11419 19TH AVE SE Geotech Report 2018-01-02 MF Import

�� 1 � 3.0 Suhsurfacc F.splor:ition, continucd that differing subsurf�icc conditious might sometimes be present due to tlie random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of � any variations beriveen the field explorations may not becomc fully evident un[il construction. r � If variations are observed at that time, it may be necessary to re-evaluate specific recommendations I in this report and make appropriate changes. To reduce Ihe potential tor settlement of the soil backfill that was placed in the exploration pit excavations, a vibratory hoepac was used to compact i � the back5l! in each exploration pit. The comp:,cted backfill in the exploration pits was in a firm, unyielding condition wlten completed. � 4.0 Stratigraphy ' The eleven exploration pits accomplished for this study penetrated &om 3 feet to 9 feet below � existing ground surface. In die vicinity of the r�u proposed buildings nearest the pond (buildings B and C), we encountered one to two feet of sandy gravel fill and/or medium loose to dense silty sand with gravei (weathered glacial till). The fill was encountered in the exploration pits rsearest the � existing structures and is probai�iy due to past grading. Below these su�cial soils we found dense undishirbed glacial till with increasing moisture content as depth incrensed. At EP-1 [he gIacial till sediments encountered at 7 feet below ground surface were saturated. At EP-4 !south end of � proposed building ^) the surficial soils (topsoil and�veathered till) were in a very «�et state, also. .vt tiie sloped undeveloped area(east end of proposed building A), in the N.E. comer of the site, EP- � 7 and EP-8 revealed one foot of topsoil ana or fill followed by two to two-and-a-half feet of reddish brown silty sand with gravel and roots. These soils manded dense to very dense glacial till. � Two expioration pits were excavated below the existing asphalt pavement at the �vest end uf the proposed building A. EP-9, at the east zdge of the pavement, was similaz to EP-7 and EP-8 except � for approximately one foot of fill above the native soils. At EP-6 three feet of firm fiil was encountered directly below the asphalt section, foltowed by nvo feet of soft reddish brown silt with bumt wood debris; then dense native glacial tilL The Site,�nd Exploration Plan, Figure l, shows the � approxir.�ate limit of the soft silt encountered. The esact lateral extent of the soft silt layer could not be determined during our expioration. � 5.0 Hydrology Very minor seepage�vas encountered in some of the exploration pit�at the interface of the fill soils � (or weathered till) and dense native till. We suspect this seep��e is due to recent raintall,which had not yet been absorbed into underlying and less permeable soils. This seepage could be expected to ftuctuate with changes in rainfall and season. At the exploration pits excavated near the pond(EP-1, � EP-3, and EP-4), the increasing moisture rontent of the till sediments with depth indicated groundwater. At EP-1 completc saturation of sediments and seepage was noted at approximately seven feet below ground surface or elevation 426. ' ' �6 � MAYES TESTING ENG/NEERS