DGeo Cap Sante Boat Haven M, N, O-Dock Maintenance Dredge Project Anacortes, Washington for Port of Anacortes June 7, 2012 Earth Science + Technology
Geotechnical Engineering Services Snoqualmie Switch Station Snoqualmie, Washington for Puget Sound Energy March 25, 2013 Plaza 600 Building 600 Stewart Street, Suite 1700 Seattle, Washington 98101 206.728.2674
Table of Contents INTRODUCTION AND SCOPE... 1 FIELD EXPLORATION AND LABORATORY TESTING... 1 Field Explorations... 1 SITE CONDITIONS... 1 Sensitive Areas... 1 Geology... 2 Surface Conditions... 2 Subsurface Conditions... 2 CONCLUSIONS AND RECOMMENDATIONS... 2 Seismic Design... 2 IBC Design Parameters... 2 Shallow Foundations and Mat Foundations... 3 Allowable Soil Bearing Pressure... 3 Embedment... 3 Settlement... 3 Lateral Resistance... 4 Construction Considerations... 4 Retaining Walls... 4 General... 4 Design Parameters... 5 Wall Drainage... 5 Global Stability Analyses... 5 Storm Drain Pipe... 5 Slope Stability... 5 Steep Slope Construction Recommendations... 6 Earthwork... 7 Excavation Considerations... 7 Clearing and Grubbing... 7 Subgrade Preparation... 7 Erosion and Sedimentation Control... 7 Structural Fill... 8 Weather Considerations... 9 Temporary Slopes... 10 Permanent Slopes... 10 LIMITATIONS... 11 REFERENCES... 11 March 25, 2013 Page i File No. 0186-679-10
Table of Contents (continued) LIST OF FIGURES Figure 1. Vicinity Map Figure 2. Site Plan Figure 3. Global Stability Analysis Static and Seismic Conditions APPENDICES Appendix A. Field Explorations Figure A-1. Key to Exploration Logs Figures A-2 through A-8. Logs of Borings Appendix B. Report Limitations and Guidelines for Use Page ii March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington INTRODUCTION AND SCOPE This report summarizes the results of our geotechnical engineering services for the proposed improvements to the existing Puget Sound Energy (PSE) Snoqualmie Switch Station. The site is located east of Salish Lodge off Railroad Avenue in Snoqualmie, Washington. The site is shown in relation to the surrounding area on the Vicinity Map, Figure 1, and the Site Plan, Figure 2. We previously issued a draft of this report dated March 15, 2015; this report supersedes our previous report. We understand that the proposed improvements include bringing in underground feeder lines from Snohomish County Public Utility District run-of-the-river hydroelectric projects at Hancock Creek and Calligan Creek. These underground feeders will enter from the north and tie into the existing PSE switch station using a new regulator, transformer, and breaker switch, which will be located at the east end of the existing station. The improvements will require expansion onto the steep slope to the east, including a new retaining wall that will be approximately 2 to 9 feet high. Due to space limitations, the retaining wall will likely be a reinforced concrete wall. The proposed improvements will include modifications to the existing storm drainage system, including a new catch basin behind the retaining wall and a new drain pipe extending south down the steep slope and connecting to an existing catch basin that discharges into the Snoqualmie River. The approximate locations of the proposed improvements are shown on the attached Site Plan, Figure 2. Our geotechnical engineering services were completed in general accordance with our proposal dated February 12, 2013. Our scope of service includes: Completing four borings and three hand-augered borings at the site; Providing geotechnical conclusions and recommendations for the proposed improvements, and Preparing this report. FIELD EXPLORATION AND LABORATORY TESTING Field Explorations The subsurface conditions at the site were evaluated by completing four borings (B-1 through B-4) to depths ranging from 11½ to 14 feet below existing site grades, and three hand-augered borings (HA-1 through HA-3). The approximate locations of the explorations are shown on the Site Plan, Figure 2. A detailed description of the field exploration program is presented in Appendix A. SITE CONDITIONS Sensitive Areas We reviewed the available sensitive areas maps published online by King County. The maps include identification of areas with significant landslide, seismic, erosion, and coal mine hazards. No geologic sensitive areas are mapped in the vicinity of the proposed switch station improvements; however, based on the slope inclination, the steep slope would be characterized as an erosion and steep slope hazard area. March 25, 2013 Page 1 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Geology Geologic information for the project area (Dragovich, Joe D., Littke, Heather A., Anderson, Megan L., et al., 2009) indicates that surficial soils mapped at the site consist of glaciolacustrine deposits and alluvium underlain by bedrock. Glaciolacustrine deposits generally consist of silt, clayey or sandy silt, and silty sand, typically with scattered dropstones and occasional layers and lenses of sand and/or gravel. Alluvium generally consists of well sorted/stratified sand and silt with lesser gravelly sand, sandy pebble gravel, peat, and organic sediments. The glaciolacustrine deposits or alluvium is underlain by bedrock (Volcanic rocks of Snoqualmie Falls - Miocene). Surface Conditions The site is bounded by Railroad Avenue to the north, Salish Lodge to the west, a paved surface parking lot to the east, and a construction access road to the south. The ground surface slopes down from the north where it is about Elevation 446 feet, to about Elevation 416 feet at the south margin of the site. The area of the proposed improvements is currently undeveloped and forested with deciduous and coniferous trees and brush. Subsurface Conditions Based on the explorations performed at the site, the subsurface conditions generally consist of topsoil and fill overlying glaciolacustrine deposits. We observed approximately 4 to 6 inches of topsoil in most of the explorations. The topsoil generally consists of forest duff and organic soil. Below the topsoil, we observed fill consisting of loose to medium dense silty sand/sandy silt with organics (fine roots, charcoal) and varying gravel content to a depth of approximately 3 to 7 feet. Below the fill, we observed glaciolacustrine deposits consisting of very stiff to hard silt with variable amounts of gravel. The glaciolacustrine deposits extended to the depths explored. Bedrock was not encountered in the explorations. No groundwater was observed during drilling. These observations may or may not be representative of the long-term groundwater conditions at the site. CONCLUSIONS AND RECOMMENDATIONS Seismic Design IBC Design Parameters We recommend the 2012 International Building Code (IBC) parameters for Site Class, short period spectral response acceleration (SS), one-second period spectral response acceleration (S1) and Seismic Coefficients FA and FV presented in the following table. Page 2 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington 2012 IBC SEISMIC PARAMETERS 2012 IBC Parameter Recommended Value Site Class C Short Period Spectral Response Acceleration, SS (percent g) 1.14 1-Second Period Spectral Response Acceleration, S1 (percent g) 0.43 Seismic Coefficient, FA 1.0 Seismic Coefficient, FV 1.37 We evaluated the site for seismic hazards including liquefaction, lateral spreading, fault rupture and earthquake-induced slope instability. Our evaluation indicates that the site does not have liquefiable soils present and therefore also has no risk of liquefaction-induced lateral spreading. In addition, the site has a low risk of fault rupture. Shallow Foundations and Mat Foundations Allowable Soil Bearing Pressure The proposed switch station equipment may be supported on conventional shallow spread footings or mat foundations bearing either on the native soils or on properly compacted structural fill placed over the native soils. The mat foundations and spread footings, where required, may be designed using an allowable soil bearing pressure of 4,000 pounds per square foot (psf). The allowable soil bearing value applies to the total of dead and long-term live loads and may be increased by up to one-third when considering total loads including transient loads such as wind or seismic forces. A subgrade modulus of 200 pounds per cubic inch (pci) may be used for the design of mat foundations. The retaining wall footing can be designed using the same parameters presented above, except we recommend the footing bear on undisturbed native soils or controlled density fill (CDF) placed over the native soils. Embedment In general, we recommend that the bottom of foundations be embedded at least 18 inches below the lowest adjacent grade for frost protection. The foundation embedment depth may be reduced to 12 inches for small, lightly loaded footings where frost action will not affect equipment performance, or an additional 6-inch-thick layer of gravel that is not susceptible to frost may be placed below the foundations to achieve an embedment of 18 inches. The retaining wall embedment is discussed separately in the Retaining Walls section. Settlement Provided all loose soil is removed and the subgrade is prepared and evaluated as recommended below in the Construction Considerations section, we estimate that the total settlement of shallow and mat foundations will be on the order of ½ to 1 inch. Differential settlements are expected to be less than ½ inch. March 25, 2013 Page 3 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Lateral Resistance Lateral foundation loads can be resisted by passive resistance on the sides of foundations and by friction on the base of the foundations. For foundations supported on native soils or on structural fill placed and compacted in accordance with our recommendations, the allowable frictional resistance can be computed using a coefficient of friction of 0.35 applied to vertical dead-load forces. The allowable passive resistance can be computed using an equivalent fluid density of 300 pounds per cubic foot (pcf) (triangular distribution) if these elements are poured directly against compacted native soils or surrounded by structural fill. The structural fill should extend out from the face of the foundation element for a distance at least equal to three times the height of the element and be compacted to at least 95 percent of the maximum dry density (MDD) estimated in general accordance with American Society for Testing and Materials (ASTM) D 1557. For the retaining wall footing, due to the descending slope in front of the wall, passive resistance should be neglected. The above coefficient of friction and passive equivalent fluid density values incorporate a factor of safety of about 1.5. Construction Considerations If soft soil areas are present at the foundation bearing surface elevation, the soft soils in these areas must be removed and replaced with structural fill. In such instances, the zone of structural fill must extend laterally beyond the footing edges for a horizontal distance that is at least equal to the depth of overexcavation. For the retaining wall footing, soft soil areas below the foundation subgrade elevation must be removed and replaced with CDF. The overexcavated areas must be neat-cut to limit the extent of the excavation and limit disturbance of the soils at the face of the retaining wall. We recommend that a representative from our firm observe the condition of all footing excavations to evaluate whether the work is completed in accordance with our recommendations and whether the subsurface conditions are as anticipated. Retaining Walls General The proposed improvements will require expansion onto the steep slope to the east, and the grade transition will be accomplished by using a reinforced concrete retaining wall up to 9 feet in height. Based on our explorations, we anticipate overexcavation will be required in some areas below the retaining wall footing. Loose soils must be overexcavated and backfilled with CDF, as discussed in the previous section. Retaining walls must be backfilled with a 12-inch wide zone of drainage aggregate, with weep pipes extending to the face of the wall. The retaining wall must have a minimum of 24 inches of embedment at the face of the wall for wall heights up to 4 feet and a minimum of 36 inches of embedment at the face of the wall for wall heights greater than 4 feet. Page 4 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Design Parameters We recommend the retaining wall be designed using the parameters presented in the table below. The retaining wall foundations may be designed using the recommendations previously presented in the Shallow Foundations and Mat Foundations section. The parameters listed below assume drainage is provided as described in the Wall Drainage section below. Soil Parameters Unit Weight (pcf) 125 Friction Angle (degrees) 35 Seismic Coefficient, Kh 0.15 Active Earth Pressure (pcf) triangular distribution Seismic Pressure (psf) uniform distribution Retained Soils 31H 6H Wall Drainage We recommend drainage for the retaining wall be provided by placing a 12-inch-wide zone of free-draining soil behind the wall (base course or yard course meet this requirement) and installing weepholes. Permanent drainage systems must intercept surface water runoff at the top and/or bottom of cut and fill slopes to prevent the surface water from flowing in an uncontrolled manner across the wall. Global Stability Analyses We performed slope stability analyses to evaluate the global static and seismic (pseudostatic) stability of the proposed retaining wall. For our analyses, we used the slope stability program Slope/W 2012. Soil strength parameters for the slope stability analysis were selected by reviewing the exploration logs and from our professional judgment based on the geologic origin of the soil units. A ground acceleration of 0.15g (where g is the gravitational constant) was used for seismic (pseudostatic) analysis. This ground acceleration corresponds to 50 percent of the effective IBC design ground acceleration, which is assumed equal to the design spectral response acceleration (SDS) divided by 2.5, per Section 1803.5.12 of the IBC, where SDS is determined in accordance with Section 1613.5.4 of the IBC. Figure 3 presents the modeled soil strength parameters and slope geometry, along with the static and seismic factors of safety and resulting critical failure surface. The global factor of safety for the slopes is at least 1.5 for static conditions and at least 1.1 for seismic conditions. Based on our slope stability analyses and geotechnical evaluation, it is our opinion that the proposed retaining wall has adequate factors of safety for global stability. Storm Drain Pipe Slope Stability Based on our field observations, subsurface explorations, and experience, it is our opinion that the steep slope is susceptible to surficial soil movement. It is our opinion that the upper weathered soil layer on the slope may move slowly downslope via raveling and soil creep. Instability of this nature is confined to the upper weathered or disturbed zone of soil, which typically has lower March 25, 2013 Page 5 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington strength than the underlying unweathered soil. This process is more significant on steeper slopes than on flatter slopes. Significant weathering typically occurs in the upper 2 to 3 feet and is the result of oxidation, root penetration, wet/dry and freeze/thaw cycles, and gravity. Erosion of the soils on the steep slope can be managed and effectively reduced through proper erosion control practices and surface restoration methods that are described in the Earthwork section of this report. We recommend that the storm drain pipe be installed aboveground to limit potential impacts from slope movement. Recommendations for construction of the storm drain pipe in the steep slope area are presented below. Steep Slope Construction Recommendations The aboveground portion of the pipe should extend from an anchor point behind the retaining wall onto the face of the slope. The pipe should be butt-fuse welded into a continuous section of pipe, without joints. Because the soils surrounding the pipe can experience movement, we recommend that the pipe be straight and oriented perpendicular to the contours on the face of the slope. This will reduce the loads that the soil movement could impose on the pipe, as compared with a pipe running cross-slope. In addition, the pipe will likely experience some loss of support from surficial soil movement. Therefore, we recommend that the pipe be anchored securely at the top of the slope. We recommend against mid-slope anchorage of the pipe because any soil movement near the midslope anchors could cause distress to the pipe at the anchorage points. In our opinion, high density polyethylene (HDPE) pipe is appropriate for this project because the flexibility of the pipe will enable the pipe to withstand bending stresses if there is some loss of support. The HDPE pipe should be anchored at the top of the slope with a structure designed to restrain the full weight of the pipe, plus the full weight and hydrodynamic loads of the designed stormwater contained within the pipe. We recommend that the anchorage be achieved by means of a structure of sufficient size or a structure plus a dead-man block of concrete. A manhole can be used for this structural anchorage, provided that the manhole has sufficient face area and the structural capacity to transmit the loads from the pipe into the ground. The pipe anchorage should be positioned behind the retaining wall. The anchor should be fully embedded in undisturbed dense native soil or structural fill. It may be possible to design the retaining wall as the anchorage, provided the retaining wall is properly designed for the increased lateral loads. The capacity of the pipe anchorage can be evaluated using the parameters presented in the Shallow Foundations and Mat Foundations section. Lateral loads can be resisted by a combination of friction between the base of the anchor and the supporting soil, and by the passive lateral resistance of the soil at the face of the anchor. Page 6 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Earthwork Excavation Considerations Topsoil, fill, and glaciolacustrine deposits were observed in the explorations. We anticipate that these soils can be excavated with conventional excavation equipment, such as trackhoes or dozers. Cobbles and boulders were encountered in the soils at the site, and the contractor should be prepared to remove them where necessary. Bedrock is anticipated to be present below the glaciolacustrine deposits, although explorations at the site did not extend to the bedrock. Clearing and Grubbing Trees, brush, and other vegetation, including topsoil with roots, should be stripped and removed from areas where structural fill will be placed. The stripped material should be placed in landscaping areas or transported off-site for disposal. Subgrade Preparation In areas where structural fill is to be placed, the upper 12 inches of existing subgrade soils must be evaluated prior to fill placement. This can be done by probing. Likewise, the bearing surface in the proposed foundation areas for structures and retaining walls must be evaluated after site grading is complete. Soft zones noted during probing must be overexcavated and replaced with compacted structural fill or CDF. Erosion and Sedimentation Control Potential sources or causes of erosion and sedimentation depend upon construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. The project impact on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. The plan should incorporate basic planning principles, including: Scheduling grading and construction to reduce soil exposure; Retaining existing vegetation whenever feasible; Revegetating or mulching denuded areas; Directing runoff away from denuded areas; Minimizing the length and steepness of slopes with exposed soils; Decreasing runoff velocities; Confining sediment to the project site, and; Inspecting and maintaining control measures frequently. We recommend that graded and disturbed slopes be tracked in place with the equipment running perpendicular to the slope contours so that the track marks provide a texture to help resist erosion and channeling. Some sloughing and raveling of slopes with exposed or disturbed soil should be expected. March 25, 2013 Page 7 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Temporary erosion protection must be used and maintained in areas with exposed or disturbed soils to help reduce the potential for erosion and reduce transport of sediment to adjacent areas. Temporary erosion protection must include the construction of a silt fence around the perimeter of the work area prior to the commencement of grading activities. Permanent erosion protection must be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established and the site is stabilized, site monitoring must be performed by qualified personnel to evaluate the effectiveness of the erosion control measures and repair and/or modify them as appropriate. Provisions for modifications to the erosion control system based on monitoring observations must be included in the erosion and sedimentation control plan. Structural Fill MATERIALS Materials used to raise site grades, placed to support structures or pavements, or used for utility trench backfill are classified as structural fill for the purpose of this report. Structural fill material quality varies depending upon its use as described below: On-site soils must not be used as structural fill to support switch station equipment. On-site soils may be considered for use as structural fill for other purposes during dry weather. On-site soils may also be used during wet weather provided that they can be moisture-conditioned to meet compaction specifications. If on-site soils cannot be moisture-conditioned, imported gravel borrow must conform to Puget Sound Energy Base Course Aggregate Specification 1275.1310 as described in the following table: US Standard Sieve Size 3 inches 100 ¾ inch 70-90 ⅜ inch 60-80 ¼ inch 50-70 U.S. No. 40 < 30 U.S. No. 200 Percent Passing (by weight) 5 maximum Structural fill placed as yard course crushed aggregate surfacing material must be angular crushed rock conforming to Puget Sound Energy Specification 1275.1330 as described in the following table: US Standard Sieve Size 1½ inches 100 1 inch 60 to 100 ¾ or ⅝ inch 0 to 35 ⅜ inch 0 to 5 Percent Passing (by weight) Page 8 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington FILL PLACEMENT AND COMPACTION CRITERIA Structural fill must be mechanically compacted to a firm, non-yielding condition. In general, structural fill must be placed in loose lifts not exceeding 8 to 10 inches in thickness. Each lift must be conditioned to the proper moisture content and compacted to the specified density before placing subsequent lifts. Structural fill must be compacted to the following criteria: Structural fill placed below foundations and roadways or to establish yard grades must be compacted to at least 95 percent of the MDD estimated in general accordance with ASTM D 1557. Structural fill placed to form finished slopes must also be compacted to at least 95 percent of the MDD. Structural fill (including utility trench backfill) placed outside of areas where foundations, roadways, parking and yard areas are to be located must be compacted to at least 90 percent of the MDD estimated in general accordance with ASTM D 1557. We recommend that a representative from our firm be present during proof-rolling and/or probing of the exposed subgrade soils in structure areas prior to the placement of structural fill and also during the placement of structural fill. Our representative will evaluate the adequacy of the subgrade soils and identify areas needing further work, perform in-place moisture-density tests in the fill to evaluate whether the work is being done in accordance with the compaction specifications, and advise on any modifications to procedures that may be appropriate for the prevailing conditions. Weather Considerations The native soils contain a sufficient percentage of fines (silt) and are moisture-sensitive. When the moisture content of these soils is appreciably above the optimum moisture content, these soils become muddy and unstable, operation of equipment on these soils will be difficult and it will be difficult to meet the required compaction criteria. Additionally, disturbance of these near-surface soils should be expected if earthwork is completed during periods of wet weather. The wet weather season in the Puget Sound region generally begins in October and continues through May; however, periods of wet weather can occur during any month of the year. The optimum earthwork period for these types of soils is typically June through September. If wet weather earthwork is unavoidable, we recommend that: Stockpiles of on-site soils that will be used as structural fill during wet weather be covered with plastic sheeting to protect them from rain. If on-site soils cannot be moisture-conditioned to meet compaction requirements during wet weather, imported gravel borrow must be used as discussed previously in the Structural Fill section of this report. The ground surface in and around the work area be sloped so that surface water is directed away from the work area. The ground surface must be graded such that areas of ponded water do not develop. The contractor must take measures to prevent surface water from collecting in excavations and trenches. Measures must be implemented to remove surface water from the work area. March 25, 2013 Page 9 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Temporary Slopes The soils encountered at the site are classified as Type C soil in accordance with the provisions of Title 296-155 of the Washington Administrative Code (WAC), Part N, Excavation, Trenching, and Shoring. We recommend that temporary slopes in excess of 4 feet in height be inclined no steeper than 1H:1V. Flatter slopes may be necessary if localized sloughing occurs. For open cuts at the site, we recommend that: No traffic, construction equipment, stockpiles or building supplies be allowed at the top of cut slopes within a distance of at least 5 feet from the top of the cut. Exposed soil along the slope be protected from surface erosion using waterproof tarps or plastic sheeting. Construction activities be scheduled so that the length of time that the temporary cut is left open is kept as short as possible. Erosion control measures be implemented as appropriate such that runoff from the site is reduced to the extent practicable. Surface water be diverted away from the excavation. The general condition and stability of the slopes be visually assessed periodically by a geotechnical engineer. Because the contractor has control of the construction operations, the contractor must be made responsible for the stability of all temporary slopes, as well as the safety of the excavations. All shoring and temporary slopes must conform to applicable local, state and federal safety regulations. Permanent Slopes We recommend that permanent cut and fill slopes be constructed no steeper than 2H:1V. To achieve uniform compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to expose properly compacted fill. Fill placed on existing slopes that are steeper than 5H:1V must be properly keyed into the native soil slope surface. This can be done by constructing the fill in a series of 6- to 8-foot-wide horizontal benches cut into the slope. Bench surfaces must be thoroughly compacted prior to placing the fill soils. To reduce erosion, newly constructed slopes must be planted or hydroseeded shortly after completion of grading. Until the vegetation is established, some sloughing and raveling of the slopes should be expected. This may require localized repairs and reseeding. Temporary covering, such as clear heavy plastic sheeting, jute fabric, loose straw or excelsior matting must be used to protect the slopes during periods of rainfall. Page 10 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington LIMITATIONS We have prepared this report for the exclusive use of Puget Sound Energy and their authorized agents for the proposed Snoqualmie Switch Station Improvements in Snoqualmie, Washington. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record. Please refer to Appendix B, Report Limitations and Guidelines for Use, for additional information pertaining to use of this report. REFERENCES International Code Council, International Building Code. 2012. Dragovich, Joe D., Littke, Heather A., Anderson, Megan L., et al., 2009, Geologic map of the Snoqualmie 7.5-minute quadrangle, King County, Washington, Washington Division of Geology and Earth Resources Geologic Map GM-75. King Country GIS database. URL: http://www.metrokc.gov/gis/mapportal/imap_main.htm. United States Geological Survey, U.S. Seismic Design Maps, 2008 data, accessed on 3/12/13 at: http://geohazards.usgs.gov/designmaps/us/application.php. March 25, 2013 Page 11 File No. 0186-679-10
Type Name of Services Here Name of Project Here for Type Client Name Here Type Date of Report Here Earth Science + Technology
SE Tokul Rd SE 47Th St 358Th Ave SE Mud C SE 49Th St rreek SE David Powell Rd 365Th Ave SE Fish Hatchery Rd SE 47Th Pl 371St Ct SE 372Nd Ave SE UV202 Tokul Creek SE 53Rd St SE 56Th St Office: Redmond Path: \\red\projects\0\0186679\gis\018667910_f1_vicinitymap.mxd Map Revised: 3/14/2013 EL Kitsap Pierce 5 405 Seattle Bellevue UV 167 364Th Ave SE Snohomish King 90 Preston Snoqualmie Trl SE 80Th St Snoqualmie River SE Gravenstein Ct SE 82Nd St SE 86Th St Kittitas 372Nd Pl SE Coa 376Th Ave SE ll C r reek SE 88Th St Notes: 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. 3. It is unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without permission. Data Sources: ESRI Data & Maps, Street Maps 2005 Transverse Mercator, Zone 10 N North, North American Datum 1983 North arrow oriented to grid north Site 378Th Ave SE SE 77Th St K imba l l l l C rree kk i Stearns Rd 382Nd Ave SE Railroad Pl SE SE Cedar St SE 85Th St 384Th Ave SE 4Th St Silva St SE 60Th St King St 2Nd Ave NW Mill Pond Rd Snoqua l lm i ie R Railroad Pl SE ive rr i River View Park Alpha St Falls Ave SE µ Vicinity Map SE Park St Snoqualmie Switch Station Snoqualmie, Washington Borst Lake 2,000 0 2,000 Feet 402Nd Ave SE SE 60Th St 396Th Ave SE SE 70Th Dr Figure 1 396Th Dr SE Three Forks P Meadowbrook S
Legend B-1 HA-1 Boring by GeoEngineers Hand Auger by GeoEngineers B-3 B-4 N B-1 B-2 W S E 20 0 20 HA-3 FEET HA-1 HA-2 Notes 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Reference: CAD file "SK-056401.dwg" provided by PSE on 3-4-13. Site Plan Snoqualmie Switch Station Snoqualmie, Washington Figure 2
SharePoint Working\Figure 3 Slope Stability Analyses.ppt HPD:tb2 03/08/13 Not to Scale Global Stability Analysis Static and Seismic Conditions Snoqualmie Switch Station Snoqualmie, Washington Figure 3
Type Name of Services Here Name of Project Here for Type Client Name Here Type Date of Report Here Earth Science + Technology
APPENDIX A Field Explorations
SNOQUALMIE SWITCH STATION Snoqualmie, Washington APPENDIX A FIELD EXPLORATIONS Field Explorations Subsurface conditions were explored at the site by completing four borings (B-1 through B-4), and three hand-augered borings (HA-1 through HA-3). The borings were completed by Geologic Drill Exploration Inc of Bellevue, Washington, on February 22, 2013. The locations of the explorations were estimated in the field by measuring distances from site features through taping and pacing. The approximate locations of the explorations are shown on the Site Plan, Figure 2. Exploration elevations were estimated based on a site plan (SK-056401.dwg) provided by Puget Sound Energy on March 4, 2013. Borings The borings were drilled using a hand-portable hollow-stem auger drill rig. The borings were continuously observed by a geotechnical engineer from our firm who examined and classified the soils encountered, collected soil samples, observed groundwater conditions and prepared a detailed log of each boring. The soils encountered in the borings were sampled with a 2-inch outside diameter split-barrel standard penetration test (SPT) sampler or with a 3-inch diameter Shelby tube sampler. The SPT samples were obtained by driving the sampler 18 inches into the soil with a 140-pound hammer free-falling 30 inches. The number of blows required for each 6 inches of penetration was recorded. The blow count ("N-value") of the soil was calculated as the number of blows required for the final 12 inches of penetration. This resistance, or N-value, provides a measure of the relative density of granular soils and the relative consistency of cohesive soils. Where very dense soil conditions precluded driving the full 18 inches, the penetration resistance for the partial penetration was entered on the log. The blow counts are shown on the boring logs at the respective sample depths. The Shelby tube sampler was pushed into the soft peat to collect relatively undisturbed samples for laboratory consolidation testing. Soils encountered in the borings were visually classified in general accordance with the classification system described in Figure A-1. A key to the exploration log symbols is also presented in Figure A-1. The logs of the borings are presented in Figures A-2 through A-4. The logs reflect our interpretation of the field conditions and the results of laboratory testing and evaluation of samples. They also indicate the depths at which the soil types or their characteristics change, although the change might actually be gradual. The borings were backfilled in accordance with Department of Ecology standards. No groundwater was observed during drilling. These observations may or may not be representative of the longterm groundwater conditions at the site. Hand-Augered Borings Hand-augered borings were completed using hand tools. The hand-augered borings were completed by GeoEngineers, Inc on February 22, 2013 and were continuously monitored by a representative from our firm who examined and classified the soils encountered, obtained representative soil samples, observed groundwater conditions and prepared a detailed log of each exploration. March 25, 2013 Page A-1 File No. 0186-679-10
SNOQUALMIE SWITCH STATION Snoqualmie, Washington Soils encountered in the hand-augered borings were visually classified in general accordance with the classification system described in Figure A-1. A key to the hand-augered boring log symbols is also presented in Figure A-1. The logs of the borings are presented in Figures A-5 through A-7. The hand-augered boring logs are based on our interpretation of the field data, and indicate the various types of soils encountered. No groundwater was observed during excavation of the hand-augered borings. These observations may or may not be representative of the long-term groundwater conditions at the site. Page A-2 March 25, 2013 GeoEngineers, Inc. File No. 0186-679-10
MAJOR DIVISIONS SOIL CLASSIFICATION CHART SYMBOLS GRAPH LETTER TYPICAL DESCRIPTIONS ADDITIONAL MATERIAL SYMBOLS SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS GRAVEL AND GRAVELLY SOILS CLEAN GRAVELS (LITTLE OR NO FINES) GW GP WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES AC CC Asphalt Concrete Cement Concrete COARSE GRAINED SOILS MORE THAN 50% RETAINED ON NO. 200 SIEVE FINE GRAINED SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SAND AND SANDY SOILS MORE THAN 50% OF COARSE FRACTION PASSING NO. 4 SIEVE SILTS AND CLAYS GRAVELS WITH FINES (APPRECIABLE AMOUNT OF FINES) CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH FINES (APPRECIABLE AMOUNT OF FINES) LIQUID LIMIT LESS THAN 50 GM GC SW SP SM SC ML CL OL SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES WELL-GRADED SANDS, GRAVELLY SANDS POORLY-GRADED SANDS, GRAVELLY SAND SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS, ROCK FLOUR, CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY CR TS Crushed Rock/ Quarry Spalls Topsoil/ Forest Duff/Sod Groundwater Contact Measured groundwater level in exploration, well, or piezometer Measured free product in well or piezometer Graphic Log Contact Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit Material Description Contact MORE THAN 50% PASSING NO. 200 SIEVE SILTS AND CLAYS LIQUID LIMIT GREATER THAN 50 MH CH OH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY ORGANIC CLAYS AND SILTS OF MEDIUM TO HIGH PLASTICITY Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit HIGHLY ORGANIC SOILS NOTE: Multiple symbols are used to indicate borderline or dual soil classifications 2.4-inch I.D. split barrel Standard Penetration Test (SPT) Shelby tube Piston Direct-Push Bulk or grab Blowcount is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted). See exploration log for hammer weight and drop. A "P" indicates sampler pushed using the weight of the drill rig. PT Sampler Symbol Descriptions PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS %F AL CA CP CS DS HA MC MD OC PM PI PP PPM SA TX UC VS NS SS MS HS NT Laboratory / Field Tests Percent fines Atterberg limits Chemical analysis Laboratory compaction test Consolidation test Direct shear Hydrometer analysis Moisture content Moisture content and dry density Organic content Permeability or hydraulic conductivity Plasticity index Pocket penetrometer Parts per million Sieve analysis Triaxial compression Unconfined compression Vane shear Sheen Classification No Visible Sheen Slight Sheen Moderate Sheen Heavy Sheen Not Tested NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to be representative of subsurface conditions at other locations or times. KEY TO EXPLORATION LOGS FIGURE A-1
Drilled Start 2/22/2013 Surface Elevation (ft) Vertical Datum End 2/22/2013 Total Depth (ft) 446 14 Logged By Checked By Hammer Data ZAS HPD Driller Geologic Drill Exploration, Inc. Rope & Cathead 140 (lbs) / 30 (in) Drop Drilling Equipment Drilling Method Hollow-stem Auger Hand Portable AckerSoil Mechanic Drill Easting (X) Northing (Y) Notes: System Datum Groundwater Date Measured Depth to Water (ft) Not encountered Elevation (ft) FIELD DATA Elevation (feet) Depth (feet) Interval Recovered (in) Blows/foot Collected Sample Sample Name Testing Water Level Graphic Log Group Classification MATERIAL DESCRIPTION Moisture Content, % Dry Density, (pcf) REMARKS 0 CR Quarry spalls 3½ feet excavated by hand 445 SM Brown silty fine to medium sand with gravel and organics (fine roots) (loose to medium dense, moist to wet) (fill) 6 1 Rough drilling 5 12 12 2 440 Grades to medium dense Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD 435 ML 10 16 16 16 20 60 65 3 4 5 Notes: See Figure A-1 for explanation of symbols. Brownish-gray silt with trace sand and orange mottling (very stiff, moist) Grades to hard Project: Log of Boring B-1 Project Location: Project Number: Snoqualmie Switch Station Snoqualmie, Washington 0186-679-10 Easier drilling Figure A-2 Sheet 1 of 1
Drilled Start 2/22/2013 Surface Elevation (ft) Vertical Datum End 2/22/2013 Total Depth (ft) 448 11.5 Logged By Checked By Hammer Data ZAS HPD Driller Geologic Drill Exploration, Inc. Rope & Cathead 140 (lbs) / 30 (in) Drop Drilling Equipment Drilling Method Hollow-stem Auger Hand Portable AckerSoil Mechanic Drill Easting (X) Northing (Y) Notes: System Datum Groundwater Date Measured Depth to Water (ft) Not encountered Elevation (ft) FIELD DATA Elevation (feet) Depth (feet) Interval Recovered (in) Blows/foot Collected Sample Sample Name Testing Water Level Graphic Log Group Classification MATERIAL DESCRIPTION Moisture Content, % Dry Density, (pcf) REMARKS 0 SM Dark brown silty fine to medium sand with trace gravel and organics (fine roots) (loose to medium dense, moist) (fill) 445 10 25 1 ML Brownish-gray silt with trace sand, occasional gravel, and orange mottling (very stiff, moist) 5 12 52 2 ML Brownish-gray silt with trace sand and orange mottling (hard, moist) Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD 440 16 50/5.5" 3 10 14 50/5" 4 Notes: See Figure A-1 for explanation of symbols. Grades to moist to wet Log of Boring B-2 Project: Snoqualmie Switch Station Project Location: Snoqualmie, Washington Project Number: 0186-679-10 Figure A-3 Sheet 1 of 1
Drilled Start 2/22/2013 Surface Elevation (ft) Vertical Datum End 2/22/2013 Total Depth (ft) 450 11.5 Logged By Checked By Hammer Data HPD HPD Driller Geologic Drill Exploration, Inc. Rope & Cathead 140 (lbs) / 30 (in) Drop Drilling Equipment Drilling Method Hollow-stem Auger Hand Portable AckerSoil Mechanic Drill Easting (X) Northing (Y) Notes: System Datum Groundwater Date Measured Depth to Water (ft) Not encountered Elevation (ft) FIELD DATA Elevation (feet) Depth (feet) Interval Recovered (in) Blows/foot Collected Sample Sample Name Testing Water Level Graphic Log Group Classification MATERIAL DESCRIPTION Moisture Content, % Dry Density, (pcf) REMARKS 0 CR SM Gravel Dark brown silty fine to coarse sand with gravel and organics (fine roots) (loose, moist) (fill) 4 5 1 Gravels/cobbles 445 5 18 3 2 SM Brown/yellow silty fine to coarse sand with gravel and organics (fine roots and charcoal) (very loose, moist) Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD 440 ML 18 21 3 ML 10 18 50/6" 4 Notes: See Figure A-1 for explanation of symbols. Greenish-gray silt with trace sand and orange mottling (very stiff, moist) Grayish-brown silt with trace sand (hard, moist) Project: Log of Boring B-3 Project Location: Project Number: Snoqualmie Switch Station Snoqualmie, Washington 0186-679-10 Figure A-4 Sheet 1 of 1
Drilled Start 2/22/2013 Surface Elevation (ft) Vertical Datum End 2/22/2013 Total Depth (ft) 448 11.5 Logged By Checked By Hammer Data ZAS HPD Driller Geologic Drill Exploration, Inc. Rope & Cathead 140 (lbs) / 30 (in) Drop Drilling Equipment Drilling Method Hollow-stem Auger Hand Portable AckerSoil Mechanic Drill Easting (X) Northing (Y) Notes: System Datum Groundwater Date Measured Depth to Water (ft) Not encountered Elevation (ft) FIELD DATA Elevation (feet) Depth (feet) Interval Recovered (in) Blows/foot Collected Sample Sample Name Testing Water Level Graphic Log Group Classification MATERIAL DESCRIPTION Moisture Content, % Dry Density, (pcf) REMARKS 0 TS 6 inches topsoil SM Dark brown silty fine to coarse sand with gravel (medium dense, moist) (fill) 445 10 15 1 Rough drilling ML Grayish-brown silt with trace sand (hard, moist) 5 16 45 2 Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD 440 18 52 3 10 18 58 4 Notes: See Figure A-1 for explanation of symbols. Becomes moist to wet With orange mottling Log of Boring B-4 Project: Snoqualmie Switch Station Project Location: Snoqualmie, Washington Project Number: 0186-679-10 Figure A-5 Sheet 1 of 1
Date Excavated: Equipment: 2/22/2013 Hand Auger Logged By: Total Depth (ft) ZAS 1.0 SAMPLE Elevation (feet) Depth (feet) Testing Sample Sample Name Testing Graphic Log Group Classification Encountered Water MATERIAL DESCRIPTION Moisture Content, % REMARKS 1 2 SM Dark brown silty fine to coarse sand with gravel and organics (fine roots) (loose to medium dense, moist to wet) (fill) 437 1 Increasing gravel content, becomes medium dense Hand auger refusal at 1 foot due to gravel No groundwater seepage observed No caving observed Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC Notes: See Figure A-1 for explanation of symbols. The depths on the hand auger logs are based on an average of measurements across the hand auger and should be considered accurate to 0.5 foot. Log of Hand-Augered Boring HA-1 Project: Project Location: Project Number: Snoqualmie Switch Station Snoqualmie, Washington 0186-679-10 Figure A-6 Sheet 1 of 1
Date Excavated: Equipment: 2/22/2013 Hand Auger Logged By: Total Depth (ft) ZAS 0.5 SAMPLE Elevation (feet) Depth (feet) Testing Sample Sample Name Testing Graphic Log Group Classification Encountered Water MATERIAL DESCRIPTION Moisture Content, % REMARKS 1 GP-GM Gray fine to coarse gravel with silt and sand (medium dense, moist) Hand auger refusal at ½ foot No groundwater seepage observed Significant caving observed Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC Notes: See Figure A-1 for explanation of symbols. The depths on the hand auger logs are based on an average of measurements across the hand auger and should be considered accurate to 0.5 foot. Log of Hand-Augered Boring HA-2 Project: Project Location: Project Number: Snoqualmie Switch Station Snoqualmie, Washington 0186-679-10 Figure A-7 Sheet 1 of 1
Date Excavated: Equipment: 2/22/2013 Hand Auger Logged By: Total Depth (ft) ZAS 3.0 SAMPLE Elevation (feet) Depth (feet) Testing Sample Sample Name Testing Graphic Log Group Classification Encountered Water MATERIAL DESCRIPTION Moisture Content, % REMARKS TS 6 inches topsoil 443 1 1 2 SM Dark brown silty fine to medium sand with organics (fine roots) (loose, moist) (fill) 3 442 2 4 ML Brownish-gray silt with sand and orange mottling (soft, moist) 441 3 Hand auger completed at 3 feet No groundwater seepage observed No caving observed Becomes denser, cobble at 3 feet Seattle: Date:3/18/13 Path:W:\REDMOND\PROJECTS\0\0186679\GINT\018667910.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC Notes: See Figure A-1 for explanation of symbols. The depths on the hand auger logs are based on an average of measurements across the hand auger and should be considered accurate to 0.5 foot. Log of Hand-Augered Boring HA-3 Project: Project Location: Project Number: Snoqualmie Switch Station Snoqualmie, Washington 0186-679-10 Figure A-8 Sheet 1 of 1
APPENDIX B Report Limitations and Guidelines for Use
SNOQUALMIE SWITCH STATION Snoqualmie, Washington APPENDIX B REPORT LIMITATIONS AND GUIDELINES FOR USE 1 This appendix provides information to help you manage your risks with respect to the use of this report. Geotechnical Services Are Performed for Specific Purposes, Persons and Projects This report has been prepared for the exclusive use of Puget Sound Energy and their authorized agents. This report may be made available to prospective contractors for their bidding or estimating purposes, but our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. This report is not intended for use by others, and the information contained herein is not applicable to other sites. GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with which there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted geotechnical practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated. A Geotechnical Engineering or Geologic Report Is Based on a Unique Set of Project- Specific Factors This report has been prepared for the proposed improvements to the Snoqualmie Switch Station located on Railroad Avenue in Snoqualmie, Washington. GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates otherwise, do not rely on this report if it was: not prepared for you, not prepared for your project, not prepared for the specific site explored, or completed before important project changes were made. 1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org. March 25, 2013 Page B-1 File No. 0186-679-10