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Home My WebLink About001302009 Geotech Assessment (2003) SEATTLE RICHLAND SHANNON WILSON INC Ill GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS ANCHORAGE I~ · DENVER SAINT LOUIS BOSTON I EC VED July 2, 2003 JUL 0 ti 2003 Mr. Jerry Haskins 191 Lane DeChantal Port Townsend, WA JEFM$ON COUNTY 98368 ADDENDUM TO GEOLOGIC EVALUATION OF SLIDE AT OF 191 LANE DECItANTAL, PORT TOWNSEND, WASItlNGTON, AND PROPOSED SEPTIC DRAIN FIELD LOCATION (CASE NO: MLA03-00252) Dear Mr. Haskins: This letter serves as an addendum to our geologic report for your property at 191 Lane DeChantal. A landslide occurred on the waterfront slope west of the existing residence on your property in February 2000. At your request, we evaluated the cause of the landslide and the relative risk of slope movement impacting the existing residence, .and Provided. general · . ... ... .~ .. - -} i .: ~' recommendations to reduce, the risk of future slope movements. This Work WaS summarized in a le~t~} :r~p0rt'}°'Y°u dated June 22, 2000, which also included a description of the site, tOPography:, geologic Conditions, sPrings, and'seeps. We understand that you propose to construct a septic drain field at the above-referenced site for an auxiliary dwelling unit (ADU). We understand that the ADU will be located on an adjacent property to the east on Cape George Road. The proposed location of the septic drain field for the ADU is on your property, 191 Lane DeChantal, between Cape George Road (to the east) and Lane DeChantal (to the west). We also understand that the Jefferson County Department of Community Development requires an evaluation of the impact of the proposed septic drain field on the stability of the slope on the site. At your request, we have performed this evaluation and have prepared this letter as an addendum to our previous report. Based on our understanding of the geologic conditions as described in our June 22, 2000, report ' ' he '~0 o~ed location of the septic drain field, it is our opinion that the proposed drain field an.-dt: . ~-P-~: P~.. - ~;' ~.~.,'~' ~i~'~.i~,.,-~ ~aiacent ~ror~ertieS Or significantly increase.the..ns~°f. wili'not a~versely aliect me staumty u~ -,~a r ~ .... . ... :. ~ ' ..... -.. ~ioPe rn~)embnts at the site.' This oPinion iS based in part on the relativelY long distance 21-1-08976-002 400 NORTH 34TH STREET · SUITE 100 P.O. BOX 300303 SEATTLE, WASHINGTON 98103 206.632-8020 FAX 206.695.6777 TDD: 1.800.833'6388 Mr. Jerry Haskins July 2, 2003 Page 2 SHANNON 6WILSON, INC. (approximately 300 feet) between the proposed drain field and the head of the slide scarp that developed in February 2000 and the relatively low discharge to the septic drain field typically expected for an ADU. We note that according to published U.Si Department of Agriculture (USDA) soil maps, surficial soils in the vicinity of the proposed septic drain field are classified as Tukey series soils with slight to moderate erosion hazard. Provided that prudent construction practices are used, it is anticipated that construction of the proposed drain field will not significantly affect soil erosion and associated hazards on the site or pre-development drainage conditions on adjacent properties. Please refer to our June 22, 2000, report for additional recommendations and limitations of the report and this addendum. If you have any questions regarding our observations, conclusions, or recommendations contained in the June 22, 2000, report or this addendum, please cai1 me. Sincerely, SHANNON & WILSON, INC. Perkinsi William J. Perkins, L.E.G. Senior Principal Engineering Geologist WJP:GJB/wjp 21-1-08976-002-LI/WP/LKD 21-1-08976-002