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' `+✓ Report for Monitor We*av(mpling and Groundwater Investigation Pilkington North America July 23,2003 Page 2 Ms. Lagorio also indicated, however, that the May 28, 2003 work plan proposed both soil and groundwater sample collection from the borings proposed for the 1997 UST removal site. Because the work plan did not propose soil sampling, Condor called Ms. Lagorio for clarification on June 12, 2003. Ms. Lagorio subsequently prepared a letter dated June 12, 2003 clarifying what the SJCEHD was requiring for the further investigation of the 1997 UST removal site. She indicated that the collection of one soil sample from each boring was necessary, in addition to one groundwater sample. She also indicated that because the soil samples needed to be collected at 12 feet below grade or below, the proposed boring in the center of the former UST location would not be required (ostensibly because the presence of a concrete slab left in place at the time of the UST removal would preclude sample collection). A scope of work for that site was developed, therefore, that included the installation of four borings around the former UST location for the purpose of collecting one soil and one groundwater sample from each boring. SITE BACKGROUND INFORMATION 1986/1987 UST Site The site background information provided in this report is based solely on documents prepared by PNA, Woodward Clyde Consultants (WCC), and the SJCEHD reviewed by Condor during a SJCEHD file review. According to WCC reports, a 550-gallon UST was removed in 1986 and a 5,000-gallon UST was removed in 1987 from a single location. Both USTs formerly contained gasoline. Soil and groundwater samples collected during the UST removals and during subsequent soil over-excavation activities indicated the presence of gasoline contamination. The soil over-excavation activities did not successfully remove all soil contamination in the source area because of site structures (loading dock). Two monitor wells (MW-17 and MW-18) were installed in the suspected down-gradient direction from the contamination source area. At least two groundwater sampling events were conducted by WCC using the two monitor wells. WCC indicated that, based on the results of the sampling, some gasoline contamination was present in groundwater at the location of the immediate down-gradient monitor well (MW-17), but the further down-gradient monitor well (MW-18) was apparently not impacted. 1997 UST Site PNA and SJCEHD documents indicate that one 5,000-gallon gasoline UST was removed from a second site location in 1997. Laboratory analysis of the four soil samples collected from the tank excavation sidewalls and the two soil samples collected from the soil removed from the excavation (soil stockpile) indicated that total petroleum hydrocarbons quantified as gasoline (TPH-G)was not detected in any of the samples at or above the laboratory reported detection limit of 1.0 milligram per kilogram (mg/kg). Benzene, toluene, ethyl benzene, and total xylenes (BTEX) were also not detected at or above the laboratory reported detection limit for these constituents of 0.005 mg/kg in any of the soil samples. MTBE was detected at a concentration of 0.006 mg/kg in the soil sample collected from the west side of the tank excavation but was not detected at or above the laboratory reported detection limit of 0.005 mg/kg in any of the other soil samples. SCOPE OF WORK CONDUCTED Monitor Well Surveying,Sampling and Laboratory Analyses On July 9, 2003, Condor marked the MW-17 and MW-18 well collars at the 1986/1987 UST removal site with a water level measuring point. The measuring point elevations were then surveyed by Condor relative to existing monitor wells W-3 and W-4 to 0.01 foot. Existing monitor wells W-3 and W-4 were previously surveyed relative to mean sea level. All monitor well collar elevations are shown in Figure 2, Attachment A. is CONDOR