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HomeMy WebLinkAbout601321003 Geotech Assessment & ASSOCIATES, INC. GEOTECHNICAL ENGINEERING · ENVIRONMENTAL ENGINEERING C()\5 I RLCIION ~ ESl'lNG & INSPECTION September 24. 2002 KA Project No. 102-02097 Mr. Richard Grandy Grand~, Marble & Tile 5809 NE .MinderRoad Unit Poulsbo. X, VA 98370 RE: Limited Slope Assessment Proposed Cable Lift Tram 280 FoxGlove Lane Quilicene, Washington As requested. ~ve are pleased to present this letter summarizine our limited slope reconnaissance for the subject propert3'. The purpose of the letter report is to provide a professional opinion as to the feasibilitx of constructing the proposed tram. In addition, seismic concerns and a detailed slope stabilitx analysis ~xere not pedbrmed as part of this assessment. In preparing this letter, ~e visited the subject site to observe general site conditions and reviewed a cross section of the slope provided by Team 4 Engineering. drawings provided by the Accumar Corporation. and revie~ved slope stability maps for Jefferson County in accordance xvith the scope of sen'ices outlined in our proposal KA No. P(5 02-164, Dated September 19. 2002. Our scope of services are based on responding to an August 21. 2002 letter eenerated bx' the Jefferson CounD' Department of Community Development regarding the proposed deve~'opment anc~ are in zeneral conformance ~xith Section 3.6.7 of the Jefferson Countx Unified Development Code amended 5ulv 2. 2001. Our scope of services for the project included the follox~ing: · A site reconnaissance b~ a member of our staff to evaluate the surface conditions at the project site. · Preparation of this report presenting the results of our field obserxafions and providing our professional opinion regarding the impact of the proposed development on the subject slopes. PROPOSED CONSTRUCTION From our discussions ~ ith 3'on on September 11. 2002 and our meeting ~ ith Accumar Corporation on September 17 2002, we understand that the proposed project x~ ill consist of the construction of a cable lift tram on a steep slope. The tram x~ill consist of an upper deck structure at the top of the slope, a landing structure at the base of the slope, and a series of cable support poles on the slope. We understand that the proposed deck structure at the top of the slope will be on the edge of the slope. The project location is shmxn on the attached Vicinit)' Map. Figure 1. Eleven Offices Serving The Western United States 20714 State Hieh~vax 305 NE. Suite 3C · Poulsbo. Washinoton 983"0 · (360} 598-2126 · Fax: {360) '~98-'~ 1'~' KA No. 102-02097 September 24. 2002 Page No. 2 SITE LOCATION AND SITE DESCRIPTION General The property.-is located x~est of Foxglove Lane on the Toanados Peninsula in Jefferson Countx. Washington. The property, is bound to the north bx tile subject residence at 280 FoxGIoxe Lane. to tl;e south bx a single-family residence, to the west b.v Dabob Bay. and to the east bx FoxGlove Lane. The site consists ora relatixelv level plateau above a relatNely' steep slope descending to the x~est. The slope is approximately 300 feet in height. The site x~as vacant and forested at the time of our site visit. In general, tile slope areas are xegetated with a mixture of mature cedars, firs and alders. Localized areas of the slope have a moderate under story of brush. A footpath from the residence at 280 Foxglove Lane provides access to the proposed tram location. x~hich is slightly higher in elevation than the residence. Site History The existing residence at 280 Foxglove Lane has been in place for approximately l 1 years. Prior to that time the lot x~as vacant. The lot for the proposed tram was forested and vacant at the time of the site visit. There is no record of previous development on this lot. The residence to the south of the subject lot has been in place for approximately 3 years. Geologic Settine Tile subject site lies x~ithin the central Puget Lowland. Tile loxxland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene. Oregon. North of Ol.,,mpia. Washington. this Ioxvland is glacially carved, with a depositional and erosional history that includes at least four separate glacial advance/retreats. The Puget Lox~land is bounded on the ~est by the Olympic Mountains and on the east by the Cascade Range. The loxvland is filled with glacial and nonglacial sediments consisting of interbedded gravel, sand. silt. till. and peat lenses. The United States Department of the Interior United States Geological Survey (USGS). Geologic Map of The 30' b~ 60' Seattle Quadrangle. Washington dated 1991. indicates that tile property' and surrounding area is located ~ithin Vashon advanced oumash deposits. The Vashon sediments x~ere deposited during the Early to Late Pleistocene and consist of oxidized red-broxYn gravel and cobbles x, ith zones of iron oxide cementation, and nonglacial deposits of red-bro,,¥n, oxidized sand and gravel and bro~n to gra.~ fine-grained sand. silt and clay:. The Washington Division of Geology' and Earth Resources Geologic Map GM-50 dated 2002 gives the sediments a designation of Glacial Till. There was no visible evidence of water seepage or springs within 1000 feet of tile proposed tram location at the time of the site visit. Krazan & Associates, Inc. Etexcn Or'rices Serx lng The "a'estcm United States I02-':2~°' Grand~ Tram KA No. I 0,-0~097 September 24. 2002 Page No. 3 HISTORICAL REVIEW A revie~ of the "Relatixe Slope Stability itl East-Central Jefferson County. Washington" map b3 R. U. Birdseye. 1976. ~xas pertbrmed in conjunction ~ith preparing this studx. Tile mapping by R. U. Birdseye indicates that the plateau area of the site is located in an area mapped as stable(l) or no,'mallv stable unless modified by man (2) x¥ith tile adjacent dmYnslope areas mapped as unstable areas (3) and areas of recently active, rapid landslides (5). The "Coastal Zone Atlas of Jefferson Count).. Washington" Department of Ecolo_ox. 1979. indicates the that the plateau area of the site is stable (S). with the adjacent steep slope area as unstable (U) ~¥ith areas of both unstable recent slides (Uts) and unstable old slides (Uos). Site Reconnaissance During our reconnaissance a limited site sur~,ey was performed. There x~ere no visible indications of slope failure and/or instabilit)-. ~hich include hummocky terrain, inconsistent patterns of ve_oetation. tension cracks, seepage zones and course grain material overlaying silt and clay soils, at the tir~e of the site ~isit. The trees on the lot to the south of the proposed tram were bo~ed, a condition that is commonly due to soil creep on a slope. The obse~'ed cur~'ature of the trees was slight but consistent. The residence at 280 Foxglove has been in place for approximately l 1 years and is located on the crest ora slope. The current properts., oxy, her stated that there had been some ~loughing of the slope below the residence approximately 8 y'ears ago after logging activities. There xxas no visible indication of structural distress on the residence at the time of the site visit and no visible indications of recent slide activity' or erosion. CONCLUSIONS AND RECOMMENDATIONS General The follox¥ing paragraphs present the results of our anal?sis and recommendations for design and construction of tile proposed project. It is our opinion that development of the subject lot ~xill not significantly impact the stabilitx of the slope. There is little to no remoxal of xezetation associated ~ith the installation of the cable support poles on the slope face. The location of'the ;roposed deck structure is such that its construction xxill have no impact on the single-family residences to tile north and south of the site. Further. due to the small size and light associated loads o'f the deck structure, it is our opinion that the structure will have little to no impact on the overall stabilit~ of the slope. Tile statement regarding the impact on the stability of tile slope due to the construction of tile deck structure assumes that the structure is placed essentially at or below grade and that associated earthwork construction is protected to prevent erosion. Note that we have not analyzed the overall stabili~-of the slope. It is our opinion that such an analysis is not necessary for the proposed construction as the impact of'the structure on tile slope is minimal.'the Krazan & Associates, Inc. Elcx en ()tlices Serx lng The ~¥estern L'nitcd States I~'2-,C'.~- Gracd~ Tram KA No. 10_-0_097 September 24. 2002 Page No. 4 structure is not generally' occupied, and the overall impact of the tramx~ax x~ ill likelx be less than that of a trail constrtlcted to the beach at approximatel.v the same location. Drainage The ground surface should slope axvav from the proposed deck building toward appropriate drop inlets or other surface drainage devices. Roof drains should be tightlined awa.v from foundations. A perimeter footing drain should be installed. All ~,'ater from pavement areas, roof drains, and l~boting drains should be tight-lined to an appropriate outlet. LIMITATIONS Geotechnical engineering is one of the ne~test divisions of Civil Engineering. This branch of Civil Engineering is constantly improving as new technologies and understanding of earth sciences improves. Although )'our site was analyzed using the most appropriate current techniques and methods. undoubtedly there will be substantial future improvements in this branch of engineering. In addition to improvements in the field of Geotechnical engineering, physical changes in the site either due to excavation or fill placement, net~ agency regulations or possible changes in the proposed structure after the time of completion of the soils report may' require the soils report to be professionally rexiex~ed. In light of this. the Ortner should be aware that there is a practical limit to the usefulness of this report without critical review. Although the time limit for this review is strictly arbitrary., it is suggested that txvo years be considered a reasonable time for the usefulness of this report. Foundation and earthwork construction is characterized by the presence of a calculated risk that soil and groundxtater conditions have been fully rexealed by' the original foundation investigation. This risk is derived from the practical necessiD' of basing interpretations and design conclusions on limited sampling of the earth. The recommendations made in this report are based on the assumption that soil conditions do not var~' significantly from those disclosed during our field investigation. If ant' variations or undesirable conditions are encountered during construction, the Geotechnical engineer should be notified so that supplemental recommendations can be made. The conclusions of this report are based on the information protided regarding the proposed construction. If the proposed construction is relocated or redesigned, the conclusions in this report mat not be valid. The Geotechnical engineer should be notified of any changes so the recommendations can be reviexved and reevaluated. This report is a geotechnical engineering investigation x¥ith the purpose of evaluating the soil conditions in terms of foundation design and slope stabiliD. The scope of our serv'ices did not include ant' environmental site assessment for the presence or absence of hazardous and/or toxic materials in the soil. groundx~ater or atmosphere, or the presence of wetlands. An,,' statements, or absence of statements, in this report or on an,,' boring log regarding odors, unusual or suspicious items, or conditions observed are strictly for descriptive purposed and are not intended to conve,, engineering judgment regarding potential hazardous and/or toxic assessrnent. Krazan & Associates, Inc. Elexen Or'rices Serx lng The ~,'estem United States ~t;2-42©0- Grand?, Tram KA No. 102-02097 September 24. 2002 Page No. 5 The geotechnical information presented herein is based upon professional interpretation utilizing standard engineering practices and a degree of consera/atism deemed proper tbr this project. It is not warranted that such inl'brmation and interpretation cannot be superseded bx future aeotechnical developments. ~'e emphasize that this report is valid tbr this project as outlined above, and should not be used for an~ other site. If you have any questions, or if we max' be of further assistance, please do not hesitate to contact our office at (360) 598-2126. Respectful13 submitted, KRAZAN & ASSOCIATES, INC. /~/f~ ~/~L~- Shawn E. Williams. R.G. Todd S. Parkington. P.E. Senior Environmental Geolooist Senior Geotechnical Engineer SEW/tsp.sex~ j~EXP~ES 5/01/ Krazan & Associates, Inc. Ele,.en Offices Serx lng The XVestem United States KA No. 102-02097 September 24. 2002 Page No. 6 REFERENCES U.S. Geological Surx,ey. 7.5-minute Seabeck. Washington topographic quadrangle map. dated 1953. Photoinspected 1973. Geologic Map of Washington-Northwest Quadrant. Geologic Map GM-50 (Joe Dragovich & others. 2002). Geologic Map of The 30' by 60' Seattle Quadrangle. Washington. United States Department of Interior United States Geological Survey (USGS). dated 1991. Coastal Zone Atlas of Washin~on. Jefferson Count>,.', Washin~on Department of Ecology. 1979. Relative Slope Stability in East-Central Jefferson Count,. Washington map bb' R. U. Birdseve dated 1976. Krazan & Associates, Inc. Eleven Or'rices Scrxing The ~3,'estern L'nited States DABOB BAY .. ~" ~ Zetatched P~ ~ Tsku~sko Pt.:: ~:~'"' ' I .---- ..... . ~ ,". ~ o.. a, ,' .t ~ -~ · ~ , ,~,, ~-~.:.~> ~: ~ ~' ~ ~ ,, . . ~ ,~,-,~ ~ ~-,. _ _ ~: ':..( . Oa~ Head HOOD CANAE Map adapted t~om USGS 7.$ Seabec~, WA. Quadrangle da[cd ] 953, pho[orevised 196g and phmoinspec[ed 1973. FIGURE I - VICINITY MAP KRAZAN & ASSOCIATES, INC. 20714 State Highway 305 NE. Suite 3C Location: Quilicene, Washington POULSBO. WA 98370 Job No.: I02-02097 360-598-2126 Client: Mr. Richard Grandv Date: 9-23-02