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�-- -1 Third Quarter 1993 Status Report September 17, 1993 Golden Grain Company, Manteca Bean Facility, 229 Moffat Blvd , Manteca CA 2 MW-10 was not accessible on August 12, 1993, and was subsequently monitored on August 18, 1993, during the following weekly site visit The water table elevations for August 12, 1993, were used to prepare a potentiometnc surface map for the site (Figure 1) Data collected from MW-2 and MW-3 were not used to prepare the potentiometnc surface map because of anomalous data This may be partially due to the difference in the screened interval of these wells and the associated geology The potentiometnc surface elevations in the site groundwater monitoring wells decreased an average of 2 28 feet since the last monitoring event conducted on May 14, 1993 The groundwater movement beneath the site is generally in a northerly direction at an average gradient of 0021 ft/ft The gradient at the southern portion of the site is substantially greater and exhibits the effects of the groundwater extraction well on the site groundwater GROUNDWATER SAMPLING Groundwater samples were collected from 7 of the 14 monitoring wells on site according to the LUFT guidelines Monitoring wells MW-1, MW-2, MW-3, MW-5, and MW-6 did not contain adequate groundwater to obtain samples, well MW-4 contained a 0 03400t-thick layer of free-phase petroleum, and well MW-10 was not accessible on August 12, 1993 Field data sheets from monitoring well l� 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 xylene (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 manifest for the water samples collected on August 12, 1993, are included in Attachment 4 Maps showing reported values of dissolved TPH-G and benzene concentrations are included as Figures 2 and 3, respectively Of the seven monitoring wells sampled in August 1993, dissolved TPH-G was detected only in the sample from well MW-7 Detectable dissolved hydrocarbon concentrations were higher than concentrations detected during the previous sampling event (Second Quarter 1993), but were comparable to the concentrations detected during the First Quarter 1993 TREATMENT SYSTEM OPERATION AND MAINTENANCE On June 28, 1993, the sod and groundwater remediation system was repaired and restarted for the remainder of the quarter Samples were collected from the groundwater treatment system on August 18, 1993, and analyzed for TPH-G, BTEX, total lead, organic lead, and ethylene dibromide at a state-certrfled laboratory Laboratory analysis reports and corresponding chain-of-custody records 38798013 070 ❑ GROUNDWATER TECHNOLOGY, INC