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Home My WebLink AboutBLD2012-00098 Geotechnical Report FILE COPY Precise Engineering Inc. I(1I I Mellen Street '' Centralia, 11'A 9)853I 36(1-73(1-1137 '= Fax 3(111-807-(1I118 March 7, 2012 Richard & Jeanine White 173 Nicole Smith Lane Brinnon, WA 98320 RE: Existing Ecology Block Wall Dear Mr. Phil White Based on the sketch that was provided and information provided by the contractor and the soils report from Bradley-Noble Geotechnical I performed a structural analysis of the existing ecology block wall. The existing wall is structurally stable with exception of the required vehicle barrier at the top of the wall. A residential vehicle barrier is required to accommodate a 6000 pound point load at 18" above the existing grade. In order to provide adequate resistance for this load a concrete cap will have to be added in order to spread the load to a larger portion of the wall. See the attached detail. If you have any questions, or if I may be of further help, please call me at (360) 736-1137 Sincerely yours, Precise Engineering c. .7 H. . / HAROLD HAHNENKRATT, PE •Ok I -� Principal %F. 7�0 ssoIsles 40� NAL 1 08/11/2007 00:36 4320181 SUNRISE PAGE 01/02 Bradley-Noble Geotechnical Services A Division of The Bradley Group, Inc. PO Box 12267, Olympia WA 98508-2267 Phone 360-357-7883 • FAX 360-867-9307 23 February 2012 Mr. Chuck Rutherford Sunrise Custom Cabinets 70 E. Heatherwood Court Shelton, Washington 98584 Subject: Geotechnical evaluation of the ecology block retaining wall constructed at the Richard &Jeanine White property, 173 Nicole Smith Lane, Brinson, Jefferson County, Washington. Dear Mr. Rutherford: This report will summarize our field observations of the ecology block wall constructed on this property. The wall was constructed using standard concrete ecology blocks. From our field observations, it appears that the base of the wall was set onto an excavated pad which extended to the basalt bedrock unit of the Crescent Formation, the bedrock unit for the Olympic Mountains. We noted that the construction resulted in a slightly concave arch towards the slope. The wall was constructed by stacking two blocks, then setting the next two blocks back so that the base block was behind the key of the lower block to increase resistance to sliding. This process was continued for six blocks of height. The top block is a single height and this block is also set behind the key. Behind this block is a level crushed rock fill section that will be used for parking. In general, we found the main block wall to appear to be stable and we did not observe any indication of settlement, bulging, or other distress to this section of the wall. The base block of the main wall is at least half height or more buried. We did observe that the north wing-wall, also constructed of ecology blocks has experienced some settlement and deflection. Based on our observations, this settlement is likely caused by construction on the wall backfill material. A footing drain does exit the wall backfill above the second block level on the north side. We do recommend that this drain line be extended to the toe of slope so that in the unlikely event that this line does carry storm water, it is not discharged onto the slope which could cause slope erosion. Below the base block, the slope does continue down. This natural slope of colluvium over bedrock is estimated to be about 1.5:1 (horizontal to vertical) below the north half and about 2:I (horizontal to vertical) for the south half 1202050I Page I of 2 y,, r • FILE COPY 08/11/2007 00:39 4320181 SUNRISE PAGE 01/01 12020501 Page 2 of 2 We expect that the wall was constructed by excavation of the colluvium and loose bedrock material. We expect that the resulting cut slope was steep to nearly vertical. We also expect that the thickness of the backfill behind the wall is at the most four to five feet in horizontal thickness before bedrock would be encountered. 'Nith the support of the main wall by a bench constructed in the bedrock, we do not expect that bearing capacity of the supporting material of the wall is an issue. The wall has a general batter back of about I:12 (horizontal to vertical). The wall backfill is a mixture of smaller angular basalt and colluvium. Based on observation, we estimate the angle of internal friction of this backfill material to be in the 40 degree range. In addition to the active soil pressure by the backfill, the wall will also be subjected to surcharge loading by vehicles. We recommend that this surcharge loading be equal to a uniformly distributed load equal to one foot of soil. We understand that this wall is about I to 1.5 years old. Other than the settlement of the blocks of the north wing wall which is supported on the wall backfill, the wall does not show signs of distress. We also discussed foundation support for the proposed new garage. At the time of our site visit, the building pad for the garage had been prepared and the surface finished with crushed rock. To ensure uniform soil support for the garage and to key the footings adjacent to the slope, we recommend that the footing lines be trenched to the bedrock. Footings may be either constructed on the bedrock and stem wall used to bring the foundation to plan elevation or the footing excavation may be backfilled to plan bottom of footing grade with either CDF (Controlled Density Fill) or lean concrete. We recommend for backfill using cementitious fill material that the width of the excavation be a minimum of three inches wider from each footing face to provide lateral support. We have discussed our observations and recommendations with your design engineer. If you or Harold have any additional questions, please contact us at our Olympia office. Cordially, BRADLEY-NOBLE GEOTECHNICAL SERVICES .> '!,. ..,,, . ;, co 144/-**,?--...___._. -.),!:; 4..\, David C. Strong, L.E.G. Vkittstits„„<....:1'': °°a"'*'""i+GecAn�g6i `'Jr 'seer'' re'' fit V Pr`k 17' ...��i.„