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Home My WebLink AboutBLD2006-00092 Geotechnical Report /13/06 12:05 FAX 1 36064 3744 STRATUM GROUP • 0302 STRATUM GROUP 1451 Grant Street,Bellingham, WA 98225 Phone(360)714-9409 March 13, 2006 _mes and Sue Bond J apiter Loop ,_non, WA 98320 I� Re: Geotechnical Report Tax Parcel 502152003 140 Jupiter Loop Brinson, Washington Case#MLA0600093 Dear Mr. and Ms Bond: t._tum Group is pleased to present the results of our geology evaluation of Tax Parcel 502152003 at 140 Jupiter Loop south of Brinnon. Washington. The purpose of this geology evaluation was to evaluate the risk of slope failures impacting proposed development on the subject property and to provide general site maintenance recommendations for the property.This evaluation included a visual inspection of the property and vicinity and review of available i.eologic mapping in the area. property is located on the east side of the Olympic Peninsula on a slope above Hood Canal. l Vocation of the property is indicated on Figure 1. The property is located in the northwest cuarter of Section 15,Township 25N, Range 2 West W.M. SCOPE OF SERVICES The scope of our services included the following: 1) Conducted a site visit to visually inspect the subject property including slope conditions and relevant conditions in the vicinity of the property. 2) Observed surface soil conditions on the slopes of the subject property and vicinity. 3) Prepared this report summarizing our findings, including a qualitative evaluation of the stability in regards to the proposed garage and residence on the property, recommendations for site development, and recommendations for further investigation, if necessary. GENERAL GEOLOGY Northwestern Washington has been occupied by continental glaciers at least four times during 03/13/06 12:05 FAX 1 36647 3744 STRATUM GROUP 03 • March 13,2006 Tax Parcel 502152003, Brinon,WA Geology Assessment the Pleistocene Fpoch(1.6 million to 10,000 years ago). During these glacial and accompanying interglacial periods,the underlying bedrock was deeply eroded. Glacial related deposits were deposited over the bedrock in various places on and in the vicinity of the subject property. The Geologic Map of Surficial Deposits in the Seattle 30' by 60' Quadrangle, Washington 'Yount, Menard and Dembroff, 1993)indicates that the subject property and vicinity is underlain by glacial till and bedrock. Observations on the subject property are consistent with this mapping. - The property is underlain by a veneer of glacial till very compact ice-contact deposits over bedrock that consists of basalt_ The Bedrock Geologic Map of the Seattle 30' by 60' Ouadrangle, Washington (Yount and Cower, 1991)indicates that mapped bedrock in the vicinity is basalt of the lower Eocene Crescent Formation. The proposed building site is underlain by glacial till. Bedrock basalt is exposed just to the north -f the building area The building site is a level building pad constructed of fractured bedrock The till deposits consist of cobbles and boulders within a matrix of sand silt and clay. -1 e till is very compact and hard. The till on the site is well exposed in the cut slopes on the -3roperty. SPECIFIC SITE OBSERVATIONS The subject property is located on a slope above Hood Canal and U.S. Highway 101 on the west side of Hood Canal. The property is accessed via Jupiter Loop Road, a spur road off of Mount Jupiter Road. The proposed building area is located on the upper northeast portion of the property at an elevation of approximately 400 feet. At the time of my site visit a cleared and level building area had already been completed on the site for the home site. The graded area is underlain by glacial till and bedrock fragments_ The building site is accessed by a short driveway off of Jupiter Loop Road located northwest of the building site area. The slope below the level building consists of fill soils pushed out over the slope below_ This slope is approximately 20 feet high and slopes down towards the southeast at an angle of approximately 30 degrees. Otherwise slopes on the subject property surrounding the building area are 20 degrees or less and are well vegetated with a mix of trees and thick underbrush. hazardous or potentially hazardous slopes were observed anywhere on the subject property. &mum Group Filc:2.13.06 2 /13/06 12:05 FAX 1 36047 3744 STRATUM GROUP 04 March l3,2006 Tax Parcel 502152003,Brinon,WA Geology Assessment CONCLUSIONS AND RECOMMENDATIONS is my opinion that proposed building area on the level building pad area of the property is -'a',?.e and that the proposed construction will not be at risk from landslides or other slope a ,• .ty problems nor will the proposed development on the property cause any instability on :-her slopes.No potential geologic ha7nrds are present on the subject property in the vicinity of the building area. -the building foundations should be set back from the down slope side of the level building area at least 10 feet in order to minimize differential settlement that may occur along the outer edge of the level building area. crrr water run off from the roof gutters and road access as well as drainage should be routed to a dispersion area either east of the building site or at the base of the fill slope below the building area. The proposed septic drain field is located in are no at risk from potential landsliding and the introduction of water at that location will not cause slope stability or erosion problems either on site or off-site. Please note that there are inherent risks associated with lots near or adjacent to steep slopes. These are risks that the building owner should recognize and be willing to accept. If conditions -tanear different than those described in this report, or other concerns arise, we request that we be ed ;o we can review those areas and modify our recommendations as required. t:21um Group appreciates the opportunity to be of service to you Should you have any uestions regarding please contact our office at(360) 714-9409. Sincerely yours, -0-k Vi a:Nr , Stra7 Group 7 f am! / /is1�� *t Dan McShane, L-E. .,M.Sc. • ,i�cnsed Engineering Geologist / •°wing Geologa`_zrw' �• 6� + r VA - - :_- Dana Stratum Group File:2.13.06 3