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'44 S EC ® R 7-Eleven Store#32262 Quarterly Groundwater Monitoring Report (3Q2004) October 1, 2004 Page 2 Current Quarter Monitoring Data (See Figure 2 and Table 1) Wells Monitored and Sampled Ten wells- MW-1 through MW-5, MW- 6D, MW-7 through MW-9, and TP-1 Dissolved Oxygen Concentrations Measured In Ten wells- MW-1 through MW-5, MW- 6D, MW-7 through MW-9, and TP-1 Depth to Groundwater (DTW) 5 62 to 11 18 ft bgs Average Change in Groundwater Elevation Since Last Event 0 21 foot increase Groundwater Flow Direction and Gradient North northwest @ 0 009 feet per foot (Figure 2) Current Quarter Analytical Data (See Figure 3 and Table 1) Maximum Benzene Concentrations Not Detected, <0 50 to <40 IL Maximum TPHg Concentrations Not Detected, <50 to <4,000 pg/L Maximum MtBE Concentrations MW-5, 17,000 pg/L Maximum TBA Concentrations Not Detected, <5 0 to <200 pg/L BACKGROUND In 1997, Fluor Daniel GTI conducted Phase I and Phase II assessments at the site, consisting of sod borings and grab groundwater samples No detectable concentrations of petroleum hydrocarbons, polynuclear aromatic hydrocarbons, or pesticides were found on- site A Phase I addendum was submitted by IT Corporation on September 27, 1999 Under the direction of a SJCEHD representative, ten soil samples were collected on May 2 and 3, 2003, beneath the product lines (1-1 through L4 on Figure 4) and dispensers (D1 through D6) at depths between 3 5 feet and 4 5 feet below ground surface (bgs) The soil samples collected did not contain total petroleum hydrocarbons as gasoline (TPHg) or benzene, toluene, ethylbenzene, or total xylenes (BTEX) above laboratory reporting limits Maximum reported concentrations of MtBE and tert-butyl alcohol (TBA) were 4 5 milligrams per kilogram (mg/kg) and 12 mg/kg, respectively (D1-4 0') Due to the presence of petroleum hydrocarbons and fuel oxygenates in soil and groundwater beneath the site, SECOR submitted an Underground Storage Tank Unauthorized Release with the (Leak)/Contamination Site Report to the SJCEHD and the Central Valley Regional Water Quality Control Board During fuel line and dispenser upgrade activities on May 3, 2003, SECOR personnel collected grab water samples (W1 and W2) from two tank pit observation wells (TP-1 and TP-2) Depths to bottom of wells TP-1 and TP-2 were measured between 11 feet and 12 feet bgs MtBE, TBA, and tert-amyl methyl ether (TAME) were reported at concentrations up to 510,000 micrograms per liter (pg/L), 79,000 ug/L, and 1,500 ug/L, respectively • During UST excavation dewatering activities, approximately 199,090 gallons of impacted water and a calculated estimate of 243 8 pounds of MtBE were removed from the tank pit 32262 04-3Q Report cloc SECOR lntematronal Incorporated s