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HomeMy WebLinkAboutStampedlog Item 8 Geotech`AAspect 4CCNSULT1NG February 1, 2019 Wayne Herr Rocky Brook Hydroelectric P.O. Box 215 Brinnon, Washington 98320 Re: Geotechnical Report Rocky Brook Hydroelectric Plant Improvements 3020 Dosewallips Road Brinnon, Washington 98320 Project No. 180641 Dear Mr. Herr: U FEB 1 1 2019 JEFFERSON COUNTY DCD Aspect Consulting, LLC (Aspect) prepared this letter report to summarize our observations and recommendations made during our geologic reconnaissance, subsurface investigation, and landslide hazard evaluation for your hydroelectric plant discharge relocation project (Project) at 3020 Dosewallips Road in Brinnon, Washington (Site; Figure 1). We performed the field work in accordance with our agreed-upon scope of work dated December 17, 2018. Project Understanding Based on our review of the preliminary project plans (ELS, 2018; Appendix A) and discussions with you, we understand that the Project will consist of the construction of a new discharge for the existing hydroelectric facility. The new discharge is needed to facilitate updated replacement turbines for more efficient energy generation. The new discharge will consist of a 24 -inch -diameter pipe conveying water from the powerhouse, post -energy generation, back to Rocky Brook Creek. The discharge pipe will extend east from the powerhouse and be buried approximately 3 feet below -grade. The discharge will outfall to a 3 -sided concrete flow dispersion channel (tailrace) that will be approximately 10 feet wide by 7 feet tall by 15 feet long. Based on the available topographic data and a review of the Jefferson County (County) geologically hazardous area mapping, the majority of the Site is mapped as an area of moderate landslide hazard. The area around the existing powerhouse is mapped as a slight landslide hazard, and the area closer to Rocky Brook Falls is mapped as a high landslide hazard. A geotechnical report is required to characterize the subsurface conditions at the proposed discharge location, provide recommendations and opinions regarding the landslide hazards mapped at the Site in the context of the Project, and satisfy the County's requirements for Special Reports (County Code 18.22.420) and Protection Standards in its Critical Areas regulations (County Code 18.22.170 [9]). Summary of Findings Based on the observed Site conditions revealed during our reconnaissance and subsurface investigation and our understanding of the Project, the stability of the Site and surrounding areas of geologic hazard will not be adversely affected by the Project. The excavation and trenching Aslx:cl Consud6iaiy, I I C '�0 I�nl'arl'�ison /worruc�lVI L'niiabiiil��pc fsGaind �Y�R/v 4Pf; I' IU Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 required for installing the new discharge and dispersion channel will occur in a relatively flat area adjacent to the existing powerhouse and can be completed in a stable manner provided the conclusions and recommendations contained herein are incorporated into the Project design and construction. Observations We completed our reconnaissance and subsurface investigations on January 4, 2019. The following is a summary of our observations. Site Conditions and Topography The Site is located near the con nLience of Rocky Brook Creek and the Dosewallips River, as shown on Figure 1. The general Site layout, existing features, proposed discharge location, topography, and landslide hazard areas are shown on Figure 2. The Site is approximately 10.80 acres in area, oval-shaped, and oriented in a north-northeast to south-southwest direction. Rocky Brook Creek flows from north to south through the Site and is the source of water for the hydroelectric facility. It is bordered by vacant land to the east and west, exempt land (national forest) to the north, and Dosewallips Road to the south. The Site is developed with a parking area, gravel path, and the existing powerhouse and associated infrastructure. The intake for the powerhouse is located above Rocky Brook Falls and the existing discharge (outtake) for the powerhouse is located below the falls but upstream of the powerhouse. The proposed discharge will be located in the southern portion of the Site, near Dosewallips Road and adjacent to the powerhouse to allow for gravity discharge. Topographically, the southeastern portion of the Site is generally flat, and most of the rest of the Site slopes down to the south and southeast. Rocky Brook Creek flows through the northern portion of the Site over Rocky Brook Falls and then along the flat portion of the Site along its southeastern edge. The slope near the powerhouse exhibits undulating, bedrock hollow -type landforms on a scale of approximately up to 3 feet, but no striking landslide features were observed. Immediately to the west of the powerhouse, the slope up to the west has an inclination of approximately 48 degrees (111 percent) for the lower 20 feet and approximately 36 degrees (73 percent) above that. The powerhouse sits on a flat area on the right bank of Rocky Brook Creek that is approximately 50 feet wide. Between the eastern edge of the powerhouse and the right bank of Rocky Brook Creek is a small, flat path, approximately 10.5 feet wide, where we conducted our hand auger explorations and where the proposed discharge and flow dispersion channel will be constructed. The eastern edge of the path and most of the right bank of Rocky Brook Creek, consists of a rockery approximately 10 feet wide and 9.5 feet tall, constructed out of basalt boulders up to approximately 4 feet in diameter. Drainage We observed groundwater seepage, overland surface flows, and standing water during our subsurface explorations and Site reconnaissance. During our Site visit, it rained in the morning and was clear in the afternoon. On basalt outcrops located to the west (and upslope) of the powerhouse, we observed overland flow of water from above. We also observed seepage below the basalt outcrops on the slope on the western side of the Site. Near the powerhouse, we observed a 12 -inch, Page 2 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 black corrugated pipe running from the northern side of the powerhouse to the eastern side of the path. This pipe discharges onto the edge of the path and rockery and appeared to be actively eroding the path in the discharge area. Another 12 -inch, black corrugated pipe discharges in the middle of the rockery, and a third pipe runs under the path from the powerhouse and discharges into the middle of the rockery. We also observed standing water on the path and seepage in the top few inches of our hand auger explorations. Surface drainage and groundwater conditions at the Site will vary with fluctuations in precipitation and changes in Site and off -Site land use. Vegetation The path and area around the powerhouse is mostly free of vegetation. The slope on the western side of the Site is vegetated with a thin understory of sword fern, blackberries, and unidentified shrubs, and much of the ground surface, including loose pieces of basalt, is covered in moss. The slope also has few downhill -tilted trees, as well as juvenile cedars hemlocks and other conifers up to approximately 1.5 feet diameter at breast height (dbh). The conifers had no to very little trunk curvature at the trunk bases, indicating possible minor ongoing soil creep downslope. Geology Subsurface conditions at the Site were inferred from direct observation of exposed soil and rock outcrops, soil encountered in our hand auger explorations, and our review of applicable geologic literature. The available geologic mapping indicates that the Site is underlain by mass wasting deposits, alluvium, Vashon ice -contact deposits, and Crescent Formation basalt (Polenz et al., 2012). Our Site observations are generally consistent with the published geologic map. The mass wasting deposits, placed by downslope movement of soil and rock, are described to be cobbles, pebbles, sand, silt, clay, boulders, and diamicton; they are loose, generally unsorted, locally stratified, and shown along potentially or demonstrably unstable slopes. The alluvium, deposited by rivers and streams, is a boulder, cobble, and pebble gravel and sand with some silt, clay, and peat. It is moderately well sorted, stratified to massive, and was deposited in floodplains and on terraces. Both the mass wasting and alluvium deposits range in age from approximately 11,700 years to recent. The Vashon ice -contact deposits were deposited directly by continental glacial ice of the Puget Lobe of the Cordilleran Ice Sheet approximately 18,500 to 17,000 years ago. The ice -contact deposits are described as loose to compact, tan to gray, cobble and pebble gravel, sand, ablation till, flow till, lodgment till, lacustrine mud, and rare boulders that are variously sorted, massive to well stratified, and include sub -ice flow and collapse features. The Crescent Formation bedrock was deposited between approximately 56 to 34 million years ago by a mid -ocean ridge and/or an intraplate hotspot. The Crescent Formation is described as fine- to coarse-grained, blocky subaerial basalt flows with rare and thin sedimentary interbeds; typically weathered and fractured, dark gray where fresh and gray, dark purple, or dark gray -green where weathered. During our Site visit, we observed colluvium/weathered Crescent Formation basalt and fresh basalt on the slope on the western side of the Site and dense, gravelly fill material underlying the path east Page 3 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 of the powerhouse. We did not observe mass wasting deposits during our reconnaissance or within our subsurface explorations at the Site. Further description of the soil and rock types observed are provided below. Fill We observed fill under the existing path surface in all three hand auger explorations. The fill consisted of a SILTY SAND WITH GRAVEL (SM)l that was very dense, moist to wet, and brown to dark brown. In HA -01, HA -02 and HA -03, we hit refusal at 1.6 feet below ground surface (bgs), 1.4 feet bgs, and 2 feet bgs, respectively. In each hand auger hole, the refusal surface appeared to be a cobble- or boulder -sized rock, but it is difficult to determine whether the rock(s) in the holes are native Crescent Formation or rocks used to backfill the existing rockery on the right bank of Rocky Brook Creek. Colluvium/Weathered Crescent Formation The colluvium we observed on the slope on the western part of the Site was difficult to distinguish from weathered Crescent Formation basalt. The material is a SILTY SAND WITH GRAVEL (SM) that was dense to very dense, moist to very moist, and brown to dark brown with angular basalt gravel and cobbles. Crescent Formation We observed several Crescent Formation outcrops measuring approximately 3 feet to 10 feet by 5 feet to 10 feet on the slope on the western side of the Site. The Crescent Formation we observed was a BASALT that was RI (very weak rock) to R3 (moderately strong rock), wet, and black to red brown with white veins. Groundwater It rained during our hand auger explorations in the morning of our Site visit, and we observed surface water flowing into the hand auger holes as well as shallow groundwater conditions a few inches below the surface of the path. During the afternoon, we observed groundwater flowing over the faces of several basalt outcrops, and flowing downslope near the base of some outcrops on the slope west of the powerhouse. Geologic Hazards Landslide Hazard Varnes (1978) describes three types of landslides common on similar Sites and slopes in the Puget Sound region: topples, deep-seated rotational landslides, and shallow flows (also known as shallow landslides or skin slides). Landslides may be triggered by natural causes such as precipitation, freeze -thaw cycles, seismic events, or be man-made (e.g., broken water pipes or stormwater flow). At the time of our reconnaissance, we did not observe evidence of ongoing or significant landslide activity near the location of the powerhouse and proposed discharge. We did observe evidence of topples (rockfall) a few hundred feet north of the proposed new discharge location. In this location, we observed a few large (greater than 7 feet) boulders that fell from the basalt cliffs above, ' Soils were classified per the Unified Soil Classification System (USCS) in general accordance with ASTM International (ASTM) D2488, Standard Practice for Description and Identification of Soils (Visual and Manual Procedure). Page 4 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 destroyed juvenile trees, and landed on the western edge of the path. While we did not observe any evidence of large-scale rockfall patterns, workers should be mindful of the minor rockfall hazard present at the Site and be constantly aware of their surroundings when working in areas north of the powerhouse. Based on our observations, the Site and slopes are relatively stable, being comprised of intact or weathered basalt, and there is a low risk of deep-seated landslide activity. However, the steeper slopes at the Site, those located away from the existing powerhouse and Project elements, may be prone to small, shallow flow landslides and rockfall that occur on and are limited to the surface of the steep slope. Shallow flows are typically triggered by a significant increase in the moisture content within the upper soil layer of a slope, and commonly result from periods of extended or heavy precipitation, groundwater seepage, or concentrated surface water discharge onto a slope. Shallow flows can also occur over time, in a process called `creep,' in which surficial soils slowly move downslope. Surface creep is typically evidenced by curvatures in shade -tolerant trees (e.g., evergreens) on the slope. Shallow flows occur within the upper several feet of a slope and typically do not extensively affect the deep-seated or overall stability of a slope. Erosion Hazard The Site is mapped as an erosion hazard area by the County. Based on our observation of the Site and subsurface conditions, it is our opinion that the erosion hazard at the Site, in the context of the Project, is relatively low. The well-developed vegetative cover outside of the Project limits and the basalt and gravelly fill around the powerhouse and proposed discharge indicate that the potential for erosion as a result of the Project is low, provided appropriate erosion and sedimentation control measures are incorporated into the Project design and construction. As part of the Project, we recommend collecting and directing all Site stormwater and drainage, including stormwater from the powerhouse, to an approved discharge location and providing for flow dissipation to prevent erosion and the outlet(s) of the stormwater pipes. The margins of the flow dissipation channel should be protected from erosion and scour with large, angular rocks similar to the rockery stones that are currently present along the right bank of the creek. Liquefaction Hazard The Site is not mapped as a liquefaction hazard by the Washington State Department of Natural Resources (DNR, 2019). Because of the basalt present at or near the ground surface at the Site, the Site is not susceptible to liquefaction. Conclusions and Recommendations Based on the observed Site conditions revealed during our reconnaissance and subsurface investigation and our understanding of the Project, it is our opinion that the stability of the Site and surrounding areas of geologic hazard will not be adversely affected by the Project. The excavation and trenching required for installing the new discharge pipe and dispersion channel will occur in a relatively flat area adjacent to the existing powerhouse and can be completed in a stable manner provided the recommendations contained in this report are incorporated into the design and construction of the Project. Our key findings and conclusions include: • The Site landslide hazard areas will not be impacted by the Project elements. Page 5 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 • The Contractor should expect to encounter very dense soil with angular cobble- and boulder -sized particles or basalt bedrock conditions during trenching for the new discharge pipe and excavation for the dispersion channel, and should be prepared to rip basalt or use oversized equipment to accomplish the excavations for the Project. • The proposed concrete dispersion channel may be grade -supported on shallow foundations or as a concrete slab -on -grade, provided the subgrade materials under the foundations/slab- on-grade is properly prepared and compacted. • Because of the likely irregular bedding surface (as a result of excavating angular fill and/or ripping basalt) beneath the discharge pipe and the dispersion channel, we recommend including pipe bedding and a gravel -bearing pad beneath the dispersion channel to provide for uniform support conditions. • The upstream and downstream ends of the new dispersion channel should be protected from erosion and scour at the end of construction. + Any existing stormwater pipes impacted by the Project should be temporarily re-routed and/or replaced at the end of the Project. The 12 -inch -diameter black corrugated drain pipe that is actively causing erosion along the east edge of the path should be extended to the base of the existing rockery and provided with flow dispersion to prevent further erosion. Temporary and Permanent Erosion Control To prevent Site erosion during construction, appropriate temporary erosion and sedimentation control (TESC) measures should be used in accordance with local best management practices (BMPs). Specific TESC measures may include appropriately placed silt fencing, straw wattles, rock check dams, and plastic covering of exposed slope cuts and soil stockpiles. Outside of the proposed construction areas, the existing vegetation should be retained. Permanent erosion control within the areas of construction should be achieved surfacing with rock or the re-establishment of vegetation. Temporary Excavation Stability and Permanent Slopes Maintenance of safe working conditions, including temporary excavation stability, is the responsibility of the Contractor. Workers should be aware of the intermittent rockfall hazard associated with the steep slope west and upstream of the existing powerhouse. All temporary cuts in excess of 4 feet in height that are not protected by trench boxes or otherwise shored should be sloped in accordance with Part N of Washington Administrative Code (WAC) 296-155 (WAC, 2009), as shown in Table 1 below. Page 6 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 Table 1. Temporary Excavation Cut Slope Recommendations Notes: OSHA = Occupational Safety and Health Administration; H:V = Horizontal:Vertical The estimated maximum cut slope inclinations are provided for planning purposes only and are applicable to excavations without groundwater seepage or runoff, and assume dewatered conditions. Flatter slopes will likely be necessary in areas where groundwater seepage exists, or where construction equipment surcharges are placed in close proximity to the crest of the excavation. With time and the presence of seepage and/or precipitation, the stability of temporary unsupported cut slopes can be significantly reduced. Therefore, all temporary slopes should be protected from erosion by installing a surface water diversion ditch or berm at the top of the slope. In addition, the Contractor should monitor the stability of the temporary cut slopes, and adjust the construction schedule and slope inclination accordingly. Vibrations created by traffic and construction equipment may cause caving and raveling of the temporary slopes. In such an event, lateral support for the temporary slopes should be provided by the Contractor to prevent loss of ground support. Permanent slopes for the Project should be no steeper than 2H: IV (Horizontal:Vertical). Site Preparation Site preparation within the proposed construction area footprint should include removal of all debris and any other deleterious material including all topsoil with significant root debris. The Contractor must use care during Site preparation and excavation operations so that any bearing surfaces are not disturbed. If this occurs, the disturbed material should be removed to expose undisturbed material or compacted in-place. All footing excavations should be trimmed neat and the bottom of the excavation should be carefully prepared. All loose or softened soil should be removed from the footing excavation or compacted in place prior to placing reinforcing steel bars. We recommend that footing excavations be observed by Aspect prior to placing steel and concrete, to verify that the recommendations of this report have been followed. Foundations Although the bearing soils at the base of the dispersion channel were not directly observed during our reconnaissance or within our subsurface explorations, we assume the soils will consist of either dense, gravelly fill or weathered Crescent Formation basalt. For either condition, we recommend an allowable foundation bearing pressure of 3,000 pounds per square foot (psf) be utilized for design purposes. An increase in the above-mentioned bearing pressure of one-third may be used for short- term loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection and be a minimum of 14 inches wide; interior footings require only 12 inches burial below outside grade. No footing should be founded in or above yielding/loose or organic soils. Page 7 OSHA Soil Maximum Maximum Soil Unit Classification Temporary Sloe Height ft Gravelly Fill B 1HAV 10 Crescent Formation Basalt (Weathered) A 0.75H:1V 10 Notes: OSHA = Occupational Safety and Health Administration; H:V = Horizontal:Vertical The estimated maximum cut slope inclinations are provided for planning purposes only and are applicable to excavations without groundwater seepage or runoff, and assume dewatered conditions. Flatter slopes will likely be necessary in areas where groundwater seepage exists, or where construction equipment surcharges are placed in close proximity to the crest of the excavation. With time and the presence of seepage and/or precipitation, the stability of temporary unsupported cut slopes can be significantly reduced. Therefore, all temporary slopes should be protected from erosion by installing a surface water diversion ditch or berm at the top of the slope. In addition, the Contractor should monitor the stability of the temporary cut slopes, and adjust the construction schedule and slope inclination accordingly. Vibrations created by traffic and construction equipment may cause caving and raveling of the temporary slopes. In such an event, lateral support for the temporary slopes should be provided by the Contractor to prevent loss of ground support. Permanent slopes for the Project should be no steeper than 2H: IV (Horizontal:Vertical). Site Preparation Site preparation within the proposed construction area footprint should include removal of all debris and any other deleterious material including all topsoil with significant root debris. The Contractor must use care during Site preparation and excavation operations so that any bearing surfaces are not disturbed. If this occurs, the disturbed material should be removed to expose undisturbed material or compacted in-place. All footing excavations should be trimmed neat and the bottom of the excavation should be carefully prepared. All loose or softened soil should be removed from the footing excavation or compacted in place prior to placing reinforcing steel bars. We recommend that footing excavations be observed by Aspect prior to placing steel and concrete, to verify that the recommendations of this report have been followed. Foundations Although the bearing soils at the base of the dispersion channel were not directly observed during our reconnaissance or within our subsurface explorations, we assume the soils will consist of either dense, gravelly fill or weathered Crescent Formation basalt. For either condition, we recommend an allowable foundation bearing pressure of 3,000 pounds per square foot (psf) be utilized for design purposes. An increase in the above-mentioned bearing pressure of one-third may be used for short- term loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection and be a minimum of 14 inches wide; interior footings require only 12 inches burial below outside grade. No footing should be founded in or above yielding/loose or organic soils. Page 7 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 We estimate the total settlement of the foundation designed in accordance with our recommendations will be less than 1 inch. Differential settlements can be expected to be less than half of the total settlement. Our experience indicates the majority of these settlements will occur during construction. Wind, earthquakes, creek flows, and unbalanced earth loads will subject the proposed structure to lateral forces. Lateral forces on a structure will be resisted by a combination of sliding resistance of its base or footing on the underlying soil and passive earth pressure against the buried portions of the structures. For use in design, an ultimate coefficient of friction of 0.55 may be assumed along the interface between the base of the footing and subgrade soils. An ultimate passive earth pressure of 400 pounds per cubic foot (pcf) may be assumed for native soils adjacent to below -grade elements. The upper 1 foot of passive resistance should be neglected in design. The recommended coefficient of friction and passive pressure values are ultimate values that do not include a safety factor. We recommend applying a factor of safety of at least 1.5 in design for determining allowable values for coefficient of friction and passive pressure. Discharge Pipe and Dispersion Channel Considerations Because of the likely irregular bedding surface (as a result of excavating angular fill and/or ripping basalt) beneath the discharge pipe and the dispersion channel, we recommend including pipe bedding and a gravel -bearing pad beneath the discharge pipe and dispersion channel, respectively, to provide for uniform support conditions. The gravel pad should be a minimum of 4 inches thick. Pipe bedding and the gravel -bearing pad should consist of Gravel Backfill for Pipe Zone Bedding meeting the requirements of Section 9-03.12(3) of the Washington State Department of Transportation (WSDOT) Standard Specifications (WSDOT, 2018). The pipe bedding and gravel - bearing pad should be compacted to at least 95 percent of the maximum dry density (MDD) as determined by test method ASTM International (ASTM) D 15 57 (modified proctor). If desired, lean concrete or controlled density fill (CDF) can also be used for the bearing pad beneath the dispersion channel Native soils may be used for trench backfill, provided clods or rocks greater than 6 inches in diameter are removed prior to placement. If imported material is used for trench backfill, we recommend Gravel Borrow, as specified in Section 9-03.14(1) of the Standard Specifications (WSDOT, 2018). Trench backfill should be compacted to at least 90 percent of the MDD as determined by test method ASTM D1557. The upstream and downstream ends of the new dispersion channel should be protected from erosion and scour by placing large, angular boulders around the ends. The existing rockery stones may be reused for this purpose and should be embedded a 2 to 3 feet below the base of the channel, unless intact basalt is present. If imported rock is used or required to supplement the existing on -Site materials, we recommend Class C Rock for Erosion and Scour Protection, as specified in Section 9-13.4 of the Standard Specifications (WSDOT, 2018). Page 8 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 References ASTM International (ASTM), 2018, 2017 Annual Book of ASTM Standards, West Conshohocken, Pennsylvania. Ecological Land Services (ELS), 2018, Rocky Brook HMP Drawings, dated November 12, 2018. Polenz, M., Spangler, E., Fusso, L.A., Reioux, D.A., Cole, R.A., Walsh, T.J., Cakir, R., Clark, K.P.; Tepper, J.H., Carson, R.J., Pileggi, D., and Mahan, S.A., 2012, Geologic map of the Brinnon 7.5 -minute quadrangle, Jefferson and Kitsap Counties, Washington: Washington Division of Geology and Earth Resources Map Series 2012-02, scale 1:24,000, 1 sheet, 47 p. text. Varnes, D.J., 1978, Slope movement types and processes, in Schuster, R.L., and Krizek, R.J., eds., Landslides—Analysis and control: National Research Council, Washington, D.C., Transportation Research Board, Special Report 176, p. 11-33. Washington State Department of Natural Resources (DNR), 2019, Washington Geologic Information Portal, https:Hgeologyportal.dnr.wa.gov/, accessed January 20, 2019. Washington State Department of Transportation (WSDOT), 2018, Standard Specifications for Road, Bridge and Municipal Construction, Document M 41-10. Washington State Legislature, 2009, Washington Administrative Code (WAC), April 1, 2009. Page 9 Rocky Brook Hydroelectric February 1, 2019 Project No. 180641 Limitations Work for this project was performed for Rocky Brook Hydroelectric (Client), and this report was prepared consistent with recognized standards of professionals in the same locality and involving similar conditions, at the time the work was performed. No other warranty, expressed or implied, is made by Aspect Consulting, LLC (Aspect). Recommendations presented herein are based on our interpretation of site conditions, geotechnical engineering calculations, and judgment in accordance with our mutually agreed-upon scope of work. Our recommendations are unique and specific to the project, site, and Client. Application of this report for any purpose other than the project should be done only after consultation with Aspect. Variations may exist between the soil and groundwater conditions reported and those actually underlying the site. The nature and extent of such soil variations may change over time and may not be evident before construction begins. If any soil conditions are encountered at the site that are different from those described in this report, Aspect should be notified immediately to review the applicability of our recommendations. Risks are inherent with any site involving slopes and no recommendations, geologic analysis, or engineering design can assure slope stability. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the Client. It is the Client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, and agents, are made aware of this report in its entirety. At the time of this report, design plans and construction methods have not been finalized, and the recommendations presented herein are based on preliminary project information. If project developments result in changes from the preliminary project information, Aspect should be contacted to determine if our recommendations contained in this report should be revised and/or expanded upon. The scope of work does not include services related to construction safety precautions. Site safety is typically the responsibility of the contractor, and our recommendations are not intended to direct the contractor's site safety methods, techniques, sequences, or procedures. The scope of our work also does not include the assessment of environmental characteristics, particularly those involving potentially hazardous substances in soil or groundwater. All reports prepared by Aspect for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect. Aspect's original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Please refer to Appendix B titled "Report Limitations and Guidelines for Use" for additional information governing the use of this report. Page 10 Rocky Brook Hydroelectric February 1, 2019 We appreciate the opportunity to perform these services. Sincerely, Aspect consulting, LLC w4T� q- c� Andrew J. Holmson, PE Associate Geotechnical Engineer aholmson@aspectconsulting.com Project No. 180641 Bill Grimm, GIT Staff Geologist bgrimm@aspectconsulting.com Attachments: Figure 1 — Site Location Map Figure 2 — Site and Exploration Plan Appendix A — Rocky Brook HMP Preliminary Drawings (ELS, 2018) Appendix B — Report Limitations and Guidelines for Use cc: Laura Westervelt, Ecological Land Services VA160641 Rocky Brook Hydroelectric Updates\Deliverables\Geotech Report\Rocky Brook Hydroelectric Report_20190201.docx Page 11 FIGURES ft ffa 4 lit SITE LOCATION rrI� 8uheek ' 1 " HOW. SITE. LOCATION _ r t -k nLy�.y►yr 1M: - - .. . I v J rS k ti .. w P41 low Air 2'000 4,060 Feet °Bellinpf,sm Site Location Map •peri. ' ales SITE LOCATION Geotechnical Report seatue °s °kane Rocky Brook Hydroelectric Updates r, racoma •�Cf1°` 3020 Dosewallips Road W A S H I N G T O N Brinnon, Washington •Yakatta FIGURE NO. �1Sect JAN -2019 / AIH / WEG PR OIECr NO 1E _ VBY 1 C -O uLrING 18064101 9esemap Layer Credits I I Sources: Esri, HERE, Garmin, Intermap, Incremunt P Corp., GE®CO, MS, FAO, NPS, -F4 , Geo6a9e, IGN, itedaster NL, Ordnapee Survey, Esri Japan, METI, Esrl China [Hong Isongl, swrsszopo. 6 OpenStreetMap contributors, and the GIS User Community Copyright:© 2014 Esrl 160' INSET MAP � �• ` �� �` - - -- -- Via• 15B ,. / Powerhouse r Proposed Outlets V V 1yL ❑ 30 f Feet 1 i + I L � ■ 1 ■ 1 ■ilpfj 1 ■L 1 1 z i , 1 � 1 � 1 , 550' � I L i ■ 1 500' 'L 1 Rockfall 450' ■ 1 , _ t , I , s , f 400'' i , 1 , 1 35� ■� I , l i { Powi 1 ■ ■ 1 1 1L N10 p 1plo use Outlet Landslide Hazard �� Contour Line - 50 ft* High Site and Exploration Plan \_. ' Contour Line 10 ft* Geotechnical Report Moderate Tax Parcel Rocky Brook Hydroelectric Updates 3020 Dosewallips Road Slight 0 200 400 Brinnon, Washington Hand Auger Subject Property Feet ' + Apecl JAN -2019 re0641-0 A1H/TDR ev FIGURE NQ •Contours derived from National Elevation Dataset (NED) co�-sui rir+t aEnsEu 2 180641-01 --- APPENDIX A Rocky Brook HMP Preliminary Drawings (ELS, 2018) ol WASHINGTON ND�EN PROJECT `ted ,kyr WHATCOM SITE VICINITY MAP SANJUAN CC FRIDAY L .a c xaar�r i j N1 HltlaYl SKA(MY j r prK C nwr •oar N Rwnrn, CV Latitude: 47.7201- Longitude: 7.7201`Longitude: -122.9426' SNOHOMISH FORKSCLALLAM r Q = p N LOCATION MAPW JEFFERSON R } 0O x > ., 7 Y 7 Q SITE MASON yaR m O � T reMwe is - T 2 L co clj FYoone KING 0cc 30 e� BOR wa..w O 41 ~ r IX — 00 COPALIS a rm CV BEACH 1 CL Z ocEAN b PIERCE ^ (n HOR' rfi£ to Y TORT rpmre yr A p R 2 jP THURSTON 'u .rump ccarrcuu (q B I a�wie LENRS r 0�0 OCUR �tOG[ RpX Lhi p7 e, PACIFIC T v° 26 i NHIJAI tuner SKAMANIA r NNO' COw"T2 A mT Br. r� HE—B c avoouua �G K Uo 15 J Q' F- O NOTE: .ter o�vrcRwo SCALE IN MILES lJ m LU co x USGS topographic quadrangle map reproduced using Q C! Ix = O a MAPTECH Inc., Terrain Navigator Pro software. ❑ o IX a- U a V i �• r • ` �� O�6mM O m 'n3�S o S � n f- Q rn 73 m`a o Of^� co Sze p f . -- - k. WA IPS 1)0 Ul moo-- - _ �- a p 600 a c3 Z V U }a _ p O a }� W E I s 11/12/2018 10:15 AM nu�w 2 3 Z Brook Hydroelectrict2766 01 -Rocky Brook 4 H� Vxx M r a � ' www.w.r......r 22 FS. fi NOTE(S): 1 l 1. Site plan provided by NE 8, C 1 l DATE: 11/12/16 1 [ 57 3rd Ave., Suite 220A DWN: JKJ 0 1'.:.'7 200 LonVew, WA 98632 REQ. BY: LW K=e:860�578-1371 PRJ. MGR: LW SCALE IN FEET E'� €� Fax. (360) 414-9305 CHK: x ecu-laad.mm 5 Land 5�r le PROJECT NO: Jennifer r..nee�+ryu Tur. T�Irr. xrlrro♦rrM of Tur6laa Tallraca VIEW AA 1h PRELIMINARY DRAWING h gure 4 PROPOSED CONDITIONS - NEW OUTTAKE Rocky Brook HMP Rocky Brook Hydroelectic Jefferson County Washington Section 28, Township 26N, Range 2W, W.M. cn g LU Q c� J U N N nm c=oL 602212000 Lr) U Y Z d> 0 7 F O Y N rnZ CO p s1 O vm U) Z0L0o O ON~ U) W a)c v cel NSITE LL U o w ti m 802283009 8022820W Lr o °r° � 3 O oc� _ ncoN J J O LUwah0 2 H 0-i 0 ' p 00LU d0a. 0_ 0 602282003 a0 QO mnC E Y .tom Dase+rell�e N .0 m M OV 00 N 3 I } { G .3g^ m O b aoasasu ', J r L" v N a > :A •_ Y o y 0 0]10 802283014 C o .. � • W� r- L.9.nd 0 JG Roede m Parcels -H FEAAAFI Altsps1 0 8hwallne oesigmtion-Am A ANI w Camammyllubwtm 0 xm o Z al�v o o uFb2-� "O w 12 L) w I Q Kund Nxu*s �f Cnnrurvm�y �!y J_ Nxu�al'S�Aurv.v� O S N 4 co VY E CO NOTE(S): i�Q 1. Map provided on-line by Jefferson County at web address: — http:Ilmaps.co.le(Terson.wa.us/}IVebsitelmsRubNiewsr.hurl?Irlapset=esa s APPENDIX B Report Limitations and Guidelines for Use 11/12/2018 10:15 AM S:\ELS\WA\Jefferson\County-Projects\2788-Rocky Brook Hydroelectric\2788.01-Rocky Brook HMP\2786.01-Fi¢ures12788 01_SH d g Jennifer 1414, 1 a lrtonb. bwbn \ � aao ft. 127 d 11� M I 16A 3 Y TurbineTelimce _ 1 VIEW AA LEGEND: C2�4 ...�........�:•�R { [ Temporary Impacts (136 sq, ft.) ...,... r.._ ,., 1 .-�.,..�..b.�•. lS � j� Planting Area (320 sq. ft.) F�----- 22 ft. — l MI Ion rant 011 i ,b,br,,,,r,,,,,,— Species common Name Stn §Eft Number PccaoAtchansls Sitka spruce 8feet :oncenter 3,gallon,potted 3 pR� y Ribes Red flowering 5 feet on center 1 -gallon, potted 6 sanULOeLan currant Rosa mtkana Nootka rose 5 feet on center 1- allon tted 6 alechnum deer fern 2f1* on center 1 -gallon, potted 20 - Ci s fcwnf 11 Total 3S 1 Site L Ian provided by NE & C PRELIMINARY DRAWING DATE: 11/12/18 Figure 5 3rd Ave., Suite 220A OWN: JKJ MITIGATION PLAN OVERVIEW 0 100 200*12157 Longview, wA 98632 REQ. BY: LW Rocky Brook HM P Phone: (360) 578-1371 PRJ. MGR: LW Rocky Brook Hydroelectic SCALE IN FEET jFax: (360) 414-9305 CHK: Jefferson County, Washington www.eco-land.comPROJECT NO: Section 28, Township 26N, Range 2W, W.M. 278601 ASPECT CONSULTING REPORT LIMITATIONS AND GUIDELINES FOR USE Geoscience is Not Exact The geoscience practices (geotechnical engineering, geology, and environmental science) are far less exact than other engineering and natural science disciplines. It is important to recognize this limitation in evaluating the content of the report. If you are unclear how these "Report Limitations and Guidelines for Use" apply to your project or property, you should contact Aspect Consulting, LLC (Aspect). This Report and Project -Specific Factors Aspect's services are designed to meet the specific needs of our clients. Aspect has performed the services in general accordance with our agreement (the Agreement) with the Client (defined under the Limitations section of this project's work product). This report has been prepared for the exclusive use of the Client. This report should not be applied for any purpose or project except the purpose described in the Agreement. Aspect considered many unique, project -specific factors when establishing the Scope of Work for this project and report. You should not rely on this report if it was: • Not prepared for you; • Not prepared for the specific purpose identified in the Agreement; • Not prepared for the specific subject property assessed; or s Completed before important changes occurred concerning the subject property, project, or governmental regulatory actions. If changes are made to the project or subject property after the date of this report, Aspect should be retained to assess the impact of the changes with respect to the conclusions contained in the report. Reliance Conditions forThird Parties This report was prepared for the exclusive use of the 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 liability claims by third parties with whom there would otherwise be no contractual limitations. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with our Agreement with the Client and recognized geoscience practices in the same locality and involving similar conditions at the time this report was prepared Property Conditions Change OverTime This report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by events such as a change in property use or occupancy, or by natural events, such as floods, earthquakes, slope instability, or ASPECT CONSULTING groundwater fluctuations. If any of the described events may have occurred following the issuance of the report, you should contact Aspect so that we may evaluate whether changed conditions affect the continued reliability or applicability of our conclusions and recommendations. Geotechnical, Geologic, and Environmental Reports Are Not Interchangeable The equipment, techniques, and personnel used to perform a geotechnical or geologic study differ significantly from those used to perform an environmental study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually address any environmental findings, conclusions, or recommendations (e.g., about the likelihood of encountering underground storage tanks or regulated contaminants). Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding the subject property. We appreciate the opportunity to perform these services. 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