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Home My WebLink AboutBLD2005-02016 GeoTech Assessment Report - BLD Engineering / Geo-tech Reports - 2/27/2006 S �oN ararFo� MASON COUNTY M o PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER o T T Shelton, Washington 98584 r N Y Y p 8E KEPT O N THE , 4 � RCc �� DATE: February 27, 2006 pq INTER-DEPARTMENTAL COMMUNICATIONS TO: Chuck McCoy PARCEL #22330-50-00301 FROM: Alan Berbisco, Project Engineer-PW BUILDING PERMIT NUMBER: Bld2005-02016 SUBJECT: Geotech. Assessment Report NAME: Craig Johnson Chuck, The Geotechnical Assessment Report prepared for the proposed single family residence located at 210 NE Haven Lake Drive Tahuya, has been received and reviewed by Public Works. The Assessment Report appears to satisfactorily address the County requirements for geotechnical reporting. The site has an approximate slope of 30 to 40%. According to the author, there were no indications that suggest past landslides had occurred on or immediately adjacent to the subject property. In his opinion, the site in a predevelopment condition would be considered as stable and the proposed development will not increase the potential slope instability on or adjacent to the site, provided that the surface water runoff from the development is properly controlled. There were no recommendations from the author on how to control the stormwater runoff. Stormwater management features should be incorporated to site development plans and made condition for permit issuance. Please feel free to contact me at 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Sincerely, Proje t Engineer I WORK 0ka8R •'PU8Ll0 WORKS DEFT. . 4tj. date: (� wolt Order PP.NMIT •""w"7� L c� — , ' N m n uWsd Q(-W YV C- , A razed by o01e0 Type of WOW., �,�, 7 7 v r 1' I CHAR08 TQs NAME L .�c� AGENCY/COMPANY •. BIUUN4 ADDRESS . PNONN r � Fmied 0 e1(TMM•to do,*$) pool i1MUMwbic ; ; ' WAn diFlnMlh Oslolow hotr�lo EiT>%TE0MAL t ldI ! .._.� t8r<ttt• 11M SAW mum_M- a i WlR 6mplin i US ..Il�l.l�rrr rniwlr • rrrrrlrrr.�r� r�riw.�OYnr�rrn� ' . - -lilr'.rrrrrrl�.ar.�:r�.rr■I■ r.rl�rrrlr.�ulll. . IEQUIPMENT USED: Ilia! BA 19TU 1.1 ' �.rrr..�Y�r II��1 Irrrrl 1• Mrr..wrrYrwr.w • �� MATINNAVIE TOTAL,lull, a • a l uea DATE PAlo.allTi LANDAU ASSOCIATES February 7,2006 Craig Johnson P.O. Box 2217 Bremerton,Washington 98310 RE: GEOLOGIC ASSESSMENT REPORT 210 NE HAVEN LAKE DRIVE MASON COUNTY,WASHINGTON TAX PARCEL No.223305000301 Dear Mr.Johnson: The following summarizes the results of our geologic assessment of the landslide hazard at the above-referenced property. The purpose of our services was to review available geologic and topographic information in the project vicinity, complete a field reconnaissance of the subject property, and address the requirements for development within a geologic hazard area per the requirements of Chapter 17.01.100 Section EA of the Mason County Code. SITE RECONNAISSANCE On January 17, 2006, a representative of Landau Associates completed a site visit to observe existing conditions as they relate to a landslide hazard. The following summarizes our observations. The subject property is located along the southern side of NE Haven Lake Drive. The subject property is rectangular in shape. From the southern property line, the site is relatively level to about the middle of the property, where the site slopes downward about 15 to 20 vertical ft to a relatively level area where the septic system is to be installed. The slope was visually estimated to have a gradient of between 30 to 40 percent. Near NE Haven Lake Drive, the site slopes gently downward to the road. The attached photographs illustrate the general site topography. At the time of our site visit, the majority of the site had been mostly cleared and stripped, except for a patch of vegetation along NE Haven Lake Drive. An embankment had been constructed along the western edge of the property to access the upper portion of the site. The embankment side slopes have been planted with grass. The slope in the mid potion of the site has been partially covered with straw. The upper portion of the site had been leveled and the excavation of the house foundation had been completed and the water well had been installed in the southwest corner of the site. Though the site had been recently stripped of vegetation and there has been a significant amount of rainfall since mid ENVIRONMENTAL I GEOTECHNICAL I NATURAL RESOURCES 950 Pacific Avenue,Suite 515 • Tacoma,WA 98402 • (253)926-2493 • fax(253)926-2531 • www.landauinc.com SEATTLE • SPOKANE•TACOMA• PORTLAND December 2005, we did not observe indications that active erosion of the surface soil was occurring on the cleared portions of the site. Based on soil conditions observed in cleared areas and in cuts at the site, the surficial geology at the site consists of relatively thin veneer of glacial recessional deposits overlying glacial till (hard pan). The thickness of the recessional deposits was observed to be about 1 to 3 ft in exposures at the site. Recessional deposits were observed to consist of reddish brown,poorly stratified, loose (where disturbed) to medium dense, gravelly to very gravelly sand with variable silt content. Glacial till exposed in cuts in the vicinity of the proposed residence and in a portion of the foundation excavation for the proposed residence consists of gray, very dense, silty sand with variable gravel content. No indications of groundwater seepage were observed at the site at the time of our site visit. SLOPE STABILITY The slope in the middle portion of the site is about 15 to 20 vertical ft in height and has a relatively uniform slope gradient. There were no indications that would suggest that past landsliding had occurred on or immediately adjacent to the subject property. In our opinion,the site in a pre development condition would be considered as stable. The proposed development will consist of constructing a residence in the upper, relatively flat portion of the site with a septic system in the relatively flat area at the toe of the slope in the middle portion of the site. In our opinion, the proposed development will not increase the potential slope instability on or adjacent to the site provided that surface water runoff from the development is properly controlled. Uncontrolled surface water runoff can result in significant erosion and possibly shallow, surficial slope failures of the weathered soil on the face of the slope. The site is underlain at shallow depth by glacially consolidated soil which is generally not prone to deep- seated slope failures. USE OF THIS REPORT This geologic assessment was prepared for the exclusive use of Mr. Craig Johnson for the proposed development located at 210 NE Haven Lake Drive in Mason County, Washington. The use by others, or for purposes other than intended, is at the user's sole risk. The findings, conclusions, and recommendations presented herein are based on our understanding of the project and on conditions observed during our January 17, 2006 site visit. Within the limitations of scope, schedule, and budget, the conclusions and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical engineering principles and practices in this area at the time this report was prepared. 277/06 I:\DATA\PROJECT\960\001\210 NE Haven Lk Dr\210 NE HL GA.doc 2 LANDAU ASSOCIATES We appreciate the opportunity to be of service on this project. If you have any questions, please contact the undersigned at(253)926-2493. �g9 A t ' LANDAU ASSOCIATES, 0 a: Edward J.Heavey, P.E. ,0 8M5 Associate �s910 AL �G EJH/jas NOIRES p ,p Attachments: Photographs(3) 217/06 I:\DATA\PROJECT\960\001\210 NE Haven Lk Dr\210 NE HL GA.doc 3 LANDAU ASSOCIATES Photograph 1 —Slope in middle of site. Looking southeast from near NE Haven Lake Drive. Photograph 2—Lower portion of site and septic field area. Looking northwest from upper portion of site toward NE Haven Lake Drive. 217/06 I:\DATA\PROJECT\960\001\210 NE Haven Lk Dr\210 NE HL GA.doc 4 tANDAu AssocIATES Photograph 3—Upper portion of site. Looking southeast from top of slope in middle of site.Note glacial till(gray soil)in cuts. 217/06 I:\DATA\PROJECT\960\001\210 NE Haven Lk DA210 NE HL GA.doc 5 LANDAU AssocIATES