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r Third Quarter 1995 Status Report 2 Golden Grain Company, Manteca Bean Facility, 229 Moffat Blvd, Manteca, CA September 25, 1995 J in accordance with the Leaking Underground Fuel 'Tank (LUFT) Field Manual published by the State of California Leaking Underground Fuel Tank Task Force, dated October 1989 The water table elevations recorded on August 18, 1995, were used to prepare a potentiometnc surface map for the site (figure 2) The groundwater elevation from MW-3 was not used because an accurate measurement could not be collected The potentiometric surface elevations measured in the site groundwater monitoring wells decreased an average of 2 38 feet since the May 9, 1995, monitoring event The groundwater movement beneath the site flows generally to the north at an average gradient of 0 002 foot per foot (ft/ft) The gradient at the southern portion of the site is slightly greater than that for the northern portion GROUNDWATER SAMPLING Groundwater samples were collected from 13 of the 14 monitoring wells on the site in accordance with the LUFT guidelines A sample was not collected from MW-3 because adequate groundwater was not retrievable A copy of the field data sheet from monitoring well gauging and sampling work • is included in attachment 3 The samples were submitted under chain-of-custody protocol to GTEL Environmental Laboratories in Concord, California 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 5030/8015/8020 Historical and recent analytical data from groundwater analyses are summarized in table 2 The laboratory analyses reports and the chain-of-custody record for the water samples collected on August 18, 1995, are included in attachment 4 Maps showing reported values of dissolved TPH-g and benzene concentrations are included as figures 3 and 4, respectively Of the 13 monitoring wells sampled in August 1995, dissolved TPH-g and benzene were detected in wells MW-1, MW-2, MW-4, MW-5, and MW-7 The dissolved TPH-g concentrations detected in groundwater samples from MW-1, MW-5, and MW-7 were lower than the results from the previous V quarterly sampling performed on May 9, 1995 Concentrations of TPH-g detected in groundwater samples from MW-2 and MW-4 were within the range reported in the previous quarter Benzene concentrations detected in groundwater samples from MW-7 were lower than the results from the previous quarter, and the remaining monitoring wells contained benzene concentrations within the range reported in the previous quarter r 42020102 QTR ❑❑®GROUNVWATER ' ❑❑❑TECHNOLOGY