SITE INFORMATION AND CORRESPONDENCE FILE 2

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j • Steve & Gene's Service`' �"� Page 3 2315 N. EI Dorado Street 07 March 2008 Stockton, CA proposed wells screened from 65 to 75 feet bsg near CPT-1 and CPT-3, but does not consider this to adequately delineate impacted groundwater in the major sand at this time. The EHD recommends that additional wells be installed in this interval near MW-6, MW-5, and VEW-1, on the north corner of E. Castle Street and N. EI Dorado Street, and on the south corner of E. Hampton Street and N. EI Dorado Street. Submit a work plan addendum and/or a report addressing these recommendations to the EHD by 15 April 2008. The Shell site at 2320 N. EL Dorado Street is also being investigated, and there is a potential that the plumes from the two sites are commingled; data from the recommended wells may be useful to resolve the commingling issue. The sand between 90 and 100 feet bsg was encountered in several onsite borings, but the offsite CPT borings did not penetrate to that depth, therefore there is no indication that either the thin sand or contaminants occur in the 90- to 100-foot depth interval. The onsite monitoring wells MW-101 (screened 92 to 97 feet bsg) appears to have `cleaned up" over time and contaminants in MW-201 (screened approximately 149 to 151.5 feet bsg) have rarely been detected. As MW-101 is in close proximity to MW-3, SB-B and the former dispensers, and no contaminants of concern have been detected in groundwater samples from the well during the four quarters of 2007, the EHD considers the vertical extent of impacted groundwater to be delineated at this time; should groundwater in MW-101 become significantly impacted again in the future, this conclusion may be reevaluated. At this time the EHD no longer considers additional wells screened in these deeper intervals to be required and therefore does not approve the proposed deep wells screened between 89 and 100 feet bsg. The EHD notes that the wells were proposed in response to the previous EHD directive. The EHD approves the proposed analysis for TPH-g and BTEX, but directs that the analytical suite include the fuel oxygenates and lead scavengers methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), tert-butyl alcohol (TBA) 1,2-dichloroethane (1,2-DCA) and ethylene dibromide (EDB). Please direct questions and comments to Frank Girardi, Senior Registered Environmental Health Specialist at (209) 953-7868. Sincerely, �� Nuel C. Henderson, Jr., PG Margaret agorio, REHS Engineering Geologist Program Coordinator NCH:nch c: James Barton —CVRWQCB,11020 Sun Center Dr. #200, Rancho Cordova, CA 95670 Ray Kablanow, PG —Geological Technics Inc., 1101 Seventh St., Modesto, CA 95354 WP Comment Letter 0308