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4 Ms Lori Duncan August 14, 2001 Page 2 of 3 Prior to sampling, monitoring wells MW 1 through MW4 were purged of a minimum of three well casing volumes The physical parameters of temperature, pH and electrical conductivity were measured during the purging process Groundwater samples were collected after the physical parameters had stabilized and water Ievels recovered to their pre-purged levels The samples were placed into an ice chest cooled to approximately 4° centigrade and transported to Argon Laboratories (FLAP#2359)under chain of custody protocol Well purge logs are included in Attachment A WASTE DISPOSAL Groundwater purged from the site wells was contained in appropriately labeled DOT-approved 55- gallon drums and stored at the site Approximately 200 gallons of purgewater was removed from the site on July 11, 2001 and transported by American Valley Waste Oil, Delhi, CA (EPA Id # CAL 000827878)to Seaport Environmental, Redwood City, CA(EPA Id#CAL 0000325058) for disposal GROUNDWATER ANALYTICAL RESULTS Groundwater samples were analyzed for the presence of TPHg, BTEX, and oxygenated gasoline additives (including the lead scavengers 1,2-DCA and EDB) using EPA methods 8015K 8020, and 8260, respectively • No TPHg or BTEX was detected in either well MW3 or well MW4 TPHg was detected in wells MW1 and MW2 at concentrations of 1,200 parts per billion (ppb) and 490 ppb, respectively Benzene was detected in wells MW1 and MW2 at concentrations of 4 8 ppb and 0 8 ppb, respectively Ethylbenzene was detected in wells MW 1 and MW2 at concentrations of 13 ppb and 5 0 ppb, respectively Toluene was detected only in well MW 1, at 1 1 ppb No xylenes were detected 1n any site well Methyl tert butyl ether (MTBE) was detected in wells MW 1 and MW4 at concentrations of 17 and 4 7 ppb, respectively No MTBE was detected in well MW2 or well MW3 No other oxygenated gasoline additives or lead scavengers were detected in any site well Analytical results are summarized in Table 2 Attachment B contains laboratory reports and chain of custody documentation SUMMARY Groundwater levels beneath the site rose slightly, and the direction of groundwater flow shifted more to the northeast since last monitored in January 2001 Concentrations of gasoline constituents in wells MW I and MW2 increased slightly since they were last sampled in January 2001 The detected levels of benzene (4 7 ppb) and MTBE (17 ppb) in well MWl exceeded the Maximum Contaminant Levels (MCLs) of 10 ppb and 13 ppb, respectively RECOMMENDATIONS Based upon the groundwater data collected to date, Ground Zero recommends continued groundwater monitoring and sampling at the site to monitor changes in groundwater flow and contaminant G 1Data1GROL7NDZE1Tuff$oylReports\QMR12QM2001 doe