximately the same seismic velocity as underlying weathered rock. In this case it would not be possible to detect the contact by refraction. A thin wedge of surficial materials with an average velocity of about 6,500 fps may be as thick as 35 ft near the north terminus of the line. A similar wedge appears to be present at the south end. 4.5 Traverse 81-5 This traverse consists of one 650 ft spread and three shotpoints. The line crosses traverse 81-4 and is slightly farther downstream for most of its length. The interpreted profile for traverse 81-5 is shown in Figure 5. The calculated apparent bedrock velocity of 12,000 fps is very low but not inconsistant with the 14,000 fps of velocity on line 81-4. The small difference could be due to anisotropy across a linear fracture zone or to inhomogeneity of the boulder deposit. If present, higher velocity rock (17,000 fps) would probably be over 100 ft deep. Thin surficial materials appear to be as thick as 15 ft at the north terminous of the traverse. 4.6 Traverse 81-6 This traverse consists of one 500 ft spread with two shotpoints. The line crosses a narrow portion of the 4-5 Susitna River under the upstream shell of the proposed dam. Both ends terminate at the rock walls of the Susitna River valley. The traverse connects the two segments of traverse 80-3 (Woodward -Clyde Consultants, 1980). The interpreted profile for traverse 81-6 is shown in Figure 6. The bedrock velocity and depth is unknown from the present data because of the masking of first arrivals from the bedrock refractor by direct arrivals through the river ice. Delayed arrival times at the end --points of the present line suggest there is about 30 to 40 ft of over- burden near the river banks. Minimum depth calculations assuming the higher velocities interpreted for the rock slopes (line 80-3) suggest that the overburden is at least 60 ft thick near the center of the river. This interpreta- tion is similar to that of Dames and Moore (1975) for a line across the river at about the downstream toe of the proposed dam. 4.7 Traverse 81-7 This traverse consists of three spreads, each about 1,000 ft long, and a total of nine shotpoints. The line crosses the river near the downstream limit of Sorrow Area E. The Susitna River divides into several branches with the main course near the north terminus of the traverse. The interpreted profile for traverse 81-7 is shown in Figure 6. Bedrock has a velocity which varies from 19,000 fps at the south terminus to 15,000 fps at the north terminus. Depth to bedrock is typically 100 ft deep. The bedrock surface has a gently undulating interface. The bedrock depth appears to increase near the north terminus of the line and correlates well with previous line SW-14 which is located about 1,000 ft to the northeast of line 81-7. I The surf icial materials, probably saturated recent river deposits, have velocities of about 5,000 fps. There is no evidence in the data for an intermediate velocity layer although previous lines in the area indicate this is possible. A thin, undetectable layer underlying the 5000 fps layer with a velocity of 7,000 to 9,000 fps (typical of glacial materials elsewhere), if present, could cause an over estimation of overburden thickness by about 30 per- cent. 4.8 Traverse 81-8 This traverse consists of three spreads, totaling about 2,500 ft long, and six shotpoints. The line crosses the river valley about 5,000 ft downstream from traverse 81-7. The eastern end of the profile crosses the active river channel. The interpreted profile for traverse 81-8 is shown in Figure 7. Bedrock velocities range from 15,000 fps at the west end of the line to 18,000 fps over most of the line. The depth to bedrock typically varies from 50 to 100 feet. The surficial sediments have velocities of 3,800 fps to 4,800 fps, suggesting only partial saturation. As in traverse 81-7, an intermediate velocity layer, if present as a hidden layer, could decrease the interpreted low velocity overburden thicknesses and increase depth to bedrock by up to 30 percent. 4.9 Traverse 81-9 This traverse consists of two spreads about 1,000 ft. long and six shotpoints. This line crosses the 5usitna River about 2 miles downstream from traverse 81-8. The line 4-7 crosses the river at its northwest terminus. Thin, unsafe ice prevented complete data acquisition. The interpreted profile for traverse 81--9 is shown in Figure 7. Bedrock velocities range from 14,000 fps at the southeast end of the line to 18,000 fps elsewhere. The depth to bedrock varies from 100 to 180 feet. The deepest portion is under the center of the valley. An intermediate layer having a velocity of about 6,500 to 7,500 fps occurs under the entire line. This layer probably represents older and more consolidated gravels possibly of glacial origin. Recent surficial materials, probably alluvial sands and fine gravels, form a thin veneer, 20 to 30 ft thick, with velocities of 3,800 to 4,800 fps. 4.10 Traverse 81-10 This traverse consists of two spreads, each about 1,100 ft long and six shotpoints. The line crosses the valley at a westward bend of the river about 8 miles downstream from the proposed dam. The southern end of the line crosses the river. The interpreted profile for traverse 81--10 is shown in Figure 8. No bedrock velocities were observed on this traverse. Minimum depth calculations show that the depth to bedrock is probably greater than 300 ft based on an assumed velocity of 18,000 fps. Lower assumed bedrock velocities would produce a shallower calculated depth. An intermediate layer velocity of 8,300 fps to 9,500 fps occurs under the entire line. The depth to this layer, which appears to be well consolidated or possibly frozen glacial deposits, decreases from about 70 ft at the north W end of the traverse to 10 ft at the south end. Surf icial materials have velocities of about 4,000 fps. 4.11 Traverse 81-11 This traverse consists of three spreads and nine shot - points. Two spreads are about 1,000 ft long while the third is 700 ft long and offset from the other two. This line is about 6,000 ft downstream from traverse 81-10 and crosses the Susitna River bottom lands. The center section of the line crosses the river. The interpreted profile for traverse 81-11 is shown in Figure 8. Bedrock appears to be about 400 ft deep assuming a bedrock velocity of 18,000 fps. An intermediate layer, similar to that beneath line 81-10, with a velocity of 8,000 to 10,000 fps occurs under the entire line. The highest velocities occur near the south end of the line. The depth to this layer is 20 to 30 feet. Thin surficial materials, which are probably partially saturated sands and gravels, have velocities of 3,000 to 3,500 fps. 4.12 Traverse 81-12 This traverse shotpoints. 81-11. The consists of two 1,000 ft spreads with seven The line is about 4,000 ft downstream of traverse north end of the line crosses the river. The interpreted profile for traverse 81-12 is shown in Figure 9. No bedrock velocities were observed on this traverse. Minimum depth calculations indicate that the depth to bedrock is probably greater than 300 feet, assum- ing a bedrock velocity of 18,000 fps. 4-9 An intermediate layer velocity of 6,700 to 8,000 fps occurs under the entire profile. Velocities increase northwards. Although they are somewhat lower than encountered on lines 81-10 and 81-11, they probably represent similar deposits. Surficial materials 10 to 30 ft thick have velocities which range from 4,500 fps at the south terminus to 3,500 fps at the north terminus. 5.0 SUMMER 1981 SURVEYS Traverses 81-13 through 81-19 were located on the north side of the river, upstream from the proposed Watana Dam. This area is underlain by a buried or "relict" channel. Velocities of channel fill material vary considerably as discussed in relation to the individual traverses below. From borings discussed in the 1980 report (Woodward -Clyde Consultants, 1980), these materials are known to include well consolidated glacial tills and outwash deposits, younger alluvial deposits, and some lacustrine sediments, all possibly frozen in part or entirely. Although the seismic velocities of the channel fill referenced with each traverse are a reflection of material properties, no subsurface boring data was available in the vicinity of the 1981 traverses to identify the type of material that might be represented by a particular velocity range. Traverses 81-20 through 81-22 were run in areas of shallow bedrock on the south abutment at Watana and on the south abutment at Devil Canyon. For these as well as for the other lines, higher velocity bedrock (ie 15,000 to 20,000 fps) is presumably more competent than lower velocity bedrock (ie 10,000 to 14,000 fps). Specific rock types or degrees of weathering, however, cannot generally be distin- guished by velocity alone. Correlation of the seismic velocities reported herein with the most recent surface mapping and boring information may provide a better idea of the extent of particular mapped units and struc- tural features away from their locations known from out- crops or cores. 5.1 Traverse 81-13 Three 1,100 ft geophone spreads overlapped line 80-1 by 500 ft and continued that traverse an additional 2,800 ft to 9 5-2 L the northeast as shown in Figure 1. The traverse crosses undulating topography which rises gently to the northeast. The interpreted profile of traverse 81-13 (Figure 10) shows a continuation of the relict channel with a relatively uniform depth toward the northeast end of the line where it shallows. Bedrock, with seismic velocities ranging from 13,000 to 15,000 fps is from 200 to 250 ft deep beneath most of the traverse. Channel fill material ranges from 6,000 to 8,000 fps and surficial sediments, which are thicker toward the southwest end of the line where it overlaps 80-1, average 2,200 fps. Several irregularities in the time -distance plot (Figure B-1) appear to be due to topographic effects. 5.2 Traverse 81-14 t The southwest end of traverse 81-14 is located about 600 ft from the northeast end of traverse 80-2. Three 1,100 ft lines were used to extend traverse 80-2 to the northeast. The northern end of the line turns north to the edge of a small lake as shown in Figure 1. Relatively smooth topo- graphy rises gently to the northeast to within 1,000 ft of the small lake, then drops gently toward the lake. The topography along the northern 1,000 ft was not surveyed; the profile shown in Figure 11 for that area was approxi- mated from small scale maps and field notes. The interpretation of traverse 81-14 (Figure 11) shows 18,000 fps bedrock to be 500 ft deep beneath the southwest end of the line. This requires a drop of about 200 ft from the northeast end of line 80-2 which is not inconsistent with the 1980 interpretation. The 500 ft depth places the thalweg of the channel at an elevation of about 1,700 ft, which is similar to that found on line 80-1 to the west and somewhat deeper than on lines to the southeast. This 5-3 deepening to the northwest is consistent with the interpre- tation from other considerations that the ancient stream flow was in that direction. To the northeast, on traverse 81-14, bedrock shallows to a depth of 100 ft, effectively the edge of the relict channel, about 1,000 ft south of the lake. Along the northern extension towards the lake, bedrock maintains a depth of between 100 and 150 ft, and an average velocity of 15,000 fps. Two layers of channel fill are apparent on the profile. Material with a velocity ranging from 9,000 to 10,500 fps as thick as 400 ft occupies the bottom of the relict channel and is overlain by a 50 to 150 ft thick 6,000 fps layer that continues to the north beyond the limits of the relict channel. The velocity of the deeper layer is similar to that interpreted as possible permafrost else- where in the area. If it is indeed frozen, then it may be underlain by less dense, unfrozen sediments and the depth to bedrock may be as much as 100 ft shallower than shown in Figure 11. This is assuming that only the upper 100 ft is frozen and that the velocity of the underlying material is about 7000 fps. Velocities of surficial deposits range from 1,200 to 1,800 fps beneath traverse 81-14 and vary from 20 to 30 ft in thickness. 5.3 Traverse 81-15 The center portion of traverse 81-15 consisted of two 550 ft geophone spreads across the apparent topographic expression of the Fins structure near the top of the valley wall on the north side of the river. Topography across this central portion is somewhat irregular due, presumably, 5-4 to the underlying structure. Slopes to either side of this central portion were too steep for continuation of the line. Therefore, two extensions were run off the east and west ends of the central traverse but shifted about 200 ft further upslope to an area of more subdued topography (Figure 1). Data from traverse 81--15 indicates no intermediate layer (7,000 fps) such as found on nearby line SW-3. Instead, the most reasonable interpretation (Figure 12) of the data shows relatively low velocity bedrock (11,000 to 12,700 fps) underlying relatively thin surficial materials with velocities of 1,000 to possibly as much as 4,000 fps. A bedrock velocity change at the southwest end of the extension to 16,000 fps may indicate the downstream boun- dary of the shear zone. All apparently anomalous arrival times (Figure $-3) can be explained by topographic effects or by slight thickness changes in surficial materials. Two possible locations of resistant ridges in bedrock within the zone are beneath the northeast end of the extension where arrivals are consider- ably more irregular than elsewhere. No such irregularities occur along the central portion of the line. 5.4 Traverse 81-16 This traverse consisted of two 1,100 ft geophone spreads across a deep section of the relict channel adjacent to the Susitna River slopes upstream from the proposed dam site. Topography in this area is gently rolling and fairly level. The east end of traverse 81-16 is within 100 ft of the south end of traverse 80-7. The interpretive profile of traverse 81-16 (Figure 12) shows the depth to bedrock to vary between 200 ft at the 5-5 west end and 450 ft at the east end of the line. Bedrock velocity is 18,000 to 19,000 fps. Channel fill ranges from 5,500 to 10,000 fps and thin surficial materials, 1,300 to 1,800 fps. The 5500 fps materials appears to be a younger filled channel. The shape of this channel, however, is not well defined. Bedrock elevation near the east end of the line is about 1,775 feet. This appears to be about the deepest part of the channel in the area. The elevation agrees with that noted on SW-3 to the north. 5.5 Traverse 81-17 A single 1,100 ft geophone spread was run northerly from the east end of traverse 81-16. The line is about 300 ft east and parallel with traverse 80-7. The configuration and velocities shown on the interpretive profile (figure 13) agree with those interpreted for traverse 80-7. Bedrock with a probable maximum velocity of 20,000 fps shallows from 400 ft at the south end, near the east end of line 81-16, to about 200 ft at the north end. Channel fill material averages about 8,000 fps and surficial materials about 1,800 fps. 5.6 Traverse 81-18 This traverse consisted of a single 1,100 ft line which was run in conjunction with line 81-19 across the southern edge of Borrow Area D north of Quarry Source B. A prominent gully separated the two lines and precluded their being run as a single traverse. The topography along traverse 81--18 is relatively flat, sloping gently to the east. The profile of line 81-18 shown in Figure 13, indicates 20,000 fps bedrock at a fairly uniform depth of 325 feet. 5-6 Bedrock depth at the eastern end of the line is based on depths interpreted for line 81-19. Intermediate velocity material is predominently 6,500 fps with a wedge of 8,000 fps material, below the eastern end of the line which is consistent with traverse 81-19. Surficial materials ranging from 1,200 to 2,000 fps thin toward the east from a maximum thickness of 60 ft near the west end. 5.7 Traverse 81-19 This traverse consisted of two 1,100 ft geophone spreads extending easterly from about 600 ft east of traverse 81-18. The traverse crosses line 80-8 near the midpoint. The line was approximately parallel to contours sloping gently toward the west. The slope is very steep toward the south. The interpretive profile of line 81-19 (Figure 14) shows an irregular bedrock surface ranging from 300 to 450 ft deep. The deepest portion is near elevation 1700 which is the lowest noted during this survey. Bedrock velocity ranges from 13,000 to 16,000 fps. Two layers of intermediate velocity materials are apparent. They consist of a 6,000 fps layer 80 to 150 ft thick overlying a 7,500 to 8,000 fps layer. Although thicknesses vary somewhat, this is consistent with the interpretation for line 80-8 where the lines cross. Surficial deposits are up to 40 ft thick with velocities from 1,200 to 2,500 fps. 5.8 Traverse 81-20 This traverse extends line SW-1 on the south abutment of the proposed Watana Dam. Total extension was about 1000 ft to the east. The traverse consisted of overlapping 550 and 300 ft geophone spreads with two 225 ft spreads over the 5-7 east side of the traverse to produce more detailed data in that area. Gently rolling topography along the traverse rises slightly toward the east. Figure 15 shows that bedrock, interpreted to be about 18,000 fps, underlies the entire traverse at shallow depth, generally less than 10 ft. A small wedge, up to 50 ft thick, of intermediate velocity material, averaging 7,000 fps overlies bedrock near the east end of the line. This material was identified as varved silts and clays in boring DH-25 (U.S. Army Corps of Engineers, 1979). 5.9 Traverse 81-21 Four overlapping 550 ft geophone spreads and several 225 ft detail spreads were run across the suspected projection of the Fingerbuster structural feature on the south abutment of the proposed Watana Dam. The total length of the line was about 1900 ft. It crosses line 81-20 near its northeastern end. The topography rises steeply to the southwest along the traverse. The purpose of traverse 81-21 was to delineate, if possi- ble, the Fingerbuster zone in order to locate a drill site for further exploration of the zone. As shown on the interpretive profile of the traverse (Figure 15), the structural zone appears to occur as an area of 12,000 fps bedrock flanked by more competent 18,000 fps bedrock. This is overlain by 1,500 to 3,500 fps surficial materials which range in thickness from zero to 40 feet. The location of the zone was thought to be known more precisely from apparent anomalies on field time distance plots. Several anomalies apparent on the time -distance plot (Figure B-6), can be attributed for the most part to topographic irregularities and to changes in thickness of M:3 the near surface layer. The zone appears to be delineated by a prominent slope break to the west and a rapid thinning of surficial deposits to the east. It appears that a topographic low exists over the central portion of the zone. The depression appears to be due to erosion by a crossing stream. 5.10 Traverse 81-22 This traverse was run as three overlapping 550 ft geophone spreads along the ridge on the south abutment of the proposed Devil Canyon Dam. The eastern portion of the traverse crosses the southern ends of lines 80-12 and 80-13. The somewhat irregular ground surface along the traverse slopes downward toward the east end. The interpretive profile of traverse 81-22, shown in Figure 16, shows very shallow bedrock ranging from 11,000 to 15,000 fps overlain by surficial materials of 1,800 to 2,000 fps. The surficial material appears to average about 10 ft thick but thickens to as much as 30 ft at one location near the east end. Intermediate layers of 5,000 and 10,000 fps interpreted for the south ends of 80-12 and 80-13 were not apparent from the data for 81-22. El 6.0 FALL TRAVERSES -FOG LAKES AREA The Fog Lakes traverse consisted of 4e-500 ft geophone spreads with common end shot points. The location of the traverse was selected to cross areas of possible buried channels which could contribute to seepage from the reservoir. Topography along the line is gently rolling and relatively flat locally. Elevations range from less than 2,300 ft across the Fog Lakes valley, approximately five miles east of the proposed Watana Dam, to about 2,400 ft near the proposed south abutment. The interpretation of the data for the traverse, shown in Figures 17 through 23, indicates that apparent bedrock velocities vary substantially along the traverse, from 20,000 fps to as low as 10,000 fps. Two types of intermediate material are apparent. The first ranges from 4,500 to 7,000 fps and is interpreted to consist of poorly consolidated, saturated glacial deposits. The second ranges from $,000 fps to as much as 10,500 fps. This is suspected to be well consolidated glacial sediments in part or entirely frozen. Surficial deposits range from 1,000 to 3,000 fps, are as thick as 50 ft in some areas, and are absent in others. Several areas along the traverse appear to be underlain by buried channels which extend below the proposed reservoir level. The two most prominent of these are near the west end of the traverse (Figure 17) and beneath the Fog Lakes Valley (Figures 22 and 23). Near the west end, a channel which may be as deep as 300 ft (to elevation 2,030) is filled mainly with low velocity (4300 to 6000 fps) de- posits. Higher velocity channel fill (9000 fps) is indi- cated near the east side of the channel but the contact 6--2 between the two types of channel fill is uncertain. It is possible that the higher velocity material is permafrost, in which case unfrozen sediments (with lower velocities) could be present below it and the total depth of the channel could be somewhat less than shown on the profile. The width of the deepest part of the channel appears to be about 1,000 feet. The apparent channel in the Fog Lakes Valley is more than a mile wide. The deepest part appears to underlie the lowest part of the valley at an elevation of about 1,940, 350 ft below ground surface. Much of the rest of the channel, which extends below the topographic high northwest of the valley, is below an elevation of 2,100 feet. The shape of the channel shown on the profile is based on marginal arrival -time data from distant offsets and from minimum depth calculations where distant offsets did not penetrate sufficiently to detect rock. The shape, therefore, could be significantly different, especially on the west side where depths could be greater. The interpretation shown, however, is considered to be a reasonable estimate of the maximum depth within the limits of the uncertainties of the data. The most critical uncertainty is the nature of the 8,000 to 11,000 fps apparent channel fill material. If this material is interpreted to be well consolidated, glacial deposits then the interpreted profile as shown in Figures 22 and 23 is appropriate. However, if the material is frozen, then lower velocity material could underlie the perma- frost and depths to bedrock could be shallower than shown on the Figures. 6--3 A third possibility, which is not likely, is that the apparent channel fill could instead be weathered bedrock, at least in part. If this were true the bedrock velocity would be so close to that expected for frozen or well consolidated sediments that the contact between them could not be distinguished. It is remotely possible that the apparent indications of high velocity bedrock at depth are the result of irregularities in shallower, very low velocity weathered rock or from steeply dipping contacts between weathered bedrock and high velocity channel fill. An attempt was made to resolve the nature of high velocity apparent channel fill material using shallow reflection at the location of refraction line 81-FL-3. Results were not definitive but the most likely reflection appears to place the bedrock contact at a depth of 170 ft below ground surface which is similar to the depth indicated by refraction in that area. This depth, however, indicates an anomalous high near the middle of the broad channel which makes the interpretation even more tenuous. Other areas of apparent channeling are present along the central portion of the traverse. These channels, although broad in some cases, are all above elevation 2,150 and generally shallower than elevation 2,200. At several locations along the Fog Lakes Traverse, bedrock lows appear to coincide with higher seismic velocities which is contrary to conditions elsewhere in the vicinity. No explanation for this is evident from the present data. 7.0 MAGNETOMETER SURVEYS Approximately 3,000 ft of magnetometer surveys were run as two long traverses and three shorter traverses in an attempt to locate buried mafic dikes on the south abutment of the proposed Devil Canyon Dam. One of the long tra- verses was run along the alignment of refraction line 51-22. No significant anomalies were detected which could not be attributed to cultural features or to topography. The method was found to be not applicable for mapping the dikes and therefore the program was discontinued after these trials. 8.0 GENERAL OBSERVATIONS AND CONCLUSIONS In general, results of the 1981 seismic refraction surveys are in good agreement with surveys interpreted during 1980 and in previous years. Only a few cases were found where independent interpretations did not agree. The most notable of these were the lack of intermediate velocity material indicated on lines 81-15 and 81-22 which crossed or were near to existing lines for which shallow, interme- diate velocity material had been interpreted. This difference may be a simple result of differing interpreta- tion procedures or possibly an indication of rapid lateral changes. Boreholes, or possible additional, more detailed seismic lines, are needed to resolve these differences. As previously discussed, the seismic refraction method is subject to a number of limitations which affect the confidence one can place on the details of interpretations based soley on refraction data. For example, a great deal of uncertainty exists as to the nature of the apparent channel -fill material along the Fog Lakes traverse. A few borings in the interpreted channel areas, however, should resolve these uncertainties and provide a basis for further evaluation of possible seepage problems during design studies. The interpretation of material types represented by various velocities have been discussed in previous reports and are covered only in general terms herein. The present profiles were developed assuming the material types and velocities encountered in this survey were similar to those encoun- tered in previous surveys which were based, in part, on boring information. REFERENCES Dames and Moore, 1975, Subsurface exploration, proposed Watana Dam site on the Susitna River, Alaska: Report for Department of the Army, Alaska District, Corps of Engineers, Contract DACW85-C-0004, 12 p. Redpath, B. B., 1973, Seismic refraction exploration for engineering site investigations: U.S. Army Engineer Waterways Experiment Station, Explosive Excavation Research Laboratory, Livermore, California, Technical Report E-73-4, 55 p. Shannon and Wilson, Inc., 1978, Seismic refraction survey, Susitna Hydroelectric Project, Watana Dam Site. Report for Department of the Army, Alaska District, Corps of Engineers, Contract DACW85-78-C-0027, 17 p. U.S. Army Corps of Engineers - Alaska District, 1979, Southcentral Railbelt Area, Alaska Upper Susitna River Basin - Supplemental Feasibility Report: Appendix Part I. Woodward -Clyde Consultants, 1980, Final Report, Susitna Hydroelectric Project Seismic Refraction Survey, Summer, 1980: Report for R & M Consultants, 22 p. TABLE 1 1980-1981 Seismic Refraction Line Data Line WCC R & M Location Profile Time -Distance Length Number of Line No. Survey No. Figure Figure Plot Figure (ft) Segments/Shots 80-1 80-1 2 * * 6,600 8/31 80-2 80-2 2 * * 5,500 5/19 80-3 80-3 2 * * 2,000 4/11 80-6 80--6 2 * * 1,100 2/5 80-7 80--7 2 * * 2,200 2/10 80-8 80-8 2 * * 2,200 2/10 80-9 80-9 1 * * 1,100 1/3 80-10 80-11 80-11 2 * * 2,200 4/13 80-12 80-12 3 * * 1,120 3/8 80-13 80-13 3 * * 1,120 3/8 80-14_-- 80-15 80-15 3 * * 440 1/2 81-1 81-1 2 4 A--1 1,000 1/3 81-2 81-2 2 4 A-1 2,000 2/6 81-3 81-3 2 5 A-1 500 1/2 81-4 81-4 2 5 A--1 900 1/3 * Profiles and time --distance plots included in previous report (Woodward -Clyde Consultants, 1980). Comments Watana Rt Abutment -Relict Channel ---Extended NE by 81-13 Watana Rt Abutment -Relict Channel --Extended NE by 81-14 Watana Rt & Lft Abutments Upstream--81-6 Crosses River in Middle Not Used Not Used Watana RT Abutment --Relict Channel Area Watana RT Abutment --Relict Channel Area Watana Quarry Source B--Extends SW-5 to South Watana Borrow Area E--Extends SW-14 to NW Not Used Watana Borrow Area E--Adjacent to Tsusena Creek Devil Canyon Saddle Dam Area --Left Abutment Devil Canyon Saddle Dam Area --Left Abutment Not Used Devil Canyon Saddle Dam Area ---Left Abutment Run Over River Ice, 2.1 Miles Upstream from Proposed Watana Dam Centerline. Run Over River Ice, 1.6 Miles Upstream from Proposed Watana Dam Centerline. Run Over River Ice, 1.1 Miles Upstream from Proposed Watana Dam Centerline. Run Over River Ice, 0.6 Miles Upstream from Proposed Watana Dam Centerline. TABLE 1 (Continued) WCC R & M Location Profile Time -Distance Line Length Number of Line No. Survey No. Figure Figure Plot Figure (ft) Se meats/Shots Comments 81-5 81-5 2 5 A-1 450 1/3 Run Over River Ice, 0.5 Miles Upstream from Proposed Watana Dam Centerline. 81-6 81-6 2 6 A-1 450 1/2 Run Over River Ice, 0.1 Miles Upstream from 81-7 81-7 Proposed Watana Dam Centerline. 1 6 A-2 3,200 3/9 Run Over River Ice, 4.0 Miles Downstream from Proposed Watana Dam Centerline. 81-8 81-8 1 7 A-2 2,500 3/6 Run Over River Ice, 5.2 Miles Downstream from Proposed Watana Dam Centerline. 81-9 81-9 1 7 A-2 2,000 2/6 Run Over River Ice, 7.3 Miles Downstream from Proposed Watana Dam Centerline. 81-10 81-10 1 8 A-3 2,100 2/6 Run Over River Ice, 8.2 Miles Downstream from 81--11 81-11 Proposed Watana Dam Centerline. 1 8 A-3 2,800 3/9 Run Over River Ice, 9.3 Miles Downstream from Proposed Watana Dam Centerline. 81-12 81-12 1 9 A-3 2 000 2/7 Run Over River Ice, 10.1 Miles Downstream from Proposed Watana Dam Centerline. 81-13 80-1X 2 10 B-1 3,200 3/10 Watana Relict Channel Area --Extends 80-1 to NE 81-14 80-2X 2 11 B-2 3,300 3/5 Watana Relict Channel Area --Extends 80-2 to NE -- North Extension Not Surveyed 81-15 & 15X BH-11 2 12 B-3 2,100 4/11 Watana Rt Abutment --Fins Area 81-16 16-81 2 12 B-3 2,200 2/8 Watana Relict Channel Area 81-17 --" 2 13 B-4 1,100 1/5 Watana Relict Channel Area --Not Surveyed 81-18 QSB 2 13 B-4 2,200 2/10 Watana Relict Channel Area--N of Quarry Source B 81-19 QSB 2 14 B-5 1,100 1/6 Watana Relict Channel Area--N of Quarry Source B 81-20 SW-1X 2 15 B-6 1,600 5/11 Watana Left Abutment --Extends SW-1 East 81-21 BH-12 2 15 B-6 1,850 5/19 Watana Left Abutment --Crosses 81-20 81-22 17 3 16 B-6 1,500 3/6 Devil Canyon Left Abutment --Crosses 80-12 and 80-13 $1-FL-1 to Fog Lakes 1 & 2 17 - 23 Cl - C7 28,800 48 138 / Watana Fog Lakes Area ---Continuous Profile 81-FL-48 33 34 35 36 37 38 39 40 41 4 3a FOG LAKES TRAVERSE 2 4 3 44 4Jr 3p 27 28 29 46 47 48 m r W N W n W E' W pn W ao W m W a W N W o W � N 3.224.000 N 3226,000 _1�3�2_B 000 I N 3,230,000 I N 3.232,300 _N 3,234 9000� �N 3,236 000 N 3 80 00 N340 -N- 1000 2000 FEET siiiiiia NOT SHOWN PREPARED BY WOODWARD-CLYDE CONSULTANTS 0 2 3 SCALE IN MILES Fog Lakes Refraction Traverse Lines 81---FL-1 to 81—FL-48 11 6 yr{ 5 23 1 12 r FLOW i •C r- — — _ — .tom 33 34 41 42 ' I ti 28 2g 48 rc z Q4qW q C) DM-B t WATANA DETAIL AREA IFigure 1 } LTZMMM11MA1I. 5L-81-10 FOG , `-\�RE ca SW-12 ,�j �- SL-81-11 Devil Canyon 16 Miles SL-81 _12 WATANA VICINITY MAP — APPROXIMATE LOCATION OF REFRACTION LINES OUTSIDE DETAIL AREA RR FIGURE 2 PREPARED UY WOODWARD — CLYDE CONSULTANTS 0 200 400 600 SCALE IN FEET SW-15 1450 1400 13b4 800 SUSITNA RIVER r LOCATION OF DEVIL CANYON SEISMIC REFRACTION LINES cn r 4 0 0 m SL-81-22 FIGURE 3 Him PREPARED BY WOODWARD — CLYDE CONSULTANTS South —P 1600--, 81-2 1500 4- e 8000 5000 / m7000 1400 � O � ~ �0— 16000 - 18000 1300 C 0 S35E —� 1600 1500 1400 1300 1600 1500 1400 1300 SEISMIC REFRACTION PROFILES 81-1 AND 81-2 1600 1500 1400 1300 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet FIGURE < 'RCRIS ooronnrn nv wnnnwwon — ri �nr rn..���� r...T.. South o 1500 a 1450 tlJ LU 1400 1354 S5E —� 1540 — � r a 1450 6500 0 a� w 1400 81-3 1350 1500 1450 1400 1350 S75E I 1450 03 03 v- C O t� f6 7 tlJ LU 1400 1350 81-4 1500 Crosses 81-5 10 14000 Minimum Depth _� � � 7 � — (D Assumed 17000 SEISMIC REFRACTION PROFILES 81-3, 81-4 AND 81-5 Assumed 6000 ~ � G 1454 1400 1350 81-5 15( 14E 14( 19 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 54 feet FIGURE , IRCBa D BY WOODWARD-CLYDE CONSULTANTS South —� 1450 HWA 1450 5000 C) 1300 0 15000 19000 a a� w 1150 1150 1000 — 1500 m 1450 m rZ 0 W 1400 1350 PREPARED BY WOODWARD-CLYDE CONSULTANTS 81 —5 r- 1500 Assumed 6000 1450 (D +r7'OJ Assumed 18000 Minimum 1400Depth Horizontal Scale: 1 inch = 100 feet Vertical Scale: 1 inch = 50 feet 1350 SEISMIC REFRACTION PROFILES 81-6 AND 81-7 Horizontal Scale: 1 inch = 300 feet Vertical Scale: 1 inch = 150 feet 1000 Compressional wave velocities in feet per second FIGURE s RCNf3 East 0. 1500 1400 m c 0 "' 1300 1200 S55E 0- 1500 �. 1400 a� a� 0 w 1300 WITY am 4800 � O 15000 1500 1400 3800 O� 1300 18000 1500 1400 3000 _ O 3500 —o- 6500 7 500 1300 0 — — — --0-- , ! ! ! 14000 1 ! 18000 1 —o� 1200 SEISMIC REFRACTION PROFILES 81-8 AND 81-9 1200 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet FIGURE 7 lAcwis� S23E 1400 1300 8300 a Mxlffl 1100 S17W 1500 1400 1:�nn C O 7 LU 1100 1200 1000 PREPARED BY WOODWARD - CLYDE CONSULTANTS 09 19 81-10 1400 4000 —1300 Greater than 300 feet deep assuming 18000 bedrock SEISMIC REFRACTION PROFILES 8I-10 AND 8I-I1 9500 Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 teet 1500 1200 1100 1400 Compressional wave velocities in feet per second 1300 1200 1100 1000 .�GUAE a ��A[si South o 1400 81-12 1400 O, 3500 —�_ — _——��p--O—� 4500 7 1300 �_ _op_-----_._._.... — 0__�--- 1300 Im 6700 8000 0 4- m w 1200 A k 1200 Greater than 300 feet deep assuming 18000 bedrock 1100 SEISMIC REFRACTION PROFILE 81-12 1100 Compressional wave velocities in feet per second Horizontal Scale: 1 inch = 200 feet Vertical Scale: 1 inch = 100 feet FIGURE , IRCflfS PREPARED BY WOODWARD-CLYDE CONSULTANTS 2200 Overlaps 8Q-1C i N35F — 1 2200 81--13-0 2006 4 1 2500 2100 2000 �.. 1 �\ 21 QQ 6000 ui LL / Z 0 H 2O00 uw 8000 z Q .... ........ J 2000 ui7000 ~ Dotted lines from a 1980 interpretation 1900 r v 1900 • 13000 1800 13000 1800 2300 r N35E — 2300 w Z_ J Y v 2500 22Q0 Q O r 2200 w ,L / Lu w 0 2000 / L` z _0 > 2100 6000 ~ J 2100 j LU i w / J ' W 2000 � e � J 2000 � e 8000 15000 1900 1900 SEISMIC REFRACTION PROFILE LINE 81-13 (80-IX) Compressional velocities in feet per second 0 100 200 HORIZONTAL SCALE IN FEET PREPARED BY WOODWARD - CLYDE CONSULTANTS FIGURE 10 2300 2200 2100 h w w U_ z 0 2000 h a w J LU 1900 - 1700 1200 7,900 LU uL 2200 0 h ` 6000 � > w LU z J UJ J 0 2100 Q 15700 ~ SEISMIC REFRACTION PROFILE LINE 81-1 (80-2X) PREPARED BY WOODWARD - CLYDE CONSULTANTS 2300 2200 2100 LU LL z 0 h Q w J 1900 Compressional velocities in feet per second 2200 0 100 200 HORIZONTAL SCALE IN FEET 2100 FIGURE II ����� N80E 2200 2100 w w LL z 0 2000 a w J w 1900 1800 N 50E — 2200 81-15X(SW) 81-15 81-15X(NE) 1500 v 1000 1100 16000 ? ? e W 2100 f L"' `-? 1150Q 4Q00?o �? O , N1300 � cN ? 12000? f a Q D Lu a 1 11000 a w 2000 yI 12700 'Io - 0 1900 PREPARED BY WOODWARD — CLYDE CONSULTANTS SEISMIC REFRACTION PROFILE LINES 81-15, 15X AND 81-16 2200 2200 2100 I- w w LL Z 0 2000 Q w J w 1900 1800 � Compressional velocities in feet per second w w LL 2100 o Q 100 200 j HORIZONTAL SCALE w IN FEET w N 1900 FIGURE 12 2A00 Nf1RTH - R1-17 2300 2200 w w LL Z 0 Q 2100 w J ui 2000 1900 :11 2A00 2200 N71F - 2300 2100 2200 2000 2100 1900 2000 1800 1900 1700 1800 1600 SEISMIC REFRACTION PROFILE LINES 81-17 AND 81-18 F:yms a 2200 2100 H w lL LL Z Q 1900 Q Lu J w 1800 1700 1600 0 100 200 --E HORIZONTAL SCALE IN FEET Compressional velocities in feet per second FIGURE 13 ����� 2300 2200 2100 6 1900 1800 1700 m N7RF SEISMIC REFRACTION PROFILE LINE 81 19 (QS®) 2300 2200 r -1 2000 1900 1800 1700 velocites in feet per second 100 200 177-71 HORIZONTAL SCALE IN FEET PRFPARE11 Rv wnnnwaan_ a vnc cMd@ni --ITC FIGURE 14 EAST 2100 81 20 2100 Crosses LINE 81-23 Lu Crosses w w LL LINE 81-21 Ui 0 2000 Q o r 2000 > ? > _ ? 7000 w J ® LU LU J d ` ��1 W 1900 18000 18000 1900 N45E 2200 81-21 2200 2300 — 2100 1 ` `1500 Stream Channel 2100 w 18000 LLL U 7 ? 1 W z , ? _3000 L 0 _ Q 2000 0 > ` ` 2000 a w 12000 / Crosses > LINE 81-20 ui w ? / 18000 3500 Compressional velocities in feet per second 1900 / 1900 0 100 200 HORIZONTAL SCALE IN FEET 1800 1800 SEISMIC REFRACTION PROFILES LINES 81-20 (SW -IX) AND 81-21 (BH-12) PREPARED BY WOOD WARD--CLYDE CONSULTANTS FIGURE 15 Crosses Line SW-17 EAST 8122 1500 2000 Crosses Crosses 1500 _ Line j80-12 Line J80-13 IN. w F- 1400 15000 ` 2000 1400 uj LL O O ii j w 11000 J 1300 ` i 1300 1200 1200 Compressional velocities in feet per second 0 100 200 B-� HORIZONTAL SCALE IN FEET FOG LAKES SEISMIC REFRACTION PROFILES LINE 81-22 (R&M 81-17) FIGURE 16 PREPARED -BY WOOOWARO- CLYDE CONS141 TANTS 81--F L48 81—F L--47 81— F L-46 81— F L-45 2400 w 2300 w D_ z a Q w J w 2200 2100 81—F L-44 81—FL---43 S77E (906� 1100 1200 1200 P "e 1600 2300 2300 —?� 4200 5000 2200 Q 9000 LU , Z = e U 2100 s O 2000 2200LU w 18000 LL LU z z 0 � Q ULU 2100 Lu 1 2000 FOG LAKES SEISMIC REFRACTION PROFILES SHEET I OF 7 2400 2300 Uj w LL z 2200 O a LU J LU 2100 2000 Compressional wave velocities in feet per second Numbers in parentheses above topographic profile refer to survey points 0 100 200 HORIZONTAL SCALE IN FEET PREPARED BY WOODWARD -CLYDE CONSULTANTS FIGURE 17 2400 81-F L-42 577E I 81-F L--41 r- S88E — 81-F L--40 (907) (908) Lu 2300 180� I 2200 1800 z 2000 4000 00, 6000 6000 Lu \ w 2200 m \ \ 12500 O Lu 12500 f 12800 -' `��•� \ z \ a 2100 81—FL-38 341_G1 _'47 -. __ 2400 ~w 2300 w LL z O a w w 2200 2100 rUb L.AKtS SLISMIG REFRACTION PROFILES SHEET 2 OF 7 PREPARED BY WOODWARD -CLYDE CONSULTANTS 81F L39 lSUU ® ® 5200 I 7000 / / S 14000 2400 2300 w LL z O H a w 2200 w 2100 2400 'N2300 w w LL z _O V ~ a w 7 z w 2200 w V a 2100 Compressional wave velocities in feet per second Numbers in parentheses above topographic profile refer to survey points 0 100 200 HORIZONTAL SCALE IN FEET FIGURE 18 iRCN6l 81--F L35 2500 l_- 2400 LU LU LL z 0 a 2300 LD 2200 81—F L34 a M C7 0 0 cs 81—F L---33 81 F l —19 2500 2400 w w LL z 0 H a w 2300 w 2200 81—F L31 81—F L-30 81—F L-29 N67E Compressional wave velocities in feet per second (917) (913) 2400 2500 3200 3000 28p0 000 �°' 2800 2400 Numbers in parentheses above topographic �•� --� — ® 1 --- — ,-.- �. .� ...� �� �•® �" �--® profile refer to survey points 5000 w 5800 7000 LU 0 100 200 LU 1 15500 LU LL LL z LU ® LL z HORIZONTAL SCALE p 2300 z 12500 Z 2300 IN FEET / j 15400 w - = U z U LU -i LU Q a LU 2200 2200 FOG LAKES SEISMIC REFRACTION PROFILES SHEET 3 OF 7 PREPARED BY WOODWARD—CLYDE CONSULTANTS FIGURE 19 81-F L-28 81-F L-27 S80E (918) �-W 2600 0 — — — — — 1600 1500 2100 1800 3200 LU LU 13,500 ULL z w 15,000 2300 z ~ J Q W J U I— W Q 2200 14, 000 81- F L-26 81-F L-25 f919) 2400 1500 2100 W w u- z 12,500 2300 2 W Q > Z W J J W U F- Q 2200 81-F L-24 81-F L-23 81-F L-22 �— N83E 2400 S80E 2400 (920) 2300 3800 �`-- --- -`- — s. 5500 3100 • �, 3800 Compressional wave velocities in feet per second 11,000 �` +� �•® O Numbers in parentheses above totographic w 2300 \ 6500 2300 w profile refer to survey points u_ 10,000 ®•® ® W 0 100 200 z O Z = z _ ___ ~ ®� O � W HORIZONTAL SCALE j = 14,600 J Q IN FEET W J W 2200 U Q 2200 > W w Q 2100 FOG LAKES SEISMIC REFRACTION PROFILES SHEET 4 OF 7 2100 -RFPA RFh RV wnor) wbwr) —rl VrIF rnme- -- FIGURE 20 81-F L-21 81- F L-20 2400 N 83 E — (921) (922) 2000 5000 4500 1-11" 5000 w 2300 O 8000 ® z \ 9000 O 13,500 �•� "� Q w 2200 w z :1 15,000 2 U H Q 2100 81-FL-19 I 81-FL-18 r 2100 2200 — ® 8000 18,000 (923)-� 2400 1800 2400 9700 2300 w w z �? ® O � � H Lu 2200 w w z_ J Y U H a 2100 81-FL-17 81-FL-16 81-FL-15 N83E— (924) 2400 2400 00 d 1 ---3000 2600 5000 5000 5500 �� 100 ® Compressional wave velocities in feet per second 4500 � \ 6500 Numbers in parentheses above topographic ® profile refer to survey points 2300 15,000 \ 2300 Lu Lu w 7 / 20,000 LL 0 100 200 w � � z z O 0 HORIZONTAL SCALE Q IN FEET a _ � 2200 z 2200 w w w w z_ x J U ~ = Q � U � a 2100 2100 FOG LAKES SEISMIC REFRACTION PROFILES SHEET 5 OF 7 FIGURE 21 ����� 81-FL-14 81-FL-13 81-FL-12 81-FL-1 N 83 E —• S63 E 2400 w 2300 W LL z 0 H a W w 22nn 2100 2400 2400 2300 W W LL z 0 2200 > W J W 2100 2000 5000 a—. (927) $1-FL-4 6800 .�•000 ~ --~ ~ •� ? 3500 ~ 4500 �•— 4800 " {928) 2300 9500 "50 .� 3000 �•� 2300 10,000 9500 w V 7000 Compressional wave velocities in feet per second LL o W z 8700 8000 Numbers in parentheses above topographic ~ 2200 W z w profile refer to survey points a = 2200 W W �O~ 1 0 LL z 0 100 200 20,000? O Q 0 Apparent Reflector Q HORIZONTAL SCALE ' 7 W IN FEET 2100 2100 w 2000 Izo,000} 18000 2000 FOG LAKES SEISMIC REFRACTION PROFILES SHEET 6 OF 7 FIGURE 22 2300 2200 h W W W z O 2100 a W J W 2000 1900 81-F L-5 81-F L-6 81-F L-7 81-F L-8 81-FL-9 81-FL-10 81-FL-11 S48E 2300 2500 "� 2000 1uuu Uj Luu 10,500 W z W O z j 2200 U W Q J W 2 ® 7 r � r 10,11 2100 3800 3000 1800 180� 2�100 2300 8000 w _ - 8000 W 9000 LL 17,000 �' ® z O F- W 2200 7 20,000 z W i J W W 0 d z W LU 2100 FOG LAKES SEISMIC REFRACTION PROFILES SHEET 7 OF 7 2300 2200 w W W z O h a 2100LU W 2000 Compressional wave velocities in feet per second Numbers in parentheses above topographic profile refer to survey points 0 100 200 HORIZONTAL SCALE PREPARED BY WOODWARD-CLYDE CONSULTANTS FIGURE 23 APPENDIX A* TIME -DISTANCE PLOTS - SPRING SURVEYS * This appendix deleted from Task 5, Appendix I. Refer to project files for Woodward -Clyde Consultants report. APPENDIX B* TIME -DISTANCE PLOTS - SUMMER SURVEYS * This appendix deleted from Task 5, Appendix I. Refer to project files for Woodward -Clyde Consultants report. APPENDIX C* TIME --DISTANCE PLOTS - FALL SURVEYS (FOG LAKE) * This appendix deleted from Task 5, Appendix I. Refer to project files for Woodward -Clyde Consultants report. APPENDIX J AIR PHOTO INTERPRETATION HYDROELECTRICSUSITIMA ■: ACRES" REM G®NS.uLTANTS, INC. EN�'INEER5—LOGISTS PLANNERS SURVEvoRS INTRoguCTION The feasibility study for the Susitna Hydroelectric Pmject includes geological and geatechnicol investigation of the area extending from the Parks Highway IIB mills east to the mouth of the Typna River and from the Denali Highway 50 miles south to Stephan Lake. The ,mat cost effeell" method of generating and compiling baseline geologic Informatiom about this large, little -investigated region is through the methods of photoinlerpratatlon and terrain unit map- ping. This text and the accompanying terrain unit maps present the results of aerial photograph interpretation and terrain unit analysis for the eras including the proposed Watana and Devil Canyon damsite areas, the Susitna River reservoir areas, wnslruction material borrow area., and access and transmission line corridors. The task was performed far the Alaska power Authority by R&M Consultants, Inc., working under the direction of Acres American, I nc. Scope of Work and methods of Analysis Work on the air photo interpretation subtask con sisted of Several activities culminating In a set of Terraln UnitMaps delineating surface materials and geologic features and conditions in the project area. The general objective of the exercise as to document geological features and gootechnical conditions that would significantly affect the design and construction of the project features. More specifically the task objectives included the delineation of terrain units of vs riou. origins an aerial photographs noting the occur- rence anddistribution of geologic factors such as permafrost, potentially unstable slopes, potentially erodible soils, possible buried channels, potential construction materials, active 11oa6 plains and organic materials. Engine.ring characteristics listed for the delineated aow alls a se.sment of each terrain uhIt's Influence on projects feaLLtres. The terrain ,it analysis serves as a data bank upon which interpretations cancerning geamorphologie development, glacial geology, and geologic history could be bleed. Additionally, this subtask provides base maps for the maiplfation and presentation of vartous other SusAra Hydroelectric project activities. The area of photo coverage was divided into units of workable size, resulting in 16 map sheets. Rase maps were prepared from photo —sales and the LarrMD units were delineated on overlay sheets. Physical characieristics and typical engineering properties ware developed for each terrain unit and are displayed on a single table. The execution of this project progressed through a number of step, that ensured the accuracy and quaitty of the product. The first atop consisted of a review of the literature concerning the geology of the Upper Susitna River Basin Intl transfer of the information gained Lo high-level, photographs at a scale of 1: 125,000. interpretation of the high-level photos created a regional terrain framework which would help In the interpretation of the low-level 1:24,000 project photos. Major terrain divisions identi- fied on the high-level photos were than used as an areal guide for delineation of more detailed terrain units on Lhe low-level photos. The primary effort of the subtask was the interpretation of 300-pins photos covering about BOO square miles of varied terrain. The land area covered in the mapping exercise is shown on the index map sheet and displayed In detail on the 21 photo mosaics. Ouring the low altitude photo Interpretation a preliminary work review and field check was underlaken by R&M and L.A. Rivard, terrain analysis consultant. A draft edition of the Terrain Unit maps and report was completed and submitted for review to ACRES and L.A. Rivard. Comments and questions generated in the review of the draft report were analyzed by R&M and a —end field check was undertaken. The final revised maps are Included herein. Terrain units composed of or including bedrock Are shown on the Interpretation. However, these divisions are interpreted only as weathered or unweathered bedrock. Detailed petrologic designa- tions and age relatlens of the rock units have been synthesized from U.S. Geological Survey sources (Cseitay, 1976) and project field mapping accomplished to date. flock unit designations from these sources are included on the maps. Lineaments, features - of -Interest, and potential faults have not been shown as their delineation is outaide the scope of R&M's work. limitations of Study This is a generalized study which is intended to collect geologic and gentechnical materials data for a relatively large area. Toward this goal, the work has been successful, however, there are certain limitations to the data and �nlerpretations which should be considered by the user. The engtoeeriog characteristics of the terrain units have been generalized and described qualitatively. When avafuating the suitability of a terrain unit for a specific u , the actual properties of that unit should be verified by --ate subsurface Investigation, sampling, and Eahora Way testing. An important factor in evaluating the engineering properties, composition and geologic characteristics Of each terrain unit is extensive field checking and subsurface investigation. The scope of the current project allowed only limited field checking and Al subsurface investigations to date have been restricted la Lhree terrain units clustered around the Watana site. This lack of ground -truth data further restricts the use of the terrain unit maps and engineering inlarpmLaU,n chart for site specific applica- Hans. TERRAIN UNIT ANALYSIS A landform is defined (Kraig and Roger, IS76) as any element of the landscape which has a dehneabie composition Intl range of physical and visual characteristics. Such characteristics can include topographic form, drainage pattern, and gully morphology. Landforms classified inla groups based In common modes of origin are most useful because similar geologic processes usuaiiy produce similar topography, Sail properties, and englnecring character- lot!-, The terrain unit Is defined as a special purpose term comprising the landforms expected Lo Occur from Lhe ground sur- face to a depth of about 25 feet. It has the capability to descrIbe not only the most surficaf landform, but also, an underlying land - form when the underlying material I. within about 25 feet of the surface (i.e. a compound terrain unit), and areas where the Surficial exposure pattern of two landforms are so intimately ur complexly related that they must be mapped as -a terrain unit complex. The terrain unit is used in mapping landforms on an areal basis. The terrain unit maps for the proposed Susitna Hydroelectric Pmject are• show the areal extent of the specific terrain units which wereidentified during the airphoko investigation and we tMbluated in part by a limited on -site surface Investigation. The terrain units, as shown on the following sheets and described in this text, document the general geology and geotechnical chary seUristics of the Susitna Hydroelectric Project area. On the maps each terrain unit is identified by letter symbols, the first of which is capilalized and indicates the genetic origin of the deposit. subsequent fetters differentiate specific terrain units In each group and when separated by a dash, identify the preserve of permafrost. During terrain unit mapping bedrock was identified, as per es- tablished techniques, only as weathered bedrock or unweathered bedrock. Details of bedrock geology shown on the mosaic maps Is derived from esajtey's USGS open rile report on The Geology of in, To flo-tna MIS. (1979) and from Acres American (unpublished data, 19111). The letter designations are used here as those authors defined them and the rock units are shown only where the Ffg - Granular Alluvial Fan: A gently sloping cone generally GFk - Hama Deposits: Hills, ra ants and canes of phominterpretabon located bedrock an the maps. There has been composed of granular material granular ice contact deposits no attempt to Correlate units ..-as area- of limited exposure or to with varying amounts of Silt formed by streams as they flow modify the outcrop pattern. Bedrock symbols are shown in slanted deposited upon a plain by a on or through a glacier. letters with the capital letters defining the age of the unit and stream where it i s from a faimnwir[g lower case letters describing the reek type. narrow valley. The primary L-f - LACUSTRINS DEPOSITS: Generally fine-grained materials depositional agent Is running laid down in the Copper River Terrain Unh_._ t Descriptions water (for sogfluction fans, see pmglaciaf Lake and gravelly Crikuelal Landforms). Can In- sands deposited Tn the Watana Far this photo Interpretation wo rcise, the soil types, engineering dude varying proportions of Creek - Stephen Lake proglacFal Properties and geological conditions have been developed for the 14 avalanche or mudflaw deposits, lake. Often frozen as denoted by landforms or Individual terrain units briefly described below. especially in mountainous regions. modifier "-f`. Several of the landforms have not been mapped independently but Fans are generally unfrozen. rather as compound or complex terrain units. Compound terrain units result when onelandform overlies a second recognized unit rp - rioodpiain: Deposits laid down by a river or O - ORGANIC DEPOSITS: Deposits of humus, muck and at a shallow, depth (less than 25 feet), such as a thin sheet of stream and floodd during periods peat generally oc urring in hogs, glacial till overlying bedrock or a mantle of iacustrhe sediments of highest water in the present fens and muskegs. Frequently overlying till. Complex terrain units have been mapped were the scream regimen. Floodplains are overlies frozen material. surficl.t exposure pattern of two landforms are so intricatly related composed of two major types of Special Symbols and Landforms that they must be mapped as a terrain unit complex, such as some alluvium. Genera€Ey granular areas of bedrock and catiuvlum- The compound and complex riverbed (lateral accretion) de- In addition to the terrain unit symbols, Several special symbols are terrain units behave and are described as a composite of individual posits and generally fine-grained used on the Terrain Unit maps to denote landslide Scars, terrace landforms comprising them. The , ragarlphy, topographic position cover (vertical accretion) deposits scarps, frozen soils, buried channels and trail., and areal extent of all units are summarfzed an the terrain unit laud down above the riverbed properties and engineering mnterpretallons chart. deposits by stream. at bank Well defined landslide scarps, which indicate relatively recent overflow (flood) stages. failure, are shown as lines fallowing the scarp trace with a Ex - BEDROCK: In place rack That is overlain by Indicating the direction of movement. Visible an the aerial photos a very thin mantle of unconsal- FpL - Old Terrace: An old, elevated floodplain within many of the terraces and autwash deposits are several idated material or exposed at the surface nlonger subject In different surfaces which may be related La sedimentation at a urr.c.. Two modifiers have frequent flooding. Occurs as temporary base level which was followed by renewed incision. The been used for all types of bad- horizontal benches above present Various outwash and stream terraces are noted by lines folloseing rock whether Igneous, sedlmen- floodpFains, Intl genermy com- the scarps separating the different elavatlon surfaces, with tick Lary or metamorphic. Weathered, posed of materials very simllar to marks on the side of the lower surface. permafrost sells have highly fractured, or poorly con active Naodplm... been delineated on the terrain unit maps through the use of an -f somiciated bedrock Is Indicated by following the terrain unit letter designation. By convention the Ure modifiers ewa (as I. Bxw); GIs - Ablation Tigh Relatively younger ablation till symbal -f Es used where the permafrost is thought In occur at unweathered, nso}idated bed- sheets with re pronounced more least discentlnously. Sporadically frozen areas have not been reek is Indicated by the modifier nmm hucky mprem topography and defined on the maps, however, the possible aceIrrance of frozen °ua (as In Rxu). A modifier or less dissected than than older till special symbol for frozen bedrock sheet.. These deposits are pre- material within a terrain untt is described En in, proceeding section on definitions and on the engineering interpretation chart, has net been used, afth.ugh dominantly of the Naptawn, bedrock at higher elevations may Glaciation, contain abundant Burled channels along the Susitna River have been delineated by be frozen. cobbles and boulders, and consist the use of opposing parallel rows of triangular teeth. Most of If water -worked till. The able- these features are minor and should have no impact on the present C - COLLUVIAL DEPOSITS: Deposits of widely varying com- Ilan till may be sporadically position that have been moved frozen in the Denali Highway studies, however three buried channels south of the southern abutment at the Devil Canyon damsite, should be Investigated to downslcpe chiefly by gravity. access corridors. assess potential leakage around the dam. A similar but larger Fluvial Sk,pewash deposits are buried channel extends from near the mouth of Deadman Creek to usually intermixed with coiluvial Gtb-f - Basal Till: Basal glacial till sheets, with deposits. subdued moraine morphology, T..... a Creek. The trough is filled with quaternary sediments of which in Lhe Watana Creek- several different types and ages some of which may have a High transmissibility. Because thls channel bypasses the Watana damsite CI - Landslide: A lobe- or tongue -shaped deposit Stephan Lake area are relatively daLailed of rack rubble ar noo—ofidit.d older (probably deposited during work should be directed towards determining its width, debris that has moved downslope. Eklutna and older gladations)and depth, apil types, and potential for reservoir leakage. Includes reck Intl debris slides, elsewhere are as young a slump blacks, earth flows and Naptowne age. Often frozen in Existing jeep and/or winter sled trails have been noted on the Terrain Unit maps by a dash -dot Sine. debris flows. young slides are the WaLana - Stephan Lake area generally unfrozen while older with a higher slit and ground ice Terrain Unit Properties and Engineering Interpretation Chart slides may be frozen. content as denoted by modifier -fa; generally unfrozen In the In order in evaluate the impact of a terrain unit with respect to cs-f - SoliflucTion posits: Solill—tion deposits are formed Gold Creek - Indian River area; specific project features an interpretation of the engineering char - by frost creep and the slaw and possibly frozen hetween acterimVC. of each unit is provided. On the chart the terrain down -slope, viscous flow of Watana Camp and the Denali units are listed in horizontal rows and the engineering properties saturated soil material and rock Highway. and parameters being evaluated are listed as headings far each debris In the active layer. This column. Within the matrix formed are relative qualitative char - unit Es generally used only where GFa - Dutwash: Coarse, granular relatively level scterizations of each unit. Several of the engineering properties obvious sofif€uctior lobes are floodru in formed by a braided and evaluation criteria are briefly discussed below. The chart Is identifiable. Inclvdes fTne- stream flowing from a glacier. presented for general engineering planning, and environmental grained colluvial fans formed assessment purposes. In this form, the data are net adequate for where solifluction deposits emerge GFe, - Esker Deposits: Long ridges of granular nee- design purposes but when additional laboratory and field Informa- fro confined channel an a hill- contact deposits farmed by tion is acquired and synthesized, site specific development work Side onto a level plain or va Hey. streams as they flow in or under Can be minimized. re These landforms a often frozen a glacier. as denoted by "-f" SEE SHEET 11 FOR CONTINUATION Engineering Interpretation Uennitions: Ground Water Table Depth W the ground water table presence of permafrost may Is described in relative terms significantly increase the Slope Cfassification Fallowing guidelines established ranging from very shallow to strength of so a fine grained by the U.S. Forest Service, the deep. In construction Involving soils 'Tut indicated an the chart Bureau of Land Management and excavation and foundation work, by the thermal state qualifying the American Society of Land- special techniques and planning stat.,dent). seep. Architects, slopes In the will be required in most aas project corridor have been with a shallow water table and In Slope Stability Th. Slope stability qualitative divided Into the following s e of the areas with a mode,- raliAl was derived through classes: Flat - 0 to 5%; Gentle • ately deep water table, In areas avaldztien of each terrain units' 5 [0 15%, Maderil - 15 to l of impermeable permafrost a topographic position, slope, soil and steep - greater than 25%. shallow perched local water table am pdsitlon, water content, ice References have been made to may occur. content, etc. The stability steep local slopes to account for asses€ment considers all rapid small scarps and the similar Probable Permafrost Distribution The cnce of permafrost ma ss Wasting processes (slump, short but steep slopes which and the degree of continuity of rock slide, debris slide, mud - characterize Ice contact glacial frozen .it Is descrItwd on the flaw, etc.). Several terrain drift. Engineering Interpretation units which have rhiracier- Chart, by the finlawing retail- istically gentle slopes and are Ptebabfe Unified Sall Types Based on the laboratory test terms: Unfrozen- generally communly in stable topographic results, field observations, without any permafrost; positions have been oversteepend previous work in similar areas, sporadic - significantly large by the recent, active under - and definitions of the soils,a ..... are frozen. Site specific cutting of streams andlor man range of unified so# type. has work may he required before (or by older processes not been assigned td each terrain design; DlsconUnous - most of currently active such as glacial unit. Often several soil types the area is underlain by frozen erosfdn and tectonic uplift and are listed, same of Which are soils - site specific work ,s faulting), The stability of the much less pre-lant than others. required unless design Incorp- terrain units on oversteepend Information I. the sole orates features relating to perma- slopes and natural slopes is stratigraphy column will aid In frost; Continues - the entire described on the Engineering understanding the range and area Is frozen. All designs Interpretation Chart. distribution of ..it type.. Study should be based on occurrence of the borehole logs and lab test of permafrost, suitability as a Source of Sulu will give site specific Borrow Great quantles of barrow mate - unified ..It types. Frost Heave Potential Those soils which comain signi- risk will be nced.d for all ficant amounts of silt and fine phases of construction. The Drainage and Permeability Now the soils compH.Thip the sand have the potential to pro- rating considers suitability as pit terrain units handle the Input of duce frost heave problems. A run and processed agg,.gift. or water is characterized by their qualitative low, moderate, and impervious core and takes info drainage and premeabigty. high scale rates the v Ious soils account the materials present as Permeability (hydraulic canduc- based on the pol...Val severity well as the problems associated Vivify) refers to the rate at of the problem. Where the soil with extracting material from the Welch Water can Flow through a stratigraphy is such that a frost various terrain units. soil. Drainage describes the the susceptible, soil overlies a coarse wethess of the terrain unit, grained deposit, a dual classifl- REGIONAL QUATERNARY GEOLOGY taking Into account a combinatlon eaten is given; for these lolls it of premeability, slope, topo- may be possible to strip if the graphic position, and the pro.- frost ruse,table, material. Quaternary glacial events throughout South -Central Alaska pro- isety of the water table. f ndly affected the soils, landforms, and terrain units occurring Thaw Settlement Potential Permafrost soils with a sign- In the project area. This history has been discussed and pa,tially Erosion Potential Erosional potential as described ific—t. volume of Ice may show deciphered in papers by Karlafrom (1064), Pewe (1965), Ferriaos here, considers the materials a, settlement of the ground (196h), and Wahrhafting (1958). However, these Tnvestigatlons are iikelyhood of being moved by surface upon thawing. In gee- of such scope as to ..it. them of limited value here. The photo- eolian and fluviaf processes such eraI, clays, slits and fine sands interpretation and resultant terrain unit mapping is the most as sheetwash, rip and gully have the greatest settlement detailed study of the Upper Susitna River Basin. The following formation, and larger channelized potential, farming the basis far discussion of Quaternary Geology is a synthesis of the new Tnfor- flow, In general this relates to the throe fold classfflcatio, motion, derived during the photolnterpretauon, supplemented by the partical size of the soil, presented on the chart. Un- data from published sources. however, the coarse sediments of frozen sails do not have the floodplains have been rated as potential for thaw semement, as The major topographic features of Southrmtral Alaska were es - high because the surface is very denoted by not applicable" tabitshed by the and of the Tertiary Period, What Ts now the active, and likewise coarse (NA). Thawing problems may be Susltna project area was located in the relatively low northern terrace deposits can have a high Initiated or acceliarated by portion of the Taikeetna Mountains, which separated the broad rating because of Chair pl-ke.ty, disturbance of the surfolal soil ancestral Copper River Seat, lying to the east from the ancestral (by virture of the their origin) layers or the organic mat. Susitna cook Inlet Basin lying to the west. North and south of to streams. (Mass wasting the Talkeetha Mountains and the adjacent large river basins stood, potential I. considered under Bearing Strength Sased on the terrain unit soli respectivily, the great arc of the Alaska Range and Chugach slope stability). types and stratigraphy a qualita- Mountains. Streams draining the region that would become the tive description of bearing project study area may have flowed into olther the ancestral strength Is given. In general Copper or Susftna River systems. During the Pleistocene the coarse grained soils have a entire Susitna Project study area was repeatedly glaciated. Each higher bearing strength than of the glacial events would be expected to follow the I— general fine grained soils, but the pattern with several advances most likely reaching the max,mum event described here. The onset of a given glacial advance in Soulhcentral Alaska would be marked by the lowering of the snowlina on the regions numerous mountain ranges and the growth of valley glaciers, first in the higher ranges and those closer to the Gulf of Alaska. Advancing glaciers from the Chugach, Wrangell, Alaska and southern Talkeetna ranges would flow out of their valleys and coalesce W form large pledmont glaciers spreading across the basin fleoes, while the ice of the northern Talkeetna Fountains (In the project area) wouftl still exist as valley glaciers. The piedmont glaciers of the Chugach and Wrangel Mountains would at some point be expected to merge, damming the ancestral Copper River and creating an exte" ve proglacial lake in the Copper River Basin. Alaska Range glaciers flowing southw.rd would black possible ancestral drainage paths of the upper Susltna River creating a second lake which covered much of the project area and merged with the lake Filling the Copper River basin. Glaciers flowing from the Kauai Mountains and southern Alaska Range would also merge creating another progladaf lake in Knik Arm, Cook Inlet, and the Southern Susitna Basin. Continued glacial advance would fill the basins eliminating the lakes and possibly forming art ice dame. Ice shelves may have extended many miles into Tha Gulf Of Alaska. At this maximum stage many mountains In the project area were caopietely buried by Ice as evidenced by their rounded summits while numerous others existed as n t—hIRs. The degiacialion of Southcentral Alaska would follow a similar pattern but in reverse. wasting of the ice would uncover peaks in the project area and the thinning and retreat of the glaciers In the Copper River, Upper Susitna and Cook Inlet regions would again allow lakes to form. Continued melting of the glaciers would remove Ice dams blocking the proglaclal lakes possibly creating a catastrophic (trench cutting) outburst flood. Intervals between glacial advances would be characterized by the fuvial entrenching of the Susitna and Copper Rivers and their tributarles. The earlier glacial events of the quaternary Period are poorly known In the Upper Susltna Basin due to both the erosion of the older deposits and their burial beneath younger deposits. However, from the alpine topography and minor glac€iv Sediments left on high stapes it can be demonstrated that early PI-ISLarene glaciers completely covered Southcentral Alaska as m the maximal event described above. Most of the glacial deposits that remain and the terrain units used to describe then have resulted from later glacial events. The last glaclatlon to completely cover the project area is of un- certain age. It has been interpreted to be of Eklutna age by Karlstrom (1964) which may be correlated with the Hilnolan glada- tion of the Cmtlnental United states (Pewe, 1975), however, with the Ilmlted data available an early Wisconsin (Knik) age may he just as viable. Whatever the age, ice flowing from the Alaska Range, the Talkeetna Mountains and several local highland centers spread across the project lowlands depositing a sheet of gray, gravelly, sandy and silty, basal till (Gtb-f). The till varies greatly In thickness, ranging from the 1004 feet, displayed In - river cut exposures, to a thin blanket ever bedrock. This till presumably overlies older, poorly exposed Quaternary sediments, It Is recognlzed that the basal till, mapped as Gtb-f In the Stephan Lek.-Watana Creek Area may actually represent Several closely related events and that h,eu till in valleys north of Deedman Lake and downstream of the Devil Canyon site was probably deposited during younger glacial advances. Prominent lateral moralises of the major advance occur on the flanks of mountains bordering the central Watana Creek-Staphan Lake Lowland. Overlying the basal till unit and representing the next major depositional event Is a lacustrine sequence. Presumably the lacustrine materials were deposited during the Eklutna (7) Glacial retreat and during much of the younger Knik and Naptowne glacial events. During these stadia) events glaciers from the Alaska Range blocked drainage down the present Susitna channel and probably through a low dfvlde between Watana Creek and Butte Creek; 7aikeetna River valley glaciers blocked low divides between Stephan Lake and the Talkeetna River; and the Copper River Basin was Occupied by an extensive proglaciaf lake. The lacustrine deposits mapped within the project area me L and L/Gtb-f, cover much of the Watana Creek -Stephan Lake Lowland and extendupstream along the Susitna River to the Susitna- Copper River Lowland. In the Watana Creek -Stephan Lake Lowland the unit is generally less than 20 feet thick and composed of medium to fine sand with a significant gravel content. The lake deposits of the Copper River Lowland are thought to be much thicker and finer -grained. The coarseness of the lacustrine sediments (i.e. gravelly sands in the Watana Creek -Stephan Lake area ) is not unexpected as the ancient lake was impounded bahfrd and ringed by glaciers which were activity calving into the lake. During the fate Naptowne glacial event, in the Watane Creek - Stephan Lake portion of the prog{ecl.i lake, several claims and stlindline features were formed at about the 3,000-foot elevation. This shoreline level Is higher than most reported shorelines of the proglociA lake .-upping the Capper River Basin. It I. Possible then, that during the Naptowne staidiai the Watane Creek - Slephan Lake proglacial Fake stood at a higher level because it Was impounded bearng another ice dam In the Kesina Creek - Jay creek . a e . It is also possible that an outlet exsisled for much of the lifeof the fake (conceivably In Koslna - Jay Creek area). Flow from the lake would remove great quantities of fine grained suspended sediment, causing a relative increase in the coarseness of the sediment deposited I, the lake. Hummocky coarse grained deposits of abetm. till (Gta) overly I ... Itrine sediments between Tsusena and Deadman Creaks and h .sal till in the valleys north of Deadman Crack and in the Denali Highway area. These materials may be correlative with eskers and kames found along the Susitna River between the Carmine and Tyone Rivers, and together they represent the extent of the last major advance of glacial Ice Into the project area. . They are ten- tatively determined to be of Nap[awne age (Late Wisconsin) (Karlstrom, 1964) suggesting that the Knik Age glaciers were less extensive and their deposits were overridden and masked by Naptowne deposits. Lacustrine sediments of the large glacial lake Occupying the Stephan Lake - Watana Creek lowland have not been mapped evertyTng the ablation till, indicating that some, of the ablation till and ancient Watana Creek -Stephan Lake lacustrine sediments were time syncronus and that the progec€al lakes were drained shortly after the Naptowne maximum. one should note that several Isolated deposits of ablation till are not necessarily indicative of this late advance and ice of Naptowne age did not deposit ablation till in all localities (most importantly in the Portage -Devil Creek area and In the area between Deadman Lake and the DenalT Highway); and that IacusIl sediments deposited in small isolated preglacial lakes have been found overlying ablation till. Intervals between glacial advances would be characterized by f€uvlal erosion and entrenching of the project area portion of the ancas[rei Susitna and its tributary streams, however, the ma)ority of the in[erstadial fluvial hisory has been destroyed by subsequent glacial and fluvial history. Remnants of the cider entrenching events are preserved In s veral abandoned and buried channel sections along the modem Susitna River. One of the largest ostler channels found, at the Vise Canyon damsite has a bedrock floor (cut below the bedrock floor of the present Susltna channel) which Is now filled with fluvial and glaclo-fluvial debris. The second buried channel, between Deadman and Tsusena Creeks, just north of the Watana site is filled with outwash and lacustrine materials with Intervening till layers (Corps of Engineers, 7979). Because ice of Naptewna and Knik ages presumably did not completely cover the project area, and the tills in the channel have character- Istics similar to the basal till unit attributed to the Eklutna Glaciatlon, it appears that a portion of the ancestral Susitna River valley of similar size and depth to the present Valley existed as early as the Eklutna Glacial event (Hllrafan), Eklutna age till and associated lacustrine sediments also filled some of the present Susftna valley, however, most have been subsequently excavated. The Eklutna age valley may have been graded to drain SFE SHEET ill FOR CONTINUATION seat Into the Copper River Basin. The fact that the present Susftna River flaws In if deep canyon tic ss mountainous terrain (In the Portage -Devil Creek and Jay-Kasina Creek areas), and not across the low Susitna-Copper River of the Stephan Lake-Talkeetna River Divides may be the result of glacial derangement and/ar the rapid drainage of progle,lal lakes causing a pirating of portions of the Copper and Talkeetna River drainages. Other minor channel remnants include three buried channels above and south of the Southern abutment at the Devil Canyon damsite that may be nelasad to the drainage of a proghrlisl lake or as Oid.r Position Of the Susitna River. The channels are probably shallow but should be thoroughly investigated to assess potential leakage around the dam. A small, partially buried channel d—treete of portage Creek and another near the mouth of Devil Creek are remnants. of the downculting phase or the Susftna River. Similar channala are found near the river level just upstream of the Watana Damslte and downstream of Watana Creek. The present course of the 5usitna River was probably established during or hafore the Wisconsin Glacial events. Sandy glacial fill observed near the river level at the Devil Canyon site may have been deposited by the glaciers forming the Naptowne Age Ice dam. if this is the case, and the till is In -situ than most of the bedrock dawncutting and removal If Quaternary sediment from the 5usitna channel was accomplished before the and of the Wisconsin. If the till deposit near water level in Devil Canyon i older than the Napt.— eat (Knik Ekultna)5 It ouid indicate, an earlier Incislon data and that the river followed its present course since the Eery Wisconsin at least. Numerous modifications of the glaciated surfaces and the devd,p- ment of non -glacial landforms has characterised the Sustlra project aria Since the PNislacene. The stream inrisfon, as previously discussed, has produced or at least excavated the V-shaped Susitne River Valley within the wide giaclated valley floor. This has rejuvenated many tributary streams which are now down - cutting in their channels, as Is evidenced by the steep gradients In the lower portions of their channels, lawar gradients in the mid-channei section and frequently a waterfall niche - point separating these stream segments. Several law terraces (Fpt) have been formed above the modern floodplain (Fp) of the Su5ltna and jls major tributaries. Terraces at several different levels were found throughout the Susitna River Valley. Some occur high an the valley walls as eroded terrace remnants (upstream of Watana Creek); while others appear as very recent, law, flat planar features. Hear the mouth of Kasina Creak sad in several other locations, the terrace materials overlie relatively shallow bedrock such that they may more accurately he called bedrock benches). Between the Oshetna and Tyone Rivers the thin terrace gravels overlie glacial till. The terraces are frequently mOdtfied by the deposition of alluvial fan dehrle (Ffg) and/or the flow of eel€fluc- tion label and sheets (Cs) across their surfaces. Correlation of the terrace levels on the air photos is difficult because Of the lack of continuity and was, therefore, not attempted. In the Gold Creek area three different, low level terraces are clearly visible and in the Tyone-Oshetna Rivers area four terrace levels can be discerned. Between these areas the terraces rarely occur in groups and are more widely spaced. Most tributary streams also show multiple terrace levels with the best example being in Tsusera Creek where rive or more levels appear as steps on the Valley wall. The stream lerreres are frequently modified by the deposition of alluvial fan debris (Fig) and/or the flow of solifluction lobes and sheets (Cs) across their surfaces. Alluvial fans have also been deposited where steep small drainages debouch onto floors of wider dieclated valleys. Frost cracking, cryoturbation and gravity have combined In form numerous rottuvial deposits. Steep rubbley talus cones have accumulated below cliffs and on slightly less precipltlam: stop,, thin deposites of frost churned tors cover bedrock terrmn (C). an numerous slopes in highland areas (.a long Devil Creek) and n the broad lowlands so€ifluor- has madifled the surficial glacial till and/or lacustrine deposits, The development of a number of landslides (Ck) has occurred throughout the project area. Most landslides were found within the basal till unit (Gtb-f ar L/Gtb-f) an steep slopes above actively eroding streams. The Incidence of failure within This material appears La be strongly related to thawing permafrost and consequent sail saturation. Th, basal till unit is frequently over- lain by lacustrine material and the lacustrine materials fall with the till. Most failures occur as sonalt shallow debris slides or debris flows, how,vsr, a few large slump failures occur. Tha slumps and debris flews are marked with a special symbol an the Terrain Unit Maps. steep rock slopes are assumed to be stable. However, this is undaubtedly not the case where unfavorably ortonted dis- continuitjes dip out of the rork slope, such discontFnuFties ..at be identified and their effects assessed during on -site rock slope stability investigations. Finally, revegetation of poorly drained portions of the landscape has produced numerous scattered deposits of organic materials (o); and Permafrost has developed in many areas. REGIONAL BEDROCK GEDLOGY The bedrock geology of the Talkeetna Maunder- and upper Susitna River Basin I, examined in numerous publications varying In nature from site specific to regional. The ..at comprehensive report is by Bela Csejtey (1978), entitied the Geology of the Talk-tn. Mountains quadrangle. This paper and map deals with the ages, lithology, structure, and tectonics of the rfolons reek units. His results, supplemented by unpublished data from recent project field mapping, are the basis of this report's bedrock unit identification. Csejtey (1978) concludes that southern Alaska developed by the accretion of a number of northwestward drifting continental blocks on la the North American plate. Each of these terrains had a somewhat ind,p,ndent and varied geologic history, consequently, many lithologies with abrupt and complex —facts are found. Csejtey notes that "the rocks of the Talkeetna Mountains region have undergone complex and intense thrustIng, folding, faulting, shearing, and differential uplifting with as socjated regional metamorphism, and plutonlsm". He recognizes at least three major periods of deformation: 'a period of intense metamorphism, plulonism, and uplifting In the Late FaHy to Middle Jurassic, the plutonic phase of which persisted Into Late Jura554cr a Middle to Late Cretaceous alpine -type orogeny, the mast intense and important of the three; and a period of normal and high-anglo reverse faulting and minor folding In the Middle Tertiary, possibly extending into the Quaternary". Most of the major structural Features of the Talkeetna Mountains trend northeast to southwest and were produced during the cretaceous Orageny. Major bedrock lithologies as mapped by Csejtey, and included oa the terrain unit maps, are summarized as follows: Tv Tertiary volcanic rocks of sun ... 1.1 and shallow intrusive origin with a total thickness of over 1,500 feet. The lower part of the sequence cons late of ..all stacks, irregular dikes, flaws and thick layers of pyroclastic rocks of quartz Hitt., rhy.lit. and lathe campasition. The upper part of the sequence c slats of ..desire and basalt flows inter ...d with tuff. These rocks are mapped in Fog Creek and its major tributary. Tsu Tertiary normarine sedimentary rocks Including fliviatile conglomerate, sandstone, and th"Ione with a few thin lignite beds. The only known exposures of this unit are in Watant Creek. Tbgd Tertiary biolits granadiorite forming stocks which are behoved to be the plulanic equjyaient of unit Tv. The most exonsiye exposures are found on either side of the S,aSitna River from just up- stream of the ❑evil Canyon damsite to the northward bend in the river ahaut Six miles upstream of Devil Creek. An outcrop or Tertiary hornblende granodiorite (Thgd) is located just west of Stephan Lake. Tsmg Tertiary schist, migdatite, and granite which d5play gradational contacts. The schist and lit-Aar-tTt mjgmaLite are probably products of contact metamorphism with the entire unit po sslbly representing the real of a large stock. The rocks occur In appracialabSy equal proportions with the largest exposures occurring In Tsusena Butte, west of Deadman Creek, and in the rec- tangular southern jog in the 5usitna River. Csejtey maps this utjlt at the Watana damsita, however, more recent -Held work (ACRES, 1901) has shown that they Watana damsite bedrock conststs of diorite sad andesite. TKgr Tertiary and/or Crelagacus granitic rocks forming small plutons the largest of which is found In the headwaters of Jay Creek. Jem Jurassic amphibolile with minor inclusions of greenschisl and occasianat laterlayers of marble. The unit Is probably. derived from neighboring basic wlcaric formatters. The amphibolite ex- tends from the Vee Canyon damsite downstream for about 12 miles. Other Jurassic rocks which Occur in extremely limited exposures include Trondj,tate (Jtr) and granedl— te, (Jgd) litholagies. ' TRv Triassic basaltic metavalranic racks form €n a shallow marine anvirrnment as evidenced by thin interbede of metach,rt, arglllite and marble. Tha individual flaws are reported as up to 10 meters thick and displaying pillow structure and colum- nar jointing. This unit is mapped, in the project ar in the mountains east of Watana Crack. Pzv Late Paieozom basaltic and andesitic metavokcano- genlc rocks which form a broad band tic s the central Talkeetna Mountains from the southwest to the northeast. The 5,000. foot sequence is dominantly marine €n Origin suggesting that It is part of a complex volcanic ore system. The majority of the band of this halt crosses the Project area just west of Tsisi, Kasina and Jay Creeks. Near the lap of this ..It Several metamorphosed iimestone reef deposits (I'll) have been mapped. Hag Cretaceous argillite and graywacke of a thick intensely deformed flyschlilce turbidite sequence, Low grade dynamet—Orphism la the low green - schist fades has allowed s oral early investi- gators to map portions of this unit as phyllite. The graywacke beds for. about 301 to 40% of the unit and tend to be clustered I. zones 1 to 5 meters thick. This unit is exposed at the Devil Qanyan site. It extends downstream bcyand Gold Creek and forms the mountain immediately east of Gold Creek. TRvs Triassic metabasalt and stela in an Interbedded, shallow marine sequence found in t- atlochth- onau5 blocks In the upper sections of Portage creek. 5everai of the above units have been used to describe rocks mapped by Acres between the Watana and Devil Canyon damsites. Where this data was available It took prcidence over Caejley's map. REFERENCES Listed below are some references which may be of help in provid- ing background information andl- details concerning the soft, and bedrock of the project area. Anon. (1978) Seismic refraction velocity profiles and discussion, Watana and Devil Canyon Oamsltes. Shane n & Wilson, Inc, Geological Consultants, in the Corps of o Engineers, 1979, Supplemental reasib€Pity Report on the Southeentral A,Ilbelt A—, Alaska; Upper 5usitna River Basin, Hydroelectric Power and related purposes. Anon. (1975) Southcentrsl RaHbelt Area Alaska, Upper Susftna River Basin Interim Feasibility Report. Hydroelectric Power and related purposes. Prepared by the Alaska District, - Corps of Engineers, Anon. (1975) Suhsurface geaphysicei exploration, proposed Watana ❑ameIt. on the Susitna River, Alaska: by Dames & Moore. In the Carps of Engineers (1875) interim Feasibility Report on the Southrentral Railbelt Area, Alaska, Upper 5usitna River Basin, Hydroeiectric Power and related purposes. Aron. (1962) Engineering Geology of the Vee Canyon Damslte: Bureau of 11-1—at"ran unpublished report 37, p. 4, APp.arres. Anon, (1960) U.S.B.R. Report an the feasjhility of hydroelectric development in the Upper 5usitna River Basin, Alaska. Arlen. (1979) Southcentrfl Rallbeit Area Alaska, Upper 5usitna River Sasin - 5uppletnental Feasibility Report Hydroelectric Power and related pvrpases. Prepared by the Alaska District Corps of Engineers. Capps, S.R. (1940) Geology of the Alaska rc H,dad region. U.S.G.S. Bulletin 907. Csejtey, B., Jr., W.H. Na15an, D.L_ Jones, N.J. 5111.. ling, R.M. Dean, M.S. Morris, M.A. Lanphere, J.G, Smith, and M.L_ Silberman 0979) Reconnaissance geolggic map and ge.- chonofogy, Talkeetna Mts. Quad., northern part of Anchorage Quad. and southwest corner of Healy Quadrangle, Alaska. U.S.G.5. Open File Report 78-558-A. Ferrians, O.J., Jr., R. Kachadoorian, and G.W. Gr.ene (1969) Permafrost and related engineering problems 11 Alaska, U.S.G.S. Professional Paper 678. Ferrians, O.J. and Nichols, Donald R. (1965) Resume of Quaternary Geology of the Copper River Basin, In Guidebook to the Quaternary Geology of Central and South -Central Alaska, Guidebook for IHQUA Flair! Conrerence F. Troy E. Few- Fait— Kachadoorian, R., and N.J. Moore (1978) Preliminary report or the recent geology of the proposed Devil canyon and Watana damsites, Susftna River, Alaska, In the Carps of Engineers, 1979, supplemental reaslhilty Report on the 5outhcentral R,Hbol. Area Alaska; Upper SUS tea River Basin, Hydro- electric Power and related purposes. Kachadoorian, R., D. Hopkins, and D. Nichols (1954) Prailminary report of geologic factors affecting highway construction In the area between the Susftna and Maclaren kivers, Alaska. U.S. G,5, Open -File Report 54-137. hashed oorian, R., T. Pewe (1955) Engineering geology of the southern half of the Mt. hares A-5 quad, Alaska. U.S.G.S. Open -File Report 55-79. Kreig, Raymond A. and Richard D. Reger, (197S). Preconstruction Terrain Evaluation for the Trans -Alaska Pipeline Project; in Geomorphology and Engineering, D.R. Coates, Ed, D—citn, Hutchinson and Ros, Inc., (Wiley), 160 pp. Kreig, Raymond A, (1977). Terrain Analysis for the Trans -Alaska Pipeline. Glv1i Engineering - ASC€, July, 1977, Karls[rom, T. N.V. (1954) Quaternary Geology the Kenai Low- lands and Glacial History of the Cook Irtlet Region, Alaska. U.S.G.S. professional Paper 443. Miller, J.M., A.E. Belon, L.D. Gedney, and L.N. Shapiro (1975) A look at Alaskan resources with Landsat data. Int. Symp. Remote Sensing of the Environment., Proceedings, No. 10, -1. z, p. 879-883. Raw,, T.L. (1975) Quaternary Geology of Alaska U.S.G.S. Prof. paper 835. Pewe, T.L. (Ed.) (1965) INQUA Conference guidebook to central and 5outhcentral Alaska. VIE Congress of the International Association for Quaternary Research, p.141. RTeger, 5., ❑.B. Schoephorster, and C,E. Furbush (1979) Exploratory soil Survey of Alaska. Soil Conservation Service Report. steel., W.C. and J.R. L.Campte (1978) Map showing interpretation of Landsat Imagery of the Talk-tn. Mountains Quadrangle, Alaska. U.5.G.5. Open -File Report 78-558-13, wahrhaftlg, Clyde (1959) Quaternary and Engineering Geology In the Central Part of the Alaska Range. 11.5,(1 Professional Paper 893. TERRAIN TERRAIN TOPOGRAPHY SLOPE PROBABLE DRAINAGE AND GROUND PROBABLE FROST THAW SUITABILITY UNIT UNIT SOIL CLASSI— EROSION BEARING SLOPE AND AREAL UNIFIED PERMEABILITY WATER PERMAFROST HEAVE SETTLEMENT AS SOURCE GYMBOL NAME DISTRIBUTION STRATIGRAPHY FICATION IN UNFROZEN POTENTIAL STRENGTH STABILITY SOIL TYPES TABLE DISTRIBUTION POTENTIAL POTENTIAL OF BORROW SOILS unweathered, Cliffs in river canyon rauntletl Moderate t Near- xu consolidated knobs on broad valley floor and - Vertical - aW Deep '- Nil NII Very High Moderate [o High Fin. - Poor bedrock ountaln peaks. Co.,.. -Goad Predaminantly found at the base Sporadic at Low CCOEluvlal deposits of steeper bedrock slopes s Angular (rust cracked, blocks of Moderate to Stee Gp, GW, GM Elevev- Fine - Poor cealescino es and tans and ock glacier con rock, some slit and sand. P Sw, SM Good/High Moderate to High Deep ❑iscontinseon, at Low to High Low to Moderate LOW to Moderate Low to Moderate Coarse variable Hfoh Elevations CI Landslide deposits Humemocky unconsolidated tle cats mast [eTR alert The P 9 Silty gravels, silty sands and Dnf—en Susitna River and its. major sandy sdisl pp HA. crude con- Moderate to 51ee P GM, SM, ML Poor/Law High Shallow (perched) Active - High Nigh where frozen Low Low Poor tribularlea. furled Idyers. 1nactive -Sporadic Relatively smooth to lobate topo- C 8-f Soli(luctfon deposits graphy created by the flow of Silty sand and sandy alit showing Gently to Steeping SW, SM, ML Dl.cpntin.— to materials subjected to frequent pntr[ed layering. Sloping Frozen High shallow (perched) continuous Hrgh High µtgh Low poor ,re—se/thaw [yc[e$. Granular Biluv1W Low carte shaped deposits formed Rounded cobbles and gravel with F f g fan where hToh gradTent streams flow san d and some ­ some 5 tino Moderate GW, SW Good/High Moderate Sh.A.W Unfrozen Low Low HTgh High Firms - Poor onto fiat surfaces, and layering of matnjals. Coerce - Good Fp rleodplain deposits Fiat plains, lJfohtly above and adjacent to the Rounded mbblea, gravaf and send Flat GW, GP, SW Surficlal silt. present Susitna River and Its tributaries. sorted and la Bred. With or y to Gentle Sp, SM Good/High High Very Shallow llnfr°aen Gerorall Low HE h Y ( 9 Low Low, 5end$ High Flhe - Poor ma or without slit rover. for surface cover) d Gr fs High Canoe - "__' Fiat surface remnan Ls of t rmer Rounded cobbles, gravel and sand Ftie' P Terrace floodpialn deposits isole[ad above With some silt covered 6 a thin y Flat to Gentle GW, GP, SW, SP, SM, ML Good/High Law Deep Untrazen General! Low Hi h Y ( 9 Law High L- to Moderate Fin. - pmr present Vocdpf,m, silt layers. Sorted and layered, for surface cover Coarse - Good G Fo Dutwash deposits Bottoms of U-shaped tributary Rounded @ striated cobbles valleys and adjacent to Susitna grave} and .and, crudely sorted Gentle GW, SW Good HI h / g Moderate Shallow to Dee P Unfrozen Low Low High Low t High Fine - Paor area. and fayned, Coarse - Fxcell.nt GFe Esker de It pus Rounded to sharp crested slnuoJs Rounded k striated whblea, ridges In upper Susitna area. grav -, and and. Crudely To Steep Local Slopes GW, SW Good/High Moderate Deep Unfrozen Low Low High Moderate Firte -Poor - well sorted and layered. Coarse Excelent GFk [s Kama deposits Rounded to sharp -nested, Rounded & striated rabbles, and sand. Crudely Steep Local Stapes Fine - Poor hummocky hills. gravel, sorted and layered. Gw, SW Good/High Moderate Leap Unfrozen Low Low High Moderate coarse - Excellent Tributary valley alde walla and valley bottom$ in general, Rounded and striated cobbles, eta Ablation till between Tsusna and Deadman gravel, and sand, no eortTng or layering. Gentle to steepGW, GM, SW, Moderale/Moderat Moderate Shall- to Unfrozen W Sporadic Low to Moderate Law to Moderate Moderate to High Moderate Fine - poor creek hummocky rolling surface, chann.1. Bou}der-cobble tag Eng surface. 5M Moderately deep Con.. •Felt Bottom. of larger H-shaped Gravid VHslltyo sand and o ravely • Gtb-f Basel till (frozen) valleys and adjacent penile dy lavering can sort -Gentle Ing; cob' lea noboulders r ly to spoon P GM, SM, M{ Frozen Moderate Shallow (perched) Discontinuous t High High Low FT.. - Fair slopes, poo to Deep Continuous HFghfWh n frozen Coarse - Poor rounded and striated. In swal.. between small rises on O organic deposits lowlands and In high elevation bedrock a Flat surface to ❑.composed and ucdmotplsed organic material with same silt. Flat PT, OL Pear/Moderate to High 9 Low At Surface Discontinuous High High Very Law Low NII st.pllk. terraces. L+custrinee Lawlantle (below 3000')flat cur- Sandy slit and silty sand with Low when L-f (frozen) face in [he Tyone - D.hOn. River are.. craslonai pebbles, m gravelly and. W o sorted and layered. Gamic 5P, SW, ML Frozen slob 9 Shadow Cperched) Dix—tinuous to Continuous High High Thawed. High when Law Poor Froz LLacuatrine Gently rolling to hummocky our- Stratified andy sift end silty 1 5p SW ML �- Low if Thew.d. eta .edEmnta a r ablation till Ve Tate .......dio Butte Lake g sand over unsorted silt sand v y y Gntle to Moderate ,-- G GM, SW, SM Poor/Maderet. Moderate shop.. S parodic Moderate to Hiqh Moderate t HTgis High When LOW Fine -Poe r gravel. Frozen Cone - Fair LLowlands, Lacuntrine (below 30DO') between sporadic to deposit over Stephan Lake and Watana Creek, Well sorted silty sand and sandy Gentle Moderate Sp, SW. ML. Lacus[rine-Goad/Good Lacuslr?ne-High kwdera[el des Diacentlnuous Low iF Thawed. �IY-f basal till and extendin u tream o pa past the yi g silt over) n base; till. m SM, SM, ML 9ase1 TIH-Frozen Rasa3 Ti -Moderate Y P Gtf G[tt-f - Discon- High High HEoh when frozen Law Poor Tyene River. to Con- I� a, ]� mlirlu,ii,n Smooth to lobat stapiTke top0- graphy on gentle .lopes above the Qf° Unsorted vets, and. & sits Low when G` deposltn (froze) over basal till proplaciei lake level, welt of wl th thin ICe )Byers, contorted Moderate to Steep GM, SM, ML Frozen Moderate Shallow (perched) c ❑i. ontinuous m High High Thawed. Low Poor fh—f (fro en) T.vsena creek. soil layering, Continuous High when Fro en Cs-f Sollffuctian (frgxen) Smooth In lobate and hummock Y Silt .a d gravel and silty Y• n over tilts b!a[ion tCOp eprephy .Fong Deatlm.n gravely sad showing toned end Moderate t Step Gw, SW cM, SM Frozen Moderate Shallow (perched) Pe Discontinuaua to High High Low If Thawed. Law Poor Gf0' till layering. to Deep continuous High when Frozen S.Hfiuction Smooth to lobate flows of Frozen W Silty, send and sandy slit show- deposits (Frozen) fine graind materl found on .Ca-f Ing contorted layering over gentle SW. SM, ML ShMi- (perched) High when Fptover terrace terraw of the Sueltna, frequent between sorted end layered rounded Gentle GW, Sp, SW Frozn Moderate t DeepDiseontin ous High High Frozen. Low Low Flno - Poor 1 sediments the Tyene and Dah.tna Riv.ra. cobbles, gravel and sand. sp, 5M, ML when Thawed. Coarse - Good Cs—f 5o11fluction Smooth to lobate atplika top.- Mixed gravel. sands and silts GW, GM deposits (frozen) graphy on the flanks of sone with thin Ice layers and faint Moderate to Steep 5W, SM, ML Frozen High 9 5 .flow h (parched) OisconYinuous High High High Low Peer Bxu over bed oak m untains, north and south of the 6ev11 Canyon area, contorted soft layering ever bedrock. bedrock Gth-f Frozen basal till Rolling lowland areas and Gravels, silty sand and sandy silt o ver bedrock moderate to steeply sloping rlv.r canyon wells. Tramitl...I to no with layering or sorting, Moderate to Steep SP, SM, ML, b°d-.k Frozen Moderate Shallow (perched) Di-ontinuou. to High High Low If Thawed. Low Poor Bxu r high mountains are... varlyfng bedrock. Continuous High when Frozen G'Q Ablation till over Hummocky rolling surface Rounded and striated robbfes, GW, GM, -weathered transitional to higher mountains gravel and sand, no orting a s Gentle t Steep 5_Wa 5M Good/ High Moderate 5h.11ow to Sporadic Low is Moderate Low to Moderate Low if Thawed Med.r.t Fin. -poor Bxu bedrock adjacent to Deadman Creek. layering, over bedrock. bedrock Moderately deep High when Frozn Ceare. - Fair A Colluvium over High elevation mountain .ream L 1 xu bedrock and and steep slope. alert the • P o An uiar blocks of rock with s o me g Steep t Gp, GW, GM, Good/Law to HighC.. - Poor T Bxu bedrock Susitna River end He major sand and slit overlying bedrock. y o Near vertical SW 5M B r�oc�� Moderate To High Deep Sporadic Low {o High Low to Moderate Low Very High" Mod erat to High g Co.r.e - F.Er exposures tributerlea, CColluvium over Small cliff. out Into tertiary Angular rubble with silt and send .L +Bxw weathered, poorly npn-learine sediments along over poorly __I Watod .and Steep to GM, SM, ML, Good/Low to Moderate SParadlc to p—diuous Fine - Poor �SxW �� con Ild.ted Watana Creek end tertiary over pearly consdlldatd highly Hear vertical GW, SW Moderate Deep ❑E Low To High Low to led.-- Low to Mutlerat —.rate Consa -Poor bedrock volcanics In Fog Creak, eeth.red bedrock. TERRAIN UNIT PROPERTIES AND ENGINEERING INTERPRETATIONS FOR CONTINUATICN, SEE SHRFI Bedrock Mapping Tv Tsu Tbgd Tsmg TKgr Jam or)(Jgd) TV PXV (P/s) Kag Tres Units Abbreviated Tertiary Volcanic asks; shallow Tertiary non rin edimentary rucks,e Tertiary bio;ite gr anodiorite; IncaI Tertiary schist, migmatile — granite, Tertiary and/or Cretaceous granifics Jurassic an,phiboiite, n lusiuns of Triassic basaltic — Late Paleoxnir basr ;l c Cretaceous argi hi [e Trlass'rc me fah asa lI n Veseriptions n[rusives, Npws, and pyroclastics; onglomerate, sand- scone, tone, hornblende granodiorit (Thgtl 1. a esentinq the roof of pa forming small plutonsr green- schlsl d marble; Ipral meta. el am r formed in shallop and andesltic m Ea yolranogenlc rocks, —d graywa ke, of a thick delormed and s,,W a erbndd ed shallow rhyolltic to hasahic. and clans large stack- trondjemi[a fJ[r7 and manna envrrunme, t. local meta.11mestene herbitlite sequence, anne aegaenoe. granudiorlte IJg6 }, (pis 1. fowgrade melamorphisn, Miscellaneous Map Symbols ��7y Scarp Slide Scar h" f Buried Channel Trail l RockCantact 0 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name ttnwean,ered, Bxu ehdated yedrock c colluyial deposits ci LandslTde CS-f Sa llfluctian depesits (fro:en) Ffq t;- W- alwvial an FP Flnpapram depesits Fpt Tamara GFo Ottwash depps;ts GFe Esker deposit, GFk ma depp,n. Gta Ablation till Gtb-f nasal till [frozen) C Organic deposit, L-f ar=strin s e [Ira en) L Lacustrine G sedimet e r Ve ablation till till LLacustrine deposits o Gtb-f basal till (frozen) sell nertlpn Cs-f depnelea (frown) Gtb-f yer basal till CfryaeN snhpnrupn Cs-f depesits (frezen) Gta near ablation till snurin�upn C S`f deposits (frozen} Fpt s�e,meni:are CS-f bolifluciian Bxu aeeosits Urozen7 ne bem eck Gfb`f Frozen basal till - U aver bedrock hblation till Gt❑ - ITKU athcrc6 betlrock CaEluvium o er Tod OxU *BXU bedrock exposures CWa—ltrm p er C +Bxw th-z nr B%W poorly e.,soli- dated bedrock Abbreviated Oeser1,0 ions TerOary \'ulcanic oc ks; shallow In lrusives, flows, antl pyroclasires; rh yolrtic Io basaltic. 1erliary n re etlimentarynrocksr; .nglvmeraie, sand . n. elayst.ne Ter Garl' biaite granonr.rrte; local hornblende gr..n.tlwritu (Thal}. Tertiary schis L. migmatite and granite, re asunting the roof of pa forge stock. TerOarp antlfor [retace.us granrtics lorm'rng small pltnnns, amphiboste. usoons of green- se}vist d marble; a andlemite [ltr) andl _ roe (igd 1. r c baseltic oc ks nshall.w ,ar ine env rnr,merri- Late I'ale.zolc basalfic and andesrtic ta- volcanoyenic .cks, lore! mel+-limestone fV4s ). Crelarenus erglltile tl gray,vac ke, of a tnick delorrrred urhidite sequence, io�v grade mctamorphrsm. fri Iabasall ands sslateT ea ectded shallow ar me sequence_ Miscelloneous Map Symbolsy Scarp "` Slide Scar Buried Channel -°`�l� / Trail / f Rock Cantoct 0 7000 4000 FEET SCALE Terrain Unit Terrain Unit Symbol Name Bxa Unweathered, .I.lidated b.d—k C C.Iluvlai depuiy Cl L—dallds CS-f 5.Linua).n dap—Z (Troa.n) Ffg G—W.r alkw Eal ran Fp Fl—dplaln d.p.slta Fpt Terrue GFo outw..) d.p.au GFe Esker deposits GFk Kam. dep.alu Gta Ablation till Gtb-f Baaai Lill (f-..n) O Organic depoeite L-f Larustrinea (rr.x.n1 Laruatrina Gta sediments . r :bi,ti.n lui�� Lacuatrin. Gt- b d;p.aiu over t,al till (frnxan} 5:11Tiucilon CS-0dp.ait. (lraxen) Gib-f ,z, basal till (rrazen) CS-f S.flfluctEIn deposits (frnz.n) Gto .V.r oblation till CS-f 5.liTluctlon deposits (frozen) FPi o:er terrace . dim.nt. !� C- i� —L Bx`u 5aiifluttion d.p.sita (f-.—) aver bedrock Gtb-f c w bassi till }(V bedrock Bxu Ablation till eather.d bedrock xu +Bxu C.Ilwium aver bedrock and bedrock xw +Bxw wesluvium urea poorly . dated bedrock L iQALASKA POWER AUTHORITY IiILU!I Sa SITNA HYNIMA.LCTRIC PROJECT SUBTASIC 5.02 PHOTO INTERPRETATION TERRAIN UNIT MAPS 7 pPHIL 1981 052502 R£V i510N6 Bedrock Mapping Tv Tso Tbgd Tsmg TKgr Jam (JtrJ(Jgd) Tv Pzv (PW Kag Tres Units Abbreviated Tertiary l'olcanie orks; sha€tow Tertiary no rin Tertiary hiutte Tertiary schist, Ter4iarl' and/or ]urass'vc amphibolite, Triassic basaltic to =akeoxaic basaltic Cretaceous argiliite 'f r;a sic metabasall Deserlptfans intrusive', Bows, nd tlimeniarynrocks;a onglomeraie, sand- slave. and ctaystpne. granodiorite;'loral hornblende granudiarite (T l"d}. m,gmatite and granite, representing throo e f Cretaceous granitics forming small pintons. an of green- srhisi & Snarule; b a metavnlcagir rocks formed In shaiEow and andesi tic m ta- volcanogenic rucks, d graywacke, o a lhl-k ueforroed r and slate, a rnterbetltled rshallow pYroclasiics; rhyoli Tic So basa3Iic. of a large 'Sock. ondjemite (Jv) and amne envrr nment. IpraE meta -limestone urbldl[e sequence, a sequence_ granodiorite (]gd). MO. lowgrade mutamnrphism Miscellaneous Map Symbols Scarp r 'r`f Slide Scor ` Buried Channel Trail Rock Contact 0 0 SCALE 2000 _ 4000 FEET Terrain Terrain Unit Unit Symbol Name unweamered, Bxu otdated bedrock [,' Co33uvial deposits Cl landslide Cs-f So-1t,ii f ( depPosits (frozen) Ffg cranr - alluvial fan Fp Flnadplain eepaane Fpt Terrace GFo 0--h dapnalts GFe Esker depesite GFk ame deposits Gta Ablation fill Gib-f 9asai kill (frozen) 0 Organic duposlts L-f a �atrinee t rra�en ) L tarustrine Gta sediments o r Ve ablation uu L ta«'trine Gtb-f n...I tilla(frozen) smtnt, tian Cs-f deposits ura�en} Gtb-f aaer nasal tit Ifrnaen) Cs-f Sprflueuon deposits Ifr—) Gta r oae amauon rli sohr ocp n Ci S-f deposits (frozen} FPt er terrace sediments Cs-f So3ifluciian Bxa tlJposits (frozen) bedrock a Gtb-f Froaen Hasa! ru over bedrock ghlation t!! Gta eamiid bedrock [okkwium o cr C' hedrock and �'E BXU bedrock exposures Ci cpEEuvlum o e r Bxw +Bxw weathered o poorly consoli- dated bedrock Ff1R rnrJTlulEorinu CFF gkFFT Bedrock mopping Tv Tsu Tbgd Tsmg TKgr Jam (Jlrl(Jgd) kv Pzv (P/5) Kog TVs Onds Abbrevlaled Deser(plions Tertiary volcanic ticks; shallow in lrusives, flows, and pyroclastics; rhyaLuic m basaltic. Tertiary no - rin etlimen[ary rocks,e onglamerale, —,d- one, and claystane. Tertiary blollte granodl-rti,: local hornb3ende granvdiorit {Thgd). Tertiary -h;st, mig-11ir and granite, rup-senting the roof of a large stock. Tertiary and/or Cretaceous gran;tics forming small pl�tops_ Jurassic amphibonle. nclusions of green- -nisi w marble; lacal ondiernite lit,) and granodi—ite (.lga)- Tri—I basaltic olcanic r loaned In shallows mamne a v,ronr„cnt Late Galeozli, basal Lic and antlesitic meta- valGanogertic rocks, ocal meta -limestone (Pis)- Cretaceous argidile and graywac e, of a lh;ck deformed ill rbidite se uence, owgrade me amorphism Triassic metabasalt and slate, a in Urbed-d shallow ari..e sequence- Miscellaneous Map Symbols Scarp Slide Scar Buried Channel Trail �, Rock Contact 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unwealnered, Bxu ensalidated nedrock [', (:oEfuvfal tleposlSs `+l Landslide Cs - i 5nlifluction depasils (Frvten) Ff9 Granuiar alluvial ran FP rloodplain aeposila Fpt Terrau GFo outwasn deansfts GFe esker dnpoefLa GFk Isame depart: Gta Ab,aliun till Gtb-f nasal lili cr--) organic dePosiu L-f a n lr;ne, (frozen} L ae�strine Gta setllmencs e� r a amaaon uu L Lacustri— Gtb f deposis a i basal till (f'oeen} Soiifluction Cs-f depoelts (fro:en) Gtb-f Ve of till (rrate�j Cs-f solrnoodon depo,its crro�en} Gta ay.r ahl—t uu smin�ctlon Cs-f deposit. (waxen) Fpt er terra e sediments Cs-f solifw-unn (frozen) Bxu oveosits r aedraek Gtb-f Fr,aen baaal tin over'bed rack Ablation 00 Gta ealhered bedrock Colluvium a er C +BXa bedrock and bedrock Hxu exnosores L+BXw Weuuviurn o er athe or Bxw ld Ponrly OEi- dated bedrock .... ............. Bedrock Mapping Tv Tsa Tbgd Tsmg TKgr Jam (Jtr)(Jgd) }iv Pzv (Pls) Kag Tvs Units Abbreviated Tertiary yols..nic acks; shall— Tertiary na - arin sedimentary. ks;e Tertiary bioute local Tertiary schist, Tertiary and/or Jurassic a,aphibollte, i—i,_ basaltic t.1, Paleozoic Gasa '; c Cretaceous argihit. Tri—ir n tabasalt 1ea Descriptions n trysiyes, flows, -d roc vnglnmerate. sand- granodioriSe; hornblende g....diorit mig..Vtl and granite, representing the roof Cretaceous gra.itics forming sma11 Pluto.=, nclusions of green- schist S ma rbie; I.— metavolc an is corks forn,etl in shallow and andesit'rc m to votcanogenic ricks, and graywacke, of a thick deformed and sim interbetlded shallow Pyroc 1—v-; rhyoiitic co basaltic. a and claysrone, (Thgd)_ of a large stook. —diemite {dlr) and mart...nv room..[ local meta -I mes [one Wrb tlile sPgt,ence, anne seq enre. --di—IL. (Jgd ). {olsJ_ lowgrade m orphts,n Miscellaneous Map Symbols j y Scarp Slide Scar Buried Channel ��� Trail �./ Rock Contact r` 0 2)00 4000 FEET SCALE GFo Cntwash deposit: GFe raker doposiu GFk Kam, deposits Gta Ablatiep till Gtb-f 6.a.I till (fro ) O Organic dtpealts L-f ae =trine. (frozen) L ta, atrine Gto ..dimenta s, a r .hlati— till Larnatrin, Gtb-f deposits -I b.sa1 tTII (frozen) Cs-f S.M. don deposits (frozen) Gtb-f —r baaal till frozen) Cs-f 5o1iffurUOn dep..h. (frozen) Gta ever ablation till syfiRuctlen Cs-f degnaita (rroaen) Fpt er urra�e sediments CS-f SoF6—tinn d I,P-cts (frozen) Bxu bedrock Gtb-f Frozen basal till aver bedrock ablation tits to xu �n- eathered hedrcck Cuil a er betl—rnck and 45— +Bxu bedrock expos _C wealnytum over erect n Bxw +Bxw pyerfr �ansah- datetl bedmrk L Ir ALASKA POWER AUTHORITY tSUSITNA HYDROELECTRIC PROJECT SUSTASK 5.02 PHOTO INTERPRETATtON TERRAIN UNIT MAPS APRIL i981 0525()2 .r fj .WtsioN6. Tertiary v anic TerimrS no - rin cks;e Tertiary blot'ite Tertiary schist, T—liiary and/or Jurassic empM1rbolive, Tr assic basartis Laie V'aleomic r. s r Cretac uuus argiu: [e Triassic metabasalt Abbreviated ticks; shalin dimeiilarynro granod iorile: V cal migmatite and granite, [retaceoUs granrSics of grce»- nsdallmrs nd antlesi [ic meta- and gravwac ke, of a and s Descriptions onus, avid pv�r�ciastics: rate. sand- o e, anu cluystone_ nornblende granodinri[ (Thyd 1. r¢prescntrng Lhe roof of a large swck. forming small plulons, schist'3 n,a b e a Vandl formed r volcanoyenic rcc ks, thick deformetl r betltled shallow rhyo?rtic in asailtc, ndiernrte IJIrJ yrxnn � dior•le (J d1. marine envi ronmenl local meta -limestone Spls). orM1idite sequence, lougrade --ph, arine sequonce. Miscelloneaus Map Symbols Scarp J Slide Scar �` 1 Buried Channel �'Y` Trait Rock Contact 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name Unweathered, Bxu consolidated bedrock [; Colluvial deposits Cl antlslide Cs-f seiirinrtinn de�os¢a Ltra:en} Ffg Gran.iar aEi—W rap Fp e Eoadpla3n deposits Fpt Tereare GFo o two:n depoeita GFe esker dnppsTL GFk kame depoalta Gta Ablation till Gtb-f 6asa1 till (frnaen) O Organic deposits L-f ar zatrinea u en) L C-arus[fipe Gia sediments n r anlabon tillVe L La1—rine Gtb-f aepnelLe o basal till uraznn> SO 1..tion Cs-f deposits (f--) Gtb-f over basal li€I (fro en) CS-f SpEiliuchnn deposits crrp:en) Gta oar ablation ull SOEiPucliarl Cs-f deppsita co-naan) FPt errs e .eaim¢nt. Cs-f sahrwenan Bxa dJptasits (frozen} o bedrock Gtb-f broom basal tics -� over bedrock Ablation till to xu r up- M-d bedrock CUES Vlum o er [; bedrock and +BxuHxu bearak exposures Colluvium p C + BXW weathered over BxW poorly c soli - dated bedrock FCH CONTINUATION. SEE SHEET 14 Bedrock Rapping Tv Tsu Tbgd Tsmg TKgr Jam 61fr)(✓9d) Tv Pzv (P/S) Keg Tr vs Unrls ani(,ni�olite, aek,sinns Tria.ssie basaltic race Paleoxoir c,sa ary, Cretaceo,ls to oa Tri antic me sail i ertia y l�olcanir. `s Tertiary no ar�n ocks:e lerl,ar} oio e Tertiary schist, Tertiary and/orassic Abbrevlaled DesLrf lions p eC" n, J rmo-t, 6vP,v� lastics', d,menrrpn m kin e, a o1e• santl tlatstone_ pranodinrnc;t ;:al her nu e, a grlT r,od�er�te Irnpd 1. miymarne and `�`a a �e en tiny Ina root' nl pa Plarge cretaeeoe+ gra,,;tira m ing small pl atolls- t green- s .e m�role: ,cal v ,eca.�aca��o r��p en �hal and andes�nc meta- �nlc n�ye,nc r-cps, a„a arav�.a�ke, or a thick delnrmed slate, a �d ed n'3,anow yn �n= bile [o basaltic. slack. trondliemita ;atr, yranud�ur, le. 1a9d )' eoarrnl,ne Iecala mesa -limestone Ip7+). lurbidire �e4amnc e, lomgratle. m orpn, loa r,ne q ce. Miscellaneous Map Symbols J y / $Corp Slide Scor Buried Channel Trail Rock Contact 0 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unwaathcretl, BXu n naendated netlraek C r fluvial aapasita Cl Landslide Cs-f snrneaion depesits (rraxen> Ffg Granu3ar aEluvial ran Fp Fio,dplain deposits Fpt Terrace GFO out—h deposits GFe Esker ft-its GFk ame aepnslts GtU Ablation kill Gfb-f gasal till (rr—) 0 organic deposits L-f acnstrines (rrnxen} L ta��,o-ina Gta setlimencs o r ablatio„ tlilVe L a�psvina Gtb f tleposils o basal till it o:an} Cs-f senn�acion deposits (rrnxen) Gib-f er hasal till (tro en} Cs-f sarrl—tinn deposits (troxen) Gt0 aea a lakion r r,ll So lifluction Cs-f depa:its (frozen} Fat errace �Qelment: Cs-f serene uen 8XU oee'eita ctraxen} a bealnzk Gtb-f r oxen basal =ul Deer bearo�k R 47atian []il to Xu un- eam.rea bedrock Colluvium o er and +BXu bedrntk exposures +Bxw wealueium over naretl o Bxw poorly onsoh- dated bedrock Qbbrevioled l artiar� 1'nrca. �c fiche[ shanpwr Tertian, r,ori- Tertiary biome 7e�trary � s T crtrar�' and'or ]eras amnh,FnllLe, rass 5 .1Lic late nalenzo,c basaltic Creta ceou s ary'i kklLe Ln e, nall Descriptions i -r i, lin,.s. as: sedrmenlary r - --Lc,O rsrle r.nyionrer� p, e, ,nr. yl'dnedlorlte; r cal 17r rn gr'anur ende n 4iur r.. ry iTne -ma0 to and gran,te, represen;,ng the. real a us yranl[ics Inrmingosmall nlutune. r r green- �.npe a „erl,a eol IT:d s InP'raeul<n nal�allnw and andesltic meld- �pc noyenr� rnr N-s, and a graYu'acke., o lni[L, delormetl nd Sial eataa� xrterbedded shallow ��}'ollbc Lo besaitie. , a,stone. J _ o, a arse ,I k. l , raniunle IJgtl 1. nenmenl. aamela-nmesione nls 1. to vg a�tle m orc'phksm ar,ne =en ente_ Miscellaneous Map Symbols j Scorp r / Slide Scar Buried Channel r Trail ./ Rack Contact 0 2000 4000 FEET SCALE Gta Ab kation ill, Gtb-f laasal till (frozen) 0 orflanic deposlts L-f Lacascni— (rreze ) L ar str€ne Gta abe[i- till L Lacustrine depasltil p Gtb-€ na I till irrozan) sp Ifl i— CS f depesns uI Gib-f yer Hasa€ t€it {froEert) Cis-f So33fluc[ion deposits (frozen) Gta ye antatlen tiE€ r 5olifluciian Cs-f aepoana {rrozen) Fpt er terra�a sediments Cs-f sol i�etipn Bxu dVefnts (frozen) nedrorx Gtb-f 1-- nasai till -Bxu over bedra�k ablation ti€[ eathered bed—k er C_-+Bxu and 'r G1ILI bedrock exposures C Wolluy3um a er o Bxw ,Bxw eaihered poorly eenaall- dated hedrnck L I�[ ALASKA POWER AUTHORITY IllLlij SUSITNA HYDROELECTRIC PROJECT SUBTASK a-02 PHOTO INTERPRETATIO111 TERRAIN UNIT MAPS 1 � -11 APR11 1981 � emxc xo. arnereexr m corvsuuTwnfTs. mrc. reww* 052502 �P Bedrock Mapping Tv Tsu Tbgd Tsmg TKgr dam (dtrlfdgd) Tv Pzv (PIS) Kag Tvs Units Abbreviated 1 erllars volsa Ochs: ha{lownc Terl�ar5' "un- rin etlimenlary roc ks,u Tertiary nintle grand iorite; rat ncrtiary s isl, and Tertiary and/dr Jurassic amphiaplite, Triassic basahir Late Aaleozoic basaltic ary, Cretaceous 'EEile Triassic metabasa3t Descriptions p flows, antl p} oclasl onylomera[c, sand hornblentle granodiori{e ymatrle yranl[e, - representing the roof Cretaceous granllics ming small plu[ons. uz nn of green- schist's mar le: Ina reeta.olcanic rrrrhs formed hrl lnrr and an6es'iic m ta- olcanogenic rocks, and graysracke, pf a N deformed and slate, a inlerbedd cs: rhyolitic to basal tis, one, and ay sturre. (Thgd )_ of a large c{cck. ontl ernite 11[r) anal 1 sarnre envrror�nie�t. local meta-{irsestone lurb;diie sequence, ed shallow arine sequence. granadivr�{e (Jgd). (Pis), lowgrade m orph''sm. Miscellaneous Map Symbois Scar0pt^ f Slide Scar Buried Channel Trail ./ Rock Contact AV A 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unweathered, Bxu sd lidated bed—k C Calluvla! deposits cl Lands3ide Cs-f Soll(luction deposits (rrp�en) Ffg cranwer anwial (an Fp Floodplain aepp:ua Fpt Terra« GFo out—h d.pp I � GFe Esker dep-its GFk ame deppaits Gta Ablation till Gtb-f f3 s 1 till (fr.—) 0 Organic deposits L-f ar zstrines L acuatrine G ta e r Ve sediments blalion tpi L Lacustri" Gtb-f basal rill (frozen} Cs-f 5all(luctlon deposSt, (frozen) Gtb f over basal till freten) Cs-f Solirluction deposits ((roam} G to o e ab,at{pn r tiu spllnnptmn C s-f deposits (tr-e:a ) Fp tt er terror. �edimenta Cs-f seliun lion .V.'s its (frozen} Bxu bedrock Gtb-f Froxun basal till —�xu aver hedrack Ablation till xU eatnered bedrock '91.—ut Colluvium a bedrock and er Bxu b edrpck expos Ce Colluvium o +Bxw B xis id poorly s pier p—ly c tlaled bedrock Abbrevioled Ter t'ia ry 5nlcanic arks, shallow Terliar� non- ones ed lmentar'y rocks; Tert-y heetite granodrarite; local Tertiary schist, miyma[iie Tertiary andlor Jurass lc—phibukite. Triassic basa,[ic I. ate Paleozoic basaltic [relacevuI argirlile 'Triassic metabasalt Descriptions n [r......, lro,rs, o glomerate, sar,tl- stone, vrnblende granodlorit. and granite, rr enling the ...f pa Cretaceous granitics forminn smell pluwns. nclusions of preen- schist A marble: EocaE melavo1—m rocks formed in sl,al,ow and andesi[ic mesa- Voiranogenir racks, and graywacke, of a thick deformed and stale, a r er Ledded shallow nd pyroc,rsCics; rhyolilic [ uasalEle, and eia,slene. (Thgd). of., stock. argc truedlemi [e (.[tr) and anne enm ronment _ local meta -limestone tvrbitlile sequence, ar,ne sequence. granediorrte (jgd}. l Pls). 3owgrode m norphism MisceElanaous Map Symbols Scarp F ^'`f Slide Scar Buried Channel Trail r r� Rack Contact 0 2000 4000 FEET SCALE F__ Terrain Terrain Unit Unit Symbol Name Unweathered, Bxu [nnanktlat.tl bedrock C Coliuvial deposits cl Landslide CS-f Selifluc[fan deposits (irozen} Ff9 Granular alluvial far, FP Fluadplain deposits Fpt Terra.. GFo nut—h deposits GFe Esker dnpvsns GFk Kam. depnsTts Gta Ablmlvn till Gtb-f nasal tin (frnaen) organic deposits L-f to nstrines uraeen) L a[va ine Gta s Ve r blaedaIii- tion till i L La cus trine Gtb-f b ..I tiill �f-..) CS-f Sanfluctlon deposft5 (frozen) Gtb-f v r basal till (frozen) CS-f 5o1ifluctit. deposit: (frnaen) Gto r ov. aW.U.n tin SWIM-tion C s-f deposits (f ozen) Fpt :ea ne esaa Cs-f s�ehn-tien Bxu (frk� nepnnb. beard k Gtb-f F—ri basal tin —S11U aver bedrotk Ablation till Bxu eatheretl bedrock -�t Colluvlum ov bedrock and er B x u bedr-1, exposures r, — +3xw Wn�lituvium over hered ar B xw d-T-d b d—k dated bedrock Bedrock Mapping ry rsu rbgd Tsmg TKgr Jam ()fr)(Jgd) Tv Pzv (Pis) Kag kvs Units Ter[idry Volcanic Tertiary no - art � Tertiary hiou[e Tertiary schist, Tertiary antllor J4ras$iC amphiboli[e, Triassir basaltic Late Paleoze�� basaltic [reyceo�s argilliie Triassic m tabasall ea Abbreviated acks; sha3low etli enlaryt rocks:e gran diorite; lacaf migmatite and granite. [retarequs gran itirs nclusions oT green- volcanic racks meta- and graywacke, o[ i antl slate, Descriptions ntrUsives, flows, dnd nyrociastics; onplomerate, sand- stone, and ciaystone. hornblende granodie Nte (Thgd). representing the roof of a large farming small plutons, schist & marble; local ro.., in shallow volcanogenlcc rocks. ti-1, deformed sequence, in —bedded shaEko�• ai ins sequence. rhvnaut m basaltir. stock. endjemile SJ[r) antl grannemrl[e fJgd). ones environment. ocal meia-limesta a E9, bidite io�rgraae m nrphism_ Miscellaneous Map Symbols Scarp Slide Scar Buried Channel Trail +y✓ /'f Rock Contact 0 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unwaatheree, Bxu en-lidatGd bedrock C couuvial deposltt Cl Landsllde Cs`f S:iTfluctlon deposits (frozen) Ff9 Granular allwlal ran Fp Flo¢dplaFn dapnsit: Fpt Terta¢e GFo outwash dep9sits GFe Esker deposits GFk Kam. depvsrt, Gta Ablitlon tilt Gib-f nasal tfii (frozen) 0 Organic deposits L-f Laeu strives ara=en) L �a��strine Gta sediments a r ablation y® Lill L La¢nstrine Gtbf dep-U er 6azm tiff (frozen) Cs-f Salifluction deposits (frozen) Gtb-f iver basal till frbten) Cs-f snstfwntion daps:it: irr9cen) Gto y­ ablatien till seiifluatian C S-f deposits (freaen) Fpt zecimeisa¢e C s-f snunn�uon Bxu oepasits (f-0 had e r fork G Fr n hasal till �tb-f DAU aver bedrock Ablation till 02 Bxu ver un- weatneraa betlroek Celluvlum o er [[,� b.and ilx+ B x u ❑❑7)CCUU bedrock expgsu - _ weakavium or r It,ered a Bxw Bxw pnnrry - dated bedroc.dr-k SEE Bedrock Mopping Tv Tsu Tbgd Tsmg Tlfgr Jam 0/009d! TV Pzv (PIs) Kag TVs Units eriiary Von.anic Ternary roe- re Tertrar} b Ternary schist, Tertiary and/or amphlbelite, Triassic basal lrc Late Paleozoic G-sa'i Cretaceous argib:te Triassic m tabasalt ea z� Abbreviated anon' edrmentary racks, granodiurite; local ymati to and granite, Cretaceous granitirs nclue cans of green- meta nlranic r nd a and grayrtacke, of a d slate, ru}srves, fiuwz. ongiomsrate, sand- strnre, nornbirnde granodioml a esenlrng the roof of pa forming sma l pl.atons. schist 8 marble: ! a and formed 1 sballuv�a volcanugenicr rmcks, th del ormed rn terheriaed shallow Des-ipflans and pvror:la st ics; r»yul'ibc to basaltic. and r t one (ch9d), large stock- e e (atr) grar uldiunte iJgd ]. marine envi renment. loca3 meta-I�mesione [PIsJ_ carpi dire seQuence, loti,grade m tamarphlsm ra, ine sequence. Misrellaneous Map Symbols Scarp Slide Scar h` ` J !ems' Buried Chonnei Trail Rack Contact 0 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unwea,r,eree, Bxu solidaled bedrock C Calluvlal deposits cl Landslide CS-f snrsm�san deposres (rrozen) Ffg Granular alluyldl oar, Fp Floodplain deposits Fpt Terrace GFo out—h deposits GFe Esker deposits GFk Kame depo:its Gto Ablation till Gtb-f a-1 till (froaen) Cl OrOanir deposits L-f Lar�strinaa [<roeeny L Lacustrine pa sediments wer uu ardatinn L Laeustrenc deposits o Gpb-f basal tiu ir�oten) Cs-f sebfineuen depmEls (frozen) Gtb-f — bal till (asfrozen) Solifl action C S-f le,vsTtl (frozen) Gto a e abla6cn mIr Solifiuctian C S-f deposes (fre�en7 Fpt e� terrace sedlmen Ys CS-f salifwctien B](ll sbetlrack en) over Gtb-f Fro:en basal tW —� over bedrock Ablation till Pweathered bedrock Colluvium o bed—k arld er +Bxu bedrock exposures C weat - a er hcred T o BXW +BXW poorly cor soll- dated bedreck L J RRjFrF�n ALASKA POWER AUTHORITY �Illu SLISIT14A HYDROELECTRIC PROJECT SUBTA5K 6-a2 PHOTO INTERPRETATION TERRAIN UNIT MAPS APRIL 18811 sere[ ooi Re052502 scan l4 DATE I Nn, REVISIONS. CH. Arv_ All Terrain Terrain Unit Unit Symbol Name unweathered, Bxa consoraaterl bedrock [, Colluvlal deposits C1 Lands7lde Cs-f s9nfw Lion deposits (frozen} Granular a€luvial Ffg fan Floodplain FP depnsha Fpt Terra.. GFo ontwa,h aepasita GFe Esker depgeils GFk mama depcvts Gta Ablation till Gtb-f Basal un (frozen) 0 organic deposits L-f Lacustrines (Iroeen ) L ar strtne sedlmenn a r Gt❑ abla Gon Lkl Ve L La�nstrine deQits Gtb-f basal Uilo(F+'ozen) snllfluctian Cs-f deposits (f—o ) Gtb-f .er 6-1 trll �f--) saltfluctlon Cs-f deposits (t-1) Gto ,.e aalaugn =ill r selifluctien C s-f dapnaFla �roaen] F P taim�n .aee Cs f snlirmaion deposits if--) BXu ov r bedrock Gtb-f Frozen basal till over hedrock Ablation S'dE un- Xu weathered bedrock CoIIuVEum qv Cbedrock and er +Bxa hedrock �o l�.11ll ekpas Col7uvium av C+Bxw weame o er r Bxw poor y nsnn- dated bedrock Be dro ck "Opp/ng Tv Tsu Tbgd Tsmg TKgr '/GMor)(Jgd) Tv Pzv (Pts) Kay TVs Units Tertiary Volcanic Teriiarl' non Tin Tertiary biatite Tertiary schist, Tertiary artd/or Jurassic amphilroliSe, Triassic ba�alSic to Paleozoic hasalSir: Cretacequs argillite Triassic metahasalt Abbreviated grks; shallow edlmenlary ocks;e granvdiorile; local migmatlte and granite, Cretaceous granillcs ons of green- me[avglcanlr rocks and anues itic mesa- and gray, —Me, of a .nd state, a intrusives, flows, ortglomerale. sand- hornblende granotl4orite re esenling the roof forming small plutons. schist 6 marble; Incal Tornretl in shallow volcancgenir rocks, think deformed erbedaed shall�,v Descriptions ne pyroclastics; one, and ciayslane. (Thgd). of pa large stock, gntllemite tulrl and arise envrro enl. nm amne rhygli iic to basaltic, cal n a -limestone urbed;te sequence, sequence. granodrgrrte {.fgtl j, 4PIs). lowyrade mefanwrptrism. Miscellaneous Map Symbols Scarp f� T `r Slide Scar �4 Buried Channel '�� Trail / Rock Contact FOR CANTIWATM SEE SHEET 7' FOR CoNTHWATION, SEE SHEET 8 s: Terrain Terrain Unit Unit Symbol Name U.—th—d, -n, t.d 1,0—k C,irwl,l d,p,,Tt, 'Ib f . . . . ........ C &w j 1 RA S.ETfl—ti— CS-f Ffg FI-dpl.i. p Fpt Sxrt w JF- GFo Clut—h d,,it, U GFe Esker d�.��Tts GFk Gia WWI, Q H.-I till Cf--) Gtb-f 0 L-f L Gia -W�V— till L Lm.LH . deposits —Ib-- f 5 lifl—ti.. CS-f J�P-lt, M.—) Glb-f basal 1111 Cs-f Sd'p-lt. (f--) Gta G S-f deposits (fm-n) Fpt CS-f -ffx —u Gfb-f F, — bozo! till FX —u ��,J—k u —t6—d bedrock —li—i— C ..d Sx—u+ Bxu -t G + -e—xw Bxw P--'IV --li- d.l.d bedrock Bedrock L Mapping TV T's u 7-smg Tffq r Jam (11r)('1gd) Pz v (P/s) Kuq TVs ALASKA POWER AUTHORITY 4Vnits 1.,v V�I—k Tertiary SUSITINA HYDROELECTRIC PROJECT ...... --i, —phlb,lit, T,—,,i� b—ltl� L�I� P.I-- b-1- Cretaceous —'WNt. T,i—i, 0 2000 4000 FEET Abbreviated I—W- —­.­ f green- 'auk and —d --iti, -.k,- ,d g,,y,,,,k,, f —d —1, SCALE . f. 1— schist & i I Formed m ...... 1� -,k,, tn"K IhIJ11, SUBTASK B.C32 Descrip lons ,d py—i-ii, 11—, .,d (T�gd (J,,l local —.-Ii—w— �Y.Iiti� t. PHOTO INTrERPRETATION Miscellaneous Map Symbols Scarp Slide Scar Buried Channel Trail Rock Contact TERRAIN UNIT MAPS O ER IL 19.1 DA- WI RM3.0N.. 1�11. A�. AM Landslide ocks; shallow n[rus;ves, flouts, angiomerate, sand- hornblende granadiorl to flog ine woof Forming snrarl erbedued H bedrock Mapping Tv Tsu Tbgd Tsmg TKgr Jam (Jtr)(Jgd) dv Pzv (Pts) Kag dvs Units Tertiary Volcanic Tertiary n - Ter Uary bl.iite Tertiary scht.1, Tertiary and/ar lrna 1, basaltic iQ Paleox.lc u li re Ctaceous ..ginite Triic melabasa It ass Abbreviated or ks; snaliow etlrmentaryn r.cksne 9ranadEorite; I cal rnigmatlte and granite, Cretaceous gr.nitins nclusions of green- met avolcan lc rocks and andesitic m and graywacke, of a and slate, a Des Lrtptioas niruxives, fkows, and .nglemerate, ssr}d- lane, antl rlayslone. Hornblende granotliorit iThgd), representing the roof of a large stack. forming Small pi.t—, schist & ma hle; heal trandlemite (Jtr) and !armed in shallow v.lc... genic rocks, local meta-hmesto.e thick del.rmed urbidite seequence, irrterbetlded shallow arine sequence. pyrociasiios; rhyolitic to hasallic. g....di.rite {J d), 9 mamma environment_ (Pis). lawgrade m .rphism Miscellaneous Map Symbols j I<GV J Ypy Scarp 1_� Slide Scar Buried Channel Trail Rock Contact %q 0 2000 4000 FFFT SCALE Terrain Terrain Unit Unit Symbol Name Unweathered, Bxu .lidated betlrock G Co[luv 111 deposl[s Cl Landslide Cs-f 5.lifl..ti.n depnsns (rr.�en) Ffg Granular aEluvEal ran FP rbadAiain depa,ly Fpt Terrace GFo Cutwaah deposit, GFe Esker dep.,us GFk Kam. dep.slts Gta Ab]atien Lill Gtb-f nasal Yin (fr..en) oreanin d�posly L-f anuatrinee L Lacuatrin. G ta sediments o r blaEion d31 ve L L.custri.e Gtb-f depo,it, basal tin (froxen) C$"f Son flJCYion deposits (frozen) Gib-f o,.er basal till proxen) Cs-f 5.lifl it,l (f deposit, ro:e.) Gto eve ablation r ON C s-f SohflucI— d,,its (frexen) FP t arcane :ealmenta Cs-f s.lifl—l.n Bxu eepoeit, (men) a„ bedrock G tb-f Frozen basal tin xu 9�er bedro�x AbIWV till Bxu weathered betlr.ck Colluvium o er broan edck d ' �C +BKa >S C7U bedrock .xpsvres �_+BKW Colluvium o weathered .rer Bxw p..rly m l!- dated bedrock L -11 Bedrock Mapping Tv Tsu Tbgd Tsmg TKgr Jam (Jtr)(Jgd) kv Pr (P/S) Kag Fvs Units Abbreviated Tertiary VOlraniC ocks; shakiow Tertiary no - r'rn edime iary[tr caks;e Tertiary Motile iocal Tertiary schist. Tertiary and/or Jurassic amphibakite, Trba iassic saltic Lai- Pamozoic basaltic Cretareous ar lc mgillite Tri ass tabasa It ea inl rusives, Tlows, onglomerate, sand- granod'rorite; hornblende granatliortte migmatlie and granite, representing the roof Cretaceous granitics forming sma it plutons. nrlusl—it of green- schist 5 marble; I, —Lav�lranic r s formed and a esitic meta- rucks, and graywacke, oI a thick tletormed and, rote rbetlded shallow Descriptions and pyroclasti"; one, a.d ci aystune. (Thgd), of a large stock. ondlemi[e (Jtr} d an In shaVlowvoicanogenlc amne envrronmen[. local me[a-l;mesione to hid;te seduenre, ar,ne seq enre_ rhyotili[ la basaltic. raned�o�lte (J d 9 9 ). IPis ), lowgrade --phi— Miscellaneous Map Symbols f' Scarp Slide -:0 -"—� Scar Buried Channel Trail Rock Contact --// AV Is 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name unweathered, Bxu solidaled bedrock C cenoyial deposits Cl Landslide Cs-f Solifluctien tlepoart: (fill:ens Ffg Granular af—W ran FR Fmdplain depos(tii Fpt Terrace GFo outwash depoarts GFe esker deposits GFk Kame Qepasirs Gta Ablagon tin Gtb-f Basal till (frnaen) D Organic deposits L-f Lai strines (frozen> L Lacvstrine Gta sediments Dyer ahiiiLl— till L Laooslrine Gtb-f deposits basal tin (i�o:en) n Ls-f Solifluction deposits (Truce„} Gtb-f er base! till �fra�en) Cs-f So kfluctian deposits (aroeen) Gta ove aalation r t;a sonfweteon CS-f deposits (frozen) FRt erra�e ,ea€manta CS-f Soll Fluctian Bxu ov a sits �fnozert) r bed ck Gtb-f Traaen basal till over betlrack Ablalion till Gta aver nn- cornered bedrock Celluvium o er C bedrock and �%U +BXU bedrock expvsores C COEEuvium o e Bxw +Bxw wear ered poorEy consoli- datetl bedrock Bedrock Mapping Tv rsu Tbgd Tsmg TKgr Jom ( fopgd! kv Pzv (P/s) Kog TVs Units Tertiary Volcanic Tertian no Tertiary biatila Tertiary schist, Tertiary and/or rassic a,nphiholite. Triassic basalllc tat. Paleo+— basaltic Cretaceous ar giVkite Triassic m tahasalt ea Abbreviated ocks; shallow edim.ntarynrocaks;s yranotlior'i le; local nipmalite and granite. Cretareous gra nilics elusions of green- melavulcanic rocks meta- and gral'racke, of a and slate, intrusives, (lotus, ongiumerate, sand- hornblende granudiorile representing the rool farming small pill tons. ,his&marble; local m.d �� sallow volcano3enicc rock, thick dclormed in lerbedded shallow Descriptions and pyroclaslics; stone, and rlayslone. (Thgd). of a large slot k. nndjeniite € Irl and environment. local meta -limestone urbidite s e seq nee. rhrolitlr to dasaitir, g—d..H,t (Jgd)_ yPK). lomgredc m ..ph-, Miscellaneous Map Symbols % f Scarp " Slide Scar Channel F Buried ; Trail ! Rock Contact AFA 0 2000 4000 FEET scnLe i Terrain Terrain Unit Unii Symbol Name unweathered, Bxu a nsolid.t.d bedrock C �alldvlal deposi o Cl 4aresiid. Cs-f Solifluction deposits (troielt} Ffg Granular alluvial tan FP FloodplAn dep—t. Fpt Terrace GFo Ontwash deposits GFe Esker dnpos]is GFk Kam. deports G1a Ablatlon till Gtb-f Basal till (trex.n) 0 Organic deposits teens[rm.s L-f (rro=en) L rarnstrine Gia Ve seen dimts o r ablation tM L tanaarina Gtb-f deposits bawl till ff- ) C S-f Soiifluctlon deposits {irox en) Gtb-f .... basal t€B cfraxen) Cs-f s.P-it mn deposits (rro..n) Gta .ver ablation till C s-f $�Iifl-ties deposits (frozen) FPt e...... zea Cs-f sn€nwamn Bxu oeeer[s ;frozen) v r Gedrxk Gtb-f Frezen basal [III over bedrock Ablation tilt xU Wvear bn- a thered bedreck ium o er beddrock and bnr -�'FBxu bedrock exposures r +BXW _SL_. a Caaluvium a er thercetl o Bxw poorly :eitr- dated bedrock Bedrock Mapping Tv Tsu Tbgd Tsmg TKgr Jom (J1rX1gd) kv Pzv (P/s) Kag F, vs Units Ter;iary volcanic Tertiary no - arin Tertiary biotite Tertiary schist, Tertiary —11— Jurassic amphibolite, sa Tli-IIL bah Ec Lale Paleozoic basaltic Cretaeeous argillite Triassic m xabasalx ea Abbreviated ocks; shaElow etlimentaryn ocks;e granodivrile; 3ocai mignullte and granite, Cretaceous granitics nclusions of green- melavolcanic Focks and andesitic meta- and graywacke, of a and slate, Descriptions in[rusives, haws, and raclastics; onglomerate, sand- stone, and hornbl-n J- grariu:Eiorite (Thgd). re es inp the mar a largo ' fore, Eng sma11 pE�tons. —11isl & marble; E... I form-d in sballc,w r vaEcanagenic ocks, Ihick tleformed - -'beddd eshaElow P rhyol:tic m hasaltlr, claysione_ of stock, ondj-mite Wirt and granodiarite (1qd ). arrne envrrtnvnent. local meta-Ilmestvno {p!s]. tl,,hW3te segoenoe, owgrade metamorphism anne sequence. Miscellaneous Map Symbols j ] Scarp Slide Scar Buried Channel 755, Trail .rJ Rock Contaci 0 2000 4000 FEET SCALE Terrain Terrain Unit Unit Symbol Name ��weathered, Bxu solidated bedrock C COEEUVEaI depesi[s Cl tandshde Cs-f snrnuremn depos]ts (frozen) Ffg Granular a334V3a1 ran FP Freodplain deposts Fpt Terraee GFo o4twash aepe,;t. GFe Esker depasita GFk xame depart. Gin Ablation till Gtb-f nasal nrr en} Q OrcJan,c deposits L-f L... —1nas (frozen) L La[U5iY1ne Gta sedimentl*11, em.tion till L Latnstrina Gtb-f deposits over basal kill (frozen) C s-f Sciirlurt;ed deposits (frozen} Gtb-f v r basal till (r .—) Cs-f S.ff I ction depa.its (rro­n) Gta e e ablaunn r tili Solilluctivd C s-f aepn:it, (rrnaen) FPf .r t.rr.ee sediments Cs-f snlin4 unn Bxu deposits (frozen) ., bedror¢ Gtb-f Frozen basal till over bedrock Ablation till Pweathered bedrock Collcrvium o-r �Arrr��^ u + B x u ��o AAAl11JJJ bedrock and bedrock exposures there .-h om over d or —Cy Bxw +Bxw P—ly rnnsnli- dated bedrock Terrain Terrain Unit Unit Symbol Name unweathered, Bxu n„related bedrock G alluvial deposits Cl Landslide C,5-� Snlifluclion depesi. (fr.-.) Ffg f,an.3ar ,11-al FEoodpla;n FP deposits FPt rarr­ GFo outwash dep,elt, GFe Esker d posit, GFk Ham. deposits Gin Ablation till Gtb-f eaaal ull (rr,zen) 0 Organic deposits L-f L-un ines (frozen) L ae�etrme sediments , r G1a ahlan,n tiuVe L tae,s� dep,sft, Gtb-f basal :il1 l (froxen) s,hn aian G5' f dep,sils (frozen) Gib-f er basal till (frox-0 S,Ilflucfi,n Cs-f dep,srcs (f ozen} Gta ,ve ablation till „ SMIR—Hon C5-f di, oM. (frozen) Fpt sediment,er terraee Cs-f sa rluni,n d 6xu ep.. its (frozen} ,v bedrock G�tb-f F-X basal till Rxu over bedrock oblation tiff t eatheredd hedr,ck C,ruvium , s U +Bxu b d— and er exposures C.4T.m er e eathered ov C Bxw +Bxw poorly � snil- dated bedrock FOR CONTINUATION SEE SHEET 21 Terrain Terrain Unit Unit Symbol Name a -� unweameree, Bxu --lid c P Y ri hedrotk C.,11—iai deposits CI Landshtle �, CS-f �nrw=P°n deposits {frown) Ffq Granular alluvial ran Fl—ciplain p deposits Fpt rerraca GFo OW-1, J.P-its r.. GFe ker dnpnslte GFk tram. depaeit. Gta Ablation till Gfb-f Basai till (frown) O Organic deposits L-f a=Hstrine5 (freaen} L G1❑ Laeustrine sediments r attar�nn till L Gib-f Lacustrin. b a.1'l (fro=.n} Cs-f sa nflurtlnn depaslts cfro=en) Gib-f ver nasal tin (trozen} Cs-f sallfluctk— deposits (f ozen} - Gfa OVef- abiahon t331 rti C5-f snunn°unn depoerte (fra.en7 Fpt er t.rra<e :edimenee CS-f salifluctivn Bxu deef sits (frozen} n b.d rwek Gtb-f Fro . ba.al till over bedrock -F xa8113 Ablation tk t weathered bedrock Colluvium o 6edroek antler ,.. G +Uxu bedrock exposures +Bxw �ouuvivm rv�er eatnerc rto - Bxw poorly soll- :ya: � dated bedrech I Bedrock L Mopping TY Tsu Tbgd Tsmg TKgr Jom (Llk)(,/gd) TV Unils F-9116 AbbreviuMd Tertiary vaman c °Lks• snanew rert,ary non" nn sed mentary vcks,e r°rt,ary biome Bran°dlerite, local Ternary scb sc, Tertiary andror .lurassic amohibabte, ,assic basaltic FOR CONTINUATION SEE SHEET Ig 0 2D00 40DD FEET DescrrplionS flows, endnpvr¢[lassez; anglomera Se, sand °I hornblende gr... d,orde m9matile and grante, representing the roof C—ale =a Vra tTt forming small plu;9ns. ,cwei°ns °r gram schist 3 marble; local rvela of a ,e r cks shallow SCALE 6U6TABK O.OB n,yelirc to nasarcc. e, ana clayslnne. (rr,gm. m a lar9. ete=k_ °nn;emit. .ltrl nd l a mine en ronment, granodiorim cagdi. PIv (P/5) KOg T{VS PHOTO INTERPREt ATION Miscellaneous Map Symbols / Scarp "'� Slide Scar � safe Paievzv�c basaltic Cretaceous argillite Triassic meiabasa3t TERRAIN UNIT MAPS Buried Channel Trail -'� Rock Contact /`-� d a °e"" a- a"° gra°'°a-- n' a and elate, a nose, rocNs, locale me[a�hmestone thick a med t�rnidne9eegnenee, interbedded shallow ar�ne setivanee. P AUGUST 190I t Pls t- mvgrade m Orphism, rhxtu.ry T aw�G n � " PATE IJP. pEVISIPNS CH. APP. PPP. cx Qszsaz 2'1 n Bedrock Mapping Tv Tsu Tbgd Tsmg TKgr Jam 0009d) Tv Pzv (P/s) Kag Fvs Units Abbreviated Tertiary Volcanic Tertiary n.n-marine ocks; shallow sedimentary rocks; Tertiary biotite diorite; fetal Tertiary schist, Tertiary and/or Jnrasiic amphiboli te, migmallte Triassic basaltic Lale Paleozoic basa : c Cretare.us m—basalt Description intruslves, flows, onglomera[e, sand- and v-; gran. hornblende granodlorlf (Thgd). and granite, Cretaceous granlbcs n4usl.ns .f green- representing the roof fanning small pill Sons. schist & ma ble; local of a large (Jtr) meta,nlrank rock and antlesitic meta- a.d graYr�acke, of a and stale, a formed in shallows valcanogenic rc,-ks, lM1ice deformed �, , e.tled shaVfow pyrocla e , and oEayst.ne. rhyolitic to basaltic. sm¢R. trondicmite and grdnediorile (Jgtl). eeanne onv ,onmeni- kcal meta---t—, urbidite sequence, marne se�uersce. (pis}_ awgrade meta arphism Miscellaneous Map Symbols] j Scarp Slide Scar K�F Buried Channel I TrcR Rack Contact 0 2000 4000 FEET SCALE mew Terrain Terrain Unit Unit Symbol Name unweathered, Bxu s.rdated bedrock C C.N—Jal tleposi[s Cl Landsllde Cs-f sabnaatian deposits (frozen) Ff9 Granulor AILVIIi ran Fp Fl--plain depbslts Fpt Terrace GFo outwaah dep-lt, GFe a ek.r deposit, GFk A— deposit: Gta Ablatiert till Gtb-€ nasal uu (fr.-.) Organic deposits L-f Lae=strines (rro en> L arnsirine Gta aedimenta o r ablation tillVe L Lan striae Gtb-f basall t[il(fro zen} 5.liflurtian t C $'I tlepasits (frpten} Gtb-f basal till (fro en) Sai u[tl.n Cs-f e.eita (r,-e=en} dp Gta r ove ablation till sollfloctit. C S-f deposits (f.—!l Fp t sed �entsane Cs-f 5.lifl-tien Bxu oee'eita (o-own} bedreek Gtb-€ Fro en basal till _� oAU aver bedrock Ablation Call fa xu weatheretl hedrock c.11uviam oer � betlrk a.,d Txu +Bxu bedroacck e Kposures Collviurn a e r C +BxW wedt hexed Bxw poorly m a.11- daled bedrock APPENDIX K RESERVOIR GEOLOGY APPENDIX K RESERVOIR SLOPE STABILITY 1 - INTRODUCTION 1.1 - General Impounding of the Susitna River valley and its tributaries will influ- ence the slope stability of both the Devil Canyon and Watana Reser- voirs. Currently on the slopes above river elevation there is evidence of shallow landslides and discontinuous permafrost. Impounding of water will result in raising the groundwater table and thawing the per- mafrost which will likely cause slope instability and failures within certain areas of the reservoirs. Because of the complexity and uncertainties of analyzing slope stabili- ties in a thawing permafrost environment, a "best estimate" has been made in this study to identify those areas in the reservoir that may be subject to future beaching, erosion, and slope failures. The following sections discuss slope stability as it relates to the Watana and Devil Canyon reservoirs. Section 2 briefly discusses the type and causes for slope instability while Section 3 and 4 evaluate the type of instability that may occur after impoundment at Watana and Devil Canyon. The last two sections provide a summary and conclusions with recommendations. 2 - TYPES AND CAUSES OF SLOPE INSTABILITY 2.1 - General Shoreline erosions will occur as a result of two geologic process: (1) beaching and (2) mass movements. The types of mass movement encoun- tered in a permafrost terrain and which are pertinent to this study are described below (4,5,12): (a) Bimodal Flow - A slide that consists of a steep headwall contain- ing ice or ice -rich sediment, which retreats in a retrogressive fashion through melting forming a debris flow which slides down the face of the headwall to its base. (b) Block Slide - Movement of a large block that has moved out and down with varying degrees of back tilting, most often along a pre- existing plane of weakness such as bedding, joints, and faults. (c) Flows - A broad type of movement that exhibits the characteristics of a viscous fluid in its downslope motion. ., ACBfi� (d) Multiple Regressive Flow - Forms a series of arcuate, concave downslope ridges as it retains some portion of the prefailure relief. (e) Multiple Retrogressive Flow/Slide - Series of arcuate blocks con- cave towards the toe that step backward higher and higher towards the headwall. (f) Rotational Slides - A landslide in which shearing takes place on a well defined, curved shear surface, concave upward in cross sec- tion, producing a backward rotation in the displaced mass. (g) Skin Flows - The detachment mineral soil with subsequent face, usually indicative of permafrost. of a thin veneer of vegetation and movement over a planar, inclined sur- thawing fine-grained overburden over (h) Slides - Landslides exhibiting a more coherent displacement; a greater appearance of rigid -body motion. (i) Solifluction Flow - Ground movements restricted to the active lay- er and generally requires fine-grained soils caused by melting and saturated soils. Aside from the formation of beaches due to erosion, instability along the reservoir slopes can result from two principal causes: a change in the groundwater regime and the thawing of permafrost. Beach erosion can give rise to general instability through the sloughing or failure of an oversteepened backslope, thereby enlarging the beach area. 2.2 - Chances in Groundwater Regime As a reservoir fills, the groundwater table in the adjacent slope also rises as shown in Figure 2.1. This may result in a previously stable slope above the groundwater table to become unstable due to increased pore pressures and seepage acting on the slope. The slope shown in Figure 2.1, whether in soil or rock, is less stable after filling than it was prior to the existence of the reservoir. This is not to say that this slope will necessarily fail, since failure is dependent on the strength parameters of the soil or the rock. Rapid drawdown of a reservoir may also result in increased instability of susceptible slopes. 2.3 - Thawing of Permafrost The instability of thawing slopes in permafrost is addressed by McRoberts and Morgenstern (4). They indicate that the characteristic features of solifluction slopes, skin flows and the lobes of bimodul flows are caused by instability on low angle slopes resulting from thawing of permafrost. Mobility is often substantial and rapid as the movements are generally distributed throughout the mass. 2.4 - Stability ➢uring Earthquakes There are certain conditions which can exist after reservoir filling which will cause slides to occur during earthquakes. This section will address only those situations which may exist after reservoir filling in which slopes are more susceptible to sliding under earthquake load- ing than they are in their present condition. Submerged slopes in granular materials, particularly uniform fine sands, may be susceptible to liquefaction during earthquakes. This is one example where a small slide could occur below the reservoir level. In addition, areas above the reservoir rim in which the groundwater table has re-established itself could have a greater potential for sliding during an earthquake due to the increased pore water pres- sures. Thawing permafrost could generate excess pore pressures in some soils. In cases where this situation exists in liquefiable soils, small slides on flat lying slopes could occur. The existence of fine-grained sands, coarse silts and other liquefaction susceptible material is not exten- sive in the reservoir areas. Therefore, it is considered that the ex- tent of failures due to liquefaction during earthquakes will be small and primarily limited to areas of permafrost thaw. Some slides could occur above the reservoir level in previously unfrozen soils due to the earthquake shaking. 2.5 - Slope Stability Models for Watana and Devil Canyon Reservoirs Following a detailed evaluation of the Watana and Devil Canyon reser- voir geology, four general slope stability models were defined for this study. These models are shown in Figures 2.2 and 2.3 and consist of several types of beaching, flows and slides that could occur in the reservoir during and after impoundment. Based on aerial photo inter- pretation and limited field reconnaissance, potentially unstable slopes in the reservoir were classified by one or more of these models as to the type of failure that may occur in specific areas. In addition to identifying potential slope instability models around the reservoir, attempts were made to delineate areas of existing slope failures, and permafrost regions. These maps are shown in Figures 2.4 through 2.28. Table K.1 provides a summary of soil types as they relate to the type of slope instability. As stated above, these maps have been construct- ed using photo interpretation and limited field reconnaissance and are intended to be preliminary and subject to verification in subsequent studies. 3 - DEVIL CANYON RESERVOIR 3.1 - Surficial and Bedrock Geology The topography in and around the Devil Canyon reservoir is bedrock con- trolled. Overburden is thin to absent, except in the upper reaches of the proposed reservoir where alluvial deposits cover the valley floor. A large intrusive plutonic body composed predominantly of biotite gran- odiorite with local areas of quartz diorite and diorite, underlies most of the reservoir and adjacent slopes. The rock is light gray to pink, medium grained and composed of quartz, feldspar, biotite and horn- blende. The most common mafic mineral is biotite. Where weathered, the rock has a light yellow -gray or pinkish yellow -gray color, except where it is highly oxidized and iron stained. The granodiorite is gen- erally massive, competent, and hard with the exception of the rock ex- posed on the upland north of the Susitna River where the biotite grano- diorite has been badly decomposed as a result of mechanical weather- ing. The other principal rock types in the reservoir area are the argillite and graywacke, which are exposed at the Devil Canyon damsite. The ar- gillite has been intruded by the massive granodiorite and as a result, large isolated roof pendants of argillite and graywacke are found locally throughout the reservior and surrounding areas. The argillite/ graywacke varies locally to a phyllite of low metamorphic grade, with possible isolated schist outcrops. The rock has been isoclinally folded into steeply dipping structures which generally strike northeast -southwest. The contact between the argillite and the biotite granodiorite crosses the Susitna River just upstream of the Devil Canyon damsite. It is non -conformable and is characterized by an aphanitic texture with a wide chilled zone. The trend of the contact is roughly northeast -southwest where it crosses the river. Several large outcrops of the argillite completely sur- rounded by the biotite granodiorite are found within the Devil Creek area. A general discussion of the regional geology is presented in Section 4.1 of the main text. 3.2 - Sl opeStabi l ity and Erosion The Devil Canyon reservoir will be entirely confined within the walls of the present river valley. This reservoir will be a narrow and deep with mihimal seasonal drawdown. From Devil Canyon Creek downstream tc the damsite, the slopes of the reservoir and its shoreline consist primarily of bedrock with localized areas of thin vaneer of colluvium or till. Upstream of Devil Canyon Creek, the slopes of the reservoir are covered with increasing amounts of unconsolidated materials, espe- cially on the south abutment. These materials are principally basal tills, coarse -grained floodplain deposits, and alluvial, fan deposits (see Appendix J). Existing slope failures 'in this area of the Susitna River, as defined by photogrammetry and limited field reconnaissance, are skin a,nd bi- modal flows in soil and block slides and rotational slides in rock. The basal tills are the primary materials susceptible to mass move- ments. On the south abutment there is a possibility of sporadic perma- frost existing within the delineated areas. Upstream of this area K4 the basal till is nearly continuously frozen as evidenced by field in- formation in Borrow Area H. Downstream of the Devil Creek area, install lity is largely reserved to small rock falls. Beaching will be the primary process acting on the shoreline in this area (Figures 3.1 and 3.2). Although this area is mapped as a basal till, the material is coarser grained than that which is found in the Watana Reservoir and is therefore more susceptible to beaching. In areas where the shoreline will be in contact with steep bedrock cliffs, the fluctuation of the reservoir may contribute to rockfalls. Fluctuation of the reservoir and therefore the groundwater table, ac- companied by seasonal freezing and thawing, will encourage frost heav- ing as an erosive agent to accelerate degradation of the slope and beaching. These rock falls will be limited in extent and will not have the capacity to produce a large wave which could affect dam stability. In Devil Creek, a potential small block slide may occur after reservoir or dam. Above Devil Creek up to about river mile 180, beaching will be the most common erosive agent. Present slope instability above reservoir normal pool level will continue to occur, with primary beaching occurring at the shoreline. At approximate river mile 175, there is an old land- slide on the south abutment. This large rotational slide is composed of basal till which, for the most part, is frozen. A large bimodal flow exists within this block headed by a large block of ground ice. Yearly ablation of the ice results in flowage of saturated material downslope. The landslide has an arcuate back scarp which has become completely vegetated since its last movement. However, this landslide, which has an estimated volume of 3.4 mcy, could possibly be reactivated due to continued thawing or change in the groundwater regime brought about with reservoir filling. Since the maximum pool elevation extends only to the toe of this slide, it is unlikely that a large catastrophic slide could result from normal reservoir impoundment (See Figure 3.3). However, potential for an earthquake -induced landslide is possible. A mass slide in this area could result in temporary blockage of river flow. The distance from the dam, the meandering of the river valley, and the shallow depth of the reservoir in this area makes the potential of a wave induced by a massive landslide that could affect the dam stability very remote. In'general, the following conclusions can be drawn about the slope con- ditions of the Devil Canyon Reservoir after impoundment: - Minimal drawdown of the reservoir is conducive to stable slope condi- tions. -, RCYfSI - The lack of significant depths of unconsolidated materials along the lower slopes of the reservoir and the existence of stable bedrock conditions is indicative of stable slope conditions after reservoir impounding. - An old large landslide in the upper reservoir has the potential for instability, which, if failed, could conceivably create a temporary blockage of the river in this area. - The probability of a landslide -induced wave in the reservoir over- topping the dam is remote. 4 - WATANA RESERVOIR 4.1 - General Preliminary reconnaissance mapping of the Watana Reservoir was perform- ed during this study and principal rock types and general types of sur- ficial material were identified. The topography of the Watana Reservoir and adjacent slopes is charac- terized by a narrow V-shaped stream -cut valley superimposed on a broad j U-shaped glacial valley. Surficial deposits mask much of the bedrock in the area, especially in the lower and uppermost reaches of the reservoir. A surficial geology map of the reservoir, prepared by the COE, and airphoto interpretation performed during this study (Appendix J), identifies tills, lacustrine and alluvial deposits, as well as pre- dominant rock types (11). 4.2 - Surficial Deposits Generally, the lower section of the Watana Reservoir and adjacent slopes are covered by a vaneer of glacial till and lacustrine deposits. Two main types of till have been identified in this area; ablation and basal tills. The basal till is predominately over -consolidated, with a i fine-grain matrix (more silt and clay) and low permeability. The abla- tion till has less fines and a somewhat higher permeability. Lacus- trine deposits consist primarily of poorly -graded fine sands and silts with lesser amounts of gravel and clay, and exhibits a crude stratifi- cation. On the south side of the Susitna River, the Fog Lake area is character- istic of a fluted ground moraine surface. Upstream in th'e Watana Creek area, glaciolacustrine material forms a broad, flat plain which mantles the underlying glacial till and the partially lithified Tertiary sedi- ments. Significant alluvial and outwash deposits exist in the river valley. Ice disintegration features such as kames and eskers have been observed adjacent to the river valley. �RC�S K-6 Permafrost exists in the area, as evidenced by ground ice, patterned ground stone nets and slumping of the glacial till overlying perma- frost. Numerous slumps have been identified in the Watana Reservoir area, especially in sediments comprised of basal till. Additional details regarding this subject will be given in subsequent sections. In addition, numerous areas of frozen alluvium and interstitial ice crystals have been observed in outcrops and identified from drill hole drive samples. 4.3 - Bedrock Geology As discussed in Section 6 (Main Report), the Watana damsite is under- lain by a diorite pluton. Approximately three miles upstream of ,the Watana damsite, a non -conformable contact between argillite and the dioritic pluton crosses the Susitna River. An approximate location of this contact has also been delineated on Fog Creek, four miles to the south of the damsite. Just downstream of the confluence of Watana Creek and the Susitna River, the bedrock consists of semi -consolidated, Tertiary sediments (8) and volcanics of Triassic age. These Triassic volcanics consist of metavolcaniclastic rocks and marble (3). From just upstream of Watana Creek to Jay Creek, the rock consists of a metavolcanogenic sequence dominantly composed of metamorphosed flows and tuffs of basaltic to andesitic composition. From Jay Creek to just downstream of the Oshetna River, the reservoir is underlain by a meta- morphic terrain of amphibolite and minor amounts of greenschist and foliated diorite. To the east of the Oshetna River, glacial deposits are predominant. The main structural feature within the Watana Reservoir is the Talkeet- na Thrust fault, which trends northeast -southwest (3) and crosses the Susitna River approximately eight miles upstream of the Watana damsite (Figure 4.1 - Main Text). Csejtey and others (2) have interpreted this to have a southeast dip, while Turner and Smith (10) suggest a north- west dip. The southwest end of the fault is overlain by unfaulted Tertiary volcanics (2). A detailed discussion of this fault is pre- sented in Woodward -Clyde Consultant's Task 4 Report. A general discus- sion of regional geology is presented in Section 4 of the main text. 4.4 - Slooe Stabilitv and Erosion Most of the slopes within the reservoir are composed of unconsolidated materials. As a generalization, permafrost is nearly continuous in the basal tills and sporatic to continuous in the lacustrine deposits. In Figures 2.12 through 2.28, the distribution of permafrost has been de- lineated primarily on the flatter slopes below elevation 2300 feet. Inclined slopes may be underlain by permafrost, but based,on photogra- metric characteristics, the active layer is much thicker indicating that permafrost soils are thawing, and/or that permafrost does not exist. Existing slope instability within the reservoir (as defined by aerial photographic interpretation (Appendix J) and limited field re- connaissance), indicate that the types of mass movement are primarily K-, �CBES solifluction, skin flows, bimodal flows, and small rotational slides. These types of failure occur predominantly in the basal till or areas where the basal till is overlain by lacustrine deposits (Appendix J). In some cases, solifluction, which originated in the basal till has proceeded downslope over some of the floodplain terraces. Three major factors which will contribute significantly to slope in- stability in the Watana Reservoir are changes in the groundwater regime, large seasonal fluctuation of the reservoir level (estimated at 60 feet), and thawing of permafrost. These factors were analyzed to determine their effects on typical conditions in the reservoir. From this, four basic models of shoreline conditions were developed (Figures 2.2 and 2.3). The two processes affecting the shoreline of the reser- voirs are beaching and slope stability. These models were applied to selected reaches of the reservoir shoreline and evaluated for condi- tions at or near normal pool levels. It should be noted that the slope stability of the Watana Reservoir was evaluated for the "worst" case which considered the maximum and minimum pool levels. In cases where sliding will occur, it will not be uncommon for some flows or possibly beaching to occur over the same reach. Slope instability during and after reservoir impounding will be addressed below. It is estimated that filling of the reservoir to normal pool level will take approximately three years. Due to the relatively slow rate of impounding, the potential for slope instability occurring during flood- ing of the reservoir will be minimal and confined to shallow surface flows and possibly some sliding. Slopes will be more susceptible to slope instability after impoundment when thawing of the permafrost soils occurs and the groundwater regime has reestablished itself in the frozen soils. Near the damsite, assuming that the present contours will remain un- changed, the north abutment will primarily be subject to beaching except for some small flows and slides, which may occur adjacent to Deadman Creek. On the south abutment, thawing of the frozen basal tills will result in numerous skin and bimodal flows. There is also a potential for small rotational sliding to occur primarily opposite Deadman Creek. On the south abutment between the Watana damsite and Vee Canyon, the shoreline of the reservoir has a high potential for flows and shallow rotational slides (Figures 4.1 and 4.2). In contrast to the north abutment, the shoreline is almost exclusively in contact with frozen basal tills, overburden is relatively thick, and steeper slopes are present. Thermal erosion, resulting from the erosion and thawing of the ice -rich fine grained soils, will be the key factor influencing their stability. On the north abutment below Vee Canyon and on both abutments upstream of Vee Canyon, the geological and topographic condi- tions are more variable and therefore have a potential for varying slope conditions. In the Watana Creek drainage area, there is a thick sequence of lacustrine material overlying the basal till (Figure 4.3). Unlike the till, it appears that the lacustrine material is largely un- frozen. All four types of slope instability could develop here, de- pending on where the seasonal drawdown zone is in contact with the aforementioned stratigraphy. In addition, slope instability resulting from potential liquefaction of the lacustrine material during earth- quakes may occur. Overall, slopes on the north abutment, in contrast with the south abutment, are less steep and slightly better drained, which may be indicative of less continuous permafrost and/or slightly coarse material at the surface with a deeper active layer. In general, the potential for beaching -is high due to: (a) the wide seasonal drawdown zone that will be in contact with a thin vaneer of colluvium over bedrock; and, (b) the large areas around the reservoir with low slopes (Figure 4.4). In the Oshetna-Goose Creeks area, there is a thick sequence of lacustrine material. Permafrost appears to be nearly continuous in this area based on the presence of unsorted polygonal ground and potential thermokarst activity around some of the many small ponds (thaw lakes/kettles). The reservoir in this area will be primarily confined within the floodplain and therefore little modification of the slopes is expected. Where the slopes are steep, there could be some thermal niche erosion resulting in small rotational slides. The potential for a large block slide occurring, and generating a wave which could overtop the dam is very remote. For this to occur, a very high, steep slope with a potentially unstable block of large volume would need to exist adjacent to the reservoir. This condition was not observed within the limits of the reservoir. In approximately the first 15 miles upstream of the dam, the shoreline will be in contact with the low slopes of the broad U-shaped valley. Between 15 and 30 miles upstream of the dam, no potentially large landslides were observed. Beyond 30 miles upstream, the reservoir begins to meander and narrows, therefore any wave induced in this area by a large land- slide would, in all likelihood, dissipate prior to reaching the dam. In general, the following conclusions can be drawn about the slope con- ditions of the Watana reservoir after impounding: The principal factors influencing slope instability are the large seasonal drawdown of the reservoir and the thawing of permafrost soils. Other factors are the change in the groundwater regime, the steepness of the slopes, coarseness of the material, thermal toe erosion, and the fetch available to generate wave action; - The potential for beaching is much greater on the north abutment of the reservoir; A large portion of the reservoir slopes are susceptible to shallow slides, mainly skin and bimodal flows, and shallow rotational slides; k 9 �u�7 - The potential for a large block slide which might generate a wave that could overtop the dam is remote; and -- The period in which restabilization of the slopes adjacent to the reservoir will occur is largely unknown. In general, most of the reservoir slopes will be totally submerged. Areas where the filling is above the break in slope will exhibit less stability problems than those in which the reservoir is at an interme- diate or low level. Flow slides induced by thawing permafrost can be expected to occur over very flat -lying surfaces. C; C1IMMARY Some amount of slope instability will be generated in the Watana and Devil Canyon reservoirs due to reservoir filling. These areas will primarily be in locations where the water level will be at an interme- diate level relative to the valley depth. Slope failure will be more common in the Watana reservoir due to the existence of permafrost soil throughout the reservoir. The Devil Can- yon reservoir is generally in more stable rock and the relatively thin overburden is unfrozen in the reach of the river upstream from the dam. Although skin flows, minor slides and beaching will be common in parts of the reservoirs, it will present only a visual concern and poses no threat to the project. Many areas in which sliding does occur will stabilize into beaches with a steep backslope. Tree root systems left from reservoir clearing will tend to hold shal- low surface slides and in cases where permafrost exists may have a stabilizing influence since the mat will hold the soil in place until excess pore pressure have dissipated. 6 - RFCOMMFNDATIONS It is recommended that typical slope conditions outlined in this report be further investigated during subsequent phases of the project in order to determine: - The magnitude of the potential for instability at a given location; and - Whether beaching or sliding will exist at major migrating herd cross- ing sites. �acus K,0 This investigation should include drilling, instrumentation and labora- tory analysis to confirm the findings in this study. Since only one significant existing landslide has been identified in this study, it is also recommended that further study be directed to this site to deter- mine the potential for future sliding in this area. 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Brown, W.G., and Johnston, G.H., "Dikes and Permafrost: Predicting Thaw and Settlement", Canadian Geotechnical Journal, Vol. 7, pp. 365-371, 1970. 2. Csejtey, B. Jr., Foster, H.L., and Nokleberg, W.J., "Cretaceous Accretion of the Talkeetna Superterrane and Subsequent Devel- opment of the Denali Fault in Southcentral and Eastern Alaska", Geolo ical Societyof America, Abstract with Pro- grams, p. 409, 1980. 3. Csejtey, B. Jr., Nelson, W.H., Jones, D.L., Silberling, N.J., Dean, R.M., Morris, M.S., Zamphere, M.A. Smith, J.G., and Silberman, M.L., "Reconnaissance Geologic Map and Geochronology, Tal- keetna Mountain Quadrangle, Northern Part of Anchorage Quad- rangle, and Southwest Corner of Healy Quadrangle, Alaska, U.S. Geological Survey, Open File Report 78-588A, p. 60, 1978. 4. Johnston, G.H. (ed.), Permafrost Engineering Design and Construc- tion, John Wiley and Sons, 1981. 5. McRoberts, E.C., and Morgenstern, N.R., "The Stability of Thawing Slopes", Canadian Geotechnical Journal, Vol. 11, No. 4, pp. 447-469, 1974. 6. "Stability of Slopes in Frozen Soil, Mackenzie Valley, N.W.T.", Canadian Geotechnical Journal, Vol. 11, pp. 554-573, 1974. 7. Newbury, R.W., Beaty, K.G., and McCullogh, G.K., "Initial Shoreline Erosion in a Permafrost Affect Reservoir, Southern Indian Lake, Canada", in North American Contribution to The Third International Conference on Permafrost, Edmonton, Alberta, National Academy of Sciences, Washington, pp. 833-839, 1978. 8. Smith, T.E., "Regional Geology of The Susitna-MacLaren River Area", Alaska Division of Geological and Geophysical Surveys, Annual Report, p. 356, 1974. 9. Smith, T.E., Bundtzen, T.K., and Trible, T.C., "Stratabound Copper - Gold Occurrence, Northern Talkeetna Mountains", Alaska Divi- sion of Geological and Geophysical Surveys, Open File Report 72, p. 11, 1975. 10. Turner, D.L., and Smith, T.E., "Geochronology and Generalized Geo- logy of the Central Alaska Range, Clearwater Mountains, and Northern Talkeetna Mountains", Alaska Division of Geological and.Geo h sical Surveys, Open File Report 72, p. 11, 1974. REFERENCES AND BIBLIOGRAPHY (Cont'd) 11. U.S. Army Corps of Engineers, Upper Susitna River Basin, Alaska, KLdroelectric Power _Supplemental _Feasibility Report, 1979. 12. Varnes, D.J., "Landslide Types and Processes", in Eckert, E.B., (ed.), Landslides and Engineering Practice, Highway Reserve Board Special Report No. 29, P...2O-45, 1958. I I BEACHING (I) - BEACHING (I) MINOR INITIALLY AFTER SEVERAL YEARS ASSUMPTIONS: FLAT SLOPES. COARSE GRAINED DEPOSITS OR UNFROZEN TILL AND LACUSTRINE DEPOSITS. STEEP BEDROCK SLOPES. FLUCTUATION OF RESERVOIR AND GROUNDWATER TABLE CAUSES FROST WEDGING TO OCCUR CAUSING ROCKFALL. FLOWS (II) ...... FLAT SLOPES. GENERALLY FINE GRAINED DEPOSITS, FROZEN. SLOPE MODELS FOR THE WATANA AND DEVIL CANYON RESERVOIRS FIGURE 2.2 jj INITIALLY AFTER SEVERAL YEARS ASSUMPTIONS SLIDING !q o O' •p•i , ,' A. �4 `, .gyp- -., .-.b�•' . SLIDING (IY) o a 7. ` - - •�• • ono:: . •p Uz) _ e, 777 r SLOPE MODELS FOR THE WATANA AND DEVIL CANYON RESERVOIRS STEEP SLOPES. TWO LAYER CASE, LOWER LAYER IS FINE GRAINED AND FROZEN. UPPER LAYER IS COARSER GRAINED, PARTLY TO COMPLETELY FROZEN. FLOWS IN LOWER LAYER ACCOMPANY SLOPE DEGRADATION STEEP SLOPES. FINE GRAINED AND UNFROZEN. STEEP SLOPES. FINE GRAINED AND UNFROZEN. NOTE: POSSIBLE FURTHER SLIDING IF THAW BULB EXTENDS INTO SLOPE WITH TIME. FIGURE 2 A�J DEVIL CANYON ELOV�i RESERVOIR BOLD CREEK WATANA RESERVOIR DAM k SCALE: 0 4 0 MILES LOCATION MAP LEGEND ------NORMAL MAXIMUM OPERATING LEVEL EL. 1455 -2000-CONTOUR IN FEET ABOVE MSL FIGURE 2.10 C) FIGURE 2.9 NA IGURE 2.8 r. ..FIGURE 2.7 0 FIGURE 2.5 4 2000 DEVIL CANYON DAM ATANA DAM .�/ '+` , t�� ~ _ FIGURE 2.6 wk FIGURE 2.11 2500 SCALE: 0 1 a MILES FIGURE 2.12 DEVIL CANYON RESERVOIR INDEX MAP �c�Es FIGURE 2.4 R 8 8 a ri w c , LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY-. i BEACHING U FLOWS ]¢ SLIDING (UNFROZEN) J5C SLIDING ( PERMAFROST) /i/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(TZ) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -I[ BEACHING AND FLOWS POSSIBLE IN DEFINED AREA f----- NORMAL MAXIMUM OPERATING LEVEL (' RIVER MILES I� 1 ' f3 A Q SECTION LOCATION AREA OF POTENTIAL PERMAFROST sg� / ;� k NOTES N-" I. REFER TO FIGURES 2.2 AND 2.3 FOR OETAI LED 5 DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS l 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 23UO FEET 3 AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ._�.'m ��I'�:•., t ��`\_, Jw - f �� ON AIR PHOTO IFICATlON INTERPRETATION AND WILL REQUIRE J: FUTURE VER f ins.. -..m,.� ,.�-< i�\ : li2C. '- %a� ""'. .%L • `ter '". c,' �_ \' \ 50�\` �\• _......,, APRROXIMAT-EDEVIL CANYON �.. \ ��-�✓ ��: ,, DAM LOCATION- •` l� Y ) - / N!" t `. — �y�, 0 1000 2000 FEET '<�•ziu, ax, 3�.-- �,. -�..3-.-. I 1 -r _ V i� �L SCALE • � „�< � :,�� r � t,�'.�y v •� , ) 'fir y T u' a cam` DEVIL CANYON SLOPE STABILITY MAP FIGURE 2.5 DEVIL CANYON SLOPE STABILITY MAP LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: 1 BEACHING II FLOWS JB SLIDING (UNFROZEN) 8 SLIDING ( PERMAFROST) /2/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(M) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING 7-II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA --- NORMAL MAXIMUM OPERATING LEVEL RIVER MILES A A SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED ❑ESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3 AREAS OF POTENTIAL PERMAFROST BASE❑ PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERWICATION D LOGO 2000 FEET SCALE FIGURE 2.6 ����� u a,rxn,u a 3.zMWO k 3,—,uao ��a aF I'no�nFreS"T- 1��a�6� 9[a!a' 1"' �n0o Gr.�a�: :u=. k+•«�ADO S� �N9EX h OL--Ul-r- -) I /AtiILI I Y MAP LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTAB€CITY: L BEACHING A FLOWS SLIDING (UNFROZEN) SLIDING (PERMAFROST) DENOTES AREA EXTENT ANO TYPE OF INSTABILITY I QZ) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING T-II BEACHING AND FLOWS POSSIBLE IN OEFINED AREA 1---- NORMAL MAXIMUM OPERATING LEVEL A# RIVER MILES A f. ? SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO OELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 9 AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1000 2000 FEET SCALE !RCflE� FIGURE 2.7 LEGEND EmAREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: I BEACHING u FLOWS x SLICING (UNFROZEN) 131 SLIDING ( PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I Or) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I-11 BEACHING AND FLOWS POSSIBLE IN DEFINED AREA 1--- NORMAL MAXIMUM OPERATING LEVEL Asx A RIVER MILES SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES 1, REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLDPE INSTABILITY MODELS 2. NO DELINEAT$ON OF PERMAFROST AREA ABOVE ELEVATION 23CO FEET a AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1000 2000 FEET SCALE DEVIL CANYON SLOPE STABILITY MAP FIGURE 2.8 a LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY, I BEACHING FLOWS IQ SLIDING (UNFROZEW 8 SLIDING ( PERMAFROST) DENOTES AREA EXTENT AND TYPE OF INSTABILITY I{IQ) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I —II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL A x A RIVER MILES SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES i. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1000 2000 FEET SCALE ETTTTTT- sw!e 9 k!£Y !N9fk DEVIL CANYON 1 r a LEI SLOPE STABILITY MAP FIGURE 2.9 ����� ,r 11Na.aca E n n,zs,cao — -- .��E5T !ND=x LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY. I BEACHING II FLOWS III SLIDING (UNFROZEN) 14 SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I (1Z) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA ---- NORMAL MAXIMUM OPERATING LEVEL n RIVER MILES A A SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REOUSRE FUTURE VERIFICATION 0 1000 2000 FEET SCALE FIGURE 2.10 ��s 'S�cia i +:OGJ�ty r.:4�•: intro rot. *Mi __—___—_—_ 3 2 a DEVIL CANYON SLOPE STABILITY MAP ?I LEGEND E AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: j T BEACHING II FLOWS SLICING (UNFR02EN) I4 SLIDING (PERMAFROST) DENOTES AREA EXTENT AND TYPE OF INSTABILITY I SIT} PRIMARY REACHING INSTABILITY WITH SOME POTENTIAL SLIDING I —II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL RIVER MILES A AA L jr SECTION LOCATION NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO OLLINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 9 AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VFRTICATION 0 IOOD 2000 FEET SCALE FIGURE 2.11 111 ff $ b r v x v F � e— rr w mLEGEND ---i'-"" AREAS OF CURRENT SLOPE INSTABILITY I ®TYPES OF SLOPE INSTABILITY: N I BEACHING II FLOWS III SLIDING (UNFROZEN) lY SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY T(IQ) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -]I BEACHING AND FLOWS POSSIBLE IN DEFINED AREA �^- NORMAL MAXIMUM OPERATING LEVEL -- NORMAL MINIMUM OPERATING LEVEL r r \R RIVER MILES 'r �;;` , f _ i f - -- I a'�_"'�r SECTION LOCATION .� IL I APPROXIMATE WATANA DAM CENTERLINE NOTES / l Y �;f; f ..eac __.r/' J � � � : _ _. I /•�i�'..��.-�f\ ,J DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS t � r `--_._. -tom/ -= •. J � _ � � �'�" / �' ��� , J REFER TO FIGURES 2.2 AND 2. 0 DE _ 3 FOR TAILED r .,� i..\_ _ _�_,-_. -..�-'� ` �, 2. NO DELINEATIONOFPERMAFROST AREA ABOVE ELEVATION �- _ ,-- - � 2300 FEET I /r t) A AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY APPftOX#MATE WAFANA �� �t ��! i" DAM CENTERLINE ' } .r / i ,.q r �� � ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION y )rf,y 6O / .. : 4 , 4 �4> �� � /--'-'� 7`� �"� ,�f,�t ».�/i `- � _ _�/ i r � � ' -L f �; yY � � -,.� -�._r f_"_' '" `•" ' �1I ,� 1, r. ,I ` ., � }fir %/ / '- [ (,\t\ (}cl �1^xV/ f� A. l f 51 P,3 SCALE 0 1000 2000 FEET ry ;Y DEVIL CANYON - SLOPE STABILITY MAP FIGURE 2.12 �C��� DEVIL CANYON 'LOw =i LOCATION MAP 01W CREEK I SCALE: 0 4 8 MILES UM EL IN SL INDEX MAP FIGURE 2.13 R��ES LEGEND mAREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: I BEACHING II FLOWS III SLIDING (UNFROZEN) ZQ SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY 1(8) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING T-IC BEACHING AND FLOWS POSSIBLE IN DEFINED AREA i �--- NORMAL MAXIMUM OPERATING LEVEL - NORMAL MINIMUM OPERATING LEVEL A r A RIVER MILES IL ? SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3, AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION. 0 1000 2000 FEET SCALE FIGURE 2.14 ���� dE :;. Sir1.GPn LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY I BEACHING II FLOWS TIC SLIDING ( UNFROZEN ) TZ SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY ICU) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL -- NORMAL MINIMUM OPERATING LEVEL A� A f. I SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION O 1000 2000 FEET SCALE FIGURE 2,15 �G"S ILTA 1 TIT -- i T l t b' L,� LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: r I BEACHING 7L FLOWS l I i 31 SLIDING i UNFRQZEN ) LQ SLIDING (PERMAFROST) !I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(7g) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING T-n BEACHING AND FLOWS POSSIBLE IN DEFINED AREA ` i I € j• t _�--- NORMAL MAXIMUM OPERATING LEVEL NORMAL MINIMUM OPERATING LEVEL RIVER MILES \.4 SECTION LOCATION i ( r'� AREA OF POTENTIAL PERMAFROST ' NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED t DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION t}� 2300 FEET ' t 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY f - ON AIR PHOTO INTERPRETATION AND WILL REQUIRE • �,' € FUTURE VERIFICATION 7 t l - • S , • � 1 r 7 - I ! °1 a� l -� �- 0 1000 2000 FEET -- -.._.. SCALE _._-..._.,.., WATANA SLOPE STABILITY ASAP FIGURE 2.17 CON g N I Cy�a pl i�p�a;r�ef.y� Y��tR �3i ..cs=.& �oPD Cc�new �vai.o3 a� 8 a u LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: T BEACHING II FLOWS TIT SLIDING (UNFROZEN) lY SLIDING (PERMAFROST) /T/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY - T(15L) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING T-n BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL - -- -`-' -'—�— NORMAL MINIMUM OPERATING LEVEL - %< RIVER MILES A A SECTION LOCATION f AREA OF POTENTIAL PERMAFROST !f NOTES I. REFER TO FIGURES 2-2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS ' 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION -._-------_._,._-__ 2300 FEET - - 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO FUTURE VERIFICATION INTERPRETATION AND WILL REQUIRE '.% x197_ { _.. aa,`` � `- � ,_� � � a \��` gee-cr J �' .h If! (t 5 `) � � ✓ j � '����` Ri xlg f 1`v� WATANA a SLOPE STABILITY MAP i + r f FIGURE 2.18 1 1 �+ s:zzarrN I N 7,zrn,c:r.� Goya at t��,a;nc»i r�:4-ti: 3v6G' :ryo..r LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABiUTY: T BEACHING II FLOWS SLIDING (UNFROZEN) lY SLIDING (PERMAFROST) r: /T/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY f 247Q) PRIMARY BEACHING INSTABILITY W]TH SOME r POTENTIAL SLIDING 1-71 BEACHING AND FLOWS POSSIBLE IN DEFINED AREA - - Y 1 � �--"--^ NORMAL MAXIMUM OPERATING LEVEL �t NORMAL MINIMUM OPERATING LEVEL RIVER MILES A A �% (TV) SECTION LOCATION 1.5 j NOTES ` \t I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS - c 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENT€AL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATICN WATANA SLOPE STABILITY MAP 0 1000 2000 FEET SCALE FIGURE 2.19 ����� 1 { I ShF. F.�.u�ox LEGEND l' AREAS OF CURRENT SLOPE INSTABILITY 0 TYPES OF SLOPE INSTABILITY \ I BEACHING - -- _ II FLOWS _ ]]I SLIDING (UNFROZEN) - IY SLIDING (PERMAFROST) _ /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(3Z) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -IL BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL - — _ — - ----^ NORMAL MINIMUM OPERATING LEVEL RIVER MILES A A SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES - I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED _ DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION i 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE _ FUTURE VERIFICATION iv- �F. i WATANA n ✓ 3j, SLOPE STABILITY MAP�1 1uIT O 1000 2000 FEET SCALE .... FIGURE 2.20 W I I (IV) LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: . . ... . .. ..... I BEACHING ........... . ... . .. . . . . II FLOWS .... IQ SLIDING (UNFROZEN I j SLIDING (PERMAFROST) :Z /I/ DENOTES AREA EXTENT AND TYPE OF INSTAS€LITY " ... ..... .... .. I (3Z) PRIMARY BEACHING INSTA81LITY WITH SOME 204-- POTENTIAL SLOING 1-3T. BEACHING AND FLOWS POSSIBLE IN DEFINED AREA �J:y J a NORMAL MAXIMUM OPERATING LEVEL NORMAL MINIMUM OPERATING LEVEL XW(%x RIVER MILES A A 202 SECTION LOCATION AREA OF POTENTIAL PERMAFROST K� NOTES .. . . ....... -3 —X —7 REFER TO FIGURES 2r2 AND 2. FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION IV' . ...... 2300 FEET .... . .... .. . . 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION . .... .. . .... .. . .... ..... . 0 1000 2000 FEET SCALE FIGURE 2.21 WATAN A .` _ SLOPE STABILITY MAP 4 LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: I BEACHING ]I FLOWS IT SLIDING (UNFROZEN) lz SLIDING (PERMAFROST) DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(]Y} PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I-7 BEACHING AND FLOWS POSSIBLE IN DEFINED AREA ---- NORMAL MAXIMUM OPERATING LEVEL --� NORMAL MINIMUM OPERATING LEVEL AAA RIVER MILES SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESOMPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION IDOO 2C00 FEET SCALE FIGURE 2.22 i'a�AEsl LEGEND EmAREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY I BEACHING II FLOWS m SLIDING (UNFROZEN) T$ SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(]Y) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I-11 BEACHING AND FLOWS POSSIBLE IN DEFINED AREA ---- NORMAL MAXIMUM OPERATING LEVEL NORMAL MINIMUM OPERATING LEVEL ®A Q RIVER MILES a SECTION LOCATION AREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DEL€NEATiON OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3, AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1000 20DO FEET SCALE FIGURE 2.23 1�Ci� I x s,' 4 r1 weft arnpr¢9*y: Y :0.8: WATANA SLOPE STABILITY MAP LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: I BEACHING II FLOWS Ill SLIDING (UNFROZEN) 8 SLIDING (PERMAFROST) /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I{3Zrj PR$MARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I-]C BEACHING AND FLOWS POSSIBLE IN DEFINED AREA ---- NORMAL MAXIMUM OPERATING LEVEL --- NORMAL MINIMUM OPERATING LEVEL x RIVER MILES A` A t.f SECTION LOCATION LLIAREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED ❑ESCRtPTION OF TYPE OF SLOPE INSTABILITY MODELS 2. NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION O 1000 2000 FEET SCALE _.. FIGURE 2.24 i�]�N �Wl k.IaKk c I (TV) � R >' t �i77"', t A �Ft' XGCS WATANA SLOPE STABILITY MAP LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY, I BEACHING II FLOWS ➢I SLIDING (UNFROZEN) 8 SLIDING i PERMAFROST I /I/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I07) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING I -II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA `—^--� NORMAL MAXIMUM OPERATING LEVEL ---�— NORMAL MINIMUM OPERATING LEVEL x RIVER MILES A A SECTION LOCATION NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE DF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3, AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1D00 2000 FEET SCALE _._,_,_.__ Emil ' FIGURE 2.26 A���� WATANA SLOPE STABILITY MAP LEGEND EAAREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY: = BEACHING jr FLOWS SLIDING (UNFROZEN) SLIDING (PERMAFROST) DENOTES AREA EXTENT AND TYPE OF INSTABILITY =fiY1 PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING 2—II BEACHING AND FLOWS POSSIBLE IN DEFINED AREA �'--� NORMAL MAXIMUM OPERATING LEVEL NORMAL MINIMUM OPERATING LEVEL A A RIVER MILES jr SECTION LOCATION NOTES I. REFER TO FIGURES 2.2 AND 2,3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEATION OF PERMAFROST AREA ABOVE ELEVATH)N 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO INTERPRETATION AND WILL REQUIRE FUTURE VERIFICATION 0 1000 2000 FEET SCALE wrr: FIGURE 2.27 C11 LEGEND AREAS OF CURRENT SLOPE INSTABILITY TYPES OF SLOPE INSTABILITY 2 BEACHING II FLOWS ]Q SLIDING (UNFROZEN) Tz SLIDING (PERMAFROST) /2/ DENOTES AREA EXTENT AND TYPE OF INSTABILITY I(IQ) PRIMARY BEACHING INSTABILITY WITH SOME POTENTIAL SLIDING T-]C BEACHING AND FLOWS POSSIBLE IN DEFINED AREA NORMAL MAXIMUM OPERATING LEVEL NORMAL MINIMUM OPERATING LEVEL A X q RIVER MILES tI SECTION LOCATION LmAREA OF POTENTIAL PERMAFROST NOTES I. REFER TO FIGURES 2.2 AND 2.3 FOR DETAILED DESCRIPTION OF TYPE OF SLOPE INSTABILITY MODELS 2, NO DELINEAT€ON OF PERMAFROST AREA ABOVE ELEVATION 2300 FEET 3. AREAS OF POTENTIAL PERMAFROST BASED PRINCIPALLY ON AIR PHOTO €NTERPHETATION AND WILL REOUIRE FUTURE VERIFICATION. O 1000 2000 FEET SCALE FIGURE 2.28 lasa�l w � L 0 0 0 rri w a ZD o 0 o LL- J J H Y U 0 0 o w wm J 11 V) W cr z Ld O Z J J LQ � W Z Z J w O Z fa Z z 0 � � 2 > U Z w o LLJ J a D J a a 0 la l CR�: O as a- U W O a: J 0 Z L O H wC) ww �U) S QQ 0 N yI O a W F- (1333) NOLLVAT13 z w w r �' S 0 >^ w D U' LO 1 li Q- 1 9' f •. Q.. a• w O U ��. lai J n • cr a o 0 U fN cn w cr �•v � J IAJ o. H V W LLJ .OD1 1' Z Z J g W LA o j - 06' W �. ® a- w �o� o z J I ', •, w m •;o • O ir d ' J •4' U) a t�, m z o_ J � w a w' it J ti w cn it a cr 0 a w i 00 cwn a a w @ � 1/ a9 f CJ Z H wU ww 0 g w Q g 0 o Q �S o g z (133-A NOIIVA3-13 F- w LL O O O P j O O a O J w J J N •�o o w w Z U) LLI in ®� J O� cwn< z w W� a� W U_ O Z W J �Ld � W �e J _J 7 N _ ~ LLJ O J W J J J 8] J W W w J 7 W fn O J O (A- Z d H O (D " m ix > N V :c W 111W III Q 0O a 0 Z 20 LL- W U ww i l i l 1 L l e N y O O O W N N Z {1333} 1d011t1113�3 � �� W 1 G� p 0 S 1.7 N IEIE€EI! W !€ z IlIElEI �a44• O OwC �n CCD in lllE#Elk! '•a ••� J :a a U N a'. W - a Y N U D ^ p U Z JW v�• W I O a m O U O J � LL U) wz w ` O � �a �U Zw Z N a m o w- W 0JQ �B® a v) WQ W Ix a a c� F- Qom w ca O a 0 cr J W ir w � U W w N J J Q a Z O Lr E H i- 0 0 a $ a c w N 0 w N N O w III. w LL.Z Cr [IC O .Q / NU wO Z)Z TO H LLJ C.) WW U) N O O O W p O O O O N N Z (133J) NOUVA3-13 r 0 0 0 r r � z 'i w fr O ix O :3 U) 6 cD LL L' l' w B' Q b' v c O � J .a 1 W J z ui o U- W J 1� z W J cr � a z Z A Cf) J O w J O �•'r x °. a w w `tioLLJ z > > ,. w w W J J �• O O a cr > > a O cr mq LL W W W O q �O W I' w I I � OJ fh cq f.. cr m Fr CQ w0 cr J M 0 z �0 r w c� wW 1 e e e • n • __�.. �__� M In O O w O O O O N N In z 1- a 0 N W LL Z J Z LL W G 00 a t4 ul IV LL 0� P :q yM CD op V Cl) 0 a: O U z w w ;m e � � o 0 III iI� De oc a U-Z t 1° o 1 N F- (V 0 wO OZ 0 W W L 1 1 rn fn 0 O O W O N N z (1333) NOIIVA313