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Second Quarter 1993 Status Report June 15, 1993 Golden Grain Company, Manteca Bean Facility, 229 Moffat Blvd , Manteca CA 2 MONITORING WELL GAUGING Before well purging and water sample collection on May 14, 1993, Groundwater Technology personnel gauged each of the 15 site wells to measure the depth to water and the depth to separate-phase petroleum (SP), if present The well gauging was conducted in accordance with the Leaking Underground Fuel Tank Field Manual (LUFT) published by the State of California Leaking Underground Fuel Tank Task Force dated October 1989 Groundwater monitoring wells MW-2 and MW-4 exhibited a hydrocarbon sheen during monitoring and gauging procedures Groundwater monitoring data are summarized in Attachment 2, Table 1 The water table elevations for May 14, 1993, were used to prepare a patentiometric surface map for the site (Attachment 1, Figure 1) The potentiometnc surface elevations in the site groundwater monitoring wells decreased an average of 0 079 feet since the last monitoring event conducted on February 18, 1993 The groundwater movement beneath the site is generally in a northerly direction at an average gradient of 0 0015 ftM 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 Previous potentiometric surface maps have not shown the effects of pumping during drought conditions During the last three quarters, groundwater elevation has increased by an average of 4 02 feet across the site and has brought groundwater back into all but one site monitoring well GROUNDWATER SAMPLING Groundwater samples were collected from 12 of the 14 monitoring wells on site according to the LUFT guidelines Monitoring well MW-3 did not contain groundwater and well MW-4 did not adequately recharge to obtain samples 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 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 May 14, 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 12 monitoring wells sampled in May 1993, dissolved TPH-G was detected in wells MW-1, MW-2, MW-5, and MW-7 Detectable dissolved hydrocarbon concentrations were slightly lower than concentrations detected during the previous sampling event (First Quarter 1993) 2379801 070 i GROUNDWATER TECHNOLOGY, INC i