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e-j TASK 1 Appendix WELL DRILLING PROGRAM Eagle River Water Resource Study Ll 'S Is, 1m; -44 A,) Municipality of Anchorage Water and Sewer Utilities 00 00011 TD 412 E34 1981 no. I LL December 1981 TASK 1 Appendix WELL DRILLING PROGRAM Eagle River Water Resource Study Municipality of Anchorage Water and Sewer Utilities A-L 14 US Department of Commerce NoAA conE.-' a,- Services Center LibrarY 2234 So uth Hobson Avenue Charkeston, SC 29405-2413 CH2M::HILL December 1981 Cover photo by: Air Photo Tech, Inc. F .4 00". + th LOYD 3 DAMRONJ 4092-E This report was prepared under the supervision of a registered professional engineer. The preparation of this report was financed in part by funds from the Office of Coastal Zone Management, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, admin- istered by the Division of Community Planning, Alaska Department of Community and Regional Affairs. K 13765. 130 PREFACE To pursue the recommendations for further study that were prescribed in the Metropolitan Anchorage Urban Study, completed by the U.S. Corps of Engineers in 19797 Me Municipality of Anchorage engaged CH2M HILL to conduct the Eagle River Water Resource Study. The purpose of the study is to investigate 'the potential sources of water supply from the Eagle River Valley. The original scope of the study comprised four tasks: Task 1 Well Drilling Program Task 2 Preliminary Damsite Investigation Task 3 Flour Water Treatment Study Task 4 Transmission Main Design Task 5, Eklutna Lake Alternative Water Source Evaluation, was added to the scope after the completion of the first four tasks. The report for each task is bound separately and is an appendix to the Executive Summary of the entire study. This Appendix I is the report for Task 1, Well Drilling Program. ACKNOWLEDGMENTS CH2M HILL appreciates the assistance provided by the following parties during performance of Task 1, Well Drilling Program: 0 The Anchorage Water and Sewer Utilities staff contrib- uted valuable information and comments during weekly task meetings, updated the task scope of work, and provided overall administrative assistance. 0 Eklutna, Inc., provided ready access to its property for the drilling program and provided pertinent information and comments at weekly meetings. 0 The U.S. Geological Survey performed the geophysical logging of the wells and made important comments at weekly meetings. 0 M-W Drilling, Inc., drilled the water wells in a. timely manner and responded resourcefully to difficult and unpredictable field conditions. 0 Geothermal Surveys, Inc., provided the personnel and equipment to perform the geothermal surveys. 0 Ranney Method Western Corporation reviewed existing data and recommended sites for shallow groundwater exploration. v NO SUMMARY AND CONCLUSI-ONS Task 1, Well Drilling Program, was the first of four tasks in the Eagle River Water Resource Study. The purpose of the study was to investigate the potential of the Eagle River Valley to sup- ply subsurface or surface water to the Municipality of Anchorage to meet projected increased water demands. The purpose of Task 1 was to locate and analyze deep and shal- low groundwater sources in the middle Eagle River Valley, up- stream of the damsite recommended in Task 2 of this study. CH2M HILL's responsibilffies were to defi-ne geologic materials above bedrock and to aid the U.S. Geological Survey (USGS) by making the CH2M HILL boreholes accessible for geophysical log- ging, providing wells for aquifer pumping tests, and facilitating sampling of groundwater quality. Eight test wells were drilled with depths ranging from 50 to 765 feet. The table on the following page summarizes the drilling. The first five wells were drilled to locate and analyze shallow and deep groundwater aquifers. These wells were drilled along two valley traverses identified by the U.S. Geological Survey, 4 miles upstream of the confluence of the Eagle River and its South Fork (Upstream Study Area). Two additional wells were drilled in the Downstream Study Area near the damsite recommended in Task 2 of this study, 2 miles downstream of the mouth of the South Fork. One shallow well was drilled near the mouth of the South Fork in the South Fork Study Area to evaluate the potential for a shallow groundwater collection system. No aquifers were penetrated that could produce enough water to meet a significant portion of the projected Municipality of Anchor- age demands. Consequently, no pump tests were performed. Very thick sequences of lake-deposited silts and clays underlie the valley upstream of the South Fork, and possibly extend downstream past the South Fork. This indicates that a deep gla- cial lake was backfilled by fine sediments that now underlie the existing valley floor. One hole near the valley center encoun- tered a poor aquifer at a depth of 690 to 750 feet, overlying bedrock. Near the recommended damsite, relatively shallow bedrock occurs on both sides of the river. It is only 20 to 25 feet deeper than the river channel. Clays and silts make up most of the formation overlying the bedrock. However, the well on the south side of the river penetrated a 5-foot sequence of water-bearing sands and gravels immediately over the bedrock. This aquifer may be able to provide sufficient quantities of groundwater for local development. vii TEST WELL DATA Wel I Depth of Depth to No. -Location Wei I Bedrock A tlui fers I Upstream Study 314a Poor or None Found Area 2 Upstream Study 765 750 Poor or None Found Area 3 Upstream Study 350 Poor or None Found Area 4 Upstream Study 130 Poor or None Found Area 5 Upstream Study 305 Poor or None Found Area 6 Downstream Study 160 130 Poor or None Found Area 7 South Fork Study 50 Poor or None Found A rea 8 Downstream Study 88 74 Fair Area aDepth at which glacial till boulder was encountered. The USGS suggested that more groundwater potential might exist in an old side channel, 800 feet downstream of this well. The side channel might have been an ancient Eagle River outlet. This area was not investigated because the old Eagle River dump might be a local source of groundwater contamination. Additionally, aquifers in the area probably do not contain enough storage capacity for the Municipality's needs because the area is too small to contain sufficient aquifer volume. Several areas were considered for shallow groundwater develop- ment, including a braided section of the stream several miles upstream of the South Fork. Of the areas considered, the mouth of the South Fork was the most promising. A shallow well near the mouth of the South Fork was drilled to 50 feet. No signifi- cant volume of water was found, and the geological formation encountered was clay from 16 feet to the bottom of the hole. Because this layer of clay would isolate a well from rapid river recharge, this area was abandoned for shallow groundwater considerations. viii The Task 1 drilling program has led to the following conclusions about the development of groundwater in the Eagle River Valley: 0 There is very little potential for a significant ground- water supply source from the Eagle River Valley. 0 Low-permeability silts and clays make up most of the subsurface geology in the middle Eagle River Valley. It is hypothesized that these fine-grained sediments filled glacial lakes to form the existing valley floor. 0 Although development of shallow groundwater might be possible in the valley, it could not fulfill the future needs of the Municipality of Anchorage. Winter flows of the Eagle River are low and cannot recharge shallow aquifers without affecting fisheries; therefore, these aquifers cannot sustain year-round demands. 0 A 70-million-gallon-per-day water source for the Muni- cipality of Anchorage from the Eagle River can be de- veloped through the construction of a dam and im- poundment of surface water. (See Appendix 11, Preliminary Damsite Investigation.) ix CONTENTS Page Preface Xcknowledgments v Summary and Conclusions vii 1 Introduction 1-1 Background 1-1 Site Description 1-4 Purpose and Scope 1-5 Limitations 1-9 2 Previous Studies 2-1 Synopsis of Previous Studies 2-1 Summary of Previous Studies 2-12 3 Test Hole Drilling 3-1 Drilling Program 3-1 Exploration and Examination of Alternatives 3-9 Summary 3-15 4 Recommendations 4-1 5 Bibliography 5-1 Exhibit. Ranney Method Western Corporation Report xi TABLES Page 3-1 Land Area Required for Shallow Groundwater Supply 3-14 3-2 Test Well Data 3-17 FIGURES 1-1 Vicinity Map 1-2 1-2 Projected Water Demand Increase 1980-2025 1-3 1-3 Eagle River Valley Test Wells and Other Subsurface Investigations 1-7 2-1 R. W. Retherford Associates Test Hole Boring Log 2-3 2-2 Tryck, Nyman, and Hayes Test Well No. 2 Boring Log 2-4 2-3 MAUS-USGS Test Well Boring Log 2-7 3-1 CH2M HILL Test Well No. I Boring and Geophysical Log s 3-3 3-2 CH2M HILL Test Well No. 2 Boring and Geophysical Logs 3-4 3-3 CH2M HILL Test Well No. 3 Boring and Geophysical Log s 3-6 3-4 CH2M HILL Test Well No. 4 Boring and Geophysical Logs 3-7 3-5 Middle Eagle River Valley Geologic Cross Section 3-8 3-6 CH2M HILL Test Well No. 5 Boring Log 3-10 3-7 CH2M HILL Test Well No. 6 Boring Log 3-11 3-8 CH2M HILL Test Well No. 8 Boring Log 3-13 3-9 CH2M HILL Test Well No. 7 Boring Log 3-16 xiii 00 Chapter 1 00 INTRODUCTION The population and, thus, the water supply needs of the metro politan Anchorage area are growing rapidly. Presently, surface water from Ship, Creek and groundwater wells in the Anchorage Bowl supply most of the Municipality's water. However, if pres- ent growth trends continue, these sources will not meet future needs. BACKGROUND In 1974 the United States Congress authorized the U.S. Army Corps of Engineers to perform the Metropolitan Anchorage Urban Study (MAUS), which was completed in 1979. The purpose 7 -the MAUS was "to evaluate the adequacy of the developed water sup- ply in the metropolitan Anchorage area, to determine future water demands, to assess sources for water supply development, and to formulate water supply plans to meet the increased future demand" (U.S. Army Corps of Engineers, 1979). The MAUS study area comprised the Anchorage Bowl and the area northeast to the town of Eklutna (Figure 1-1). The projected future water demand increases, determined in the MAUS, are shown in Figure 1-2. It is expected that by the year 2025 an additional 81.5 million gallons per day (mgd) of water will be needed to meet the increased demands in the area. The MAUS report identified many potential sources of supply: Eagle River Valley groundwater; Anchorage Bowl groundwater; and surface water from Campbell Creek, Ship Creek, Eagle River, and Eklutna Lake. . Two plans were recommended by MAUS for future study. Plan IV, which ranked first environmentally and socially, included a combination of supply from Ship Creek, An- chorage Bowl groundwater, and Eklutna Lake. Plan VI, which ranked first on an economic basis, included an increased supply from Ship Creek, winter diversion from Eagle River, further cle velopment of Anchorage Bowl groundwater, and exploration for Eagle River Valley ground water. To implement portions of these plans, the Municipality increased the existing water supply from within the Anchorage Bowl by re- cently constructing a 36-inch supply main to its water treatment plant from the military diversion facility on Ship Creek. Future developments are expected to include new wells to increase groundwater supply and the expansion of the capabilities of the plant that treats Ship Creek water. However, rapidly growing demands in Anchorage will require development of a new source outside the Anchorage Bowl within the next 10 years. The Eagle River-Chugiak-Eklutna area, northeast of Anchorage, needs a new source now. 1-1 C> 0 0&12 1010 b C@a CIO o 0 C0, TZ-N Z9. 0 KNIK kIL iN LD GLENN 0 IR OD P ERS ET CREEK EKLUTNA LAKE CHLIGIAK f SOUTH TOWN OF STUDY EAGLE RIViR RR GROUND BRIDGE P T M ST D A FORT RICHARDSON "ELMENDORF EAGLE RIVER -1MR FORCE BASE DOWNST AM." VALLEY ? STUDY AA.',.A EKLUTNA ANCHORAGE RI GLACIER CHUGACH MOUNTAINS EAGLE GLACIER N 0 Miles 5 Figure 1-1 Vicinity Map 1-2 0 c WATER DEMAND INCREASE (mgd) 4:h z 1980 0 0 m -4 :3 T CD 1985 CD 1990 CD CL 0 1995 0 0 2000 3 m n PL 2005 m 2010 -0 -n 0 0 am q %5.c (D -q 2015 0 (D m (D CL 2020 00 Q 16 (D 2025 0 "T " 10 01 (D 3 CL As a result of the MAUS findings, the Municipality decided to investigate potential sources outside the Anchorage Bowl that could supply 70 mgd of water. On the basis of the MAUS popu- lation projection, this diversion would satisfy the demands of the entire study area through the year 2012. The future increases in water supply capacity that are expected to be developed within the Anchorage Bowl will delay the need for the full 70-mgd capac- ity of the new water source outside the Bowl until approximately the year 2020 or later. The Eagle River Valley is one possible source of water from out- side the Anchorage Bowl that was suggested in the MAUS, Plan VI. To investigate the potential of this valley to supply the 70-mgd requirement, the Municipality engaged CH2M HILL to con- duct the Eagle River Water Resource Study. The original scope of the study comprised four separate tasks: 0 Task 1, a well drilling program to study the feasibility of developing the Eagle River Valley as a groundwater source 0 Task 2, a preliminary damsite investigation to determine the feasibility of developing the Eagle River as a sur- face water source 0 Task 3, an investigation to determine if the glacial rock flour in the Eagle River water is removable by conventional treatment processes 0 Task 4, a preliminary design of a pipeline to transport groundwater or surface water from the Eagle River Valley to Anchorage Each task was conducted independently. The results of the first four tasks clearly indicate that a substan- tial dam and reservoir are required to develop Eagle River as a water source. Before committing itself to this dam and reservoir project, the Municipality of Anchorage increased the study scope to include Task 5, Eklutna Lake Alternative Water Source Evaluat- ion. Task 5 analyzed the capability of Eklutna Lake to supply the 70 mgd of water to the area. Eklutna Lake is included in Plan IV of the MAUS. The lake is 30 miles northeast of downtown An- chorage and 16 miles northeast of the Eagle River (Figure 1-1). PURPOSE AND SCOPE During the MAUS the Corps of Engineers considered recommend- ing a deep and shallow groundwater exploration program in the Eagle River Valley as a possible future action. However, the Corps recommended against developing deep groundwater because it doubted that deep groundwater production, even if available, would be economically feasible. 1-4 The Corps believed that induced infiltration (shallow ground- water) development could provide a summer water supply to aug- ment a proposed winter river diversion. This combination would provide a dependable year-round water supply to Anchorage. The Corps recommended a hydrogeological survey to determine the potential for development of an induced infiltration source as a summer water supply. The U.S. Geological Survey (USGS) conducted a surface geo- physical survey of an area in the Eagle River Valley 4 miles up- stream of the South Fork (see the Upstream Study Area in Fig- ure 1-3). The 1981 report on this work states: Interpretation of electrical resistivity and seismic refraction data collected in one area of the middle reach of the Eagle River valley indicates that at most points along the explora- tion lines, the depth to bedrock below the valley floor varies between 350 and 450 feet. Two, and perhaps three, major unconsolidated sedimentary layers are inferred to overlie bed- rock. Other significant layers may exist that are not recog- nizable from the sounding data. As a result of the MAUS recommendation, the USGS interpretation, and the Anchorage Water and Sewer Utilities' (AWSU) desire to obtain a quantitative assessment of the availability of ground- water in the Eagle River Valley, AWSU included a comprehensive drilling and testing program as part of the Eagle River Water Re- source Study. This program was the study's first and most im- portant task, Task 1, Well Drilling Program. For the Task 1 drilling program, CH2M HILL was contracted to define geologic materials above bedrock and to aid the USCS by making the CH2M HILL boreholes accessible for geophysical log- ging, facilitating the sampling of groundwater, and providing wells for aquifer pumping tests. The program was designed to be conducted under two drilling schedules: 0 Schedule A. The AWSU and the USGS specified that 12 test sites be drilled to explore for aquifers. These sites were located along and between two cross-valley traverses that were previously identified by the USGS. These traverses are near the center of the valley, 7 to 8 miles upstream of Glenn Highway. See Figure 1-3, Lines A and B. 0 Schedule B. Two test production wells and four obser- vation wells were to be installed if developable aquifers were found during the Schedule A activities. These wells were to be located near the individual Schedule A test wells that encountered aquifers with a potential of over 300 gallons per minute. 1-5 CH2M HILL provided the engineering management services, field inspection, and engineering for this task. This included the se- lection and retention of a drilling contractor; the field supervision of percussion (cable-tool) and air-rotary drilling; coordination with Eklutna, Inc. (the land owner), AWSU, and USGS; the for- mulation of and recommendations for variations in the original Task 1 scope; and the preparation of this report. CH2M HILL was to provide the following deliverable products for Task 1: 0 Map indicating the location, and identity of wells drilled for this task 0 Driller's log of each well 0 USGS geophysical logs and notes 0 Induced infiltration analysis 0 Production test results 0 Water quality analyses 0 Positive and/or negative conclusions and recommenda- tions These products are included in this report, except for the pro- duction test results and the water quality analyses. No develop- able quantities of water were found on which to obtain these data. This report analyzes the previously collected data as well as data collected in this task and provides conclusions regarding the via- bility of developing groundwater in the Eagle River Valley to meet the future demands of the Municipality of Anchorage. SITE DESCRIPTION The Eagle River Valley runs generally east-west and is located approximately 18 miles northeast of Anchorage within the Chugach mountain range (Figure 1-1). The Eagle River begins at Eagle Glacier and flows northwest through the valley for approximately 35 miles to the Knik Arm. The valley is characterized by a typ- ical U-shaped cross section formed by past episodes of glaciation. Alluvial, glacioalluvial, lacustrine, and deltaic sedimentary de- posits fill the valley basin. The steep mountain walls along the valley are composed of varying types of bedrock, including un- differentiated older metamorphic and assorted nonmarine sedimen- tary units. The valley floor is characterized by a low-relief flood plain consisting of alluvial sediments including gravels, sands, sifts, and clays. 1-6 0 E E89fe Rive CAmOgroon 4 1.00 DO e, uil S TU15 AREA- SOU'TH..F 00 #6 STUDY ARE....- ,OLD EA t RIVER D U 0 #8 00 'Zoo m Dri 8 J lod, 7 ou cl, 00 'A LEGEND SOUTH FORK STUDY AREA UPSTREAM STUDY AREA DOWNSTREAM STUDY AREA CH2M HILL ( 1980- 1981 CH2M HILL ( 198,1 CH2M HILL ( 1980-1981 1 TEST WELL: #7 LINE A LIN - - ----- 2 TEST WELLS: - 06, 418 1 TEST WELL. 05 8 SHALLOW THERMAL PROFILE U.S. ARMY CORPS OF ENGINEERS 1976) 7 SHALLOW THERMAL PROFILE _7 HOLES ( NOT SHOWN ( MAUS - USGS HOLES ( NOT SHOWN 6 DAMSITE TEST HOLES 1 TEST WELL: ERTW- 76 LINE B 0 4 TEST WELLS: #1 THRU 04 U.82EOLOGICAL SURVEY ( 1979 ) TRYCK, NYMAN & HAYES ( 1973) 7 SHALLOW THERMAL PROFILE 1 ELECTRICAL RESISTIVITY 1 TEST WELL: ERTH *2 HOLES ( NOT SHOWN SOUNDING SITE U.S, GEOLOGICAL SURVEY R & M CONSULTANTS, INC. ( 1979 ) 1979 - LOCATIONS NOT SHOWN) ELECTRICAL RESISTIVITY SOUNDING LINE A SITES (NOT SHOWN, 2 ELECTRICAL RESISTIVITY PORTIONS ON LINE C) SOUNDING SITES 1 SEISMIC REFRACTION ROBERT W. RETHERFORD ASSOC. ( 1966 SOUNDING SITE V 1 TEST HOLE LINE B 3 GEOPHYSICAL PROFILES ( NOT SHOWN 4 ELECTRICAL RESISTIVITY SOUNDING SITES STATE OF ALASKA ( 1971-1972) 3 SEISMIC REFRACTION 0 7 TEST HOLES SOUNDING SITES 13 3 BRIDGE FOUNDATION BORING$ Task 1, Well Drilling Program, was designed and undertaken spe- cifically to address the capability of the glacial valley sediments to provide an adequate supply of groundwater to the Anchorage area. LIMITATIONS This report was prepared for the use of the Anchorage Water and Sewer Utilities for specific application to the Eagle River Water Resource Study, Well Drilling Program, in accordance with gen- erally accepted engineering practice. No other warranty, expressed or implied, is made. The wells indicate only the sub- surface conditions at the well locations. Interpolation between wells was used for conclusions. Variations from the predicted re- sults might exist. Should such variations be found, the findings and recommendations of this report will no longer pertain unless CH2M HILL is given the opportunity to reevaluate them in light of the new findings and report on the reevaluation in writing. 1-9 NO Chapter 2 NO PREVIOUS STUDIES There has been limited exploration for groundwater in the Eagle River Valley prior to this study. Studies have been conducted that have speculated on the overall well-yield capacity of the val- ley. Two studies included the drilling of deep test wells. SYNOPSIS OF PREVIOUS STUDIES The following studies in the Eagle River Valley, which relate to this task, are listed in chronological order: 1. R. W. Retherford Associates and Adams, Corthell, Lee, Wince and Associates, 1966. Preliminary Engineering Report, Eagle River Project, Anchorage, Alaska. For the City of Ancorage Municipal Light and Power Util- ity. Federal Power Commission Project No. 2045. 2. Tryck, Nyman & Hayes; Dames & Moore; and Leeds, Hill & Jewett, Inc., 1973. Anchorage Water Sources. For the Anchorage Water Utility and to Central Alaska Utilities. 3. U.S. Geological Survey, 1974. Geology and Ground- water for Land Use Planning in the Eagle River-Chugiak Area, Alaska. Open file Report 74-57. Prepared for the Greater Anchorage Area Borough. 4. U.S. Geological Survey, 1977. Ground Water Investi- gation at the Alluvial Fan of the South Fork Eagle River, Ancorage, Alaska-Results of Test Drilling, 1976. Open File Report 77-493. Prepared for the Municipality of Anchorage. 5. Quadra Engineering, Inc., 1977. The Eagle River Community Water Supply and Distribution Pre- pared for Alaska Department of Environ- mental Conservation. 6. R&M Consultants, Inc., 1979. Eagle River Water Supply Study, Meadow Creek Area, Alasa, Final Report. Pre- pared for the State of Alaska Department of Environ- mental Conservation. 7. U.S. Army Corps of Engineers, Alaska District, in con- junction with the Municipality of Anchorage, 1979. Metropolitan Anchorage Urban Study, Volume 2, Water Supply. 2-1 8. U.S. Geological Survey, 1981. Surficial Geophysical Data for Two Cross-Valley Lines in the gliddle Eaqle ff Fv-e r -V a I Fe _y. Open- File ReFo-rt 8d'--2oT6-. 77-epared in cooperation with the Municipality of Anchorage. The remainder of this chapter is a discussion of these studies and their pertinence to this Task 1 study. 1. Preliminary Engineering Report, Eagle River Project, Anchorage, -A-1-aska (Retherford) This report describes five potential hydroelectric power sites within the Eagle River drainage basin. Two of these sites are on Eagle River. The 'lower of the two sites was studied in more detail than the other site. It is located in the southeast corner of Section 13, Range 1 W, Township 14 N, about 1-1/2 miles southeast of the town of Eagle River (1,000 feet downstream of the damsite that was proposed in Task 2 of this study). The geologic portion of the investigation of this site includes information gained from seismic profiles and one 240-foot-deep test boring that included a materials log and field permeability tests (Figure 2-1). The report emphasizes subsurface geologic condi- tions, including estimates of the depth to bedrock. On the basis of three seismic profiles and the test boring, the Retherford report states: The site is generally characterized by fairly deep and heter- ogeneous deposits of sands, gravels, clays, and silts exhib- iting a complex stratigraphy. The only subsurface correla- tion available is with test hole no. 1 (the 240-foot boring) which showed a sequence of undifferentiated, very dense, alluvial deposits, primarily gravels. Noting that bedrock was not encountered in the test hole, the report states that the top of the rock, which was estimated by seismic surveys to be approximately 240 feet deep at the test hole location, is uncorrelated with known rock depths and is subject to revision. This test hole is located in Figure 1-3. Although the report did not consider groundwater capabilities, it mentioned artesian flow from L@e test boring at 10 gpm. Field perEneabilities ranged from 10 cm/sec (gravels) to less than 10-U cm/sec (sand, silt, and clay mixture) . No conclusions about groundwater potential could be made from the report. 2. Anchorage Water Sources (TNH Study) Chapter 7, Eagle River Wells, of Anchorage Water Sources, indi- cates that a shallow aquifer and @i -deep aq-7 fer ii_x-istnear the confluence of the Eagle River and the South Fork. A 445-foot- deep test hole (see Figure 1-3, Well ERTH No. 2) encountered the shallow aquifer between 33 and 42.5 feet and the deeper aquifer at depths greater than 300 feet (Figure 2-2). 2-2 0- 0- VERY DENSE, GRAVELLY SAND. 10- 10- 0. .. .- ';: OCCASIONAL COBBLES -b. 20- GRAVEL 20- VERY DENSE. CLAYEY SANDY VERY DENSE, SILTY SANDY GRAVEL VERY DENSE, SANDY GRAVEL 30- SILTY SANDY GRAVEL 30- 0 VERY DENSE, SANDY GRAVEL VERY DENSE. SILTY SANDY GRAVEL 40- 77. 40- VERY DENSE, SANDY GRAVEL VERY DENSE. SILTY SANDY GRAVEL VERY DENSE, SANDY GRAVEL 50- 0 -VERY DENSE. SANDY GRAVEL W/TRACE OF SILT -MEDIUM DENSE, SILTY SANDY GRAVEL Go- ;kVERY DENSE, SILTY FINE TO MED. SAND 60 -C DENSE, SANDY GRAVEL, WITRACE OF SILT 70- -VERY DENSE, SANDY GRAVEL 70- 0 Z.@F@ -SLIGHTLY PLASTIC SILT 80- :1., -VERY DENSE, SANDY GRAVEL 80- 0 VERY DENSE, WELL-GRADED SAND VERY DENSE. SILTY SANDY GRAVEL VERY DENSE. SANDY GRAVEL 90- VERY DENSE. SILTY SANDY GRAVEL 90- VERY DENSE, SILT, SAND, GRAVEL, LAYERED 100- 100- -0 -VERY DENSE, CLAYEY SILT, PLASTIC 110- 110- -VERY DENSE, SANDY GRAVELLY 120- CLAYEY St T, SLIGHTLY PLASTIC 120- x X. @VERY DENSE, FINE SANDY SILT 130- 130- HIGH DILATANCY. NONPLASTIC 4.Z.'.; -VERY DEN 140- SE, WELL GRADED SAND 140- X71 %ZIF VERY DENSE, GRAVELLY WELL- GRADED SAND -VERY DENSE, SILTY SANDY GRAVEL 150- 150- VERY DENSE, SILTY WELLQRADED SAND C 160- -VERY DENSE, SANDY GRAVEL, WELL, 160- GRADED 41 170- 170- 0 VERY DENSE, SILTY SANDY GRAVEL 0 180- 180- 4 7 -VERY DENSE, SILTY SAND 190- -//@' 190- -VERY DENSE, SILT 200- 200- /0,@ -VERY DENSE. GRAVELLY SILTY SAND 210- '1'1@'./!@ 210- C 220- -VERY DENSE, GRAVELLY 220- COARSE SAND 230- VERY DENSE, SILTY SANDY 13RAVEL 230- _JVERY D NSE, GRAVELLY WELL_GRADED S D@ 240- AN , ARTESIAN WATER 240'a AT 10 GPM TO SURFACE 10-6 10-5 10-4 10-3 10-i 1CF, PERMEABILITY cmisec SOURCE: R.W. Retherford Assoc. 1966. Figure 2-1 R.W. Retherford Associates Test Hole Boring Log 2-3 NATURAL GAMMA GAMMA TOPSOIL, DRK. BROWN EL. 345 0 __RAY NEUTRON GAMMA /GRAVELLY SILT UNIT 1: SAND & GRAVEL. WELL GRADED, GRAY TO GRA@-BRN., SILTY THROUGHOUT MOST 0- OFINTERVAL. 0 NSAND & GRAVEL, GRAY, CLEAN 50- NO SILT SAND & GRAVEL, DRK. GRAY, SILTY %UNIT 2: SILT, DRK. GRAY, SATURAT z ED LOOSE TO 67 FT. w 100 Z @- SILT & CLAY, DRK. GRAY, WET, C) Z PLASTIC, SOFT, LOCAL TRACES CC0 OF SAND & GRAVEL AS ISOLATED FRAGMENTS w PROBABLE LAKE SEDIMENT w 150- SILT & CLAY, AS ABOVE, BUT GRAY-BROWN 200-2 HEAVING SILT: WATER LEVEL x ROSE 100 FT. OVERNIGHT _j (L -< w 250- 0: UNIT 3: GLACIAL TILL. SILTY,SANDY GRAVEL,GRAY,DENSE,GRAVEL& SAND PARTICLES. ONE ANGULAR GRAYWACKE ROCK FRAGMENTS z 300- UNIT 4: GRAVEL & SAND, GRAY, ;o SILTY. INTERBEDDED COARSE 0"0 GRAVELLY SAND & SILTY FINE SAND. PROBABLE OUTWASH .:0 ALLUVIUM DEPOSITED BY 350- 2 '.. ANCESTRAL EAGLE RIVER 9 '' 0 qc, 'PRINCIPAL CONFINED AQUIFER, WATER FLOWS TO SURFACE CLEAN GRAVEL STREAK AT 386'-389' 400- GRADATIONAL CONTACT UNIT 5: GLACIAL TILL. SILTY WATER SAND, GRAY, VERY DENSE, WITH 0. RARE ANG CONTENT ULAR GRAVEL 450--J INCREASES FRAGMENTS RADIOACTIVITY DENSITY INCREASES INCREASES __j SOURCE: Tryck, Nyman, and Hayes, et .91. 1973. Figure 2-2 Tryck, Nyman, and Hayes Test Well No. 2 Boring Log 2-4 This report contains the most positive evidence and conclusions to support the existence of substantial groundwater potential for municipal use in the Eagle River Valley. On the basis of a 24-hour pumping test of the shallow aquifer, the report indicates an initial specific capacity of the shallow aquifer to be 31 gpm per foot of drawdown. * The report states, "A water yield of approxi- mately 775 gpm (1.1 mgd) should be possible if the drawdown were increased to 25 feet." The report indicates that, from 14-minute and 16-minute bailer tests, the specific capacities of the deeper aquifer at 344 feet and 346 feet were- found to be 4 gpm per foot and 16 gpm per foot, respectively. The deeper aquifer is noted as a series of outwash sands and gravels interlayered with silty sand. This report states in its analysis of the test hole and the pumping and bailer tests that "properly developed large diameter wells may yield water in excess of 1 mgd from Unit 1 (the shallow aquifer) and over 3 mgd from Unit 4 (the deeper aquifer)." It says the pumping and bailer tests indicate that the aquifers have sufficient potential to warrant consideration of Eagle River groundwater as a potential water supply for the Anchorage area. Additionally: It is quite reasonable to expect specific yi,elds of 10 to 20 % in Eagle River alluvium but if it is assumed that the surficial aquifer in Eagle River has a specific yield of 5 % only 3.8 square miles 30 feet thick would be required (for a 40-mgd yield). Either the surficial or deep aquifer alone, therefore, should be able to provide the Anchorage area's needs for additional water. Finally: The analysis of the Eagle River well project is based on the assumption that sustained yields will average 1.3 mgd per well from the deep aquifer. The single test well drilled in conjunction with this project provides inadequate information upon which to design and evaluate this project; however, until additional information is available, it must be used. Thirty wells in the Eagle River Valley of 2-mgd capacity would be required to furnish the area needs in the design yea r. This provides a capacity of approximately 1.5 times the annual average demand of 40 mgd. A possible well field arrangement is shown on Figure 254 (in the TNH report) for cost analysis, but actual locations must be based on test drilling. 2-5 3. - Geology and Ground Water for Land Use Planning in the Eagle River-Chugiak Area, Alaska (USGS) This report indicates that, because large alluvial fans generally contain deposits favorable fo r groundwater exploration, the greatest potential for ground-water development exists in the larger alluvial fans. Specifically mentioned is the Meadow Creek fan. This USGS report was based on existing well logs and pro- duction data, and it contains little information about the ground- water potential in the area studied in Task 1 of the Eagle River Water Resource Study. The report does show several wells located near the Glenn High- way bridge and the Eagle River Campground. Most of these were installed by the State of Alaska and have low yields, from 1 to 72 gpm. Bedrock near the river ranges from 40 to 107 feet below ground level. A bedrock outcrop is shown in the river about 1/2 mile upstream of the Glenn Highway bridge. 4. Ground Water Investigation at the Alluvial Fan of the South Fork-Eagle River-7-0-srs) This investigation was conducted as a phase of the water availa- bility and water supply element of MAUS. Its primary purpose was to evaluate the potential of the aquifers described in the 1973 report of Tryck, Nyman & Hayes (TNH). A test well, ERTW-76, was drilled into bedrock at a depth of 487 feet, approximately 195 feet down-valley from the TNH well. The well location is shown in Figure 1-3. According to the USGS, the lithologic sequence of the test hole drilled for this project was similar to that logged in the 1973 TNH test hole (Figure 2-3). However, the shallow aquifer found in the TNH test hole between 33 and 42.5 feet correlated with only 1 foot of relatively permeable aquifer material (at a depth of 48 to 49 feet) in the USGS test hole. This led the USGS to conclude that the shallow aquifer, tested by TNH to have a specific capac- ity of 31 gpm per foot of drawdown, has a limited areal extent. Test pumping by the USGS of individual aquifer zones below 300 feet indicated that no water-bearing strata capable of sustain- ing moderate-to-large yield public supply wells (200 gallons per minute or more) are present. The report states: The well penetrated four sand and gravel strata of low water-yielding capacity .... Each water stratum was pumped for several hours, and the best aquifer yield was found to be 1.7 gal/min/ft of drawdown. These test results support the conclusion, previously inferred from drilling data at a nearby test hole drilled in 1973 (TNH), that larger yield, confined aquifers are not present in the subsurface at this locality. 2-6 0 71 C in NATURAL GAMMA- GAMMA GAMMA NEUTRON CD 0 INCREASING INCREASING INCREASING 0 GAMMA BULK TOTAL 12. RADIATION DENSITY POROSITY 0 0) 0 COUNTS PER SEC. COUNTS PER SEC. COUNTS PER SEC. CD 20 60 3000 5000 400 800 0- 7`49? VIL T 40 T T 4000 600 0 T T T T 01JAVel, 60LI)EIZ9 WL :-4 C14V, 4POIZAOIC 6114VEL I I I 20- &lzdilez, a. o>,Oml) I 1 1 20 4AIII) 2@ 0, ILI, &IZ4 I/e it V WL 40- 4147 40 0 IZ4 IIEZ, W4 T--jZ)- A107 LOW YIELD AOUIFER 76,CFED, 13117 walao MAr.- 00mcomC w-rL1 60- -60 80- 80 100- q it I; L 7. euZA V, 4 Orr -100 120- -120 140- -140 160- 160 ,;III; COAlf.41,VIA16- 5901eekl ISO- rz 0 C le, D/Z K. alm V, '? of 7 -180 gftr, L1i9,'1r0r1z,4V, 40FT 200- -200 CONT.411.11AIC, lzocle, 61ZAY 220- -220 -aeAVEL; ;I(,Tv umEmTeD 240- 240 @260- @260 Lu In -11,4t1ejjYCEA4EMrED, Velf WARR 280- 280 ..04t1f; C4606AITCO, 300- -300 -.; 41jtrrt-,e wAre)z -320 320- @,;ur & &ZA Y61; A141ZD -4/6T & CIZAVeL; ;OFT 340- -340 -Cd-W- V RE C -D r-A Cra.db'& e, 4AA10; LA1,4TER :gU -IF t 44AID; PlAle &RAV61 e, 4AA10; CEMEAireD 360- 0 INov I I log 360 G24VE1 & ;4AIIJ; WArjelZ I Dec 13 log (rIZA VEL 4A AJO 6. 1 it, r Nov 11 log -380 380- ROCK; IU109EAI, CEMEAlIff) 8" Casing Nov 11 logl Dec 13 log 7 - Dec 13 log Caliper Log 400- --w&Z41(eL, ';A1jq,, W4rf1Z 6" Casing Dia. in. 400 91ZOXCAI, t6MCAUEO 6 7 114AW W1 Wfifg@; "Of Tf,5r.-,0 T 1700CRIZOIZ6AI, C6,WCA1146n Gluva w1raw4ree 420- Zoe/," 40IJ3 g- 511-r -420 tCem51JTb9 to 4WJt.) 1?117O41EA1 IZ#Cle,' C6MeWeO 440- 131zoKeAl lucle; q1t7V -440 qAA117v, eemeljr-cl) 'I -69 - - - - - - - Xvivrrom ai-atm-- - xacle; fildleo e,4,;INC 4150- 0 x 110cie, 40--1 a 416 IV -460 Lu ROCK: IWLCI). A1.440 -TI 480- 706M, A1,4110 z 480 0 SL 2OCK; [/.-/ZY UARO 1 40 100 67 1 C 40 COUNTS PER SEC. 600 _q 5 0'0j N.11.9 COUNTS PER SEC. COUNTS PER SEC. 500 te.; mleu,;ceeened over 11if io in terma I - 0 CA ca *40 -rltd@?,a fe,- ;1Oi,;z-;e of screen uf 111000's MCA. C) 0 rumped @dfallml@r. for Zh,- uJI'M 181t. of drawdowtt; temp L.8*C; eaftd 480 vmtta4; 4&jr'c w4tee level > (j) 0 bailfd 4t taboul 15 pl.1mi'n. wilit tnuadramdown; wouldtof detylop due to ft'ne malert'al; AtImped 4,6,vut 1,5 fal/mrn. wi'th much drawdown; 4iiatz? burwr leyel polvinf; co,,td Z30 C),Icreeti not Inqazled, 9pen Itele Zjf; pumved -35 @vr Z fir Ivi'th z4ft. drawdejute; ib-oq 9z 4 s?pzt?IZ; temp 7 506; tonj 600 amllof; ;t4i i't water leyel ahotle 4 It As a part of the conclusions of this report, the USGS noted: Also, because only 1 foot of relatively permeable aquifer material (at a depth of 48 to 49 ft.) was penetrated in the unconfined system in ERTW-76, the extent of the shallow aquifer tested at well ERTH #2 is questionable. However, a surprisingly large yield (60 gal/min) was pumped from a 12-ft-deep, open-end casing beside the new test well, which suggests an abundance of very shallow groundwater here. 5. The Eagle River Community Water Supply and Distribution Plan (Quadra) The purpose of this report was to compile and analyze existing data on the potential water supply sources for the Community of Eagle River. No field exploration was conducted. This report notes that: ... the data (are) inconsistent and often conflicting (from previous studies in the area of Eagle River). Additional field work will be required before the true capabilities of the Eagle River aquifers can be determined. On the basis of previous reports, Quadra chose to assume for the purpose of its study that the underflow of Eagle River will pro- duce sufficient quantities of good-quality water to meet the needs of the community. The report further assumed that a shallow- aquifer well field could be located adjacent to the Eagle River in Sections 17 and 18 of T14N, R1W, with each well having a poten- tial production capacity of 450 to 500 gpm. 6. Eagle River Water Supply Study, Meadow Creek Area, Alaska (R&M) -The emphasis of this study is on the surface water and ground- water potential in the Meadow Creek area, north of the Eagle River Valley. The study includes detailed hydrologic and geologic investigations of the Meadow Creek area, including geophysical surveys, well drilling, and test pumping. No test holes or wells were drilled to test the aquifer character- istics 'or well production capabilities in the Eagle River Valley. Geophysical surveys run in the Meadow Creek area and the Eagle River area suggest that subsurface geologic conditions in the lower Eagle River Valley are similar to the Meadow Creek fan area to the north. 2-9 In its conclusions, the R&M report states: Interpretations developed in this study support the conten- tion that aquifers within the glacial till including the Meadow Creek Fan, are discontinuous and restricted. Relative to this comparison, the report states in its description of a test pumping of a well on the Meadow Creek fan that: The most significant result of this pump test is the discovery that the producing formation has physical limits at the test pumping rate (165 gpm). This observation supports the (R&M) concept that the good producing zones in this area are discontinuous and vary greatly in lithology from place to place. 7. Metropolitan Anchorage Urban Study (MAUS), Volume 2, Water Supply (Corps of Engineers) Section 4, Groundwater - Eagle River Valley, of Appendix 3, Potential Water Resource Development, of this MAUS report con- tains a discussion of previous study in the Eagle River Valley, the 1976 MAUS-USGS test well, its recommendation for a future testing program, the feasibility of groundwater development in the Eagle River Valley, and the impacts of groundwater development. Because the results of the TNH (1973) and MAUS-USGS (1976) test wells have not provided conclusive results on the potential for development of Eagle River groundwater, this MAUS report notes the need for a future testing program: Ground water aquifers in the Eagle River valley warrant continued consideration as a potential water supply for the Anchorage area. However, explorations to date have not been sufficient to determine overall aquifer characteristics .... these characteristics should be determined by a comprehen- sive field exploratory program. The Corps suggested a deep, confined aquifer testing program consisting of four wells drilled to bedrock. Locations for these wells are shown in Figure 3-154 of the MAUS report. It also suggested that a shallow aquifer testing program be conducted, consisting of one test well drilled 4 miles upstream of the conflu- ence of Eagle River and South Fork. This test well't location is also shown in Figure 3-154. If a shallow aquifer were found, numerous observation wells and seismic data would be required for definition of the aquifer. However, the report recommends against an extensive drilling and testing program: 2-10 The estimated cost of approximately $65,000,000 for a (groundwater) project, which would supply an average of 40 mgd to the Anchorage area is clearly excessive.... Therefore, it must be concluded that development of deep groundwater in the Eagle River Valley would not be feasible, regardless of whether or not the assumptions made about its availability are correct. Accordingly, an extensive drilling and testing program would not be justified. The MAUS report does suggest that it may be prudent to conduct an analysis of shallow induced infiltration potential: If the formation beneath Eagle River should prove to be of sufficient permeability to make the use of the induced infil- tration method practical, a considerable reduction in the cost of development would be possible. Because of the relatively low surface flow in Eagle River during the winter, it is' possible that this method would be productive only in the summer months. 8. Surficial Geophysical Investi ation Data for Two Cross-Valley - D-n-esin the Middle Eagle River Valley, __(`0-!;7C_S) The work for this report was conducted in the area of the middle Eagle River Valley because in this reach, Eagle River and the North Fork meander on a flat, broad valley bottom that is swampy in places and that probably has a shallow water table. Seepage .into small tributary channels had been noted by USGS. Because of these features this area was expected to have a greater groundwater potential than areas downstream. Six vertical electrical resistivity soundings and four seismic re- fraction soundings were made along two cross-valley traverses (Lines A and B, Figure 1-3). The following quotes summarize this report: The work described in this report appears to have served well as a means of supplying basic subsurface information in a small segment of the Eagle River valley. Geophysical sounding data for the valley bottom, alluvial reach that extends 3 miles upstream and downstream of the survey lines used in this study probably would be equally beneficial .... Interpretation of electrical resistivity and seismic refraction data collected in one area of the middle reach of the Eagle River valley indicates that at most points along the explora- tion lines the depth to bedrock below the valley floor varies between 350 to 450 ft. Two, and perhaps three, major un- consolidated sedimentary layers are inferred to overlie bedrock. 2-11 This report refers to this Task 1, Well Drilling Program, and suggests that bedrock may be deeper and that revised values will be reported when more information becomes available. SUMMARY OF PREVIOUS STUDIES The TNH study contains the most positive evidence and conclu- sions to support the existence of substantial groundwater poten- tial in the Eagle River Valley. Unfortunately, sufficient funds were not available to properly complete and test-pump the only well drilled. A substantial Eagle River exploratory drilling program was then developed by the U.S. Corps of Engineers and USGS. Again, sufficient funds were not available, and only one well could be drilled. This one well was located 195 feet from the TNH well to determine the extent of the aquifers that the TNH well had encountered. The results of this limited program were quite disappointing, since developable groundwater was not found. Because the South Fork area did not show potential for significant quantities of groundwater, the USCS then investigated other areas for groundwater. The limited time and budget-allowed for an investigation of a small portion of the valley using surface geophysical methods only rather than test drilling. The data from these reports led USGS and AWSU to undertake the concen- trated Task 1 Well Drilling Program for the middle of the Eagle River Valley. The program was developed to evaluate the groundwater potential of the Eagle River Valley on a scale much larger than any previous investigation. It was to be conducted along and between the USGS cross-valley geophysical lines, Lines A and B of Figure 1-3. The results of this drilling pro- gram are discussed in Chapter 3. 2-12 00 Chapter 3 TEST HOLE DRILLING The Task 1 drilling program was designed to obtain an accurate description of the lithologic materials above bedrock and to aid the USGS by providing access for aquifer pumping tests and borehole geophysical logging and by facilitating sampling of groundwater quality. Site access and necessary permits were obtained through the Municipality of Anchorage. Special cooperation by the land owners, Eklutna, Inc., and state permitting agencies allowed timely decisions regarding the execution of and changes in the direction of the drilling program. DRILLING PROGRAM CH2M HILL was authorized to begin the test hole drilling in July 1980 and subcontracted M-W Drilling, Inc., of Anchorage to supply the necessary drilling equipment and personnel to complete the task. Drilling did not begin until September 3, 1980. Delays resulted from site access problems caused by high streamflows and a desire to minimize the impact on the local environment caused by moving equipment and materials. The original plan specified that in the first phase of the drilling program, Schedule A, 12 wells were to be drilled at sites along the two cross-valley traverses, which were previously identified by the USGS. These cross-valley traverses are shown as Lines A and B on Figure 1-3 and are within the Upstream Study Area of the drilling program. Two other areas of study are identified in the figure: the South Fork Study Area and Downstream Study Area. Initial drilling began on Line B. Two percussion rigs (cable-tool) were used because they produce good formation samples and are lighter than truck-mounted air-rotary-type rigs. The lighter rigs have a minimal impact on the environment. Six-inch and eight-inch steel casings were driven as drilling pro- gressed. Eight-inch casing was used in the upper portion of Test Well Nos. 1 and 2 because these holes were expected to exceed 300 feet in depth. Telescoping 6-inch casing through the already installed 8-inch casing would allow the continuation of the holes to total depth. This system reduces the difficulty of driv- ing casing at greater depths. Schedule A focused on the drilling of 8-inch- and 6-inch-diameter test holes to identify potential aquifer zones. Cuttings were examined, and if the cuttings had indicated a potential aquifer, drive samples would have been collected to more accurately define 3-1 aquifer zones and materials. If any zones had been identified as having potential for significant water production (several feet of permeable sands and gravels), they would have been pump tested. Individual zones would have been screened using the "casing pull- back" method and pump tested. The sequence of events and the findings of each hole drilled are described in the following paragraphs (see Figure 1-3 for the locations of the individual test wells). Test Well No. 1 The drilling of Test Well No. 1 along Line B began on Septem- ber 3, 1980. One hundred ninety-nine feet of 8-inch casing was installed; the boring was then reduced to 6-inch diameter. The drilling was terminated at a depth of 314 feet on September 22, 1980, when the casing could not be driven any further. Meta I cuttings that were retrieved along with rock chips showed that the casing had bent and perhaps a large boulder or bedrock had been reached. It was decided, with the approval of the AWSU and USGS, to leave Test Well No. I uncompleted at 314 feet. The decision included the possibility of returning to the site and continuing to drill if the other test holes along Line B encoun- tered bedrock or potential aquifers at a depth greater than 315 feet. Subsequent completion of nearby Test Well No. 2 at 765 feet indicated that the rock chips retrieved at a depth of 314 feet in Test Well No. 1 were probably from a glacial till boul- der rather than from bedrock. However, because no promising aquifers were found elsewhere, Test Well No. 1 was not continued to bedrock, as had been planned. The sediments encountered in Test Well No. 1 were predominately low permeability silts and clays. Gravelly and sandy horizons were thin and rarely encountered, and those that were encoun- tered had low permeability silts and clays as matrix. The sedi- ments at this site have little potential for storage and transmis- sion of groundwater (see Figure 3-1). Test Well No. 2 The drilling of Test Well No. 2 on Line B by a cable-tool rig began on September 5, 1980. Eight-inch casing was installed to approximately 208 feet, and 6-inch casing was installed to 634 feet. In mid-October progress was stopped at 634 feet because the casing could not be driven further. Drilling was resumed on March 17, 1981, with an air-rotary rig. Revert mud was used to complete the open hole to a depth of 765 feet. Bedrock was en- countered at 750 feet. The sediments and lithologic sequence en- countered at Test Well No. 2 were similar to those encountered at Test Well No. 1. Thick sequences of silts and clays predominated the material above bedrock (see Figure 3-2). No significant aquifer material was encountered that warranted pump testing. 3-2 DRILLER'S LOG NATURAL GAMMA GAMMA-GAMMA NEUTRON THERMAL LOG Increasing increasing Increasing Temperature (degrees C) WELL NO. 1 Gamma Radiation Counts Counts 0 1 2 3 4 6 6 7 0 0 .,SILTY SAND c@ AND GRAVEL ,A,0CLAYEY Sill T 50 7 - 50 -CLAY OR SILTY CLAY 100 100 -GRAY CLAY OCCASION - ALLY SILTY OR SANDY 150 L -ISO IL LU 200 200 250 260 SANDY SILTY CLAY WITH SOM GRA EL 300 1300 350 SOURCE: Geophysical Logging: U.S. Geological Survey Figure 3-1 Thermal Log: Geothermal Surveys, Inc. CH2M HILL Test Well No. 1 Boring and Geophysical Logs DRILLERS LOG NATURAL CLAMMA GAVANA-GAMMA NEUTRON THERMAL LOG Increasing Increasing Increasing WELL NO. 2 ...me Radiation Comte Counts Temperature (degrees C) 0 1 2 3 4 a a- L GRAVEL .L., IS I @A Aipi@ LTY SAND 6 TV SAND CLAYEY OLT TO SILTY CLAY C.Al CLAY OCCASIONALLY OCT V too 2.0 SILTY SAND b.. Soo- :ILTY CLAYEY AND It 7 400- .00 CL ORAVELLY CLAY LL! - SILTY CLAY 00 CLA YET OCT ao. Boo- SILTY CLAYEY CAN. A -.91. SOO- fee- SILTY CLAY SILTY SAND A GRAVEL TOO (OLE. .'!L!L. Too- OCT A PRE 'AN. 0.0 Boo] FT SOURCE: Geophysical Logging: U.S. Geological Survey Figure 3-2 Thermal Log: Geothermal Surveys, Inc. CH2M HILL Test Well No. 2 Boring and Geophysical Logs 3-4 Test Well No. 3 The drilling of Test Well No. 3 on Line B by a cable-tool rig began on September 25, 1980, and was completed on October 3, 1980. Well No. 3 was completed entirely with 6-inch-diameter casing. The drilling was terminated at approximately 350 feet, prior to encountering bedrock, because the lithology encountered was similar to. that found in Test Well Nos. 1 and 2. These test wells were dominated by thick sequences of low permeability silts and clays that are unsuitable for test pumping or development (see Figure 3-3). Test Well No. 4 Test Well No. 4 on Line B was drilled by a cable-tool rig near the south boundary of the valley. This well completed the drilling necessary for a valley cross section along Line B. Drilling began on October 6, 1980, and was completed on October 8, 1980. Drillling was terminated at approximately 130 feet because the lithology correlated with the low groundwater potential materials encountered in the other wells along this cross section (see Figure 3-4). Test Well No. 5 The information gathered from the drilling of the four test holes along cross-valley traverse, Line B, indicates extensive lake deposits, and it was concluded that the potential for encountering significant water-bearing horizons along Line A also was very small (Figure 3-5). The environment for deposition of the low permeability clays and silts encountered in Test Well Nos. 1 through 4 on Line B can be extrapolated throughout much of the Eagle River Valley. The same conditions almost certainly existed upstream, beyond Line A. A deep glacial lake probably extended throughout a significant portion of the Eagle River Valley. Because groundwater potential along Line A was considered low, it was recommended that supplemental surface geophysical work be done in the valley to assess the potential along Line A prior to drilling. A thermal survey was conducted by Geothermal Surveys, Inc. (GSI). This survey indicated that Line A was not "particularly promising" as having significant groundwater flow beneath the site. However, because the AWSU wanted to ensure that no siz- able groundwater source existed in this area, a test hole was drilled along Line A. One of the thermal holes along Profile A (No. 5) indicated the best groundwater potential and was selected to be the site for Test Well No. 5, which was drilled with a cable-tool rig. Test Well No. 5 also encountered low permeability silts and clays similar to those found at the sites of Test Well Nos. 1 through 4 3-5 DRILLER'S LOG NATURAL GAMMA GAMMA-GAMMA NEUTRON THERMAL LOG Increasing Increasing Increasing WELL NO. 3 Gamma Radiation Counts Counts Temperature (degrees C) 0 1 2 3 4 5 6 7 0 0 -SANDY SILT 50 SILTY CLAY so SILTY CLAYEY SAND SANDY SILTY CLAY 100 100 CLAYEY SILT 150 7 150 oSANDY SILTY CLAY 200 200 SILTY CLAYEY 250 250 SAND AND GRAVEL LU ARTESIAN WATER 1/2 Win FLOW DA M @ I @ 300 300 -SANDY SILTY CLAY 350 - 350 400- 400 4:50 450 SOURCE: Geophysical Logging: U.S. Geological Survey Figure 3-3 Thermal Log: Geothermal Surveys, Inc. CH2M HILL Test Well No. 3 Boring and Geophysical Logs 3-6 DRILLER'S LOG NATURAL GAMMA GAMMA-GAMMA NEUTRON THERMAL LOG Increasing Increasina Increasing WELL NO. 4 Gamma Radiation Counts Counts Temperature (degrees C) 0 1 2 3 4 5 6 7 0 0 /SILTY SAND & GRAVEL SANDY r 50 50 SILT SANDY SILTY CLAY 100 100 'GRAY CLAY OCCASION - ALLY SANDY OR SILTY x 1- 150 150 IL LU 200 200 260 250 300 t -300 SOURCE: Geophysical Logging: U.S. Geological Survey Figure 3-4 Thermal Log: Geothermal Surveys, Inc. CH2M HILL Test Well No. 4 Boring and Geophysical Logs 500- 1600- 1600 500 1400- -1400 400- - - -400 1200- -1200 - 300- 1000- -1000 -300 Boo- Boo NORTH FORK - EAGLE RIVER - - 200- - 600- WELL -600 -200 EAGLE RIVER),/WE (W No. I EAGLE RIVER :LL N:.L@L ROAD WELL 400- :4 .4" A., , No. 4 No. 3 -400 too- - 100 200- -200 00 0- 0- LEGEND -0 0 - - Primarily Silty Sands and Gravels -200- Primarily Clay and --200 Silty Clay -too- - --too Primarily Silty and -400- Clayey Sand -400 - Primarily Talu:, Deposit or Morainal Depo Is ( not Iso'...le -600- Bedrock -600 -200- FEET FEET --200 METERS METERS Figure 3-5 Middle Eagle River Valley Geologic Cross Section (Figure 3-6). The drilling of Test Well No. 5 was halted at a depth of 305 feet because the possibility of encountering a poten- tial aquifer was considered remote. The drilling program was discontinued in the Upstream Study Area after Test Well No. 5 was abandoned. Based on the data collected from the drilling of the first five test holes, the groundwater potential in the Upstream Study Area is not adequate for potential municipal water supply. EXPLORATION AND EXAMINATION OF ALTERNATIVES Geophysical Survey Under the direction of CH2M HILL, GSI reassessed the existing geophysical data and proposed to do additional thermal sensing in the Eagle River Valley. GSI concluded that a "very accurate thermal loop" of the existing four test holes and a surface thermal grid of Line A and of the outwash deposits along Line C would be beneficial in locating additional drill sites. To conduct the bore- hole thermal survey, the following field work was required: down-hole temperature profiles were run both in the four test holes drilled for CH2M HILL along Line B and, for a background comparison, in an existing well down-valley at the Eagle River Campground. Also, shallow surface thermal profiles, which consisted of monitor- ing ground temperatures from depths of approximately 10 feet below surface, required the drilling of 22 10-foot-deep holes along three valley profiles. Two of the three profiles coincided with Lines A and B. Profile C was run down-valley below the conflu- ence of Eagle River and the South Fork at Line C (see Fig- ure 1-3). GSI completed its field work the last week of November 1980. Line C had temperatures and temperature drift that indicated a potential for groundwater. Probe sites C-1 and C-2 were chosen as having the greatest potential for groundwater flow beneath the site. Test Well No. 6 Site C-2 was chosen as Test Well Site No. 6 at GSI's recommen- dation. Drilling at Site No. 6 began January 2, 1981, and was completed January 12, 1981. Test Well No. 6, drilled by the air-rotary method, encountered what appeared to be bedrock at 135 feet below ground surface. This is about 25 feet below the level of the river. The anticipated depth to bedrock, based on logs from nearby wells and on geophysical work, had been more than 300 feet. The dril:ling of the well continued to a depth of 160 feet, still in what proved to be bedrock. Drilling was discon- tinued at 160 feet. No potential aquifers were encountered (see Figure 3-7). .3-9 0- Silty Clay 0-10, Clayey Slit w/ some Small Gravel 50- Gravelly Clay 0 0 0 0 Silty Clay w/ some Small Gravel 100- 150- LU 200- Soft Gray Clay 250 300- Figure 3-6 CH2M HILL Test Well No. 5 Boring Log 2-10 0- Organic Topsoil Sandy Gravel 00 0 Loose Gravel 00 Sandy Gravel T 20- 0 " 0'110 10 10 10 0100 40 - o i 4D Silty Gravel Some water, less than 5 gpm 0 C) 0 0 00 0 60 - 10 10 00 0 0 0 0 80 - 0 Silty Gravelly Clay LU 0 100 - 0 0 0 120 - Silty Gravel w/ Clay balls 140 - Gray Bedrock 160- Figure 3-7 CH2M HILL Test Well No. 6 Boring Log 3-11 This finding of shallow bedrock and no aquifer material resulted in a reassessment of the groundwater exploration program. GSI, after reviewing the shallow bedrock data from TeSt Well No. 6, submitted a preliminary draft report that indicated data originally thought to be anomalous or incorrect (a high temperature drift) was actually correct. High drift in temperature over a short period of time is normally the result of shallow bedrock. The GSI report included a geologic interpretation of the occur- rence of shallow bedrock at the Test Well No. 6 site. Based on field visits, air photos, and nearby well logs, the shallow bedrock appears to be the result of a ridge formed as the main glacier bifurcated and gouged around a postulated bedrock knob in the vicinity of Test Well No. 6. According to GSI, the effects of such a ridge would be the erosion of areas on either side of the ridge and subsequent deposition of outwash gravels in the eroded channels. Evidence from Thermal Probe C-1 indicated a potential for groundwater flow in the location of an anticipated outwash channel south of Test Well No. 6. The groundwater potential suggested by the thermal survey at C-1 resulted in the drilling of Test Well No. 8. Test Well No. 8 The air-rotary drilling rig began drilling Test Well No. 8 at the C-1 location on March 25, 1981. Drilling was completed on March 26, 1981, at 88 feet; bedrock was encountered at a depth of 74 feet. This bedrock level is about 25 feet below the level of the river, as encountered in Test Well No. 6. With the exception of a 5-foot sand and gravel zone between 69 and 74 feet, the subsurface materials consisted of low permeability silts and clays. The 5-foot-thick sand and gravel zone between 69 and 74 feet was too thin to justify further investigation as a source of large- volume water supply and was not pump tested (see Figure 3-8). Shallow Groundwater Potential To develop a shallow groundwater supply system, the subsurface materials need to be well-sorted sands and gravels in hydraulic communication with the river. The capacity and duration of a shallow groundwater supply system is also dependent upon its area[ extent. Assuming a 3-month duration of use during low- flow winter months at a demand of 70 mgd, a 20-square-mile area with a minimum of 30. feet of sand and gravel would be required. This estimate assumes a specific yield of 5 percent. A larger specific yield would reduce the required land area. Some additional thickness also would be required to make up for the extraction system characteristics and the freezing of surface and near-surface materials. Substantial recharge of the shallow surface materials cannot be assumed during low-flow winter months. Recharge could affect 3-12 0- Frozen Soil Slit and Sand 10- Clayey Silt 20- 30- - Silty Clay 40- LU 50- 60- 0 0 Sand and Gravel To - 0'.. 0.0. Gray Bedrock 80 Figure 3-8 CH2M HILL Test Well No. 8 Boring Log 3-13 the existing fisheries. The impact on fisheries was addressed in a letter from the State of Alaska Department of Fish and Game (concerning a dam on Eagle River--See Appendix 11, Preliminary Damsite Investigation) . This letter had the following comments: 0 If no significant fisheries are found below the damsite, a minimum river flow of 20 m9d will have to be main- tained. Studies may prove that larger minimum river flows are required to protect existing fisheries. 0 Changes in water surface on the North Fork of Eagle River could affect anadromous fish spawning habitat. Recharge of shallow subsurface materials during the low-flow winter months could reduce the downstream river flows signifi- cantly and also affect the level of water in North Fork and the mouth of South Fork. This would affect the fisheries. Table 3-1 is a compilation of land area requirements for various demands and specific yields. Table 3-1 LAND AREA REQUIRED FOR SHALLOW GROUNDWATER SUPPLY (30 Feet of Drainable Gravel) Area Required (sq mi) Specific Yield 47-mgd Demand 70-mgd Demand 5 13.5 20.1 10 6.8 10.0 A subconsultant, Ranney Method Western Corporation, reviewed the borehole information from this Task I program, previous re- ports, and other data relative to development of shallow ground- water in the Eagle River Valley. (The Ranney report is included as an exhibit to this appendix.) Ranney concluded that the lower portion of the Eagle River Valley, beginning at the South Fork alluvial fan and extending downstream to the Glenn Highway bridge, was potentially suitable for the development of a shallow groundwater supply. Specifically, the report recommended further test drilling and test pumping in the South Fork alluvial fan and at selected sites downstream to the Glenn Highway bridge. This recommendation was used in the selection of Test Well No. 7, near the Eagle River on the alluvial fan of the South Fork, and in the selection of Test Well No. 8, near the proposed damsite location. Test Well No. 8 was described in a previous section of this chapter. 3-14 Test Well No. 7 Test Well No. 7 was drilled with a cable-tool rig on March 24-25, 1981. This well was located near the TNH and the MAUS-USGS wells to confirm the reported presence of significant quantities of shallow groundwater. Shallow groundwater should be less avail- able in March than in the summer and fall. Therefore, this drilling would confirm if a year-round shallow groundwater supply is available and if induced infiltration is possible from Eagle River. Drilling was terminated at a depth of 50 feet after encountering very little water and 34 feet of clay (see Figure 3-9). Braided Channels A section of the Eagle River about three miles upstream of Line A consists of braided channels. This area was identified by AWSU as a potential shallow groundwater source. CH2M HILL and Ranney Method Western Corporation considered this area, but no test holes were drilled. Shallow groundwater is not expected to be developable from this area for the following reasons. 1. Sufficient pervious materials are not expected to exist in this area to provide sufficient storage for required demands (Table 3-1). 2. Low flows in this area will be less than those recorded at the stream gage, making storage requirements greater than those calculated for downstream areas. 3. Braided streams tend to change frequently, making consistent reliable recharge to the shallow aquifer dependent on changing stream patterns. The success of a collector well is in direct relation to its distance from the stream from which the collector induces infil- tration. 4. This area is eleven miles from the Glenn Highway and the cost per gallon to deliver water to the Municipality is expected to be high. Additionally, the water may require treatment because of the small particle size of glacial flour, which could allow the flour to move through the formation. Ninety percent of the particles are smaller than 2 microns (a micron is one-millionth of a meter), 13 percent smaller than 0.5 micron. SUMMARY Table 3-2 summarizes the drilling program. In general, no developable aquifers were found in the eight test wells drilled. 3-15 0- Frozen Soil T - 0. .0 *.0 Silty Sand and Gravel 10- 0 0 1.0 20- 30- Gray Sticky Clay 40- 50- Figure 3-9 CH2M HILL Test Well No. 7 Boring Log 3-16 Table 3-2 TEST WELL DATA Wel I a Depth of Depth to No. Location Wel I Bedrock Aqu i fers 1 Upstream Study 314 b Poor or None Found Area 2 Upstream Study 765 750 Poor or None Found A rea 3 Upstream Study 350 Poor or None Found Area 4 Upstream Study 130 Poor or None Found Area 5 Upstream Study 305 Poor or None Found Area 6 Downstream Study 160 130 Poor or None Found Area 7 South Fork Study 50 Poor or None Found Area 8 Downstream Study 88 74 Fair Area aSee Figure 1-3. bDepth at which glacial till boulder was encountered. The four wells across the middle valley along Line B provided data that indicate this portion of the valley was formed by the backfilling of a deep glacial lake with fine sediments. These sediments provide low potential for groundwater development. Bedrock is very deep. Test Well No. 2 was drilled into bedrock at a depth of 750 feet. Some silty clays and gravels were found over the bedrock, but not in quantities sufficient for development. Test Well No. 5 (Figure 1-3, Line A, upstream of Line B) and Test Well No. 7 (near the mouth of the South Fork, downstream of Line B) confirmed that the backfilled glacial lake extended throughout much of the valley. Test Wells No. 6 and 8 were drilled several miles downstream of the middle valley as a result of additional field work and data analysis. Outwash channels were expected in this area. Both of these wells hit bedrock at a depth of about 25 feet below the 3-17 level of the nearby river channel. Little water-bearing material was found over the bedrock and no aquifer pumping tests were performed. No areas were found that would justify development of an induced infiltration system. The drilling program was stopped because the data from the eight test wells were sufficient to conclude that aquifers in the Eagle River Valley are not sufficient to meet the Municipality of Anchorage's future demands. 3-18 00 Chapter 4 EN RECOMMENDATIONS The following recommendations for groundwater development in the Eagle River Valley are made as a result of the Task 1 Well Drilling Program: 0 Abandon the prospect of developing groundwater in the Eagle River Valley as a source to help meet the Municipality of Anchorage's future demands. 0 If smaller demands in the immediate area require a nearby groundwater source, investigate the outwash channels that may exist in the lower Eagle River Valley. The second recommendation is based on the assumption that glacial outwash channels do exist and should yield moderate volumes of water. However, this area can be compared geolog- ically to the Meadow Creek fan area (R&M Consultants, Inc., 1979) and although individual wells may be capable of significant production, the geologic conditions are such that total production from several wells might be limited. Additionally, shallow bedrock lies upstream and downstream of the Eagle River Campground. Shallow bedrock and low permeability silts and clays were found upstream of the proposed damsite (Figure 1-3, Line C). A bedrock outcrop exists in the river at the upstream end of the campground. Downstream of the camp- ground at the Glenn Highway bridge, bedrock is very shallow (see attached exhibit). Shallow bedrock can limit the amount of water that is available. Therefore, the availability of ground- water may be limited in the lower Eagle River Valley. 4-1 Chapter 5 BIBLIOGRAPHY Anchorage Water Sources. Prepared for the Anchorage Water Utility and the Central Alaska Utilities. Anchorage, Alaska: Tryck, Nyman & Hayes; Dames & Moore; and Leeds, Hill & Jewett, Inc. 1973. The Eagle River Community Water Supply and Distribution Plan. Prepared for Alaska Department of Environmental Conservation. Anchorage, Alaska: Quadra Engineering, Inc. 1977. Eagle River Water Supply Study, Meadow Creek Area, Alaska, Final Report. Prepared for the state of Alaska, Department of Evironmental Conservation. Anchorage, Alaska: R&M Consul- tants, Inc. 1979. Preliminary Engineering Report, Eagle River Project, Anchorage, Alaska. Prepared for the City of Anchorage Municipal Light and Power Utility. Anchorage, Alaska: R.W. Retherford Associates and Adams, Corthell, Lee, Wince and Associates. Federal Power Commission Project No. 2045. 1966. U.S. Army Corps of Engineers, Alaska District, in conjunction with the Municipality of Anchorage. Metropolitan Anchorage Urban Study, Volume 2, Water Supply. 1979. U.S. Geological Survey. Geology an Ground Water for Land Use Planning in the Eagle River-Chugiak Area, Alaska. Open File Report 74-57. Prepared for the Greater Anchorage Area Borough by C. Zenone, H.R. Schmoll, and E. Dobrovolny. Denver, Colo- rado (published by the Anchorage Area Borough). 1974. U. S. Geological Survey. Ground Water Investigation at the Alluvial Fan of the South F Eagle River, Anchorage, Alaska - Results of the Test, Drilling, 1976. Open File Report 77-493 for the Municiality of Anchorage. 1977. U.S. Geological Survey. Surficial Geophysical Data for Two Cross-Valley Lines in the Middle Eagle River Valley, Alaska. Open File Report 80-2000. Prepared in cooperation with the Municipality of Anchorage by Larry Dearborn and Donald H. Schaefer. 1981. 5-1 2 1 Exhibit Ranney Method Western Corporation Report IRANNEY METHOD WESTERN CORPORATION WATER SVPPLY ENCINEERS AND CONTRACTORS March 9, 1981 P. 0. BOX 6387 RANNEY COLLECTORS KENNEWICK. WASHINGTON 99336 SURFACE WATER INTAKES TELEPHONE: (509) 58-A@47 ARTIFICIAL RECHAROING CONSTRUCTION DEWATERING CH2M Hill P.O. Box 2088 Redding, California 96099 Attention: Mr. Ramond L. Moresco Chief Hydrogeologist Re: Municipality of Anchorage, Alaska - Eagle River Shallow Ground-Water Study Gentlemen: We have reviewed the existing information, reports and data recently transmitted to us,and are setting forth our preliminary evaluation and recommendations regarding the development of a shallow ground-water supply from the alluvial deposits adjacent to and underlying the Eagle River. (1) Location and Hydrogeology: The locations of existing wells and test holes within the study area are shown on the Location Map in Figure SW-95-Pl and the upper portions of their logs are given in Figure SW-95-P2. In general, the lower valley of the Eagle River is underlain by shallow deposits of sands, gravels, cobbles and/or boulders, extending from ground surface to a maximum observed depth of about 50 feet. These sand and gravel deposits are quite variable in character, containing clay zones at some wells and being described as "silty," at others. Underlying these shallow sands and gravels is a rather thick zone of impermeable material, generally described as grey silt or grey clayey silt. It is, of course, only the shallow deposits above this zone that are of interest for a shallow ground-water development. It is probable that these shallow sands and gravels are in hydraulic contact with the Eagle River and that free inter- change of water between the river and the aquifer occurs. Thus, a shallow ground-water development could rely upon a dependable source of recharge by induced infiltration from I I C(D ?? the river. The specific areas where geologic data are available are described in detail as follows. ASSOICIATED WITH: RANNEY METHOD WESTERN OF CALIFORNIA. INC. RANNEY INTERNATIONAL. S.A., 186 AVENUE LOUISE. BRUXELLES, BELGIUM CH2M Hill Mr. Ramond L. Moresco March 9, 1981 Page 2 (2) Eagle River (Ford) Campground: this area is located along t'he South bank of the Eagle River just upstream from the Glenn Highway bridge. Bridge borings at the Glenn Highway bridge encountered bedrock, described as claystone, at depths of only 4 to 6 feet below ground level (1 to 6 feet below river level). However, three wells drilled by the State of Alaska in the Eagle River Campground (Wells 14-3, 14-4, and 14-5) showed bedrock occurring at depths of 47 and 107 feet. The locs of these wells show water-bearing sands, gravels and boulders extending to depths of 45 feet, with the most favorable material appearing to extend to a depth of 24 to 26 feet. The Quadra Engineering Inc. report describes two of these wells as follows: "Both wells are 30 to 35 feet deep and are producing 200 to 250 gallons per minute without substantial drawdown." Based upon the foregoing, it would appear that this area is potentially suitable for a shallow ground-water supply. It is noted, however, that bedrock outcrops in the riverbed at the upstream end of the campground, thereby limiting the area available for development. (3) Proposed Damsite: The proposed damsite is about 1 mile upstream from the Eagle River Campground. Retherford Test Hole 1 showed sand and gravels extending from ground surface to a depth of 49 feet, the materials encountered appearing to be somewhat similar to those encountered at the campground and therefore potentially suitable for development. However, CH2M Hill damsite boring B-5, located adjacent to the river and on the north bank, showed only 8 feet of silty sand and gravel ,underlain by silty sands, clay, and clayey gravels. (4) South Fork Alluvial Fan: In 1973, Tryck, Nyman & Hayes drilled a 6-inch diameter test hole, referred to as ERTH-2, to explore the materials underlying the South Fork Alluvial Fan. The log of this test hole revealed the existence of a shallow ground-water aquifer, extending from ground surface to a depth of 52 feet. The materials encountered consisted of silty sand, gravels and cobbles, with a silt free zone occurring from 33 to 42.5 feet. A slotted well screen was installed in the zone from 33 to 38 feet and the well was pumped con- tinuously, at a constant rate of 350 gallons per minute, for a period of 24 hours. The drawdown stabilized at 11.3 feet after 5 hours of pumping. This is considered to be a highly favorable production for a 6-inch diameter well and would CH2M Hill Mr. Ramond L. Moresco March 9, 1981 Page 3 indicate an aquifer having a moderately high permeability. If the aquifer is proven to be in hydraulic contact with the river, the probable yield of a single radial collector well (Ranney Collector) could be expected to be in the order of magnitude of 5 MGD. A subsequent test hole drilled in 1976 by the USGS, referred to as ERTW-76, showed silts, sands and gravels extending from ground surface to a depth of 49 feet. However, a silt zone occurred in the interval from 30 to 48 feet, i.e., that zone which was indicated as being most productive at ERTH-2. Although the USGS test hole did not confirm the areal extend of the aquifer shown to exist at ERTH-2, the USGS report contains the added comment, "a surprisingly large yield (60 gal/min) was pumped from a 12-ft. deep, open-end casing beside the new test well, which suggests an abundance of very shallow ground water here." The South Fork Alluvial Fan is considered to be the most favorable area encountered, based upon existing well data. Preliminary geologic mapping by the USGS shows that this alluvial fan has a width.', along the river, of over 2000 feet. This would be sufficient-distance for 4 to 5 radial collector wells (Ranney-Collectors) or a potential yield of 20 to 25 MGD. (5) CH2M Hill Lines B & A: At Line B, Wells 4, 2 and 1 showed silty sands and gravel extending from ground surface to depth of 20 to 30 feet while Well 3 showed only sandy silt. Similarly, Well 5 on Line A did not show any shallow water-bearing materials, the materials encountered consisting of silty clays and clayey silts. It is concluded that this area is not suitable for the development of a shallow ground water supply. (6) Summary and Recommendations: Based upon the foregoing geologic data, it appears that the lower portion of the Eagle River Valley is potentially suitable for the development of a shallow ground-water supply, although present well data are insufficient to confirm the magnitude of such a development. Specifically, we recommend further test drilling and test pumping in the South Fork Alluvial Fan and at selected sites in the valley extending downstream from the alluvial fan to the Glenn Highway bridge. CH2M Hill Mr. Ramond L. Moresco March 9, 1981 Page 4 This test drilling and test pumping program is generally outlined as follows: a. The test holes should be a minimum of 8-inches in diameter and should be drilled with a cable tool rig using the "drive and bail" technique. b. The test holes should be located as close as practicable to the Eagle River and carried to a depth of 50 feet or until the first significant layer of impermeable material is encountered. c. Where water-bearing materials are encountered, small rate testing should be carried for preliminary (field kit) determinations of water quality. d. An experienced hydrogeologist should be on the site throughout the test drilling program to select drilling sites, visually observe and log the test holes, and direct all drilling activities. e. At sites selected from the results of the test drilling, detailed pumping tests should be conducted to determine the permeability of the aquifer,-the infiltration rate of the river bed, and all other data necessary to the evaluation of the ground-water potential of the site. f. As a minimum, each detailed pumping test should consist of the drilling of a 10 or 12-inch diameter pumping well, equipped with a suitable screen, and three 8-inch diameter observation wells. The pumping well will be pumped continuously, at a constant rate, for a period of at least 48 hours or until water levels have become sufficiently stabilized to make the neccessary hydraulic determinations. Water levels in observation wells and changes in river stage will be recorded continuously, by means of automatic water level recorders, throughout the test period. Near the end of the test, water samples will be collected for laboratory determinations of water quality. We believe the testing program, as outlined above, will provide the data required for determining the feasibility of a shallow ground-water supply in the lower Eagle River Valley. If you have any questions or wish to discuss this program in further detail, please let us know. We are returning your reports under separate cover. Very truly yours, RANNEY METHOD WESTERN CORPORATION C. -@VvdA-& Frederick C. Mikels, P.E. President & Chief Engineer FMC/sk Area TOWN OF -,,E LE ER BRIDGE B$ 17 IN W-4-0 BEDROCK 0 TCA'9P 819> - 44- N 4 3 b 14-, 500 D FOR CH2M Soo 55 R 11. .N TH-2 T FOAXA - I 1@1 I UVI 1@1 \\V1 0 0 C O@ -6 2000 scale e 6f-- ------ GLENN HIGHWAY DAMSITE BORINGS BRIDGE BORINGS STATE OF ALASKA RET14ERFORD CHZM HILL CH2M HILL LINE B LINE A NO. 2 NO 14- 3 14-4 1 B-2 B-3-A B-313 14-5 TH. I B ERTW-76 ERTH-2 NO. 4 1 NO@ 3 No. 5 0- 0 7- 0*a k 0 0. Q 0.- 0 '0 0 0 0. w lo- .0 :0 0 .0. 0 NO LOG 0 0 20 -.6 6_61 .10 0 7-. 0 A CC 30 /;Q w 00 0 (L 40- w 777 CA. 50 L E G E N D CLAY GRAVEL BEDROCK 0 RANNEY METHOD F SILTY COBBLES OR WESTERN CORPORATION 1 F BOULDERS KENNEWICK, WASHINGTON CH2M HILL SAND STATIC WATER LEVEL EAGLE RIVER WATER STUDY OR RIVER LEVEL ANCHORAGE.ALASKA LOGS OF WELLS DRAWN@ M S E I APPROVED: DATE 3-9-81 ING, SW-95-P2 0 Logs of Wells I TASK 1 WELL DRILLING PROGRAM Eagle River Water Resource Study (0 C) 0 zv m-@n CD "Ct A 4 4 0 0 4 Cf)