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' S E C 0 R Second Quarter 2004, Quarterly Progress Report July 13, 2004 ' Page 2 3 0 EVALUATION OF GROUNDWATER EXTRACTION ' GWET and Sod Vapor Extraction (SVE) systems were activated on July 3, 2000 Certified laboratory analytical reports and chain-of-custody documentation and remedial system operation and maintenance ' field data sheets are included in Appendices D and E, respectively On August 20, 2003, SVE was discontinued as approved by the Regional Water Quality Control Board (RWQCB) in their letter dated August 18, 2003 A copy of this letter is included in Appendix F A brief description and performance evaluation of the GWET remedial system during 2Q04 are presented below s 31 Groundwater Extraction System i ' The GWET system includes groundwater extraction wells EX-1, EX-2 and EX-3 (Figure 5) These wells are equipped with submersible pumps connected through mechanical piping to a series of granular activated carbon (GAC) vessels prior to an industrial sewer discharge point Chevron discharges treated groundwater at the subject site under City of Lodi (City)wastewater discharge permit#328 To assess effectiveness of the GWET system, process samples were collected monthly during this ' reporting period Sample locations include a influent port (INFL) prior to the first GAC vessel, between the first and second GAC vessels (MID-1), between the second and third GAC vessels (MID-2), and before discharge (EFFL) to the industrial sewer During these sampling events, INFL, MID-1, MID-2 and EFFL samples were analyzed for TPHg, BTEX, MtBE, TBA, DIPE, EtBE, TAME, ethanol, methanol, EDB and 1,2-DCA Maximum concentrations of detected constituents are presented below Current and historical analytical information is presented as Table 3 ' Maximum Constituent Concentrations(pgh) Zone ' MtBE TBA EtBE TAME Ethanol Methanol INFL 9 <10 <2 <2 <100 <400 ' MID-1 <2 <10 <2 <2 <100 <400 MID-2 <2 <10 <2 <2 <100 <400 EFFL <2 <10 <2 <2 <100 <400 Exglanatio_ns <Indicates the constituent was not present at or above the method detection limit shown tBetween December 12, 2003 and March 09, 2004, the GWET system discharged a total of 765,216 gallons of treated groundwater (Table 4) As of March 09, 2004, the GWET system had treated a total of 9,428,621 gallons Calculated discharge rates during the 2Q04 monitoring period ranged from 5 58 to ' 6 77 gallons per minute (gpm) uring ZUU4, trie system extracted an estimated U 2 pounds of I PHg I o date, the system ah s extr`acT6d approximately 9 7 pounds of TPHg, 0 2 pound of benzene, and 85 0 pounds of MtBE Plots of GWET system mass removal trends and influent groundwater TPHg, benzene, and MtBE concentrations versus time are shown on Figure 6 and 7, respectively ' 11Chevron1957751Penodic Monitonng\Q P R=0412nd Quarter-2004 QPR doc