3206 WAVE DR 2016-01-01 MF Import

GeoTesl Services,Inc. June 3, 2005 Baldwin Residence,3206 Wave Dnve, Evereri,WA Job No. 5233 Site Soil and Groundwater Conditions GeoTest Services, Inc. conducled iimiled site explorations during the time of our visit. Our subsurface explorations consisted of three Dynamic Cone Penetrometer (DCP) tests in order to help evaluate the subsurface soil densities within the existing wall locations and the proposed upper wall location. A DCP probe includes recording the number of blows necessary to advance a pointed steel rod into the ground with a 35- pound drop hammer. Thie blows necessary to advance the rod into the soil have been correlaled with the density of granular soil deposits and the consistency of cohesive soils. The ihree DCP tests were conducted along the middie bench poriion of the existing wall system. The three DCP tests were conducted to maximum exploration depths of 4 feet 8 inches, 6 feet and 3 feet 4 inches at DCP-1, DCP-2 and DCP3, respectively. A distinct change in density was observed in all three test locations. At DCP-1 and DCP-2 the contact was interpreted to be between loose, possible previous fill soils, and more compe!ent native soils at a depth oi 4 feet below existing ground surface (BGS) and 3 feet 4 inches at the two locatioiis. The change in density observed at approximately 1 feet 4 inches BGS in DCP-3 was interp �:ted to be between the upper more loose native slope soils and the underlying more competent undisturbed native soils. Logs of the DCP analysis are included in the appendices of this report. A�ao refer to the Site and Explorafion Plan, Figure 2, for more detail regarding exploration lucations. Observed soils within the unfinished wall section appeared to be native cut areas consisting of moisl, light brown siltylclayey sand with gravel and trace cobble or boulder. The undisturbed native soils were medium dense to dense and appeared consistent v. th glacial till mapped in the area of the property. We understand that some pravious fill soils andlor debris may also have been present within the northern portion of the existing wail locations. We are unsure if all of the potential previous fill soils or debris was removed prior to the construction of the originai H all system. Groundwater seepage was not encountered within any uf the explorations conducted during our site visit. We would expect that a regional groundwater level would not be encountered within the scope of this project. However, incident stormwater runoff perched at the contact of looser near sur(ace soils or within previous fill soils and the denser till-like soils may be encoun;ered depending on the time of excavation. Groundwater seepage may be expected to emanale trom sandier zones within the native soils, as well as from random locations in existing fill soils, and at the contact between fill and underlying native soils. Groundwater levels are not static and vary with respect to surface runoft, precipitalion, season, changes in sile utilization, both on and off site, and othEr factors. Tlie retaining wall design recommendations provided herein are based on the findings of our limited site exploralions. Accordingly, we recommend that competent personnel monitor construction of lhe retaining walls and that contingencies for differing site condilions be incorporaled into the project contract documenls lo aliow for necessary changes in design and cons!ruction methods. , Page2of7 �i , �