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Home My WebLink AboutStetson Creek Diversion and Cooper Lake Dam Facilities Project Geotechnical Baseline Report - May 2012 - REF Grant 7040005STETSON CREEK DIVERSION AND COOPER LAKE DAM OUTLET FACILITIES GEOTECHNICAL BASELINE REPORT FINAL REPORT MAY 2012 PREPARED BY: STETSON CREEK DIVERSION AND COOPER LAKE DAM OUTLET FACILITIES GEOTECHNICAL BASELINE REPORT FINAL REPORT MAY 2012 PREPARED BY: Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page i Geotechnical Baseline Report – Final May 2012 TABLE OF CONTENTS ACRONYMS AND ABBREVIATIONS ................................................................................... IV 1.0 INTRODUCTION.............................................................................................................1-1 1.1 PURPOSE .................................................................................................................. 1-1 1.2 PROJECT DESCRIPTION ........................................................................................ 1-1 1.2.1 Location ......................................................................................................... 1-1 1.2.2 Background .................................................................................................... 1-1 1.3 REPORT STRUCTURE ............................................................................................ 1-2 2.0 OVERVIEW OF PROJECT IMPROVEMENTS ......................................................... 2-1 2.1 DIVERSION DAM .................................................................................................... 2-1 2.2 DIVERSION PIPELINE AND CONSTRUCTION ACCESS .................................. 2-1 2.3 OUTLET WORKS.....................................................................................................2-2 2.4 BORROW AREAS .................................................................................................... 2-2 3.0 SITE CHARACTERIZATION ....................................................................................... 3-1 3.1 LITERATURE REVIEW .......................................................................................... 3-1 3.2 FIELD INVESTIGATIONS ...................................................................................... 3-2 3.2.1 Geological Reconnaissance ........................................................................... 3-2 3.2.2 Geophysical Survey ....................................................................................... 3-2 3.2.3 Test Pit Explorations ...................................................................................... 3-3 3.2.4 Exploratory Drilling ....................................................................................... 3-3 3.3 LABORATORY TESTING.......................................................................................3-3 4.0 GENERAL PROJECT SETTING .................................................................................. 4-1 4.1 GEOLOGY ................................................................................................................ 4-1 4.1.1 Regional Geology .......................................................................................... 4-1 4.1.2 Regional Seismicity Overview ...................................................................... 4-2 4.2 LOCAL GEOLOGY .................................................................................................. 4-2 5.0 GEOTECHNICAL PROPERTIES AND MATERIAL BASELINES ......................... 5-1 5.1 UNIT I: SLATE OF THE VALDEZ FORMATION ................................................ 5-1 5.1.1 Material Description and Characteristics ....................................................... 5-1 5.1.2 Material Baselines .......................................................................................... 5-2 5.2 UNIT II: GLACIAL TILL ........................................................................................ 5-4 5.2.1 Material Description and Characteristics ....................................................... 5-4 5.2.2 Material Baselines .......................................................................................... 5-4 5.3 UNIT III: GLACIAL OUTWASH DEPOSITS ........................................................ 5-4 5.3.1 Material Description and Characteristics ....................................................... 5-4 5.3.2 Material Baselines .......................................................................................... 5-5 5.4 UNIT IV: TERMINAL MORAINE DEPOSITS ...................................................... 5-5 5.4.1 Material Description and Characteristics ....................................................... 5-5 5.4.2 Material Baselines .......................................................................................... 5-5 Page ii Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final 6.0 BASELINES FOR PROJECT IMPROVEMENTS ...................................................... 6-1 6.1 DIVERSION DAM .................................................................................................... 6-1 6.1.1 Diversion Dam Baseline Conditions .............................................................. 6-1 6.1.2 Geologic Units ............................................................................................... 6-1 6.1.3 Geologic Interpretation .................................................................................. 6-1 6.1.3.1 Surface Conditions .......................................................................... 6-1 6.1.3.2 Subsurface Conditions .................................................................... 6-1 6.2 DIVERSION PIPELINE AND CONSTRUCTION ACCESS .................................. 6-3 6.2.1 Diversion Pipeline and Construction Access Baseline Conditions ................ 6-3 6.2.2 Geologic Units ............................................................................................... 6-3 6.2.3 Geologic Interpretation .................................................................................. 6-3 6.2.3.1 Surface Conditions .......................................................................... 6-3 6.2.3.2 Subsurface Conditions .................................................................... 6-4 6.3 SIPHON OUTLET WORKS ..................................................................................... 6-7 6.3.1 Siphon Outlet Works Baseline Conditions .................................................... 6-7 6.3.2 Geologic Units ............................................................................................... 6-7 6.3.3 Geologic Interpretation .................................................................................. 6-7 6.3.3.1 Surface Conditions .......................................................................... 6-7 6.3.3.2 Subsurface Conditions .................................................................... 6-8 6.4 BORROW AREA .................................................................................................... 6-10 6.4.1 Siphon Outlet Works Baseline Conditions .................................................. 6-10 6.4.2 Geologic Units ............................................................................................. 6-10 6.4.3 Geologic Interpretation ................................................................................ 6-10 6.4.3.1 Surface Conditions ........................................................................ 6-10 6.4.3.2 Subsurface Conditions .................................................................. 6-10 7.0 REFERENCES .................................................................................................................. 7-1 LIST OF TABLES Table 5-1 Rock and Soil Units ............................................................................................. 5-1 Table 6-1 Stetson Creek Diversion Dam Subsurface Baseline ............................................ 6-2 Table 6-2 Diversion Access and Pipeline Subsurface Baseline ........................................... 6-5 Table 6-3 Siphon Outlet Works and In-Line Facilities Subsurface Baseline ....................... 6-9 Table 6-4 Diversion Pipeline Instrumentation Building Subsurface Baseline ..................... 6-9 Table 6-5 Siphon Instrumentation Building Subsurface Baseline ....................................... 6-9 Table 6-6 Borrow Area Subsurface Baseline ..................................................................... 6-11 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page iii Geotechnical Baseline Report – Final May 2012 LIST OF FIGURES Figure 1 Location Plan Figure 2 Site Plan Figure 3 Diversion Dam and Intake – Plan and Elevation Figure 4 Diversion Pipeline STA 0+00 – STA 10+00 Plan & Profile Figure 5 Diversion Pipeline STA 10+00 – STA 25+00 Plan & Profile Figure 6 Diversion Pipeline STA 25+00 – STA 40+00 Plan & Profile Figure 7 Diversion Pipeline STA 40+00 – STA 55+00 Plan & Profile Figure 8 Diversion Pipeline STA 55+00 – STA 70+00 Plan & Profile Figure 9 Diversion Pipeline STA 70+00 – STA 85+00 Plan & Profile Figure 10 Diversion Pipeline STA 85+00 – STA 100+00 Plan & Profile Figure 11 Diversion Pipeline STA 100+00 – STA 109+00 Plan & Profile Figure 12 Diversion Pipeline STA 109+00 – STA 118+65 Plan & Profile Figure 13 Cooper Lake Dam Outlet Works – Plan Figure 14 Cooper Lake Dam Outlet Works – Profile LIST OF APPENDICES Appendix I 2009 Geophysical Seismic Refraction Survey Program Appendix II 2010 Geophysical Seismic Refraction Survey and Video Core Logging Program Appendix III 2009 Test Pit Procedures, Logs, and Photographs Appendix IV 2010 Boring Procedures, Logs, and Photographs Appendix V Selected Historical Exploration Logs Appendix VI 2009 Laboratory Testing Program and Results Appendix VII 2010 Laboratory Testing Program and Results Page iv Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final ACRONYMS AND ABBREVIATIONS Chugach Chugach Electric Association, Inc. EL Elevation EPA Environmental Protection Agency FERC Federal Energy Regulatory Commission FPC Federal Power Commission fps feet per second ft foot (or feet) GBR Geotechnical Baseline Report H Horizontal HDPE High-Density Polyethylene kg Kilogram LA Los Angeles M Magnitude mg Milligram MWH MWH Americas, Inc. NEIC National Earthquake Information Center NPC North Pacific Consultants pcf Pounds per cubic foot Project Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Project psi Pounds per square inch RQD Rock Quality Designation SMR Slope Mass Rating STA Station (Stationing) TAI TestAmerica, Inc. USACE U.S. Army Corps of Engineers USBR United States Bureau of Reclamation USGS U.S. Geologic Survey USSD United States Society on Dams V Vertical Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page v Geotechnical Baseline Report – Final May 2012 DISCLAIMER This report has been prepared in accordance with the terms set out in the contract between Chugach Electric Association, Inc. (Chugach) and MWH. The findings of this report are based on explorations, information provided by Chugach, and readily available data and information obtained from public and private sources. Additional studies (at greater cost) may or may not disclose information which may significantly modify the findings of this report. Neither MWH nor Chugach or any person acting on any of their behalf, make any warranty, express or implied, or assume any liability with respect to the use of any information, method, product, process, or statement contained in this report. MWH was neither requested to perform nor has performed environmental or regulatory investigations or assessments in connection with this investigation of the facilities described in this report. Also, MWH was neither requested to, nor has performed, any economic analyses or detailed evaluation of any permits or licenses in association with this Geotechnical Exploration Report. The content of this report is governed by confidentiality clauses in the contract between MWH and Chugach. The contents of this document may not be disclosed to other parties in a manner not consistent with the terms of the confidentiality clauses of the contract. Page vi Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final This page is intentionally blank. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1-1 Geotechnical Baseline Report – Final May 2012 1.0 INTRODUCTION 1.1 PURPOSE This Geotechnical Baseline Report (GBR) is issued as part of the construction contract documents. The purpose of this report is to provide contractual representations of the subsurface conditions that are anticipated at the Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Project (Project). The GBR has been prepared based on geometry and physical locations of the conceptual Project at the time of this GBR. Baselines statements included herein are not applicable to alternate locations of the Project features that may be proposed by the contractor. Contractual representations in this GBR, referred to as “baselines,” are derived from information and data gathered through geotechnical subsurface explorations, testing and other data, analyses, evaluations and professional opinions. The following clarifications should be considered when interpreting this GBR: The baselines presented in this GBR are only applicable to the work required for permanent works as specified in the Contract Documents and do not apply to any other temporary surface or work that the contractor may perform for their convenience, including site grading, temporary slopes, and etcetera. Interpretations shall be based on the GBR in its entirety. Reliance on singular words, phrases or sentences out of context of the GBR as a whole shall be done at the contractor’s own risk. Statements presented in this report that indicate an anticipated or assumed condition, regardless of the wording (e.g., “it is anticipated that…”, “these conditions apply to…”, “the baseline is…”, etc.), represent a contractual baseline statement. Statements that indicate conditions at a particular location that will negatively impact construction do not imply that such conditions do not exist at other locations of the Project. 1.2 PROJECT DESCRIPTION 1.2.1 Location The Project is located near the northern portion of Cooper Lake in the Kenai Borough of Alaska, approximately 4 miles south of the community of Cooper Landing. The Project is located within Sections 16, 17 and 18 of Township 4 North, Range 3 West of the Seward Meridian. The Project location with respect to the surrounding physical features is shown on Figure 1. 1.2.2 Background As part of the conditions stipulated in the first Federal Energy Regulatory Commission (FERC) relicense of the Cooper Lake Hydroelectric Project, Chugach Electric Association, Inc. (Chugach) is required to make modifications to the Cooper Lake Hydroelectric Project in an Page 1-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final attempt to improve downstream fish habitat. Prior to the construction of the Cooper Lake Dam, Cooper Lake was a significant source of water flow to Cooper Creek. Since the dam’s construction, flow from Cooper Lake to Cooper Creek has effectively stopped, making the glacial-fed Stetson Creek the primary source of water flowing in Cooper Creek. This shift in flow sources is believed to have caused a decrease in the downstream temperature of Cooper Creek, which is thought to have reduced the quality of fish habitat. The preliminary design Project improvements are intended to increase the water temperature of Cooper Creek by diverting water from Stetson Creek to Cooper Lake and releasing warmer water from Cooper Lake to Cooper Creek. 1.3 REPORT STRUCTURE This report is divided into seven sections as follows: Section 1: Introduction – Introduces the Project and describes the intent of the document. Section 2: Overview of Project Improvements – Provides a description of the proposed improvements to the Project. Section 3: Site Characterization – Provides descriptions of the methods used to characterize the site. Section 4: General Project Setting – Provides a description of regional geologic and tectonic characteristics. Section 5: Geotechnical Properties and Material Baselines – Provides baselines for the soil deposits and rock formations present at the site. Section 6: Baselines for Project Improvements – Provides baseline descriptions with respect to individual Project improvements. Section 7: References – Provides a list of reviewed Project documents and cited works. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 2-1 Geotechnical Baseline Report – Final May 2012 2.0 OVERVIEW OF PROJECT IMPROVEMENTS Project improvements include a diversion dam on Stetson Creek, a diversion pipeline to convey the diverted water from Stetson Creek to Cooper Lake, an access road to the diversion dam and pipeline, and an outlet facility to release water from Cooper Lake to Cooper Creek in a controlled manner. Descriptions of these Project improvements are presented in the following paragraphs. 2.1 DIVERSION DAM The Project includes a low diversion dam that impounds water from Stetson Creek. The dam site is located approximately 1.2 miles upstream of the confluence of Stetson Creek and Cooper Creek (Figure 2). The dam will consist of a small concrete gravity structure with a weir spillway. The dam is fitted with a series of sluice gates to manage the flow of water being diverted to Cooper Lake and to aid in the removal of silt buildup behind the dam. The diversion structure has a crest length of approximately 57 feet (ft), a spillway height of 9.5 ft and a cross- sectional base width of about 13.5 ft. The base of the structure will be at elevation (EL) 1,420.5 ft, and the weir will be at EL 1,430 ft. 2.2 DIVERSION PIPELINE AND CONSTRUCTION ACCESS The diversion pipeline and construction access will be approximately 2.2 miles long, and will extend from the sluice gates of the diversion dam to an outfall located approximately 1,500 ft south of Cooper Lake Dam. The pipeline will consist of a 42-inch outside diameter, standard diameter ratio (SDR) 21, high-density polyethylene (HDPE) plastic pipe. The pipeline will generally follow slope contours sloping downward from the diversion dam to Cooper Lake at an average grade of 1.8 percent (Figures 3 through 12). The diversion access road will typically be 15 ft wide. The diversion access road will be restricted to 10 ft wide next to the diversion dam, and to 12 ft wide along a gabion wall that will extend from the diversion dam to approximate road station (STA) 3+00. The alignment of the pipeline will generally follow the centerline of the diversion access road from the diversion dam to the diversion outlet; however, the pipeline alignment may vary as field conditions dictate. The pipeline will be buried a minimum depth of 3 ft below grade. The diversion pipeline outlet is located approximately 1,500 ft south of the existing Cooper Lake Dam. The outlet will consist of a diffuser pipe that is intended to limit the exit velocity to minimize erosion. The contractor will be responsible for constructing and maintaining the diversion access road such that it is adequate to support construction activities. Following construction of the diversion dam and pipeline, the contractor will grade and compact the road such that it is suitable for four wheel drive vehicle traffic at the time construction is complete, and such that it is graded to drain free standing water away from the road and Project improvements. It is understood that the construction access is not intended to be a high volume road and that seasonal maintenance by the owner may be required following construction activities. Page 2-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final 2.3 OUTLET WORKS The proposed Site improvements include the construction of an outlet facility to convey water from Cooper Lake to Cooper Creek (Figure 13 and 14). The outlet works will consist of a 30- inch diameter siphon that will be constructed within the existing spillway excavation. Due to elevation constraints of siphon systems, this approach requires that an approximate 30-ft deep trench be excavated into the rock of the existing spillway. The siphon will be primed by diverting flow from the nearby diversion pipeline. Structures associated with the outlet works will include siphon inlet and outlet structures, a siphon fill and vent vault, a concrete plug, an instrumentation vault and an instrumentation building. The inlet for the siphon will consist of a precast structure that will be lowered into place within the reservoir onto a prepared foundation surface. The siphon outlet will be a cast in place structure located within the channel of Cooper Creek. A siphon fill and vent vault will be constructed approximately 60 ft upstream of the existing spillway weir. The vault will house and provide access to the lower fill line and air vent valves. This fill line will access the diversion pipeline in the diversion instrumentation vault located near diversion access road STA 95+25. A concrete plug will be constructed within the rock trench at the location of the existing spillway weir. The plug will function to retain the water of the Cooper Lake Reservoir during and following construction. To help maintain water tightness and resist lateral loading, the concrete plug will include a 2-ft deep by 2-ft wide key. A flow meter vault will be constructed at siphon STA 16+00. This precast vault will house the flow meter and a remotely operated control valve used to adjust the flow of the siphon. The instrumentation building will be located about 65 ft south of the Cooper Creek stream channel near STA 15+50. This precast building will house electrical distribution panels, as well as controls for the outlet gate, flow meter, and charging system. 2.4 BORROW AREAS The project grading will result in a surplus of fill material. To the extent feasible, fill required to meet grades will come from the required excavations. However, additional fill sources may be required if the demand for fill outpaces the rate of excavation. In this case, additional fill may be obtained from an established borrow area located upstream of the right abutment (Figure 13). The soil comprising this borrow area varies in mixtures of sand, silt and gravel, cobbles and boulders. Assuming that the reservoir level is sufficiently drawn down to excavate to EL 1182 ft, an estimated 70,000 cubic yards can be mined from this location. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 3-1 Geotechnical Baseline Report – Final May 2012 3.0 SITE CHARACTERIZATION Site and subsurface characterization were based on literature review and field investigations. Field investigations consisted of geologic reconnaissance, geophysical seismic refraction surveys, exploratory drilling, and test pit explorations. A summary and logs of the site explorations, laboratory testing, geophysical surveys, and selected historical exploration logs are present in Appendices I through VII. 3.1 LITERATURE REVIEW Characterization of the Project site was based on a literature review of documents provided by Chugach, documents on file with MWH, and some publically available documents. Chugach provided documents including original design reports, available design and as-built construction plans, available FERC Part 12 and similar dam safety reports, and other Project-related documents. Project documents on-file such as the 2003 and 2008 FERC Part 12 dam safety reports and relicensing documents were reviewed. Readily available United States Geological Survey (USGS) reports related to the site were also reviewed. A document search of the Alaska Department of Natural Resources’ database did not identify any documents applicable to the Project. A comprehensive list of the documents included in the literature review is presented in the “References” section of this report. Evaluations of the site have included site reconnaissance, borings, trench explorations, and seismic refraction surveys. The following list indicates the known geotechnical-related site explorations in the vicinity of the planned Stetson Creek diversion and Cooper Lake outlet: 1915 – USGS conducts a reconnaissance to identify potential hydropower sites in south- central Alaska, which included an evaluation of Cooper Lake (Ellsworth and Davenport, 1915). 1955 – USGS conducts a geologic site reconnaissance of four lakes in the vicinity of Kenai Lake including Cooper Lake (Plafker, 1955). 1955 – Seven borings, four test pits, one trench and several seismic refraction surveys are conducted near the location of Cooper Lake Dam in association of the Project design (NPC, 1955). Investigations also included a reconnaissance for the potential siting of a Stetson Creek diversion system. 1965 – Fred O. Jones, the project geologist for the design of the dam, conducts the first safety review. The review includes a geologic reconnaissance and trench explorations on the upstream side of the dam (Jones, 1965). Logs and site plans indicating the location of the explorations were not included in the reviewed copy of the report. 1983 – Three observation wells (piezometers) were installed to monitor groundwater levels at various locations within the dam (Stone & Webster, 1988). Exploration logs associated with the installation of the piezometers were not readily available. Details regarding the screen, filter pack, and seal intervals are not known. 2010 – MWH completes a feasibility level geotechnical report for the Project. The study includes 12 test pit explorations, 9 seismic refraction surveys, and a preliminary geological Page 3-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final site reconnaissance. As part of the study four diversion dam sites are identified, and a siphon outlet facility constructed through the spillway is identified as the preferred option. 2011 – MWH completes a Report of Geotechnical Engineering Services for the Project. This study included six subsurface borings, five seismic refraction lines, and additional geologic reconnaissance. As part of this study, the site of the diversion dam was selected and the alignment of the outlet works was refined. Laboratory testing of rock, soil, and aggregates were also conducted. 3.2 FIELD INVESTIGATIONS Field investigations of the Project included, geological reconnaissance, geophysical surveys, test pit explorations, exploratory borings, and laboratory testing. Descriptions of the field investigations and laboratory testing are presented in the following paragraphs. 3.2.1 Geological Reconnaissance MWH conducted multiple geological site reconnaissance of the proposed diversion dam location and pipeline alignment on September 22 and 25, 2009; October 7, 2009; and June 28 through 30, 2010. The purpose of these reconnaissance visits was to evaluate and select a preferred diversion dam site, note the surface conditions at the diversion dam site alternatives, as well as along the accessible portions of the diversion pipeline. Information regarding grades and slopes, vegetation, stream crossings, and other visible geologic features were recorded. As a result of these field evaluations, the site of the Stetson Creek diversion dam and the pipeline alignment were modified from the original location proposed in early 2009 to reduce earthwork, improve hydraulics, and to minimize exposure to steep or potentially unstable slopes. 3.2.2 Geophysical Survey Geophysical surveys consisting of seismic refraction surveys were conducted during both the 2009 and 2010 site investigations. The 2009 seismic refraction surveys focused on assessing subsurface conditions in borrow areas, the Cooper Lake Dam spillway, and along the Cooper Creek reach of the diversion pipeline and construction access. Seismic refraction surveys conducted as part of the 2010 field season focused on evaluating the subsurface conditions at the diversion dam and the Stetson Creek reach of the diversion pipeline and construction access alignment. A total of nine geophysical seismic refraction surveys were conducted at the site between September 29 and October 2, 2009. Seismic refraction survey SL-1 was conducted in the right abutment borrow area. Seismic refraction survey SL-2 was conducted along the approximate centerline of the Cooper Lake Dam spillway. Seismic refraction surveys SL-3 through SL-9 were conducted along the diversion pipeline and construction access alignment. Due to modifications of the alignment, SL-4 and SL-9 no longer correspond with the diversion pipeline and construction access. Locations of the 2009 seismic refraction surveys are indicated on Figures 2, 8, 10, 12, and 13. Results of the 2009 seismic refraction survey are presented in Appendix I. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 3-3 Geotechnical Baseline Report – Final May 2012 Five geophysical seismic refraction surveys were conducted between July 27 and July 30, 2010. Two of the seismic refraction lines were conducted at the diversion dam site, one along the approximate centerline of each diversion dam abutment. The remaining three were conducted along the Stetson Creek reach of the diversion pipeline and construction access. These three seismic lines were biased towards the uphill side of the approximate centerline to investigate the state of the cut materials. Locations of the 2010 seismic refraction surveys are indicated on Figures 2 and 3 through 6. Results of the 2010 seismic refraction survey are presented in Appendix II. 3.2.3 Test Pit Explorations Test pit explorations were conducted during the 2009 site investigations at the locations of the anticipated borrow areas, near the outfall of the diversion pipeline, and along the alignment of a previously considered gravity outlet through Cooper Lake Dam. Test pit explorations were used to identify and characterize subsurface conditions at these locations and to obtain soil samples for laboratory testing. A total of 12 test pits were excavated between October 5 and October 6, 2009. Test pit locations are indicated on Figures 2,12, and 13. Test pit logs are presented in Appendix III. 3.2.4 Exploratory Drilling Six subsurface borings were advanced during the 2010 site investigation consisting of two borings at the diversion dam and four borings along the alignment of the siphon outlet works. The two borings at the diversion dam (B-1-2010 and B-2-2010) were advanced using NQ triple tube diamond rock coring methods. Two of the four borings along the siphon alignment (B-4- 2010 and B-5-2010) consisted of HQ triple tube, diamond rock core borings, which were advanced in the existing spillway channel. The remaining two borings along the siphon (B-3- 2010 and B-6-2010) consisted of soil borings both upstream and downstream of the spillway. The upstream boring was advanced near the edge of Cooper Lake at the time of the exploration. The downstream soil boring was conducted near the proposed control valve and meter vault. The locations of the subsurface borings are presented on Figures 2, 3,and 13. Subsurface boring logs are presented in Appendix IV. Two of the rock core borings B-2-2010 and B-5- 2010 were surveyed using a down-hole televiewer. Televiewer logs are presented in Appendix II. Historical subsurface explorations including borings and test pits were conducted prior to the construction of the existing Cooper Lake Dam. The locations of relevant historical explorations are presented on Figure 13. Logs of the conditions encountered in these historical explorations are presented in Appendix V. 3.3 LABORATORY TESTING A laboratory testing program was developed to determine the physical and corrosion characteristics of the soils and rock encountered at the site. As part of the 2009 site investigation, disturbed grab and bulk soil samples were collected from the test pit explorations. The laboratory testing of these samples included moisture content, grain size distribution, liquid Page 3-4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final and plastic limits, and a suite of corrosion potential tests. Test results of the 2009 laboratory testing program are presented in Appendix VI. Samples from the 2010 site investigation were collected from soil borings, rock core borings, and from the ground surface. Laboratory testing conducted on samples from the soil borings included grain size analysis, moisture content, and plastic limits. Rock core samples were tested for unconfined compressive strength and Young’s modulus. Surface bulk samples from potential borrow sources were evaluated for Los Angeles (LA) abrasion, coarse aggregate soundness, and petrographic composition. Results of the 2010 laboratory testing program are presented in Appendix VII. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 4-1 Geotechnical Baseline Report – Final May 2012 4.0 GENERAL PROJECT SETTING Site conditions were explored and characterized as described in Section 3. Site conditions, based on observations of the site including geology, surface conditions, and subsurface conditions are summarized in the following sections. 4.1 GEOLOGY 4.1.1 Regional Geology The glacially-carved mountains of the Kenai Peninsula in the Cooper Lake area summit at between 5,000 and 6,000 ft above sea level, with as much as 5,000 ft of local relief. Plafker stated “These mountains are a rugged mass with little apparent arrangement of form or drainage (1955).” Creeks of the area all drain to Cook Inlet via the Kenai River. In general, the valleys are heavily forested with spruce and an understory of alder, hemlock, birch, cottonwood, and willow up to an elevation of about 2,000 ft. Dense thickets of alder cover the range between the forest level and the more sparsely vegetated uplands. The Kenai Mountains in the Cooper Lake area are comprised of metasedimentary rocks that are likely from the Mesozoic. Plafker states that Quaternary glaciation has “modified the terrain and removed any chemically-altered material that may have been present up to an altitude of about 4,000 ft (1955).” Cooper Lake and several of the other local lakes are contained behind natural dams of glacial (moraines) and alluvial (outwash) materials within glacially-carved, U-shaped valleys. The crudely stratified glaciofluvial and the stratified alluvial deposits both consist of silt, sand, gravel, and boulder sediments. Talus of unstratified coarse rubble collects on the steeper slopes, a result of very common occurrences of mass-wasting (Plafker, 1955). Rock consists of thinly bedded metasediments of dark gray to black slate with interfingering lenticular beds of hard and massive, fine- to medium-grained graywacke (firmly indurated, angular/sub-angular grained, poorly sorted/well graded sandstone with dark rock/mineral fragments in compact clayey/slatey matrix, otherwise known as a dirty sandstone, typical of submarine turbidite currents) of the Valdez Formation. To a much lesser extent, there are interstratified lenticular bodies of conglomerate that are generally less than 10 ft thick. Locally, small veins and irregular masses of quartz can be found. Structurally, the rock has been tightly folded along a generally north-south axis and overturned to the west. Bedding attitudes in the region are somewhat variable, ranging between north-south to north 65 degrees east and dipping from 75 degrees west to 45 degrees east, but most commonly the dips are near vertical, ranging between 75 degrees west to 75 degrees east. While faulting is common, the displacement along these faults is typically covered quickly by sediments making them difficult to quantify. It is thought that much of the stress and displacement due to faulting is relieved by relatively small movements along established bedding or joint surfaces (Plafker, 1955). Page 4-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final Jointing is typically well developed in the greywacke, while the fine-grained rock possesses an imperfect incipient cleavage that strikes essentially parallel to bedding. Two distinct, transverse sets of widely-spaced, high angle fractures are common. These conjugate joint sets “strike between east and southeast and between north and northwest (Plafker, 1955).” Given that there are many rectangular topographic features in the area, and that many of the local drainages appear to be controlled by these fractures, it appears likely that these joint sets are “probably open and constitute lines of weakness (Plafker, 1955).” A well-developed east-west striking set of vertical jointing is also common, particularly in the greywacke. 4.1.2 Regional Seismicity Overview Regional seismicity is considered high, although no active faults are known with any certainty to be located near the Project site. The nearest possible known source of significant seismicity is the Shelikof Straight fault zone, approximately 12 miles west of the site. The Kenai Lineament, located approximately 15 miles east of the site, is also in close proximity. These features are about 350 and 55 miles long, respectively. The inferred trace of the Shelikof Straight fault zone has a southwest to northeast strike and extends from approximately Kodiak Island to near Palmer. This fault zone is believed to have been active in the Holocene (last 11,000 years). The Kenai Lineament includes the generally north to south valley aligned with Moose Pass, Seward, and Resurrection Bay. The Kenai Lineament is considered potentially active due to possibly- related shallow seismicity. Slightly east and parallel to the Kenai Lineament is the Placer River Fault, which offsets pre- Miocene (older than about 23 million years) Paleogene units, but for which there is no more recent record. Located about 80 miles to the northwest of Cooper Lake is the Holocene Castle Mountain Fault. This fault is considered capable of producing moment magnitude (M) 6 to M7 earthquakes. The Aleutian Megathrust, the source of the M9.2 Good Friday Earthquake of 1964, is located about 170 miles to the southeast. Several active, relatively short faults (Johnstone, Hanning, and Patten Bay) are located in closer proximity (50 to 85 miles), but appear to have been offset during the 1964 event. 4.2 LOCAL GEOLOGY Although the existing dam was built about 500 ft upstream of the location shown by Plafker (1955), it appears that the dam is directly underlain mostly by unconsolidated glacial outwash deposits, though alluvial sediments may lie within the former Cooper Creek channel. The glacial outwash deposits consist mainly of angular to subrounded, poorly-sorted, gravel, cobbles, and boulders in a sand and silt matrix. A well-developed post-glacial podsolic soil profile (severely leached and highly acidic with a gray ashy appearance; extending immediately south of tundra regions of the Northern Hemisphere, characteristically capped with an abundant surface accumulation of organic matter) often develops on the exposed ground surface, and can mark the interface with younger alluvial sediments. This soil horizon is characterized by a bleached, 1- to 2-inch thick, gray or white horizon lying immediately beneath the surficial organic horizon, and above an iron-rich, reddish-brown horizon that may be up to 2.5 ft thick. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 4-3 Geotechnical Baseline Report – Final May 2012 Rock beneath Cooper Lake Dam is fine-grained, well-consolidated, dark gray, blue-black, or black slate with minor, thin (trace to 1-inch) lenses of greywacke of the Valdez Formation. Cleavage is imperfect and “the rock breaks into slabs with rough irregular surfaces (Plafker, 1955).” These slabs of slate are cut into angular pieces of 9 inches or smaller following closely- spaced cross-cutting joint planes. The slate is weathered mechanically to a depth of about 3 ft along the cleavage and joint planes. Cleavage and bedding strikes at between about north-south to north 10 degrees east and dips at between 85 degrees east and 85 degrees west (Plafker, 1955). Page 4-4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final This page is intentionally blank. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 5-1 Geotechnical Baseline Report – Final May 2012 5.0 GEOTECHNICAL PROPERTIES AND MATERIAL BASELINES This section describes the soil and rock units that will be encountered during construction and subsequently provides baselines for specific material properties for these units. The work will encounter both rock and soil rock units. Rock units at the site consist of either intact slightly weathered to fresh slate, or disturbed, intensely fractured slate of the Valdez Formation. Soil units will consist of glacial till, glacial outwash, and terminal moraine deposits. Each of the rock and soil units are identified in Table 5-1 below, and baselines for each of the units are presented in the following paragraphs. Table 5-1 – Rock and Soil Units Unit Description Ia Intact Slate (Valdez Formation) Ib Disturbed or Intensely Fractured (Valdez Formation) II Glacial Till III Glacial Outwash IV Terminal Moraine Deposits 5.1 UNIT I: SLATE OF THE VALDEZ FORMATION 5.1.1 Material Description and Characteristics All rock found within the Project area is part of the Valdez Formation. Within the project area, the Valdez Formation is chiefly comprised of thinly bedded slate. On rare occasion the slate is interbedded with fine grained greywacke. With respect to the site the rocks of the Valdez Formation can be subdivided into two primary categories, intact slate (Unit Ia) and disturbed or intensely fractured slate (Unit Ib). The intact slate of Unit Ia is dark grey, fine grained, fresh to slightly weathered and hard. Discontinuities are typically clean to very thinly filled, and are slightly rough. Discontinuity spacing ranges from 0.3 to 1 ft in rock cores, however larger spacing of up to approximately 5 ft has been observed in existing rock cuts. Discontinuities within Unit Ia are relatively consistent across the Project area. Where drilled, Unit Ia commonly has an average rock quality designation (RQD) that ranges from about 50 to 100 percent where fresh and undisturbed; however, discrete zones with RQDs of less than 50 were observed occasionally. The best exposure of the slate of Unit Ia is in the existing spillway of the Cooper Lake Dam. Unsupported cuts of up to about 50 ft high are present at angles ranging between 1H:1V and 0.3H:1V. While smaller block failures on the order of 1/3 to ½ cubic yards have occurred within the spillway cutslope, most rock fall from this slope is on the order of less than three to six inches in diameter. The cut slope stability is structurally controlled along a bedding plane and a prominent joint orientation. Similar to the intact slate of Unit Ia, the disturbed or intensely fractured slate of Unit Ib is dark grey, fine grained, slightly weathered, and moderately hard; however, Unit Ib is considerably more fractured or is displaced. Discontinuities within Unit Ib are very inconsistent and can vary Page 5-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final over as little as a few feet. Unit Ib has a discontinuity spacing that is generally between 1 and 3 inches and an RQD that is typically less than 30 percent (commonly 0 percent). The disturbed slate comprising Unit Ib is visible at several locations along the banks of Stetson Creek and the cuts of the dam access road. At approximate diversion access STA 5+00, Unit Ib outcrop in slopes dipping at slopes of up to 0.4 H:1V short distances, while slopes on the order of 0.6H:1V to 0.8H:1V are more common. A photograph of this outcrop is presented in Appendix IV. Discontinuity spacing in this area is typically on the order of 2 inches. Unit Ib also outcrops in some cut slopes of the Cooper Lake Dam access road. At these locations the contact between Unit Ia and Unit Ib is visible. Unconfined strength testing has been conducted on four Unit Ia rock core samples. No Unit Ib samples were tested given the intensely fractured nature of Unit Ib; however the intact rock strength is expected to be consistent with that of Unit Ia. The number of unconfined compressive tests is considered to be statistically insignificant; the test results show a significant amount of scatter, ranging from 13,087 to 987 psi. The lowest unconfined strength was a clear outlier that is believed to have failed along a pre-existing fracture that was not visible prior to testing. With the outlying sample excluded, the average unconfined strength was 9,487 psi. It was noted that each of the tested samples failed along the orientation of the bedding planes. Accordingly, rock mass strength is expected to vary significantly with bedding and discontinuity orientation. The slope mass rating (SMRs) for cuts in Unit Ia is expected to have and average value of 55 in areas of controlled blasting near the diversion dam and the existing spillway. An average value of SMR of 44 is anticipated in areas where blasting is less restricted. This range of SMR is described as “Normal” (Singh and Goel, 2011). Systematic rock anchors will be required as indicated on the project drawings. Additional rock anchors will be required to secure individual unstable blocks. The average SMR of Unit Ib is expected to be approximately 32, which is classified as “bad” (Singh and Goel, 2011). As with Unit Ia, Unit Ib will also require systematic rock anchors with additional rock anchors to secure individually unstable blocks. Uncased drains will be required in all permanent rock slopes surrounding the diversion dam and rock cut slopes. Soil Units II, III, and IV will be sloped back as indicated on the project drawings. 5.1.2 Material Baselines The material baselines for Valdez Formation are defined below: Structure Unit Ia Bedding Orientation: Dip Direction/Dip (95 Percent Confidence Interval) Diversion Dam 283 / 84 (+/- 38) Degrees Construction Access and 283 / 84 (+/- 38) Degrees Pipeline 0+00 to 35+00 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 5-3 Geotechnical Baseline Report – Final May 2012 Construction Access and 80 /76 (+/- 10) Degrees Pipeline 35+01 to 118+65 Siphon Outlet Works 80 / 76 (+/- 10) Degrees Discontinuities Orientation: Dip Direction/Dip (95 Percent Confidence Interval) Diversion Dam 146 / 57 (+/- 15) Degrees Construction Access and 146 / 57 (+/- 15) Degrees Pipeline 0+00 to 35+00 Construction Access and 136 / 52 (+/- 20) Degrees Pipeline 35+01 to 118+65 Siphon Outlet Works 136 / 52 (+/- 20) Degrees Unit Ib The bedding and joint orientations vary significantly by location. For baseline purposes, these orientations are considered randomly oriented. Baseline Intact Rock Properties (Rock Material Without Discontinuities) Unit Ia Unit Weight: 172 pcf Unconfined Strength: 9,500 psi Young’s Modulus: 12.6 x 106 psi Unit Ib Unit Weight: 172 pcf Unconfined Strength: 9,500 psi Young’s Modulus: 12.6 x 106 psi Baseline Rock Mass Measurements Unit Ia RQDave 65 percent Seismic Primary Wave Velocity: 12,000 fps Unit Ib RQDave 10 percent Seismic Primary Wave Velocity: 8,500 fps Page 5-4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final 5.2 UNIT II: GLACIAL TILL 5.2.1 Material Description and Characteristics Glacial till, sometimes referred to as unstratified glacial drift, consists of material that is transported by glaciers. This type of material is generally well graded to gap-graded with large variations in particle sizes ranging from clay to boulders. The parent material of the glacial till is rock from the Valdez Formation (Units Ia and Ib). Accordingly, particles forming the glacial till deposits are primarily composed of slightly metamorphosed slate and fine grained greywacke. While no petrographic testing has been conducted on this soil unit, glacial till deposits are expected to have the same mineralogical constituents that were identified in a petrographic analysis conducted on a glacial outwash sample. These constituents are discussed in Section 5.3. Glacial till at the Cooper Lake site consists of dense to very dense, well graded to gap graded mixtures of fine and coarse grained soil. Coarse grained soils are general rounded to sub- angular. Maximum particle sizes of glacial till soils may exceed 4 ft in diameter. Laboratory testing and observations of the glacial till indicate that the fines content ranges from 8 to 20 percent. Glacial till is distinguished from glacial outwash by the lack of particle sorting or stratification, higher relative density, and higher fines content. 5.2.2 Material Baselines The material baselines for glacial till deposits are defined below: Dry Unit Weight: 120 pcf Moisture Content: 8 to 15 percent Fines Content: 5 to 20 percent Seismic Primary Wave Velocity 4,500 fps 5.3 UNIT III: GLACIAL OUTWASH DEPOSITS 5.3.1 Material Description and Characteristics Glacial outwash deposits at the site are comprised of fluvial and colluvial deposited soils of glacial origin. The source of the glacial soils is predominately slightly metamorphosed (greenschist facies) trubidite deposits of the Valdez Formation (Units Ia and Ib). Locally the Valdez Formation is slate with minor amounts of fine grained graywacke. A petrographic analysis of one sample indicates the glacial outwash has a mineral composition of 50 percent calcite, 35 percent quartz, 6 percent opaques, and 5 percent or less of other minor minerals such as feldspar, mica, sphene and chlorite. Glacial outwash deposits consist primarily of consist sub-rounded to sub-angular, poorly graded gravel with sand and cobbles to sand with gravel and cobbles. Occasional boulders up to four feet in diameter were observed in some outwash deposits. Observation and laboratory test results indicate that the fines contents of glacial outwash deposits range from 1 to 10 percent. Large fluctuations of fines content were observed with both depth and location. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 5-5 Geotechnical Baseline Report – Final May 2012 5.3.2 Material Baselines The material baselines for glacial outwash deposits are defined below: Dry Unit Weight: 115 pcf Moisture Content: 5 to 12 percent Fines Content: 0 to 10 percent Seismic Primary Wave Velocity 2,000 fps 5.4 UNIT IV: TERMINAL MORAINE DEPOSITS 5.4.1 Material Description and Characteristics Terminal moraine deposits are glacial soil formed at the edge or end of a glacier. With respect to the Cooper Lake project, this deposit marks the terminus of a glacier that was once present in the current location of Cooper Lake. Fine grained fluvial deposits have formed at this location. While these deposits may be more accurately described as a lodgement till, the title of terminal moraine will be used to maintain consistent nomenclature with previous reports. Terminal moraine deposits at the site vary significantly with location and depth. They are generally characterized by their high fines content, typically containing between 15 and 100 percent by weight passing the US Standard No. 200 sieve. Coarse gained components of the terminal moraine deposits range from sand to gravel, but may contain cobbles or occasional boulders. This fine grained deposit is regularly interbedded with layers of coarse grained soil. While groundwater conditions in terminal moraine deposits were not observed due to the exploration methods used, coarse grained soil interbedded in this type of deposit are known to be potential seepage conduits. 5.4.2 Material Baselines The material baselines for terminal moraine deposits are defined below: Dry Unit Weight: 92 pcf Moisture Content: 7 to 30 percent Fines Content: 15 to 100 percent Page 5-6 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final This page is intentionally blank. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-1 Geotechnical Baseline Report – Final May 2012 6.0 BASELINES FOR PROJECT IMPROVEMENTS 6.1 DIVERSION DAM 6.1.1 Diversion Dam Baseline Conditions The baselines presented for the diversion dam are predicated on the following assumptions: Rock excavations will be conducted using controlled drill and blast methods or hydraulic rock breakers. Permanent cut slope excavations will be conducted in a top down manner installing slope support measures as the excavation progresses. Excavations will be made to the line and grade shown on the project drawings. Groundwater control and stream water diversion will be conducted in accordance with the project specifications. Temporary supports are designed and installed by the contractor. Permanent rock cut supports include prescriptive passive rock anchors and at additional locations where determined necessary as indicated in the project drawings and specifications. Conditions encountered during field investigations are representative of overall site conditions. 6.1.2 Geologic Units The excavation for the diversion dam will be primarily within Units Ia and Ib. Portions of the diversion dam will be covered with colluvial soil consistent with the soils of Unit III. The colluvial soil is present primarily at the upper slopes of the excavation. The baseline properties for these materials are presented in Section 5 of this report. 6.1.3 Geologic Interpretation 6.1.3.1 Surface Conditions Surface conditions at the diversion dam are characterized by a gorge with steep slopes. The left abutment slopes downward to the southeast at a rate of 1.3 horizontal to 1 vertical (1.3H:1V), while the right abutment slopes downward to the northwest at a rate of approximately 0.8H:1V. The average grade of Stetson Creek at this location is 6 percent, with localized portions exceeding 20 percent over short distances. Exposures of shallow bedrock (Units Ia and Ib) are visible within the stream bottom and along lower portions of the slopes. Upper slopes appear to be mantled with a thin layer of colluvial soil (Unit III). Vegetation at the diversion dam site consists primarily of alder and tall grass. 6.1.3.2 Subsurface Conditions Subsurface conditions at the proposed diversion dam were evaluated by conducting two rock core explorations (B-1-2010 and B-2-2010) and two seismic refraction surveys (SL-10-1-1 and SL-10-1-2). The locations of these explorations are presented on Figures 3 and 4. Shallow rock is exposed in the streambed of Stetson Creek and in the lower elevations of each abutment. Based on observation, the rock in the base of the stream consists of moderately Page 6-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final weathered, gray slate consistent with Unit Ib. Within the stream channel the rock is expected to be underlain by undisturbed rock (Unit Ia) at a depth of about 2 feet. Explorations B-1-2010 and SL-10-1-2 were conducted on the slope of the left abutment. Explorations show that the fresh to slightly weathered slate (Unit Ia) is overlain by a layer of displaced slate (Unit Ib) that is approximately 13 ft thick. RQD’s of 0 were recorded in this upper displaced rock layer. It is believed that this displaced rock is the result of a combination of factors including stress relief, freeze-thaw cycles, undercutting from Stetson Creek and slope creep. Intact, fresh to slightly weathered, moderately hard slate (Unit Ia) was encountered below the displaced rock to the depths explored of 40.4 ft. Above the left abutment, the displaced rock is mantled by a thin layer of glacial outwash (Unit III) overlain by topsoil. Thicker layers of outwash of approximately 5 feet are anticipated above an elevation of 1455 on the left abutment. Explorations B-2-2010 and SL-10-1-1 were conducted right abutment on the slope. Relatively low RQD’s (24) were encountered in the upper 5 ft of B-2-2010 indicating the presence of Unit Ib rock. This disturbance is likely the result of both stress relief and freeze-thaw cycles. The disturbed rock was underlain by intact, fresh to slightly weathered, moderately hard slate (Unit Ia) from 13 ft to the depth explored of 30.0 ft. The left abutment is overlain by an approximate 1-ft thick layer of glacial outwash (Unit III) between the elevations of 1431 and 1462. Thicker layers, on the order of 5 feet of Unit III are present above and elevation of 1462. The following Table 6-1 presents the baseline subsurface conditions for the Stetson Creek Diversion Dam: Table 6-1 – Stetson Creek Diversion Dam Subsurface Baseline Location Depth (ft)Rock or Soil Unit Left Abutment Above El 1455 ft 0 to 5 III 5 to 10 Ib 10+ Ia Left Abutment Below El 1455 ft 0 to 2 III 2 to 13 Ib 13+ Ia Stream Channel 0 to 2 Ib 2+ Ia Right Abutment Below El 1465 ft 0 to 1 III 1 to 5 Ib 5+ Ia Right Abutment Above El 1465 ft 0 to 5 III 5 to 10 Ib 10+ Ia Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-3 Geotechnical Baseline Report – Final May 2012 6.2 DIVERSION PIPELINE AND CONSTRUCTION ACCESS 6.2.1 Diversion Pipeline and Construction Access Baseline Conditions The baselines presented for the diversion pipeline and construction access are based on the following assumptions: Excavations of rock Unit Ia will be conducted using either drill and blast methods or hydraulic rock breakers. Controlled blasting will be used between road STA 92+40 and 97+00. Cut slope excavations will be conducted in a top down manner installing slope support measures as the excavation progresses. Permanent rock cut supports in Unit Ia and Ib include prescribed passive rock anchors and supplemental rock anchors where determined necessary as indicated on the project drawings and in the specifications. Permanent soil cut slopes steeper than 2H:1V require support as indicated on the drawings. Permanent fill slopes will be constructed at 2H:1V or flatter, with the exception of approved rockfill slopes, which will be constructed at a maximum slope of 1.5H:1V. Soil cut slopes in Units II and III that are steeper than 2H:1V will be reinforced with driven soil nails. Approximately 15 percent of soilnails shorter than 30 ft long will encounter refusal and will require pre-drilling of soilnails. All soil nails 30 ft or longer will require pre-drilling. Groundwater control measures will be designed by the contractor and conducted in accordance with the project specifications and as indicated on the Drawings. Temporary supports are designed and installed by the contractor. Conditions encountered during field investigations are representative of overall site conditions. 6.2.2 Geologic Units The material excavated for the construction of the diversion pipeline and construction access will vary with location and depth between Valdez Formation rock (units Ia and Ib), glacial till deposits (unit II), and glacial outwash deposits (Unit III). The baseline properties for these materials are presented in Section 5 of this report. 6.2.3 Geologic Interpretation 6.2.3.1 Surface Conditions Surface conditions along the diversion pipeline and construction access can be divided into two reaches (Stetson Creek and Cooper Creek) separated by the ridgeline between the two drainage basins at approximate road STA 35+00. The Stetson Creek reach of the diversion pipeline and construction access, located between road STA 0+00 and 35+00, is characterized by a gorge that is on the order of 200 ft deep. The southern slopes of the gorge generally dip downward toward Stetson Creek at an average rate of 1.4H:1V to the northwest. Slopes located immediately adjacent to the stream are commonly steeper than 1H:1V. Rock outcrops of Units Ia and Ib can be seen within Stetson Creek and Page 6-4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final along many of the lower portions of the adjacent slopes. The upper slopes of the gorge are typically mantled by glacial outwash deposits (Unit III). Vegetation along the Stetson Creek reach of the alignment is dominated by areas that alternate between alders with tall grass and stands of coniferous trees. The second reach of the diversion pipeline and construction access is identified as the Cooper Creek reach. This portion of the alignment extends from road STA 35+00 to the diversion outfall at Cooper Lake. The pipeline and construction access alignment within the Cooper Creek reach transect moderate to flat slopes in comparison to the Stetson Creek reach. Slopes within the Cooper Creek reach generally dip downward to the northeast at rates ranging from 3H:1V to 6H:1V, with steeper slopes in localized areas. The ground surface within the Cooper Creek reach is generally covered by a thick layer of duff, with occasional rock outcroppings. Vegetation along the Cooper Creek reach is similar to the Stetson Creek reach, varying between areas of alder with tall grass and stands of coniferous trees. 6.2.3.2 Subsurface Conditions Stetson Creek Reach The Stetson Creek reach of the diversion pipeline and access road was explored by conducting a series of three seismic refraction surveys (SL10-2, SL10-3, and SL10-5) and by conducting a geologic reconnaissance. The locations of the seismic refraction surveys are depicted on Figures 2, and 4 through 7. In general, the seismic refraction surveys along the Stetson Creek reach of the diversion pipeline and access indicate the presence of glacial outwash deposits (Unit III) overlying more dense glacial till deposits (Unit II). The Unit III deposits generally extend 3 to 10 ft below grade. Unit II deposits are expected to underlie Unit III deposits between road STA 12+40 and 37+00. Seismic refraction data indicates that depth of Unit II deposits along the Stetson Creek reach varies significantly from 0 to in excess of 60 ft. Rock outcrops of Units Ia and Ib were observed along portions of the Stetson Creek reach. The outcrops are most prevalent between road STA 0+00 and 12+40. Velocities consistent with Unit Ib were noted in SL10-2 at depths of about 10 ft; however based on exposures of Unit Ia in the adjacent stream, it is expected that Unit Ib is relatively thin at this location. Data from SL10-5 indicate that intact rock (Unit Ia) is present at depths of up to 60 ft. Seismic refraction velocities consistent with rock were not observed in SL10-3. Landforms showing signs of previous slope movements are common within the Stetson Creek reach of the alignment and throughout much of the Kenai Peninsula. These areas included localized sloughing, hummocky terrain, pistol-butted trees, and historical headscarp features. One area along the diversion pipeline alignment was observed within the Stetson Creek reach between approximate road STA 3+10 and 5+20. Trench drains will be installed at the locations indicated on the project drawings to help stabilize slopes in these areas. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-5 Geotechnical Baseline Report – Final May 2012 Cooper Creek Reach The Cooper Creek reach of the diversion pipeline and construction access was explored by conducting seven seismic refraction surveys (SL-3 through SL-9) and a geologic reconnaissance of the alignment (Figure 2, 3,9, 11, and 13). Since the time of these seismic refraction surveys, the alignment of the diversion pipeline and construction access has been modified. It is important to note that the seismic lines were conducted at locations that represent a previous pipeline alignment. The distance between the two pipeline alignments vary by a distance of up to approximately 450 ft within the Cooper Creek reach. In general, seismic refraction surveys along the previous alignment of the Cooper Creek reach of the diversion pipeline and construction access indicate the presence of shallow bedrock mantled by a thin layer of glacial outwash (Unit III) at most locations. In some locations the glacial outwash deposits are underlain by glacial till deposits (Unit II). The average depth of the soil deposits (Units II and III) is expected to vary with location along the alignment. Geotechnical data indicate that the soil deposits generally consists of 2 to 6 ft of Unit III deposits underlain by Unit II deposits; however in some areas of shallow rock, Unit II deposits may be absent as indicated by SL-4, SL-5, and SL-7. The geotechnical baseline for specific locations along the diversion pipeline, access road, and in- line vaults is presented in Table 6-2. Table 6-2 – Diversion Access and Pipeline Subsurface Baseline Diversion Access STA Depth (ft)Rock or Soil Unit Water Depth (ft) 0+00 to 1+75 0 to 2 Ib 12+ Ia 1+75 to 3+10 0 to 3 Ib 0 (at or near the ground surface)3+ Ia 3+10 to 6+40 0 to 9 III 49 to 11 Ib 11+ Ia 6+40 to 12+40 0 to 10 Ib 1510+ Ia 12+40 to 20+00 0 to 6 III 206 to 35 Ib 35+ Ia 20+00 to 35+00 0 to 9 III 159 to 38 II 38+ Ia 35+00 to 41+00 0 to 2 III 152 to 6 Ib 6 + Ia 41+00 to 46+00 0 to 4 III 54 to 16 II 16+ Ia Page 6-6 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final Table 6-2 – Diversion Access and Pipeline Subsurface Baseline Diversion Access STA Depth (ft)Rock or Soil Unit Water Depth (ft) 44+00 to 45+00 0 to 4 III 14 to 16 II 16+ Ia 44+00 to 45+00 0 to 4 III 54 to 16 II 16+ Ia 46+00 to 48+50 0 to 3 III 103 to 6 II 6+ Ia 48+50 to 50+00 0 to 4 III 14 to 12 II 12+ Ia 50+00 to 55+00 0 to 6 III 86+ Ia 55+00 to 56+50 0 to 6 III 16+ Ia 56+50 to 67+50 0 to 6 III 86+ Ia 67+50 to 70+50 0 to 3 III 53 to 10 II 10+ Ia 70+50 to 72+00 0 to 6 III 56+ Ia 72+00 to 73+00 0 to 6 III 16+ Ia 73+00 to 75+00 0 to 6 III 56+ Ia 75+00 to 87+50 0 to 3 III 53 to 10 II 10+ Ia 85+20 to 86+20 0 to 3 III 13 to 10 II 10+ Ia 86+20 to 87+50 0 to 3 III 53 to 10 II 10+ Ia 87+50 to 91+50 0 to 5 III 105+ Ia 91+50 to 97+00 0 to 2 III 152 to 10 Ia 97+00 to 98+50 0 to 5 III 105 to 10 Ib Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-7 Geotechnical Baseline Report – Final May 2012 Table 6-2 – Diversion Access and Pipeline Subsurface Baseline Diversion Access STA Depth (ft)Rock or Soil Unit Water Depth (ft) 97+00 to 98+50 10+ Ia 98+50 to 111+50 0 to 25 III 525 Ib 111+50 to 118+65 0 to 15 III 015+ Ia 6.3 SIPHON OUTLET WORKS 6.3.1 Siphon Outlet Works Baseline Conditions The baselines presented for the siphon outlet works are based on the following assumptions: Rock excavations will be conducted using controlled drill and blast methods or hydraulic breakers. Construction will be staged such that the concrete plug is constructed prior to the excavation of the upstream portion of the siphon pipeline so that the reservoir maintains watertight at all times during construction. Temporary supports are designed and installed by the contractor. Permanent soil cut slopes will be limited to 2H:1V in glacial outwash deposits and 2.5H:1V in terminal moraine deposits. Groundwater control and dewatering systems will be designed by the contractor. The surface of Cooper Lake will be maintained at or below EL 1162 ft during the anticipated construction season (between May 15 and October 15). Conditions encountered during field investigations are representative of overall site conditions. 6.3.2 Geologic Units The excavations associated with the siphon outlet works will include cuts in the Valdez Formation rock (Units Ia and Ib), glacial outwash deposits (Unit III), and terminal moraine deposits (Unit IV). The baseline properties for these materials are presented in Section 5 of this report. 6.3.3 Geologic Interpretation 6.3.3.1 Surface Conditions The siphon outlet facility is located within the Cooper Lake Dam spillway. The existing spillway is located at the left abutment of Cooper Lake Dam. The spillway is approximately 50 ft wide and nearly 600 ft long. Water flow through the spillway is controlled by a 3-foot high concrete weir located in-line with the axis of Cooper Lake Dam. Vegetation within the spillway is sparse and consists primarily of moss, grass, and small alders. The spillway discharges into a heavily vegetated channel with alder and stands of deciduous and coniferous trees. The end of the spillway is characterized by a near vertical rock wall with a drop of approximately 10 ft into the vegetated channel. This feature can be noted near siphon Page 6-8 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final outlet STA 13+50 (Figure 13). The vegetated channel downstream of the spillway extends approximately 250 ft where it intersects the natural channel of Cooper Creek. 6.3.3.2 Subsurface Conditions Subsurface conditions at the siphon outlet works were evaluated by conducting four borings (B- 3-2010 through B-6-2010) and a seismic refraction survey (SL-2). Boring B-3-2010 was conducted near the siphon intake, borings B-4-2010 and B-5-2010 were conducted within the existing spillway, and boring B-6-2010 was conducted within the channel downstream of the existing spillway. In addition to subsurface borings, a seismic refraction survey (SL-2) was conducted within the existing spillway during the 2009 exploration program. The subsurface characterization of the spillway area also considered information from previous borings conducted near this location (NPC, 1955). The locations of these explorations are presented on Figure 13. Subsurface conditions upstream of the existing spillway and near the siphon intake consist of glacial outwash deposits (Unit III). The thickness of the Unit III deposits are expected to range from 0, within the rock spillway, to in excess of 30 ft below Cooper Lake. At the location of B- 3-2010, Unit III deposits were observed to extend to a depth of 28 ft were they are underlain by highly fractured rock of the Valdez Formation (Unit Ib). Intact rock (Unit Ia) is visible at the surface of the existing spillway between approximate siphon outlet STA 7+00 and 13+50. Borings B-4-2010 and B-5-2010 encountered fresh to moderately weathered and moderately hard rock from depths of 0 to 30.0 ft in each hole. One seismic refraction survey conducted at this location indicates the underlying rock has an interpreted primary seismic velocity of 15,000 fps, which is consistent with sound rock. The downstream edge of the rock surface is marked by a pronounced drop off at approximate siphon outlet STA 13+50. Disturbed rock (Unit Ib) was encountered upstream of the spillway in boring B-3-2010. The rock at this location exhibited RQD’s ranging from 0 to 33 percent. This occurrence indicates that a layer of disturbed rock (Unit Ib) is likely present where it has not otherwise been removed during the excavation of the existing spillway. Terminal moraine deposits (Unit IV) are present downstream of the existing spillway between siphon outlet STA 13+50 and the 22+05. Boring B-6-2010 was conducted near STA 15+50. The subsurface conditions at this location consist of medium dense sand with silt and gravel between the ground surface and a depth of 8.5 ft that is consistent with Unit III. The sand layer is underlain by very stiff silt and lean clay with occasional 1- to 3- inch thick gravel interbeds to a depth of 43 ft (Unit IV). The very stiff layer of silt and lean clay is underlain by very dense to dense sands and gravels to the depth explored of 50.5 ft. The siphon outlet works will include a number of ancillary facilities including in-line facilities, a diversion instrumentation building, and a siphon instrumentation building. Inline facilities will include a siphon inlet structure, a siphon fill and vent manhole, a concrete plug, a siphon instrumentation vault, and a siphon outlet structure. Subsurface conditions for inline facilities are expected to be consistent with the subsurface conditions for the siphon outlet pipeline. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-9 Geotechnical Baseline Report – Final May 2012 Subsurface conditions at the location of the diversion pipeline instrumentation building are expected to consist of approximately 2 ft of glacial outwash soil (Unit III) underlain by intact rock (Unit Ia). The siphon instrumentation building is expected to be underlain by as much as 25 ft of dense fill consistent with the properties of glacial outwash (Unit III). Specific subsurface baseline conditions for the siphon outlet works and in-line ancillary facilities are presented in Table 6-3. Subsurface baseline conditions for the diversion pipeline instrumentation building are presented in Table 6-4. Subsurface baseline conditions for the siphon instrumentation building are presented in Table 6-5. Table 6-3 – Siphon Outlet Works and In-Line Facilities Subsurface Baseline Siphon Outlet STA Depth (ft)Rock or Soil Unit Groundwater Elevation (ft) 0+00 to 6+00 0 to 28 III 117528 to 33 Ib 33+ Ia 6+00 to 6+25 0 to 10 III 117510 to 15 Ib 15+ Ia 6+25 to 6+70 0 to 5 III 11755 to 8 Ib 8+ Ia 6+70 to 13+50 0+ Ia 1170 13+50 to 15+90 0 to 8 III 11688+ IV 15+90 to 17+00 0 to 4 III 11664+ IV 17+00 to 22+95 0 to 2 III 11602+ IV 19+00 to 21+00 0 to 2 III 11562+ IV 19+00 to 21+00 0 to 2 III 11542+ IV Table 6-4 – Diversion Pipeline Instrumentation Building Subsurface Baseline Depth (ft)Rock or Soil Unit Groundwater Elevation (ft) 0 to 2 III 11752+ Ia Table 6-5 – Siphon Instrumentation Building Subsurface Baseline Depth (ft)Rock or Soil Unit Groundwater Elevation (ft) 0 to 30 III 116830+ IV Page 6-10 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final 6.4 BORROW AREA 6.4.1 Siphon Outlet Works Baseline Conditions The baselines presented for the borrow area are predicated on the following assumptions: Temporary supports are designed and installed by the contractor. Permanent soil cut and fill slopes will be limited to 2H:1V in glacial outwash and glacial till deposits. Groundwater control and dewatering systems will be designed by the contractor. The surface of Cooper Lake will be maintained at or below elevation 1162 ft during construction during the anticipated construction season (May 15 through October 15). Conditions encountered during field investigations are representative of overall site conditions. 6.4.2 Geologic Units The excavations in the borrow area will encounter glacial outwash (Unit III) and glacial till (Unit II) deposits. The baseline properties for these materials are presented in Section 5 of this report. 6.4.3 Geologic Interpretation 6.4.3.1 Surface Conditions The right abutment borrow source is located upstream of Cooper Lake Dam’s right abutment (Figures 2 and 3). The borrow area was initially developed during the construction of the dam. It is believed that this material was used for the outer shell of the existing dam. The surface of the western portion of the right abutment borrow source is relatively flat, ranging in elevation from about 1182 to 1188. This portion of the borrow area is sparsely vegetated with grasses and occasional brush. The eastern portion of the right abutment borrow source ranges in elevation from approximately 1188 to 1234, and is sloped to the west at an average rate of 4H:1V. The eastern portion of the borrow area is densely vegetated with grass, brush and deciduous trees. 6.4.3.2 Subsurface Conditions The right abutment borrow source was explored by excavating Test Pits TP-4 through TP-7 and conducting seismic refraction survey SL-1. The near surface soil at TP-4, TP-5, and TP-6 consists of glacial outwash deposits (Unit III). These glacial outwash deposits are comprised primarily of dense, poorly-graded sand with gravels, cobbles and boulders, and well-graded gravel with sand and boulders. The maximum boulder size encountered at this location was 14 inches in diameter. Glacial outwash deposits extend to depths of 10 and 11 ft in TP-6 and TP-7, respectively, and were present throughout the entire depths of TP-4 and TP-5. The glacial outwash soil is overlain by a 2.5-foot thick layer of organic silt at the location of TP-7. The top of the glacial outwash deposits in the right abutment borrow area are underlain by glacial till deposits (Unit II) consisting of dense to very dense silty sand with varying amounts of gravel Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 6-11 Geotechnical Baseline Report – Final May 2012 in explorations TP-6 and TP-7. The glacial till deposit is present at depths of 10 and 11 ft in TP- 6 and TP-7, respectively. Glacial till is present to the terminal depth of both these test pits. The baseline subsurface conditions for the right abutment borrow area are presented in Table 6- 6. Table 6-6 – Borrow Area Subsurface Baseline Area Elevation Range (ft)Rock or Soil Unit Groundwater Elevation (ft) Areas with Existing Surface Elevation of less than 1190 ft Above 1180 III 11821180 to 1130 II Below 1130 Ia Areas with Existing Surface Elevation Between 1190 ft and 1200 ft Above 1180 III 11901180 to 1130 II Below 1130 Ia Areas With Existing Surface Elevation Greater Than 1200 ft Above 1180 III 1200 1180 to 1130 II Below 1130 Ia Page 6-12 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final This page is intentionally blank. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 7-1 Geotechnical Baseline Report – Final May 2012 7.0 REFERENCES Ellsworth, C.E., and Davenport, R.W, 1915. Waterpower Reconnaissance in South Central Alaska. USGS Water Supply Paper 372. Federal Energy Regulatory Commission (FERC), 2006. Environmental Assessment, Cooper Lake Hydroelectric Project, Alaska (Project No. 2170-029). FERC, 2007. Letter to Chugach Electric Association: Order on Offer of Settlement and Issuing New License, Project No. 2170-029. HDR Alaska, Inc. (HDR), 1998. Cooper Lake Hydroelectric Project, Part 12 Safety Inspection Report (Seventh Five-Year Review), FERC Project 2170. September. HDR, 2001. Cooper lake Hydro Project Supplement to 1988 Part 12 Safety Inspection Report. May 18. HDR, 2005. Proposed Stetson Creek Diversion, 2005 Studies Technical Memoranda, Cooper Lake Project (FERC No. 2170). August. HDR and Northern Ecological Services (HDR and NES), 2004. Draft Interim Report: Cooper Creek Instream Flow Study and Preliminary Evaluation of Potential Aquatic Habitat Benefits, Cooper Lake Project (FERC No. 2170). August. Inter-Fluve, Inc., 2004. Final Report, Cooper Creek Sediment and Geomorphology Investigation, Cooper Lake Project (FERC No. 2170). June. International Engineering Company, Inc. (IEC), 1983. Cooper Lake Hydroelectric Project, FERC No. 2170, Kenai Peninsula, Alaska, Periodic Safety Inspection Report. August 5. Jones, Fred O. 1965. Inspection of Cooper Lake Hydroelectric Project, Kenai Peninsula, Alaska. August 1. LaCroix and Horn, 1973. Direct Determination and Indirect Evaluation of Relative Density and Its Use on Earthwork Construction Projects: in Evaluation of Relative Density and Its Role in Geotechnical Projects Involving Cohesionless Soils.ASTM Special Technical Publication 523, p. 251-280. MWH, 2003. Cooper Lake Hydroelectric Project Part 12 Safety Inspection Report, Eighth Five- Year Review, FERC Project No. 2170, October. MWH, 2004. Cooper Lake Project, FERC No. 2170, Potential Cooper Creek Protection, Mitigation, and Enhancement Measures, DRAFT. August. MWH, 2008. Cooper Lake Hydroelectric Project Part 12 Safety Inspection Report, Ninth Five- Year Review, FERC Project No. 2170.August. Page 7-2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final Nelson, Steven W., Dumoulin, J.A., and Miller, Marti L., 1985. Geologic Map of the Chugach National Forest, Alaska.USGS MF-1645-B. North Pacific Consultants (NPC), 1955. Definite Project Report on Cooper Lake Hydroelectric Project, Kenai Peninsula, Alaska. December 29. NPC, 1958. Geology of the Cooper Lake Tunnel Site cooper Lake Hydroelectric Project, Kenai Peninsula, Alaska, Information for Bidders. August 28. NPC, 1958b. Cooper Lake Project Alaska 8 “H” Chugach, Project Roads, Report on Construction Materials. September 2. NPC, 1959. Cooper Lake Project, F.P.C. License No. 2170, R.E.A. Project: Alaska 8H Chugach, Design Report, Cooper Lake Dam. March. Plafker, George, 1955. Geologic Investigations of Proposed Power Sites at Cooper, Grant, Ptarmigan and Crescent Lakes Alaska. Geology of Power Sites in Alaska, USGS Bulletin 1031-A. Singh and Goel, 2011. Engineering Rock Mass Classification – Tunneling, Foundations, and Landslides. Butterworth Heinemann, New York, NY. Stone & Webster, 1987. Cooper Lake Dam, Technical Specification for Spillway Enlargement and Parapet Wall Installation, Issued for Bid. May 23. Stone & Webster, 1988. Fifth Periodic Safety Inspection Report, Cooper Lake Hydroelectric Project, FERC Project No. 2170, Kenai Peninsula, Alaska. September 1. Stone & Webster, 1997. Cooper Lake Dam, Technical Specification for Spillway Enlargement and Parapet Wall Installation, Issued For Bid. May. U.S. Army Corps of Engineers (USACE), 1983. Engineering and Design, Rock Mass Classification Data Requirements for Rippability. Engineering Technical letter No. 1110- 2-282. June 30. U.S. Bureau of Reclamation (USBR), 1998. Engineering Geology Field Manual. Second Edition, volume 1. U.S. Department of Agriculture – Natural Resources Conservation Service (USDA-NRCS), 1994.National Engineering Handbook. Part 633, Chapter 26. U.S. Geologic Survey – National Earthquake Information Center (USGS-NEIC), 2010a. Recorded Earthquake Database (1973 to 2010). Queried December 27, 2010. USGS-NEIC, 2010b. Significant U.S. Earthquakes Database (1568-1989). Queried December 27, 2010. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 7-3 Geotechnical Baseline Report – Final May 2012 U.S. Society on Dams (USSD), 2007. Strength of Materials for Embankment dams.USSD Committee on Materials for Embankment Dams. Weaver, Kenneth D. and Bruce, Donald A., 2007. Dam Foundation Grouting: Revised and Expanded Edition. American Society of Civil Engineers, Reston, VA. Wilson, Frederic H. and Chad P. Hults (Compilers), 2007. (Draft) Geology of the Prince William Sound and Kenai Peninsula Region, Alaska. USGS. Page 7-4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final This page is intentionally blank. FIGURES APPENDIX I 2009 Geophysical Seismic Refraction Survey Program . Stetson Creek Diversion & Cooper Lake Dam Outlet Facilities Page 1 of 2 Geotechnical Baseline Report – Final – Appendix I May 2012 APPENDIX I 2009 GEOPHYSICAL SEISMIC REFRACTION SURVEY PROGRAM As part of the 2009 exploration program, MWH conducted nine geophysical seismic refraction surveys (SL-1 through SL-9). The surveys were conducted by Northwest Geophysical Associates of Corvallis, Oregon, between September 29 and October 2, 2009. Geophysical surveys were located in the field using Global Positioning System-based survey equipment with sub-meter accuracy. The survey locations are shown on figures within the text of this report. Details are provided in the report of geophysical services attached. Page 2 of 2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix I This page is intentionally blank. Northwest Geophysical Associates, Inc. 1600 SW Western Boulevard, Suite 200 PO Box 1063, Corvallis, OR 97339-1063 Phone: (541) 757-7231 FAX: (541) 757-7331 www.nga.com October 28, 2009 NGA Ref: 715 Paul D. Richards, PE Senior Geotechnical Engineer MWH Americas, Inc. 5100 SW Macadam Ave, No. 420 Portland, Oregon 97239 Final Report Geophysical Investigation Stetson Creek Diversion Project Kenai Peninsula Borough, Alaska Dear Mr. Richards: This letter report presents the results of the seismic refraction survey that Northwest Geophysical Associates, Inc. (NGA) performed for the Stetson Creek Diversion Project (Figure 1 – Site Map) near Cooper Lake, Kenai Peninsula Borough, Alaska. NGA was assisted in the field effort by Mr. Thomas Williams of Northland Geophysical PLLC. The Stetson Creek Diversion Project will include a diversion dam on Stetson Creek and pipeline from the diversion dam to Cooper Lake. The geophysical investigation was to aid MWH America’s geotechnical investigations of site conditions along the pipeline route, potential borrow locations at Cooper Lake, the Cooper Lake Dam, and the pipeline terminus at Cooper Lake. The objective of the investigation was to estimate depth-to-bedrock as well as to characterize overburden and bedrock materials with seismic velocities. A description of the seismic refraction method is attached (Attachment A). Interpreted results are described in this report and presented on Figures 2-10. Field Methodology Field work was performed along nine seismic lines during the period September 29, 2009 to October 2, 2009. The locations of the nine seismic lines (Lines SL-1 through SL-9) are shown on the Site Map (Figure 1). The seismic lines are numbered in the order they were run in the field, with SL-1 at the proposed borrow area near Cooper Lake Dam, SL- Geophysical Investigation Page 2 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 2 at the spillway next to Cooper Lake Dam, and SL-3 at the pipeline lake access location. Seismic lines 4-9 are along the pipeline alignment. The locations of the seismic lines were selected by Paul Richards of MWH. The seismic lines were established in the field using 300-foot tape measures. NGA mapped the positions of the line ends using a Trimble PRO XRS GPS, which has sub-meter accuracy. NGA measured relative elevations along each line using a transit level. The field investigation was performed using a 24-channel Geometrics Geode seismograph to record the data. A Betsy Seisgun was used as the primary seismic source, firing an 8 gauge shotgun blank (400 grains of black powder) with the muzzle 2-3 feet into the surface soils to generate a seismic wave at regular intervals along each seismic line, and also at some distance from both ends of each line. Where surface soils were shallow (Seismic Lines 1-3), a slide-hammer (30 kg weight) source was used to generate a seismic wave at regular intervals along each seismic line, and also at some distance from both ends of each line. Geophones were spaced at 10-foot intervals along each of the seismic lines. On Seismic Lines 1, 2, and 5-10 NGA used 24 geophone receivers spaced at 10 foot intervals, yielding line lengths of 230 feet. On Seismic Line 3 NGA used 14 geophone receivers spaced at 10 foot intervals, yielding a line length of 130 feet due to limited physical access (e.g. thick forest and lake water) on either end of the survey alignment. At Seismic Line 4 NGA used 22 geophone receivers spaced at 10 foot intervals, yielding a line length of 210 feet due to limited physical access (e.g. rock wall and thick forest) on either end of the survey alignment. Interpretation Results The results of the seismic survey are shown on the interpretation profiles (Figures 2-10). The profiles show the geophone locations along the ground surface, the interpreted depths/thicknesses of each layer, and interpreted velocities. The possible geologic units were identified based on the interpreted seismic velocities (in feet/second) and conversation with MWH engineer Paul Richards. Their interpreted velocity range (in feet per second), graphic pattern, and possible classification are indicated in the following table. Geophysical Investigation Page 3 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 TABLE 1 Seismic Stratigraphy GRAPHIC PATTERN LAYER DEISGNATION & SEISMIC VELOCITY POSSIBLE CLASSIFICATION (Feet/Second) Dot Fill V1 - 820 – 1,460 V1 - Unconsolidated soil and/or organic material. Angled Hatch V2 - 2,700 – 3,250 V2a – 4,900 – 6,850 V2 - More consolidated overburden and/or weathered material. V2a – Till and/or slide material. Solid Grey 8,500 – 16,000 Competent Rock (Phyllite – Slate, per conversation with MWH). Seismic Stratigraphy Interpretations Layer 1 – Organic and unconsolidated soil overburden Layer 1exhibits lower velocities ranging from 820 feet/second to 1,460 feet/second. We have interpreted this layer as organic and unconsolidated soil overburden. Layer 1 was observed on all nine seismic profile alignments with the exception of Seismic Line 2, at the dam spillway. Layer 1 thickness varied across the individual profile alignments, usually representing the upper 2-8 feet of the interpreted profile. Layer 2 –Consolidated overburden material Layer 2 displayed moderate velocities ranging from 2,700 feet/second to 3,200 feet/second. We have interpreted this layer as overburden material. Layer 2 was observed on Seismic Lines 3, 8, and 9. Layer 2 thicknesses varied greatly across the site and even across individual profiles, with layer thickness ranging from 10 to 25 feet Layer 2a –Till and/or Slide Material Layer 2a displayed moderate to high velocities ranging from 4,900 feet/second to 6,800 feet/second. We have interpreted this layer as till and/or slide material. Layer 2a was observed only on Seismic Lines 1 and 7. Where interpreted, Layer 2a thickness was substantial (20 feet or greater) and extended near the maximum depth of the interpreted seismic profiles. Geophysical Investigation Page 4 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 Layer 3 – Competent Rock The high velocities exhibited by Layer 3 ranged from 8,500feet/second to 16,000 feet/second. We have interpreted this layer as competent rock, likely correlated to the phyllite-slate material common throughout the site. Layer 3 was interpreted across eight of the nine profile alignments: Seismic Lines 1-6 and 8-9. Layer 3 was not observed on Seismic Line 7. The interpreted competent rock layer (Layer 3) has a range of high seismic velocities (8,500 – 16,000 ft/sec). These values likely correlate to the phyllite- slate material observed throughout the site, and are in the range of values for similar rock units observed elsewhere in the Chugach Formation. Profile Interpretations Seismic Line 1 The interpreted seismic velocity profile for Seismic Line 1, extending 230 linear feet, is displayed on Figure 2. Seismic Line 1 was run across a flat surface northeast of the existing dam at the northern end of Cooper Lake, a location being considered for material excavation and supply. A low velocity (1,100 feet/second) material, which we have interpreted as Layer 1, appears in the upper 5 feet of the profile alignment. The interface between Layer 1 and Layer 2a mirrors the generally flat surface topography. A zone of moderate velocity material (6,850 feet/second) was observed nearly to the maximum depth of investigation (approximately 50-60 feet). We have interpreted this moderate velocity zone as Layer 2a (till). As access was clear off the ends of this alignment, and data from near off end shot points indicated a possible third layer beneath the interpreted Layer 2a, NGA collected data from far off end shotgun shell energy sources. These additional data were taken at distances approximately 100 feet off either end of the spread, distances which were not possible on any of the other seismic alignments due to limiting physical surface features (e.g. rock walls, dense forest). Additional data from these far off end data points seems to indicate the presence of a third layer at depths of 45 feet and greater; however, at such interpretation depths and source distances off the end of the seismic receiver array, resolution of the third layer was limited. As a result of this limited resolution, NGA has indicated the Layer 2a-Layer 3 contact with a dashed interpreted contact line on Figure 2. The estimated representative velocity for velocity Layer 3 and dipping (from West to East) interface contact represent the best model available from the data that were collected. As the interface contact and velocity layer are near the depth limit of investigation with available energy sources, their actual depth, interface geometry, and material velocities may vary from the interpretations we have provided. Geophysical Investigation Page 5 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 Seismic Line 2 The interpreted seismic velocity section for Seismic Line 2, extending 230 linear feet, is displayed on Figure 3. Seismic Line 2 was run along the long axis of the spillway at the west end of the existing dam at the northern end of Cooper Lake. Interpretation of the seismic data indicates the presence of a single high velocity layer. We have interpreted this material as velocity Layer 3 (competent rock), and estimate a representative velocity of 15,000 feet per second. Seismic Line 3 The interpreted seismic velocity section for Seismic Line 3, extending 130 linear feet, is displayed on Figure 4. Seismic Line 3 was run at the site where the proposed pipeline outfall to Cooper Lake. The west end of the seismic alignment was bounded by dense forest, and the east end of the seismic alignment terminated near the edge of Cooper Lake, leaving only a 130 foot survey alignment. Interpretation of the seismic data indicates the presence of three velocity layers across the alignment which itself slopes significantly on its eastern half. Velocity Layer 1 (organic material and unconsolidated overburden) exhibited a low velocity (820 feet/second) and varied from 1-5 feet in thickness, generally mirroring the sloping topography. Velocity Layer 2 (consolidated overburden) exhibited a moderate velocity (2,400 feet/second) and layer thickness of approximately 20 feet. The upper limit of velocity Layer 2 tapers with the sloping topography on the east end of the profile while the lower limit of velocity Layer 2 trends gently downward from west to east between stations 0 and 60, and remains fairly flat from station 60 to station 130. The faster material (11,100 feet/second) interpreted below velocity Layer 2 to the maximum depth of detection we have interpreted as velocity Layer 3 (competent rock). Seismic Lines 4-6 The interpreted seismic velocity sections for Seismic Lines 4, 5, and 6, extending 210, 230, and 230 linear feet respectively, are displayed on Figures 5, 6, and 7 respectively. Seismic Lines 4-6 were run at different locations along the proposed pipeline alignment which runs between Stetson Creek and Cooper Lake (Figure 1). Interpretation of the seismic data indicates the presence of two velocity layers across each of these profile alignments. We have interpreted the low velocity (820-880 feet/second) material in the upper 2-8 feet of each of these profiles as velocity Layer 1 (organic material and unconsolidated overburden) and the high velocity material (13,000- 13,900 feet/second) extending from beneath Layer 1 to the maximum interpretation depths (20-40 feet below ground surface) of each profile alignment as velocity Layer 3 (competent rock). The Layer 1 – Layer 3 contacts for all three profiles generally mirror Geophysical Investigation Page 6 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 the topography profile, except at the topographic low which appears along Seismic Line 5 at station 35. As this topographic low occurs at a creek/stream crossing, it is likely that Layer 1 is missing from the interpreted section due to erosion. Seismic Line 7 The interpreted seismic velocity section for Seismic Line 7, extending 230 linear feet, is displayed on Figure 8. Seismic Line 7 was run along a section of the proposed pipeline alignment which runs between Stetson Creek and Cooper Lake (Figure 1). Interpretation of the seismic data indicates the presence of two velocity layers. We have interpreted the lower velocity material (1,460 feet/second) as velocity Layer 1 (organic material and unconsolidated overburden), which appears along other interpreted sections across the site. Layer 1 is approximately 10 feet in thickness, and generally mirrors surface topography at depth. We have interpreted the layer of moderate velocities (4,900 feet/second) beneath velocity Layer 1 as possible till or slide material. This layer, Layer 2a, is similar to materials found at similar depths on Seismic Line 1. While exhibiting a significant velocity contrast from velocity Layer 1, Layer 2a does not fall within the range of the interpreted competent rock values seen in Layer 3 elsewhere across the site, but instead better fits a range of values more commonly exhibited by till and/or slide materials. Seismic Line 8 The interpreted seismic velocity section for Seismic Line 8, extending 230 linear feet, is displayed on Figure 9. Seismic Line 8 was run along a section of the proposed pipeline alignment which runs between Stetson Creek and Cooper Lake (Figure 1), and is located between Seismic Lines 6 and 7. Similar to Seismic Lines 4-6, Seismic Line 8 exhibits a thin (2 feet) zone of low velocity (1,050 feet/second) material at the surface, and a zone of fast velocity (14,700 feet/second) material at depth. We have interpreted these two zones as velocity Layer 1 (organic material and unconsolidated overburden) and velocity Layer 3 (competent rock). Similar to Seismic Line 3, Seismic Line 8 also exhibits a zone of moderate velocity (2,750 feet/second) between Layers 1 and 3. The Layer 1-Layer 2 contact mirrors surface topography while the Layer 2-Layer 3 contact gradually thickens at depth from west (station 230) to east (station 0) across the profile alignment. We have interpreted this zone as velocity Layer 2 (consolidated overburden). Seismic Line 9 The interpreted seismic velocity section for Seismic Line 9, extending 230 linear feet, is displayed on Figure 10. Seismic Line 9 was run along a section of the proposed pipeline Geophysical Investigation Page 7 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 alignment which runs between Stetson Creek and Cooper Lake (Figure 1), and is located between Seismic Lines 4 and 5. Seismic Line 9 exhibited three velocity zones of 925 feet/second, 3,250 feet/second, and 8,500 feet/second, which we have interpreted as velocity Layers 1, 2, and 3 respectively. The layers have respective thickness of 1-2 feet, 6-8 feet, and <15 feet while the interface boundaries mirror the irregular and undulating surface topography. We have interpreted the layers as organic and unconsolidated soils, consolidated overburden, and competent rock respectively. While the interpreted velocity for Layer 2, 3,250 feet/second best corresponds to consolidated overburden; a second interpretation is that this material can be related to velocity Layer 2a (till and/or slide material). Resolution of Interpretation While the accuracy of the interpretation depends on site-specific conditions, geophysical methods in general provide an accuracy of +/- 10% under good conditions. Extreme changes in topography or depth to subsurface interfaces will affect the accuracy. As with any geophysical technique, these results are interpretive in nature and represent the best estimate of subsurface conditions considering the limitations of the geophysical method employed. Only direct observations using borings or test pits or other means can ultimately characterize subsurface conditions, using the geophysical results as a guide. CLOSURE Northwest Geophysical Associates, Inc. has performed this work in a manner consistent with the level of skill ordinarily exercised by members of the profession currently practicing under similar conditions. No warranty, express or implied, beyond exercise of reasonable care and professional diligence, is made. This report is intended for use only in accordance with the purposes of the study described within. Geophysical Investigation Page 8 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 28, 2009 Please feel free to contact us if you have any questions or comments regarding this information, or if you require further assistance. We appreciated the opportunity to work with you on this project and look forward to providing you with geophysical services in the future. Sincerely, Northwest Geophysical Associates, Inc. Rowland French, R.G. President Neil McKay Project Geophysicist Attachments: Figures 1-10 Attachment A: Seismic Refraction Technical Note File: CooperLake_Rpt02.doc NGA Project: 715 RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) RELATIVE ELEVATION (feet) Seismic Refraction Survey Stetson Creek Diversion Project Kenai Peninsula Borough, Alaska Attachment A NGA Technical Note Seismic Refraction Northwest Geophysical Associates, Inc. P.O. Box 1063, Corvallis, OR 97339-1063 (541) 757-7231 Fax: (541) 757-7331 www.nga.com info@nga.com © 2006 Northwest Geophysical Associates, Inc. Geophysical Services Environmental Groundwater Geotechnical Seismic Refraction TECHNICAL NOTE COVER rev.2B, AUG. 2006 Depth-to-Bedrock Competence of Bedrock Fault Mapping Groundwater Investigations © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 1 HEAD WAVE DIRECT WAVE RECIEVERS SEISMIC SOURCE REFRACTED WAVE IMPULSIVE WAVE BEDROCK OVERBURDEN Figure 1 Seismic Refraction Geometry DISCUSSION OF GEOPHYSICAL TECHNIQUES SEISMIC REFRACTION INTRODUCTION Seismic refraction is a commonly used geophysical technique to determine depth-to- bedrock, competence-of-bedrock, depth-to- water table, or depth to other seismic velocity boundaries. Seismic refraction is widely used in geotechnical and groundwater investigations. It is one of the classic geophysical techniques, presented in most introductory geophysical courses and texts. PHYSICAL PRINCIPLES The seismic refraction technique is illus- trated in the schematic drawing, Figure 1. An impulsive source creates a seismic wave (sound wave), which travels through the earth. When source to receiver separation is small, the first arrival is generally the direct wave propagating through the surface layer. When the wave-front reaches a layer of higher velocity (e.g. bedrock), a portion of the energy is refracted, or bent, and travels along the refractor as a head wave, at the seismic velocity of the refractor (bedrock). Energy from the propagating head wave leaves the refractor at the critical angle of refraction and returns to the surface, where its arrival is detected by a series of geophones and recorded on a seismograph. The angle of refraction depends on the ratio of velocities in the two materials (Snell’s Law). Travel times for the impulsive wave-front to reach each geophone are measured from the seismograph records. From those travel times, seismic velocities in each layer, and depths to each layer can be cal- culated. Seismic refraction differs from seismic reflection, which is widely used in petroleum exploration. In reflection seismic the waves re- flected off the geologic interface are utilized rather than the refracted arrivals. FIELD PROCEDURES When acquiring seis- mic refraction data a series of 12 or 24 geophones (re- ceivers) are placed along the seismic line at set intervals, the geophone interval. Each of these set-ups of 12 or more geophones is termed a spread. The geophone interval is generally 5 to 50 feet de- pending on the desired resolution and the desired depth of exploration. Due to the geometry of refraction (governed by Snell’s Law), it is necessary for the length of © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 2 the seismic spread to be approximately 3 to 5 times the depth of the overburden in order to detect the primary refractor (i.e., the bedrock). A series of 5 to 11 shots are initiated for each spread, one at each end, one or more be- yond the ends (off end), and one or more along the spread. These additional shotpoints allow dipping interfaces, changes in overburden mate- rials, and intermediate layers to be identified and resolved, increasing the accuracy of the depth- to-bedrock interpretation. Several spreads may be put together to form a longer refraction profile line. Several options are available for the seismic energy source. A sledge hammer strik- ing an metal plate is one of the simplest and most common sources. An airless jackhammer (Figure 2) provides additional energy and may be effective if the bedrock is 30 or 40 feet, par- ticularly if the overburden is sufficiently con- solidated. A higher energy source, such as an elastic weight drop (Figure 3) or 8-gauge seis- mic shells, may be required if the overburden is loose and poorly consolidated, or if the bedrock interface is significantly deeper. Small explo- sive charges may be used where depth of explo- ration, near surface attenuation, or high ambient noise demand a stronger source. DATA PROCESSING & INTERPRETATION Processing begins with picking the time of the first arrival. While several automated picking programs are available, the first arrival times must be checked for accuracy and consis- tency and adjusted as needed. Two basic methods of processing first arrival data are available, each with its strengths and limitations. These can be classified as delay-time techniques and tomographic tech- niques. Figures 4 and 5 show delay-time and tomographic interpretations of the same data. Figure 2 Airless Jack Hammer Figure 3 Elastic Weight Drop © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 3 Delay-Time Techniques Delay-time methods treat the earth as discrete layers, with refracted waves coming off each layer. Generally, these methods assume laterally continuous, constant velocity repre- sentations of the subsurface. Delay-time methods are sometimes referred to as the plus- minus method or the time-term method. The generalized reciprocal method (GRM) is based on the delay-time approach. Historically, the delay-time is the classic method of interpreting seismic refraction data. Redpath, 1973, is an excellent reference for the basic delay-time technique. Picked first arrivals are assigned a specific subsurface layer from which that seismic wave was refracted. This is a critical step in the interpretation process. Layer as- signment is based on the slope of the travel-time curves and the recognition of parallel curve segments from adjacent shots. Reduced traveltimes are calculated using refracted arrivals from each direction, effec- tively removing changing layer thickness on the velocity curve and leading to a better velocity 101091010910108101081010710107101061010610105101051010410104101031010310102101021010110101OAK CREEKOAK CREEK -20 00 100 DISTANCE (FEET)DEPTH (FEET)20-20 20 40 60 80 120 SOUTHWEST NORTHEAST -20 00 100 DISTANCE (FEET)DEPTH (FEET)20-20 20 40 60 80 120 SOUTHWEST NORTHEAST V1 = 1100 ft/secV1 = 1100 ft/sec V2 = 6100 ft/secV2 = 6100 ft/sec Figure 4 Layered Earth Interpretation SEISMIC P-WAVE VELOCITY FT/SEC 1200 1800 2400 3000 3600 4200 4800 5400 6000-20 00 100 DISTANCE (FEET)DEPTH (FEET)20-20 20 40 60 80 120 SOUTHWEST NORTHEAST Figure 5 Tomographic Interpretation © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 4 determination. Refractor depth is computed from the velocity and delay time, at each geophone. A common enhancement to the delay time method is to refine the model, using ray tracing. The ray tracing procedure adjusts the depth of the interface at the point the ray enters or emerges from the refractor. Tomographic Techniques Tomographic techniques partition the earth model into a mesh of finite-element or finite-difference elements, each with an assigned velocity. Element velocities are iteratively adjusted, altering the theoretical ray path(s) through the model. Velocities are adjusted until a best fit between the observed travel-times, and the modeled travel-times is arrived at. Tomographic methods evolved rapidly in the late 1990s (Zhu et al., 2000). Today there are several commercial software packages available. Each has its own variation of the inversion method, choice of the starting model, and introduction of geologic constraints(see Sheehan et al., 2005). Tomographic solutions allow for both lateral and vertical changes in velocity. Thus, they can approximate complex geologic situa- tions such as faulting and weathering. However, where sharp geologic/velocity boundaries are present, tomographic interpretations will tend to represent them as gradational boundaries. Tomographic solutions are inherently non-unique. Several earth models may yield similar travel-time curves. Therefore, it is often useful to look at the layered earth/delay-time solution along with the tomographic solution and geologic constraints to select the most appropriate. APPLICATIONS The product or deliverable from a seismic refraction survey is generally a profile, or cross section, along the seismic line showing depth-to- bedrock (or other primary refractor) at each geophone, and seismic velocities in the bedrock and the overburden. Often layers with interme- diate velocities (corresponding to layers or units with varying consolidation or lithology) can be identified and resolved. Seismic velocities relate to the soundness or competence of rock, and to the degree of con- solidation, cementation, and/or saturation in soils. The Caterpillar Tractor Co. has developed a series of tables which empirically relate seismic velocities to the rippability of bedrock with their equipment (such as a D8 or D9 with one or several ripper teeth). Figure 6 is an example of those rippability tables. In geotechnical engineering, depth-to- bedrock and rippability surveys are commonly used for design and cost estimates for road cuts, pipelines, and other civil engineering projects. Groundwater applications of seismic refraction include mapping bedrock channels, identifying faults and fracture zones, and delineation of geologic boundaries to constrain hydrogeologic models. LIMITATIONS There are several inherent limitations to the seismic refraction technique. Fortunately, for most projects, the required geologic condi- tions are met, and the seismic refraction program can be successfully. However, these conditions must always be considered when planning a refraction survey, and when examining refraction data. Velocity contrast A velocity contrast between strata is re- quired to refract the seismic wave. Hence, similar stratigraphic units are difficult to differentiate. Weathering zones with grada- tional changes present problems. Tomo- graphic techniques can now handle some of the weathering zone problems © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 5 Velocity reversals Standard refraction velocity analysis as- sumes that the velocity of successive layers increases with depth. Hidden layers Thin layers with small velocity contrast between adjacent layers may be hidden lay- ers, and no first arrival refracted from that layer will be present. These layers are diffi- cult to detect without additional borehole data. Lateral velocity variations Most standard interpretation software does not do a good job at handling geology with gross lateral variations in lithology. Fault zones can be detected from slower velocities in the brecciated fault gouge zones, but of- ten are poorly imaged unless a detailed sur- vey with short geophone spacing is carried out. Shot points coverage Tomographic models require dense shot coverage to properly constrain the models. This is an operational or cost constraint rather than a constraint inherent in the method. Urban Noise Urban noise (traffic, railways, construction, etc.) and natural noise (wind, waves, moving water, etc.) often limit the depth of ex- ploration, or dictate a more energetic source. D9L Ripper Performance Multi or Single Shank Ripper Estimated by Seismic Wave Velocities TOPSOIL CLAY GLACIAL TILL IGNEOUS ROCKS SEDIMENTARY ROCKS METAMORPHIC ROCKS MINERALS & ORES GRANITE BASALT TRAP ROCK SHALE SANDSTONE SILTSTONE CLAYSTONE CONGLOMERATE BRECCIA CALICHE LIMESTONE SCHIST SLATE COAL IRON ORE RIPPABLE MARGINAL NON-RIPPABLE Velocity in Meters Per Second x 1000 Velocity in Feet Per Second x 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 Taken From: Caterpillar Performance Handbook, 1983 Caterpillar Tractor Company Note: Seismic compression wave analysis serves as only one indicator of rippability and the only proven test is a machine trial. Figure 6 Example of Caterpillar Rippability Tables © Northwest Geophysical Associates, Inc. DISCUSSION OF GEOPHYSICAL TECHNIQUES Revision: August 2006 SEISMIC REFRACTION Page 6 Borehole or ground truth data is very use- ful in constraining the seismic interpretation. Seismic data is often used very effectively to interpolate between borings or to extrapolate away from borings. Downhole seismic veloci- ties surveys are even more effective at constraining refraction interpretations. FURTHER READING: Caterpillar Tractor Company, 2004, Caterpillar Performance Handbook, Edition 35, Peoria, Illinois. Dobrin, M.B. and Savit, C.H., 1988, Intro- duction to Geophysical Prospecting, 4th Edition, McGraw-Hill, New York, NY, 867 pp Kassenaar, Dirk, and John Luttinger, 1993, Practical considerations in GRM refraction surveys in glacial terrains: in Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems, Environmental and Engineering Geophysical Society, San Diego, California, April 18-22, pp. 355-371. Langston, Robert W., 1990, High Resolution refraction seismic data acquisition and interpretation:in Ward, S., ed., Geotechnical and Environmental Geophysics, Society of Exploration Geophysicists, Tulsa, OK, pp. 45-73. Palmer, Derecke, 1980, The Generalized Reciprocal Method of Seismic Refraction Interpretation: Society of Exploration Geophysicists, Tulsa, Oklahoma, 104 pp. Redpath, Bruce B., 1973, Seismic Refraction Exploration for Engineering Site Investigations: U.S. Army Engineer Waterways Experiment Station, Explosive Excavation Research Laboratory, Livermore, California, Technical Report E- 73-4, (NTIS AD-768710) 51 pp. Sheehan, J. R., Doll, W. E. and Mandell, W. A., 2005, An Evaluation of Methods and Available Software of Seismic Refraction Tomography Analysis, Journal of Environmental and Engineering Geophysics, v.10(1):21-34. Zhu, T., Cheadle, S., Petrella, A., and Gray, S., 2000, First-arrival tomography: method and application: Expanded Abstracts SEG 70th Annual Meeting, 2028-2031p. DISCUSSION OF GEOPHYSICAL TECHNIQUES SEISMIC REFRACTION Northwest Geophysical Associates, Inc. P.O. Box 1063 Corvallis, Oregon 97339 http://www.nga.com phone: (541) 757-7231 Rowland B. French, PhD, R.G. Senior Geophysicist Mark J. Villa Project Geophysicist Revision: August 2006 Printed :August 4, 2006 refraction_teq_2006-08A.doc APPENDIX II 2010 Geophysical Seismic Refraction Survey and Video Core Logging Program . Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1 of 2 Geotechnical Baseline Report – Final – Appendix II May 2012 APPENDIX II GEOPHYSICAL SEISMIC REFRACTION SURVEY AND VIDEO CORE LOGGING PROGRAM As part of a design level exploration program, MWH conducted five geophysical seismic refraction surveys (SL-10-1-1, SL-10-1-2, SL-10-2, SL-10-3 and SL-10-5). The surveys were conducted by Northwest Geophysical Associates of Corvallis, Oregon, between July 28 and July 30, 2010. Geophysical surveys were located in the field using Global Positioning System-based survey equipment with sub-meter accuracy. The geophysical survey locations are shown on the figures contain within the text of this report. Video televiewer core logging was conducted on borings B-2-2010 and B-5-2010. Details are provided in the report of geophysical services attached. Page 2 of 2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix II This page is intentionally blank. Northwest Geophysical Associates, Inc. 1600 SW Western Boulevard, Suite 200 PO Box 1063, Corvallis, OR 97339-1063 Phone: (541) 757-7231 FAX: (541) 757-7331 www.nga.com October 26, 2010 NGA Ref: 744 Paul D. Richards, P.E. Senior Geotechnical Engineer MWH Americas, Inc. 5100 SW Macadam Ave, No. 420 Portland, Oregon 97239 2010 Geophysical Investigation Stetson Creek Diversion Project Kenai Peninsula Borough, Alaska Dear Mr. Richards: This letter report presents the results of the seismic refraction and borehole televiewer survey that Northwest Geophysical Associates, Inc. (NGA) performed for the Stetson Creek Diversion Project (Figure 1 – Site Location) near Cooper Lake, Kenai Peninsula Borough, Alaska. This is a follow up investigation to the seismic refraction survey which NGA performed in fall of 2009. That work was presented to MWH in a report dated October 28, 2009. The Stetson Creek Diversion Project will include a diversion dam on Stetson Creek and pipeline from the diversion dam to Cooper Lake. The geophysical investigation was to aid MWH America’s geotechnical investigations of site conditions along the pipeline route, at the Cooper Lake spillway structure, and at the Stetson Creek diversion structure. The geophysical work included two tasks: 1) seismic refraction on 4 lines in the Stetson Creek canyon and 2) optical televiewer logging of borings at the Stetson Creek diversion structure and at the Cooper Lake spillway. Results of the two tasks are presented as separate sections of this report. SEISMIC REFRACTION The objective of the seismic refraction survey was to estimate depth-to-bedrock as well as to characterize overburden and bedrock materials with seismic velocities. An NGA technical note describing the seismic refraction method is attached (Attachment A). 2010 Geophysical Investigation Page 2 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 26, 2010 Field Methodology Field work was performed along four seismic lines during the period July 27-29, 2010. The locations of the four seismic lines (Lines SL10-1, SL10-2, SL10-3, and SL10-5) are shown on Figure 2, Seismic Line Locations. The seismic lines are numbered as proposed with the prefix “10” added to the number to differentiate the 2010 seismic lines from the 2009 seismic lines. Line SL10-1 crosses Stetson Creek at the diversion dam site, and SL10-2, SL10-3 and SL10-5 run along the pipeline alignment on the east side of Stetson Creek approximately 400, 1200 and 2200 feet downstream from the diversion dam respectively. SL10-4 was omitted due to time and access constraints at the time of the field survey. The proposed seismic line alignments were surveyed and brushed by an independent surveyor prior to the geophysical field work. Survey lath marking the start and end of the 300 foot long alignment were placed by the surveyors. Actual seismic geophone locations were then referenced to those endpoints using a 300-fiberglass tape. Final seismic line locations, as well as the surveyed alignment endpoints, are shown on Figure 2. NGA measured relative elevations along each line using a handheld inclinometer and measuring tape. Those relative elevations were tied to the surveyed elevations of the alignment endpoints. The seismic field investigation was performed using a 24-channel Geometrics Geode seismograph to record the data. A 30kg slide hammer was used as the primary seismic source to generate a seismic wave at regular intervals along each seismic line and also at some distance from both ends of each line. On SL10-1-1 NGA used 24 geophone receivers spaced at 5 foot intervals, yielding a line length of 115 feet. On SL10-1-2 NGA used 20 geophone receivers spaced at 5 foot intervals, yielding a line length of 95. At SL10-2, -3, and -5 NGA used 24 geophone receivers spaced at 10 foot intervals, yielding a line length of 230 feet. INTERPRETATION RESULTS The results of the seismic survey are shown on the interpretated profiles (Figures 3-6). The profiles show the geophone locations along the ground surface, the interpreted depths/thicknesses of each layer, and interpreted velocities. Seismic Stratigraphy Interpretations For these seismic lines along Stetson Creek we see the same basic units as those reported in the 2009 survey along the pipeline alignment closer to Cooper Lake. Those units are summarized in Table 1: 2010 Geophysical Investigation Page 3 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 26, 2010 TABLE 1 Seismic Stratigraphy GRAPHIC PATTERN LAYER DEISGNATION & SEISMIC VELOCITY POSSIBLE CLASSIFICATION (Feet/Second) Dot Fill V1 - 300 – 1,200 V1 - Unconsolidated soil and/or organic material. Angled Hatch V2 - 2,150 – 2,800 V2 – Poorly consolidated overburden, landslide material. Solid Grey V3 - 4,200 – 13,000 Weathered or Competent Rock (Phyllite – Slate, per conversation with MWH). Seismic Profile Interpretations Seismic Line 10-1 Seismic Line 10-1 was run crossing Stetson Creek at the planned site of the diversion structure. The line was run in two spreads with SL10-1-1 on the left bank to the west and SL10-1-2 on the right bank to the east. Both spreads used a 5-foot geophone spacing. The spread lengths were 115 and 95 feet (slope distance) respectively. Geophone elevations were measured in the field with a handheld inclinometer. However, the final interpretation used elevations taken from the topographic map, Figure 2. The interpretation shows a low velocity surface layer (300 ft/sec to 1,200 ft/sec). This corresponds to a thick organic mat and possibly some unconsolidated slide material. The lower layer velocities, 7,000 ft/sec and 4,200 ft/sec, are interpreted as bedrock and weathered bedrock. A phyllite-slate is observed at the surface in the two boreholes on that line, B1 and B2. Data quality on this line was fair, with strong attenuation in the organic mat and excessive seismic noise due to the fast flowing creek. 2010 Geophysical Investigation Page 4 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 26, 2010 Seismic Line 10-2 The interpreted seismic profile for Seismic Line 2, extending 230 linear feet, is displayed on Figure 4. Seismic Line 2 was run along the east side of Stetson Creek 400 feet north (downstream) of the proposed diversion dam site. The line was run on a steep side slope. The seismic interpretation indicates the presence of lower velocity materials: V1=1,000 ft/sec and V2=2,600 ft/sec. These layers combined are 3 to 10 feet thick and are interpreted as organic materials overlying slide deposits. Layer 3 is interpreted as competent bedrock with a representative velocity of 8,600 ft/sec. Seismic Line 10-3 The interpreted seismic velocity profile for Seismic Line 3, extending 230 linear feet, is displayed on Figure 5. Seismic Line 3 was run along the east side of Stetson Creek 1200 feet downstream (north) of the proposed diversion dam site. The line was run on a steep side slope. No bedrock velocities were observed at this site. The velocities of 1,000 ft/sec and 2,150 ft/sec are interpreted as organic mat and poorly consolidated, possibly landslide materials. Seismic Line 10-5 The interpreted seismic velocity section for Seismic Line 5, extending 230 linear feet, is displayed on Figure 4. Seismic Line 5 was run along the east side of Stetson Creek 2,200 feet downstream of the proposed diversion dam site. The line was run on a steep side slope. The interpretation shows competent bedrock, with velocities of 13,000 ft/sec, at depths from 50 to 60 feet. Above that is a thick overburden, possibly poorly consolidated landslide debris. Resolution of Interpretation While the accuracy of the interpretation depends on site-specific conditions, geophysical methods in general provide an accuracy of +/- 10% under good conditions. Extreme changes in topography or depth to subsurface interfaces will affect the accuracy. As with any geophysical technique, these results are interpretive in nature and represent the best estimate of subsurface conditions considering the limitations of the geophysical method employed. Only direct observations using borings or test pits or other means can ultimately characterize subsurface conditions, using the geophysical results as a guide. 2010 Geophysical Investigation Page 5 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 26, 2010 TELEVIEWER LOGGING Field Methodology Field work was performed at two borehole locations during the period July 25-26, 2010. Borehole B-2 is located on the right bank (east side) of Stetson Creek at the proposed diversion damn site. Borehole B-5 is located in the Cooper Lake spillway adjacent to the existing dam on the west end of Cooper Lake. It was originally planned to log four borings: B1 and B2 at the diversion structure and B4 and B5 at the Cooper Lake spillway. However, the high water in Stetson Creek at the time of the survey prevented access to B1 on the left bank of the creek. Boring B4 at the spillway was plugged at a depth of approximately 6 feet and the logging tools could not get past that depth. The borehole logging was performed using a Mount Sopris/ALT model OBI40 Optical Borehole Televiewer, and a Poly Caliper Probe. A Matrix Portable Digital Logger console and side-by-side winch were used to control those probes. The caliper log, which measures the diameter of the borehole, was run prior to the televiewer to assure that the boring was not obstructed. Caliper boring diameter information was also used to correct the dip angles measured from the televiewer logs. Both borings were water filled to within 2 feet of the surface. Boring logs have been corrected to true north using the magnetic declination of 18.7° E. The depth is referenced to the ground surface at the boring. Televiewer Interpretation Results Televiewer images are presented in Figures 7 and 8 for borings B2 and B5 respectively. Regular foliation can be seen in both borings. We have indicated strike and dip of several of the foliation features in each log. The foliation direction was very consistent within each borehole. Boring B2 foliation generally had a dip direction of about 290° with dips near 70°. Boring B5 foliation generally had a dip direction of about 100° with dips near 70°. Those directions are referenced to the true north direction. CLOSURE Northwest Geophysical Associates, Inc. has performed this work in a manner consistent with the level of skill ordinarily exercised by members of the profession currently practicing under similar conditions. No warranty, express or implied, beyond exercise of reasonable care and professional diligence, is made. This report is intended for use only in accordance with the purposes of the study described within. 2010 Geophysical Investigation Page 6 Stetson Creek Diversion Project, Kenai Peninsula Borough, Alaska October 26, 2010 Please feel free to contact us if you have any questions or comments regarding this information, or if you require further assistance. We appreciated the opportunity to work with you on this project and look forward to providing you with geophysical services in the future. Sincerely, Northwest Geophysical Associates, Inc. Rowland French, R.G. President Attachments: Figures 1-8 Attachment A: Seismic Refraction Technical Note File: CooperLake 2010_Rpt02.doc NGA Project: 744 ELEVATION (feet) ELEVATION (feet) ELEVATION (feet) ELEVATION (feet) APPENDIX III 2009 Test Pit Procedures, Logs, and Photographs . Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1 of 2 Geotechnical Baseline Report – Final – Appendix III May 2012 APPENDIX III 2009 TEST PIT PROCEDURES, LOGS, AND PHOTOGRAPHS As part of a previous exploration program, MWH conducted 12 test pit excavations (TP-1 through TP-12). Each test pit was excavated using a Komatsu PC-120, track-mounted excavator on October 5 and 6, 2009. The excavator was operated by Dan Hayes of D&R Construction of Seward, Alaska. Test pits were backfilled with excavated soil and compacted to the extent feasible with the excavator. Test pit locations were determined in the field using a hand-held Global Positioning System receiver and by pacing from features identified on site drawings. Test pit elevations shown in the explorations logs were based on elevation values shown on available topographic surveys of the site. Test pit locations are shown on Figures 2 and 13 of the report text. Test pit locations and elevations should be considered approximate. Soils encountered were classified in accordance with the ASTM D 2488, Practice for Description and Identification of Soils (Visual-Manual Procedure). Soil samples were collected directly from the test pit or from the bucket of the excavator at selected locations and depths. Collected samples were packaged and shipped to laboratories for testing in general accordance with the procedures outlined by ASTM D 4220, Standard Practices for Preserving and Transporting Soil Samples. Exploration logs and photographs of test pits TP-1 through TP-12 are presented in the following pages. Page 2 of 2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix III This page is intentionally blank. Letter Name Hatching Color GW Well-graded gravels or gravel-sand mixtures, little or no fines T GP Poorly-graded gravels or gravel-sand mixtures, little or no fines GM Silty gravels, gravel-sand-silt mixtures D GC Clayey gravels, gravel-sand-silt mixtures SW Well-graded sands or gravelly sands, little or no fines Ring Sample: 1.5" ID ring sampler, hand driven R SP Poorly-graded sands or gravelly sands, little or no fines Continuous Sample C SM Silty sands, sand-silt mixtures SC Clayey sands, sand-silt mixtures ML Inorganic silts & very fine sands, rock flour, silty or clayey fine sands, or clayey silts with slight plasticity Total Petroleum Hydrocarbons as gasoline G CL Inorganic clays of low to medium plasticity, gravelly clays, sandy or silty clays, lean clays Benzene B OL Organic silts and organic silt-clays of low plasticity Toluene T MH Inorganic silts and organic silt-clays of low plasticity Ethylbenzene E CH Inorganic clays of medium to high plasticity, organic silts Xylenes X OH Peat and other highly organic silts Methtl tertiary-butyl ether M Pt OrangePeat and other highly organic soils Photoionization Detector PID Sandstone Soil concentrations in mg/kg Siltstone Claystone Shale or Chert Water level at time of exploration Fill Fill-landfill refuse Equilibrated water level Fill Sand and Sandy Soils RedYellowChemical Test Type GreenBlueFine-grained SoilsSilt, Clay, Silty Soils, Clayey Soils Bedrock Groundwater concentrations in mg/l Major Divisions Symbol Sample Type Coarse-grained SoilsGravel and Gravelly Soils RedStandard Penetration Test: split spoon sampler, 2.0" OD/ 1-3/8" ID, driven with 140 lb. weight, 30" drop YellowModified California Sampler: Split spoon sampler, 3.0" OD, driven with 140 lb. weight, 30" drop PROJECT NO. 1007059 FIGURE NO. C-0 Geotechnical Investigation Report Stetson Creek Diversion and Cooper Lake Outlet Chugach Electric Association, Inc. Anchorage, Alaska UNIFIED SOIL CLASSIFICATION SYSTEM AND EXPLORATION LOG EXPLANATION LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-1 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-2 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-3 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-4 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-5 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-6 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-7 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-8 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 5, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-9 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 6, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-10 LOG OF EXPLORATION NO. DATE DRILLED: Oct. 6, 2009 EQUIPMENT: Komatsu PC-120 Excavator ELEVATION: TP-11 APPENDIX IV 2010 Boring Procedures, Logs, and Photographs . Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1 of 2 Geotechnical Baseline Report – Final – Appendix IV May 2012 APPENDIX IV 2010 BORING PROCEDURES, LOGS, AND PHOTOGRAPHS The 2010 geotechnical exploration program included six (6) subsurface boring explorations (B- 1-2010 through B-6-2010). Borings B-1-2010 and B-2-2010 were conducted using a platform- mounted CME 45 drill rig using NQ triple tube rock coring methods to depths of 40.4 and 30.0 ft, respectively. Borings B-3-2010 through B-6-2010 were conducted using a track-mounted CME 850 drill rig. Boring B-3-2010 was conducted using both mud-rotary and HQ triple tube rock coring methods to a depth of 47.7 ft. Borings B-4-2010 and B-5-2010 were conducted using HQ triple tube rock coring methods to a depth of 30.0 ft in each hole. Boring B-6-2010 was conducted using mud-rotary drilling methods to a depth of 51.5 ft. The subsurface borings explorations were conducted By Discovery Drilling of Anchorage, Alaska between July 6, 2010 and July 13, 2010. Borings B-3-2010 and B-6-2010 were backfilled with hydrated bentonite chips. The remaining borings were backfilled with cement-bentonite grout. The location of each boring was surveyed by McClane Consulting, Inc. of Soldotna, Alaska. Boring locations are shown on Figures 3 and 4. Down-hole televiewer surveying was conducted on borings B-2- 2010 and B-5-2010 by Northwest Geophysical Associates, Inc. of Corvallis, Oregon. Televiewer surveys of the remaining rock core borings were not completed due to caving conditions at the time of the surveys. Down-hole televiewer survey logs are presented in Appendix II. Soils encountered were classified in accordance with the ASTM International (ASTM) D 2488, Practice for Description and Identification of Soils (Visual-Manual Procedure). Soil samples were collected from disturbed, California Modified split-spoon samplers driven with a 300-lb hammer at regular intervals. Collected samples were packaged and shipped to laboratories for testing in general accordance with the procedures outlined by ASTM D 4220, Standard Practices for Preserving and Transporting Soil Samples. Rock conditions encountered were classified in accordance with the United States Bureau of Reclamation’s (USBR’s) Engineering Geology Field Manual (1998). Continuous rock core samples were collected and classified from each of the rock core borings. Rock drilling, sample storage, and sample transport were conducted in general accordance with ASTM D 2113, Standard Practice for Diamond Core Drilling for Site Investigation. Exploration logs and photographs of borings B-1-2010 through B-6-2010 are presented in the following pages. Page 2 of 2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix IV This page is intentionally blank. 1 2 3 4 5 6 7 8 9 10 11 12 13 1 2 3 4 5 6 7 8 9 10 11 12 13 Depth: Distance in feet below the collar of the boring. Graphic Log: A depiction of material encountered in boring using symbols to represent individual groups of rock and soil stratigraphy. Material Description: Lithologic description of the rock and soil encountered. Sample Type/Number: Type and identification number of sample collected at depth interval shown. Recovery/RQD: Actual soil recovery in sampler as a percentage of the sampler penetration. Refer to Key to Rock Core Logs for description of RQD. Blow Counts: Number of blows to advance a Modified California sampler each six-inch drive interval, or distance noted, using a 300-lb auto-trip hammer with a 30-inch drop. Pocket Pen.: Index test results for a pocket penetrometer expressed in tons per square foot. Dry Unit Weight: Unit weight of soil determined by ASTM D4767. Expressed in pounds per cubic foot. Moisture Content: Laboratory moisture content expressed as a percentage determined by ASTM D2216. Liquid Limit: Laboratory liquid limit of soil determined by ASTM D5731. Expressed as a percentage. Plastic Limit: Laboratory plastic limit of soil determined by ASTM D5731. Expressed as a percentage. Plastic Index: Plastic index of soil (Liquid Limit - Plastic Limit) determined by ASTM D5731. Expressed as a percentage. Fines Content: Amount of soil passing a Standard US No. 200 Sieve as determined by ASTM D422 and D1140. GEOLOGICAL TESTING COLUMN DESCRIPTIONS TYPICAL ROCK GRAPHIC SYMBOLS Run No.: Number of the individual coring interval. Depth of top and Slate bottom of coring interval in parentheses. Claystone/Mudstone Bit: Core or drill bit used during coring interval. Siltstone Recovery: Amount (in percent) of core recovered from the coring interval; calculated as length of core recovered divided by length of run. Sandstone RQD: (Rock Quality Designation) Amount (in percent) of intact core (pieces of sound core greater than 4 inches long) in each coring ABBREVIATIONS interval; calculated as the sum of lengths of intact core divided by length of core run. Ck Creek E Easting Depth: Distance (in feet) below the collar of the borehole.FD_Fracture Density Descriptor ft Feet Geology: Graphic log of material encountered in boring using H_Hardness/Strength Descriptor symbols to represent individual groups rock stratigraphy.HL_Fracture Healing Descriptor in Inch Degree of Weathering: Condition of rock mass with respect to J Joint decomposition in accordance with the USBR classification system. Lk Lake Refer to Key to Rock Descriptions for additional details.MB Mechanical Break N Northing Discontinuities Per Foot: (Fracture Index or Fracture Frequency) NQTT NQ Triple Tube The number of naturally occurring discontinuities per foot of core.O_Fracture Openness Descriptor R_Joint Roughness Descriptor Discontinuity Type: Indicates type of imperfection in the rock core. S Shear May include joints, faults, shears, bedding, mechanical breaks etc.SP_Joint Spacing Descriptor T_Fracture Filling Thickness Descriptor Discontinuity Dip: Angle formed between the discontinuity and a W_Weathering Descriptor (ft) Geology Degree of Weathering Discontinuities Description Discont./ft. Type Dip KEY TO ROCK CORE LOGS DRILLING/GEOMECHANICAL Run No. (Start - Stop)BitRecovery (%)RQD (%)Depth 0 2 4 6 8 60 20 80 40 60 20 80 40 W1 W5 W9 W3 W7 1 2 3 4 5 6 7 8 9 10 12 13 1 2 3 4 5 6 7 8 9 10 11 Testing Notes: Drilling Rate Blocking Water loss plane orthogonal to the boring axis. Discontinuity Column: Provides a graphical depiction of the discontinuities observed in the core. Geologic Description: Detailed description of the rock conditions encountered in the core. Descriptions are in accordance with USBR field manual. Refer to Key to Rock Descriptions for additional detail. Testing: Indicates depths that field or laboratory tests were conducted. Also provides notes on related field observations and drilling data. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 1 of 9 0 2 4 6 8 60 20 80 40 60 20 80 40 W1 W5 W9 W3 W7 1 2 3 4 5 6 7 8 9 10 12 13 1 2 3 4 5 6 7 8 9 10 11 11 12 13 Testing Notes: Drilling Rate Blocking Water loss GRAIN SIZE DESCRIPTORS BEDDING, FOLIATION, OR FLOW TEXTURE DESCRIPTORS Descriptor Grain Size Descriptor Thickness Very Coarse Grained or Pegmatitic >3/8 in Massive >10 ft Coarse Grained 3/16 to 3/8 in Very Thickly, Bedded, Foliated, or Banded 3 to 10 ft Medium Grained 1/32 to 3/16 in Thickly 1 to 3 ft Fine Grained 0.04 to 1/32 in Moderately 0.3 to 1 ft Aphanitic <0.04 in Thinly 0.1 to 0.3 ft Very Thinly 3/8 in to 0.1 ft Laminated (Intensely Foliated or Banded) <3/8 in WEATHERING DESCRIPTORS Numeric Descriptor Description Fresh No discoloration or oxidation. No change to texture or solutioning. Slightly Weathered to Fresh Slightly Weathered Discoloration or oxidation is limited to surface or short distance from fractures. Some feldspars are dull. Texture is preserved. Minor leaching of some soluble minerals. Moderately to Slightly Weathered Moderately Weathered Discoloration or oxidation extends from fractures, usually throughout. Feldspars are cloudy. Texture is generally preserved. Soluble minerals may be mostly leached. Intensely to Moderately Weathered Intensely Weathered Discoloration or oxidation throughout. All feldspars and Fe-Mg minerals are altered to clay to some extent. All fractured surfaces are discolored or oxidized. Texture is altered by chemical disintegration. Leaching of soluble minerals may be complete. Very Intensely Weathered Decomposed Discolored or oxidized throughout. Resembles soil. Partial or complete remnant rock structure may be preserved. Leaching of soluble minerals usually complete. ROCK HARDNESS/STRENGTH DESCRIPTORS Numeric Descriptor Description E t l H d C t b t h d ith k if b hi d ith t d h h blH1 W4 W5 W6 W7 W8 W9 KEY TO ROCK CORE LOGS ROCK DESCRIPTORS W1 W2 W3 Extremely Hard Cannot be scratched with knife; can be chipped with repeated heavy hammer blows. Very Hard Cannot be scratched with knife; Core or fragment breaks with repeated heavy hammer blows. Hard Can be scratched with knife or sharp pick with difficulty; Heavy hammer blow required to break specimen. Moderately Hard Can be scratched with knife or sharp pick with light or moderate pressure. Core or fragment breaks with moderate hammer blow. Moderately Soft Can be grooved 1/16 in deep by knife or sharp pick with moderate or heavy pressure. Core or fragment breaks with light hammer blow or heavy manual pressure. Soft Can be grooved or gouged easily by knife or sharp pick with light pressure, can be scratched with fingernail. Breaks with light to moderate manual pressure. Very Soft Can be readily indented, grooved or gouged with fingernail, or carved with knife. Breaks with light manual pressure. H1 H7 H5 H6 H2 H3 H4 PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 2 of 9 FRACTURE DENSITY DESCRIPTORS Numeric Descriptor Description Unfractured No observed fractures. Very Slightly Fractured Core recovered mostly in lengths greater than 3 ft. Slightly to Very Slightly Fractured Slightly Fractured Core recovered mostly in lengths from 1 to 3 ft with few exceptions. Moderately to Slightly Fractured Moderately Fractured Core recovered mostly in lengths from 0.33 to 1 ft with most lengths about 0.67 ft. Intensely to Moderately Fractured Intensely Fractured Lengths average from 0.1 to 0.33 ft with fragmented intervals. Core recovered mostly in lengths less than 0.33 ft. Very Intensely to Intensely Fractured Very Intensely to Intensely Fractured Core recovered mostly as chips and fragments with a few scattered short core lengths. JOINT SPACING DESCRIPTORS Numeric Descriptor Description Extremely Widely Spaced >10 ft Very Widely Spaced 3 to 10 ft Widely Spaced 1 to 3 ft Moderately Widely Spaced 0.3 to 1 ft Closely Spaced 0.1 to 0.3 ft Very Closely Spaced <0.1 ft FRACTURE OPENNESS DESCRIPTORS Numeric Descriptor Description Tight No visible separation. Slightly Open < 1/32 in Moderately Open 1/32 to 1/8 in Open 1/8 to 3/8 in M d t l Wid 3/8 i t 0 1 ft SP5 O1 O2 O3 O4 SP6 O0 FD8 SP1 SP2 SP3 FD9 SP4 FD0 FD1 FD2 FD4 FD5 FD7 FD3 FD6 KEY TO ROCK CORE LOGS ROCK DISCONTINUITY DESCRIPTORS Moderately Wide 3/8 in to 0.1 ft Wide >0.1 ft FRACTURE FILLING THICKNESS DESCRIPTORS Numeric Descriptor Description T0 Clean No film coating. T1 Very Thin <1/32 in T2 Moderately Thin 1/32 to 1/8 in T3 Thin 1/8 to 3/8 in T4 Moderately Thick 3/8 in to 0.1 ft T5 Moderately Thick >0.1 ft O4 O5 PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 3 of 9 FRACTURE HEALING DESCRIPTORS Numeric Descriptor Description Totally Healed Completely healed or recemented to a degree at least as hard as surrounding rock. Moderately Healed Greater than 50 percent of the fracture material, fracture surfaces, or healed filling is healed or recemented; and/or strength of the healing agent is less hard than surrounding rock. Partially Healed Less than 50 percent of fractured material, filling, or fracture surface is healed or recemented. Not Healed Fracture surface, fracture zone, or filling is not healed or recemented; rock fragments or filling (if present) is held in place by its own angularity and/or cohesiveness. FRACTURE ROUGHNESS DESCRIPTORS Numeric Descriptor Description Stepped Near normal steps and ridges occur on the fracture surface. Rough Large, angular asperities can be seen. Moderately Rough Asperities are clearly visible and fractured surface feels abrasive. Slightly Rough Small asperities on the fracture surface are visible and can be felt. Smooth No asperities, smooth to the touch. Polished Extremely smooth and shiny. R3 R4 R5 R6 R1 R2 HL0 HL2 HL3 HL5 KEY TO ROCK CORE LOGS ROCK DISCONTINUITY DESCRIPTORS (CONTINUED) PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 4 of 9 Stetson Ck./Cooper Lk ELEVATION 1453.5 ft DRILLING CONTRACTOR: Discovery Drilling, Inc. Diversion Lt. Abutment INCLINATION Vertical RIG: CME 45 - Platform Mounted N 2349989 DIRECTION N/A START: July 7, 2010 E 525565.2 LOGGED BY P. Richards FINISH: July 8, 2010 GEOLOGICAL TESTING SLATE: Dark gray, fine grained, slightly weathered to fresh (W2), moderately hard (H4), very intensely 26 0 fractured (FD9); Discontinuities are very closely spaced (SP6), tight to slightly open (O0 to O1), clean to thinly J 25 filled (T0 to T1), partly healed (HL3), slightly rough (R4), 50 0 and predominately dip at 25-30 degrees. (Potentially Water loss at 5 to displaced rock)7 ft 27 0 Blocked off at 7.5 ft 60 0 60 0 J 20,50 J 25, 30, 90 SLATE: Dark gray, fine grained, slightly weathered to J/MB 80/0 fresh (W2), moderately hard (H4), intensely to MB 0 moderately fractured (FD6); Discontinuities are Packer Test 15 to J/MB 20/20 moderately to closely spaced (SP3 to SP4), tight to 40.4 ft = 100 58 S 20 moderately open (O0 to O2), clean to very thinly filled (T0 0.5 Lugeons to T1), partly healed (HL3), slightly rough (R4), predominately dip at 30, 50 to 60, and 75 degrees, and J/MB 20/10 are occasionally slickensided. MB 20 100 56 S 30 Moderately rough (R3) at 22.2 ft. J 15 J 70 MB 60 J/MB 40/20 100 100 S 55 MB 60 J/MB 40/70,80 J/MB 20/0 98 86 S 10 MB 0, 20 PROJECT Discont./ft. DRAFT LOG OF COREHOLE NO. B-1 DRILLING/GEOMECHANICAL Description COORDINATES (ft) Depth LOCATION Run No. (Start - Stop)BitRecovery (%)RQD (%)1 (0.0 - 5.0)25 (10.0 - 15.0)DipGeology DiscontinuitiesDegree of Weathering Type 0 2 4 6 8 5 10 15 20 25 30 35 60 20 80 40 60 20 80 40 34NQTT6 (15.0 - 20.2)7 (20.2 - 25.2)9 (30.4 - 35.4) 8 (25.2 - 30.4) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss S 30 S/J 85/10,80 100 52 S/J 10,65/30 S/J 5/15 J/MB 85/10, 30 Terminal Depth = 40.4 ft Packer Test Conducted from 15 to 40.4 ft Notes Run 2 from 5.0 to 7.0 ft Run 3 from 7.0 to 8.5 ft Run 4 from 8.5 to 10.0 ft THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF ACTUAL CONDITIONS ENCOUNTERED. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 5 of 9 0 2 4 6 8 5 10 15 20 25 30 35 40 45 60 20 80 40 60 20 80 40 55 5034NQTT6 (15.0 - 20.2)7 (20.2 - 25.2)9 (30.4 - 35.4) 8 (25.2 - 30.4)10 (35.4 - 40.4) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Stetson Ck./Cooper Lk ELEVATION 1437.8 ft DRILLING CONTRACTOR: Discovery Drilling, Inc. Diversion Rt. Abutment INCLINATION Vertical RIG: CME 45 - Platform Mounted N 2349922 DIRECTION N/A START: July 6, 2010 E 525566.7 LOGGED BY P. Richards FINISH: July 7, 2010 GEOLOGICAL TESTING J 60 SLATE: Dark gray, fine grained, slightly weathered to J 50, 90 fresh (W2), moderately hard (H4), intensely to 92 24 moderately fractured (FD6); Discontinuities are J 0,10 moderately to closely spaced (SP3 to SP4), tight to J 50 moderately open (O0 to O2), clean to very thinly filled J 5, 10, 80 (T0 to T1), partly healed (HL3), slightly rough (R4), J 5 predominately dip at 30, 50 to 60, and 75 degrees, 98 60 J 40 and are occasionally slickensided. J/MB 75/10 J 10, 45 J/MB 10/5 Packer test 10.0 J 0 to 30.0 ft = 100 88 J/MB 30/10 0.0 Lugeons J 20 J 30,75 J 10 100 76 J/MB 35/30 J/MB 35, 70/30 Blocked off at 90 86 MB 30 17.9 ft. J/MB 50,70/45 S 70 -Clay infilling at 20.8 ft. J/MB 65/30 92 38 J 10, 50, 60 J 10, 50, 60 Very intensely fractured (FD9) between 22.5 and 23.2 ft. 100 50 J 30 Blocked off at 25.8 ft. 100 88 J 30,50 Terminal Depth = 30.0 ft Packer Test Conducted from 10.0 to 30.0 ft DRAFT LOG OF COREHOLE NO. B-2 PROJECT LOCATION COORDINATES Run No. (Start - Stop)BitRecovery (%)RQD (%)Depth Degree of Weathering Description Discont./ft. Type DipGeology Discontinuities (ft)1 (0.0 - 5.0)0 2 4 6 8 5 10 15 20 25 30 35 60 20 80 40 60 20 80 40 2 (5.0 - 10.0)NQTT4 (15.0 - 17.9)6 (20.0 - 25.0)73 (10.0 - 15.0)58 (25.8 - 30.0) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Notes: Run 5 from 17.9 to 20.0 ft Run 7 from 25.0 to 25.8 ft THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF ACTUAL CONDITIONS ENCOUNTERED. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 6 of 9 0 2 4 6 8 5 10 15 20 25 30 35 40 45 60 20 80 40 60 20 80 40 55 502 (5.0 - 10.0)NQTT4 (15.0 - 17.9)6 (20.0 - 25.0)73 (10.0 - 15.0)58 (25.8 - 30.0) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Stetson Ck./Cooper Lk ELEVATION 1189.7 ft DRILLING CONTRACTOR: Discovery Drilling, Inc. Near Siphon Intake INCLINATION Vertical RIG: CME 850 - Track Mounted N 2350220.0 DIRECTION N/A START: July 11, 2010 E 532275.3 LOGGED BY P. Richards FINISH: July 12, 2010 GEOLOGICAL TESTING See Boring Log for Description of B-3 between depths of 0.0 and 28.0 ft. J 50 SLATE: Dark gray, fine grained, slightly weathered to J 50 fresh (W2), moderately hard (H4), intensely to 100 22 J/MB 60,70 moderately fractured (FD6); Discontinuities are J 40,50 moderately to closely spaced (SP3 to SP4), tight to J 50,60,70 moderately open (O0 to O2), clean to very thinly filled J 50,60 (T0 to T1), partly healed (HL3), slightly rough (R4), Geology Degree of Weathering Discontinuities Description BitRecovery (%)RQD (%)Depth Discont./ft. Type Dip DRAFT LOG OF COREHOLE NO. B-3 PROJECT LOCATION COORDINATES (ft)Run No. (Start - Stop)0 2 4 6 8 5 10 15 20 25 30 35 60 20 80 40 60 20 80 40 HQTT7(28.8-30.0)1(28.0 - 32.5)- 37.5) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss 86 0 J 40, 50 predominately dip at 30 to 65 degrees, and are J 30,40,50 occasionally slickensided.Lost circulation at J 50 -Very intensely fractured zone 32.5 to 34.5 ft.35 ft. J 50,60 -Very intensely fractured zone 37.0 to 37.5 ft. J/MB 30 -Very intensely fractured zone 38.5-41.2 ft. 100 0 J 40,50 Blocked off at 41.2 95 0 J 50, 60 ft. J 40, 60 J 60 92 0 J 45,60,70 -Very intensely fractured zone 46.0 to 47.0 ft. J 30,50,60 Terminal Depth = 47.7 ft. Boring Backfilled with hydrated bentonite chips. Notes: Run 3 from 37.5 to 38.5 ft Run 5 from 41.2 to 43.2 ft THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF ACTUAL CONDITIONS ENCOUNTERED. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 7 of 9 0 2 4 6 8 5 10 15 20 25 30 35 40 45 60 20 80 40 60 20 80 40 55 50HQTT7(28.8-30.0)1(28.0 - 32.5)2(32.5 - 37.5)3100 30 4 (38.5 - 41.2)56 (43.2 - 47.7) W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Stetson Ck./Cooper Lk ELEVATION 1206.1 ft DRILLING CONTRACTOR: Discovery Drilling, Inc. Southeastern Spillway INCLINATION Vertical RIG: CME 850 - Track Mounted N 2350263.9 DIRECTION N/A START: July 10, 2010 E 532063.3 LOGGED BY P. Richards FINISH: July 10, 2010 GEOLOGICAL TESTING J 50 SLATE: Dark gray, fine grained, slightly weathered to J 50,40 fresh (W2), moderately hard (H4), intensely to 92 50 J 40 moderately fractured (FD6); Discontinuities are J/MB 0,20/40 moderately to closely spaced (SP3 to SP4), tight to S/J 35/40,85 moderately open (O0 to O2), clean to very thinly filled J 45 (T0 to T1), partly healed (HL3), slightly rough (R4), J/MB 40,50/30 predominately dip at 30 to 60 75 degrees, and are 100 16 J 30,60 occasionally slickensided. S/J 55/40,45,60 -Very intensely fractured (FD9) zones at 4.1 to 4.2, 4.7 to Blocked off at 9.9 J 40 4.9, 5.4 to 5.6, 9.0 to 9.9, 11.5 to 11.6, 14.5 to 15.7, 22.7 ft. J 50 to 23.1, 23.8 to 25.3, and 28.8 to 30.0 ft. 100 70 J 25,40 J 40,50,60 Blocked off at J 50 14.5 ft. 100 60 J 40,45,50 J 40 Thin iron-oxide stain at 18.0 ft.Blocked off at J 60,70 18.8 ft. S/J/MB 45/20/40 100 42 S 45 -1/8-inch gouge at 21.9 ft. J 45 J 20 100 60 J 30,40 J/MB 20,50/10 J 20,40,60 67 0 J 60 Terminal Depth = 30.0 ft Notes: DRAFT LOG OF COREHOLE NO. B-4 PROJECT LOCATION COORDINATES Run No. (Start - Stop)BitRecovery (%)RQD (%)Depth Degree of Weathering Description Discont./ft. Type DipGeology Discontinuities (ft)1 (0.0 - 5.0)0 2 4 6 8 5 10 15 20 25 30 35 60 20 80 40 60 20 80 40 2 (5.0 - 9.9)HQTT4 (14.5-18.8)6 (23.8 - 28.8)73 (9.9-14.5)5 (18.8-23.8)W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Run 7 from 28.8 to 30.0 ft THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF ACTUAL CONDITIONS ENCOUNTERED. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 8 of 9 0 2 4 6 8 5 10 15 20 25 30 35 40 45 60 20 80 40 60 20 80 40 55 502 (5.0 - 9.9)HQTT4 (14.5-18.8)6 (23.8 - 28.8)73 (9.9-14.5)5 (18.8-23.8)W1 W5 W9 W3 W7 Testing Notes: Drilling Rate Blocking Water loss Stetson Ck./Cooper Lk ELEVATION 1205.9 ft DRILLING CONTRACTOR: Discovery Drilling, Inc. Northwestern Spillway INCLINATION Vertical RIG: CME 850 - Track Mounted N 2350508.4 DIRECTION N/A START: July 10, 2010 E 531822.8 LOGGED BY P. Richards FINISH: July 10, 2010 GEOLOGICAL TESTING J 60 SLATE: Dark gray, fine grained, slightly weathered to J/MB 65/60 fresh (W2), moderately hard (H4), intensely to 100 54 J/MB 60/20,0 moderately fractured (FD6); Discontinuities are S 35,65 moderately to closely spaced (SP3 to SP4), tight to 100 55 J/MB 45/30 moderately open (O0 to O2), clean to very thinly filled (T0 to T1), partly healed (HL3), slightly rough (R4), J 35,50 predominately dip at 30 to 65 degrees, and are 100 88 J/MB 50,55/45 occasionally slickensided. J/MB 40,55,80/40 -Very intensely fractured (FD9) from 0.0 to 0.9 feet. J 40 -3/4-inch thick silty clay infilling at 3.8 ft.Blocked off at S/J 50,65/50,70 3.9 ft. 100 58 J 50,70 J/MB 50,65/0 J/MB 50/30 J/MB 20,30,70/0 J 20,30,65,70 -Very intensely fractured (FD9) at 16.0 to 16.1 ft. 90 33 -Very intensely fractured (FD9) at 17.6 to 18.5 ft. J 30 J 20,50 J 60 100 96 MB 40 J/MB 50 100 0 J 50 Blocked off at J 50 25.2 ft. 100 100 MB 10 J 40,50 Terminal Depth = 30.0 ft DRAFT LOG OF COREHOLE NO. B-5 PROJECT LOCATION COORDINATES (ft) Description DiscontinuitiesDegree of Weathering Discont./ft. Type DipGeology Run No. (Start - Stop)BitRecovery (%)RQD (%)Depth 0 2 4 6 8 5 10 15 20 25 30 35 60 20 80 40 60 20 80 40 Testing Notes: Drilling Rate Blocking Water loss 2HQTT5 (14.5-20.0)77(28.8-30.0)3 (5.0 - 10.0)6 (20.0 - 25.0)1(0.0 - 3.9)4 (10.0 - 14.5)8 (25.2 - 30.0) W1 W5 W9 W3 W7 Notes: Run 2 from 3.9 to 5.0 ft Run 7 from 25.0 to 25.2 ft THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF ACTUAL CONDITIONS ENCOUNTERED. PROJECT NO. 1007059 CHUGACH ELECTRIC ASSOCIATION STETSON CREEK DIVERSION AND COOPER LAKE OUTLET KENAI BOROUGH, ALASKA PAGE 9 of 9 0 2 4 6 8 5 10 15 20 25 30 35 40 45 60 20 80 40 60 20 80 40 55 50 Testing Notes: Drilling Rate Blocking Water loss 2HQTT5 (14.5-20.0)77(28.8-30.0)3 (5.0 - 10.0)6 (20.0 - 25.0)1(0.0 - 3.9)4 (10.0 - 14.5)8 (25.2 - 30.0) W1 W5 W9 W3 W7 APPENDIX V Selected Historical Exploration Logs APPENDIX VI 2009 Laboratory Testing Program and Results Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1 of 2 Geotechnical Baseline Report – Final – Appendix VI May 2012 APPENDIX VI 2009 LABORATORY TESTING PROGRAM AND RESULTS The 2009 geotechnical laboratory soil testing was conducted by Duane Miller Associates of Anchorage, Alaska. Corrosion-related analytical laboratory testing was submitted to TestAmerica Inc. (TAI) of Anchorage, Alaska. TAI’s corrosion testing was conducted in their Beaverton, Oregon, Laboratory. All tests were conducted in accordance with applicable ASTM or U.S. Environmental Protection Agency (EPA) testing standards. Descriptions of the laboratory tests conducted on selected soil samples are presented below. Test results are summarized in the 2009 exploration logs in Appendix III and are detailed in the following pages. Moisture Testing Moisture content tests were performed on a number of samples recovered from the test pits. The results of these tests were used to aid in evaluating soil properties. Moisture content tests were conducted in accordance with ASTM D 2216. Sieve Analysis Sieve analyses (combined sieve with hydrometer analyses) were performed on selected samples of the subsurface materials. These tests were performed to evaluate the gradation characteristics of the soils and to aid in their classification. These tests were performed in accordance with ASTM D 422. Atterberg Limits Testing (Liquid Limit, Plastic Limit and Plasticity Index) Atterberg limits are used primarily for classifying and indexing cohesive soil. The liquid and plastic limits, which are defined as the moisture content of a cohesive soil at established limits for liquid and plastic behavior, respectively, were determined for a core material sample from Cooper Lake Dam. Atterberg limits testing was conducted in accordance with the guidelines presented in ASTM D 4318. Plasticity Index (PI) is defined as the difference in water content between the liquid limit (LL) and plastic limit (PL). Soil Classification Visual soil classifications were conducted on all soil samples in the field and confirmed with laboratory testing. All soils were classified in accordance with the Unified Soil Classification System as described by ASTM D 2487 and ASTM D 2488 as appropriate, which includes: stiffness/ relative density, color, major soil type (based on grain size), minor soil types, and relative moisture content. Classifications and sampling intervals are shown in the test pit exploration logs presented in Appendix III of this report. The logs indicate the depths at which the soils or their characteristics change at the location of the exploration, although the changes may actually be gradual. If the change occurred between sample locations, the depth of change was interpreted. Page 2 of 2 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix VI This page is intentionally blank.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        APPENDIX VII 2010 Laboratory Testing Program and Results Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 1 of 4 Geotechnical Baseline Report – Final – Appendix VII May 2012 APPENDIX VII 2010 LABORATORY TESTING PROGRAM AND RESULTS Primary geotechnical laboratory testing of soil and aggregate was conducted by Terra Firma Testing, Inc. of Anchorage, Alaska. Additional confirmation testing of selected soil samples was conducted by ACS Testing, Inc. of Tigard, Oregon. Rock core testing was conducted by Cooper Testing Labs, Inc. of Palo Alto, California. All tests were conducted in accordance or in general accordance with applicable ASTM standards. Descriptions of the laboratory tests conducted on selected soil samples are presented below. Test results are summarized in the exploration logs in Appendix IV and are detailed in the following pages. California Modified Split Spoon Penetration Tests California Modified split spoon penetration tests were conducted in regular intervals within soil substrates in general accordance with methods prescribed by ASTM for Standard Penetration Testing (ASTM D1586). The test involves driving a 3-inch outside diameter split spoon sampler for three intervals of six inches using a 340-lb auto hammer with a drop height of 30 inches. The number of hammer blows required to drive the sample each 6-inch interval is recorded, and the sum of the blow counts over the second and third interval is presented as a raw blow count or “N-value”. This raw value can then be related to standard penetration test N-values using relationships such as that presented by LaCroix and Horn (1973). Water Pressure Testing Water pressure testing was performed in two rock core borings located at the proposed diversion dam. The tests were performed of a selected interval that was isolated from the remainder of the boring using a pneumatic, rubber seal packer. Each of the water pressure tests were comprised of five pressure stages: Stage 1 – 5 psi; Stage 2 – 10 psi; Stage 3 – 15 psi; Stage 4 – 10 psi; and Stage 5 – 5 psi. The water flow for each stage was measured from an analog water meter and recoded manually. The data from each test is presented in Lugeons, a unit of permeability used to evaluate rock groutability and the effectiveness of grouting programs in rock. One Lugeon is defined as 1 liter (0.26 gallons) of water loss per minute, per meter (3.28 ft) of bore hole at a pressure of 1 megapascal (145 psi). Moisture Testing Moisture content tests were performed on a number of samples recovered from the test pits. The results of these tests were used to aid in evaluating soil properties. Moisture content tests were conducted in accordance with ASTM D 2216. Sieve Analysis Sieve analyses (combined sieve with hydrometer analyses and material passing a US Standard No. 200 sieve) were performed on selected samples of the subsurface materials. These tests were performed to evaluate the gradation characteristics of the soils and to aid in their classification. These tests were performed in accordance with ASTM D 422 and ASTM D 1140. Page 2 of 4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix VII Atterberg Limits Testing (Liquid Limit, Plastic Limit and Plasticity Index) Atterberg limits are used primarily for classifying and indexing cohesive soil. The liquid and plastic limits, which are defined as the moisture content of a cohesive soil at established limits for liquid and plastic behavior, respectively, were determined for a core material sample from Cooper Lake Dam. Atterberg limits testing was conducted in accordance with the guidelines presented in ASTM D 4318. Plasticity Index (PI) is defined as the difference in water content between the liquid limit (LL) and plastic limit (PL). Soil Classification Visual soil classifications were conducted on all soil samples in the field and confirmed with laboratory testing. All soils were classified in accordance with the Unified Soil Classification System as described by ASTM D 2487 and ASTM D 2488 as appropriate, which includes: stiffness/ relative density, color, major soil type (based on grain size), minor soil types, and relative moisture content. Classifications and sampling intervals are shown in the exploration logs presented in Appendix IV of this report. The logs indicate the depths at which the soils or their characteristics change at the location of the exploration, although the changes may actually be gradual. If the change occurred between sample locations, the depth of change was interpreted. Unconfined Rock Strength The unconfined strength and elastic modulus of intact rock core samples was tested on four selected samples. This test was used to determine the compressive strength and deformation properties of intact rock core samples. These tests were conducted in accordance with ASTM D 7012. Direct Shear Strength of Rock Direct shear strength of rock was conducted on a selected saw-cut core sample. This test was conducted to approximate the minimum shear strength of the rock along existing joints within the rock mass. This test was conducted in accordance with ASTM D 5607. Petrographic Examination of Aggregates A petrographic examination of a selected bulk sample was conducted on a sample collected at the ground surface at the location of a proposed borrow area. The petrographic examination was used to determine the chemical and mineral characteristics of the bulk sample to aid in the evaluation of the aggregates suitability for use on the proposed Project. The petrographic examination was conducted in accordance with ASTM C 295. Los Angeles Abrasion of Aggregates A Los Angeles Abrasion test was conducted on one bulk sample collected at the ground surface within the proposed borrow areas. This test method evaluates the aggregates resistance to abrasion using a standardized testing machine. Los Angeles abrasion testing was conducted in accordance with ASTM C 131/C 535. Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities Page 3 of 4 Geotechnical Baseline Report – Final – Appendix VII May 2012 Soundness of Aggregates The soundness of a selected bulk sample was evaluated to determine the aggregate’s resistance to weathering. The selected bulk sample was collected at the ground surface at the location of a proposed borrow area. This test simulates the effect of weathering by subjecting the sample to either sodium sulfate or magnesium sulfate for a minimum of five cycles. The soundness of aggregate testing was conducted in accordance with ASTM C 88. Page 4 of 4 Stetson Creek Diversion and Cooper Lake Dam Outlet Facilities May 2012 Geotechnical Baseline Report – Final – Appendix VII This page is intentionally blank.