ARCHIVED REPORTS_XR0002360 - Laserfiche WebLink

Home Browse Search

San Joaquin County, Local Oversight Program March 19, 2001 Page 3 Benzene was found at concentrations exceeding the maximum contaminant level(drinking water standard) in one of the monitoring wells- 3.0 :g/L in MW-4. For the sample from MW-5 the detection limit was raised to the MCL and<1.0 :g/L was reported. See Table 3 and Figure 3. The other aromatic hydrocarbon compounds;toluene, ethylbenzene, and total xylene isomers, were generally not detected,however in MW-4 groundwater ethylbenzene, was reported at 1.2 :g/L. See Table 3. MtBE was found in seven of the monitoring wells as indicated in Table 3 and Figure 3. Three of the monitoring wells (MW-4, MW-5, and MW-8)were with concentrations above the maximum contaminant Ievel(primary drinking water standard)of 13 :g/L. Five of the monitoring wells (MW-1, MW-2, MW-3, MW-6, and MW-7 were reported with below the secondary drinking water standard of 5.0 :g/L. The other U.S. EPA Method 8260B Fuel Oxygenates were not detected above their respective detection limits in groundwater samples as indicated in Table 3. Ethylene dibromide and 1,2- Dichloroethane were below their respective detection limits. 4.0 MONITORING WELLS MW-5, MW-8, AND MW-4 Monitoring wells MW-5 and MW-8 were installed in September 1995 and are about 12 feet apart. Monitoring of the MtBE concentration in the monitoring wells began in February 1999. For the first four monitoring events (2/23/99, 6127199, 8/31/99, and 213100)MtBE was not detected (<1.0 :g/L) in water from MW-5 and was consistently low in MW-8 (6.1, 2.0, 8.0, and <1.0 :g/L) that was installed as a 6-inch test/extraction well under oversight agency direction. There was a sampling hiatus during the summer of 2000. When sampling resumed in Fall 2000 MW-5 was reported with 140 :g/L on 11/19/00 followed by 81 :g/L on 2/23/01; 250 :g/L on 5/19/01; 200 :g/L on 8/18/01;210 :g/L on 11/17/01 and 290 :g/L on 2/24/02. For these same sampling events adjacent MW-8 was reported with 19, 40, 58, 54, 78,and 120 and :g/L. MW-5 and MW-8 are cross to downgradient of the west end of the fuel pump island. Conversely,MW4,contiguous with the tank excavation on the downgradient side, was first reported with 530 :g/L on 2/23199 followed by 160 :g/L on 6/27/99, 240 :g/L on 8/31/99, and <1.0 :g/L on 213/00_The more recent events have shown 91,53,32,.32, 27, and 52 :g/L. 5.0 RECOMMENDED CONTINUED MONITORING Based on communications with The Customer Company,the continuing obligations of The Customer Company for Store 437 are for events that occurred prior to 1998. For events after 1998 the obligation is to Convenience Acquisition Company operating as More for Less#37. Convenience Acquisition Company recently sold More for Less#37 to another party. H2OGEOL A GROUNDWATER CONSULTANCY