Loading...
HomeMy WebLinkAboutTalkeetna River Project Alaska General Design Memorandum 1975TALKEETNA RIVER PROJECT ALASKA DESIGN MEMORANDUM DESIGN ALASKA DISTRICT, CORPS OF ENGINE ERS FEBRUARY 1975 REPLY TO ATTENTION OF: DEPARTMENT OF THE ARMY ALASKA DISTRICT. CORPS OF ENGINEERS P.O. BOX 7002 ~\ ,? ,~:11 ',' ~'~ NPAEN-PR-R 28 February 1975 SUBJECT: Ta 1 keetna Ri ver Proj ect, Al aska. \ ': Division Engineer, North Pacific 1. Transmitted for your ~eview and approval, in accordance with ER 1110-2-1150, are the following: a. 20 copies of the General Design Memorandum. b. 20 copies of the Environmental Impact Statement. c. Original and 20 copies of the Statement of Findings. d. 5 copies of draft local cooperation agreement. 2. Due to the small scale of the project, a GDM was prepared in lieu of a project restudy report. 3. The EIS has been fully coordinated with the State and other Federal agencies. Their comments have been incorporated into this final EIS. 4. Recommend immediate capability of $415,000 be expressed for inclu- sion in the Division's capability and that $16,000 be authorized and approval granted for preparation of plans and specifications. 5. It is further recommended that action be implemented to reclassify the status of the project from "Deferred for Restudy" to "Active." This is a project that could be started this ~lendar year to provide "Brick and !·lortar" type jobs as i ndi cated at th H~ Appropri ations Subcommittee on Public Works hearing on 25 February 19 ~., ~ ~~ Sinc~.r~4). ~rs~\ /-(01 "1. A---~ !> ______ ( __ .d ... ..,-,. ) £ I-t/{ ____ _ 4 Incl / CHARLES A. DEB '. US --. as {und sep cov Colonel, Corps 0" ,Eng'neers 'ct Engineer f .If { \~ ~ -----------". ".--~-.--- \ TALKEETNA RIVER PROJECT, ALASKA GENERAL DESIGN MEMORANDUM PERTINENT DATA Authorization The Talkeetna River Project was authorized by the Flood Control Act of 1958, Public Law 85-500, in accordance with the recommendations of the Chief of Engineers. General Dike Location Talkeetna, Alaska Drainage Area at Project Site Talkeetna River 2,015 Square Miles Susitna River 11,035 Square Miles Purpose of Project . Bank Erosion Protection Economic Life of Project 50 years Benefit -Cost Ratio . . 1 .2 to 1 Length 600 feet Nose . 25 feet Maximum Elevation 343.5 Minimum Elevation 341.5 Average Height . . . . . . . . . . . . . .. 5 feet Top Width . 8 feet Side Slopes 2H, 1V PERTINENT DATA Sheet 1 of 2 PERTINENT DATA Core Material . . Gravel Protection Cover Thickness Quarry Rock Revetment Length 1,660 feet Side Slope 2H, lV Average Height . 7 feet Fi" Material . . Gravel Protective Cover Thickness . 1.5 feet Quarry Rock Seeded 5 lope Length 740 feet Side Slope 3H, lV Average Height . . . . . . . . . . . . . . . 7 feet PERTINENT DATA Sheet 2 of 2 Para 1. 01 1. 02 1. 03 1. 04 2.01 2.02 3.01 3.02 4.01 5.01 5.02 ---------~--------------------------- TALKEETNA RIVER PROJECT, ALASKA DESIGN MEMORANDUM NO. 1 GENERAL DESIGN MEMORANDUM TABLE OF CONTENTS PERTINENT DATA SECTION 1 -PROJECT AUTHORIZATION Authority Project as Described in Project Document Local Cooperation Specified in Project Document Project History SECTION 2 -INVESTIGATIONS Preauthori zation Postauthori zation SECTION 3 -PUBLIC MEETINGS Preauthorization Postauthor i zation SECTION 4 -LOCAL COOPERATION Local Requirements SECTION 5 -LOCATION OF PROJECT AND THE RIVERS Proj ect Location The Rivers Page 1-1 1-1 1-1 1-1 2-1 2-1 3-1 3-1 4-1 5-1 5-1 TABLE OF CONTENTS (Cont) Para Page 5.03 Flood Plain Area 5-2 5.04 Erosion 5-2 SECTION 6 -PROJECT FORMULATION 6.01 Planning Concepts 6-1 6.02 Project Scope 6-1 6.03 Alternatives 6-2 6.04 Proposed Plan 6-9 SECTION 7 -BASIS FOR DESIGN 7.01 General 7-1 7.02 Hydrology 7-2 SECTION 8 -RECOMMENDED PROJECT PLAN 8.01 General 8-1 8.02 Design References and Criteria 8-1 8.03 Rock Dike 8-2 8.04 Graded and Seeded Bank 8-4 8.05 Bank Revetment 8-4 8.06 Construction Materials 8-4 SECTION 9 -DEPARTURES FROM PROJECT DOCUMENT 9.01 Departures 9-1 9.02 Reason for Departures 9-1 i i TABLE OF CONTENTS (Cont) Para SECTION 10-ENVIRONMENTAL CONSI DERATIONS 10.01 General 10.02 Existing Conditions 10.03 Environmental Impacts SECTION 11 -REAL ESTATE 11 .01 General Land Description 11.02 Land Acquisition SECTION 12 -PROJECT OPERATION AND MAINTENANCE 12.01 General 12.02 Annual Cost SECTION 13 -DESIGN AND CONSTRUCTION SCHEDULE 13.01 Genera I 13.02 Proposed Schedule SECTION 14 -COST ESTIMATES 14.01 Proposed Plan SECTION 15 -PROJECT BENEFITS 15.01 General 15.02 Benefit Analysis 15.03 Benefit-to-Cost Comparison iii 10-1 10-1 10-3 11-1 11-1 12-1 12-1 13-1 13-1 14-1 15-1 15-1 15-4 TABLE OF CONTENTS (Cant) Para Page SECTION 16 -DI SCUSSION 16.01 Genera I Comments 16-1 SECTION 17 -RECOM ENDATIONS 17.01 Recommendations 17-1 No. Follows P~ Aerial view of the confluence of t e Talkeetna and Susitna Rivers at Talkeetna, Alaska 5-2 2 View of fascine from upstream en as it appeared in May 1951 6-3 3 Fascine as it appeared in October 1971 6-3 Alternative Structural Improvem nts 6-4 Location Map 5-1 2 Stream gages and Quarry Site 7-2 3 Project Map 8-1 PLATES Plan 2 Plan and Sections 3 Profi I es and Deta i I iv TABLE OF CONTENTS (cont) EXHIBI S River Profi Ie 2 Fish and Wildlife Service Report 3 Matanuska-Susitna Borough Spo sorship Letter 4 Matanuska-Susitna Borough Lett r 5 Department of Transportation Le ter SECTION 1 -PROJECT UTHORIZATION 1.01 Author ity. The Flood Control ct of 1958 (Publ ic Law 85-500) authorized improvements for bank pr tection at Talkeetna, Alaska, as described in Interim Report No.2 - C ok Inlet and Tributaries, and printed in House Document No. 34, 8 th Congress, 1st Session. 1.02 Project as Described in Proje t Document. The plan of improve- ment set forth in the project documen calls for the construction of rock riprap bank protection along the left ank of the Talkeetna River, extend- ing 1,500 feet downstream from the r i Iroad embankment. 1.03 Local Cooperation Specified i document specifies that local interest Document. The project a. Provide, without cost to the United States, all lands, easements, and rights-of-way necessary for the construction of the project, b. Agree to hold and save the nited States free from damages due to the construction work, c. Agree to maintain the works after completion in accordance with Federal regulations. 1.04 Project History. The Rivers nd Harbor Act of 1948 authorized a study of the Cook Inlet and Tribut ries within Alaska. This study was related to water resource improvem nts within the study area for which the Talkeetna River and community f Talkeetna were included. The report resulting from this Rivers and Harbor Act included a recommendation 1- that a flood control project along the Talkeetna River at Talkeetna be constructed in the interest of erosion prevention. The report was printed as House Document No. 34, 85th Congress, 1st Session after the Chief of Engineers submitted his report to Congress in 1953. However, during the period of the above study and the sUbmission of that report to the Congress, an emergency bank protection project in the form of a fascine was constructed by the Army Corps of Engineers under Section 14 of the 191~6 Flood Control Act. The structure consi sted of timber tied in bundles and held in place with vertical railroad ties. The Flood Control Act of 1958 authorized the construction of the project recom- mended at Talkeetna in the House Document mentioned above. In 1960, the existin<;1 fascine was still functioning and the authorized project was classified as inactive. The timber in the emergency structure has deteriorated with time and has not been replaced and the fascine con- sequently no longer fUnctions as an effective erosion control device. The original sponsorship group no longer exists since Alaska became a state. With this deteriorated fascine, local interests requested assis- tance. ThE~ inactive authorized project was reclassified deferred for restudy in 1971 to reanalyze existing conditions. Herein is presented the restudy analysis. 1-2 SECTION 2 -INVESTIGATIONS 2.01 Preauthorization. Investigatio s made in preparation of the project document included a hydrogr phic analysis and material surveys. Office studies included various alter atives for quantities, cost estimates, and benefit analyses. 2.02 Postauthori zation. Additional investigations made in preparation of this report include topographic surveys, studies for a source of quarry rock, and coordination with local interests. Office studies include hydraulic analyses, quantity estimates, cost e timates, and a review of benefits. A reconnanissance trip and minor mat rial laboratory tests were accomplished for the proposed quarry site. In ad ition, cross-sections in selected locations were taken along the Talk etna River. These studies were also supplemented with the II Flood Plai n nformation, II Talkeetna, Alaska, report dated June 1972 by the Alaska Distr ct, Corps of Engineers. Included were sections taken across both the ITal keetna and Susitna Rivers, derived Intermediate Regional Flood and Sta~dard Project Flood flows, and backg round data. I I 2- SECTION 3 -PUBLIC MEETINGS 3.01 Preauthorization. No formal public meetings were held prior to authori zation of the initial 3.02 Postauthorization. he Id at Ta I keetna on 5 January 1973 to ascertain local i terest desires and to discuss various corrective actions. Local interests desi red add itional protection from floods and bank erosion along the alkeetna and Susitna Rivers. Methods discussed during the meeting incl dikes, bank revetment, and various alternative constructi n materials. Twenty-six people attended the publ ic meeting. The proposed project was coordinated with Federal, State, and local agencies. Inform I contacts, including workshops, with local officials and other interested local residents indicate that the community and the local sponsor are extremely concerned about erosion protection at Talkeetna. I 3t-1 SECTION 4 -OCAL COOPERATION 4.01 Local R_~guirements. Prior o construction, the project sponsor will be required to enter into a written agreement agreeing to the items of local cooperation listed in paragraph 1.03. At the time of this writing, the Matanuska-Susitna Borough is in the process of setting up a service area that wi II be the legally consti uted vehicle with full authority and capabi lity to perform the terms of ocal cooperation. This would then give the borough the ability to co ply with Section 221, PL 91-611. 4--1 I SECTION 5 -LOCATION IOF PROJECT AND THE RIVERS 5.01 Project Location. The commlunity of Talkeetna, Alaska, is situ- ated on the left bank of the Talkee+a River at its confluence with the Susitna River (see figure 1). The Icommunity is located about 115 mi les north of Anchorage, at mi lepost 22~ on the Alaska Rai Iroad and has a population of about 185 people (19JO census). This unincorporated com- munity serves as an important disrbution center to homesteaders, pros- pectors, trappers, and hunting-fi,hing-outdoor recreation enthusiasts. Supplies are distributed from Talkleetna by boats, airplanes, train, and trucks. Principal business estab'lshments include flying services, motels, hotels, lodges, and trading posts. Other business enterprises include bars, cafes, and curio shops. Talkeetna is a critical Alaska railroad bridge! site as well as a depot. Other govkrnmenta I faci I ities include important / FAA air-navigational facilities, a ost office that serves over 1,000 people, road maintenance shops and facili ies, and two new schools. A paved highway now connects Anchorage with Fairbanks and a new paved spur connects Ta Ikeetna with the paved IhighWa y which allows easier access to the Talkeetna Area. I 5.02 The Rivers. The Talkeetn4 River is about 80 miles in length with a drainage area of about 2,015 sqlare miles. The Susitna River has a length of about 200 mi les and a dr inage area of about 11,035 square miies upstream of Ta Ikeetna. Both of t1ese 9 lacier-fed rivers are meanderi n9, I I I 15-1 '. ··':a"..:' -~ .' ;,' .. I"; ~; .. , . . ~-.-". .. o 1/2 I ~3.-:=F.::;::j MILES .----~~--_J.~" GENER,!I,L DESIGN MEMON'ANDUM TALKEETNA RIVER PROJECT ALASKA ' LOCATION MAP ALASKA DiSTRICT, CORPS GF ENGINE~P.S ANCHORAGE,ALASKA FEBRUARY 1975 braided and subject to high runoff. 5.03 Flood Plain Area. Talkeetna is susceptible to inundation from both the Talkeetna and the Susitna River with out-of-bank flows occurring at flood stages of lS-year and 2S-year frequency recurrence intervals, respectively. While the Alaska Rai Iroad embankment and bridge structure provides partial low flow protection through volume detention, runoff exceeding a 70-year frequency-flood would overtop the ra i I road fi II, flooding Talkeetna from the back side. The flood plain is occupied by a railroad, roads, streets, utilities, homes, businesses, historical structures, and government facilities which would be damaged by a major flood. 5.04 Erosion. Flood flows causing bank erosion occur annually on both the Talkeetna and Susitna Rivers. While the timber fascine has provided partial protection along the Talkeetna River, the lower portion of town has been under excessive attack from both river flows. Even with emergency construction efforts by the local residents, land loss has still exceeded 800 feet width since 1917 with an average loss of 10 feet per year along the left bank in recent years. This annual loss has resulted in much damage to land and personal property, and has caused numerous bui Iding relocations. With the gradual deterioration and recent failure of portions of the fascine, the community is now in immediate danger of a greatly accelerated erosion rate. This erosion wi" also augment the flow attack problems along the Susitna reach. 5-2 Photo 1 . Aerial view of the confluence of the Talkeetna and Susitna Rivers at Talkeetna, Alaska (Corps of Engineers Photo, July 1974.) SECTION 6 -PROJECT FORMULATION 6.01 Planning Concepts. To insure that a project would result in the optimum plan of improvement, meeting the desires of local interest within restraints imposed by existing laws and regulations as well as criteria and parameters existing to the particular site, a restudy of the authorized-unconstructed project commenced in FY 73. This restudy found that flooding and land erosion is continuing along the left bank of the Talkeetna River and along the left bank of the Susitna River adjacent to the community of Talkeetna. In addition, it was found that the existing timber fascine, constructed as an emergency measure in 1951, was deterio- rated. Solutions considered to alleviate the flooding and erosion situation included both structural and nonstructural methods such that: (1) the proposed project should confirm or modify the authorized project as indi- cated in the project document, (2) the proposed project should be accept- I able to desires of local interest such that local interest would support the project and agree to specified items of local cooperation, (3) the project should be engineeringly feasible and have economic justification and not significantly degrade the environment or have adverse effects on the social structure of the area. 6.02 Project Scope. The project was scoped to be a complete within itself project such that no additional work would be required to assure effective and successful operation, excepting minor maintenance. In 6-1 addition, the scale of the project wou Id provide a max imum excess of benefits over costs where possible. The views and comments of inter- ested agencies as well as those of local interest would be considered. 6.03 Alternatives. Within the project formu lation process, various alternatives were studied to ascertain the most feasible project consis- tent with sound environmental, economic, and engineering principles. Structural and nonstructural alternatives were considered in the evaluation to obtain a project formulation consistent with existing laws and regulations. 1. Structural. Structural developments are considered to be developments to reduce bank erosion and to provide barriers against bank erosion. Complete structural flood protection against 1 OO-year and standard project flood for the community was considered but would require levees around four sides of the community plus an interior drainage system. Protection in the form of levees and interior drainage system would not be economically justified and was not considered in further detai I. A lesser degree of protection up to the protection afforded by the existing rai Iroad embankment, about a 70-year frequency flood, would require a levee along two sides of the community plus an interior drainage system. This form of lesser flood protection is not economically justified 6-2 and was not considered in further detai I. Protection in the form of bank erosion was considered, and it was found that some methods could be economically justified depending on the scope of the project and con- struction materials utilized. Various methods and degrees of bank protection were studied including dikes or levees, groins, bank revetment, and soi I stabi I i zation. I n addition, various materials for construction were considered including timber, river sand and gravels, quarry stone, and river rocks. Timber structures were estimated on a 20-year physical life; gabions on a 40-year physical life; with sand, gravel, river rocks and quarry stones having at least a 50-year physical life. Annual maintenance was an additional factor. Four alternative designs are included for structural land protection. a. Rehabi I itate the Existing Fasci ne. The townsite of Tal keetna is suffering from bank erosion behind the fascine because the fascine was not maintained and thus deteriorated. This alternative would replace the deteriorated timber logs between the steel pilings and extend the fascine with like materials about 1,500 feet downstream. The rehabilitated fascine would again provide protection from bank erosion by the Talkeetna River as well as additional protection from the waters of the Susitna River. Environmentally, this alternative is acceptable and would provide the same protection as the proposed project. While 6-3 Phot o 2. View of fascine from upstream e n d as it appeared in May 1951. ( Corps of Engineers Photo. ) Photo 3. Fascine as it appeared in October 19 71. (Corps of Engineers Photo) 1204-7 5 little or no vegetation would be removed, significantly more river habitat would be covered by this alternative than by the proposed project. Greater quantities of construction material than in the proposed project would also be required. The higher annual cost of this alterna- tive produced a lower benefit-to-cost ratio than did the proposed plan (table 1). Therefore, this alternative was not chosen. b. Groins. This alternative would consist of a 600-foot dike, paralleling the existing fascine, and two L-shaped groins project- ing riverward from the left bank of the Talkeetna River past the end of the dike. The dike and groins would be constructed by using sand and gravel from the riverbed with quarry stone for an outer protective shell. The dike and groins would function to redirect flows away from the eroding bank. Deposition of material would occur in front of the groins. Environmentally, this alternative is acceptable. This alternative would alter the river morphology of the Talkeetna River; however, because of the normal fluctuating channel and flow conditions of the Talkeetna River, no adverse environmental impact would be antici- pated. Greater quantities of construction material than required for the proposed project would be necessary to complete the construction of this alternative. The higher annual cost of this alternative produced 6-4 TABLE 1. ALTERNATIVE STRUCTURAL IMPROVEMENTS -TALKEETNA, ALASKA AL TERNATIVES RECOMMENDED PROJECT DESIGN NO 2400 L.F. * 600 Ft. DIKE & 2400 L.F.* 2400 L.F.* DIKE, GRADED & SEEDED CONSIDERATION IMPROVEMENT LOG FASCINE GROINS GAB IONS ROCK DIKE BAl.'Th REVETMENT Project Area 80 acres 80 acres 80 acres 80 acres 80 acres Economically Feasible Not Rated YES YES YES YES YES Environmentally Acceptable YES YES YES YES YES YES Design Life N/A 20 yrs 50 yrs 40 yrs 50 yrs 50 yrs Construction Costs NONE 337,000 628,000 658,000 676,000 426,000 Amortized Costs ** N/A 29,100 39,200 43,000 42,100 26,600 Annual Maintenance Cost N/A 2,000 800 1,000 800 800 Annual Cost N/A 31,100 40,000 44,000 42,900 27,400 Benefits *** N/A 32,000 32,000 12,000 32,000 12,000 BIC Ratio N/A 1.03 .80 .72 .74 1.2 'k Linear Feet 5-7/8 Interest *** Minor Variances in EDA benefits are not included. a lower benefit-to-cost ratio than did the proposed plan (table 1) . Therefore, this alternative was not chosen. c. Gabions. This alternative would consi st of 2,400 feet of gabions constructed along the left banks of the Talkeetna and Susitna Rivers. The gabions would consist of wi re baskets fi lied wi th quarry rock, as it would be costly to separate cobbles and stones from the riverbed. The gabions would stabilize the left banks of the two rivers and would pre- vent flows from eroding the bank. Environmentally, this alternative is acceptable. This alternative would alter the ri ver morphology of the Talkeetna and Susitna Rivers; however, because of the normal fluctuating channel and flow conditions of the Talkeetna and Susitna Rivers, no adverse environmental impact would be anticipated. The higher annual cost of this alternative pro-' duced a lower benefit-to-cost ratio than did the proposed plan (table 1) . Therefore, this alternative was not chosen. d. Dike. This alternative would provide a continuous dike con- structed along an alinement about 100 feet riverward from the existing left bank of the Talkeetna and Susitna Rivers. The dike would be constructed of sand and gravel excavated from sandbars in the rivers and would be protected by quarry stone from a designated quarry si te. This alternative would prevent bank erosion due to the Talkeetna and 6-5 Susitna Rivers and, depending on dike design, would provide flood protection from floodwaters in both rivers. This alternative would probably have the greatest impact on the envi ronment as compared to the rest of the alternati ves due to the si ze of the project in relation to esthetics, river morphology, and quantity of material requi red for construction. However, thisal ternative would provide both flood and bank erosion protection to the community of Tal keetna which would have a beneficial impact on the commun ity. The higher annual cost of this alternative produced a lower benefit to-cost ratio than did the proposed plan (table 1). Therefore, this alternative was not chosen. 2. Nonstructural. Nonstructural methods are considered to be other procedures for reducing bank erosion and damage potential s. These include no protective construction, relocation of the town of Talkeetna, and zoning and building ordinances. a. No Construction. Providing no protective construction would result in continuing and possibly escalating bank erosion of the town- site of Talkeetna, continuing loss of vegetation and animal habitat due to bank erosion, and eventual loss or damage to buildings and struc- tures (i.e., homes, motel, barn, several historical buildings, camping area, utilities, road). By not disrupting the influences of the Talkeetna 6-6 and Susitna Rivers on the community, these rivers would continue their encroachment and flooding actions on the townsite. These actions would continue to affect the water qual ity of these two rivers and even- tually would alter their river morphology. Environmentally, this alternative is acceptable and would eliminate the adverse impacts associated with the proposed plan. The Talkeetna and Susitna Rivers would be allowed to continue in their naturally fluctuating channels within their flood plain. However, abandonment of the project would not necessari Iy assure the return of the area to natural conditions. Local people may institute some improvement measures on their own. I nauguration of flood-plain zoning with flood- proofing of existing buildings, appropriate building codes, relocations, and other appropriate land use practices could decrease the disrupting influences of flood and bank erosion. b. Relocation. This alternative would be the relocation of structures and utilities at Talkeetna that could be damaged by bank erosion and flood ing from the Ta Ikeetna and Susitna Rivers to another location that would have a lower probabi I ity of damage than the present location. This alternative would have a desirable impact on the Talkeetna and Susitna Rivers and the adjacent area as relocation would allow the rivers to continue along their natural course. Also it would remove the 6-7 community from an area in which the town is naturally and habitually subjected to bank erosion and flooding from the two rivers. The relocation process would extend over many years and would be governed by existing regulations. While this would probably be economically feasible, it is socially unacceptable because the people of Talkeetna do not want to move. Furthermore, it would result in prob- lems of compensation for land that would be zoned as nonusable and for relocation of buildings that have not yet served their complete economic life. In addition to these problems that would have to be solved, a more basic problem is the fact that neither the community nor the Matanuska- Susitna Borough have the authority necessary to implement this action. Since this solution remains as being basically only academic and at present not practical, no detai led studies or comparative analyses were conducted. Examination of immediate relocation was determined uneconomical. c. Zoning Ordinances. The zoning ordinance alternative fits into the larger category of flood plain management. The community of Talkeetna is not incorporated and hence does not have the power to zone. The Matanuska-Susitna Borough does not have area wide regulatory power for flood control. However, the local citizens could apply flood plain management principles to the land endangered by bank erosion. This alternative would have a beneficial impact on the Talkeetna and Susitna 6-8 Rivers because no new construction would occur in or wou Id alter the river. This alternative would have an undesirable impact on the community of Talkeetna by allowing continuing bank erosion and the subsequent loss of lands, vegetation, and anima I habitat, which the proposed plan has been designed to prevent. 6.04 Proposed Plan. The proposed plan is an erosion control structure consisting of 600 linear feet of dike extending downstream from the rail- road bridge forcing the Talkeetna River flows away from the bank, 740 I inear feet of grading and seeding immediately downstream from the rai 1- road embankment, 1,660 linear feet of rock revetment along the Talkeetna and Susitna Rivers. This plan is discussed in the following sections. 6-9 SECTION 7 -BASIS FOR DESIGN 7.01 General. a. Talkeetna is situated on the left bank of two rivers, at the confluence of the Talkeetna River with the Susitna River. An Alaska Railroad bridge spans the Talkeetna River about 1,500 feet upstream of the Susitna River. In 1949, the Alaska Rai Iroad agency initiated a channel improvement project upstream of the bridge, blocki ng meanders and excavating new channels to direct the flow perpendicular to the bridge. In 1951, the Corps of Engi neers constructed 1,000 feet of timber fasci ne below the bridge to continue the straight channel al inement and thereby, directed flow away from the left bank of the Talkeetna River and the Talkeetna townsite. Presently, the channel above the railroad bridge is much the same as before the channel improvement project with an increasing quantity of flow approaching the bridge at an angle, directing flow towards the fascine. The fascine has been breached in severa I areas and has deteriorated to the extent that it is no longer effective. Below the confluence of the Talkeetna River with the Susitna River, a serious bank erosion problem exists at the west end of the townsite. b. Soi Is and Geology. The Talkeetna area geology consists of an alluvial plain of sandy gravels. Along the river bottoms, stream flows 7-,1 have concentrated gravel and shingle rocks in small quantities up to about 4 inches in diameter. No bedrock outcrops existing in the immediate vicinity. Drainage Areas. The Talkeetna River and the Chul itna River are the major tributaries of the Susitna River. The Talkeetna River, which encompasses total drainage area of 2,015 square miles, has its origin at the Talkeetna Glacier in the Talkeetna i\10untains. The areas above Talkeetna drained by the three rivers range from 350 feet to over 6,000 feet in elevation. All have portions of thei r higher elevations covered by glaciers. Locations Talkeetna River at Mouth Susitna River at Talkeetna River Length (M iles) 80 200 Drainage Area (SM) 2,015 11,035 d. Climate. The area is characterized by moderately warm summers and cold winters with temperature extremes ranging from +91 0 F to -480 F. Annual precipitation averages 28.8 inches and annual snowfall 114 inches. Rainfall is generally the heaviest in July, August, and September with monthly precipitation amounts about equal for the rest of the year. 7.02 Hydrology. a. Data Sources. The U. S. Geological Survey has maintained stream gages (see figure 2) at the following locations upstream from Talkeetna for the periods indicated below: 7-2 ~--------~- NUSt<A-SUS'" MATA UGH sORa ~~~TL..e . .-.-,l:~'.c," ;~. ~ 'C':"l, \ \ :~_~(~\V 'J~.~: ~ I II 11,.,,-., • "';~~-~:""J .n~-::t-: -S:---1.._~_--.j(1-___ .l-2~~~;::~=-=~=-:;~~r~"':::~~!:~~JlIwl:=====:fJ STREAM GAG~S: AI TALKEETNA R!VER ABOVE TALKEETNA QUARRy:a4 MONTANA CREEK QUARRY A 2 CHULITNA RIVeR NEAR TALKEETNA STREAM GAGES AND QUARRY SITE. A:3 SUS/TNA Ri Yl:R AT GOLD CREEK FIGURE 2 I Locations Susitna River at Gold Creek Chulitna River near Talkeetna Talkeetna River above Talkeetna Period of Record August 1949 -Present February 1958 -Present June 1964 -Present To supplement the records of the gaging stations and those of snow surveys with more information concerning past floods, newspaper files and hi storical documents were reviewed. b. Past Floods. Major floods have occurred in the study area during spring, summer, and fall seasons. River stages can rise from normal flow to extreme flood flow in a relatively short time. The largest known flood occurred in September 1942, resulting from 48 hours of heavy rains in the mountains, and associated glacial melt. The Talkeetna River rose more than 6 feet, flooding homes and businesses in Talkeetna with 2 feet of water. In August 1971, a flood occurred (estimated to be about the 20-year frequency event) resulting in considerable bank erosion and flooding at the west end of the townsite. c. Design Floods. Intermediate reg iona I and standard project flood s for the Talkeetna River near Talkeetna and the Susitna River at Talkeetna were developed for use in the Talkeetna Flood Plain Information Report published in June 1972. Design flows with a 50-year recurrence interval were developed from statistical analysis of streamflow records. These flows a re tabu lated be low: 7--3 Flood Frequency Standard Project Intermediate Regional 50-Year Talkeetna River 3usitna River at mouth at Talkeetna 121,000 c. f. s. 97,OOOc.f.s. 84,000 c. f. s. 31 5, 000 c. f. s. 268,000 c. f. s. 243, 000 c . f. s. d. Des ign References and Criteria. The 50-year flood in the Talkeetna River (84,000 c.f.s.) with a Susitna River flow of 243,000 c.f.s. below the confluence of the Talkeetna and Susitn<l Rivers was used as the design criteria for the Talkeetna dike and bank improve- ments. The 50-year Susitna River flow of 243,000 c. f. s. was used as the design criteria for the Susitna bank revetments. 7-4 SECTION 8 -RECOMMENDED PROJECT PLAN 8.01 General. T.he recommended plan as shown in figure 3 is a com- bination of control methods. This was determined to be the most eco- nomical approach to the erosion problems attributable to the Talkeetna and Susi tna River. The plan consists of a 600-foot-long dike extending downstream of the railroad bridge for directional control of the Talkeetna River. Since the dike will be overtopped, 740 feet of the bank along the Talkeetna townsite will be graded and seeded for low velocity erosion protection. Downstream of the seeded area, the bank is subject to erosion from both the Talkeetna and Susitna Rivers. Joining the seeded bank and continuing 1,660 feet downstream, riprap bank revetment is recom- mended. 8.02 Design References and Criteria. a. HEC-2 Water Surface Profiles Computer Program 723-02A was used to determine water surface elevations and velocities. Mannings IInll values used in the program are .030 for the channels and. 1 5 for the overbank areas. b. Revetment stone gradation and course thickness weredetermine<;l in accordance with EM 1"0-2-1601, ETL 1110-2-120, and HDC 712-1. Revetment thicknesses were increased to allow for ice and debris impact. c. Scour computations were made using the formula prepared by T. Blench and Associates, Ltd., for Alyeska Pipel ine Service Company. 8-1 I N .~< .. :=1 ===!I ~I ====~ I MAIN sus/rNA RIVER nf1nJ u iU U:lL.:=:::::::: NOTE: PROPOSED DISPOSAL LOCATION IS THE AREA 8ETWE EN THE PROPOSE D OIKE AND THE LEFT BANK OF THE TALKEETNA IL K E N ~======~i ~j======~i ir---~ FEET 200 0 200 400 600 J H H E----I ::::oJ GENERAL DESIGN MEMORANDUM TALKEETNA RIVER PROJECT. ALASK A PROJECT MAP ALASKA DISTRICT CORPS OF ENGI NEERS ANCHORAGE, ALASKA FEBRUARY 1975 This formula was concurred in by the Corps of Eng ineers for Alyeska pipeline river crossi ngs. 2/3/ 1/3 ds = (q Fbo ) x scour factor in which ds means depth from some standard flood elevation to the average estimated bed in a cross section. q = total Q/channel width IIW Il = c. f.s. per foot of width DM means the median size by weight, in millimeters, of a bed sample believed to be representative. Scour factor = 1.35 on straight channels x 1.20 for unforeseens. d. The 50-year flood in the Talkeetna River (84,000c.f.s.) with the 50-year Susitna River flow (243,000 c.f.s.) was used as the design criteria for the Talkeetna dike and bank improvements and the Susitna bank revetments. Thi s is consistent with the expected life of rock revetment type of construction. The river profiles are shown on exhibit 1. 8.03 Rock Dike. The GOO-foot long dike averages about 5 feet high and has a top width of 8 feet. A gravel core with armor facing at lV on 2H side slopes is planned. Material excavated for the buried toe wi II be used as core embankment. Excess material wi II be used as fill for bank improvements or will be wasted in the channel adjacent to the graded and seeded bank. The top elevation of the dike wi II 8-2 slope from elevation 343.5 at the railroad bridge to elevation 341.5 at the lower end. Overtopping wi II occur at design flow in the Talkeetna River. Since the lower slope of the dike is greater than the slope of the water surface profi Ie; overtopping, as the water surface rises, will gradually proceed upstream. This will tend to reduce the head differential across the dike and will decrease overtopping veloc- ity. Maximum overtopping velocity was computed to be 6.5 f.p.s. Profi les of the design floodwater surface with respect to the dike are shown in plate 3. The channel side of the dike for the first 50 feet below the railroad bridge is designed to withstand a computed veloc- ity of 15.8 f.p.s. This section is protected with 42 inches of riprap. Between stations 0+50 and 2+50, 30 inches of riprap are provided to protect against a velocity of 12 f. p. s. From station 2+50 to the end of the dike, 24 inches of riprap are provided for protection against velocities of 10 f.p.s. Sections and riprap gradations are shown in plate 2. Scour depths corresponding to velocities along the dike were computed and sufficient rock wi II be placed at the excavated toe to provide design armor thickness to the computed scour depths on a 1V on 2H slope. An 18-inch layer of quarry run rock will be carried over the top and back slope of the di ke and an apron provided at the toe of the back slope to prevent scour. Plate 2 shows dike sections and riprap gradations. 8-3 8.04 Graded and Seeded Bank. When the dike is overtopped, veloci- ties along the upper bank at the Talkeetna townsite will be slightly less than 5 f.p.s. Seven hundred and forty feet of the bank will be graded to a lV on 3H slope and will be seeded to withstand these velocities. A seed-fertilizer-mulch mixture will be distributed on 4 inches of topsoil (plate 2) . 8.05 Bank Revetment. Extending 1,660 feet downstream from the graded and seeded bank, riprap revetment continues around the left bank of the Susitna River. Average height of the bank revetment is 7 feet. The computed water velocity of 7 f. p. s. was used for riprap design. An 1 a-inch revetment thickness is adequate to withstand this velocity plus ice and debris impact. The toe will be buried a minimum of 7 feet and wi II be weighted with sufficient material to provide the design, revetment thickness to computed scour depth. Material exca- vated for the toe burial will be used to dress the upper slope. Quarry run revetment stone reasonably graded and up to 18 inches in diam- eter is recommended for slope protection below the design water sur- face elevation (see plate 3) or top of submerged banks. Banks extend- ing above the water surface will be graded, top soiled and seeded to vegetate bare or disturbed surfaces. 8.06 Construction Materials. Sand, gravel, topsoi I, silt, and quarry rock are available in the area. 8-4 a. Materials at Site. Sand and gravel s from excavation for toe riprap wi II meet major requirements. Minor add itional sand and gravel for filter blankets and bank grading can be obtained from river bars. Topsoi I can be acqu ired on top of the banks along the river. b. Quarry Rock. Quarry rock is available from an Alaska High- way Department Quarry located along the middle fork of Montana Creek (see figure 2). The only other rock nearby is at Curry, on the Alaska Railroad route, about 25 miles north of Talkeetna. This location was investigated for a rock source for other projects .. It was learned that additional quarry work at Curry would require relocating the rail- road, the cost of which is prohibitive. (1) Haul Road. The haul road includes 11 miles of paved high- way south from Talkeetna to East Sunshine Lake. From the lake, an improved road heads east by northeast 3 miles to Montana Creek. Crossing the north fork, the improved road continues to the middle fork of Montana Creek where it follows the creek bottom 3 miles or more upstream to the quarry. Travel is restricted to winter operation, usually after 15 December. (2) Quarry Rock. The quarry rock is a medium to fine grained quartz diorite with accessory biotite. Rock from this source will meet the sizes required by careful blasting. Adequate rock appears to be available, but no estimate of reserves will be forthcoming until explor- atory test pitting or drilling is accomplished to establish the dimensions of usable rock. 8-5 SECTION 9 -DEPARTURES FROM PROJECT DOCUMENT 9.01 Departures. The project plan as described in the project document had rock revetted s lope protection extending 1,500 feet downstream from the railroad bridge and constructed on the existing left bank of the Ta I keetna River. The mai n departures in the proposed plan from the project document are the additions of a 600-foot dike, 740 feet of grading and seeding, and the extension of the bank protection further downstreatm to afford protection from the Susitna River. 9.02 Reason for Departures. The reasons for departures from the project document plan fall into categories of changed erosion conditions, as well as additional protection desired. As the Talkeetna River has again shifted to skewed flow pattern through the bridge, the authorized bank revetment by itself was considered inapproppriate to meet the present con- dition of flow pattern and desi red protection. The di ke downstream of the rai Iroad bridge is to direct flows through the bridge opening and to prevent direct attack by the Talkeetna River on the community. The graded and seeded protection is to provide bank stabi lization from river overdike flows. Extending the authorized bank revetment further downstream is to provide the community additional erosion protection from the Susitna River. 9-1 SECTION 10 -ENVIRONMENTAL CONSIDERATIONS 10.01 General. The purpose of this section is to review the impact of project construction along the left banks of the Talkeetna and Susitna Rivers at Talkeetna, Alaska. This analysis is composed of two parts; a review of existing conditions and resources, and a commentary on envi ronmenta I impacts to be expected from the proposed project. Sources of information include reports of Federal and State agencies, comments of interested citizens, and onsite observations by Corps of Engineers per- sonnel. A draft environmental impact statement was filed with CEQ on 9 May 1974. Exhibit 2 is the Fish and Wildlife Service report. 10.02 Existing Conditions a. Wilderness Areas and Wild and Scenic Rivers. The Talkeetna area is not located with a designated wi Iderness area, nor have any of the streams in the area been proposed for inclusion in the wi Id and scenic rivers system. b. Historical and Archeological Sites. Exami nation of the National Register of Historic Places, as required by the National Historic Preser- vation Act of 1966, indicates there are no officially designated archeological or historical sites within the project area at Talkeetna. At the present time the State recognizes prt of the Talkeetna area as the Talkeetna Historic District. This district includes the original townsite, the Alaska Railroad right-of-way and reserve, and the cemetery reserve. At this time, the Talkeetna Historic District is in the process of being proposed as a Fede:~3: 10-1 Historic District to be placed on the National Register. The project area does not involve the removal or elimination of any of these historic sites or structures. c. Vegetation. The vegetation of the Talkeetna area consists of intermixed forest and muskeg. Overstory in the immediate project area is composed primari Iy of paper birch, cottonwood, wi lIow, and alder. Understory in the immediate project area is composed primarily of yarrow, sorrel, fireweed, clover, horsetai I, and cow parsnip. d. Mamma Is. Terrestrial wi Idl ife I iving in the project area would include only sma II mamma Is such as voles and lemmings because the close proximity of the human community has caused big game species to avoid the area. e. Birds. Habitat in the project area is ideal for a variety of song birds. f. ~ish. Major spawning runs reach the upper headwaters and streams of both the Ta Ikeetna and Susitna Rivers. Spring, summer, and fall seasons support heavy migrations of spawning chinook (king), sockeye (red), coho (silver), pink (humpback), and chum (dog) salmon. No steelhead trout are known to frequent the Talkeetna or Susitna Rivers. Ra inbow trout, Dolly Varden, and grayl ing are resident species of the two rivers. They begin their mass migration in early spring after winter- ing in the Susitna River and lower end of the Talkeetna River. Whitefish 10-2 TABLE 1. Talkeetna and Susitna Rivers Fisheries Data Spec ies Chinook Coho Pink Chum Sockeye (spring run) (summer run) Ra inbow Trout Dolly Varden Grayling Adult Fish Return Mid-May -1 July Mid-July -December 1 July -September 1 July -September Mid-May -1 July July 1 -September Mid-April Mid-April April Smolt Migration May -June May -June March -April March -April May -June May -June May -June March -Apri I and burbots (ling cod family) exist in large numbers in the Talkeetna and Susitna Rivers. However, no data are available on the migration and/or spawning habits of these two species. g. Rare and Endangered Species. According to the published list, "Rare and Endangered Fish and Wildlife of the United States, II issued by the Fish and Wildlife Service, there are no rare or endangered wildlife or fish species known to inhabit the project area. 10.03 Environmenta I Impacts. The environmental impacts associated with the construction of the proposed project can be categorized under five basic categories: project construction, river morphology, quarry excavation, water quality, and human ecology. a. Project Construction. Identifiable impacts resu I ting from project construction are: 10-3 1. Loss of about 2 acres of river habitat and shrub vegetation. 2. Removal of about 11,000 cubic yards of in situ material. 3. Temporary increase in water turbidity during construction operations. 4. Temporary increase in noise during construction operations. 5. Visual impact of structural measures. 6. Provide bank stabi I ization, protection from bank erosion by floodwaters of the Tal keetna and Susitna Rivers. b. River Morphology. Construction activities are not anticipated to effect erosion downstream of the project, to disrupt river currents or flow characteristics of the Talkeetna and Susitna Rivers .. The proposed project would prevent bank erosion. c. Quarry Excavation. Project construction would necessitate removing approximately 10,000 cubic yards of stone from a designated quarry site. Two existing quarry sites have been located. One quarry is located about 20 mi les north of Talkeetna at Curry. The quarry is situated adjacent to the railroad and is owned by the Alaska Railroad. The other quarry is located about 15 miles south of Talkeetna along Montana Creek's middle fork. This quarry is owned by the State High- way Department and has tentatively been selected as the source of quarry rock. Temporary distrubance to terrestrial animals that inhabit 10-4 the surface of the quarry and adjacent areas wi II occur due to vegetation removal, rock blasting, and quarry excavation. d. W?ter Quality. The water quality of the Talkeetna and Susitna Rivers would be affected by increased turbidity resulting from excava- tion and construction activities. The increase in water turbidity of these rivers would be temporary and is not anticipated to prove detrimental because these rivers are naturally very turbid during the time opera- tions are scheduled to commence, and these rivers also naturally experi- ence extreme fluctuations in sediment concentration throughout the year. e. Human Ecology. The proposed project wou Id have a beneficial impact on the community of Talkeetna by providing bank erosion pro- tection from the floodwaters of the Talkeetna and Susitna Rivers. This would result in reductions in property damage and loss for the com- munity of Talkeetna. Identifiable impacts resulting on human ecology arc: 1. Route and mode of transportation would introduce a safety hazard as well as undesirable traffic conditions on the community of Talkeetna. 2. Ai r pollution due to dust generated by the increased travel of haul trucks. 10-5 SECTION 11 -REAL ESTATE 11 .01 General Land Description. The community of Talkeetna is not incorporated and therefore has no zoning powers. Lands involved in the project construction are under the direction of the Matanuska- Susitna Borough which will act as the local sponsor of the project. Lands required for construction is less than 1.5 acres. Ingress and egress to the exisitng quarry site on Montana Creek are via an existing road, part of which crosses private land. Easements for construction purposes wou Id also need to be obtained. 11 .02 Land Acquisition. The Federal Government is to be provided a II of the lands and rights-of-way necessary for the construction of the project. The project sponsor has indicated agreement to provide without cost to the United States all lands, easements, and rights-of-way for construction of the project by letters of 6 December 1973 (exhibit 3) and 4 December 1974 (exhibit 4) . The Matanuska-Susitna Borough, which has assumed the respon- sibility of local interests, will be instructed to obtain applicable inter- ests in the lands required for the project. No problem is expected for the borough to obtain acquisition of privately owned lands, as these are owned by advocates for bank protection. Governmental lands are also expected to be acqui red by the borough, as this land would also have bank protection. The project sponsor is to comply 11-1 with PL 91-646, as appropriate, which in part provides that a land appraisal must first be obtained and the landowner offered an amount not less than such appraised value. Ownership of the required lands will remain in the sponsor for operation and maintenance. The cost of acquiring the required lands, easements, and rights-of-way is estimated at $11,000. 11-2 SECTION 12 -PROJECT OPERATION AND MAINTENANCE 12.01 General. One annual inspection is required, preferably during low flows, to examine the toe of the dike and revetment. Usually, the optimum time is just after the spring thaw or just prior to the first snow- fall when the ground is clear of snow and ice. Special inspections shall be scheduled immediately after a severe flood condition has ended. Dike and revetment quarry riprap shall be repaired promptly if rocks are dislodged by floating debris, or if other types of failure should occur. Erosion repairs, reseeding, refertilizing, or wetting shall be accomplished, as necessary, to keep the graded and seeded bank grass root structure alive and intact. Since there are no operational controls on the project, the project wi II function by itself during flooding. Main- tenance will be the responsibility of the Matanuska-Susitna Borough. 12.02 /\nnual Cost. Minimum repair and maintenance costs depend upon schedul ing adequate inspections followed by prompt repai rs. a. Inspections. One annual inspection during low water is essential and the results would include a written report. One postflood inspection is considered reasonable based on a 10-year average. b. Maintenance and Repai rs. Repai r cost for ri prap replacement was assumed for two impact dislocations that could occur twice within the 50-year economic life of the project. Repair material is to be available 12-1 from riprap stockpiled for maintenance use. The seeded bank is expected to require the annual addition of some seed, fertilizer, and water to maintain a good root system. c. Estimated Costs. (1) Annua I inspection with report (2) Annua I cost of 10-year frequency inspection and report at $500 each event (3) Annual cost of riprap repair costs for 2 each $7,500 repairs at 20-year frequency floods (4) Annual cost, graded and seeded bank maintenance (5) Total estimated annual costs 12-2 $250.00 50.00 300.00 200.00 $800.00 SECTION 13 -DESIGN AND CONSTRUCTION SCHEDULE 13.01 Genera I. The existing erosion problem at Talkeetna urgently requires that construction be started at an early date. With completion of plans and specifications by November in the fi rst fiscal year, adver- tising and opening of bids can be accompl ished so that award can be made by the middle of December. 13.02 Proposed Schedule. Dike and revetment construction could be I imi ted to periods of low riverflow which normally occur between 15 August through 15 May. Excavation and grading are usually limited to times the ground is unfrozen, commencing early in June to 30 October when subzero temperatures are possible. Ten-year snowfall records indicate minimal snowfall is anticipated through ~~ovember. At the lowest riverflows in September, excavation for the riprap toe is expected to be in several feet of water. For below water riprap fill, the placing of riprap may have to be made concurrently with the excavation to prevent sand from running into the excavation. A further considera- tion is that the Montana Creek Road to the quarry, which traverses close to 3 miles of streambed, is usable by equipment usually during the period of December through /'vlarch when the ground is frozen. In view of the above time sequences, the contractor may have to quarry, haul, and stockpi Ie the riprap stone during the winter for use in later 13-1 construction of the project. An alternative method wou Id be to locate and develop another quarry or allow the contractor to furnish approved quarry stone. Considering the conditions observed and expressed above, award of a contract by December with project completion within 11 months appears to be a realistic time frame. The following bar chart illustrates a proposed schedule. PROPOSED CONSTRUCTION SCHEDULE Contract Award Quarry Operation I--~~-I-_ Stockpiling at Site Site Construction Initial River Bottom Inasmuch as the Susitna River is considered a navigable waterway to its confluence with the Talkeetna River it will be necessary prior to initiation of the proposed work, to process a Department of the Army authorization for the construction in accordance with rules and regu- lations published as 33 CFR 209.145 "Disposal of Dredged Material in Navigable or Ocean Waters. II 13-2 SECTION 14 -COST ESTIMATES 14.01 Proposed Plan Work Feature Mobilization & Demobilization 1 600' Dike: Site Preparation 1 Toe Excavation & Backfil13,430 Toe Excavation & Unit Job Job C.Y Unit Price L. S. Subtotal L.S. $ 3.00 Disposal 1,440 C.Y. 2.50 Quarry Stone Riprap 4,573 C.Y. 30.00 ...:-"-~""'.' .. > (42" to 18" Thickness) (includes 50 c.y. stockpile) .. ~.~ Subtotal 1660' Bank Revetment Grading 1 Job L.S. Toe Excavation & Backfill 2,830 C.Y. 3.00 Toe Excavation & Slope Use 3,280 C.Y. 2.50 Pit Run Riprap 4,640 C.Y. 25.00 (18" thickness) (incl udes 50 c.y. stockpile) Subtotal 740' Grade and Seed Bank Grading 1 Job L.S. 4" Topsoil & Seed 19,600 S.F. 0.25 Subtotal 400' 1 Lane Access Road with Turnourts Clearing 3 Acres 1,500.00 12' Top Width, Strip & Gravel Contingencies (10%) S&A Plans and Specifications Federal Cost Non-Federal Cost 2,400 L.S. 6.00 Subtotal Subtotal for Work Features Estimated Contract Amount Rounded Lands, Easements, Rights-of-Way, etc. (Project Sponsor) Total Project Cost 14-1 Amount $30,000 30,000 2,000 10,300 3,600 137,200 153,100 1,500 8,500 8,200 116,000 134,200 1,200 4,900 6,100 4,500 14,400 18,900 342,300 34,200 376,500 22,800 ~OOO 415,300 415,000 11,000 $426,000 SECTION 15 -PROJECT BENEFITS 15.01 General. The community of Talkeetna, Alaska, population of about 185, is located at the mouth of the Talkeetna River at its con- fluence with the Susitna River. The general economy of Talkeetna is based on tourism and its function as a supply center. With the completion of the paved road between Anchorage and Fai rbanks, and a new paved spur road into Talkeetna, the historic community is now more accessible and is more frequently visited. 15.02 Benefit Analysis. The benefits attributed to the proposed project are mainly for erosion protection to the community, protection to the railroad bridge, land stabilization, and area redevelopment benefits. Benefits are based on a 50-year economic project life and 5-7/8 percent interest. a. Erosion Protection. (1) The prevention of loss of land due to erosion from the Talkeetna and Susitna Rivers is taken as project benefits. More than 30 acres of land, which is owned by the Federal Government, the Matanuska-Susitna Borough, and private parties, could be lost due to erosion, if protection is not supplied. In past years, the fascine has protected the community from erosion along the Talkeetna River with the Susitna having an average annua I erosion rate of about 10 feet. 15-1 Now with the imminent loss of the fascine, erosion can continue at an unchecked rate and erode the major portion of the community. About 30 acres of land, valued at $4,000 per acre, is currently in immediate danger. Benefit accruing from abatement of loss of land by . erosion are calculated as 30 acres times $4,000 per acre times 0.06234 (CRF, 50, 5-7/8 percent) which is $7,500 per year. (2) Improvements that have been made which will be lost to this present unchecked erosion include private homes, historical build- ings, a maintenance shop, a recreational park, a resort complex, roads, and utilities. Relocation was considered for all structures that are in danger of being lost to erosion. Cost for relocating relocatable structures was a mi nimum of $2,000 per structure for six units and $4,000 minimum for eight units. Other units either had a minimum moving expense at a cost higher than the units' market value or were constructed so as not to be relocatable. As these structures are in immediate threat of loss, their market value has not been discounted in the erosion analysis. Costs derived in relocating structures were estimated at six units times $2, OOO/unit plus eight units times $4,000/ unit for $44,000. Then, this $44,000 times 0.06234 (CRF, 50, 5-7/8 percent) yielded $2,700 annua I expenses. Other structures, roads, and utilities that could not be relocated amounted to a market value of about $250,000. Annual costs were estimated as $250,000 times 15-2 0.06234 = $lS, 600. Structural losses prevented are claimed as project benefits and amount to $2,700 plus $lS, 600 = $18,300 annually. Total erosion protection benefits are $18,300 plus $7,SOO = $2S,800 annually. In addition, historical buildings that are lost can never be replaced at any cost. b. Protection to Railroad Br~dge. The proposed dike immedi- ately downstream of the rai Iroad bridge wi II channel flows downstream, alleviating eddy currents and subsequent scour of the rai Iroad embank- ment. In add ition, the di ke would save the current annual expenditures of maintaining channel alinement through the railroad bridge (exhibit S). These benefits are estimated at $5,000 annually. c. AR Benefits. Talkeetna is in an area designated by the Economic Development Administration as being eligible for aids and grants. A Federal project in the vicinity of Talkeetna, costing $426,000 would have AR benefits which are derived as the estimated contract amount times 50 percent expended for labor of which 10 percent could be local persons who would be otherwise unemployed. Therefore, annual benefits are $376,SOO times O.SO times 0.10 times (CRF, SO, S-7/8) 0.06234 which yields about $1,200 annually. d. Benefit Summary. Annual benefits from the Talkeetna project are accumulated by category and are presented in the following tabulation: lS-3 Item Amount Erosion Protection $25,800 Railroad Bridge Protection 5,000 Area Redevelopment 1,200 Tota I Annua I Benefits $32,000 15.03 Benefit-to-Cost Comparison. The annual cost is based on a 50-year economic life at 5-7/8 percent interest. Annual benefits from 15.02 are $32,000. a. Annual Cost Federa I Cost Interest and Amortization ($415,000 x .06234) $25,900 Non-Federa I Cost Maintenance 800 Interest and Amortization ($11 ,000 x .06234) 700 Tota I $27,400 b. BIC Ratio. The total annual benefits evaluated at $32,000 compared with the total annua I charge of $27,400 yields a benefit-to- cost ratio of 1.2 to 1 which indicates that the improvement is economi- cally justified. 15-4 SECTION 16 -DISCUSSION 16.01 Genera I Comments. The authorized-unconstructed project for the community of Talkeetna consisted of 1,500 feet of rock riprap bank protection along the left bank of the Talkeetna River, as described in House Document No. 34, 85th Congress, 1 st Session. The authorized project was classified as inactive since an existing emergency bank protection project had been previously constructed and was preventing erosion due to the Talkeetna River flows. The emergency bank protec- tion project, constructed in 1951 under Section 14 of the 1946 Flood Control Act, consisted of a timber and brush fascine to direct high velocity Talkeetna River flows away from the community. The timber fascine has since deteriorated and does not provide the desired pro- tection. A publ ic meeting was held on 5 January 1973 at Talkeetna to ascertain the view of local interests. Local interests have requested improvements to alleviate their flood and erosion problems. In the reanalysis of the authorized project, engineering and economic studies were made as well as an environmental assessment for a project. To provide protection from the Talkeetna and Susitna Rivers, complete flood control protection for the whole community of Talkeetna would require a structure around the community plus an interior drainage system. Various methods and scope of projects were studied in pro- viding protection for the community. It was found that total flood control 16-1 protection could not be economically justified. It was found that flood protection would need to be limited to bank erosion protection similar to that described in the authorizing project document. Bank protection can be provided which would alleviate the continu- ing bank erosion. The proposed plan consists of a 600-foot dike, 740 feet of graded and seeded bank, and 1,660 feet of bank revetment. The top of the bank protection would be the same as the existing elevations of the left embankments. To raise the height of bank protection higher than the existing bank elevation to provide a levee in effect and, hence, provide minor flood control protection would require an interior drainage system to prevent entrapped interior surface runoff from ponding behind the levee and causing additional damage. The elevation of the lowest pOint on the left embankment of the Ta Ikeetna River corresponds to about the water surface elevation of a lS-year-frequency flood on the Talkeetna. For a larger flood event, floodflows would not erode the bank but would overtop the bank revetment. No significant damage is expected on the revet- ment since it is designed for overtopping. To channel flow away from the Talkeetna community, a di ke was needed. With a dike, velocities of flow were found to be of such a magnitude that a graded and seeded section would protect portions 16-2 of the bank in I ieu of rock revetment along a 740-foot length of the Talkeetna. Accordingly, a graded and seeded section was incorporated into the project. As the reanalysis of the project continued, additional protection was added and it was found economically feasible to extend the project scope to include bank protection along the Susitna River. Workshops were held with local interest groups, and they support an erosion control project of this scope based on the economic justifications that accrue from this project. The benefit cost ratio for a project at Talkeetna is 1.2 to 1. 16-3 SECTION 17 -RECOMMENDATIONS 17.01 Recommendations. It is recommended that the authorized unconstructed project at Talkeetna, Alaska, be modified to provide for the construction of the Talkeetna Project, herein described, at a Federal cost of $415,000and subject to the conditions of local coopera- tion previously discussed. It is further recommended that this DM be approved and that preparation of plans and specifications be authori zed at a cost of $16,000. 17-1 CORPS OF ENGINEERS N 10,500 N 10,250 N 9,750 N 9,500 \1\ \ ~ U N 9,250 " \ o /8. (J) w' SEE NOSE DETAIL PLATE 3 DETERIORATED FASCI NE lm LEFT ~ o 10 N m ",I TURNAROUND TURNOUT SINGLE LANE ACCESS ROAD N 10,500 N 10,000 N 9,750 N 9,500 100' : t 400' 400' lOa' ItOO' -----SCALE IN FEET VICINITY MAP NOTES I ~~~G~N6~~ ~~O~O~N~~~~o6:N~E~O~6~6.0F TRACK AT ARR f11LE ros~ 345.68 FT. ABOVE PREPARED .~J U.S. ARMY ENGINEER DISTRICT. ALASKA CORPS OF ENGINEERS ",,,,CHOR..,,")' AI-ASiKA TALKEETNA RIVER PROJECT ALASKA TALKEETNA, ALASKA I DIKE AND BANK IMPROVEMENTS PLAN L PLATE ( \ CORPS OF ENGINEERS N 9,000 \ N 8 750 N 8,500 N 8,250 N 8,000 <J> ~\ -I r-~ ~ ':>l <. f'\ ':>l ~ LEFT BANK lJJsj 1660' REVETMENT ~I '" W o o o en w SINGLE LANE ACCESS ROAD JOINS PLATE I \ CONTOUR INTERVAL 5' 0 0 '0' 0' .0' 0 100 -... I en SCALE 'N fEET W ~O' I o 10 C\I en w \ 0 10 C\I ,,; W o o 10 en w TALKEETNA TOWN SITE N 9,000 N 8,750 N 8,500 N 8,250 \ \ N 8,000 \ ~\ GRADE, TOPSOIL AND SEED DISTURBED SURFACES WHERE W.S. OVERTOPS BANK. EXTEND STONE TO TOP OF BANK I/. 3-W.S.~------~~L..,i!< RIVER BED '.5 '1/ 85' ,: NOTES SEE NonS ON PLATE I U. S. ARMY I4'NIMUM DESIGN GRADIATIQHS ARE SHOIoiN UHDEG' [HE SECTIONS ACTUAL OUARRY OPERATION MAY REOUIRE REVISIOH THICKEN RFVET~ENT SLOPE RIPRAP TO 48 INCHES FOR FULL SIX FOOT LENGTH AT DOWNSTREAM END. TERRACE BANKS ARE SAND & GRAVEL OVERLAIN BY A SILT SURFACE. FiElD UPlORATliJN WILL BE CllNDUCTED PRI()R TO PLANS & SPECS. ACCqS ROAD TO HAVE 6" GRADED GRAVEL SlJRF~CE uVER MINIMUM 12" GRAVEL EITHER DISflNG OR FILL SEED DISTURBED TOPSOil SURFACE AT SIDES OF ROADWAY. PROVISIONS FOR DRAI~AGE TO BE SHOWN ON PLANS AND SPECIFIUTIONS LEFT BANK STA 7+40 TO STA 24 +00 REVETMENT NTS .5' QUARRY RUN ROCK BELOW) STA 0+00 TO 0+50 ARMml STONE t:42" d= II' T=)9' WI5 232 TO 549* 015 1.401 TO I.B5' W50 741 TO 109S_ 050 2.03' TO 2.32' WIO·O 14B2 TO 3704_ 0100 2.5B' TO 3.50' STA 0+ 50 TO 2+50 ARMOR STONE W'5 B4 TO 200* 0'5 W50 270 TO 400_ 0 50 W'OO 540 TO 1350'" 0 10 0 t=30': d.:9', T:15' 96' TO 1.47' TO I. B4' TO U2' 1.66' 2.50' DIKE ~ SEEDED "' "' EXISTING ~ TOE ELEV . .L.---'_~"~ 1.5' STA 2+50 TO 6+25 ARMOR STONE ,,=24" d=B' T,= 13' W'5 43 TO 102.. 0 15 .37 TO 1.05 W50 13B TO 205. 050 1.15' TO 1.32' WIOO 276 TO 691:11= 0100 ) 4B' TO 2.00' 4" TOPSQI LOVER NON ORGANIC SOILS LEFT BANK STA 0 +00 TO STA 7+40 SEEDED SLOPE NTS -+ -'--, U.S. ARMY ENGINEER DISTRICT. ALASKA CORPS OF ENGINEERS TALKEETNA RIVER PROJECT, ALASK A TALKEETNA. ALASKA OIKE AND BANK IMPROVEMENTS PLAN AND SEcn NS \ DESIGN MEMORANDUM NO. , PLATE 2 CORPS OF ENGINEERS ( ------------- BURIED TOE (SEE SECTION, PLATE Z) DIKE NOSE DETAIL NO SCALE SUSITNA RIVER 50 YEAR FLOOD Q = 243,000 cis PROFILE 100",,;;' ~~==~'O~O' __ ~2OO' HORIZONTAL SCALE IN FEE T 5' 5' 10' VERTICAL SCALE IN FEET TALKEETNA RIVER 50 YR. FLOOD PROFILE Q = 84,000 cfs 340 U S ARMY NOTES DI~E GROUND PROFILE, TO? OF LEFT BANK AND TOE OF LEFT BANK DATA WERE TAKEN FROM NOVEMBER 1972 SURVEY, AND SHOULD BE USED AS APPROXIMATE ELEVATIONS. DIKE GROUND PROFiLE AND TOE OF LEFT BANK ELEVATIONS ARE SUBJECT TO CHANGE QUE TO DEPOSITION OR SCOUR. 2 SEE PLATE 2 fOR TYPICAL SECTIONS 3. SEE PLATE) & 2 FOR ALIGNMENTS U.S, ARMY ENGINEER DISTRICT, ALASKA CORPS OF ENGINEERS TALKEETNA RIVER PROJECT, ALASKA TALKEETNA,ALA3KA DESIGN MEMORANDUM NO, I PLATE 3 Exhibit 1 Exhibit 2 Exhibit 3 Exhibit 4 Exhibit 5 EXHIBITS River Profile Fish and Wildlife Service Report· Matanuska-Susitna Borough Sponsorship Letter Matanuska-Susitna Borough Letter Department of Transportation Letter 345 34 ... ... ... 335 ... ~ :> ... 330 ..J ... 325 340 ... ... ... ... !: z 330 0 ~ C > ... ..J ... 320 l EXISTING RAILS OF FASCINE \ W.S. JUNE 20, 1973 , 336.2 3500 3600 3700 3600 3900 4000 4100 4200 4300 4400 4500 4600 4700 4600 4900 5000 5100 5200 5300 HOR I ZONTAL DISTANCE I N FEET CROSS SECT ION AT 1750 TALKEETNA RIVER zoo' ~"~O~RI~ZO~N~TA~L~S~C~<L~E~'N~FE~E~T= 100' 0' IDO' 5' 0' 5' 10' .... ERTICAL SCALE IN FEET APPROX. TOP OF LEFT BANK WATER SURFACE PROFI LE- STA.O+OO EL.343 ------BEGIN PROJEcr -------------~_ ____ -APPROX :-./\ ."",----., -GROU N D __________ " \ """"'. '" 0' ''1'\ ''------/' ~ I ~ """" ;~\1_t%_:'_B_:_N_K---'1 \ P . -.---1660' REVETMENT ; I ~ _/ ----------: ~~/ ---iT~ .. i! I --T---~-----r----~-----------~~~~----j I ---------THALWEG THALWEG SUSITNA RIVER b TALKEETNA RIVER ~ I SUSITNA RIVER FLOOD CRITICAL·----------~H-I ... ·-TALKEETNA RIVER FLor CRITICAL ~ BRIDGE 2525 I 1200 1400 1600 1600 2 0 2200 2400 2600 7000 8000 9000 HORI ZONTAL CHANNEL DISTANCE IN FEET SUSITNA RIVER 50YR. FLOOD PROFILE 0·243,000 100' O' zoo' 400' .. HORO=~ll\'.!:ON~Ti;;AL"";'SC"'A~LE~,N,...,FE".E.-'T----j VERTICAL SCALE IN FEET 10000 TALKEETNA RIVER 50 YR. FLOOD PROFILE Q. 64,000 cis 350 340 ~~ 0 T E S BANK IMPRovEMENT PROF I LES ARE NOT TO SCALE DLJE TO CKAI~NEL CURvATURE. RAILROAD-BRIDGE ABUTMENT a EMBANKMENT 330 320 TALKEETNA RIVER PROJECT, ALASKA TALKEETNA, ALASKA RIVER PROFILE EXHIBIT I 1444-75 r' .... , . -, - BUREAU OF' SPORT FISHERIES AND WILDLIFE Arc2 Office 813 P Strect Ar.chcY:1 ,-c, ,'lr-s1-;:: 99501 Cobn-:-l ri:a:-lcs A. Debelius lli.;tl'ict r:l.=:incor \L' 5];.:1 District Corps of En~incers P.\I. Eox 7002 Anchor::!;c, Alaska 99510 NOV 2 0 1974 Co: T::d~~r.ctn" :-rnsiOD (pnty('1 , f' _, r,efcrence is r,i,~cle to your letter of l:ovcr.ber 1, 1974, rC0,ucstinr our co~c1.ents conccrnin:.: fish <'.r;d -.:ildli.cc resources ;lssoci"tetl Hiti1 t;le rcfcrcncc~ ~rcject. re:,ort tmdIJr Sec. 2 401 ~s 2~cnded: 16 TLis is 0111' o~Fici(ll Fi~:' ;-:r:d "ildli~c Service of the Fish and ':i1dlife Coorc.1in'1tion Act (48 Stat. USC 661 8t 5C~.). -,'e a,:-,rce l'!ith the analysis of fiS~l r1T1d ,dldli:fe resources in the il;"cdi:,tC' :'TOjcct ?fCa as ~'rcscntcJ in the c'rn5t EnviToTl1 18ntnl I":'8.ct Statement and anticipate no adverse effects uron those resources. ' . .'0 8YC concerned, hOl'lever, as :JTcviously ex~resscd ill our COl'll'lents on the ,~ra;-t Environmental b~-~ct St;.ttcr"cnt, about :1otenti21 Cluverse effects ("f f'):='~'i1si(\n of the borrol, site <.t ;.ont<::'l1<l CreeL U:l():l aesthetic, recre- ational 2nd rishcry V8lues. -.,-.... 1C\"-... n-,. ... r,r. ·""·r... .. '~r~ .. 1, t~~,l ;: .1 ~ .:: . c~ : t 1 ,:~ " cut i 1 i : (.~ :.~ i •. ':") T f<. ': ;"','1'1,':1. 'J is' ~, ..... :::~', _'" : '('mt,,);,. C,',.:cL S-lto:', lie ., ..... ' .. t 1 ',C ~ :~\ 1~ ; ~; 10 t .i ;"~ 1. .~ ~ 1 ~'~' : ... :-:: C' ~-~ 2 C t 5 0 :f t!.:lt the!._ loc;ltio~ l:r ::1i'ninatcd ....... ~.' r T .. :"· l' ~"Cll.~ f~r-:r th-:: C:~~""::"'l't:~~Li.t:· '~'l co "'·':.'T".t C:'~ t.l~ :'rr-ject. :'lc~.sc l~:Jcr us i~r(~ c~ o~ its ~rc~rcss. I Area Director J V E.XHIBIT 2 Matallllska· Susitna BOI'ou4h, ·Inc. BOX B. PALMER, ALASKA 99645 • PHONE 745-3246 BOROUGH ASSEMBLY Colonel Amos C. Mathews Alaska District Enqineer U. S. Army Corps of Engineers P. O. Box 7002 Anchorage, Alaska 99510 Dear Colonel Mathews: December 6, 1973 Re: Flood Protection at Talkeetna As a result of the appearance of Mr. Parnell of your agency at a Borough meeting on November 20, 1973, the Borough Assembly has adopted a resolution agreeing to maintain flood and erosion control structures proposed to be constructed by the Corps of Engineers at Talkeetna. Two copies of our Resolution No. 73-119 are enclosed. At the time Mr. Parnell appeared before the Assembly, he explained that repair to the existinq fascines would give no permanent solution to the problem found at the rivers and indicated that prelim- inary work had been done on a more permanent structure but that, before the Corps could proceed further, the Corps would need a current resolution of the Assembly. After discussion on the matter, the Assembly did adopt a resolution on December 4, 1973. We assume this will give the Corps the information it needs to proceed on the above project. Yours truly, ... ' /1 k~, ~->V" / / . Borough Clerk Encs. (2) EXHIBIi 3 I-IATAtIUSKA-SUSlTIlA BOROUGII RESOLUTIOlj SERIAL 110. 73-119 A RESOLUTIOtj OF TilE ltATAIIUSKA-SUSInjA OOROIJGII AGREEING TO tlAltlTAIN FLOOD AND EROSIO!I cornRoL STRUCTURES AT TALKEETlIA. ALASKA. WHEREAS, the United States Corps of Engineers has determined that It is feasible to construct flood and erosion control structures at Talkeetna, Alaska; and ImEREAS, the United States Corps of Engi neel"S requi res a corrmi tment of local cooperation as a prerequisite to undertaking projects of this nature; and 11HEREAS, the [lroject is necessary for the preservation of parks and rccreatlon facilitics at Tal~eetna, Alaska; NOli THEREFORE, IlE IT RESOLVED by the Assembly of the Matanuska-Susftna Uorou9i1 th.lt, ill coanpction \'Ii til t1lis proje:t, the Borough shall: 1. Prcvid~, l:iti,Gut cost to the U~itcd States, all necessary lands, C<lSO"""ts, and rights of way requircd for construction and subsequent maintenance of the nroject, including suitable borrol1, Quarry or snoil disposal areas with any neces sary retai ni rig di kes, bulkheads, and embankments therefor. 2. Accomollsh, without cost to the United States, alterations and relocations as required of any and all utility facilities. 3. Hold and save the United States free from damages that may resul t from con- struction and maintenance of the project. 4. Maintain and operate the project after completion ~,;thout cost to the United States In accordance with regulations prescribed by the Secretary of the Anny. 5. Assume full res[lonslhllity for all project costs In excess of statutory Federal cost limitations. 6. Contribute, in cash, the local share of rroject construction cost, deter- mined In accordance with existing policies for regularly authorized projects, for projcct costs assigned to project features other than flood control or where'special local benefits will accrue. 7. Prevent further encroachments 11hich might Interfere with proper functioning of the project for flood control. PASSED AlID APPROVED by the Assembly of the r1atanuska-Susitna Borough this ;j i~~ day of ~'~ ~-<'---"-'L d.v./ • 1973. ~) 2;t.~~.---,---~. Larson ---~-- (Jorough Mayor ATTEST: C· . ;:;-{(.(~71/4;-~ Evelyn T pson 7 Borough lerk (SEAL) Matanllska· Stlsltna BOI'ou4h, Inc. BOX B, PALMER, ALAS KA 99645 • PHON E 745-3246 DEPARTMENT OF ADMINISTRATION Colonel Charles A. Debelius District Engineer United States Army Corps of Engineers P. O. Box 7002 Anchorage, Alaska 99510 December 4, 1974 Subject: Talkeetna Water Erosion And Flood Control Service Area Dear Colonel Debelius: Enclosed is a certified copy of Ordinance No. 74-50 which was enacted by the Bo'rough Assembly December 3, 1974. This service area provides the legal mechanism whereby the owners of benefiting property may tax themselves so that the Borough can meet its local government obligations for participating in the Talkeetna Water Erosion Control project. WMH/jis Enclosure • '. ~2Z1Y~~ Wes ;:.0{ Howe Borough Manager EXHI8IY ,~ MATAflUS/:A-SUSITrlA BOROUGH 1 ORDlfu\I:CE SEr.lfll NO. 74-50 !).ULJJ: '_1 U~.'-·~lh •. ,lot .. 1\1"\.'01 Spon~ol cd ~ ~Ior • t': {\~~!~''''r~ n~ T"F ~~~~"nl y nr TIl< 1'~n'!I1~",\-~II~:T>'~ r-nnnllr;u rQM11l"HlNr. S[;;\'l~r ,.,--;, '::'./~ :,.,' ~:~r1~:.' ~~~·~:-::CT. rl"'~ 1':::: r:'rT'0~l ,""'-r~(~Vl~l:;.; l"t£~ [ROSIO:, M;D FLOOD cer'TROL, At/O PROVIOlliG ~OR lHE !\m\lNI~lRATl\JN 01 WAIER lRoslON !'11O FLCOD COiITfWL. area: WHEREAS" the owners of property within the following described Point of beginning being the east-west center section line where the A1as~a Railroad intersects the east bank of the Susitna River in Sec. 36, T2G1l. R5!1. S.r1.; thence fol101'lin9 the I,est side of the Alaska Railroad right-of-Hay in a northerly direction to a point I,there the Alaska Railroad intersects the south bank of the Talkeetna River; thence in a generally southerly d'rection to the point of confluence of the Talkeetna and Susitna Rivers; thence generally south along the east bank of the Susitna River to the point of beginning: all situated I'lithin T2611. R51'I, 5.1'1. petitioned the Borough Assembly to establish a service area to provide water erosion and flood control; and .IHEREflS. the Borough Assemo1y held public hearings on the establishment of a service area as requested; and WHEREAS, ~ proposition was placed on the ballot at the 1974 Dorough g:'1cra1 election to be voted on ~y the residents of the proposed servlc!! area; and ~rnEREflS, the proposition to establish the service area was passed by a vote of 27 in favor and 3 opposed; tlOl'1 TlJEIl.HORE. BE IT OROI\INEO: Section 1. Classification, This ordinance is of a permanent nature and shall become a part of the Ilorough Code. Section 2. Scnri1bi1ity. If any provision of this ordinance or application thel'eof to any person or circu,"stance is held Invalid. the remainder of this ordin~nce shall not 'be affected thereby. Seclion 3. Servic!,~'cil [sj:E.!>lished·. There is hereby establish- ed '-Iatanusl:a-Susitna [)orough Service flrea t1o.y. Ta1keelna ~Iater erOSion and flood cantrol. to provide water erosion and flood control within its boundarle~. Section 4 • .Jl~~. ThCl boundaries of the Mat~nuska-SusitnJ Ilo r(lu!)h Servicc f"'ciJ ':0. 5. T,lli:eetna Wolter el'o.ioll and flood control, ~re hl'r\:hy est;",1i~,h("d JS ~bovc dt'~crlbcd. , II .Il L' .:i "'I , ! , "i !~ " . , Section 5. I\dministration. Matanuska-Su,sitM Borough Service Area 110.1, TaHcetna water erosion and flood control, shall be administered 1n accordJnCe with Section 2.60.050 of the Borough Code. , Secilon 6. Effective DJte. This ordinance shall become effect I -I ive upon its adoplion by the Borough Assembly and signature of the Mayor. I Introductlon: ____________ l I First Reading: ___________ _ Public Hearing: __________ _ , , i ! ADOPTED by the Assembly of the Matanuska-Susitna ~orough, Alaska, this ____ day of _______ " ____ t 1974. AnEST: Evelyn Ihompson Corough Cl~,.1; (SEAL) ROnald L. Larson Borough ~'ayor , , I 1 I .! \. , 'J n [[' ,Id: T ,', r l'T [J r 1~: ;',:: S :' fP: l!. T I 0 I: FELJLl!flL IIIIIL",-,!d.l ;,I,r.~II'!I', Illi\'II(H~ "rHL "I.I\~;I\I\ Hf,11..1l0AIJ I'. o. I,ax ·,·;'111 ANCH~II"Gl:, AL"~,I;" urnOl Colonel A. C. ~bLhch's District EI1(',.inccr Al;1skil District, Corps of Engi.neers 1>.0. Bo": 7002 Anc!101-<lge, Al<lska 99501 I have your letter of ,\Ul'.u::t 1.7. August 2 li, J.970 NPAEN-Plt-R !listo)" ical.l Y I the TalkceLn:1 H.iver h:1S bl.!ell ;1 continued sou,~e of tl"oulle to Lilc [:l";IC\.~ ~\I1J hl."id~',e ;H ·j';l1kcLll<l.· i'cnn:10cmt contro;' of ;;:IC ch:1.n:l(.:J~> IIp!~trc,'!lI is not p(ls~~:i.bl.t! ',.'ith the ('::tcnsi\<~ br.:lid- inr, anu [l:1.t gl"d<1ient of this stl·C.:l,iI as it :tpproaches its con- fluence \·]ith the Su:;itna River. Frequent ch:1l1ncl ':ode lIp~trc;I:!1 [r0:11 our hridge somel'llIat allevia,t.:::s t.he prohleIT!, but marc i::lporto.nt, controlled alignment of the river belCH" us, tendin~ to provic(! clire:ct flo' .. ' perpendicular to our center line, is desired. This has been provided by the 10(; f.::sd.ne previously il~st.111ed, and rcpl~cemcnt.by some flood,control structure accomplishinG this is he~1rtily recom:nen(led. Very ,truly yours, ,1 'r-') ./ .... <',..., '1 (. C-'-..../ I/),. &. -' " . -vt __ -"--r.:-i......:..J :-.r/ -. -_..... -/1' (~ .''V ' ohn E. l'lanley H;}n<lger EXHIBIT G