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I) � Third Quarter 1994 Status Report 2 Golden Gram Company, Manteca Bean Facility, 229 Moffat Blvd , Manteca, CA September 26, 1994 The water table elevations recorded on August 19, 1994, were used to prepare a potentiometric surface map for the site (figure 2) The potentiometric surface elevations measured in the site groundwater monitoring wells decreased an average of 1 61 feet since the May 20, 1994, monitoring event The groundwater movement beneath the site flows generally to the north at an average gradient of 0 0017 foot per foot (ft/ft) The gradient at the southern portion of the site is greater and exhibits the effects of pumping from the groundwater extraction well on the site groundwater GROUNDWATER SAMPLING Groundwater samples were collected from 9 of the 14 monitoring wells on site in accordance with the LUFf guidelines Monitoring wells MW-1, MW-2, MW-3, and MW-5 did not contain adequate groundwater to obtain samples Monitoring well MW-9 was not sampled because the subsurface casing in the well is bent and the peristaltic pump normally used to sample the well is inoperable Field data sheets from monitoring well gauging and sampling work are 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 19, 1994, 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 9 monitoring wells sampled in August 1994, dissolved TPH-g was detected in wells MW-4 and MW-7 The dissolved TPH-g concentrations detected in groundwater samples from these wells were within the same range reported in the previous sampling event on May 20, 1994 Benzene concentrations were also detected in samples from wells MW-4 and MW-7 in the same range reported in the previous sampling event, although the concentration in MW-7 was slightly higher this quarter The TPH-g and benzene concentrations of samples taken from wells MW-10, MW-13, and MW-14 were all below detection limits for the August 19, 1994 sampling event During the previous three quarters, low levels of TPH-g and benzene were detected in these wells The concentrations from the previous three quarters caused concern because the wells are upgradient and/or cross gradient from the original source area for hydrocarbon concentrations at the site This quarter, a hand bailing technique was used to purge the wells and the wells were sampled using a disposal bailer Purging of these wells was completed with a pump each of the last three quarters It is surmised that a small amount of water containing hydrocarbons may have remained with the purging pump • 0102RO14 202 GRoUNDWATER EEITECHNOLOC,Y, INC