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A S S O C I A T E S I N C In November 1998, ATC supervised the advancement of two soil borings to 78 feet bgs and one soil boring to 86 feet bgs Soil samples were collected at five-foot intervals and analytical data indicated that the soil was impacted with petroleum hydrocarbons mainly between 20 feet and 60 feet bgs The three soil borings were completed as groundwater monitoring wells and the wells were developed Groundwater samples from the wells contained elevated concentrations of petroleum hydrocarbon constituents The on-site domestic well was also sampled and benzene, toluene, ethyl benzene, and xylenes (BTEX) constituents were detected Benzene concentrations in the three monitoring wells and the on-site supply well exceeded the State of California ' Maximum Contaminant Level (MCL) Site activities were summarized in ATC's Summary Report of Subsurface Investigation, January 15, 1999 ' In December 2000, ATC supervised the advancement of one cone penetrometer (CPT) boring to 145 bgs, four hollow stem auger borings to 80 feet bgs, and one hollow stem auger boring to 100 feet bgs The five hollow stem auger borings were completed as groundwater monitoring wells and the wells were developed Groundwater samples from the wells MW4, MW6, MW7, and MW8 contained elevated concentrations of petroleum hydrocarbon constituents Site activities were summarized in ATC's Summary Report of Additional Subsurface Investigation, March 6, 2001 2.0 SUBSURFACE INVESTIGATION METHODS AND PROCEDURES To evaluate if soil vapor extraction and/or air sparge are viable remedial options for remediating kU j" petroleum impacted soil and groundwater, six soil borings were advanced in the vicinity of the former USTs and converted to wells used for pilot testing To evaluate the lateral extent of impacted groundwater, four Geoprobe soil borings and two hollow stem auger borings were advanced at the site All field activities were performed in accordance with ATC's Workplan for 4;j_6;f'" Vapor Extraction and Aar Sparge and Pilot Testing at Pacific Coast Recreation, 3755 Munford Avenue, Stockton, California, dated June 27, 2001 This workplan was approved by SJCEHD on July 16, 2001 2.1 Drilling Activities 2.1.1 Geoprobe® Drilling Activities On August 27 and 28, 2001, ATC personnel supervised advancement of four soil borings, SBI through S134 to first encountered groundwater, approximately 61 feet bgs The soil borings were advanced at the locations shown on Figure 2 to evaluate the horizontal extent of petroleum hydrocarbon impacted soil and groundwater Fisch Environmental, California License C57 683865, advanced the borings using a truck mounted Geoprobe® narrow diameter rig employing direct push technology Soil samples were collected from borings SBI through S134 at approximate ten-foot intervals in acetate sampling tubes and were described according to the Unified Soil Classification System Descriptions of w 1163931repons%rjfs doc 2 r r - -