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WTo KLEINFELDER 8) Concentration contours of contaminants found and those remaining in soil and groundwater, and both on-site and off-sate Concentration contours were not prepared due to the limited dataset. Lateral and Vertical extent of soil contamination Based on analytical results from investigations performed in the vicinity of the former UST, soil impact appears to be limited • On March 25,1999,four Geoprobe borings(SB- 1 through SB4)were advanced to 25 feet bgs on both sides and ends of the UST. MTBE was detected in soil samples collected from 24.5 to 25 feet bgs at concentrations ranging from 0 004 mg/kg to 0.093 mg/kg TPH gasoline and BTEX were not detected above laboratory reporting limits in the soil samples. • Analytical results from May 2000 UST excavation confirmation soil samples indicated that petroleum hydrocarbons were not detected above laboratory reporting limits • On.lune 22,2000 three borings(MW-1 through MW-3)were advanced around the perimeter of the former UST at a distance of approximately 10 feet and to a depth of 15 feet bgs. Soil samples from a depth of 6 feet bgs from each boring were submitted for analyses TPH gasoline (1.1 mg/kg),xylenes (0.088 mg/kg) and MTBE (0.25 mg/kg) were detected in the sample from MW-1, and MTBE (0.017 mg/kg) was detected in the sample from MW-2. • On April 1,2004 a boring(MW-4)was advanced approximately 25 feet north- northwest(downgradient)of the former UST and to a depth of 35 feet bgs. Soil samples from depths of 25 5,30.5,and 36 feet bgs were submitted for analyses. TPH gasoline, VOCs, and the five fuel oxygenates were not detected above laboratory reporting limits in the three soil samples. In summary,the soil appeared to be impacted to a depth of approximately 25 feet bgs adjacent to the former UST and to at least 6 feet bgs at a distance of approximately 10 feet laterally from the former UST. At a distance of approximately 30 feet north-northwest(downgradient) of the former UST,the soil did not appear to be impacted to at least 36 feet bgs. Lateral and Vertical extent ofgroundwater contamination • On June 22,2000,three wells MW-1 through MW-3 were installed and screened from 5 to 15 feet bgs. On April 1,2004,well MW-4 was installed and screened from 30 to 35 feet bgs to evaluate potential vertical migration of petroleum hydrocarbons. MW-4 was installed in a deeper groundwater zone than the j previously installed wells. • Seven groundwater monitoring events have been performed between June 2000 and January 2005 During the first monitoring event (June 2000), the highest petroleum hydrocarbon concentrations were detected in downgradient well MW-1 [see groundwater results summary table included in attachments for number 7)]. In October 2000, approximately five months after removing the UST, petroleum hydrocarbon concentrations in the groundwater significantly decreased, most significantly in downgradient well MW-1. After two 49014-1/SAC5R423 Page 8 of 17 June 30,2005 Copyrtght 2005 Klemfelder,Inc