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CRO Ms Margaret Lagono • May 8, 1995 (93479013) In September 1989, Aegis Environmental Consultants (Aegis) of Roseville, California, performed a pre-tank replacement site assessment at the subject site A total of fifteen soil borings (B-1 through B-15) were advanced on site to depths ranging from 11 5 to 21 5 feet below grade, at the locations identified on Figure 2 The soil sample collected from boring B-8 at 10 feet below grade (bg) contained concentrations of total petroleum hydrocarbons (TPH) as gasoline and benzene of 1,060 and 1 81 parts-per-million (ppm), respectively Complete assessment results were documented in Aegis' "Pre-Tank Site Assessment Results Report" dated October 16, 1989 On October 3 and 4, 1990, Aegis installed 4-inch-diameter groundwater monitoring wells MWA through MW-3 to depths of 75, 73, and 75 feet bg, respectively (Figure 2) Soil and groundwater samples analyzed from each boring contained no detectable petroleum hydrocarbon concentrations Complete investigation results were documented in Aegis' "Site Assessment Monitoring Well Installation Results Report" dated March 26, 1991 Groundwater conditions beneath the site are well documented No concentrations of petroleum hydrocarbons have been detected in any of the three monitoring wells since October 1992 The wells were monitored and sampled quarterly until 1994 In a February 8, 1994 letter, the SJCEHD agreed to an annual monitoring and sampling program The . wells are currently monitored and sampled annually in the fourth quarter Proposed Wozlk Fugro proposes to drill one 6-inch-diameter soil boring and one 10-inch-diameter soil boring on site using a hollow-stem-auger drill rig in the areas of investigation shown on Figure 2 To avoid drilling into or through potential buried obstructions, the first five feet of each boring will be augered by hand The 10-inch-diameter soil boring will be located approximately 10 feet downgradient (south) of the UST basin and will be completed as a 4-inch-diameter groundwater monitoring well The top of groundwater beneath the site is approximately 65 feet bg The well will be developed by surging and bailing until the water appears relatively clear The well will be purged and sampled no sooner than 24 hours after development The 6-inch-diameter boring will be drilled adjacent to boring B-8 (Figure 2) The soil boring will be drilled to a minimum of 20 feet bg Soil samples will be collected in each boring at 5 foot intervals, and significant changes in lithology The soil samples will be described according to Fugro's standard operating procedures (SOP) included in Attachment 1, and screened in the field using a portable organic vapor monitor (OVM) The 6-inch-diameter boring will be terminated when field screening using an OVM indicates the absence of hydrocarbons for ten consecutive feet in the unsaturated zone A minimum of three soil samples collected from the 6-inch-diameter soil boring will be submitted for chemical analysis • 93479013 AWP 2