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HomeMy WebLinkAbout901034010 Geotech Assessment STRATUM GROUP 1451 Grans Sued, uellint;hara. WA 91ms Phase (360) 714 9409 October 25, 2005 Lukc Snyder 22080 Anderson Lake Road Chimacum, WA 98325 Re: Geoh>p~ Evahtatioo S P A ey - c o c a `~ Tax Patie1 901 03401 0 Jefferson County, Washington near Mr. Snyder: 1 inspected the slope end geologic conditions on Jefferson Cottttty Tax Parce1901034010 in order to evaluate the impacts of toasttuctirtg a road across the slope to excess abtriWing site at the top of the slope. This visual inspection incbtd~ a visual inspection; of the steep slopes on the property and in the vicinity of the property, hand dug test pitsbn the slopes of the property to determine soil types and the underlying geobgy and review of available geologic mapping is the ~. The. subject pto-aaty is locaxd on the west side of Chimacum Valley. The lower portion oSthe property is lomted on the nearly flat valley floe. The property amends up the west slope of the valley to the genie sloping uplands above the west side of the valley. The proposed road ott the subject property is to provide recess to the gearle upland area from the valley flow portion of the property. The location of the subject propeety is indicated on the ettaclted Figtne 1. Figure 2 is a sketch map provided by yon indicating the proposed route of the road. GENERAL GEOLOGY Northwestern Washington has been oecopied by catttir-ental ghteiers at Itmst four times dating the Pleistocene Epoch (l.b million to 10,000 years ago). Ihuing these ghtcial and accompanyi»g interglacial periods, the nrrderlyirtg bedrock was eroded and a relatively thick layer of glacial related and interplattial fluvial seditttents were deposited over the ttoderlying bedrock in the vicinity of the subject property. The h[ortt+raa>m Jcffacon tim>v W elti~g (Gayer-1976) indicate the subject property is underlain by three uoits_ 1) Reressonei-CoMittemal Detwsits, 2) Advance Urivuas-t Dapo~ts and 3) Till_ Observations on the subject property are taatsistent whit the mapping ttt'scribed above. The Recessional-Continattal Deposits ~e described as c~sisting of poorly to well-aortal sand, g. oee>ba~s.aees Thx Paml9elafYwle:;ldmCawo'. irA Citatagy IMaard ©wbwM~ gmvd, and alt dapodkd P by merit vtala fiam the s~6 Vnhoo-sge ice ~ Tlaeae depodn covr4e floor of t Vslky and 16e loaiapoRioa dthe aobjxtProPn'~f• The lacer dopes dtbs salley tide ~ dte atbjeotpeopaq~ nee mdalia by Advmtt Otdwaeb These depend re daeribad s maaiCiai ~~. Yavrd. s~ and ehq depodmd by reek went 8owia im ~ advaaag ice merlin dthe ~t bba a~fYas6oa age. Thrs n~ am is ibe raoesrioani o~aa~ depaeit:llavtever, bocaae thgdve bcea overridden bP ghneiai ice they ana geataYy ®e compact madmen. The upland tas dthe pmpaty and~e nppa daps dthe valley aide ero tmdalaia b! h'LL The iifi maiele oFapoady soAsdashdtae daodc 1'tsgmml6 dopoeeed dra$~ by ~ Vaahm-age im mlal. Frraon Wilde fit. ~d ®d day>o varis6ie propatiooc aoaaWudaig a modenta191o highly compact pratht dvPhieh the mesa noeditaeots ae fmmly -. emboddod. The L~sD'eG 19717 mdicata that the dope on the aubjeetpmpaty is baled w~ ~ mess desiaus0ed a paoraaad atidatity 1'he tgdod sbpea, tmlaod res and the valicT floc atria die sd>;mx ptapaty ate dedgoamd ss stable swdle dopes. . srEC[RCC errs oB~avwzltoNs Tbepropoaed cad aegla sp the ebpe fltmt mebtne die hll scathe foaAt propnry tawoa. the mtrbwer m $nwed properly lined then ewieehPa haelcto towards the noolhveeet m the sop dthe slops The bwr part dthe abpe sul the appapett dine slops am gmda The ateepast po.ties dthe slope abpm ae m eagles dappro>t~ely 35 dt~reee The hdglrt rime 35-degta pm6aa dthe abpe is appioor~ ~0 feet'rbe dope b pleiae' ®dutwvated>shh a stead ofamrre aarord growth forest, No apnioga or streps a arse ofmaagene topogwpby era pnasmt on the slope mtha aabjeetpropaty The elope is tetdedsm hyssm! snd gtavd ~ I hrteepret m he adtrma: amam~. send aced gravel. The appapetr d$e dept i9 undedda by dhY awdy gmvd vri~ scaleaed boddnsa that I interpret m be glsndd rid TJteee ere ao htd;eetboa ddope hMability ~ the dope miaept t6r miter shaMwv ant3m soil tsaep• eevtad rid akld roads arm praea w the sbpemggw adtject prepay: Tsacxpt far attoorrevNiol etas slopes the old logging sled rwda ere aorrovstg,own with vngmaic® ~ are anbk. No arideme (tmden undo at tnxs mined iawrd away firm ~etop diha bhrff'sriat>ia ofpert gdiR a#the beach ara~ iod4~pg of i~piearglohal.type or dapseeted feilma is as.r~ Pac laa~mP ramntiae Pea 1a21.aiF OCT 31 Z005~ I ~, R oaxa,arzs,suos Tax 1'aree1901034010;, 7dWsas CwLLy, WA Gwlaay HwaIIM gvataaUon located on the subject property. CONCLUSIONS AND Based on my inspaxion of the subject property. I oottclade that a road can be oonatructed uP the slope ie such s manner that the risk of causing landslides or the road being impacted by landslides is minimal. The road .vill require cutting into the slope the sheep slope. If full bench cuts ate used, the heigbx of the cart slopes will be a t of 9 feet tyith the majority of hie eut slopes on the road being substantially less. Cut and fill coasavtxion of the mad will have much reduce the cut slopes by half: The slope stns will be into corr-pect sand sod gravel. Minor raveling should be exported from the art slopes onto the road surface and may cause sane mitmr increases in slope «cep rate cear the top of the cut slope. Likewise some minor soil raveling and soil creep should be expected on the fill slopes. Tree removal on the slope will rot caue~e auy slope stability pmbleins as long as snvnps ate left in place and not pulled from the ground. !f conditions appear different than those described in this report, or other cotttxms arise, eve that we be notified so we can review those mess and modify imr tecatrrmendatioos as required. Stratum Group appreciates the opportunity to be of service m you. Should you have any gtrestiarrs regarding this assesmrertt please contact our office at (360) 714-9409. Sincerely Yours, Stra m Grertp Dan McShane, M.Sc., L.E.G. I.iar~sed Engineering Geologist srrr. caoy _ File IaZ1.O3F s K