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,t � hY� 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 2.0 METHODS AND PROCEDURES To evaluate the extent of impacted soil and groundwater, one cone penetrometer soil boring and five hollow-stem soil borings were advanced at the site Soil samples were collected from the ' five hollow-stem soil borings every five feet and submitted for analysis The hollow-stem auger borings were subsequently completed as groundwater monitoring wells The new monitoring wells were developed and groundwater samples were collected from the new monitoring wells, the existing monitoring wells, and the on-site domestic well All field activities were performed in accordance with ATC's Workplan for Subsurface Investigation at Pacific Coast Recreation, 3755 Munford Avenue, Stockton, California, dated June 7, 1999 This workplan was approved by PHS/EHD on June 11, 1999 221 Cone Penetrometer Drilling Activities 1 Drillingwas conducted on December 4 200 0 by Gregg Drilling & Testing Inc (State C57 license no 485165) utilizing cone penetrating testing (CPT) methods A cone mounted with sensors at the tip was advanced into the soil using direct push rods at the location shown on Figure 2 The sensors on the cone tested the response of the soil to the force of the penetrating cone and allowed the subsurface stratigraphy to be characterized The cone and rods were advanced by a hydraulic press with a down pressure capacity of approximately 25 tons to 144 feet bgs utilizing a truck-mounted CPT rig A copy of the Gregg Drilling & Testing Inc Cone ' Penetration Test Data is included in Appendix A 2_2 Hollow Stem Au er Drilling Activities ' Drilling was conducted on December 5, 6, and 8, 2000 by V & W Drilling (State C57 license no 720904) utilizing a hollow stem auger drill rig Soil borings MW4, MW5, MW6, MW7, and ' MW8 were advanced and completed as groundwater monitoring wells A field geologist logged . drill cuttings and soil samples utilizing the Unified Soil Classification System Descriptions of soil types encountered and sample collection intervals are included on the well construction logs contained in Appendix B w\I 6393%reportslsumu doc 2 1