SITE INFORMATION AND CORRESPONDENCE FILE 1

Home Browse Search

w 03 August 1999 AGE-NC Project No. 95-0121 Page 2 of 6 hydrocarbons were present to depths in excess of 19 feet below surface grade (bsg). 2. 3 . PREVIOUS INVESTIGATION A total of nineteen soil borings were advanced at the site between May 1989 and December 1994; nine of the borings were completed as two-inch diameter monitoring wells (MW- 1 through MW-9). Extensive hydrocarbon-impacted soil and ground water, including free product, were encountered during assessment of the site. In July 1995, one dual-purpose soil vapor extraction/ground water extraction well (EW- 1 ), and two soil vapor extraction wells (VW- 1 , VW-2) were installed at the site. In August 1995, an 8-hour soil vapor extraction (SVE) test was conducted at the site. The pilot test was performed to provide vapor extraction data for proper system design of a remediation system. Details of the SVE pilot test were included in Corrective Action Plan (CAP), dated 14 November 1995 , prepared by AGE. Additional background information has been prepared by AGE and summarized in the June 1998 (dated 20 July 1998), September 1998 (dated 29 October 1998) and December 1998 (dated 29 January 1999) Quarterly Reports submitted to PHS-EHD. 2. 3 , REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough. The Great Valley Province has been I� filled with thick sequences of sediment ranging in age from Jurassic to Quaternary, creating a nearly flat- lying alluvial plain, extending from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively. Rocks composing the basement complex of the province have not been completely defined but are believed to be metamorphic and igneous in origin. The northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively. Based on the General Soil Map from the San Joaquin County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Jackson-Hallenbeck-Stockton (JHS) association. The JHS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils. The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from mixed rock sources . Advanced GcoEnvironnental, Inc.