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i Ms Margaret Lagorio S E C ® R October 18, 2005 Page 4 • monitoring wells (MW-8S/IID through MW-10S/IID) consisting of three wells nested at each location SENSITIVE RECEPTORS A 1996 Department of Water Resources (DWR) survey identified 10 wells located within the survey area These wells are located northeast to southeast of the site and are apparently utilized as cathodic protection or irrigation wells MONITORING AND SAMPLING Groundwater monitoring and sampling has been performed at the site since the second quarter 1996 From 1996 to 2000, the site was monitored and sampled quarterly In 2001, the site was monitored and sampled monthly In 2002, the site was monitored and sampled b4-monthly From 2003 to the present, the site has been monitored and sampled quarterly Currently, 11 wells (MW-1 through MW-4S and D, MW-6S and D, MW-8D, and MW-10S, 1, and D) are monitored and sampled quarterly and 9 wells (MW- 5S and D, MW-7S and D, MW-8S and I, and MW-9S,I, and D) are monitored and sampled semi-annually during the first and third quarters Samples are analyzed for total petroleum hydrocarbons as gasoline (TPHg) by Environmental Protection Agency (EPA) Method 8015M, benzene, toluene, ethyl-benzene and total xylenes (BTEX), fuel oxygenates tertiary-butyl alcohol (TBA), methyl tertiary-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETRE), tertiary-amyl methyl ether (TAME), and ethanol, and lead scavengers 1,2-dichloroethane (1,2-DCA) and ethylene di-bromide (EDB) by EPA Method 82608 All wells were sampled during third quarter 2005 Results are discussed below and are summarized in TRC's Quarterly Monitoring Report July through September 2005, dated September 7, 2005, which is included in Attachment 1 DISCUSSION During the third quarter 2005, depth to groundwater ranged between 6 15 feet and 9 08 feet bgs, which is consistent with historical levels that have ranged between depths of 4 11 feet and 11 43 feet bgs The direction of groundwater flow was southwesterly at a gradient of 0 003 feet per foot (ft/ft), which is consistent with the previous groundwater flow direction reported last quarter During the third quarter 2005 monitoring and sampling event, the following maximum concentrations were reported TPHg 160 micrograms per liter (Ng/L) (MW-1) Benzene 0 14J pg/L (estimated concentration) (MW-6S) MTBE 160 pg/L (MW-1) TPHg and MTBE concentrations in groundwater continue to decline, particularly in source area wells MWA and MW-2 Ethanol was detected at estimated concentrations of 310 lag/L and 170 pg/L in the groundwater samples collected from MW-4S and MW- 5S this quarter Ethanol has not previously been detected in groundwater at these wells Besides TPHg, benzene, MtBE, and ethanol, no other requested analytes were reported • above laboratory method reporting limits in groundwater 5886 3Q2005 QSSR doe SECOR Intemational Incorporated