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7-Eleven Store #19976 Quarterly Groundwater Monitoring and Remediation Progress Report (2Q2006) August 8, 2006 Page 6 80% of the original levels prior to collection of the water sample Groundwater samples were collected using a disposable Teflon® bailer, placed into appropriate EPA-approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a California state-certified laboratory Copies of the field notes are presented in Attachment A r GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from MW-1, MW-1A, MW-2, MW-3, MW4A, MW-5, MW-5A, MW-6 and MW-7 were analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, tert-butyl alcohol (TBA), dnsopropyl ether (D1PE), ethyl-tert-butyl ether (EtBE), and tert- amyl-methyl ether (TAME) by Environmental Protection Agency (EPA) Method 82608 The certified laboratory analytical report and chain-of-custody (COC) documentation are presented as Attachment B Groundwater analytical results are presented on Figure 3, and are summarized in Tables 1 and 2 Due to cross-contamination of samples collected on April 18, 2006, all wells were re-sampled on May 12, 2006 MtBE concentrations continued to decrease during the second quarter 2006 in down-gradient wells MW-5 and MW-7 REMEDIATION • Remediation conducted during the second quarter 2006 was oxygen injection into SP-1 and SP-1A On April 12, April 27, May 11, May 22, June 8, and June 22, 2006, SECOR field personnel / conducted oxygen injection into on-site sparge wells SP-1 and SPAA Approximately 150 ft3 of oxygen was injected into each well simultaneously (Table 4) J Dissolved oxygen concentrations were measured before and after the injection event in monitoring well MW-2 (Table 5) The greatest D O concentration increase observed to MW-2, located adjacent to SP-1 and SP-1A, was from 20 2 milligrams per liter (mg/L) to 46 1 mg/L on May 22, 2006 SECOR will continue biweekly to monthly oxygen injection during the third quarter 2006 Copies of the field notes and laboratory analysis are presented in Attachment C r PURGE AND RINSATE WATER DISPOSAL Water generated during well sampling and equipment cleaning is pumped into a SECOR truck-mounted water tank The water is transferred into properly labeled 55-gallon drums and stored on-site The drummed non-hazardous petroleum hydrocarbon contaminated water is transported quarterly by Belshire Environmental to DeMenno Kerdoon in Compton, California, for disposal • 19976 46-2Q Report doc SECOR International Incorporated