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S E C O R Work Plan for Soil Vapor Survey August 9, 2007 ARCO Service Station No. 2186 Page 3 of 8 borings (CPT-2 and CPT-3) on the eastern edge of the site and one CPT boring north of the site (CPT-1). Benzene and MTBE was detected in groundwater samples from CPT-2. No petroleum hydrocarbon compounds were detected in the groundwater samples collected from CPT-1 or CPT-3. None of the soil samples contained detectable concentrations of GRO and BTEX above their respective MRL's. MTBE was reported in samples collected from CPT-2 at 35 and 55 feet bgs. The vertical extent of MTBE impacts was defined. No other oxygenates were reported. HydroPunch groundwater samples were collected from CPT-1 and CPT=3 at 80 feet bgs and from CPT-2 at 55 feet bgs and 80 feet bgs. GRO was not detected in the groundwater samples collected. Benzene was detected in CPT-2 at 55 feet bgs at 0.64 micro grams per liter (pg/L). The benzene concentration was below laboratory detection limits of 1.0 pg/L and vertical extent was defined. MTBE was detected in CPT-2 at 55 and 80 feet bgs at 412 and 27 pg/L, respectively. (1T, 1999) In September 2000 Delta Environmental Consultants (Delta) of Rancho Cordova, California, conducted a SVE test. Three separate four hour tests were conducted. Soil vapors were extracted from wells VW-1A, VW-2A, and VW-3A. The tests indicated that extraction of soil vapors from these wells at nine to 10 cubic feet per minute (cf/m), with 50 to 100 inches of water column, resulted in a radius of influence between 34 and 45 feet. The initial hydrocarbon mass extraction rates were calculated to be between 1.10 and 3.88 pounds of GRO per day. In August 2001 Delta installed three groundwater monitoring wells (MW-5, MW-6, and MW-7). MW-5 is east of the site on American Street. MW-6 and MW-7 are in Oak Park, across Alpine Avenue, to the northwest and northeast of the site. Xylenes were detected in soil samples collected from boring MW-7 at 41 feet (0.026 mg/kg) and 81 feet bgs (0.025 mg/kg), other fuel oxygenates or other petroleum hydrocarbons were not detected in soil samples from boring MW-7. No petroleum hydrocarbons or fuel oxygenates were detected in soil samples collected from borings MW-5 or MW-6. Petroleum hydrocarbons or fuel oxygenates were not detected in groundwater samples collected from wells MW-5 throglgh MW-7. On April 13 through April 16 and April 19 and 20, 2004�Gregg Drilling, of Martinez, California, drilled four soil borings (BH-1 through BH-4) and installed one 2-inch diameter groundwater monitoring well (MW-8) in the dominant downgradient direction from the UST cavity (east- northeast) to assess the vertical extent of petroleum hydrocarbon impacted groundwater beneath the site. One vapor extraction well (VW-4) was installed to complete the remedial well network at the site. One air sparge well (AW-1) was installed for use in conjunction with the Vapor wells in the soil vapor extraction pilot test. GRO was detected in one soil sample, at a concentration of 0.73 mg/kg, at 50 feet bgs in AW-1 7--BTEX compounds were not reported at or above laboratory detection limits in any�soil samples analyzed from the soil borings. MTBE was detected in samples from 50 feet bgs in AW-1—and BH-3 at 0.86 mg/kg and 0.63 mg/kg, respectively. Tert-amyl methyl ether (TAME) also was detected in the samples from 50 feet bgs in AW-1 and BH-3, at concentrations of 0.013 mg/kg and 0.0081 mg/kg, respectively.–fert-butyl alcohol (TBA) also was detected at concentrations of 0.26 and 0.18 mg/kg In samples collected from 50 feet bgs in BH-2 (AW-1) and BH-3./MTBE was reported in groundwater samples from MW-8 and AW-1 at concentrations of 2.3 pg/L and 150 pg/L respectively. All other analytes were reported at or below laboratory detection limits for the groundwater sample collected from MW-8. The water sample from well AW-1 was reported to have detectible concentrations of GRO, benzene, and total xylenes, at concentrations of 97 pg/L, 6.3 pg/L, and 8.0 pg/L, respectively. 2186 SVI 8-07.doc SECOR International Incorporated