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S E C 0 R 7-Eleven Store#19976 Quarterly Groundwater Monitoring and Remediation Progress Report (4Q2005) February 9, 2006 Page 6 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 GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from MW-1 through MW-3, MW-5, MW-6, MW-1A, MW- 4A, and MW-5A were analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, tert-butyl alcohol (TBA), diisopropyl ether (DIPE), ethyl-tent-butyl ether (EtBE), and tert-amyl-methyl ether (TAME) by Environmental Protection Agency (EPA) Method 8260B 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 Hydrocarbon concentrations continued to decrease in well MW-2 located immediately adjacent to and downgradient of the USTs and dispensers 0 The concentrations of BTEX and MtBE reported in water samples collected from A) and,MW- are anomalous when compared with the historical analytical data (Table 2) ,ti REMEDIATION , Remediation conducted during the fourth quarter 2005 was oxygen injection into SP-1 and SP-1A � f On October 10, October 27, November 9, November 23, and December 8, 2005, SECOR field personnel conducted oxygen injection into on-site sparge wells SP-1 and SP-1A 150 ft3 of oxygen was injected into each well simultaneously (Table 4) 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 in MW-2, located adjacent to SP-1 and SP-1A, was from 11 1 milligrams per liter (mg/L) to 37 4 mg/L on October 27 2005 SECOR will continue biweekly to monthly oxygen injection during the first quarter 2006 Copies of the field notes and laboratory analysis are presented in Attachment C 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 05-40 Report doc SECOR International incorporated