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Fourth Quarter 1993 Status Report January 6, 1994 Golden Grain Company, Manteca Bean Facility, 229 Moffat Blvd , Manteca CA 2 The water table elevations recorded on November 11, 1993, were used to prepare a potentiometric surface map for the site (Figure 1) Data collected from MWA and MW-8 were not used to prepare the potentiometric surface map because the wellheads on the wells had been damaged or altered and well elevations were uncertain New wellheads and street boxes will be installed, d necessary, on these wells and they will be resurveyed before the next quarterly monitoring event The potentiometric surface elevations in the site groundwater monitoring wells increased an average of 1 72 feet since the last monitoring event conducted on August 12, 1993 The groundwater movement beneath the site is generally in a northerly direction at an average gradient of 0 003 ft/ft The gradient at the southern portion of the site is greater and exhibits the effects of the groundwater extraction well on the site groundwater GROUNDWATER SAMPLING Groundwater samples were collected from 13 of the 14 monitoring wells on site according to the Leaking Underground Fuel Tanks (LUFf) guidelines Monitoring well MW-3 did not contain adequate groundwater 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 record for the water samples collected on November 11, 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 13 monitoring wells sampled in November 1993, dissolved TPH-G was detected in wells MW-1, MW-2, MW-4, MW-5, and MW-7 The dissolved total hydrocarbon concentrations detected in groundwater samples from these wells were lower than concentrations from the previous sampling event on August 12, 1993 Benzene concentrations detected in samples from these wells were also lower than concentrations detected In the previous sampling event Concentrations of benzene less than 1 part per billion (ppb) were also detected In groundwater samples collected from wells MW-10, MW-13, and MW-14 (fable 2) Reportable TPH-G concentrations were not detected in samples from those wells TREATMENT SYSTEM OPERATION AND MAINTENANCE During this quarter, the sod and groundwater treatment system was operational for 45 days Over the quarter, 14 site visits were made to perform system operation and maintenance work Work performed during each maintenance event included 3879RO23 070 GROUNDWATER II II N TECHNOLOGY, INC