ARCHIVED REPORTS 2nd QUARTER 2011 QUARTERLY REPORT

Home Browse Search

Site Background Information: Herman and Helens Marina Page 2 of 13 respectively. Additional information can be found in the Condor Earth Technologies, Inc. (Condor)-prepared Tank Pull Testing Results, dated 18 November 1991. Based on the contamination detected in the soil samples collected during the UST removals the San Joaquin County Environmental Health Department (EHD) directed the investigation of the TPH-g and TPH-d contaminated soil. STRATIGRAPHY With the exception of approximately 20 feet of built-up levee material along the western edge of the site and a gravel zone (fill material) beneath the ASTs, the general soil stratigraphy consists of an uppermost peat layer, ranging in thickness from 6 feet east of the ASTs to 20 feet beneath the levee material, underlain by sand layers at approximately 30 feet, 70 feet, 93 feet and 102 feet below the maximum surface grade (bmsg), as measured from the top of the levee, and fine-grained soil at approximately 40 feet, 83 feet and 95 feet bmsg. The upper 15 feet of built-up levee material consists of dry, brown, poorly-sorted coarse- grained sand underlain by dry to moist, tan to dark brown silty sand with gravel. Between 15 to 20 feet bmsg the soil consists of dry to moist, tan to dark brown silty sand with gravel. The peat layer consists of moist to saturated, black organic peat, oftentimes fibrous with grass or straw material, that is laterally continuous, extending eastward from beneath the built-up levee material to form the surface layer; the exception is along the eastern edge of the AST enclosure, where apparently a substantial amount of the peat has been removed and replaced with up to 7 vertical feet of clean gravel. Previous geotechnical testing of soil samples collected from this peat interval (Advanced Geo Environmental, Inc., 2003) indicated very high porosities (85% to 92%) and organic contents (76%to 88%), but very low average permeabilities, ranging from 10-6 to 10-7 centimeters per second (cm/sec). In general, the sand layers at 30 and 70 feet bmsg consist of greenish gray to black, saturated, fine- to medium-grained, poorly-graded sand. The uppermost sand is finer- grained, consisting of blue-green to green-gray, damp to saturated, silty to fine sands; previous geotechnical testing of soil samples collected from this layer indicated soil porosity of approximately 30% and low hydraulic conductivities of 10-7 cm/sec (Advanced GeoEnvironmental, Inc., 2003). The intermediate sand layer at 70 feet bmsg is a black to gray, saturated sand which appears to coarsen from fine- to medium-grain with depth. Sand types below 90 feet bmsg are based on CPT logs; the thin sand layer at approximately 90 feet bsg was identified as a dominantly silty sand, and the lowermost sand consisted of interbedded layers of silty sand, sand and cemented sand. Advanced CeoEnvironmentnl,Inc.