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Bradley Middle Fork Erosion Study 2003 1
Alaska Industrial Development and Export Authority Alaska Energy Authority January 5,2004 Mr.Harry T.Hall Federal Energy Regulatory Commission Portland Regional Office 101 S.W.Main Street,Suite 905 Portland,Oregon 97204 Subject:-Bradley Lake Hydroelectric Project,FERC License 8221, Middle Fork Diversion Erosion Study Dear Mr.Hall: AEA's Middle Fork Diversion Erosion Study,prepared by R&M Engineering consultants,is enclosed. Study -results indicate that erosion is likely to be self-limiting by reaching equilibrium or bedrock and recommends against performing any remedial,work at this time.Photographs:included with the studyfrom1990and2003indicatethatarelativelysmallamountoferosionhasoccurredinthelast13years. R&M Engineering recommends continued active monitoring,an annual evaluation of monitoring results, and preparation.of a remedial action plan.AEA concurs with and intends to implement the consultant's recommendations. If you would like to discuss any aspect of the study please do not hesitate to call me or contact ourengineeringconsultantatR&M,Mr.John Magee,at (907)522-1707. hadaay \,Establish data ceportyy'Project Manager Formert Enclosure 2.Contre monitor + )notes t+loyainy ¢cc:J.Magee,R&M,Inc.Photes Raging chanel) D.Bowes,PE ;vk J.Thrall,MMI 3.Ranesty <valvete sstabiftyJ.Miyashiro,FERC con panrernenrre File C1 PoO-ge Sowumonhy Bradley Lake O&D Committee:"4,More FRQ monitomag, John Cooley,CEA S.Prepare remehia)Doug Hall,ML&P.ac tren”' Henri Dale,GVEA plan ' Bob Zacharski,HEA Tom Kelley,MEA Das CETT 813 West Northern Lights Boulevard *Anchorage,Alaska 99503 ,907 /269-3000 *FAX 907 /269-3044 ¢Toll Free (ALASKA ONLY)888 /300-8534 *www.aidea.org LR CSMR&M CONSULTANTS,INC. 8101 Vanguard Drive,Anchorage,Alaska 99507 January 2,2004 Mr.Art Copoulos Project Manager Alaska Energy Authority 813 West Northern Lights Blvd. Anchorage,Alaska 99503 (907)522-1707,FAX (907)522-3403,www.rmconsult.com Project No.:251123 RE:Bradley River Middle Fork Diversion Erosion Study Final Report Dear Mr.Copoulos: Enclosed are four (4)copies of the Final Report for the Bradley River Middle Fork Diversion Erosion Study for your use. This report is based on field observations and analyses by R&M personnel and geophysical work by our sub-consultant,Northland Geophysical,PLLC. We are available at your convenience to discuss the content of this report and welcome your comments. Thank you for the opportunity to be of service to the Alaska Energy Authority. Sincerely, R&M CONSULLTANTS,Inc. MeeehnK.Magee,P.E. Senior Engineer Enclosures (4 copies of noted report) cc: Jim Thrall,MMI (1 copy of enclosure) Z:/project.02/251123/middle fork erosion study/erosion study report (Sradleg File \\-a) Alusha imousing!ceeh pment amd Expect Avathosibs Alaska tnery Authonty BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY FINAL REPORT December 2003 R&M CONSULTANTS,INC. 9101 VANGUARD DRIVE ANCHORAGE,ALASKA 939507 Tel:(907)622-1707 722M R&M CONSULTANTS,INC.(907)522-1707,FAX (807)522-3403,www.rmconsult.com 9101 Vanguard Drive,Anchorage,Alaska 99507 January 2,2004 Project No.:251123 Mr.Art Copoulos Project Manager Alaska Energy Authority 813 West Northern Lights Blvd. Anchorage,Alaska 99503 RE:Bradley River Middle Fork Diversion Erosion Study Final Report Dear Mr.Copoulos: Enclosed are four (4)copies of the Final Report for the Bradley River Middle Fork Diversion Erosion Study for your use. This report is based on field observations and analyses by R&M personnel and geophysical work by our sub-consultant,Northland Geophysical,PLLC. We are available at your convenience to discuss the content of this report and welcome your comments. Thank you for the opportunity to be of service to the Alaska Energy Authority. Sincerely, R&CONSULLTANTS,Inc. apehnK.Magee,P.E. Senior Engineer Enclosures (4 copies of noted report) ce: Jim Thrall,MMI (1 copy of enclosure) Z:/project.02/251123/middle fork erosion study/erosion study report Alaska Industral Devclopment and Export Authority Alaska Energy Authorivy BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY FINAL REPORT December 2003 R&M CONSULTANTS,INC. 9101 VANGUARD DRIVE ANCHORAGE,ALASKA 995607 Tel:(907}622-1707 3S sata 2 Coton a eg ho W/2N JALAN Ee Oe,Nes tomy anny BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY FINAL REPORT TABLE OF CONTENTS Description Page Number Executive Summary ...........ccccecccsscccseeeseeseesesscesecseseeesseesseeeseeeeseeesaeeses 1 IMtrOductiOn...............ccssccessssccceceecsssscesesseessssssesscsscesssscsssecsesccssssstseeesecs 2 Project DeSCriptiOn ........ce eeecsseseeseeseeseescesccsececeeeseaeeseeseeseeesesseeeeeaees 2 Field investigations...cecececcsssesceccecesececceesessescensceeceseeseesceseecenees 4 DISCUSSION ...........cccccccsesseseceeesssccecesseesecesseccessscceseesscesassecesssusenssssesesnss 5 COMNCIUSIONS ..........c:cccessscsscceesssececsesseececeseecceessecersssceescucssceussesecseceeesenss 7 ReCOMMENAAMIONS ............cccsssscccesssescecsecccceesesseseessecseeessccesscsessueeensenss 8 Figures Figure 1 -Location Map,Vicinity Map,Project Map and Area Map Figure 2 -Bradley River Middle Fork Diversion -Diversion Channel Plan Figure 2A -Bradley River Middle Fork Diversion -Diversion Channel Plan With Photographs of Features Inserted Figure 3 -Bradley River Middle Fork Diversion -Channel Profile And Typical Sections Figure 4 -Photographs of Original and Existing Conditions,Stilling Basin / Right Bank Erosion Area Figure 5 -Photographs of Original and Existing Conditions,Steep Channel / Drop Structure Erosion Area Figure 6 -Seismic Refraction Profile SR-2 Figure 7 -Seismic Refraction Profile SR-3 Appendicies Appendix A -Historical Photographs, Sub-Appendix A1 -Photographs dated 8/09/90 Sub-Appendix A2 -Photographs dated 9/03/02 Sub-Appendix A3 -Photographs dated 11/07/02 Sub-Appendix A4 -Photographs dated 8/29/03 Appendix B -Report on the Results of Seismic Refraction Investigation by Northland Geophysical,PLLC. RD BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY EXECUTIVE SUMMARY The Middle Fork Diversion redirects flows from the upper reaches of the Bradley River to the Bradley Lake Reservoir.The Middle Fork Diversion was established by constructing a 1,600-foot long unlined open cut excavation through rock and overburden in 1990 and was described in Project documents as a small intake basin and two reaches of open channel separated by a Stilling Basin which is located in a natural bog area.See Figure 2A for a photo-illustrated Plan of the Diversion. During the annual FERC inspection of the Bradley Lake Hydroelectric Project in August 2002,a concern was expressed by the inspection party that the erosion noted along the right bank of the Middle Fork Diversion in the area of the Stilling Basin feature could be a problem in the near future due to the erosion possibly cutting through the right bank into a minor drainage channel to the adjacent Bradley River Tributary Area.R&M Consultants,Inc.was retained to evaluate the diversion channel erosion and make recommendations regarding the need for corrective remedial measures to secure the integrity of the diversion channel function. Field investigations were conducted in 2002 and 2003 that focused on flow conditions and progress of erosion of the right bank in the Stilling Basin area.No detailed investigations were conducted on the Intake Basin or channel downstream to the Drop Structure.A geophysical seismic refraction investigation was performed to define the subsurface conditions along the right bank of the Diversion Channel at the Stilling Basin and under the adjacent Waste Fill Area #2 and to aid in the evaluation of erodability and stability of the right bank of the diversion channel.Present channel configuration and physical conditions were compared to project construction records to better understand the diversion channel design and construction details and to aid in estimating future channel alignment and stability. The field investigation and analysis of project records found that not only is there erosion of concern in the area of the Stilling Basin,but a steep section of channel excavated in bedrock and overburden has been eroded to a flatter slope for about 250 feet upstream from the Stilling Basin and a Drop Structure has formed in the bedrock excavation at the beginning of the formerly steep channel section.This Drop Structure is a source of boulders and cobbles that are transported downstream as the bedrock continues to erode and the left and right banks along the degraded channel are a source of finer grained material as the banks continue to erode.It was also determined that Diversion now comprises four definable Reaches rather than the two reaches originally described at Project inception. Our conclusion from this investigation and analysis of results is that no remedial corrective work to limit erosion and stabilize channel banks in the area of the Stilling Basin is required at this time but the Diversion Channel erosion should continue to be regularly monitored and remedial action to control bank erosion in critical areas taken in the future if bank erosion is not significantly reduced by establishment of natural equilibrium in the channel or bank erosion reaching underlying bedrock. We recommend the Middle Fork Diversion continue to be monitored and a photographic record of channel conditions from the Intake Basin to the Marmot Creek intersection be updated through regular inspections by project operations personnel to allow continuing evaluation of channel changes and erosion conditions,particularly along the right bank at the Drop Structure and Stilling Basin areas. S11 Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 2 INTRODUCTION The Middle Fork of the Bradley River was diverted from its natural course to flow into the Bradley Lake Reservoir via Marmot Creek as part of the development of the Bradley Lake Hydroelectric Project (Bradley Lake HEP)in 1990.The open cut,unlined diversion channel is excavated through bedrock and overburden (soil and glacial till)and is a project feature included in regular project operations inspections and in FERC annual inspections. During the August 2002 FERC annual inspection of the Bradley Lake Hydroelectric Project a concern was expressed by the inspectors that the developing erosion noted along the right bank of the lower reach of the Middle Fork Diversion could be a problem in the near future due to the erosion/undercutting of the channel bank and possible eventual cutting of a channel through into the adjacent Bradley River Tributary Are.While not a safety issue,this would effectively negate the benefit of the Middle Fork Diversion to the Bradley Lake HEP. R&M Consultants,Inc.was retained to evaluate the diversion channel erosion and make recommendations regarding the need for corrective remedial measures to secure the integrity of the diversion channel function.R&M's evaluation included performing a review of historical records and field investigations at the Middle Fork Diversion area. PROJECT DESCRIPTION The Middle Fork of the Bradley River naturally flows into the Bradley River near Kachemak Bay. The upper reaches (watershed above about elevation 2,170 feet)of the Middle Fork of the Bradley River has been diverted from its natural course to flow into the Bradley Lake Reservoir via Marmot Creek as part of the development of the Bradley Lake Hydroelectric Project;See Figure 1 which shows Location,Vicinity,Project and Middle Fork Diversion Area Maps.The Middle Fork Diversion is located about one mile to the North of Bradley Lake.Historical photographs of the Middle Fork Diversion are included in Appendix A (Sub-Appendicies Al through A4). The Middle Fork Diversion comprises a 1,516-foot long open cut,unlined channel from the Intake _Basin (approx.2,170 feet elevation)on the Middle Fork of the Bradley River to intersect with a channel about 80 feet long to Marmot Creek (at approx.2,125 feet elevation)which then directs flows over Marmot Falls into the Bradley Lake Reservoir.The Board of Consultants Final Report of 1992 describes the Middle Fork Diversion as "a small intake basin and two reaches of open channel ......separated by a stilling basin which is located in a natural bog area,all of which was established by excavation”.A detailed plan of the Diversion Channel is shown on Figure 2;this is excerpted from the original construction plans and shows the horizontal alignment and features of the Diversion Channel and is annotated to point out features of concern in this study.This plan apparently depicts the Middle Fork Diversion "as-constructed”.Figure 2A is a Photo-illustrated Plan of the Diversion similar to Figure 2 but that provides images of the various features of the Middle Fork Diversion. Due to erosion and down-cutting of the natural materials in portions of the original unlined channel and the existence of bedrock control downstream from the stilling Basin the effective number of Reaches has increased and,at the time of the present study,the Diversion Channel now comprises four definable Reaches which are: RSM Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 3 I -the reach from the Intake Basin at Station 0+00 to the Drop Structure at about Station 7+00; II -the reach from the Drop Structure to the Stilling Basin at about Station 12+00; III -the reach from the Stilling Basin to a channel contraction identified herein as the Bedrock Control feature at about Station 13+00 formed by the channel section in rock excavation between the rock knobs immediately downstream from the Stilling Basin,and; IV -the reach from the Bedrock Control feature to the intersection with the channel of Marmot Creek at about Station 15+20. During construction,waste rock and overburden materials from channel excavation was placed in one of three Waste Fill Areas which were developed as shot-rock armored (6 feet thick armor) embankments of undifferentiated waste from channel excavation.These were each constructed as a regular trapezoidal cross-section (see Figure 3). As-constructed,the diversion channel slope was 2 percent over much of its length except for a 200-foot long steep (14 percent slope)section immediately upstream from the Stilling Basin and a zero percent slope through the Stilling Basin.Figure 3 shows the Diversion Channel as- constructed profile and typical cross-sections of the Diversion Channel at various locations and the typical cross-section of the Waste Fill Area #2 embankment. The Diversion Channel was constructed with a bottom width of 10 feet minimum and with a bottom sloped at 5 on 1 transversely from the right bank to the left bank which effectively puts the thalweg of the channel along the left bank.Side slopes of the channel were designed as 1 on 4 in rock cut and nominally 2 on 1 in areas of overburden excavation.The overburden in the vicinity of Waste Fill Area #2 comprises approximately 6 feet of organic and mineral soil over glacial till of variable depth up to about 30 feet (based on the seismic refraction investigation).The diversion channel bottom extends into the glacial till.Alluvial deposits along the right bank in the area of the Stilling Basin consist of silty-sandy gravel,cobbles and boulders from erosion in the channel upstream from the Stilling Basin. As noted above,the diversion channel was excavated through bedrock and overburden comprising a soil layer (about 6 feet thick)over glacial till at a slope of nominally 2%throughout its course except for the steeply sloped (14%)section between Stations 7+00 and 9+00 that has eroded since construction into a steep chute in bedrock that functions as a Drop Structure at the head of Reach II,about Station 7+00,and about 250 feet upstream from the Stilling Basin at the foot of Reach II. The Reach II channel downstream from the Drop Structure curves to the left to the Stilling Basin then curves to the right as Reach III through the Bedrock Control feature,formed by a contraction in the channel section in rock excavation between two rock knobs immediately downstream from the Stilling Basin,to become Reach IV which ends at the intersection with Marmot Creek.The right bank area at the Stilling Basin is the site of erosion that is the primary concern of this study. The Stilling Basin originally constructed in Reach II has experienced deposition of alluvial materials since the diversion went into operation and a small channel along the base of the right bank has existed from the time of construction.Construction phase photographs indicate the 1238 Ml Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 4 Stilling Basin was constructed to be a wide channel section with a 5 on 1 transverse bottom slope to the thalweg of the Diversion Channel and with a zero longitudinal slope;this can be seen in the 8/09/90 construction progress photograph in Figure 5 and typical channel cross-sections shown in Figure 3. FIELD INVESTIGATIONS Field investigations were initiated in September 2002 immediately after the FERC inspection and continued through to early November 2003;field visits were made specifically on 9/03/02, 11/07/02,7/20/03 and 8/29/03.As indicated previously,the field investigations comprised a review of construction records,primarily progress photographs,in the files located at the Bradley Lake Hydroelectric Project powerhouse and on-site observations of the Middle Fork Diversion at low,medium and higher flows.No observations were made at maximum flow.To determine the elevation of bedrock relative to the bottom of the diversion channel and the water level during higher flows and to aid in the assessment of erodability and stability of the right bank and right channel bottom of the diversion channel in the area of the Stilling Basin,a seismic refraction investigation was performed by Northland Geophysical,PLLC,(NG)on July 20,2003.The seismic refraction investigation report provided by NG is included in Appendix B. Observations on-site found that the glacial till has a large fraction of cobbles with boulders in the area of the erosion and that material transported from the Drop Structure area includes cobble and boulders. The net effect of the channel horizontal geometry is that the lower flows in the diversion channel stay within the original channel but at higher flows the diversion channel banks erode,particularly the right bank area in the vicinity of the Stilling Basin where a high water channel has developed along the toe of the right bank.Significant bank erosion is also occurring along the right bank in the channel immediately downstream from the Drop Structure. Review of the construction records including drawings,reports and photographs was performed on September 3,2002 and followed up on November 7,2002.A series of archival photographs were located at the Bradley Lake Powerhouse that documented the construction methods and details of the Diversion Channel construction.Relevant photographs,dated 8/9/90,from the time of completion of the Diversion Channel construction were copied digitally and are presented in Appendix A along with photographs taken during the 2002-03 field inspections. Record drawings included as exhibits in the official project record were reviewed.No drawings were found of changes in the diversion channel since original construction was completed and the record drawings are assumed to represent the Middle Fork Diversion "as-constructed”.Sections of the record drawings were scanned and used in preparing Figures 1 through 3. The seismic refraction investigation along the right bank in the area of the Stilling Basin utilized two seismic lines run parallel to the axis of the Waste Fill Area #2 embankment.The first seismic line (SR-2)was run along the terrace (top of bank)at the right bank of the Diversion Channel near the toe of the Waste Fill Area #2 embankment.The second seismic line (SR-3)was run parallel to the first approximately 75 feet to the West along the top of the Waste Fill Area #2 embankment and 6 feet West of the East top edge of the Waste Fill Area #2 embankment (see Figure 2).The SMI Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 5 full seismic refraction investigation report is included as Appendix B and the seismic lines are shown on Figure 2. Observations of flow in the channel during field visits were subjective and noted only as lower, mid-range or higher flows depending on width of the wetted cross-section and stage of the flow. No stream flow measurements were made with current meter or other instruments to accurately estimate the actual flow rate in the channel at the time of the field visits. DISCUSSION As previously noted,investigation of erosion in the Diversion Channel was primarily along Reach II.Examination of the Diversion Channel bed materials along the Right Bank Erosion Area and the Stilling Basin determined that the bed materials are coarse-grained materials,cobbles and boulders,with void spaces in-filled with silt-sand-gravel materials.The channel bottom material gradation is that typically found in moderately steep,Class G natural stream channels in mountainous terrain and the excavated channel would be characterized as an entrenched gully if it were a natural channel,see photographs in Appendix A. Alluvial materials are transported along the Diversion Channel at various rates depending on flows and deposition occurs in the Stilling Basin area.The function of the Stilling Basin at the downstream end of Reach II is to reduce channel velocity and allow head to build up to drive higher flows through the Bedrock Control in the channel at the downstream end of Reach III.This slowing of flow through the Stilling Basin area allows materials being transported from upstream at the higher flows to deposit at the widened channel approaching the Stilling Basin and this forms an alluvial bar along the right side of the main channel.Also at the moderate to high flows,a small portion of the flow passes to the right of the bar in a high water channel formed in coarse grained glacial till materials along the base of the right bank,See Appendix A2 photographs 3,4, 6,8,and 9.This bar of alluvial materials presently exists along the length of the Stilling Basin area (See Appendix A photographs).The deposited material in the bar erodes and is transported on downstream at very high flows.Also,at very high flows the channel water level is high enough to erode the organic/mineral soil overburden materials forming the terrace along the right bank.The erosion is most severe in the direction of flow as the water impinges directly on the channel bank (terrace)below the rock knob at the right bank at the downstream end of the Stilling Basin.Bedrock is becoming exposed near the Diversion Channel in this area and will ultimately stop the advance of erosion,see Appendix A4 photograph 2,7,8,9,10,and 11.The flow path is along the right bank to the left,past the recently exposed bedrock and into the Diversion Channel downstream from the Stilling Basin.The Bedrock Control feature at the downstream end of Reach III effectively acts as a hydraulic control at higher flows and promotes the deposition of bed load in the Stilling Basin area due to backwater effects at higher to very high flows,see Appendix Al photograph 7 and A4 photograph 12. Figure 4 shows two annotated photographs of the area at the Stilling Basin,one photograph was taken 8/09/90 at completion of construction of the Diversion Channel and the second photograph was taken some 13 years later on 7/20/03.As can be seen by comparing the two photographs,the Stilling Basin feature of the Diversion Channel has accreted sand,gravel,cobbles and boulders from upstream channel erosion along the right side of the low water channel that are transported by higher flows.However,the Stilling Basin appears to have maintained the general 2S) Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 6 configuration to which it was constructed 13 years ago though the high water channel visible along the right bank in the more recent photograph is more pronounced. Figure 5 shows two annotated photographs of the steeply sloping channel section upstream from the Stilling Basin.One photograph was taken 8/09/90 at completion of construction of the Diversion Channel and the second photograph was taken some 13 years later on 7/20/03.As can be seen by comparing the two photographs that the steeply sloping section of Diversion Channel has degraded and eroded progressively upstream to a point approximately 250 feet upstream from the Stilling Basin.This formed a steep chute that is essentially a Drop Structure formed in a rock excavation section of the diversion channel where the channel passes between two rock knobs. The erosion of the formerly steeply sloping section of channel in Reach II also resulted in significant erosion of the channel side slopes as the channel bottom degraded.The extent of the bank erosion can be seen in both Figure 5 (Photo dated 11/07/02)and Appendix A3 photos 2 and 3 and Appendix A4 photos 3 and 8.This erosion along the right bank from about 100 feet to 200 feet upstream from the Stilling Basin could become a concern as the Diversion Channel widens. However it is thought the erosion will reach the underlying bedrock in the near future and stop.If this is not the case,remedial measures such as installation of gabion groynes or "J”hook training structures may be required to train the flow back into the intended channel. The channel degradation in the area below the Drop Structure is the probable source of some of much of the finer materials and most of the cobble and boulder materials deposited along the right bank in the area of the Stilling Basin,see Appendix A2 photographs 1,2 and 10.This can be verified through continued inspection. Additional photographs of historical and present physical conditions in the Middle Fork Diversion Channel are included for information in Appendix A as Sub-Appendix A1 thru Sub-Appendix A4. Figure 6 is an annotated image of Figure 7 from the NG Seismic Refraction Investigation included in Appendix B.Figure 6 shows the location of the top of the glacial till and bedrock profile and the estimated bottom of the high water channel along the right bank at the erosion area adjacent to the Stilling Basin area.Indications are that bedrock is up to 30 feet below the channel bottom at the right bank adjacent to the stilling basin and that the bedrock is overlain by glacial till at least up to the bottom of the channel with organic and mineral soil over the glacial till. Figure 7 is an annotated image of Figure 9 of the NG Seismic Refraction Investigation included in Appendix B and shows the bedrock profile under the Waste Fill Area #2 embankment and the estimated bottom of the high water channel along the right bank at the erosion area adjacent to the Stilling Basin area.The shot-rock armor and undifferentiated core material in the embankment forming Waste Fill Area #2 registered on the seismograph as a single material type in the seismic refraction investigation.We interpret this to indicate the undifferentiated material in the embankment has a medium percentage of waste shot rock and that any soil layer over the underlying glacial till was thin and was intermixed with the undifferentiated waste in the fill during embankment construction as it does not appear as a defined layer of material in the seismic velocity-depth section of Figure 7 (NG's Figure 9).Note that the depth to bedrock on Figure 7 is likely not as accurate as that shown by Figure 6 for reasons stated in the NG report. Also,note in both photographs that a boulder that was in place in 1990 on the right bank terrace remains in the same location in 2003 which shows graphically that the lateral erosion of the -3SM1 Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 7 Diversion Channel bank at that location is nominal rather than extensive at the right side of the Stilling Basin.This boulder is also visible in photographs in Appendix A,particularly Al-1,A2-3, 4,5 &6,A3-2,3,4,5 &6,and A4-7and 8.The major erosion occurs at the sharp left bend in the right bank which is underlain by bedrock at the base of the rock knob at the South end of Waste Fill Area #2 and the Stilling Basin area. Comparing the two photographs in Figure 4 also shows that the present erosion along the right bank adjacent to Waste Fill Area #2 would be expected due to the design of the Diversion Channel and Stilling Basin as flow is directed across the Stilling Basin directly into the right bank area where the bank curves to the left.See also Appendix A photographs A3-6 and A4-8. CONCLUSIONS Erosion of the Diversion Channel Reach II Right Bank in the area along the Stilling Basin will continue but is essentially self-limiting at the location of the Stilling Basin due to the coarse glacial till and shallow bedrock.Erosion of the right bank along and immediately upstream from the Stilling Basin will be stopped by shot rock from the Waste Area Fill #2 embankment armoring the erosion area should the erosion progress into the toe of the embankment slope.If no remedial corrective measures are taken the probability that the erosion along the right bank of the Diversion Channel will actually extend through the base of the Waste Area Fill #2 is very low considering that the fill has a base width on the order of 100 feet and is over 25 feet high. Erosion of the Diversion Channel Reach II and III Right Bank in the area at the downstream end of the Stilling Basin where the right bank curves sharply to the left will continue for some time but is self-limiting as the bank is underlain by bedrock (now partially exposed)that extends above the high water level.There is no immediate need to provide corrective works along the left-curving right bank erosion area at the downstream end of the Stilling Basin. Erosion of the Diversion Channel Reach II Right Bank in the area between the upstream end of the Stilling Basin and immediately downstream from the Drop Structure will continue until it either reaches the underlying bedrock in the right bank or reaches a state of natural equilibrium as the channel width increases.If a state of natural equilibrium is not reached,it is possible that erosion incursion will need to be limited at a future date by installation of corrective works using insitu materials such as gabion groynes or "J”hook training structures or by moving boulders in the channel to the right side of the channel to form natural flow training works.To allow expedient implementation of erosion remediation measures,an action plan with easily executed erosion remediation concepts should be prepared and placed on file at the project.Since access to the site is mainly by helicopter,materials and equipment must be helicopter transportable. It would not be expected that any significant future down-cutting or degrading of Reach II of the Diversion Channel will occur (such as occurred in the past that formed the Drop Structure)but it is probable the Drop Structure will continue to erode and move upstream somewhat over time.The channel bottom elevation and slope along the right bank of the Stilling Basin area should remain as at present as hydraulic control of the channel in this area is established effectively by the Reach III channel and the Bedrock Control terminating Reach III.However,lateral erosion of banks will continue until an equilibrium is reached or eventual remedial measures are taken as warranted. SSN71a Bradley Lake Hydroelectric Project,Middle Fork Diversion Erosion Study 8 RECOMMENDATIONS Based on the conclusions reached in the present study of the Middle Fork Diversion Channel erosion as noted above,we recommend the following: 1 -Do not perform any remedial work to correct erosion conditions along the right bank of Reaches II and III of the Middle Fork Diversion at this time. 2-Establish a data form and reporting format for use in ongoing inspections of the Middle Fork Diversion that is structured to focus on the various features of the Diversion including the Intake Basin,Reach I,Drop Structure,Reach Il,Stilling Basin,Reach III,Bedrock Control feature,and Reach IV and allow consistent data presentation for evaluation.Update project procedures as required to include the structured data collection. 3-Continue the established program of monitoring all Reaches of the Middle Fork Diversion on. a regularly scheduled basis but including taking digital photographs and logging the condition and any changes in the various features of the Diversion Channel.Note the occurrence and extent of any erosion areas,slides,channel degradation and other areas of concern to establish a database for evaluating channel performance and maintenance needs. 4-Re-evaluate,from year to year,the stability and the performance of all features of the Middle Fork Diversion based on inspection findings.If required,take appropriate action and perform remedial corrective work to the affected Diversion Channel feature(s). 5 -For the near future,perform more frequent (once per month June thru October)monitoring of right bank erosion along Reaches II and III of the Middle Fork Diversion in accordance with project inspection procedures.This includes taking digital photographs of the right bank erosion areas,East toe of Waste Fill Area #2 and any other areas of concern along Reaches II and III during each inspection.Note the occurrence and extent of any erosion areas,slides, channel degradation and other areas of concern.Maintain the inspection records and photographic database for evaluation of channel performance.Report inspection results within 10 days of the field inspection.Revaluate the need for detailed inspections of Reach IV/III in 2007 and continue if warranted.If continuation of detailed inspections is not warranted,implement Recommendation 3 for Reach II/III. 6-Re-evaluate the results of the detailed monitoring of Right Bank Erosion of the Middle Fork Diversion Channel in Reaches I and III as inspections are made per Recommendation 5,and, if the erosion advances to an unacceptable level along any portion of the right bank of Reach II or II,take appropriate action and perform corrective work as required. 7 -Prepare a remedial action plan for use in possible future corrective work along the right bank of Reaches II and III of the Middle Fork Diversion Channel.Base erosion control concepts on helicopter transport of materials and equipment an on using site-available materials in gabion baskets formed into groynes and/or "J”hook structures or to form boulder training sills along the channel.- 2S BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY FIGURES Figures 1 through 7 13M INTAKE BASIN : ONS JooKENALésfp&PENINSULA A OPEN CHANNEL TO MIODLE FORK TRIBUTARY waneTA FILL \\-srittins BASINAOPENCHANNEL cTOMAAecree(EXISTING DRONNAGE »)VICINITY MAP fy AREA MAP AT DIVERSIONScale\NTS SSCy,Lt cAMesiTi\{STA S75+00pPSITE "2ifforkcen FLAT reese?TENDING STRIP ake {'4 a"S2\sity SSROAD LOCATION MAP OQ =an y aPONDScaneOYS,(sta 873)oY{RECLAIMED RIPRAP.iy)&)Qs}anes BRADLE 6 a0 -aed "e Rea PS <D &S main BattGowesreRS NTN NORMAL MAX.WS.EL87 NORMAL MAK.W.S.ELTISO = ,:'A 887 )S {od.oe ans oS caMesiTE 4 e009 peer oa 7 PO%(STA 815)CREEK Oy VA >.4,ELEVATIONS SHOWN ARE BASED ONFPeGEAIFELINELEVELDATUM»PROJECTZzSATUMPLUS4.02 FT, oy : =( )°wos 00 sood Aooke etaees!Dovtane nt and Lepoet Authur: a co :..Alatka Energy Autsonty -a BRADLEY LAKE HYDROELECTRIC PROJECT PROTECT MAR ee LOCATION MAP,VICINITY MAP,Scale:Graphic ''ars Vie PROJECT MAP AND AREA MAP EROSION STUDY -FIGURE 1December31,2003Ref.Bradley Lake HEP drawings H05-F-08-0001-R49,HO5-F-04-2002-R49,HO5-F-04-2012-R49,HO5-F-04-2013-R49 Stilling Basin;Now Filled |CoWithGravel,Cobbles and \7 Cc/,MG; Estimated Location of Boulders SNANN\ Drop Structure formed by Erosion of Steep Channel SSo& LOR,AW: ie x SSERIEENNYDe"Gs ZN \"4 (3 We :|Wy ow X26Hi,(x.y h Geophone 1 location on each line3[2 -\s 4ieee SSE.,( whl s a ye .a)\-*, Z-: .Mm LONG Nr |Ss "i \)ax Svs Waste Fill Area #24a yaya (WEY Seismic Refraction Investigation Line 3 Potential Channel to Bradley 72.\y iAPf1 AC |S ---Yo River Tributary Area Seismic Refraction Investigation Line 2 cn | 4WAGPLAN-AS-CONSTRUCTED Scale:Graphic nel "ate N\\\0 feet 100 200 Low to Medium "Ny Flow Channel High Water Channel and 3 Eroded Right Bank AIDEA /IAF A BRADLEY LAKE HYDROELECTRIC PROJECT BRADLEY RIVER MIDDLE FORK DIVERSION DIVERSION CHANNEL PLAN EROSION STUDY -FIGURE 2 Waste Fill Area #1 . SPs VEaaR&M CONSULTANTS,INC. December 31,2003RefBradleyLakeHEPdrawingsHOS-F-04-2012-R49,HO5S-F-04-2013-R49 of Diversion Channel Intake Basin and upper section of Reach I Drop Structure formed by Erosion of Steep Channel Drop Structure,Reach II,Stilling Basin and Right Bank Erosion Area Lower section of Reach I &Head of Drop Structure Middle Fork Diversion Intake Basin ?"eee fe266© Y,yy/LO gh \\TESWas¢SYyy)My I4 Bedrock Control feature |es 'aeERSTENSeeepeege¥Pag « yy Reach I,Stilling Basin,Reach IIT and Right Bank Erosion Area Reach II,Stilling Basin,Right Bank Erosion Area and Head of Reach III Reach I If and III looking Downstream Marmot Falls at Bradley Lake Reservoir AIDEA/AEA |Alaska Energy Aulionty PLAN -AS-CONSTRUCTED Scale:Graphic SS_0 feet 100 200 Ref Bradley Lake HEP drawings HO5-F-04-2012-R49,HO5-F-04-2013-R49 SSeS ViaR&EM CONSULTANTS,INC. December 31,2003 BRADLEY LAKE HYDROELECTRIC PROJECT BRADLEY RIVER MIDDLE FORK DIVERSION DIVERSION CHANNEL PLAN EROSION STUDY -FIGURE 2A NOTE -Reaches I through IV are as defined Intersection with (NTS? "LOOKING UPSTREAM by Channel Features in 2002-2003 Marmot Creek Original Channel with Slope of 147%Stilling Basin and Estimated Location of existing "Drop Approximate Area Intake Basin Structure”formed by Erosion of Steep Estimated Existing of Right Bank (14%slope)Channel Channel with Slope Erosion Bedrock Control la XN >)\of about 2% | . n0 4 INTAKE oasn Reach I |i. IMIDOLE FORK -a) iced Te an Reach II >Reach III sie skS2100]cac eac Reach IV bs <4 27 :. = &oto J ° --s 2%SLOPE ----Pf fp smane ees -,::V .m0 i uy .&,i ae gan 7 , ;z 7604!" me s|: .cL aT ====E224 2%SP mm a suo2120=_--$200002003-00 .400 5400 6-00 7400 6-00 9-00 . ,"S 2120-44|"STATION :2 'Ww Ln a PROFILE re 10-00 too .> PROFILE -AS-CONSTRUCTED t ;|cee seo is 2 Scale:Graphic 5 €PROFILE P t :"PLL WIDTH wares,o «4 8OFEET,L__FRLWIDTHvaRies, "OVERBURDEN 12 .= MIN 6 Laon el oo0m CHANNEL STS BEOOMIN 7 on y WASTE FILL SS S25 hin ::TYPICAL al |crn EXsTTYPICALCHANNELEXCAVATION CHANNEL EXCAVATION IN OVERBURDEN 3-3 - IN ROCK &OVERBURDEN ;Lookin erean , WASTE FILL . . .: ; AREA 2 TYPICAL CROSS-SECTIONS -AS-CONSTRUCTED Scale:Graphic BRADLEY LAKE HYDROELECTRIC PROJECT ES s.MEEZa2 BRADLEY RIVER MIDDLE FORK DIVERSION R&M CONSULTANTS,ING.CHANNEL PROFILE AND TYPICAL SECIONS EROSION STUDY -FIGURE 3December31,2003RefBradleyLakeHEPdrawingsH05-F-04-2012-R49,HOS-F-04-2013-R49 Bradley Lake Hydroelectric Project -Middle Fork Diversion -Erosion Development _Page 1 of 1 Eroded Channel Bank Waste Fill Area #2 Approximate Location of Original ak Developing HighStillingBasinoeWaterChannel Boulder;Reference and TBM NOTE:Flow in channel is at higher end of flow range. As Viewed From Lower Drop Structure Looking Downstream Photo taken 7/20/03 Stilling Basin as constructed in 1990 Boulder;Reference and TBM East Slope of Waste Fill Area #2 NOTE: middle Flow in channel is at to lower end of flow ox MS x"x OgaeTE EEa reritAOeatSheeodvat oe Beat eeepoaetedYtyeetMatteaeeh Poet.3 der Pie ey As-Constructed Middle Fork Channel Erosion Area As Viewed from Lower Drop Structure Looking Downstream Photo Taken 8/09/90 AIDEA/AEA... fm =&.MV aREMCONSULTANTS,INC. FIGURE 4 -PHOTOGRAPHS OF ORIGINAL AND EXISTING CONDITIONS STILLING BASIN /RIGHT BANK EROSION AREA Bradley Lake Hydroelectric Project -Middle Fork Diversion-Channel Erosion Page 1 of 1 Drop Structure formed by channel erosion Area of steep channel erosion Stilling Basin location ey SPS ae naPedainSPER be ve "Whe vey 'wsMeteevehs,BeeeweedsCae ee iaMa Ai!SS.Current Conditions Middle Fork Diversion Steep Channel:Drop Structure Area As Viewed From Right Bank Looking Upstream Photo taken 11/07/02 Location of Drop |Structure formation Steep channel (14%slope) Stilling Basin location As-Constructed Middle Fork Diversion Steep Channel-Drop Structure Area As Viewed From Right Bank Looking Upstream Photo taken 8/09/90 me =&.V1REMCONSULTANTS,INC. FIGURE 5 -PHOTOGRAPHS OF ORIGINAL AND EXISTING CONDITIONS STEEP CHANNEL /DROP STRUCTURE AREA Ome Approximate area of greatest erosion activity in diversion Approximate location of thalweg of potential channel to Bradley River Tributary Area channel 2 a | F SOUTH NORTH 4 Approximate @ 120 E 4120 |bottom of £Ground Surface hi ghwater ©110 F .channel at right=E Shotpoint Location =bank of 5 100 F wt OY '400 |diversion >2 ee }Aan :channel Sercodedee cerns a tale Eee OOQpatsaieeeeyy, Go fF Keiss BF ty tay oy EEE ET ES ISIS ROS 3OEROKR2ae0dtisee”O27 LOTOTT RRS 80@£&oS OL ey Oy PET GLRRR |B70 F OCR ORR:=LO!FO:102 GO:ARK KK,|70BBROSSERETETEETEEOTEKKKKKKKROOEEETPIGORKKRRS,|EID Beotetatetccotenstetaretetarenc tet ae aretaterateratetacetetente La3seccatsanstatetacetacetacesarteicenecenBedrockSKSKS,|BE IIIITHTT ees IT,en:peetatacanstscanenetecenete eeeatatatatetetanatonaenenetaen SxS |go HeeLeeerrri rite te gg 0 50 100 150 200 Distance from First Geophone (feet) FIGURE 7 HORIZONTAL SCALE IN FEET Seismic Line SR-2 Prepared by:ey =(BCE Shells Energy Source)NORTHLAND GEOPHYSICAL,ettc VERTICAL EXAGGERATION:2701 Velocity-Depth Section R &M CONSULTANTS,INC.Middle Fork Diversion Channel NOTE:This Figure is based on Figure 7 of the Seismic Refraction Survey Report.See Appendix B for that Report MIDDLE FORK BRADLEY RIVER DIVERSION CHANNEL EROSION STUDY SEISMIC REFRACTION PROFILE SR-2 FIGURE 6 Approximate area of greatest Approximate location of thalweg of potential erosion activity in diversion channel to Bradley River Tributary Area channel idl 2 Os TTT TTT TT TTT TTT TTT TPT tr 140 F SOUTH Geophone Positijns Shotpoint Lagation Ground Surface NORTH 8 130 &130 Approximateéa45hectorbestesorterraacreTUTIsti-,-P oi battom ofx12035mies:Sacaa sete Sasa ter emu?SM RATA3 Saeaaseessas 420 highwater€Ep O41 ae iy .=aes a channel at righto7¢,of .5 1410 £-S mr ¥A 10 tilec,Se 110 bankorc:E NEATEF '6%' 5 100 E x ans Ageei BEEK KKK NOD 400 |channelef3%3 PER ORR GROSSO§£2 Nig nitasitghisaereisentees Ait COO OOOO,OOOOOOaE eeFaoEaseCpkwphaveleaeigeyes:OCCoEYSEEROMEVOCCCCCOCCOCUCOCCOO 90BEKQQQRSSADOSERQOCOQPOOHZBRRRRRRRKOFREKKKORRECKLBagBQOQQQQRQRQRQRVRSSOEVOOCCCCCCOCO,BBO KOSI BOO "Fh 80DFQQQQQQVEQLQPQQLCO$125726735:OOOO,QDR PD 70 BE RODGERS aPPIOX.11,300 fl'SeC XOXOXO 70BESRRRKRRKERRKKKKEIOKKKBFQQQQQQVQQLOQO#GPI DODO OPO OOOO OOKPeOO00OWCOCCCOCWCUCUCLOOOOOWCCCDCUCDCCWOOOO,B60 E SOKO R HOHIRRKK J 60eres EF OO OD50 0 50 100 150 200 Distance from First Geophone (feet) HORIZONTAL SCALE IN FEET Prapared by: NORTHLAND GEOPHYSICAL,eitc Prepared for. R &M CONSULTANTS,INC. 0 10 a w 40 VERTICAL EXAGGERATION:2TO1 +50 250 300 FIGURE 9 Seismic Line SR-3 Velocity-Depth Section Middle Fork Waste Fill Area No.2 NOTE:This Figure is based on Figure 9 of the Seismic Refraction Survey Report.See Appendix B for that Report MIDDLE FORK BRADLEY RIVER DIVERSION CHANNEL EROSION STUDY SEISMIC REFRACTION PROFILE SR-3 FIGURE 7 BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY APPENDIX A Sub-Appendicies Al thru A4 Historical Photographs of Middle Fork Diversion [36S Bradley River Middle Fork Diversion -Construction Progress Photographs of Stilling Basin and Diversion Channel in Area of Erosion At Waste Fill Area #2 Page 1 of 3 « ene anne wg we, PMS tn feeaee oe ee aeeK"ATR TeSceneola 1 -Looking Upstream over Stilling Basin toward 14%slope Channel (channel eroded bedrock control since this photo was taken and steep channel is now a drop structure). Bohm eo aewteddL »i ' 2 -View from top of WasteFill. back to APPENDIX A1 -HISTORICAL PHOTOGRAPHS dated 8/09/90 ae 2 >.11REMCONSULTANTS,INC.AIDEA/AE eM oiateienn Bradley River Middle Fork Diversion -Construction Progress Photographs of Stilling Basin and Diversion Channel in Area of Erosion At Waste Fill Area #2 Page 2 of 3 Same aePo aez ra aewe 4 -Looking upstream at channel contraction Bedrock Control feature. APPENDIX A1 -HISTORICAL PHOTOGRAPHS dated 8/09/90ee2ES.V1 AIDEA/AEAREMCONSULTANTS,INC. Bradley River Middle Fork Diversion -Construction Progress Photographs of Stilling Basin and Diversion Channel in Area of Erosion At Waste Fill Area #2 Page 3 of 3 ee EAS 4%eeteiin aos cers oking upstream at Middle eeemStation5+00 toward immediately after commissioning on 8/07/90. APPENDIX A1 -HISTORICAL PHOTOGRAPHS dated 8/09/90me2SVAIDEA/AEREMCONSULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 1 of 5 gy Fawr laos 4 : Se me t:oe : ..P.gt be Py a } = 2"thecn * tat oa an.pies J*la,ae 7c .-4 rr get ae | .on TL L +Soak,MR ee ;POLES RCie OO a Se We Rae ee tatescturecreatedbyerosionofasteepunlinedchannellooking upstream from Right Bank of Diversion Channel. =Wi ula Mh ne ytcnceen_?the"ae if >aa we at eesmeeetareg”,a Wars32.. wee i ™ae ve t eT a eee . 2 -Looking downstream along right bank toward APPENDIX A2 -HISTORICAL PHOTOGRAPHS dated 9/03/02 oe 2S.V1 AIDEA/AEA.x.R&M CONBULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 2 of 5 PRayer:a * E. >Fa tasquraeeeast.idaihad¥'4i'yetaah,rheigaMd,Toe e"ee Pegecan ae32TokeeenaloneNehbankoveraSiillingBasin area toward Drop Structure.:?AA 8 eerayrrY™g ey sPATAFe"he1HUTaiFrneoperawrenThorny:1,,4'be-abam:4 ore - _ -4 ea Lm _ 7 «la ae .}ar »a ' --_set i oy -an ==;jer _oF .we . a "ae ap - rm . -ran a ee Cee : -.!oe x=a oo itePSgadtarétbicab'ai e et :"Tooking |upstream along right bank at bank erosion near toe of Waste Fill Area #2. APPENDIX A2 --HISTORICAL PHOTOGRAPHS dated 9/03/02poeF211AIDEA/AEA.REM CONBULTANTS,ING. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 3 of 5 cee ee ee eee Tar 0 aR,SE TM SEE OES AQ Bos 7 .- *oe i - e :at _>- 7 &:-ny .we hye ES.oa fee ayee_a erfi-aa =«7 7 oFhe"2 =e ak -. .4 e =-*>-=*k om,_be -oL.3 .ae -d .-ae -ad oe;Cae _«jrf=:ee eee + i .+7 gy a ere _5 7 i .-ae r *'he,"en .7 _.I a j i .4 -3 oat af '1 7 -:a v .it are .=+.3 =7. =e ae ind JJ«-.é d ,» }aime fi-_ z wee ae ' =:'eea?."ato .4 nd 46 an ve i oe moe \.a 7!'oe!y *.at 7 -_- wt 'sy "|.an ar }@-.*% .4 :wwf t os .a :'. 2 |'a 23 :' é rEg ._#3wet 2 it ' -'.ae '+f we ey fakeanwyte!!oe qsauteParkaMsrlacBbsteadihrer5-Aerial view of Stilling Basin ans;Erosion Area from above left bank of Diversion Channel looking upstream.--ry:yee art:weNeeder -vost ac)a»aLa2'aan . "4 & ae a . .-.ve a rr rn)act . :_-.4 . .3 :'q q °. 4 5 ,' %4 . x .won "ye - - * - 3 aay ";faery ”te «*eer "4044 .4eeemeNEPORTOemeeaeeeePeSPTarseinaa6-Aerial view of Stilling Basin and Erosion Area from above left bank of Diversion Channel looking toward Waste Fill Area #2. APPENDIX A2 --HISTORICAL PHOTOGRAPHS dated 9/03/02ae2SVAIDEA/AEA.Ram CONBULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 4 of 5 wlLAthebhaaeeeevy8 -Cobbles and boulders onbar at right bank «erosion area,field book iiSoros APPENDIX A2 -HISTORICAL PHOTOGRAPHS dated 9/03/02poetF211AIDEA/AEA.REM CONSULTANTS,ING. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 5 of 5 ee eee >.. 407 i Pal Pats TT i :. -woo'sy ied EG?es10-Boulders eroded from left bank downstream from Drop Structure. APPENDIX A2 -HISTORICAL PHOTOGRAPHS dated 9/03/02pone2ViAIDEA/AEA.R&M CONSULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 1 of 4 eeoe'Gan\s eo vee crs le . _ FE Roe mei he awh ee i ee =at we ---1 -View of Drop Structure created by erosion of a steep unlined channel looking upstream from Right Bank of Diversion Channel. ;z ;b. - S ".Fa7 'q 3 f -ot jPrepvdsae,asec ee ayPosetitind APPENDIX A3 -HISTORICAL PHOTOGRAPHS dated 11/07/02mes2SVAIDEA/AEA.__...REM CONSULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 2 of 4 "a.aAeateeoe&Sod 7is.°.ae Steg..ay¥apahemuae&aNisse}SaBSaw'-Vb age Biweece 2c Vata ilaEAN 'if:[SenokingupstreamalongrightbankoverStillingBasinareatowardDropStructure. et :a ee rt 4oa A as elmi nae AN +4 -Looking upstream from right bank aat beginning of diversion channel bank erosion near upstream end of Stilling Basin,note developing high water channel along right bank. APPENDIX A3 -HISTORICAL PHOTOGRAPHS dated 11/07/02mn2SVieAIDEA/AEA.R&aM CONSULTANTS,ING. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 3 of 4 io ee "i.y .' strutsTOEeWeTe 6 -Aerial view of Stilling Basin and Erosion Area from looking upstream toward Waste Fill Area #2,Bedrock Control at left foreground,Drop Structure at right background. APPENDIX A3 -HISTORICAL PHOTOGRAPHS dated 11/07/02paF=2 V1 AIDEA/AEA.REM CONSULTANTS,INC. Bradley River Hydroelectric Project -Middle Fork Diversion Existing Conditions at Lower Flows Page 4 of 4 °. .a -ey.are * pote TU : -.*.1 :'°- e atten Loe ange os te wt =.oe Ue _oe .ne OSS 2aat SS ze?oe Maite -.MOD aoe a?co '.ere aes =bd ant ss waced ht ™| .i .ie eee ee es a ee -.|Tet Yoesoegeln SO?.F?QIne and-ST me ee 7 ees Ft ght Lite wie ONDooeenOLee-'== -es fe =*ng Tet we ee Ot ee t-=o:«6 -°Pa ©--.-oT ow ee 8wa=7F a .a ete DO * -=wn uu -"@eeeeeOSeeSe"to . a ee7-Bedrock Control in Diversion Channel at head of Reach IV (image scanned from video tape). 8 -Middle Fork Diversion Intake Basin (image scanned from video tape). APPENDIX A3 --HISTORICAL PHOTOGRAPHS dated 11/07/02 ee 2 SV AIDEA/AEA.-.x.REM CONSULTANTS,INC. Bradley Lake Hydroelectric Project -Middle Fork Diversion Existing Conditio Page 1 of 6 ad tataaeaeaaeee"aiaellesai1 -Looking up om channel erosion since construction;located at approximately Station 6+90. Original Stilling Concern -Basin Area Erosion Area of ae Bierstream along right bank toward Stingdowns APPENDIX A4 -HISTORICAL PHOTOGRAPHS dated 8/29/03ees2S.V1 AIDEA/AEA.RGM CONSULTANTS,INC. Bradley Lake Hydroelectric Project -Middle Fork Diversion Existing Conditions at Higher Flow __Page 2 of 6 Te tine aikenae a .aeentbank0overStillingBasinarea towtowardBr-3 -Looking u stre:ream1 alongoes)a FoARE,1 i34-Looking upstream along right bank at bank erosion;this viewis immediately tothe left of Photo 3 above. APPENDIX A4 -HISTORICAL PHOTOGRAPHS dated 8/29/03meF=2 V1 AIDEA/AEARMCONSULTANTS,ING.Penna Bradley Lake Hydroelectric Project -Middle Fork Diversion Existing Conditions at Higher Flow __,Page 3 of 6aoSSana Vo.apefTY6 -Aerial view of Drop Structure and area iawedintehy downstream. APPENDIX A4 -HISTORICAL PHOTOGRAPHS dated 8/29/03 oe 2 >.1/1 AIDEA/AEA.REM CONSULTANTS,INC. Bradley Lake Hydroelectric Project -Middle Fork Diversion page 4 of 6 Ewan a ue wy oa peStillingBasinandbankerosionasviewedfrom Bedrock Control (channel contraction) EY Drop "<4 Stilli in EEO Sa LAMY ight Bank (4 Structure f°ee oe er 7 |Erosion Area '2 JehanCoesrypee8 Aerial \view looking downstream over Drop Structure toward Stilling Basin,right bank eroded area and Bedrock Control. APPENDIX A4 -HISTORICAL PHOTOGRAPHS dated 8/29/03 aS Vie AIDEA/AEA meek Bradley Lake Hydroelectric Project -Middle Fork Diversion Existing Conditions ___Page 5 of 6 i ay AF t4rsLeTaGaels25 ,«hare4a at AG ae p24 r,s.:terthyJ7TM °af '_4 --°=on "4 -a7 an te a .a eeees To3 yeea7.-=oShe -. .-_-__-a)oe,.- ---aa . ™..:x er .n,nate ort . ws pee f bi aah et .ae ee "4.A ."' 10 -Right bank erosion area at downstream end of left-curving section of bank (image scanned from video tape). APPENDIX A4 --HISTORICAL PHOTOGRAPHS dated 8/29/03neF=2 E>,1/1 AIDEA/AEA.... Bradley Lake Hydroelectric Project -Middle Fork Diversion Existing Conditions at Higher Flow Page 6 of 6 purwerwe Ne - tw Stas a wy i ¢ omAleAhena =as 11 -Right bank erosion area in left-curving section of bank (image scanned from video tape). =.ee ty eae a ena,-eet Ly lee te athe etal?Ratan12-Bedrock Control at contraction in Diversion Channel at head of Reach IV (image scanned from video tape). APPENDIX A4 -HISTORICAL PHOTOGRAPHS dated 8/29/03 meee 2 SV AIDEA /JAEA a teFamCONSULTANTS,INC. BRADLEY LAKE HYDROELECTRIC PROJECT FERC Project No.AK-8221 BRADLEY RIVER MIDDLE FORK DIVERSION EROSION STUDY APPENDIX B Seismic Refraction Investigation Report JIS M1 NORTHLAND PO Box 310 ©Snohomish,WA 98291-031 GEOPHYSICAL,pitc 425.347.4559 phone ©425.513.0835 fa Geotechnical &Environmental Geophysics December 11,2003 Mr.John K.Magee,P.E. R&M CONSULTANTS,INC. 9101 Vanguard Drive Anchorage,Alaska 99507 SUBJECT:Results of Seismic Refraction Investigation Bradley Lake Hydroelectric Project Kenai Peninsula,Alaska Dear Mr.Magee: This report presents the results of a seismic refraction investigation conducted by Northland Geophysical,PLLC,and R&M Consultants,Inc.,from July 22-23,2003,at the Bradley Lake Hydroelectric Project,located approximately 25 miles northeast of Homer,Alaska.Seismic refraction profiles were completed in two areas of the hydroelectric development where remedial measures are being considered. Seismic Line SR-1 was surveyed on the upstream face of the bedrock which comprises the Bradley Lake Dam spillway foundation.The purpose of this line was to assist in locating zones of weakness in the bedrock that may be contributing to seepage observed flowing from the spillway foundation drain gallery and on the downstream face of the spillway near the foundation. Seismic Lines SR-2 and SR-3 were conducted adjacent to the Middle Fork of the Bradley River approximately 2.5 miles north of Bradiey Lake in an area where the Middle Fork was diverted from its former natural channel to increase inflow to the Bradley Lake reservoir.Some westward erosion of the diversion channel has recently been observed in this area.The purpose of the two seismic lines was to determine the approximate elevation of the bedrock surface to assist with evaluation of the extent of the erosion problem and possible mitigative measures to be employed in controlling the erosion. The Seismic Refraction Method The principle of the seismic refraction method is illustrated in Figure 1 on the following page.An impulsive energy source at or near the ground surface is used to generate a seismic wave (sound wave)that travels through the earth.When the expanding wavefront reaches a layer of higher velocity (such as bedrock),a portion of the energy is critically refracted and travels along the refractor as a "headwave'”at the velocity of the refractor.Energy from the propagating headwave leaves the refractor at the critical angle of refraction and returns to the surface,where its arrival Results of Seismic Refraction Investigation Page 2 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 is detected by an array of sensors (geophones)and is recorded on a seismograph. As defined by Snell's Law,the angle of refraction depends on the ratio of velocities of the overburden and the bedrock. Seismograph Energy Source Geophone Array Trigger Cable ""..."...YAN Direct Waves Refracted Waves .Soil LS A SD YE RR A CONG RED OR EN NBSSSSSSSSaeeaeCooT,Bedrock 5SSRSRERSSSNSNENOSECRSCUSCENINOSSOSENSRSACONGER(SY QOS GED GOON SOROS SOUR | FIGURE 1.Principle of the Seismic Refraction Method Unless the subsurface interfaces are planar and parallel with the ground surface,it is necessary to record a minimum of two "shotpoints,”one at each end of the seismic "spread”(geophone array).In practice,two additional off-the-end shotpoints are normally recorded,as well as one or more shotpoints within the geophone array. In the data processing phase,travel times for the seismic wavefront to reach each geophone are measured from the seismograph records for all of the shotpoints. Using the matrix of geophone positions and seismic travel times,seismic velocities in each layer and the depths to the layer interfaces are subsequently computed. Field Investigation Seismic Line SR-1 Following transportation of the seismic crew and equipment by light airplane from the Homer airport on the morning of July 22,the Bradley Lake seismic investigation commenced that afternoon with seismic profiling along Line SR-1 just south of the upstream face of the Bradley Lake Dam spillway.Access to the spillway was achieved by vehicle up the gravel road to the dam.The orientation of the seismic line with respect to the spillway is diagrammed in Drawing No.SK-01-8221-76 dated Results of Seismic Refraction Investigation Page 3 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 10/21/03,attached,which was prepared by R&M from project records for this report. The seismic line is located parallel to and immediately upstream from the upstream face of the spillway. The purpose of this seismic line was somewhat different from the typical application of mapping overburden thickness illustrated in Figure 1 above.The objective of this profile was to search for zones of weakness in the bedrock foundation of the spillway that might be contributing to seepage observed in the foundation drain gallery and on the downstream face of the spillway foundation.An array of 23 geophones with a nominal geophone spacing of 3 feet was used for the profile,resulting in a seismic "spread”length of 66 feet.The seismic sensors consisted of a string of 23 Mark Products L-15A 14-Hz vertical geophones.These geophones are mounted in MC- 10 marsh geophone cases with 7-foot leads.Emplacement of the geophones on the exposed bedrock surface of the spillway foundation proved to be more difficult than in normal refraction surveying.Emplacement was accomplished using a hammer and bull point to provide a starting hole for the geophone spikes,and then encasing the vertical geophones in sandy gravel carried from nearby deposits. The seismic energy source for the spillway profile was a 16-lb.sledgehammer and steel striker plate,as illustrated in Figure 1 above.Five shotpoints were sequentially recorded for Line SR-1 at varying positions along the line.All seismic data were recorded on a Geometrics R24 StrataView multichannel digital seismograph.The data were recorded digitally on an internal computer hard drive in the seismograph as well as on paper field records (seismograms)for field verification and data backup. The profile of line SR-1 was surveyed using the top of the spillway foundation mud slab at block SP-8 as a reference plane and the horizontal location was measured from the upstream face of the spillway at the heel. Seismic Lines SR-2 and SR-3 Lines SR-2 and SR-3 were located on the right side of the diversion channel that was constructed to divert the flow of the Middle Fork of the Bradley River into the Bradley Lake reservoir.In a section of the channel approximately 800 feet downstream (south)of the diversion of the original channel,lateral erosion of the western bank of the new channel has been observed.To assess whether remedial action will be necessary to prevent the river from creating a new channel to the west in this area (thus eliminating the contribution of the Middle Fork into Bradley Lake reservoir),a seismic refraction survey was planned to determine the depth to competent bedrock along this stretch of the river.Transport to the site was provided on Wednesday,July 23,by Alaska Maritime Helicopters of Homer. Results of Seismic Refraction Investigation Page 4 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 As shown in Drawing No.SK-02-8221-76,attached,Line SR-2 was located along the terrace on the right bank of the Middle Fork between the river channel and the 25-foot-high waste disposal berm of shotrock (derived from construction of the diversion channel)deposited in Waste Fill Area No.2.A 24-channel geophone spread with a geophone spacing of 10 feet and a total line length of 230 feet was employed for this seismic profile.Using the 16-lb.sledgehammer and striker plate combination,five shotpoints were recorded for this line.In addition,all five shotpoints were recorded a second time using a seismic energy source consisting of BCE (Betsy Carbon Electric)8-gauge black powder shells assembled for seismic fieldwork by Betsy Seisgun,Inc.,of Tulsa,Oklahoma.These shells were loaded into 1-3 foot deep hand-dug shotholes stemmed with soils,tamped,and then covered with portable blast mats to prevent flyrock.The profile of SR-2 was surveyed by use of a rag tape,hand level,and fiberglass level rod. Seismic Line SR-3,the third and final profile of the seismic refraction survey,was recorded along the crest of the berm of shotrock constituting Waste Fill Area No.2 west of the diversion channel (see Drawing No.SK-02-8221-76,attached).A 24- channel geophone spread with a geophone spacing of 13 feet and a total line length of 299 feet was utilized for this profile.The seismic energy source for this profile was restricted to the 16-lb.sledgehammer and striker plate for the following reasons: 1)the difficulty of hand-excavation of shotholes for the BCE 8-gauge black powder shells in the dense fill material;2)the location of the transport helicopter in standby mode at the center of the seismic spread,and 3)rapidly deteriorating weather with a lowering cloud ceiling. Data Processing and Interpretation The seismic data were processed and interpreted using the SIPT2 suite of seismic refraction programs developed by Rimrock Geophysics of Lakewood,Colorado. SIPT2 is an enhanced PC version of SIPT,a time-proven refraction interpretation method developed over a number of years by the U.S.Bureau of Mines and the U.S. Geological Survey.SIPT2 arrives at the first approximation of the seismic interpretation using delay-time methods,then improves the computed subsurface model through a number of iterations of seismic ray tracing. Comments regarding the individual seismic profiles are provided in the following paragraphs. Seismic Line SR-1 Figure 2 presents a composite travel-time plot for all five of the shotpoints recorded into Line SR-1 at the Bradley Lake Dam spillway.Figure 3 is the interpreted velocity-depth section corresponding to this plot.On the travel-time plot,the horizontal distance in feet is given at the top of the plot,and the relative geophone Results of Seismic Refraction Investigation Page 5 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 positions are indicated along the horizontal axis at the bottom of the plot.The geophone numbers ("Geo”)correspond with the geophone numbers posted just above the geophone symbols in Figure 3,and the shotpoint locations ("SP”)on the travel-time plot correspond to the shotpoints shown schematically in Figure 3. The travel-time plot gives the time (in milliseconds)that it took the seismic wave (in this case the P-wave,or compressional wave)to travel from the respective shotpoint locations to each of the geophones in the seismic spread.While the entire seismic wavetrain is recorded by the seismograph in digital format over a selected time window,only the first arrival of the seismic energy (the so-called "first break”)is used in refraction analysis.Because the shotpoints are recorded sequentially,there is a travel-time curve for each shotpoint.Five shotpoint locations were recorded for Line SR-1,and two of these shotpoints were repeated for a second time,resulting in a total of seven travel-time curves for this line.The travel-time curves for Line SR-1 appear somewhat erratic compared to normal refraction travel-time plots for the following reasons:1)the very short seismic spread length,resulting in brief travel times relative to the precision possible when timing seismic waveforms;and 2)the waveform irregularities commonly seen when attempting to couple the geophones directly to a bedrock surface.Nevertheless,patterns emerged when seismic travel times for all of the shotpoints were superimposed on one composite travel-time plot. In Figure 2,three different materials have been identified on the travel-time curves. The numeral "3”has been assigned to refracted seismic arrivals from the competent bedrock surface.The numeral "2”on the plots identifies zones of weathered rock and/or rubble in the shallow subsurface overlying competent bedrock.The numeral "1”on the travel-time curves identifies what are thought to be out-of-the-plane refractions from energy traveling along the surface of the concrete mud slab at the base of the spillway structure.This effect is apparent on the travel-time curves for geophones 1-12 (which were located very close to the mud slab)for shotpoints 1 /7, .2,and 3.The total travel time from shotpoint 1 /7 (east end of the spread)to geophone 23 (west end of the spread)is shorter than the travel time from the west end of the spread to the east end.This total time discrepancy indicates different travel paths depending on which end of the spread is energized.West of geophone 12,the mud slab concrete was offset farther from the geophones,so that all of the seismic arrivals for geophones 13-23 are thought to be from the geologic materials in the foundation rather than from the concrete mud slab. The composite travel-time plot for Line SR-1 indicates three zones exhibiting travel- time delays in the bedrock arrivals:geophones 3-5,13-15,and 17-21.These delays indicate zones of lower-velocity material infilling shallow irregularities or "pockets”in the competent bedrock surface.The "pockets”may represent zones of differential weathering of the bedrock,or they may simply represent zones of rubble overlying an irregular bedrock surface caused by glacial scour. Results of Seismic Refraction Investigation Page 6 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 An interpreted velocity-depth section for Line SR-1 is presented in Figure 3.A two- layer seismic stratigraphy is indicated,consisting of weathered bedrock over competent bedrock.The numerals posted along the competent bedrock surface represent the computed locations of emergent seismic rays from the respective shotpoints.Because of the "sideswipe”arrivals from the concrete mud slab,bedrock velocity is poorly determined for this short spread.Based on higher-quality (reversed)bedrock velocity data from Line SR-2,a bedrock velocity of 11,500 ft/sec has been assumed for the Line SR-1 interpretation. Elevations on the velocity-depth section are relative to an assumed elevation of 100 feet for the top of the mud slab.Because of the false signals from the concrete mud slab over the east half of the seismic line,the data for shotpoints 1 /7,2 ,and 3 (geophones 1-12)were not used for this interpretation.Due to the weakness in the data over the east half of the line,the indicated thickness of the weathered zone at the east end of the line is poorly determined.The most useful aspect of the velocity- depth section may be the locations of the "pockets”in the top of the competent bedrock surface if they are related to differential weathering of the rock. Seismic Line SR-2 Two independent interpretations were computed for Line SR-2,located on the terrace on the right bank of the Middle Fork diversion channel:one solution using the seismic data for the 16-lb.sledgehammer source,and the other solution using the data from the BCE 8-ga.black powder shells.The travel-time plots for the sledgehammer source and the BCE shells are shown in Figures 4 and 6, respectively,while the corresponding interpreted velocity-depth sections are given in Figures 5 and 7.The elevations on the depth sections are relative to an assumed elevation of 100 feet at a temporary benchmark on top of a large boulder in the central portion of the line. The data sets for both of the energy sources were weak,particularly with regard to refracted arrivals from the bedrock.True "first break”arrivals were absent for most of the bedrock refractions.The bedrock arrivals (denoted by the numeral "3”on the travel-time plots)were derived by digital filtering of the seismograms to determine relative arrival times for later phases of the seismic wavelet (such as the first trough or first peak),then subtracting an appropriate phase delay to estimate the first break times.Due to burial of the shells in hand-dug shotholes in the loose surficial soils, the arrival times for the BCE shells source are somewhat earlier than the arrival times for the sledgehammer source at the ground surface. Both interpretations for Line SR-2 indicate a three-layer seismic stratigraphy underlying the terrace:a surficial layer of organic soils with a seismic velocity of about 1200 feet per second (ft/sec),a second layer interpreted to consist of glacial Results of Seismic Refraction Investigation Page 7 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 till with a velocity of 4500-4800 ft/sec,underlain by bedrock with a velocity of 11,300- 11,600 ft/sec. Because of the weakness of the refracted signals from the bedrock,the interpretation of the bedrock morphology differs for the two seismic sources. However,the interpretation of the total thickness of overburden at the central portion of the line (where the bedrock interface is apparently deepest)is similar for both seismic energy sources. Seismic Line SR-3 The travel-time plot for Line SR-3 is presented in Figure 8,and the corresponding interpreted velocity-depth section is given in Figure 9.For this line,located at the crest of the waste disposal berm in Waste Fill Area No.2 west of the Middle Fork diversion channel,the seismic data were the weakest of the July 2003 survey.Due to time constraints,rapidly deteriorating weather,and the location of the transport helicopter in standby mode at the center of the spread,the energy source was restricted to the use of the 16-lb.sledgehammer.Because of gusty winds across the crest of the berm,the recorded seismic data were very noisy.Digital filtering of the data was required to discern the trends of the refracted arrivals.As seen on the travel-time plot,arrivals thought to be refracted energy from the bedrock (layer "2”) are very sparse,so that the dataset is incomplete. Just two layers have been interpreted from the travel-time data:1)shotrock fill;and 2)bedrock.Based on the results from Line SR-2,there may well exist a layer of glacial till underlying the fill and overlying bedrock.The "bedrock”arrivals for shotpoints 7 and 8 at the north end of the line (designated with the numeral "2”onthetravel-time plot)may be refractions from the top of a till layer rather thanrefractionsfromaslopingbedrocksurface,as they have been interpreted.Without a more complete data set,it is not possible to determine which is the case.If glacial till is present beneath the shotrock fill,the computed depth to the bedrock interface using a 2-layer seismic model is most likely too shallow. Using representative velocities derived for the shotrock fill beneath Line SR-3 and for glacial till and bedrock beneath Line SR-2,limited travel-time computer modeling was conducted for Waste Fill Area No.2.The modeling indicated that a layer of glacial till underlying the manmade fill would not be detectable by refraction methods if the fill comprised more than about half the total thickness of material overlying bedrock.This is due to a geometrical limitation of the refraction method known as the "blind zone”or "hidden-layer”problem.The problem occurs when an intermediate layer cannot be detected by the refraction technique because of insufficient velocity contrast or thickness of the layer.Commonly,this intermediate layer overlies a high-speed layer such as bedrock.The problem results from the geometry of the refraction method,and no rearrangement of the geophone layout Results of Seismic Refraction Investigation Page 8 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 can remedy the lack of detection of the hidden layer.The error that results from this lack of detection is that the computed depth to the high-speed layer is too shallow. Summary and Recommendations The seismic refraction investigation conducted at the Bradley Lake Hydroelectric project in July 2003 is thought to have provided useful information with regard to consideration of possible mitigative measures at two locations within the project. Seismic Line SR-1,conducted on the upstream bedrock face of the Bradley Lake Dam spillway foundation,contains three zones exhibiting minor seismic travel-time delays.These zones are thought to represent low areas or "pockets”in the surface of competent bedrock.The pockets may indicate differential weathering in the underlying rock,which in turn may be related to seepage observed in the foundation drain gallery and on the downstream face of the spillway.Alternatively,they may simply indicate an irregular bedrock surface caused by glacial scour. Because of the relatively long wavelength of the seismic signal from a sledgehammer impact on a weathered bedrock surface (estimated to be 60-80 feet for the frequencies and velocities measured at this location),the seismic refraction method is not ideally suited for the detection of zones of bedrock weakness only a few feet in thickness.Further seismic refraction investigation of the spillway seepage problem is not recommended,although other geophysical methods (such as the electrical Self-Potential,or SP,Method)may have application. In contrast,the problem of determining the depth to bedrock at the Middle Fork diversion channel location is well suited to the seismic refraction method.A significant thickness of a layer of glacial till was detected beneath Line SR-2.While the computed morphology of the bedrock surface differed somewhat for the sledgehammer and BCE shells energy sources for this line,the total thickness of overburden was similar for both solutions at the location of the lowest bedrock elevation.If additional seismic refraction work is conducted in this area,the confidence in the seismic interpretation could be improved considerably using a more powerful seismic energy source such as binary explosives. The seismic results for Line SR-3 surveyed at the crest of the waste disposal berm in Waste Fill Area No.2 were the most uncertain of the seismic investigation due to limited penetration of the manmade fill using a sledgehammer seismic energy source.Further seismic work in this area might be beneficial if binary explosives were used as the energy source,although shothole preparation in the dense fill material would be laborious and time-consuming.Furthermore,even if explosives were used for the seismic energy source,the "hidden-layer”problem in seismic refraction interpretation may prevent the detection of glacial till beneath the shotrock fill and thus limit the accuracy of the computation of depth to bedrock. Results of Seismic Refraction Investigation Page 9 Bradley Lake Hydroelectric Project,Kenai Peninsula,Alaska December 11,2003 |have appreciated the opportunity to conduct this reconnaissance geophysical investigation with R&M Consultants,Inc.,at the Bradley Lake Hydroelectric Project. Please contact me if there are any questions regarding the seismic field program or the interpretation of the geophysical results. Sincerely yours, NORTHLAND GEOPHYSICAL,PLLC hemes 8.NWiamna. Thomas R.Williams,President Washington State Licensed Geologist No.147 EMERGELADDER -CREST EL 1160.00% a HANORAIL LOCATION OF ROCKT CONCRETE INTERFACE WILL See ROCK Ceee"EL eas|f NON|'Ler 113490!aN "\{INTERMEDIATE >NNOTRAININGWALL \N|i \\|west Trainee wboEASTFralwneNNL4/NIAYPB1)i \%SOS >J)i \\PosLS/NL sS2S*S l 7 TINS N\C Ne SONSV\NX TN NORSN N\\\ON SQL TS 11}\\\ygsenss\NOS]i \BEDROCK NN .}yf)leprasee SDs//|/NL -nag Ra 7 }//a _TeSA7 ™ SIs a 7 PLAN-SPILLWAY PLAN -BRADLEY LAKE DAM SPILLWAY Drawing No. Showing Location of Seismic Line SR-1 SK-01-8221-76 Scale 1”=60 ft Ref Drawing 8221-76 10/21/03 R&M Consultants,Inc.Bradley Lake Dam Spillway Seepage and Uplift Study Sketch-01 =pss T wy WORK AREA Lis >. 2'6% LE 3 \OCURVEGK4,4 STA 10+=ryZz,Yeaoeacn»;Seismic Refraction ty,oe |teems=<4 (a N \it LG'Survey Lines rm WE,*5 JimaENFaHth@MN SSyy 2 ws --"tn.\CS Bradley Lake Hydroelectric Project =MIDDLE FORK BRADLEY RIVERI_-|!\IE 0 Scale 40 feet STREAM DIVERSION ( Drawing No.Bradley Lake Hydroelectric Project PLAN -MIDDLE FORK DIVERSION EROSION AREA SK-02-8221-76 Showing Location of Seismic Lines SR-2 and SR-3 10/21/03 Scale 1”=40 ft Ref Plate 11 and 12,Exhibit F Sketch-02R&M Consultants,Inc.Middle Fork Bradley River Diversion Channel Erosion Study Distance from First Geophone (feet) 0 10 20 30 40 50 60 7A i es 20 |EAST AGE 4 WESTLUovaHas.| a 1ioe422(-Ve Zones with Travel-Time Delays 7 SOD SeismicWaveTravelTime(milliseconds)10 --"1 190 |Qut-of-the-plane Refractions 7 |.from Concrete Mud Slab (7)4 |Ss : 5 0 SP ?2 3 5 6 Geo 1 2 4 6 8 10 12 14 16 18 20 22 Geo FIGURE 2 Prepared by:Seismic Line SR-1NORTHLANDGEOPHYSICAL,pitc Prepared for: R &M CONSULTANTS,INC. Travel-Time Plot Bradley Lake Dam Spillway 110 TTTTTPTTTTTTTTTTTrrrr EAST 90 QOL prtprlerpytydpiey | NEO CCECOOOOCCEEOOOOCEEOOOOOEOS PEPUrPPri pererrridt PETEPPPeryerrrerreeger rend 110 WEST Ground Surface L11lILLl90 KKKSMHS 3 sP45 RRS=SOKSSS I Shotpoi i ped LRRKRSSDni otpoint Location ;KOO KK RE EKG2eophonePositionsSh37KO?CS,KKK2SraOESSites=100 PR PRESB KL RR ELAR 1003sP2KOROYBRERARRRRRSteeGfLAKRERRARRRRRR+EE COSCOSCOOCOR EY SonaZFBPKKLYPKRYRBFESSKOKLRLVKRPPKRPIKLLPLLILRBRLEERKEKKEKEKK|@ BOKK OIKLR OC GERRBEARAR SKK KR KKK RNGEbKRLVPKRIVKRIRKKKKKKKBedrockRKKKKKKRLKKS J3PIKRPIKRPGERRRRRRKRRRRGEBBIOK,11,500 RUSE PRRDFSRPRPPSGEERRR.SRR 7:ERE KKK KKK RRR KKK KKK KKK LRG5|REESBSERSNINIHRHHHRI THCI TT TIS_ PE Be oiccoreioreccreccroncconccorereneroneconecoraereneconcereereeeen aera 2 | Lu a petit title titi litt 0 10 20 30 40 50 60 Distance from First Geophone (feet) Prepared by: NORTHLAND GEOPHYSICAL,pPitc Prepared for. R &M CONSULTANTS,INC. FIGURE 3 Seismic Line SR-1 Velocity-Depth Section Bradley Lake Dam Spillway HORIZONTAL SCALE IN FEET 01234567 8910 VERTICAL EXAGGERATION:2 TO 1 2 Distance from First Geophone (feet) 0 50 100 150 200 50 l |Tor UT FT Uo '7 foo |Tor rd bt tf b bg |Perr dg ft dt t Tot |Pore &do TF ft tog |Tier YT F ¢7 JY 50 s 4 -SOUTH NORTH J Bao kt 4 40-VJ =_Q - -_oO i . ®@ - = 4 2 C 3 7 -&Ff .a:1 ®30 --30£FE ° ,: i . 3Gr 7>_a -=©C 2 s 7FEC é 4 o 20 [J /-20 >LL.©_ 2 4SoF: 2 :zs 5 _5 . Qe 10 7 :10 0 x *x Fd mo Sp 5 4 1 2 Sp Geo 1 2 4 6 -8 10 12 14 16 18 20 22 24 Geo FIGURE 4 Seismic Line SR-2 resets LAND GEOPHYSICAL (Sledgehammer Energy Source),PLLC . Prepared for.Travel-Time Plot R &M CONSULTANTS,INC.Middle Fork Diversion Channel Prepared by: NORTHLAND GEOPHYSICAL,Pitc Prepared for:ElevationRelativetoTemporaryBenchmark(feet)TTT TTT TTT TT TTT TTT TT ttt ttt rg 130 F SOUTH NORTH 4E4 120 F Ground Surface 7 5 Geophone Positions FEps"fe 4 110 E Shotpoint Location ee J :Sil 1p eee | Gee eee eee 4 100 |C Qo etetie:Heguam Seoge aK VaFsgOe-11101-28101-Or 101 G1 4 ORR 3 E Reh dg idi tigi:OS 4 39OERESPETETETERAAPORYR|POCO CONE NEEDS BAPE LREELEK 3BQQQPPPMRAZHIPPPOQOOOO?-4 60FQRQQQQDPRQPQPRVQPQPPVLROQVORY_FBQPQOPQPOHROKY?QO QOIPQCODO_-}FQQOVQOQ OOOO:BOK,Bedrock KOKKOOOOKO JERRRKKH!1600 fsee KKKRRRERERS.|50ERRRKRRRRRKKKKOKOKKKKKKKKKKKK| oe 0 50 100 150 200 Distance from First Geophone (feet) FIGURE 5 HORIZONTAL SCALE IN FEET Seismic Line SR-2 >ns 0 (Sledgehammer Energy Source)VERTICAL EXAGGERATION:2TO 1 R &M CONSULTANTS,INC. Velocity-Depth Section Middle Fork Diversion Channel Distance from First Geophone (feet) 0 50 100 150 200 ft 50 oT potrtrrrrty rrr rrr rr ry rrr rrrrrryrrrrrrtrrryrrrrrrriy 50 -SOUTH NORTH + $40 |40 c r 4SF: 2 c / -Ff 7 : @ 30 +30£-a =&£: ro)r 7>'7©r a 7 -bs - @ 20 [--]20>C 7coC7=&£ 2 7 £C : a2 7 7 Pr ae]7 qf 10 o>"-0 SP 5 4 1 2 SP Geo 1 2 4 6 8 10 12 14 16 18 20 22 24 Geo FIGURE 6 Seismic Line SR-2 Prepared by (BCE Shells Energy Source)AL .NORTHLAND GEOPHYSICAL,PLtc Travel-Time Plot R &M CONSULTANTS,INC.Middle Fork Diversion Channel 130 TTT TT TT TTT TTT TTT TTT TTT Tt tr |130 F SOUTH NORTH 4 120 E 4 120 Ground Surface . F Geophone Positions sp 24 =24 7)110 Esps"fe (4 110 100 -==SSS --O--4 100SassllCQcaeleTmrnneveraFPeekkkctetee :1 E ORR TEL ES 4800 fS00Fatee BSEKKKKFOETHOO17OrOs-OOD :E WAL TED ET EL ESET ESET ECTS AOR 370FXR:=OF FO KRESSKKS |70EOIETETATPTETIRRRIENREFPFPERRO!B0 Fe RRRRRSEEETE RRL RLS,F 59EFHSS.3ESRRRRRKRKHOI,BeMtOK SKEKY0)SERRESSSS tie SSS;SOCCCOCCCOES OO OOO OO OOO O00 OTEElevationRelativetoTemporaryBenchmark(feet)s1"7'|di"1'|1a"|:a"y:i"i"|:|:i(ahsx50 QL QRQLSISEE2 go Feoborerrrrii tire i'd gg 0 50 100 150 200 Distance from First Geophone (feet) FIGURE 7 HORIZONTAL SCALE IN FEET S eismic Line Ss R-2eePreparedbyare)0 (BCE Shells Energy Source)NORTHLAND GEOPHYSICAL,Puc VERTICAL EXAGGERATION:2T01preparedfo Velocity-Depth Section R &M CONSULTANTS,INC.Middle Fork Diversion Channel Distance from First Geophone (feet) 0 50 100 150 200 250 300 80 a ]|Trirrre?d td |Tr?r?robprpi dd |Pr?rIrird tl |Trrirr?r itd }'rrirrredd |TErrirrtidl j 1 4 80 EF SOUTH NORTH 4 70 J 70 @ &:TC -aq c 7 a8sOEJ 60®-3274 E so E {50 ®5 :£F : @ 40 FE "y 40>x - 9 C q FE : 2 30 &J 30©F Js-q AS)E 7£20 &N 4 20 G F : ®F Y z Oo Ff : 10 &X>J}10o&a a a a Vs ce|n-_n_a\/nn do*%**x x * sp 1 2 5 6 8 7 sp Geo 1 2 4 6 8 10 12 14 16 18 20 22 24 +Geo FIGURE 8 NORTHLAND GEOPHYSICAL Seismic Line SR-3 »PLLC .prepared for Travel-Time Plot R &M CONSULTANTS,INC.Middle Fork Waste Fill Area No.2 40 erry yr perp pr rrr prt rrr rr 140 _3 SOUTH Geophone Positions Shotpoint Location Ground Surface NORTH :3”ESP 44 6 Pe 2 rete SP 8 gp73 ”5 2 Sets ais wie wie aiseretreteere sueBFSabuaesleaohnleiphaneanenria4 120S:Eeeneenetaecnes ecancnees::S 110 Saeheenetnecnetnecne BRSS,11022150flsecLeiOe))Seaeeesate cae ROK :©a S22 $eee aed LLL LLE =5 100 :;PRS K RORROO Ig 109e@Seaesai:OS.=90 E .Re!KKK KKKKSKKO.4 80©QRRR UE URSUSE UE UID OR OOK OOK KOK HNODERRRRKKKHEEEEEEAOOKORKOKROKLS|B30 Fe SO OERERR EATER OQ OOSOCS.=DE RRR KKK EEEEBR KKKKO 3PBSRRKORKKKKEIOOKBedrockRKKKKRR5ERRRKKKKORORBANovane11.300 Nees ROE =G70 EF SRK RRR KKK RKO KE HN CHK 70BEKROHNBEKOKOROKKNiy60E{60TESRRKERRKKKJ so Exebosrrrriir tippers te A 6 0 50 100 150 200 250 300 Distance from First Geophone (feet) HORIZONTAL SCALEINFEET FIGURE 9 Prepared by.a =Seismic Line SR-3 NORTHLAND GEOPHYSICAL,pitc Prepared for. R &M CONSULTANTS,INC. VERTICAL EXAGGERATION:2T0O 1 Velocity-Depth Section Middle Fork Waste Fill Area No.2