SITE INFORMATION AND CORRESPONDENCE_CASE 2

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• w . AEGIS ENVIRONMENTAL , INC . 1050 Melody Lane, Suite 160, Roseville, CA 95678 ♦ 916.782-2110 1916-969-2110 1 FAX 916.786-7830 December 9, 1991 RECEIVED DEC 16 1991 Ms. Margaret Lagorio ENVIRONMENTAL San Joaquin County Public Health Services ENVIRONMENTAL HEALTH I 445 North San Joaquin Boulevard PERMIT/SERVICES Stockton, California 95201 Subject: Quarterly Groundwater Monitoring Report Shell Service Station (WIC No. 204-4416-0202) 420 West Kettleman Lane, Lodi, California Dear Ms. Lagorio: Based upon the results of the previous (i.e., April and July 1991) and most recent (i.e., October 1991) laboratory analyses of groundwater samples collected from the three monitoring wells (MW-1, MW-2, and MW-3) on the subject site, Aegis Environmental, Inc. (Aegis), plans to discontinue analysis for the following constituents: • Ethylene dibromide (EDB); • 1,2-dichloroethane (EDC); and, • Total lead. Groundwater monitoring will continue to include analysis for: • Total petroleum hydrocarbons (TPH), as gasoline; and, • Purgeable priority pollutants, including benzene, toluene, ethylbenzene, and total xylenes (BTEX). In addition, Aegis plans to change the frequency of monitoring from quarterly to annually. Results of analysis of water samples collected on October 17, 1991 (Tables 1 and 2), indicate for all three wells: total lead concentrations are consistently below 0.002 parts- per-million (ppm); EDB concentrations are consistently below the 0.01 ppm detection limit; and EDC concentrations are consistently below the 0.0028 ppm detection limit. The ' analytical results over the past four quarters indicate the hydrocarbon constituents indicated above have stabilized below the respective laboratory detection limits. 89-0130.LTR GEOLOGISTS 9 ENGINEERS • GROUND WATER SCIENTISTS