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HomeMy WebLinkAboutAPA2347[]:{]&~~& c ~liD&®©© Susitna Joint Venture Document N~1mber Q341 Please Return To DOCUMENT CONTROL A~ Ill I 3 ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT RECEIVED . UN 2 1981 PJ_ASKA POWER AUTHORITY REPORT ON SECOND SPECIALIST CONSULTANTS PANEL MEETING~ BUFFALO, N!Y. FEBRUARY 17 & 18) 1981 Acres American Incorporated 1000 Liberty Bank Building Main at Court Buffalo, New York 14202 Telephone (716) 853 .. 7525 t$tt:f I 4 illl I ' I ' .. ' ' •.••• • I' .. • , • ' I" ' ' J, 4 • J , • ' I t "' , • • , ., ' t, 6 "" • I '( V , ' . • I ' , · V>o , / I' , ~ . . • . ~ . I . .. . I I I I I I I I I ;j I I I l ( ( I I [ 1 ii#.M¥4. td ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT REPORT ON SECOND SPECIALIST CONSULTANT PANEL MEETINGS) BUFFALO) N.Y. FEBRUARY 17 & 18J 1981 ACRES AMERICAN INCORPORATED 1000 Liberty Bank Building Main at Court Buffalo, New York 14202 Telephone (716) 853-7525 , I . . I I I I .I i ~I . I I E I I fr e I ( I 1 I l ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT REPORT ON SECONb SPECIALIST CONSULTANT PANEL MEETING TABLE OF CONTENTS 1 . Objectives 2. Agenda -February 17 3. Agenda -February 18 4. Group Organizations 5. Minutes of Meeting, February 17 6. Minutes of Meeting, February 18 7. Attachment I (Proposed WCC 1981 Activities) 8. Attachment 2 (Preliminary Project Layouts) 9. Attachment 3 (W~tana Pam Destgn Constderattons) 10. Report by Specialist Cons·ultants· •• t'~fl.~<i~J}:~t.:~;D:;-~:-.. .-~--:-:-~~:-'~:----~~~--~-~--·~··---;·-·~-l. -~--,7~-~---~ f '' ~..,1f"T1""65'i1"0iii111!iJt!'S'irnnnvui"'i"¥2m&a!WMi!#:.....,,., • · • ·- I I I I I E ' . r: a I I [ t . . 1. OBJECTIVES 2. The objectives of thfs series of meetings are to update the panel on work completed since the last meetings· jn October 1980 and to review: -Results of seismic studies to date as reported by Woodward-Clyde -Proposed seismic studies for 1981 -Results of geotechnical exploration to date -Recommendations of the Power Authority•s External Review Board (January 24, 1981) -Proposed geotechnical exploration for 1981 -Acres recommendations for Susitna development selection -Status of general arrangement studies at Devil Canyon and Watana -Status of arch dam analyses at Devil Canyon -Status of earth fill dam design at Wa~ana -Schedule further meetings to tie in with Acres continuing sttidi~s and APA Externa 1 Board meetings scheduled for March .19-.21 , June 3-6 and October 5-9, 1981 February 17, 8:30 a.m. -lOth Floor Conference Room, Buffalo 8:30 Opening remarks J. D. Lawrence 9:00 Development selection J. w. Hayden 9:45 Geological studies update Sa N. Thompson 10:15 Coffee 10:30 Seismic studies -proposed 1981 program V. Si.ngh 11:00 Discussion - 11:30 Geotechnical exploration -results to· date v. Singh 12:00 Lunch (brought in) 1:00 Geotechnical exploration -pr·oposed 1981 program v. Singh 2:00 Discussion 4:00 Adjourn (Dr. J ~ Douma accompanied by r. lfutcnJson vi s·it Acres Laoorator1~es in Canada to view j1ydraulic model.) . ·~·--~~:<.·::::-:rx:~::.,--.--:,-~--"..,_,~.--,----~-·---·-··---·,....---·--· ... ---·----·-~1~·"··---7---·· .. -·-.. ·-·-----~-:------·-----------·~------·--·--·~----~-. -~:::!JJi~ ~ ' · .. . .. ,""""!~Aiii!!i::Wa'S'W3"·T'-r!'!\15!i!il\:®rt7<tii!ilr..§arr*i~•~•k. ! "'"""'"" • "'"' ... . \ '· . ·.: I' I I I I I I I I I I I I I I 'I I I I ( ' . 3. February lB -8:30 a.m. -lOth Floor Conference Room~ ·suffalo 4. 8:30 9:15 10:00 10:15 11 :00 12:00 1:00 2:30 4:00 Devil Canyon general arrangements Devil Canyon arch dam analyses Coffee · Watana general arrangements Watana dam desjgn Lunch Divide into working groups to review (see item 4): -Arch dam design -Geotechnical (including Watana Dam) -Hydraulics/hydrology -Genera~ion plan~i~g Panel meets to prepare report Final summary and adjourn Group organizations: Topic Consultants Moderator R. Ibbotson R. Ibbotson R. Ibbotson V. Singh Location Arch dam M. Copen R. Ibbotson 9th Floor Small Conference Room Geotechnical (inc 1 • Wa taria R. Peck V •. Singh Graphics area Dam) A. Hendron (1Oth Fl oar) Hydraulics/ J. Douma I. Hutchison J. Lawr-ence's office hydrology (lOth Floor} Generation J. Hayden lOth Floor Conference Planning R. Mohn Room I I ' I ! I I I I I I I I I I I I I I I I 5. MINUTES OF MEETING held at the offices of Acres American Incorporated Buffalo, on February 17-18, 1981 SUSITNA HYDROELECTRIC PROJECT Second Specialist Consultants Panel Meeting PRESENT: Consultants Panel Dr. R.Ba Peck Mr. M.D. Copen Dr. A.J. Hendron Jr. Dr. L. Sykes (2/17 only) Acres American Inc. J.D. Lawrence C. Debelius J.W. Hayden S.N. Thompson V. Singh I. Hutchison A. Burgess R. Henschel J.D. Gi 11 G. Krishnan . . s. Bahadur H. Eichenbaum R. Ibbotson D. McDonald L. Duncan (a) Presentation by J. Hayden Alaska Power Authority Panel Mr. J. Douma Alaska Power Authority R. Mohn -Brief review of Task 6 Development Selection Studies which have been completed to date. -Based on analyses~ a combination of Watana and Devil Canyon provides the most cost effective development of the Upper Susitna River Basin. Also conciuded that Watana is the first development for the basin. - .... I I I I I I I I I I I I I I I I I I I I (b) Presentation B~ S. Thompson Brief review of regional and site geology by previous investigations. -Summary of 1980 mapping program objectives and scope of work. -Updated geologic maps and overburden thickness maps of both sites. -Review of special features at Watana and Devil Canyon. Included "Fins 11 and 11 Fingerbuster" shear zones, relict channel, possible fault in river and low velocity anomaly on ri9ht abutment at Watana, and large open joints (striking northwest), bedding of argillites, buried channel, possible fault through alluvial fan area, possible fault in river channel, and granodiorite encountered at depth in BH-2 at Devil Canyon. (c) Presentation by V. Sir~ -Brief review of wee scope of work and program for 1980. -Discussed Talkeetna terrain and relationship of features to plate tectonic model. Assigned magnitude 8.5 to Benioff zone. -Review of historical earthquake data. -Microseismic network objectives and data obtained. No apparent relationship between epicenter locations of micro earthquakes and known features at both sites. However, data clearly shows decoupled zone below sites with subductive plate about 50-70 km deep. -Review of WCC screening process for lineaments and field studies. Identification of four features at Watana (Talkeetna thrust, Susitna feature, ·Fins and KD3-7) and nine features at Devil Canyon site for further detailed study in 1981. -Studies indicate that reservoir induced seismicity is to occur for both reservoirs. very likely - 3 primary ground motion sources identified: Benioff Zone 8.5M Watana 30km (0.41g) Denali Fault 8.5M Watana 70km (0.21g) Castle Mtn. Fault 7.4M Watana 105km (0.06g) D. C~nyon 60km (0~37g) D. Canyon 70km (0.21g) D. Canyon 105km (0.05g) -General feeling that 8.5M on Benioff is controlling earthquake, but that this can be refined downward with additional work. -Reviewed earthquake magnitudes and associated accelerations at sites from 13 identified features in the event that they prove to be active. Could result in significant design changes. 1981 program has to be aimed at these features. -Presented proposed WCC 1981 program (typed sheets -handout) point by point discussion of program by panel. - I ·.1···. .. , I 1-· I I ' I I ill 1 I I '1. l ' I l I I I I I I I I I -General di'scussi'on as to what items had highest priority for 1981 wee program. . (d) Presentation by V. jingh Brief review of 1980 geotechnical investigation. Included mapping, borings, seismic refraction work, etc. -Look at special features at both sites. -Reviewed proposed borrow sources and material properties. -Presented proposed 1981 diamond drilling program (Acres panel considered this a minimal program) for both dam sites. Reviewed borrow areas exploration for 1981. -Discussed relict channel and additional work proposed by APA panel. Acres plan of additional seismic lines and flow net analysis to characterize channel. -Proposed seismic refraction surveys across river channel to define quantity of alluvium for construction. -Discussed proposed additional hole(s) in powerhouse area. Powerhouse location not finalized yet. (e) General Discussion -wee seismic trenching program -difficult to get definitive cost on trenches due to logistics and constraints on equipment. Best time is sprfng or winter but doesn't fit design schedule very well. J. Gill -practical to do trenching at Devil Canyon or Fins in summer but can't get to Talkeetna or Susitna feature until November. J. Lawrence -question if data is still usable in November. J. Lawrence -main concern is activity along Talkeetna thrust. If not confirmed early, then have to assume acti'Ve and design for .76g (assuming 354 mi length). No problem with Watana dam but affects· concrete structures.- J. Gill -sufficient mapping may eliminate need for trenching. L. Sykes -even if Talkeetna Thrust is not connected to Broxon Gulch Fault, can still get magnitude 7.6 +earthquake. J. Hayden -concern that data may be too late. Design for 0.46g and later get 0.76g may endanger the technical feasibility. C. Debelius -agree that FERC won't issue license. R. Mohn -APA wants to be conservative in license application. R. ~~-any significance to lack of micro earthquake data along Talkeetna? L. Sykes -no, historical data shows earthquakes associated with Talkeetna outside lOOkm radius. Left with mapping and trenching to define it. Feeling that a lot can be gained by showing that Talkeetna has not moved in the past 10,000 years. - tAWS._ .... r~ ,: ~-.. -~=. "~~~ '· ··, ~~ ..... · .. - lf I ll~ I . 1. : ' ! } I I I I I II ·JI ~~ II ~~ II -S. Thompson -concern about floating earthquakes. L. Sykes -no matter what you do you will still have a floating earthquake with at least 6.25M~ A. Hendron-use probablistic analysis to assess 6.5M'event occurring under site. Design for 0.4g for earthquake on Benioff zone. Floating earthquake of 6.25M has to be within about 6.6 miles of site to give · > 0.4g. R. Ibbotson -probably won't have significant overall cost impact to desi"gn for 0.7g as opposed to 0.4g. R. Peck -may get some failures of appurtenant structures but not critical to scnemes. J. Lawrence -general feeling that 0.4g could be used for preliminary design and be safe. Question is what APA will have to do to satisfy opponents of project. R. Mohn -maybe should be conservative now. -R. Peck -what steps do we have to take to live with big earthquake. No doubt that we can design economic dam that will survive. Not worried aoout powerhouse or other structures. Design dam for maximum earthquake and other structures for lower magnitude. H. Eichenbaum -may need to add low level outlet for drawdown. R. Peck -overall cost will be slightly higher to design dam for 0.7g and other structures for 0.4g but not prohibitive. J. Lawrence -use Oroville cross section? R. Peck-agree, if use gravel. It should rockfill you have to be more conservative. improved upon somewhat. Should be able to come up with. be adequate. If use Feel that section can be handle any earthquake you -J~ Lawrence -question of need for WCC calibration trench. R. Peck-feel it should be considered 11 0Ut of scope 11 • Not characteristic of site terrain and may be quite different. Don't feel it is necessary. V. Singh -Dr. Seed was also opposed to the idea and was going to talk to wee directly. (f) Responses by Panel -A. Hendron-question, which layout at Devil Canyon (arch or earthfill) was used for costing in Task 6 studies? J. Hayden -both layouts were looked at and cost is about the same. Arch dam is preferred. -A. Hendron -question, why isnAt 11 Fingerbuster 11 shear included in features to be looked at by wee in 1981? J. Lawrence -was not identified during their lineament studies, but has been pointed out to them for inclusion. -A. Hendron -question, what field evidence to say KD3-7 is not continuous to Devil Canyon? J. Gill -rock exposure between Watana and Devil Canyon~ no expression of feature in these areas. - I ,, If ·!·'; ! ' ~ I I I I I . I ll • r I I I I ' . -Proposed 1981 wee program dtscussion.(Attachment l) • Item 3 -refine ~1CE on Benioff zone -not consi·dered warranted by panel. Take out • • Items 4 & 5 -evaluation of historical earthquakes -considered to be worthwhile. Expected that this could be done for about $5,000 . • Item 6 -evaluate stress regime -some disagreement. L. Sykes -good data to have, low cost. R. Peck -money better spent on setting up microseismic network. • Item 7 -A. Hendron -question, why we need to evaluate MCE on active faults in Talkeetna terrain. Have already assigned magnitude to Dena 1 i Fault. vJhtch is actl've .. • Item 8 -low priority, take out of program . • Item 9-A. Hendron-concern about·time involved in looking at Denali Fault. Waste of effort. Look at other features local to site. ,R. Peck -feel that most of work on refining and evaluating this (MCE on Denali) is wasteful. Knew answers to some items last time panel met. , A. Hendron -willing to go with what we have on Denali now. No need to refine it and lower it . . L. Sykes -Benioff Zone is still likely to control .. design. J. D. Lawrence -Conclusion of Panel that nothing is to be gained by studying tfi.e Dena 1 i: furthe.r. • Item 10 -permanent seismic network. Agree on "Like to Have 11 it, but do not feel it is absolutely necessary to install it this year . Plan on installing in Phase II. Agreed to postpone until 1982. , !tens 11 through 14 -okay • Item 15 -revise attenuation relationship. L. Sykes .... do not feel there will be much difference from present case. Take out of program. • Items 16 through 18 -okay General discussion as to what should be in WCC 1981 program. • A. Hendron -need to look at floating earthquake and Talkeetna tb.rust. • L. Sykes -most effort has to go to items 1 and 2 (study of 13 features)., and floating earthquake. 8.5M on Benioff is too large, but probably will not drop below 7.8. Minimal effort to refine this. V. Singh -about 50% of budget is for ·Items 1 and 2. . ..... ··-_____ ..,......., .. ._,..,.._, __ ..,. _____ ..... -......_, ___ .. _,_ I 'I .I I I I .. [ I I I I I I • Discussion on criteria for determining recent displacement. R. Peck -do not feel that 100,000 year is ~ good criteria. have a good chance of dating features as being yo~nger or older than 10,000 years (Glacial} but poor chance of getting 100,000 year confirmation. Need to look at features and determine what data exists to put an age on it, and not worry about a specific age. S. Thompson ~ feel that it will be almost impossible to put 100,000 year date· on features because of terrain. R. Peck-what age can we put on reatures: 10,000 years -Glacial evidence 35,000 years -Carbon dating Geologic data to date very old features V. Singh-if no criteria on age (100,000 years), will this affect exposure analysis? A. Bur~ess -feels that it can be accommodated in probablistic analys1s. . J. Gill -first activity in 1981 will be to determine if any units can be identified which will give dates between 10,000 and 100,000 years {Quaternary geology studies). A. Hendron -at some point it becomes more economical to accept h1gher earthquake risk and get on with it. H. Eichenbaum -yes, but higher earthquake risk affects design of dams, equipment costs, etc. • J. Lawrence -have to look at Talkeetna thrust and put it to rest. A. Hendron -define difference between Talkeetna thrust, Fins and other features shown on photographs. Talkeetna and Fins exist, others may not. J. Hayden -feel part of 1981 program should lay to rest all 13 features as to fault or not, and age where possible . V. Singh -feels we wiil still have indeterminate features after 1981. R. Peck -should start at the site, develop geology and then work outwards. -A. Hendron -concerned about origin of andesites. It may be extrusive and flowed down old weathered valleys. Potential problem for tunnels. -R. Mohn -can Watana stand alone as cost effective scheme if Devil Canyon is not built later? J. Hayden -yes, still cost effective (> 1.7 benefit ratio). But High DeVll Canyon is probably the best single development scheme. -A. Hendron -all proposed holes for 1981 are aimed at disproving faults! J. Lawrence -not true, holes are based on recommendations of th.;s Panel in October. V. Singh -holes designed to pickup rock quality as well as faults. -A. Hendron -do not see need of BH-11 in Fins structure. Drilling could be used to better advantage elsewhere. V. Sin~-determine permeability, continuity, characterize zone, etc. - .! l.i • IJ' • IJ I 11 I I I [ -R. Peck -possibility of terrace deposits infilling relict channel at Watana being exploitable for shell materials. -R. Henschel -possible~ but materials are quite variable and the extent is unkno\"m .. -J. Gill -require layout schemes so that seheduling of drilli.ng can be completed. -· JiAot I I I I I I I I I I I I I I I I 6. Minutes of Meeting -February 18, 1981 Present: As for February 17, 1981, except for L. Sykes. (a) \\ \\ '\. Presentation on general arrangements and layouts -R. Ibbotson -Presentation of design criteria for Watana -for initial layout for remainder of project for multiple spillways arrangement. · High velocity in chute -175 fps. J. Douma stated precedents for 150 fps at Tarbela, Mica and in Iran. Need aeration to avoid damage. Only expected to operate few times, once in 20 years. Maybe able to accept some cavitation. Also· have to keep nitrogen saturation in mind-won't lose it in Devil Canyon reservoir. Add to it in Devil Canyon Dam, but may lose some in rough stretches of river-suggest discuss with Milo Bell. Use Flip Bucket aimed directly downstream, but have to avoid potential erosion problems. · R. Ibbotson -problem is aggravated in Devil Canyon due to nar- row gorge and possibility of under-cutting slope. Low level drawdown capability. Period of 12 months assumed to empty reser- voir -i~ this acceptable time frame? 20,000 cfs discharge required. · J. Douma -if failure imminent -can't drawdown fast enough, 12 months may not be of any use. May want to use low level outlet and also discharge through diversion tunnel -e.g. Mica Dam. Standard COE practice to install drawdown capability even if can't justify need. COE criteria is to drawdown half of reser- voir in three months. · J. Lawrence -Don MacDonald and I. McCaig are doing in-house search on drawdown practices at existing dams -will make recommendation. · R. Peck -need to look at risk from severe earthquake event - wouldn't expect to have to drawdown entire reservoir -damage may be restricted to upper section of dam. • M. Copen -USBR has past cases where rapid drawdown saved dam - not something to·· ove·rl ook at. ··Gates 1 ike ly to be· damaged by severe earthquake. · R. Peck -blastable plugs rather than gates in diversion tunnels may be something to look at. Gates likely to be damaged by severe earthquake. · R~ Ibbotson -three level intake with gates or shutters being considered. · M. Copen -shutters used with three -level intake at Flaming Gorge -works fine. -Presentation of design criteria for Devil Canyon -for preliminary 1~youts (4) - $§±)1144wa;:- " .. ""'-''*"',;;l:i!!.:!l'~~~~-......... 1....._. ... _ ............ _. -- l j \ ~ I ' ' I' IJ I . . I I I I I I I I I I I I I' I · A. Hendron -have you looked at ~tiffness of rock? V. Singh -varied between 1 x 10 psi and 3 x 106 psi · Discussion on design factor of safety .. M. Copen sa.vs that stresses due to earthquake will not exceed strength of concrete. Dam will not fail in tension -will crack -can only fail in compression if strength of concrete is exceeded. -Presentation of Watana layouts (see Attachment 2) · COE dam layout with Acres revised spillway, intake and toe of dam location . · Layout 1 -Conservative, single spillway, designed for PMF. R. Peck -how high is upstream cofferdam -(about 100 feet, not designed yet). If slopes of dam are flattened, may push upstream toe into Fins area. Problem also of being able to excavate alluvium. J. Hayden -Enough seismic lines proposed under dam area to get picture of alluvium. J. Lawrence -should bear in mind that this is only 1 of 11 alternative layouts that have been looked at ~ still being refined. We will be revising sections, center line location, spillway location etc. before finalizing layout. R. Peck-not knowing alluvium thickness and dam slopes -hurts you later when you need·more room and tunnels become longer, etc. · Layout 2 - J. Hayden -how much problem with diversion tunnels, etc. passing through 11 Finger Buster 11 ? V. Singh -feel that south abutment is better than North -will know better after drilling. R. Ibbotson-water passages longer on south-hare to pull dam centerline upstream to get ~owerhouse downstream of dam centerline. J. Hayden -intake needs to be unconstrained by 150' drawdown - lower intake will be required. J. Gill -why pull centerline downstream on left -R. Ibbotson - to shorten spillway. R. Peck -Use longer cascade spillway -unlined -get more rockfill for dam. J. Hayden -problem of locating spillway so it doesn't cross shear zones. Problem of putting downstream shell on shear zone and spillway in good rock. R .. Peck-exploration should be aimed at 'static geotechnics' of site to define problems for layout of dam -not seismic studies. · Layout 3 - R. Ibbotson -very economical spillway excavation. R. Peck -project section more downstream. J. Douma -cascade spillway also helps N2 problem. J. Hayden -will still be passing about 12,000 cfs through power- house if spilling, with about 50% dilution of N2. ~ 11 I IJ I I I I I I I I I I I I I I I I J. Douma -erosion will be on right side of spillway -channel will flow more to that s.ide. Hill also raise tailwater level. J. Hayden -should use stepped spillway to help this. Layout 4-Very constrained in vicinity of Fins -2.5:1 upstream slope on dam. R. Peck -if flatter slopes are used there could be a severe problem locating structures clear of the Fins and Fingerbuster features downstream. R. Ibbotson -this arrangement allows a favorable layout for rna i n s pi 1 hvay. J. Hayden -proposing to design main spillway for 1:100 year flood, then probably will not be a problem with surface flume. J. Douma -the flow would still be 50,000 cfs. R. Ibbotson -we may want to use emergency spillway -until Devil Canyon is built to eliminate N2. H. Eichenbaum - 2 spillway scheme has good flexibility. 10:10 -Coffee -Presentation of Devil Canyon Layouts -(see Attachment 2) · Devil Canyon earthfill dam layout. · Layout 1 -thin arch Problems -with spillways and discharge and concrete gravity dam a 1 ong top of 1 eft abutment -not very economi ca 1 o·r practi ca 1. · Layout 2 -(should be thin arch rather than 11 thick" shown on drawing) · Layout 3 -Optimum spillway location and alignments (Plan and sections presented) J. Hayden -what about Nz problem under normal operation of spillway? J. Douma -not enough information yet. If flume is designed to discharge at surface, should eliminate N2 problem, but may have lateral erosion problem. A. Hendron -have you looked at thick arch with powerhouse in dam and spillway on right abutment? M. Copen -would have to go to gravity section to do that, better to have surface powerhouse in that case. R. Peck -emergency spillway on left abutment way have problems of discharging into relict channel which may erode material under the saddle dam -may have to strengthen downstream section of spillway to prevent this. J. Hayden -any problem with gates and plunge pool at toe of dam? M. Copen/J. Douma -No! Has been done at Morrow Point with a so• deep lined pool. Devil Canyon has 90' depth of water, unlined. - [ I [ I I I I I IJ [ I I I I I I I I I "> ":. ~""~{-.~ . " ~-'~ ' ... M .. Copen -may be okay. Look at putting intermediate level intake on diversion tunnel to act as.emergency spillway- several existing dams did this with considerable cost savings. R. Ibbotson -with high flows expected, it may no~ be economical to enlarge small diversion tunnels during initial construction. J. Hayden -should check economics -may be cheaper to enlarge surface spillway unless low level drawdown capability is required. J. Lawrence -any thoughts on emergency spillway fuse plugs i'n general? Are they currently out of favor? J. Douma -no problem, as long as they go out when required - proposing one on Nippawan Dam now in Canada -may require model testing to optimize. Not too many in existence, only used for PMF. M. Copen -Don't see my problem with them. J. Douma -should be designed to save structure from overtopping. T. Buroess -if flooding occurs in spring, won't fuse plug be frozen and not easily eroded? J. Douma -will be exposed to warm water and sunlight. Considerable thawing by then, should be okay if well-drained. D. MacDonald-on Nelson River-frosting to 18' -20' until August! J. Douma -may be problem. Have to consider it. M. Copen -dropping water 700+ feet into plunge pool at toe of dam-may be problem. Should be dispersed by air during fall. J. Douma -plunge pool very dependent on rock quality. If highly fractured will erode quickly. M. Copen -gates required for spillway. J. Douma -should consider using cost of gates and plunge pool in dam in boosting capacity of main spillway to handle most of flow, and then use fuse plug spillway more frequently. I. Hutchison -system will be spilling very frequently -might not be cost. effective. · Thin Arch Dam -geometry presented. Assymetrical arrangement gives better stress distribution in abutments. 11:00 -Break into discussion groups: (b) Arch Da~ -. M. Copen/R. Ibbotson/H. Eichenbaum -Review of latest results of stress analyses and design assumptions. No significant comment. (c) Watana Dam Design -R. Peck/ A. He1tdron/ V. Singh -Presentation of Watana embankment sections -oriqinal COE layout. ~ Acres proposal for slight u/s -d/s slope on core. (see Attachment 3) · Portion of u/s shell constructed of cobbles. U/s -d/s slopes of shells vary from 1.75:1 to 3.5:1 u/s and 1.7:1 to 2.8:1 d/s assume alluvium u/s to be used in shell -use all available gravel shells. · Dr. Seed -has suggested core should be sloped more upstream. Also recommended making slopes similar to Oroville -for seismic shaking. This increases volume and cost. . ' - [ I [ I I I~ I I ( I I I I I I I I I · Some preliminary static analyses undertaken. Limited information on materials -used .4g earthquake acceleration. Results indicated a few inches of slumping. (no low strength materials in section). Allowing about 12' settlement for seismic considerations. Planning on removal of riverbed materials under entire dam. Will also look downstream for more alluvium to use as fill. R. Peck -any chanca of getting gravel materials out of buried channel area? J. Lawrence -may be possible, but elevation in borrow area D is not much higher than reservoir level. L. Duncan-low point is El. 2204-will require a saddle dam. R. Peck -what will be used for core? -(V. Singh -processed till materials from Borrow Areas D or H.) R. Peck -should put<~~~ in core, remainder in shells. At Portage Mountain -used this splitting of material - a good dam resulted -may also reuse alluvium from under dam with processing - will probably be more expensive than rockfill, but a better dam. V. Singh -concern about %fines in alluvium. R. Peck -definitely rather see more gravel in upstream shell than rockfi11, have to see what material is available and go from there. Beneficial to compensate for steeper slopes with better compaction. If flat slopes -don't. Suggest steeper slopes in section of cobbles in upstream shell from that shown which will tend to crack. Steeper section wi 1·1 have more tendency to crack further · upstream. A. Hendron -like idea of leaving core where it is. More stable than sloping upstream. -Presentation of Oroville Section R. Peck -don't want to duplicate core sections of Oroville -Acres section better in that respect. -.P.resentation of possible··failures caused by ·earthquake (Seed) A. Hendron -has tectonic tilting been considered in freeboard? y. Singh -allowed 12', don't have good handle yet on features which could cause tectonic tilting. J. Lawrence-currently (without looking in detail) have assumed it won't happen. V. Singh -need to review regional tilting from 1964 earthquake. L. Duncan -take MCE in region, calculate settlements and project to damsite. R. Mohn -has Acres looked at all items other than tilting? V. Singh -currently based on generic list, not all will apply. J. Lawrence -haven't rooked at design for overtopping. -Presentation of features to be included in dam to make it more resistant to earthquake (Seed) R. Peck -stability analyses should show that location of core and flattening of slopes upstream can be varied within a fairly narrow range before F.S. decreases and potential instability becomes evident. . ' :• . ·--·-·:~~~ ........ --.·------~-----o-:---~-::----------.,.·····;···"'f' ~"·-·--·~-. . ' -,, <> - I·~ ' r I·~ -' [ 11 .k l l ~ I I . ; I ( I I I I I I I I I · Discussion on foundation treatment (preliminary, prior to group discussion) R. Peck -must expect to have grouting and drainage -adequate funding should be allowed. J. Hayden -will the 150-200' drawdown cycle cause any problems? R. Peck -should already be accounted for in design. Drawdown not rapid. C. Debeliu~-will there be freeze/thaw and ice shelving problems? J. Douma -may cause deteroration of rip-rap. ~·Duncan-at Curry-rock was very resistant< .1%@ 250 cycles -no reactivity. R. Peck -also will have rather thick rip-rap section. (d) Geotechnical Discussion Group -R. Peck/A. Hendron/V. Singh -Discussion of grouting galleries at Watana/Devil Canyon R. Peck -at James Bay, grouted from surface after cleaning -need wide blanket grouting-which can't be done from gallery. Not good to ·blast rock for gallery. Question: What do you do about grauting and permafrost? L. Duncan -CRREL work -2-3 meters -pumped river water through rock. R. Peck -should strip abutments. -Discussion of dr1inage galleries Ro Peck -Desirable, work up abutments as you go. A. Hendron -can see advantages to drainage galleries. R. Peck -discharge drains into shells. J. Gill -do you need to have access to drains? R. Peck -don't feel that drains are likely to clog up. D. MacDonal~-chief purpose of galleries is to get back in later. A. Hendron -galleries useful to show where seepage is coming from. R. Peck -design system based on geology and requirements. Rather seegalleries in abutments than undet~ dam. Don't like raised gallery through fill. Some concern about stress relief features under valley bottom. Need not make decisionnow, but allow funds to cover drainage and refine later when you have more data. Show galleries in abutments and holes under dam for now, but may end up with just holes in foundation. A. Hendron -is ·there a drainage ga 11 ery ·under spi 11 way chute? fl. MacDonald-yes, center gallery with drain holes -primarily to drain underside of slab. R. Peck -another potential problem -open joints running parallel to grout curtain -may have to angle holes upstream. L. Duncan -the COE design assumed combined drainage and grouting galleries. COE also worried about not being able to get back in to grout if leakage occurred and that instrumentation would not survive to 800' depth. R. Peck -this type of a~rangement worked fine at Mica. Really need to do good foundation preparation -and schedule for it (e.g. James Bay). -r--~~. ~-· ~--~----·c·-----~-------_,1. -c-:::_----,----:c-----·····-·c-------~- ( ·~ (· ·~ I I I I [ I I I I I I I I I -Discussion on cofferdams -need bet·ms into excavation and drainage system-also cutoff wall. R. Peck -there will be a drainage system anyway. Meeting Adjourned - I I [ I I I I I I [ I [ I IJ I ··'" ... ' ... 7. ATTACHMENT I PROPOSED WCC 1981 ACTIVITIES - (./ i I I 1 ' ~ ~ ACTIVITY 1) Study significant features at Watana Site; active or inact1ve fault 2} Study significant features at Devil Canyon Site; active or inactive fault ~ -~ ~ TASK 4 ~ ....aii ~ .. PREtiMINARY'BUDGET.tAYOUT'FOR'1981 'ACTIVITIES . ---------- BUDGET WATANA OUT Of! STANDARD EMPHASIS TOTAL SCOPE $ 50t000 $ 50,000 . $ 50,000 '20-30,000 28,000DC 14,000 70,000 20,000 42,000W 56,000 13,000DC ---50,000 50,00Qi 37,000 50,000 .. -·;.~---- (iilllll -~ ATTACHMENT 1 COMMENTS Quaternary geology Field Mapping ~ ' Trenches {Contract 8) (Proposed 4) 1 -DC ~ ~· f ~t~·-~··· ,2 -Talkeetna Thrust 1 -Susitna Feature .1 -Fins I t ! I I ! i i I I l l } J I f ·! " l I I i , ,I 3) Refine MCE on the Benioff Zone and how close to site 12,000DC 18,000W 6,000DC 24,000W 30,000 I 28,000 ·10,000 (90% conf. 1 evel } 15,000 Calibration Remote Sensing 20,000 -----------Geophysics & Seismic Refraction Survey 10,000 t Review & Travel To include evaluation of low seismicity zones, 1964 earthquake & Japanese S.A. data j ' . ~"'Jili!IPI(i!i41!?4.A#II41441$1 QIM$#$24& AUI:W:::SAS,jtto®WIU t¥t;WJA ... IJQ i!Wl!J&4&W AUCZ 141 ¢it ... 41U£#2,.·~-··· ~··· ~· .·11·.11 · .•.. , : ·~:·: .. ·: ... ·:: . •. . . . t».Jil!f ... ..-(,'j. ·----• ,. . ,/ ~ . -~ ~ ... --• ~ ~ ~ ~ ~ ~ tal! ,.. .. ~' ._, ... ... , -- .• TASK'4·-PRELIMINARY BUDGET.LAYOUT'FOR'1981 'ACTIVITIES (~ontinued) -------~------~---------------- • ACTIVITY 4} Evaluate location and sources of mod. to large historical earthquakes in Talkeetna Terratn 5) Evaluate location and · sources of mod. to 1 arge hi stori ca 1 earthquakes north of Talkeetna Terrain 6) Evaluate stress regime within the Talkeetna Terrain 7) Estimate the MCE for active faults in the Talkeetna Terrain 8) Continue evaluation of the of RIS on the maximum c're'dibl e . · .ea.pthquake · 9) Refine MCE on the. Dena 1 i Fault BUDGET -liJATANA OUT OF 'STANDARD' EMPHASIS TOTAL SCOPE $ 10,000 -' 1 ll nc ~. trip to UAGI) 7,000 5,000 $ 20,000 5,000 . Budget included under (1) & {2) and (18) ' 10,000 20,000 ,_.. Pa61-!IJ.1 of~~!*-~ 1(4] ~ COMMENTS To include other events To include more events ~· '1 ,, """"*44= 1 I IV-''"" · liM¥ il !IIQ MA""*'IIi44%CA11f!AI::U. Q 4lh CI!IIJ!:U:CCUY. Xi MC:W U.JU)WJJIIIU IS:L -lliJMS C-IS as: a uwr = m .- I I -A I ' ~ • '~. • • < ~ " ... ~ , ~= ._ .. ~>'-!S<JOJ ... J1'_;·! "'' n ;·:j \1 I . . J :l I 'I I l I .-1 1 j '11 \\ l \~ '4 . I ",, , .. ~ lj l 1 l I I I l f , I I . I i I l 1 I ·! l J _j ! ·I -t .-J ti I ~ ~ ~ ~~ ~ ~ .. -~ ~ ~ .._ ,... .. .... ..... ageJIIII>f ~ .,.... TASK 4 -PRELIMINARY BUDGET LAYOUT FOR 1981 ACTIVITIES (Continued) • ACTIVITY , 10) Install and operate seismic network in 1981 11) Determine ground motions for design. at Watana Site 12) Determine ground motions for design at Devil Canyon Site 13) Evaluate dam stability 14) Assess stability condi- tions along trans- mission line row and roads 15) Revise.attenuation relationship 16) Redo exposure analysis J7) Prepare a seismic net\-Jork installation & operations manual 18) Prepare final report STANDARD BUDGET WATANA OUT OF EMPHASIS TOTAL SCOPE $ 27,000 $100,000 to 200,000 . 7,000 to COMMENTS 8,000 -----------To develop time history 2,000 5,000 8,000 Only for Benioff Zone Included under (11) and (12) 35,000 112,000 ~ · .. !J!¢¢i • .4£l\41jii. AIU;;;;;o::. MJUI u QJJbld'A!HLAt 4 ;o cszu:JJu: oauyuuaau ••:yxzaa u;u.asaMu LUI au &ZR•t mamw.a£LI11¥ a ;g : c t&L&-• m • ,. , ~ ,<·. I I' I' I I 1., I I' a: I I I. I I I I 8. ATTACHMENT 2 PRELIMINARY PROJECT LAYOUTS .-'""'' a aq I . \ .lc /I ... ~ .. ~ --~ .. --~ Watana Rockfill Dam Devil Canyon Rockfill Dam Arch Dam Arch Dam SUSITNA -APA SPECIAliST CONSULTANTS MEETING FEBRUARY 17 & 18, 1981 ":' Corps layout Acres layout -Staged Acres layout 1 Acres layout 2 Acres layout 3 Acres layout 4 'Acres layout Acres layout 1 Acres layout 2 Acres layout 3 , Sections for layout 3 Geometry .. j .. ; 1111111! . . ...-~ ~ f . C)· ~~ lDlBIJ!I.,.U iifl run t 1 r JL. .. ~ . .. liiiOIIIIII ... (' . , ...... j ... . '. .---~r-~·---=------~--.. -------------~--·-~--~·--·----"'----------.. --------------.,:----·'7-··~ ' . I I I I I I I 0 I \ \ I ,.. _, \\ ' i i l \ I ' i i ' I I i I I I I l i l i :// I I I ./ ·ht I I ~: ,, I I t ·r u • .. ... ti ~ Ul .. ~~~ oC Q u.l ...1 ~ ~ i&: .. 0 u C1l! 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I! .!.;._f f ..... ,.,.,, ' w1u:.tl,~ I ) J .. I { \ .......... LU.IUM SHO<ke 01. OIU.I:>Gi.D O<Jr) GENE@~L ARQANGEMENT • ~ !' -~ EMERGENCY SPILLW .. Y- IIGAL£ 0 100 1!!!!!!!5 • I . § Et. 14!:6' { -IIIII!!! III I :).1/ l ___ t~ . -. --1--"Wi!\jFIIlCjiWMi'\14""11WWW ... J4$)CVIIU ¥ i.OAWCU 4J$Hi#IJl!¥Q¢Wi( i4 W41\!Pi¥1J l~IWi 14UJ. S!WQ&; #.1 JUS I iii,WzaM $$1 SZSAWQ #iAC US !AJJP .4W!41W~&& - " '1111 . ' ! ' ' -~ a G F a: +- D f c( c .. :"r • ....... ,~ I ~ ~ .....:.._...... __ ,"'-] 10 & 1'1 7 G Ma> ·~ •:~~X>. F I ICC> f" 1-14( TWI. I!L '12a' ...... 1\\\. &!.. .• , •• £ CROW"-! SE.CTION 0 c ~r .[WL El..J4"1~' l4<:b ao<> ·- ~·- l:l liC:O lOCO "'eo 800 <A } SECTION TJ.IRLJ FoWER. FACILITIES l I I ~~ ~ ~ ~ .. IIIII .. DW - • • 3 lJC¥1 "-" ... --.......... ..... ~. ~', _j-· E~ 1445' lifO r- 1100 IIOCI - . ..... lOCI 7DP ., ... POWelrllCUI. P!!I.II'IOC.II. ,.~ ... , ... .,. a11ouww ~ ~ ~ l!ll DAM PR.OFIL~ rtt,l -Oov£fl:.oo~ lU~ ~ ,. M.I).WL!L.Ct-~1 -~---.... --:utrl&N*'---~ ~ --IHut ~ :~L.ao'""' 4t.lll' u·,.u· ........ ,., .. ...------: ...... ·~~- UQQ 1\00 11 .... --~9 ·- """ IDO ... ' ' ' / ... " .... -lloOQ (lii'T 111>1) >(-__ z .. M~·--··--· .......... ... ' ... . ...... SECTION T14RU SPILLWAY :OC ... Lit 0 100 1.!00 iFEET lfl[ll Mil 2 --..... .... 10 ____ j • T • I ' I • I • I • . . . r,... r=r ,_,_ F=·~ 14"= • .._ ·--• Eal G " E 0 c • 8 A tl I " ... w Q . u " • ~ • .. I ::r 'J on • w _, C1 0 z .. < ~ ..I .. ~ <t llf I ! ... 1-_, z ~I '1 w 4 u l J IL I 4 ~ "' 0 I .... 2 :i "' \J • = ~ ~ ~ I ;:! ! ! ~ llf .. C1 <( (loa) -... .,. i5 I ., I "'" :!'i: ~a "" I I >- Ill I-w ~ 0 w I " z 0 5 .. w -1) I z ~ 0 Ill ~ • v ~ 2: : l Sj~,-: I -=-~ ... ~;;; : .. ' -... Ut- ~ ~ - ,.. ~ w 3 ~ .. ~ ~ ; ~ I : s r .. (l..o1 1'40lJ.Y .... ~~ ,.. ~ " ~ ~ ~ & g ~ ~ ~ g .. ~ !! .. ": e . .· ' I ~ ' ' .. ; .. ·-~ ' • ' '• ' ' ' , / ' . ~ . • - \ 3 " ~ <1: 11. z <1: If I I I I I I I I I I ~ IJ IJ ~ ~ 9. ATTACHMENT 3 WATANA DAM DESIGN CONSIDERATIONS ~EV1"":'7~.:;;Jl';:'~•~~-.;::~:~c-,.,-oc,.~,...--:-..,..~!""",-:-":c:·;--::-...--:--:-o--,~--·····-~·~-~--...... -~~~~----...... .,.....,..,__.....,.. __ _ ,...., ,~' ~,;' "'0- ,_..,.. 1 '. ' lAiN -=•• ~ . ._.....,F""'""""":::--..... ~~, 11'!fi!A-~ I 1\ ti', I I I I ~ i I ~ ~ .. ~ ... • ~ 8 ... I ,.,.,., .. ,.J,J I I ~ ~ ... ~ c I J I 5 _,/ . ~ ... ·,.._., I 8 !!: • I -~ " il .. ... • .. -§ .J ... ~ "' u -~ -~ J "" ~ 0 -~ ~ -8 • -§ ~~~ i ~ l . ·I ; §! I ~ .. : I -· i .. c • ... .., a!; -! ; j ~ J. (·= • :: 4 ~~ j ... z -. I i ... ... ~-u I • i ... .., -... ~. J ... I ... = J J z ... II: g w 5 lt -::. ~ Q. i ~ --:~ . ... -...... ~; ~ -~ ~.. . J ai N " --- l ~ c:! ~.. .;_ -:i :.i ·~ ...... .; ~~ :lo ..... •• 5§ ,J ~-~ .. ~a -~ ... lil .. -~ .. -~ I ·~ I I I I I .I .· . • -tlr--50' I \ \_POSSIBLE LIMIT FOR· PLACEMENT OF ROUNDED COBBLES WATANA DAM ·~ CONCEPTUAL DESIGN-• . (--~-~·s-~,----~-------- · * B~SED ON A STUDY OF 28 MAJOR DAMS-FROM SEISMiCALLY ACTIVE AREAS-WORLD WIDE HEIGHT RANGE: 197 TO 800 FEET. - I I I I I_ I I I I , I t ~ 1.) ' -I .• . FOUNDATION CONSIDERATION~: . I -RQCK FOUNQATJO~ IS ADEOUATE TO SUPPORT THE DAM. " . . -ROCK IS R£L.ATIVEt...Y TIGHT FOR SEEPAliE CONSlDERATIONS 1 HOWEVER A GROUT CURTAIN WILL BE INCO.RPORATED. . . -PROVISIONS FOR DRAINAGE GALLERIES AND DRAINAr,E CURTAtN . IN ABUTMENTS -RivER ALLUVIUM VARY IN DEPTH FROM 40 T0·80 FEET-. -UNDER A LARGE MAGNITUDE EARTHQUAKE 1 THEI·R STABILITY (BOTH 'LIQUEFACTION & LOSS OF STRENGTH) IS . QUESTIONABLE -CURRENT THINKING lS·EXCAVATE UNDER THE ENTIRE DAHJ OPTIONAL TO LEAVE IN PLACE UNDER THE SktlL IF PIO~EN STABLE EXCAVAilO! OF ROCK DOWN TO UNWEATHERED ROCK ( ). Uf"DER THE CORE AND THE FILTERS A!'.CD REMOVAl. OF LOOSE ROCK UNDER THE SHELL IREAIMENI OF LOCAL ANOMALOUS~££ATURSS AS CONSIDERED NECESSARY EMBANKMENt DESIGN: -ZONED ROCKFILL DAM WITH IMPERVIOUS CORE & u/s -DIS FILTERS 'CONSTRUCIIOM_MAIERIAL REQUIREMENTS LARGE AND FINE GRAINED SOILS VERY SENSITIVE TO WATER CONTENT WITH RELATIVELY LOW OPTIMUM WATER CQNTE~J. PHILOSOPMY IN Q!SlGM -SAFETY OF STRUCTURE IS PRIME OB~ECTIVE -OPTIMUM USE OF AVAILABLE MATERIAL INCL, REQUIRED EXCAVATION . -MATERIAL PERFORMANCE UNDER STATIC LOADS~ EARTHQUAKE AND POST EARTHQUAkE CONDITIONS AND FROST SUSCEPTIBILITY . -DESIGN SAFEGUARD FEATURES AGAiNST SEEPAGE~ PlPINGJ CRACKING AND STRESS CONCENTRATION j. - I < ' t ~ I I .. ""' COIISIDERATIONS -OF CONSTRUCTION PROCEDURES AND EIVJRONMe~TAL CONSTRAINTS ON DESIGN ASSUMPTIONS -DEVELOPMENT LEveL & SEOUEHCE I.e. FULL DEVEloPMENr. · STAGED DEVELOPMENT~ ETC. . . DesiGN AeeRPAcH: -DESIGN A DAM CROSS SECTION BASED OF JUDGMeNT AND CONVENTIONAL PROCEDURES . -PERFORM SLOPE STABILITY ANA·LYSJS FOR STATIC LOADING CONDIITIONS -PERFORM PSEUDOSTATIC ANALYSIS TO EVALUATE THE OVERALL STABiliTY INDEX AGAINST LARGE SLIDING -- -PERFORM NEWMARK TYPE DEFORMAiiON ANALYSIS TO AID lN DETERMINING THE FREEBOARD REQUIREMENTS -PROVIDE DEFENSIVE MEASURES AGAINST EARTHQUAKE EFFECTS SUCH AS AMPLE FREEBOARD~ WIDE TRANSITION AND FILTER ZONES~ WIDER CORE CONTACT WlTH ABUTMENTS (A FURTHER REFINEMENT OF SEISMIC STABILITY ANALYSIS MAY BE DONE BY STUDYING PORE PRESSURE GENERATION & DISSIPATION WITHIN CRITICAL ZONES) .. I' I J I I I I I f i[: : .. " t ~ OROVILLE DAM GOlZE & SEED. 1967 VI I. OTHER EARTHQUAKE RES !STANT DESIGN FEA TURfS ~ . INHERENt IN THE CONVENTIONAl EMBANKMENT Di::SIGN WERE THESE ADDITiONAL EARTHQUAKE RESISTANT FEATURES: . 1. THE DAM ENBANKMENT WILL BE FOUNDED DIRECTLY ON BEDROCK OR ON A MINOR AMOUNT Of SAND AND GRAVEL WITH DENSITY GREATER . THAN THAT OF THE EMBANKMENT. THUS ELIMINATING ANY POSSIBILITY OF FOUNDATION LIQUEFACTION. 2. THE EMBANKMENT ZONING SCHEME PROVIDES WIDE TRANSITION ZONES OF WELL GRADED SAND AND GRAVEL BETWEEN THE SHELLS AND THE CORE. THE TRANSITION WILL BE DENSE AND ALSO RELATIVELY IMPERVIOUS. 3. FREEBORAD IN EXCESS OF WAVE REQUIREMENTS ABOVE NORMAL WATER SURFACE AMOUNTS TO APPROXIMATELY 17 FEET (5 METRES) WHICH IS MORE THAN THAT REQUIRED FOR ANY POSSIBLE CREST SLUMPING. THIS FREEBOARD IS AS A RESULT OF SPILLWAY HYDRAULIC REQUIRE-MENTS .. 4. THE CORE MATERIAL IS A DENSE, PLASTIC, EXTREMELY IMPERVIOUS MATERIAL WITH A WIDE RANGE OF PARTICLE SIZES. All MATERIAL PLACED AT CONTACTS WITH BEDROCK OR CONCRETE STRUCTURES WILL HAVE AN INITIAL WATER CONTENT FROM 1 TO 3 PERCENT ABOVE OPTIMUM TO ENSURE A PLASTIC ZONE IN CONTACT WITH THESE MORE RIDGE ELEMENTS. THE SLOPING CORE WILL BE PLACED AT OR SLIGHTLY WET OF OPTIMUM SO AS TO PROVIDE PROTECTION AGAINST POTENTIAL CRACKING. ~~~~1r-:::. _,ZrZ .~~ i . • ,fJD . ~;,~, # • ~· • • .. )~A"'~ ,.~; -· ; ~ .·~l·· . ~ -:~1 C:::X::::c:::::» • -r• -uw.a .. ue1 ~··~-... ==--·~ • u • n .. ..,. . .. -:.-::.::. :.:.:.. .. G).{!).~. ------0.G.·0· ----:..--..._ ~·-~· ... _. __ .....__., -·------.----. ...-. .. --.. _.,. __ • ._ _____ t' G't ....... -~----..-• .......,. -------~-----..... 0· ._ __ ._ --------a-e·--·--;·---.. -............. r--·--·--"'-.. _..,.... _!!)-G .• ·----.._.-.:.,_ ----........._ .... ....__..., ..-........... ...... __ ..., _____ ..,..,__.,.__, (!). c-.... _.---:.~-.......... • -.. .-.-................. ,_..,...._ _,. ___ ...., 0· ~----:--~--........._.. --... --...... 0 -(i). , ____ _ ,_._. ----...... i , __ _ ._ _____ ...._ ·--- I ._,..._.:.:,. ,_ ...... __ ~ ·--.._.._ Fi'-I . ·---·-----,. __ ......._.... ... _...,.. . ......._ ___ _..,_ :.-.... ---...... . -«----------------~ t . ).fuimum E'11,t-~n\rnc~tr S..•cfiott-Oro•inc Oua., JJ., .. &r .-o,, •. ,.lk -C'o"M J. ,. •• .q. I' '. - -,. .. I : I I I I l . . I . . , I I ' I I . I I I I . ' IABLE 1 · POSSIBLE WiYS IN. WHICH· AN EARTH~KE MAY . . CAUSE'EAILURE OF AN EARTH iJi · ·-·· .. 1 • DiSRUPTION· OF DAM BY MAJOR FAULT MoVEMENT IN FOUNDATION·~·. 2. 3. 4. . . LOSS OF FREEBOARD DUE TO DIFFERENTIAL TECTONIC GROUND t10VEMENTS. ' . . SLOPE FAilURES INDUCED BY GROUND MOTIONS, . LOSS OF FREEBOARD DUE TO SLOPE FAILURES OR SOIL COMPAC-TION. . 5. SLIDING OF DAM ON WEAK FOUNDATION MATERIALS. 6, PIPING FAILURE THROUGH CRACKS INDUCED BY GROUND MOTIONS, 7. OVERTOPPING OF DAM DUE TO SEICHES IN RESERVOIR. 8, OVERTOPPING OF DAM DUE TO SLIDES OR ROCKFALLS INTO RESERVOIR. g • FAILURE oF sP I LLriA v OR ouT.t.ET woRKs I CREF. "CONSIDERATIONS IN THE EARTHQUAKE-RESISTANT DESIGN OF EARTH AND ROCKE ILL DAMS" BY H 1 .BOLTON SEED, 1979) I' . . - •. .. Table 5 , Probable Upper Bound Displacements for Embankment Dams Sub ·cctcd to Ma ni tude 81, Earth \.Hlkes (little O·J;_no stren th loss) Crest k .Accn. • -- F.S•l.l5 F.S •1 .. 15 F;S ··1 .. 15· for ~or for ~ -0.1 k ,. 0.15 k-0.15 15\ strength 15\ strength, No strength . loss loss loss ky -0.10 Jc:l -0.15 ky -0.20 l.Og =o .4 =17 ft =7 ft =3 ft Probable · 0 •. 7Sg =0.3 upper ' bound of 0.5q =0.2 accelns. for I) =10 ft =3 ft =a inches . . . =3 ft =4 inches 0 most earth dams 0.2Sg =0.1 0 0 . 0 l i t ~ REF. Seed · (1979) ~· . • • • • I • • • • .. • I' • • - . . • 0 .. .. .. . . I I I I 'I ' Jr I I ll (I ~ . . In short, r:-.any of t.'le potentially . ha:rmful effects of earthq~akes on earth and' roc.kfill darns can be eliminated by adopting ·defensive measures W·hich render the effects non-harmful... A_ .. list of such defensive measur~s would inclu~ the .following: 1. Allow ample fr~eboard.to allow for settlement, slumpinq or fault moyernents. ·. . .. 2. Use wide transition zones of material not vulnerable to cracking. . J. Use chimney drains ncar the ccntr~l portion ~f embank~nt. . J(J. Provide ample drainage zones to allow for possible flow of water through cracks .. . !i. Use wide core zones of plast'ic materials not vulnerable tO cracking. 6. Usc a well-graded filter zone upstream of the core to serve as a 7. a. crack-s ~pper. Provide crest details which ~ill prevent erosion .in the event of overtopping • .,...,<J.._ Flare the embankment core· at abutmr:mt contacts. 9. Locate the cora to. rninjmizc the degree of saturation of materials. 10. Stabilize slopes. u.rotmd the reservoir rim to prevent slides into the rcscr·,oir. ~· . ll. Provide spcci~l d~tails if d~ger of fault movement in founda- tion. This list should not by any means be cn_n,6 ;~~.red 11 · ., ....... ._ a -~n~l.usive. CREF. SEED~ 1979). ,1 ~~----------------'·----~~----------------------------------------------~ 1: l -~·-.,..;.,.,-,,_.....,.. .......... ~. -~---"""-"'-'-'-"~·---._....._......,,.,.._....._._.,. ....... ~ r'"l:-~ ,~~---,. .\\ -• •--.--"'••~~·---~~- • 1 - .. .. nALSO, BECAUSE OF THE POSSIBILITY OF EARTHQUAKES, N~PLE CREST.WIDTM AND FREEBOARD WILL BE PROVIDED AND A COMPARA- TIVELY THICK CORE FOR THE PERMEABILITY OF THE MATERIAL . WILL BE ADOPTED~ IN ADDITION, S.INCE THE VIBRATION CAUSED BY EARTHQUAKE AT THE DAM CREST WI~L BE· GREATER THAN AT THE BASE, THE OUTSIDE SLOPES <EVEN AT THE UPPER. PORTIONS> WILL NOT BE STEEPENED, WITH BOTH UPSTREAM AND DOWNSTREAM FACES HAVING UNIFORM GRADES OF 1:2.5 AND 1:1.8 RESPECTIVELY.• <REF. FROM A DESCRIPTION OF THE AYRACIK DAM -TURKEY - "WATER POWER & DAM CONSTRUCTION~ DEC., 1975) ... . l. - l •• I I I'' I I I ·J I' 1: ~ ~~ ~ [ 10. REPORT BY SPECIALIST CONSULTANTS .. - ~ tl ~ ,n ~ I I ~· n w, n " l:J: [ @, li ~ t ?-1r. John La'tvrsnca Project Hanager 21 F;bruary 1981 Acres American Incorporated 900 Libarty Bank Building Buffalo ~Y 94202 Subject: Susitna Projact RECEIVED FEB 2 G 1981 Second Specialist Consultants Pansl Meating February 17 and 18, 1981 Dsar Hr. Lawrence: Introduction The members of the Panel 'Tisi ted the of fica of Acres Ameri- can in Buffalo on February 17 and 18, 1981. Information r:gard- ing prograss on the Susitna Project since the First Panel Meet- ing was provided to each P~nel Marnber prior to this visit. Dr. LQ R. Sykes participatad in the discussions on February 17, but because of other commitm:nts was unable to remain in Buffalo on Fabruary 18 and therefore did not assist in preparing this report. This report presents our consensus of the information ob- tained and suggsstions regarding futura investigations on ths projact. Ganeral Gsology and Seismology The comments on gaology and saismology in the Panel l.~tter of 25 October 1980 rsmain the view of the P,an2l and ara neither rapeated nor changed as of the date of this re.port. Since Octo- bar of 1980 NCC have indicated that the maximum ground accelera- tion at both Devil Canyon and Watana Dam sitzs from a magnitude 8. 5. earthquake on the Benioff zone \vould be on the order of 0. 40 g. In addition, an earthquake of magnitude 8.5 on the Dznali ~- Jl II t Johl'l La\.;r;nce -2-21 February 1981 Fault \>lOUld produce about 0.20 g at each site. These values seem reasonable to the Panel. Commants on this subjact are also givan in t..~e r:port by D-: .. Sykes da·ted 4 February 19 81. Tha main items of work that remain to be resolved are the investigation of features and hypothesized faaturas that pass naar or through the dam sites. Such features for Watana Dam are: (1) The Talkaetna Overthrust (ses letter of·October 25). (2) KD3-7, a linear drav..rn on the basis of air and satellite photography through the Watana dam site parallel to the Susitna 'River • . (3) The Susitna feature, another linear which has been dra,.,n to the northwest of Nat ana darn site. As stated praviously, gsologic field work needs to be done to substantiata if there is a feature; if thera is, ho\'1 continu- ous it is and what is its dats of last movereent. Of all the items listed above, the Talkaetna Overthrust is the only ~~11 de- fined tectonic feature, and the affort is definitaly justified to gathsr evidence on the date of last significant movsmant. Up to the pres.:;;nt, no othar feature mentioned above has been substan- tiated by diract fiald evidence. Sykes (February 19Bl) states that ·t:he 1912 and 1943 e.arth- quakas indicata that a floating earthquake of magnituds 6c5 should be con-··idered in the Talkeetna tarrain. On this prer.1ise, tha nead to investigate some of the shortar linaars dissappsars unless thsy are in the im..rnediate area of "the dam sites and could result in the offsetting of the proposad structures. In this connaction, it is suggested that the recv.rrance interval be com- puted for a floating earthquake of magnitude 6.5 occurring w£thin a distance of 10 km of the Watana Site, taking into account t..'l1e area of tha Talkeetna terrain, the psriod of observation, and the 1912 and 1943 observations. It is suggested that both wee and Dr. Sykes independently assess the probability of occurrence of this floating earthquake cl.oser than 10 km to the site. The foregoing corrJ11e.nts lead us to the follo'v,ring suggestions and conclusions concerning the preliminary budgat layout for 1981 activities being considered for the wee effort. I f t. [ I t ~· I. r I l ~4 ~- ~-- n n ll, n ~' John La\<Vrence -3-21 February 1981 Wa believe that t~a main effort should be d:voted to Activi-· ty (1), fiald mapping and Quaternary geology, particularly to devslop. the geological structure. near the ~~at ana site, to rsach conclusions r~garding the nature of the linaars or other faatures close to the site {KD3-3, KD3-7), and to obtain. whatevar perti- nent data can be assembled regarding the time since any nearby proven faults l'lera active (\'lhether post-Pleistocene, 'Tertiary, ate. 1 WithOUt referenCe tO an arbitra'ry age SUCh aS lQQ ,QQQ years) • r·· To the ~xtant that trenching at critfcal points may aid the mapping and dating, ';Y'e consider it to be a desirable adjunct, not a pri- mary effort directed toward determining an age oldar or youngar than 100,000 years. In ~iew of the possibility that the application fdr license may include the two-dam project, we favor a similar effort for tha Devil Canyon site (Activity 2) ~ We do not endorse the proposed calibration effort to test out the efficacy of dating procedures. We question whether remota sensing will provide furthar useful information, and we consider that geophysical and seismic refraction survays should be util~ ized primarily to extend t~e limits of knowledge of buriad chan- nals or other low-velocity zones already discovared, and especially to explor; the depths a.'ld areal ext;nt of the buried channels close to the darn sites, where they may influence tha layouts of b~e pro- jects with r:::spect to diversion, SP.ill'.'lays, power plants and '.'later passagzs, and foundation conditions. Ill short, we beliave the ax- panditures for these vital purposes should be primary objectives, and that inferences dra"t1n therefrom regarding seismicity should be considered as useful by-products. We believa the funds proposed for Acti vi tias ( 3) , ( 8) , ( 9) , ?.nd (15) could better be spant as an increased affort under Acti- vities (1) and (2). Hodast expenditures tL"lder l\ctivities (4), (5), possibly (6), (11), and (17) appear appropriate. Activity ( 10) , installation and operation of a seismic neb11ork in 19 81, vlould be desirabl-e for developing background information prior to ras·srvoir filling, but in view of the likelihood of a period of nearly 10 years before fillil:lg, the item could be dafsrred. The network could possibly than be astablishsd under the aegis of a permanent agancy. - Q· 0 G u .u D - John Lawrance -4- Enginearing Geology and Rock Engineerin~ 21 February 1981 Revised April 7, 1981 All comments from the October 25, 1980, report apply unchang- ed. It is felt that at laast two borings ars necsssary in the area of the undarground powerhouse at Watana Dam. Although explo- ratory adits will yield the best information on the feasibility of the underground powerhouse, it \vould be preferable not to spsnd the money on the adits at this time. It is suggested that a lay- out be considared for evaluation "'hich includes a surface po~var­ house, in order that the relative economics of ~~e surface and underground layouts can be compared before large sums ara expended to investigate the underground po":e:rhouse further. Since it has been found that the andesites immediately down- stream of Watana Dam ara extrusive, it is again ernphasi~ad that the base of the andesites and the underlying weatherad surface on the diorite should be more ·=xtensively investigated to avaluats the possibility that tunnels may intersect this unconformityo This f~ature could affact tailraca tunnals·frorn an underground pmverhouse or power tunnels to a surface powerhousa. Borings to investigate the nature of this contact should be given a higher priority than Boring B-11 prese:n-'cly proposed for the "fins" area ·of Watana. Additional borings supplemented by seismic exploration would be desirable to delineate an approximate width of the buried channel just upstream on the ri·ght bank of WATANA Dam site. Eventually percolation tests and pumping tests to determine the penneability of the channel should be conducted. Piezometers should also be placed at several locations in the buried channel between the Susitna River and Tsusena Creek to learn about any possible existing hydraulic gradients in the present condition of the channel. At the Devil Canyon site 1 b·11o angle borings have bean pro- posed on the left river bank, one dipping bsnaath the river and the ":::lther :into the canyon ~1all. The boring dipping beneath the rivar is intend~d to chsck the possibility of a shear zona be- neat~ tha rivar. Both borinqs are intended to explore the geolo- gic structure as well. Inasmuch as the most prominent jointing, and some observable shears seem to be oriented perpandicular to the axis of tha river, such borings may not disclose ~~em. On tha other hand, one or both borings might fortuitously be located entirely in one of the shears characteristic of metamorphic rocks and might give an erroneous conception of the rock mass. \\'e sug- oest that the. nae·d for these borings be r3vie"1ed and that, if they are deeMed necessarJ, they be oriented to cross the geologic s.tructure • . Watana Darn Layoui;:_ clr=vc:ral preliminar·y layouts , .. ,sre prasant·~.d and discussed for an ,;;rn.oankrnent dam at Natana. Ne concur that an external cross .... \ ' I ' !, 1 ij, ~ ~ ~ lf'l u Q (l u jf 0 " . John Lar:lrenca -5--21 Fabruary 19 81 . section similar to that at Oroville represents a satisfactory and conservative starting point. A darLl with thesa slopes requires a long diversion tunnel, whereas th~ length of the tunnel is con- strained by the configuration of the river and the quality of the rock naar the portals. The position of the cofferdams, similar- ly constrained, may in part determine the amount of riverbed al- luvium that ca~ be excavated baneath the darn. The depth of allu- vium \-till also be a significant factor in this determination. Hence, determination of the configuration of the riv=:r bottom and of the depth and character of the alluvium are considersd matters of high priority for 1981. A Backer drill, perhaps of large dia- meter, may prova useful in riverbed exploration. ~ve concur that an arnnle allowance for blanket and curtain .. grouting, for foundation traatment, and for drainage of founda- tion and abutments should be made in tha preliminary estimates. A decision regarding the adoption of drainage or grouting gal- lerias can and should be daferrad until mor2 is known regarding th~ character of the rock. An embankment dam~as been investigated in some detail for the Watana site. To provide a reasonable evaluation of alterna- tive design possibilities, a thin doubls curvature arch dam de- sign should be prspared and studied. The geological and topogra- phi,cal conditions at b'1e Natana site appear to be satisfactory for a structure of this type. Devil Canyon Dam Design An acceptable arch dam design has been prepared for the Devil Canyon site. Stress analyses 'qere made for normal full r~ssrvoir and maximum dra,qdo~V"n with appropriate concrete temperatures. The stresses computed for these conditions ara satisfactory. Some minor changes in the design can be made with minimal sf- fort and should improve the structural behavior while reducing the concrete volume required for the darn. An analysis indicating the effects on the design of earth- quake should be. made when appropriate ground accelerations ara datarmined. Response spectra analyses are satisfactory for this stage of developrnant. (~ u Q fJ 0 John Lawrance· t RBP/ajj ;.) - -6-21 February 1981 Yours sincerely, • Hendron Jr. /l£1 f"!1 u B f'1 u fj 0 • 0 0 0 r., u 0 Mr. Ralph B. Peck 1101 Warm Sands Drive, S.E. Albuquerque, New Mexico 87123 Dear Ralph, -tr-~~·~~ R .._ r-:_ ~. .... _ , , ~ .... :. --J:. •• -... .. 1 ••••••• .... ......,~-~.- Lamont-Doherty Geological Observatory of Columbia University Palisades, New York 10964 5 March 19.8f I have looked over the report you sent me about our meeting at Acres American in Buffalo on February 17-18, 1981. ·I have but one suggested change 9r comment to makeft On page 2 starting in the middle Df the page I .am quoted as indicating that a floating earthquake of magnitude 6.5 should be considered in the Talkeetna terrain. My main concern is that the magnitude of that event not be "cast in concrete" ,too quickly. In the report that I wrote for Acres I mentioned that work needs to be done by Wood~ard-Clyde to obtain better locations for earthquakes of about/ magnitude 7in 1912 and 1943. We need to know if those events actually occurred within the Talkeetna terrain and whether they occurred at shallow· depths or ~long the Benioff zone. If they cannot be shown to have occurred along the boundaries of the Talkeetna terrain or along the Benioff zone, it may be necessary to consider an event of comparable size within the terrain! itself. If they can be assigned to another feature, the size of the, floating earthquake could be smaller than 7. In an;:1 case, however, the occurrence of other events within the terrain (such as the shock of 1929) indicates that the size of the floating earthquake will probably be at least 6 1/2. My expectation is that the work that"Woodward-Clyde has been asked to do this year should help to resolve th-ese problems. Sin cere ly yours, Lynn R. Sykes LRS/lz cc: Mr. John Lawrence ·• .. .... , ... -. t j•, :-·, ...... ,_.l