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Third Quarter 1996 Status Report 2 Golden Gram Cornmy,Manteca Bean Facildy,229 Moffat Boulevard Manteca California ember 17 19% ' The depth to water measurements recorded on August 5, 1996,were used to calculate the groundwater elevations for preparation of a potentiometnc surface map for the site (figure 2) The ' potentiometnc surface elevations measured on August 5, 1996, showed an average decrease of approximately 1 7 feet since the May 21, 1996, monitoring event The groundwater gradient ' direction beneath the site is generally to the north at an average gradient of 0 0001 foot per foot The general gradient at the southern portion of the site is greater than that of the northern portion GROUNDWATER SAMPLING ' Groundwater samples were collected from 13 of the 14 monitoring wells on site in accordance with the LUFT guidelines Monitoring well MW-3 did not recharge and therefore was not sampled ' A copy of the field data sheet for monitoring well gauging and sampling work is included in attachment 3 The samples were submitted under chain-of-custody protocol to American ' Environmental Network in Pleasant Hill, California, for chemical analyses The samples were analyzed for benzene,toluene, ethylbenzene, and total xylenes(BTEX), and for total petroleum hydrocarbons as gasoline (TPH-g) using Environmental Protection Agency (EPA) Methods 5030/801518020 Groundwater samples were also analyzed for total lead, organic lead, and ethylene dibromide (EDB) Historic and recent groundwater analytical data are summarized in ' table 2 The laboratory analytical reports and the chain-of-custody record for the water samples collected on August 5, 1996, are included in attachment 4 Maps showing reported values of dissolved TPH-g and benzene concentrations are included in attachment 1 as figures 3 and 4, ' respectively ' Of the 13 monitoring wells sampled in August 1996, dissolved concentrations of TPH-g and benzene were detected in wells MW-2, MW-4, MW-5, and MW-7 Concentrations of TPH-g only were detected in well MWA The dissolved TPH-g concentrations detected in groundwater samples from ' MW-4 were the same as reported last quarter Concentrations detected in wells MW 1, MW-5, and MW-7 were lower than the results reported for the previous quarterly sampling performed on May 21, ' 1996, but within historic ranges Concentrations of TPH-g detected in groundwater samples from MW-2 were higher than the results reported in the previous quarter Concentrations of benzene detected in groundwater samples collected from MW-4, MW-5 and MW-7 were lower than the results ' of the previous quarter, but within historic ranges Concentrations of dissolved benzene in the sample collected from MW-2 were detected slightly higher than last quarter ' 20200213 QS3 FL41®1,1; ®tl1N9EL GTI