1 - Alaska Energy Data Inventory

DEPARTMENT OF THE ARMYALASKA DISTRICT. CORPS OF ENGINEERSP.O. BOX 7002REPLYTOATTENTION OF:~\ ,? ,~:11',' ~'~NPAEN-PR-R 28 February 1975SUBJECT:Ta 1 keetna Ri ver Proj ect, Al aska.Division Engineer, North Pacific\ ':1. Transmitted for your ~eview and approval, in accordance with ER1110-2-1150, 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 lieuof a project restudy report.3. The EIS has been fully coordinated with the State and other Federalagencies. Their comments have been incorporated into this final EIS.4. Recommend immediate capability of $415,000 be expressed for inclusionin the Division's capability and that $16,000 be authorized andapproval granted for preparation of plans and specifications.5. It is further recommended that action be implemented to reclassifythe status of the project from "Deferred for Restudy" to "Active." Thisis a project that could be started this ~lendar year to provide "Brickand !·lortar" type jobs as i ndi cated at th H~ Appropri ations Subcommitteeon Public Works hearing on 25 February 19 ~., ~ ~~Sinc~.r~4). ~rs~\/-(0 1 "1.A---~ !>______ ( __.d... ..,-,. ) £ I-t/{ ____ _4 Incl / CHARLES A. DEB '. US --.as {und sep covColonel, Corps 0" ,Eng'neers'ct Engineer.If f{\~ ~---- ". ".--~-.----------\

TALKEETNA RIVER PROJECT, ALASKAGENERAL DESIGN MEMORANDUMPERTINENT DATAAuthorizationThe Talkeetna River Project was authorized by the FloodControl Act of 1958, Public Law 85-500, in accordance withthe recommendations of the Chief of Engineers.GeneralLocationTalkeetna, AlaskaDrainage Area at Project SiteTalkeetna RiverSusitna RiverPurpose of Project .Economic Life of Project2,015 Square Miles11,035 Square MilesBank Erosion Protection50 yearsBenefit - Cost Ratio . . 1 .2 to 1DikeLengthNose .600 feet25 feetMaximum Elevation 343.5Minimum Elevation 341.5Average Height . . . . . . . . . . . . . .. 5 feetTop Width .Side Slopes8 feet2H, 1VPERTINENT DATASheet 1 of 2

PERTINENT DATACore Material . .Protection Cover ThicknessGravelQuarry RockRevetmentLengthSide SlopeAverage Height .Fi" Material . .Protective Cover Thickness .1,660 feet2H, lV7 feetGravel1.5 feet Quarry RockSeeded 5 lopeLengthSide Slope740 feet3H, lVAverage Height . . . . . . . . . . . . . . . 7 feetPERTINENT DATASheet 2 of 2

---------~---------------------------TALKEETNA RIVER PROJECT, ALASKADESIGN MEMORANDUM NO. 1GENERAL DESIGN MEMORANDUMTABLE OF CONTENTSPERTINENT DATAParaPageSECTION 1 - PROJECT AUTHORIZATION1. 011. 021. 031. 04AuthorityProject as Described in Project DocumentLocal Cooperation Specified in Project DocumentProject History1-11-11-11-12.012.02Preauthori zationPostauthori zationSECTION 2 - INVESTIGATIONS2-12-13.013.024.01SECTION 3 - PUBLIC MEETINGSPreauthorizationPostauthor i zationSECTION 4 - LOCAL COOPERATIONLocal Requirements3-13-14-15.015.02SECTION 5 - LOCATION OF PROJECT AND THE RIVERSProj ect LocationThe Rivers5-15-1

TABLE OF CONTENTS (Cont)ParaPage5.03 Flood Plain Area 5-25.04 Erosion 5-2SECTION 6 - PROJECT FORMULATION6.01 Planning Concepts 6-16.02 Project Scope 6-16.03 Alternatives 6-26.04 Proposed Plan 6-9SECTION 7 - BASIS FOR DESIGN7.01 General 7-17.02 Hydrology 7-2SECTION 8 - RECOMMENDED PROJECT PLAN8.01 General 8-18.02 Design References and Criteria 8-18.03 Rock Dike 8-28.04 Graded and Seeded Bank 8-48.05 Bank Revetment 8-48.06 Construction Materials 8-4SECTION 9 - DEPARTURES FROM PROJECT DOCUMENT9.01 Departures 9-19.02 Reason for Departures 9-1i i

TABLE OF CONTENTS (Cont)ParaSECTION 10- ENVIRONMENTAL CONSI DERATIONS10.01 General10.02 Existing Conditions10.03 Environmental Impacts10-110-110-3SECTION 11 - REAL ESTATE11 .01 General Land Description11.02 Land Acquisition11-111-1SECTION 12 - PROJECT OPERATION AND MAINTENANCE12.01 General12.02 Annual Cost12-112-1SECTION 13 - DESIGN AND CONSTRUCTION SCHEDULE13.01 Genera I13.02 Proposed Schedule13-113-1SECTION 14 - COST ESTIMATES14.01 Proposed Plan14-1SECTION 15 - PROJECT BENEFITS15.01 General15.02 Benefit Analysis15.03 Benefit-to-Cost Comparison15-115-115-4iii

TABLE OF CONTENTS (Cant)ParaPageSECTION 16 - DI SCUSSION16.01 Genera I Comments 16-1SECTION 17 - RECOM ENDATIONS17.01 Recommendations 17-1No. Follows P~Aerial view of the confluence of t e Talkeetna and SusitnaRivers at Talkeetna, Alaska 5-22 View of fascine from upstream en as it appeared in May 1951 6-33 Fascine as it appeared in October 1971 6-3Alternative Structural Improvem nts 6-4Location Map 5-12 Stream gages and Quarry Site 7-23 Project Map 8-1PLATESPlan2 Plan and Sections3 Profi I es and Deta i Iiv

TABLE OF CONTENTS (cont)EXHIBI SRiver Profi Ie2 Fish and Wildlife Service Report3 Matanuska-Susitna Borough Spo sorship Letter4 Matanuska-Susitna Borough Lett r5 Department of Transportation Le ter

SECTION 1 - PROJECTUTHORIZATION1.01 Author ity. The Flood Control ct of 1958 (Publ ic Law 85-500)authorized improvements for bank pr tection at Talkeetna, Alaska, asdescribed in Interim Report No.2 - C ok Inlet and Tributaries, andprinted in House Document No. 34, 8 th Congress, 1st Session.1.02 Project as Described in Proje t Document. The plan of improvementset forth in the project documen calls for the construction of rockriprap bank protection along the left ank of the Talkeetna River, extending1,500 feet downstream from the r i Iroad embankment.1.03 Local Cooperation Specified iDocument. The projectdocument specifies that local interesta. 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 damagesdue to the construction work,c. Agree to maintain the works after completion in accordancewith Federal regulations.1.04 Project History. The Rivers nd Harbor Act of 1948 authorizeda study of the Cook Inlet and Tribut ries within Alaska. This study wasrelated to water resource improvem nts within the study area for whichthe Talkeetna River and community f Talkeetna were included. Thereport resulting from this Rivers and Harbor Act included a recommendation1-

SECTION 2 - INVESTIGATIONS2.01 Preauthorization. Investigatio s made in preparation of theproject 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 preparationof this report include topographic surveys, studies for a source of quarryrock, and coordination with local interests. Office studies include hydraulicanalyses, quantity estimates, cost e timates, and a review of benefits. Areconnanissance trip and minor mat rial laboratory tests were accomplishedfor the proposed quarry site. In ad ition, cross-sections in selectedlocations were taken along the Talk etna River. These studies were alsosupplemented with the II Flood Plai n nformation, II Talkeetna, Alaska, reportdated June 1972 by the Alaska Distr ct, Corps of Engineers. Includedwere sections taken across both the ITal keetna and Susitna Rivers, derivedIntermediate Regional Flood and Sta~dard Project Flood flows, andbackg round data.II2-

SECTION 3 - PUBLIC MEETINGS3.01 Preauthorization. No formal public meetings were held priorto authori zation of the initial3.02 Postauthorization. he Id at Ta I keetna on5 January 1973 to ascertain local i terest desires and to discuss variouscorrective actions. Local interests desi red add itional protection fromfloods and bank erosion along thediscussed during the meeting inclalkeetna and Susitna Rivers. Methodsdikes, bank revetment,and various alternative constructi n materials. Twenty-six people attendedthe publ ic meeting. The proposed project was coordinated with Federal,State, and local agencies. Inform I contacts, including workshops, withlocal officials and other interested local residents indicate that the communityand the local sponsor are extremely concerned about erosion protection atTalkeetna.I3t-1

SECTION 4 -OCAL COOPERATION4.01 Local R_~guirements. Prior o construction, the project sponsorwill be required to enter into a written agreement agreeing to the itemsof 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 servicearea that wi II be the legally consti uted vehicle with full authority andcapabi lity to perform the terms of ocal cooperation. This would thengive the borough the ability to co ply with Section 221, PL 91-611.4--1

ISECTION 5 - LOCATION IOF PROJECT AND THE RIVERS5.01 Project Location. The commlunity of Talkeetna, Alaska, is situatedon the left bank of the Talkee+a River at its confluence with theSusitna River (see figure 1). The Icommunity is located about 115 mi lesnorth of Anchorage, at mi lepost 22~ on the Alaska Rai Iroad and has apopulation of about 185 people (19JO census). This unincorporated communityserves as an important disrbution center to homesteaders, prospectors,trappers, and hunting-fi,hing-outdoor recreation enthusiasts.Supplies are distributed from Talkleetna by boats, airplanes, train, andtrucks. Principal business estab'lshments include flying services, motels,hotels, lodges, and trading posts. Other business enterprises includebars, 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, aost office that serves over 1,000 people,road maintenance shops and facili ies, and two new schools. A pavedhighway now connects Anchorage with Fairbanks and a new paved spurconnects Ta Ikeetna with the paved IhighWay which allows easier accessto the Talkeetna Area.I5.02 The Rivers. The Talkeetn4 River is about 80 miles in length witha drainage area of about 2,015 sqlare miles. The Susitna River has alength of about 200 mi les and a dr inage area of about 11,035 square miiesupstream of Ta Ikeetna. Both of t1ese 9 lacier-fed rivers are meanderi n9,III15-1

'. - ··':a"..:'~ .' ;,'.. I"; ~; ,. . ~-.-". ..o 1/2 I~3.-:=F.::;::jMILES.----~~--_J.~"GENER,!I,L DESIGN MEMON'ANDUMTALKEETNA RIVER PROJECTALASKA'LOCATIONMAPALASKA DiSTRICT,CORPS GF ENGINE~P.SANCHORAGE,ALASKAFEBRUARY 1975

aided and subject to high runoff.5.03 Flood Plain Area. Talkeetna is susceptible to inundation fromboth the Talkeetna and the Susitna River with out-of-bank flows occurringat flood stages of lS-year and 2S-year frequency recurrence intervals,respectively. While the Alaska Rai Iroad embankment and bridge structureprovides partial low flow protection through volume detention, runoffexceeding a 70-year frequency-flood would overtop the ra i I road fi II, floodingTalkeetna from the back side. The flood plain is occupied by a railroad,roads, streets, utilities, homes, businesses, historical structures, andgovernment facilities which would be damaged by a major flood.5.04 Erosion. Flood flows causing bank erosion occur annually onboth the Talkeetna and Susitna Rivers. While the timber fascine hasprovided partial protection along the Talkeetna River, the lower portionof town has been under excessive attack from both river flows. Evenwith emergency construction efforts by the local residents, land losshas still exceeded 800 feet width since 1917 with an average loss of 10feet per year along the left bank in recent years. This annual loss hasresulted in much damage to land and personal property, and has causednumerous bui Iding relocations. With the gradual deterioration and recentfailure of portions of the fascine, the community is now in immediatedanger of a greatly accelerated erosion rate. This erosion wi" alsoaugment the flow attack problems along the Susitna reach.5-2

Photo 1. Aerial view of the confluence of the Talkeetna and Susitna Rivers atTalkeetna, Alaska (Corps of Engineers Photo, July 1974.)

and was not considered in further detai I. Protection in the form ofbank erosion was considered, and it was found that some methods could beeconomically justified depending on the scope of the project and constructionmaterials utilized. Various methods and degrees of bankprotection were studied including dikes or levees, groins, bankrevetment, and soi I stabi I i zation. I n addition, various materials forconstruction were considered including timber, river sand and gravels,quarry stone, and river rocks. Timber structures were estimated on a20-year physical life; gabions on a 40-year physical life; with sand,gravel, river rocks and quarry stones having at least a 50-year physicallife. Annual maintenance was an additional factor. Four alternativedesigns are included for structural land protection.a. Rehabi I itate the Existing Fasci ne. The townsite of Tal keetnais suffering from bank erosion behind the fascine because the fascinewas not maintained and thus deteriorated. This alternative wouldreplace the deteriorated timber logs between the steel pilings andextend the fascine with like materials about 1,500 feet downstream. Therehabilitated fascine would again provide protection from bank erosionby the Talkeetna River as well as additional protection from the watersof the Susitna River. Environmentally, this alternative is acceptableand would provide the same protection as the proposed project. While6-3

Photo 2. View of fascine from upstream e nd as it appeared in May 1951.( Corps of Engineers Photo. )Photo 3.Fascine as it appeared in October 19 71. (Corps of EngineersPhoto)1204-75

little or no vegetation would be removed, significantly more riverhabitat would be covered by this alternative than by the proposedproject. Greater quantities of construction material than in the proposedproject would also be required. The higher annual cost of this alternativeproduced 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 projectingriverward from the left bank of the Talkeetna River past the endof the dike. The dike and groins would be constructed by using sandand gravel from the riverbed with quarry stone for an outer protectiveshell. The dike and groins would function to redirect flows away fromthe eroding bank. Deposition of material would occur in front of thegroins.Environmentally, this alternative is acceptable. This alternativewould alter the river morphology of the Talkeetna River; however,because of the normal fluctuating channel and flow conditions of theTalkeetna River, no adverse environmental impact would be anticipated.Greater quantities of construction material than required forthe proposed project would be necessary to complete the constructionof this alternative. The higher annual cost of this alternative produced6-4

TABLE 1. ALTERNATIVE STRUCTURAL IMPROVEMENTS - TALKEETNA, ALASKAAL TERNATIVESRECOMMENDED PROJECTDESIGN NO 2400 L.F. * 600 Ft. DIKE & 2400 L.F.* 2400 L.F.* DIKE, GRADED & SEEDEDCONSIDERATION IMPROVEMENT LOG FASCINE GROINS GAB IONS ROCK DIKE BAl.'Th REVETMENTProject Area 80 acres 80 acres 80 acres 80 acres 80 acresEconomicallyFeasible Not Rated YES YES YES YES YESEnvironmentallyAcceptable YES YES YES YES YES YESDesign Life N/A 20 yrs 50 yrs 40 yrs 50 yrs 50 yrsConstructionCosts NONE 337,000 628,000 658,000 676,000 426,000AmortizedCosts ** N/A 29,100 39,200 43,000 42,100 26,600AnnualMaintenanceCost N/A 2,000 800 1,000 800 800Annual Cost N/A 31,100 40,000 44,000 42,900 27,400Benefits *** N/A 32,000 32,000 12,000 32,000 12,000BIC Ratio N/A 1.03 .80 .72 .74 1.2'k Linear Feet5-7/8 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 gabionsconstructed 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 itwould be costly to separate cobbles and stones from the riverbed. Thegabions would stabilize the left banks of the two rivers and would preventflows from eroding the bank.Environmentally, this alternative is acceptable. This alternativewould alter the ri ver morphology of the Talkeetna and Susitna Rivers;however, because of the normal fluctuating channel and flow conditionsof the Talkeetna and Susitna Rivers, no adverse environmental impactwould 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 constructedalong an alinement about 100 feet riverward from the existingleft bank of the Talkeetna and Susitna Rivers. The dike would beconstructed of sand and gravel excavated from sandbars in the riversand would be protected by quarry stone from a designated quarry si te.This alternative would prevent bank erosion due to the Talkeetna and6-5

Susitna Rivers and, depending on dike design, would provide floodprotection from floodwaters in both rivers.This alternative would probably have the greatest impact on theenvi ronment as compared to the rest of the alternati ves due to the si zeof the project in relation to esthetics, river morphology, and quantityof material requi red for construction. However, thisal ternative wouldprovide both flood and bank erosion protection to the community ofTal keetna which would have a beneficial impact on the commun ity.The higher annual cost of this alternative produced a lower benefitto-cost ratio than did the proposed plan (table 1). Therefore, thisalternative was not chosen.2. Nonstructural. Nonstructural methods are considered to beother procedures for reducing bank erosion and damage potential s.These include no protective construction, relocation of the town ofTalkeetna, and zoning and building ordinances.a. No Construction. Providing no protective construction wouldresult in continuing and possibly escalating bank erosion of the townsiteof Talkeetna, continuing loss of vegetation and animal habitat dueto bank erosion, and eventual loss or damage to buildings and structures(i.e., homes, motel, barn, several historical buildings, campingarea, utilities, road). By not disrupting the influences of the Talkeetna6-6

and Susitna Rivers on the community, these rivers would continuetheir encroachment and flooding actions on the townsite. These actionswould continue to affect the water qual ity of these two rivers and eventuallywould alter their river morphology.Environmentally, this alternative is acceptable and would eliminatethe adverse impacts associated with the proposed plan. The Talkeetnaand Susitna Rivers would be allowed to continue in their naturallyfluctuating channels within their flood plain. However, abandonmentof the project would not necessari Iy assure the return of the area tonatural conditions. Local people may institute some improvementmeasures on their own. I nauguration of flood-plain zoning with floodproofingof existing buildings, appropriate building codes, relocations,and other appropriate land use practices could decrease the disruptinginfluences of flood and bank erosion.b. Relocation. This alternative would be the relocation of structuresand utilities at Talkeetna that could be damaged by bank erosion andflood ing from the Ta Ikeetna and Susitna Rivers to another location thatwould have a lower probabi I ity of damage than the present location.This alternative would have a desirable impact on the Talkeetnaand Susitna Rivers and the adjacent area as relocation would allow therivers to continue along their natural course. Also it would remove the6-7

community from an area in which the town is naturally and habituallysubjected to bank erosion and flooding from the two rivers.The relocation process would extend over many years and wouldbe governed by existing regulations. While this would probably beeconomically feasible, it is socially unacceptable because the people ofTalkeetna do not want to move. Furthermore, it would result in problemsof compensation for land that would be zoned as nonusable and forrelocation of buildings that have not yet served their complete economiclife. In addition to these problems that would have to be solved, a morebasic problem is the fact that neither the community nor the Matanuska­Susitna Borough have the authority necessary to implement this action.Since this solution remains as being basically only academic and at presentnot 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 intothe larger category of flood plain management. The community ofTalkeetna is not incorporated and hence does not have the power to zone.The Matanuska-Susitna Borough does not have area wide regulatorypower for flood control. However, the local citizens could apply flood plainmanagement principles to the land endangered by bank erosion. Thisalternative would have a beneficial impact on the Talkeetna and Susitna6-8

Rivers because no new construction would occur in or wou Id alter the river.This alternative would have an undesirable impact on the communityof Talkeetna by allowing continuing bank erosion and the subsequentloss of lands, vegetation, and anima I habitat, which the proposedplan has been designed to prevent.6.04 Proposed Plan. The proposed plan is an erosion control structureconsisting of 600 linear feet of dike extending downstream from the railroadbridge forcing the Talkeetna River flows away from the bank, 740I inear feet of grading and seeding immediately downstream from the rai 1-road embankment, 1,660 linear feet of rock revetment along the Talkeetnaand Susitna Rivers. This plan is discussed in the following sections.6-9

SECTION 7 - BASIS FOR DESIGN7.01 General.a. Talkeetna is situated on the left bank of two rivers, at theconfluence of the Talkeetna River with the Susitna River. An AlaskaRailroad bridge spans the Talkeetna River about 1,500 feet upstream of theSusitna River. In 1949, the Alaska Rai Iroad agency initiated a channelimprovement project upstream of the bridge, blocki ng meanders andexcavating new channels to direct the flow perpendicular to the bridge.In 1951, the Corps of Engi neers constructed 1,000 feet of timber fasci nebelow the bridge to continue the straight channel al inement and thereby,directed flow away from the left bank of the Talkeetna River andthe Talkeetna townsite. Presently, the channel above the railroadbridge is much the same as before the channel improvement project withan increasing quantity of flow approaching the bridge at an angle,directing flow towards the fascine. The fascine has been breached insevera I areas and has deteriorated to the extent that it is no longereffective. Below the confluence of the Talkeetna River with the SusitnaRiver, a serious bank erosion problem exists at the west end of thetownsite.b. Soi Is and Geology. The Talkeetna area geology consists of analluvial plain of sandy gravels. Along the river bottoms, stream flows7-,1

have concentrated gravel and shingle rocks in small quantities up to about4 inches in diameter. No bedrock outcrops existing in the immediate vicinity.Drainage Areas. The Talkeetna River and the Chul itna River arethe major tributaries of the Susitna River. The Talkeetna River, whichencompasses total drainage area of 2,015 square miles, has its originat the Talkeetna Glacier in the Talkeetna i\10untains. The areas aboveTalkeetna drained by the three rivers range from 350 feet to over 6,000feet in elevation. All have portions of thei r higher elevations coveredby glaciers.LocationsRiver Length(M iles)Drainage Area(SM)Talkeetna River at MouthSusitna River at Talkeetna802002,01511,035d. Climate. The area is characterized by moderately warm summersand cold winters with temperature extremes ranging from +91 0 F to -48 0 F.Annual precipitation averages 28.8 inches and annual snowfall 114 inches.Rainfall is generally the heaviest in July, August, and September withmonthly precipitation amounts about equal for the rest of the year.7.02 Hydrology.a. Data Sources. The U. S. Geological Survey has maintainedstream gages (see figure 2) at the following locations upstream fromTalkeetna for the periods indicated below:7-2

~---- ----~-NUSt

LocationsSusitna River at Gold CreekChulitna River near TalkeetnaTalkeetna River above TalkeetnaPeriod of RecordAugust 1949 - PresentFebruary 1958 - PresentJune 1964 - PresentTo supplement the records of the gaging stations and those of snowIsurveys with more information concerning past floods, newspaper filesand hi storical documents were reviewed.b. Past Floods. Major floods have occurred in the study areaduring spring, summer, and fall seasons.River stages can rise fromnormal flow to extreme flood flow in a relatively short time. The largestknown flood occurred in September 1942, resulting from 48 hours ofheavy rains in the mountains, and associated glacial melt. The TalkeetnaRiver rose more than 6 feet, flooding homes and businesses in Talkeetnawith 2 feet of water. In August 1971, a flood occurred (estimated to beabout the 20-year frequency event) resulting in considerable bankerosion and flooding at the west end of the townsite.c. Design Floods. Intermediate reg iona I and standard project flood sfor the Talkeetna River near Talkeetna and the Susitna River at Talkeetnawere developed for use in the Talkeetna Flood Plain Information Reportpublished in June 1972.Design flows with a 50-year recurrenceinterval were developed from statistical analysis of streamflow records.These flows a re tabu lated be low:7-- 3

Flood FrequencyTalkeetna River 3usitna Riverat mouth at TalkeetnaStandard ProjectIntermediate Regional50-Year121,000 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 theTalkeetna River (84,000 c.f.s.) with a Susitna River flow of 243,000c.f.s. below the confluence of the Talkeetna and Susitn

SECTION 8 - RECOMMENDED PROJECT PLAN8.01 General. T.he recommended plan as shown in figure 3 is a combinationof control methods. This was determined to be the most economicalapproach to the erosion problems attributable to the Talkeetnaand Susi tna River. The plan consists of a 600-foot-long dike extendingdownstream of the railroad bridge for directional control of the TalkeetnaRiver. Since the dike will be overtopped, 740 feet of the bank along theTalkeetna townsite will be graded and seeded for low velocity erosionprotection. Downstream of the seeded area, the bank is subject to erosionfrom both the Talkeetna and Susitna Rivers. Joining the seeded bankand continuing 1,660 feet downstream, riprap bank revetment is recommended.8.02 Design References and Criteria.a. HEC-2 Water Surface Profiles Computer Program 723-02A wasused to determine water surface elevations and velocities. ManningsIInll values used in the program are .030 for the channels and. 15 forthe overbank areas.b. Revetment stone gradation and course thickness weredetermine

INsus/rNARIVER.~< .. :=1nf1nJu===!I ~I ====~IMAINiU U:lL.:=::::::::IL K E NNOTE:PROPOSED DISPOSALLOCATION IS THE AREA8ETWE EN THE PROPOSE DOIKE AND THE LEFTBANKOF THE TALKEETNA~======~i ~j======~i ir---~FEET200 0 200 400 600J H H E---- I ::::oJGENERAL DESIGN MEMORANDUMTALKEETNA RIVER PROJECT.ALASK APROJECT MAPALASKA DISTRICTCORPS OF ENGI NEERSANCHORAGE, ALASKAFEBRUARY 1975

This formula was concurred in by the Corps of Eng ineers for Alyeskapipeline river crossi ngs.2/3/ 1/3ds = (q Fbo ) x scour factorin whichds means depth from some standard flood elevation to the averageestimated bed in a cross section.q = total Q/channel width IIW Il = c. f.s. per foot of widthDM means the median size by weight, in millimeters, of a bedsample 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.) withthe 50-year Susitna River flow (243,000 c.f.s.) was used as the designcriteria for the Talkeetna dike and bank improvements and the Susitnabank revetments. Thi s is consistent with the expected life of rockrevetment type of construction. The river profiles are shown onexhibit 1.8.03 Rock Dike. The GOO-foot long dike averages about 5 feet highand has a top width of 8 feet. A gravel core with armor facing at lVon 2H side slopes is planned. Material excavated for the buried toewi II be used as core embankment. Excess material wi II be used asfill for bank improvements or will be wasted in the channel adjacentto the graded and seeded bank. The top elevation of the dike wi II8-2

slope from elevation 343.5 at the railroad bridge to elevation 341.5at the lower end. Overtopping wi II occur at design flow in theTalkeetna River. Since the lower slope of the dike is greater than theslope of the water surface profi Ie; overtopping, as the water surfacerises, will gradually proceed upstream. This will tend to reduce thehead differential across the dike and will decrease overtopping velocity.Maximum overtopping velocity was computed to be 6.5 f.p.s.Profi les of the design floodwater surface with respect to the dike areshown in plate 3. The channel side of the dike for the first 50 feetbelow the railroad bridge is designed to withstand a computed velocityof 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 toprotect against a velocity of 12 f. p. s. From station 2+50 to the endof the dike, 24 inches of riprap are provided for protection againstvelocities of 10 f.p.s. Sections and riprap gradations are shown inplate 2. Scour depths corresponding to velocities along the dike werecomputed and sufficient rock wi II be placed at the excavated toe toprovide design armor thickness to the computed scour depths on a1V on 2H slope. An 18-inch layer of quarry run rock will be carriedover the top and back slope of the di ke and an apron provided at thetoe of the back slope to prevent scour. Plate 2 shows dike sectionsand riprap gradations.8-3

8.04 Graded and Seeded Bank. When the dike is overtopped, velocitiesalong the upper bank at the Talkeetna townsite will be slightly lessthan 5 f.p.s. Seven hundred and forty feet of the bank will be gradedto a lV on 3H slope and will be seeded to withstand these velocities. Aseed-fertilizer-mulch mixture will be distributed on 4 inches of topsoil(plate 2) .8.05 Bank Revetment. Extending 1,660 feet downstream from thegraded and seeded bank, riprap revetment continues around the leftbank of the Susitna River. Average height of the bank revetment is7 feet. The computed water velocity of 7 f. p. s. was used for riprapdesign. An 1 a-inch revetment thickness is adequate to withstand thisvelocity plus ice and debris impact. The toe will be buried a minimumof 7 feet and wi II be weighted with sufficient material to provide thedesign, revetment thickness to computed scour depth. Material excavatedfor the toe burial will be used to dress the upper slope. Quarryrun revetment stone reasonably graded and up to 18 inches in diameteris recommended for slope protection below the design water surfaceelevation (see plate 3) or top of submerged banks. Banks extendingabove the water surface will be graded, top soiled and seeded tovegetate bare or disturbed surfaces.8.06 Construction Materials. Sand, gravel, topsoi I, silt, and quarryrock are available in the area.8-4

a. Materials at Site. Sand and gravel s from excavation for toeriprap wi II meet major requirements. Minor add itional sand and gravelfor 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 HighwayDepartment Quarry located along the middle fork of Montana Creek(see figure 2). The only other rock nearby is at Curry, on the AlaskaRailroad route, about 25 miles north of Talkeetna. This location wasinvestigated for a rock source for other projects .. It was learned thatadditional quarry work at Curry would require relocating the railroad,the cost of which is prohibitive.(1) Haul Road. The haul road includes 11 miles of paved highwaysouth from Talkeetna to East Sunshine Lake. From the lake, animproved road heads east by northeast 3 miles to Montana Creek.Crossing the north fork, the improved road continues to the middlefork of Montana Creek where it follows the creek bottom 3 miles ormore 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 grainedquartz diorite with accessory biotite. Rock from this source will meetthe sizes required by careful blasting. Adequate rock appears to beavailable, but no estimate of reserves will be forthcoming until exploratorytest pitting or drilling is accomplished to establish the dimensionsof usable rock.8-5

SECTION 9 - DEPARTURES FROM PROJECT DOCUMENT9.01 Departures. The project plan as described in the project documenthad rock revetted s lope protection extending 1,500 feet downstream fromthe railroad bridge and constructed on the existing left bank of theTa I keetna River. The mai n departures in the proposed plan from theproject document are the additions of a 600-foot dike, 740 feet of gradingand seeding, and the extension of the bank protection further downstreatmto afford protection from the Susitna River.9.02 Reason for Departures. The reasons for departures from theproject document plan fall into categories of changed erosion conditions,as well as additional protection desired. As the Talkeetna River has againshifted to skewed flow pattern through the bridge, the authorized bankrevetment by itself was considered inapproppriate to meet the present conditionof flow pattern and desi red protection. The di ke downstream of therai Iroad bridge is to direct flows through the bridge opening and to preventdirect attack by the Talkeetna River on the community. The graded andseeded protection is to provide bank stabi lization from river overdikeflows. Extending the authorized bank revetment further downstream isto provide the community additional erosion protection from the SusitnaRiver.9-1

SECTION 10 - ENVIRONMENTAL CONSIDERATIONS10.01 General. The purpose of this section is to review the impact ofproject construction along the left banks of the Talkeetna and SusitnaRivers at Talkeetna, Alaska. This analysis is composed of two parts;a review of existing conditions and resources, and a commentary onenvi ronmenta I impacts to be expected from the proposed project. Sourcesof information include reports of Federal and State agencies, comments ofinterested citizens, and onsite observations by Corps of Engineers personnel.A draft environmental impact statement was filed with CEQ on9 May 1974. Exhibit 2 is the Fish and Wildlife Service report.10.02 Existing Conditionsa. Wilderness Areas and Wild and Scenic Rivers. The Talkeetnaarea is not located with a designated wi Iderness area, nor have any of thestreams in the area been proposed for inclusion in the wi Id and scenicrivers system.b. Historical and Archeological Sites. Exami nation of the NationalRegister of Historic Places, as required by the National Historic PreservationAct of 1966, indicates there are no officially designated archeologicalor historical sites within the project area at Talkeetna. At the present timethe State recognizes prt of the Talkeetna area as the Talkeetna HistoricDistrict. This district includes the original townsite, the Alaska Railroadright-of-way and reserve, and the cemetery reserve. At this time, theTalkeetna 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 projectarea does not involve the removal or elimination of any of these historicsites or structures.c. Vegetation. The vegetation of the Talkeetna area consists ofintermixed forest and muskeg. Overstory in the immediate project areais composed primari Iy of paper birch, cottonwood, wi lIow, and alder.Understory in the immediate project area is composed primarily ofyarrow, sorrel, fireweed, clover, horsetai I, and cow parsnip.d. Mamma Is. Terrestrial wi Idl ife I iving in the project area wouldinclude only sma II mamma Is such as voles and lemmings because theclose proximity of the human community has caused big game speciesto avoid the area.e. Birds. Habitat in the project area is ideal for a variety of songbirds.f. ~ish. Major spawning runs reach the upper headwaters andstreams 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 thetwo rivers. They begin their mass migration in early spring after winteringin the Susitna River and lower end of the Talkeetna River. Whitefish10-2

TABLE 1. Talkeetna and Susitna Rivers Fisheries DataSpec iesChinookCohoPinkChumSockeye (spring run)(summer run)Ra inbow TroutDolly VardenGraylingAdult Fish ReturnMid-May - 1 JulyMid-July - December1 July - September1 July - SeptemberMid-May - 1 JulyJuly 1 - SeptemberMid-AprilMid-AprilAprilSmolt MigrationMay - JuneMay - JuneMarch - AprilMarch - AprilMay - JuneMay - JuneMay - JuneMarch - Apri Iand burbots (ling cod family) exist in large numbers in the Talkeetnaand Susitna Rivers. However, no data are available on the migrationand/or spawning habits of these two species.g. Rare and Endangered Species. According to the publishedlist, "Rare and Endangered Fish and Wildlife of the United States, IIissued by the Fish and Wildlife Service, there are no rare or endangeredwildlife or fish species known to inhabit the project area.10.03 Environmenta I Impacts. The environmental impacts associatedwith the construction of the proposed project can be categorized underfive basic categories: project construction, river morphology, quarryexcavation, water quality, and human ecology.a. Project Construction. Identifiable impacts resu I ting from projectconstruction 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 constructionoperations.4. Temporary increase in noise during construction operations.5. Visual impact of structural measures.6. Provide bank stabi I ization, protection from bank erosion byfloodwaters of the Tal keetna and Susitna Rivers.b. River Morphology. Construction activities are not anticipatedto effect erosion downstream of the project, to disrupt river currents orflow characteristics of the Talkeetna and Susitna Rivers .. The proposedproject would prevent bank erosion.c. Quarry Excavation. Project construction would necessitateremoving approximately 10,000 cubic yards of stone from a designatedquarry site. Two existing quarry sites have been located. One quarryis located about 20 mi les north of Talkeetna at Curry. The quarry issituated adjacent to the railroad and is owned by the Alaska Railroad.The other quarry is located about 15 miles south of Talkeetna alongMontana Creek's middle fork. This quarry is owned by the State HighwayDepartment and has tentatively been selected as the source ofquarry rock. Temporary distrubance to terrestrial animals that inhabit10-4

the surface of the quarry and adjacent areas wi II occur due to vegetationremoval, rock blasting, and quarry excavation.d. W?ter Quality. The water quality of the Talkeetna and SusitnaRivers would be affected by increased turbidity resulting from excavationand construction activities. The increase in water turbidity of theserivers would be temporary and is not anticipated to prove detrimentalbecause these rivers are naturally very turbid during the time operationsare scheduled to commence, and these rivers also naturally experienceextreme fluctuations in sediment concentration throughout the year.e. Human Ecology. The proposed project wou Id have a beneficialimpact on the community of Talkeetna by providing bank erosion protectionfrom the floodwaters of the Talkeetna and Susitna Rivers. Thiswould result in reductions in property damage and loss for the communityof Talkeetna. Identifiable impacts resulting on human ecologyarc:1. Route and mode of transportation would introduce a safetyhazard as well as undesirable traffic conditions on the community ofTalkeetna.2. Ai r pollution due to dust generated by the increased travelof haul trucks.10-5

SECTION 11 - REAL ESTATE11 .01 General Land Description. The community of Talkeetna isnot incorporated and therefore has no zoning powers. Lands involvedin the project construction are under the direction of the Matanuska­Susitna Borough which will act as the local sponsor of the project.Lands required for construction is less than 1.5 acres. Ingress andegress to the exisitng quarry site on Montana Creek are via an existingroad, part of which crosses private land. Easements for constructionpurposes wou Id also need to be obtained.11 .02 Land Acquisition. The Federal Government is to be provideda II of the lands and rights-of-way necessary for the construction ofthe project. The project sponsor has indicated agreement to providewithout cost to the United States all lands, easements, and rights-of-wayfor 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 responsibilityof local interests, will be instructed to obtain applicable interestsin the lands required for the project. No problem is expectedfor the borough to obtain acquisition of privately owned lands, asthese are owned by advocates for bank protection. Governmentallands are also expected to be acqui red by the borough, as this landwould also have bank protection. The project sponsor is to comply11-1

with PL 91-646, as appropriate, which in part provides that a landappraisal must first be obtained and the landowner offered an amountnot less than such appraised value.Ownership of the required lands will remain in the sponsor foroperation 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 MAINTENANCE12.01 General. One annual inspection is required, preferably duringlow flows, to examine the toe of the dike and revetment. Usually, theoptimum time is just after the spring thaw or just prior to the first snowfallwhen the ground is clear of snow and ice. Special inspections shallbe scheduled immediately after a severe flood condition has ended.Dike and revetment quarry riprap shall be repaired promptly if rocksare dislodged by floating debris, or if other types of failure shouldoccur. Erosion repairs, reseeding, refertilizing, or wetting shall beaccomplished, as necessary, to keep the graded and seeded bank grassroot structure alive and intact. Since there are no operational controlson the project, the project wi II function by itself during flooding. Maintenancewill be the responsibility of the Matanuska-Susitna Borough.12.02 /\nnual Cost. Minimum repair and maintenance costs dependupon schedul ing adequate inspections followed by prompt repai rs.a. Inspections. One annual inspection during low water is essentialand the results would include a written report. One postflood inspectionis considered reasonable based on a 10-year average.b. Maintenance and Repai rs. Repai r cost for ri prap replacementwas assumed for two impact dislocations that could occur twice withinthe 50-year economic life of the project. Repair material is to be available12-1

from riprap stockpiled for maintenance use. The seeded bank isexpected to require the annual addition of some seed, fertilizer, andwater to maintain a good root system.c. Estimated Costs.(1) Annua I inspection with report(2) Annua I cost of 10-year frequencyinspection and report at $500each event(3) Annual cost of riprap repair costsfor 2 each $7,500 repairs at 20-yearfrequency floods(4) Annual cost, graded and seededbank maintenance(5) Total estimated annual costs$250.0050.00300.00200.00$800.0012-2

SECTION 13 - DESIGN AND CONSTRUCTION SCHEDULE13.01 Genera I. The existing erosion problem at Talkeetna urgentlyrequires that construction be started at an early date. With completionof plans and specifications by November in the fi rst fiscal year, advertisingand opening of bids can be accompl ished so that award can bemade by the middle of December.13.02 Proposed Schedule. Dike and revetment construction couldbe I imi ted to periods of low riverflow which normally occur between15 August through 15 May. Excavation and grading are usually limitedto times the ground is unfrozen, commencing early in June to 30 Octoberwhen subzero temperatures are possible. Ten-year snowfall recordsindicate minimal snowfall is anticipated through ~~ovember.At the lowestriverflows in September, excavation for the riprap toe is expected tobe in several feet of water. For below water riprap fill, the placingof riprap may have to be made concurrently with the excavation toprevent sand from running into the excavation. A further considerationis that the Montana Creek Road to the quarry, which traversesclose to 3 miles of streambed, is usable by equipment usually duringthe 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 later13-1

construction of the project. An alternative method wou Id be to locateand develop another quarry or allow the contractor to furnish approvedquarry stone. Considering the conditions observed and expressedabove, award of a contract by December with project completion within11 months appears to be a realistic time frame. The following bar chartillustrates a proposed schedule.PROPOSED CONSTRUCTION SCHEDULEContract AwardQuarry Operation I--~~-I-_Stockpiling at SiteSite ConstructionInitialRiver BottomInasmuch as the Susitna River is considered a navigable waterway toits confluence with the Talkeetna River it will be necessary prior toinitiation of the proposed work, to process a Department of the Armyauthorization for the construction in accordance with rules and regulationspublished as 33 CFR 209.145 "Disposal of Dredged Material inNavigable or Ocean Waters. II13-2

SECTION 14 - COST ESTIMATES14.01 Proposed PlanWork FeatureUnitUnitPriceAmountMobilization & Demobilization 1JobL. S.$30,000Subtotal30,000600' Dike:Site Preparation 1Toe Excavation & Backfil13,430Toe Excavation &JobC.YL.S.$ 3.00Disposal 1,440 C.Y. 2.50Quarry Stone Riprap 4,573 C.Y. 30.00...:-"-~""'.' .. >(42" to 18" Thickness) (includes 50 c.y. stockpile).. ~.~ Subtotal1660' Bank RevetmentGrading 1 Job L.S.Toe Excavation &Backfill 2,830 C.Y. 3.00Toe Excavation & SlopeUse 3,280 C.Y. 2.50Pit Run Riprap 4,640 C.Y. 25.00(18" thickness) (incl udes 50 c.y. stockpile)Subtotal740' Grade and Seed BankGrading 1 Job L.S.4" Topsoil & Seed 19,600 S.F. 0.252,00010,3003,600137,200153,1001,5008,5008,200116,000134,2001,2004,900400' 1 Lane Access Road with TurnourtsSubtotal6,100Clearing 3 Acres 1,500.0012' Top Width, Strip &Gravel2,400 L.S. 6.00SubtotalSubtotal for Work FeaturesContingencies (10%)Estimated Contract AmountS&APlans and SpecificationsFederal CostRoundedNon-Federal CostLands, Easements, Rights-of-Way, etc. (Project Sponsor)Total Project Cost4,50014,40018,900342,30034,200376,50022,800~OOO415,300415,00011,000$426,00014-1

SECTION 15 - PROJECT BENEFITS15.01 General. The community of Talkeetna, Alaska, population ofabout 185, is located at the mouth of the Talkeetna River at its confluencewith the Susitna River. The general economy of Talkeetna isbased on tourism and its function as a supply center. With the completionof the paved road between Anchorage and Fai rbanks, and a new pavedspur road into Talkeetna, the historic community is now more accessibleand is more frequently visited.15.02 Benefit Analysis. The benefits attributed to the proposedproject are mainly for erosion protection to the community, protectionto the railroad bridge, land stabilization, and area redevelopment benefits.Benefits are based on a 50-year economic project life and 5-7/8 percentinterest.a. Erosion Protection.(1) The prevention of loss of land due to erosion from the Talkeetnaand Susitna Rivers is taken as project benefits. More than 30 acres ofland, which is owned by the Federal Government, the Matanuska-SusitnaBorough, and private parties, could be lost due to erosion, if protectionis not supplied. In past years, the fascine has protected the communityfrom erosion along the Talkeetna River with the Susitna having anaverage annua I erosion rate of about 10 feet.15-1

Now with the imminent loss of the fascine, erosion can continueat an unchecked rate and erode the major portion of the community.About 30 acres of land, valued at $4,000 per acre, is currently inimmediate 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 thispresent unchecked erosion include private homes, historical buildings,a maintenance shop, a recreational park, a resort complex,roads, and utilities. Relocation was considered for all structures thatare in danger of being lost to erosion. Cost for relocating relocatablestructures was a mi nimum of $2,000 per structure for six units and$4,000 minimum for eight units. Other units either had a minimummoving expense at a cost higher than the units' market value or wereconstructed so as not to be relocatable. As these structures are inimmediate threat of loss, their market value has not been discountedin the erosion analysis. Costs derived in relocating structures wereestimated 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, 5-7/8percent) yielded $2,700 annua I expenses. Other structures, roads,and utilities that could not be relocated amounted to a market valueof about $250,000. Annual costs were estimated as $250,000 times15-2

0.06234 = $lS, 600. Structural losses prevented are claimed as projectbenefits and amount to $2,700 plus $lS, 600 = $18,300 annually. Totalerosion protection benefits are $18,300 plus $7,SOO = $2S,800 annually.In addition, historical buildings that are lost can never be replaced atany cost.b. Protection to Railroad Br~dge. The proposed dike immediatelydownstream of the rai Iroad bridge wi II channel flows downstream,alleviating eddy currents and subsequent scour of the rai Iroad embankment.In add ition, the di ke would save the current annual expendituresof 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 theEconomic Development Administration as being eligible for aids andgrants. A Federal project in the vicinity of Talkeetna, costing $426,000would have AR benefits which are derived as the estimated contractamount times 50 percent expended for labor of which 10 percent couldbe 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 projectare accumulated by category and are presented in the following tabulation:lS-3

ItemAmountErosion Protection $25,800Railroad Bridge Protection 5,000Area Redevelopment 1,200Tota I Annua I Benefits $32,00015.03 Benefit-to-Cost Comparison. The annual cost is based on a50-year economic life at 5-7/8 percent interest.Annual benefits from15.02 are $32,000.a. Annual CostFedera I CostInterest and Amortization ($415,000 x .06234) $25,900Non- Federa I CostMaintenance 800Interest and Amortization ($11 ,000 x .06234) 700Tota I $27,400b. BIC Ratio. The total annual benefits evaluated at $32,000compared with the total annua I charge of $27,400 yields a benefit-tocostratio of 1.2 to 1 which indicates that the improvement is economicallyjustified.15-4

SECTION 16 - DISCUSSION16.01 Genera I Comments. The authorized-unconstructed projectfor the community of Talkeetna consisted of 1,500 feet of rock riprapbank protection along the left bank of the Talkeetna River, as describedin House Document No. 34, 85th Congress, 1 st Session. The authorizedproject was classified as inactive since an existing emergency bankprotection project had been previously constructed and was preventingerosion due to the Talkeetna River flows. The emergency bank protectionproject, constructed in 1951 under Section 14 of the 1946 FloodControl Act, consisted of a timber and brush fascine to direct highvelocity Talkeetna River flows away from the community. The timberfascine has since deteriorated and does not provide the desired protection.A publ ic meeting was held on 5 January 1973 at Talkeetnato ascertain the view of local interests. Local interests have requestedimprovements to alleviate their flood and erosion problems. In thereanalysis of the authorized project, engineering and economic studieswere made as well as an environmental assessment for a project. Toprovide protection from the Talkeetna and Susitna Rivers, completeflood control protection for the whole community of Talkeetna wouldrequire a structure around the community plus an interior drainagesystem. Various methods and scope of projects were studied in providingprotection for the community. It was found that total flood control16-1

protection could not be economically justified. It was found that floodprotection would need to be limited to bank erosion protection similarto that described in the authorizing project document.Bank protection can be provided which would alleviate the continuingbank erosion. The proposed plan consists of a 600-foot dike, 740feet of graded and seeded bank, and 1,660 feet of bank revetment. Thetop of the bank protection would be the same as the existing elevationsof the left embankments.To raise the height of bank protection higher than the existingbank elevation to provide a levee in effect and, hence, provide minorflood control protection would require an interior drainage system toprevent entrapped interior surface runoff from ponding behind the leveeand causing additional damage. The elevation of the lowest pOint on theleft embankment of the Ta Ikeetna River corresponds to about the watersurface elevation of a lS-year-frequency flood on the Talkeetna. For alarger flood event, floodflows would not erode the bank but would overtopthe bank revetment. No significant damage is expected on the revetmentsince it is designed for overtopping.To channel flow away from the Talkeetna community, a di ke wasneeded. With a dike, velocities of flow were found to be of such amagnitude that a graded and seeded section would protect portions16-2

of the bank in I ieu of rock revetment along a 740-foot length of theTalkeetna. Accordingly, a graded and seeded section was incorporatedinto the project. As the reanalysis of the project continued, additionalprotection was added and it was found economically feasible to extendthe project scope to include bank protection along the Susitna River.Workshops were held with local interest groups, and they support anerosion control project of this scope based on the economic justificationsthat accrue from this project. The benefit cost ratio for a project atTalkeetna is 1.2 to 1.16-3

SECTION 17 - RECOMMENDATIONS17.01 Recommendations. It is recommended that the authorizedunconstructed project at Talkeetna, Alaska, be modified to provide forthe construction of the Talkeetna Project, herein described, at aFederal cost of $415,000and subject to the conditions of local cooperationpreviously discussed. It is further recommended that this DM beapproved and that preparation of plans and specifications be authori zedat a cost of $16,000.17-1

CORPS OF ENGINEERSN 10,500o/8.(J)w'o10Nm",IN 10,500N 10,250SEE NOSE DETAILPLATE 3TURNAROUNDtN 10,000DETERIORATEDFASCI NETURNOUTN 9,750SINGLE LANEACCESS ROADN 9,750VICINITY MAP-----400' 400' lOa' ItOO'SCALE IN FEETNOTESI ~~~G~N6~~ ~~O~O~N~~~~o6:N~E~O~6~6.0F TRACK AT ARR f11LE ros~345.68 FT. ABOVEN 9,500\1\\ ~U\lm~LEFTN 9,500U.S. ARMY ENGINEER DISTRICT. ALASKACORPS OF ENGINEERS",,,,CHOR..,,")' AI-ASiKATALKEETNA RIVER PROJECT ALASKATALKEETNA, ALASKA I100':PREPARED.~JDIKEAND BANK IMPROVEMENTSPLAN"N 9,250LPLATE

CORPS OF ENGINEERSU. S. ARMY(oenwJOINS PLATE Io10C\Ienwo10enwGRADE, TOPSOIL AND SEEDDISTURBED SURFACESWHERE W.S. OVERTOPS BANK. EXTENDSTONE TO TOP OF BANKNOTESSEE NonS ON PLATE II4'NIMUM DESIGN GRADIATIQHS ARE SHOIoiN UHDEG'[HE SECTIONS ACTUAL OUARRY OPERATION MAYREOUIRE REVISIOHN 9,000SINGLE LANEACCESS ROAD\N 9,000RIVERBED'.5'1/I/. 3- W.S.~------~~L..,i!

CORPS OF ENGINEERSU S ARMY(- ------------NOTESDI~E GROUND PROFILE, TO? OF LEFT BANK AND TOE OF LEFT BANKDATA WERE TAKEN FROM NOVEMBER 1972 SURVEY, AND SHOULD BE USEDAS APPROXIMATE ELEVATIONS. DIKE GROUND PROFiLE AND TOE OFLEFT BANK ELEVATIONS ARE SUBJECT TO CHANGE QUE TO DEPOSITIONBURIED TOE (SEE SECTION, PLATE Z)OR SCOUR.2 SEE PLATE 2 fOR TYPICAL SECTIONS3. SEE PLATE) & 2 FOR ALIGNMENTSDIKENOSE DETAILNO SCALE340U.S, ARMY ENGINEER DISTRICT, ALASKACORPS OF ENGINEERS100",,;;' ~~==~'O~O' __ ~2OO'HORIZONTAL SCALE IN FEE TTALKEETNA RIVER PROJECT, ALASKATALKEETNA,ALA3KA5' 5' 10'SUSITNA RIVER 50 YEAR FLOODQ = 243,000 cisPROFILEVERTICAL SCALE IN FEETTALKEETNA RIVER50 YR. FLOOD PROFILEQ = 84,000 cfsDESIGN MEMORANDUM NO, I PLATE 3

EXHIBITSExhibit 1Exhibit 2Exhibit 3Exhibit 4Exhibit 5River ProfileFish and Wildlife Service Report·Matanuska-Susitna Borough SponsorshipLetterMatanuska-Susitna Borough LetterDepartment of Transportation Letter

345EXISTING RAILS OF FASCINE \W.S. JUNE 20, 1973 , 336.2~~ 0 T E SBANK IMPRovEMENT PROF I LES ARE NOT TO SCALE DLJE TO CKAI~NELCURvATURE.......34...335~:>... 330..J...3253500 3600 3700 3600 3900 4000 4100 4200 4300 4400 4500 4600 4700 4600 4900 5000 5100 5200 5300HOR I ZONTAL DISTANCE I N FEETCROSS SECT ION AT 1750TALKEETNA RIVER100' 0' IDO' zoo'~"~O~RI~ZO~N~TA~L~S~C~

'...., . -, -BUREAU OF' SPORT FISHERIES AND WILDLIFEArc2 Office813 P StrectAr.chcY:1 ,-c, ,'lr- s1-;:: 99501Cobn-:-l ri:a:-lcs A. Debeliuslli.;tl'ict r:l.=:incor\L' 5];.:1 District Corps of En~incersP.\I. Eox 7002Anchor::!;c, Alaska 99510NOV 2 0 1974Co: 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 ourco~c1.ents conccrnin:.: fish

Matallllska· Susitna BOI'ou4h, ·Inc.BOX B. PALMER, ALASKA 99645 • PHONE 745-3246BOROUGH ASSEMBLYDecember 6, 1973Colonel Amos C. MathewsAlaska District EnqineerU. S. Army Corps of EngineersP. O. Box 7002Anchorage, Alaska 99510Dear Colonel Mathews:Re:Flood Protection at TalkeetnaAs a result of the appearance of Mr. Parnell of your agencyat a Borough meeting on November 20, 1973, the Borough Assembly hasadopted a resolution agreeing to maintain flood and erosion controlstructures proposed to be constructed by the Corps of Engineers atTalkeetna. Two copies of our Resolution No. 73-119 are enclosed.At the time Mr. Parnell appeared before the Assembly, heexplained that repair to the existinq fascines would give no permanentsolution to the problem found at the rivers and indicated that preliminarywork had been done on a more permanent structure but that, beforethe Corps could proceed further, the Corps would need a current resolutionof the Assembly. After discussion on the matter, the Assembly did adopta resolution on December 4, 1973.We assume this will give the Corps the information it needsto proceed on the above project.Encs. (2)Yours truly,...' /1>V"k~,/~-/ .Borough ClerkEXHIBIi 3

I-IATAtIUSKA-SUSlTIlA BOROUGIIRESOLUTIOlj SERIAL 110. 73-119A RESOLUTIOtj OF TilE ltATAIIUSKA-SUSInjA OOROIJGII AGREEING TO tlAltlTAIN FLOOD ANDEROSIO!I cornRoL STRUCTURES AT TALKEETlIA. ALASKA.WHEREAS, the United States Corps of Engineers has determined that Itis feasible to construct flood and erosion control structures at Talkeetna,Alaska; andImEREAS, the United States Corps of Engi neel"S requi res a corrmi tmentof local cooperation as a prerequisite to undertaking projects of this nature;and11HEREAS, the [lroject is necessary for the preservation of parks andrccreatlon facilitics at Tal~eetna,Alaska;NOli THEREFORE, IlE IT RESOLVED by the Assembly of the Matanuska-SusftnaUorou9i1 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

Matanllska· Stlsltna BOI'ou4h, Inc.BOX B, PALMER, ALAS KA 99645 • PHON E 745-3246DEPARTMENT OF ADMINISTRATIONDecember 4, 1974Colonel Charles A. DebeliusDistrict EngineerUnited States Army Corps of EngineersP. O. Box 7002Anchorage, Alaska 99510Subject:Talkeetna Water Erosion And Flood Control Service AreaDear Colonel Debelius:Enclosed is a certified copy of Ordinance No. 74-50 which was enacted bythe Bo'rough Assembly December 3, 1974.This service area provides the legal mechanism whereby the owners ofbenefiting property may tax themselves so that the Borough can meetits local government obligations for participating in the TalkeetnaWater Erosion Control project.WMH/jisEnclosure~2Z1Y~~Wes ;:.0{ HoweBorough Manager•EXHI8IY ,~'.

!).ULJJ: '_1 U~.'-·~lh •.,lot ..1\1"\.'01Spon~ol cd ~ ~Ior •MATAflUS/:A-SUSITrlA BOROUGH1ORDlfu\I:CE SEr.lfll NO. 74-50t': {\~~!~''''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 describedPoint of beginning being the east-west center section line where theA1as~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 AlaskaRailroad right-of-Hay in a northerly direction to a point I,there theAlaska Railroad intersects the south bank of the Talkeetna River;thence in a generally southerly d'rection to the point of confluenceof the Talkeetna and Susitna Rivers; thence generally south alongthe east bank of the Susitna River to the point of beginning: allsituated I'lithin T2611. R51'I, 5.1'1.petitioned the Borough Assembly to establish a service area to provide watererosion and flood control; and.IHEREflS. the Borough Assemo1y held public hearings on theestablishment of a service area as requested; andWHEREAS, ~ proposition was placed on the ballot at the 1974Dorough g:'1cra1 election to be voted on ~yarea; and~rnEREflS,by a vote of 27 in favor and 3 opposed;the residents of the proposed servlc!!the proposition to establish the service area was passedtlOl'1 TlJEIl.HORE. BE IT OROI\INEO:Section 1.nature and shall become a part of the Ilorough Code.Classification, This ordinance is of a permanentSection 2. Scnri1bi1ity. If any provision of this ordinanceor application thel'eof to any person or circu,"stance is held Invalid. theremainder of this ordin~nceshall not 'be affected thereby.Seclion 3. Servic!,~'cil [sj:E.!>lished·. There is hereby established'-Iatanusl:a-Susitna [)orough Service flrea t1o.y. Ta1keelna ~IatererOSion andflood cantrol. to provide water erosion and flood control within its boundarle~.Section 4 • .Jl~~. ThCl boundaries of the Mat~nuska-SusitnJIlor(lu!)h Servicc f"'ciJ ':0. 5. T,lli:eetna Wolter el'o.ioll and flood control, ~rehl'r\:hy est;",1i~,h("d JS ~bovc dt'~crlbcd.

,IISection 5. I\dministration. Matanuska-Su,sitM Borough ServiceArea 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 Iive upon its adoplion by the Borough Assembly and signature of the Mayor.Introductlon: ____________ lIFirst Reading: ____________,Public Hearing: ___________i!ADOPTED by the Assembly of the Matanuska-Susitna ~orough,this ____ day of _______" ____ t 1974.-IIAlaska,ROnald L. LarsonBorough ~'ayorAnEST:Evelyn IhompsonCorough Cl~,.1;(SEAL).IlL'.:i"'I, ! ,"i!~" . ,, ,I1I.!

, 'Jn[[' ,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..1l0AIJI'. o. I,ax ·,·;'111ANCH~II"Gl:, AL"~,I;" urnOlAugust 2 l i, J.970\.Colonel A. C. ~bLhch'sDistrict EI1(',.inccrAl;1skil District, Corps ofEngi.neers1>.0. Bo": 7002Anc!101-