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Second Quarter 1995 Status Report 2 . Golden Grain Company, Manteca Bean Facility,229 Moffat Blvd, Manteca,CA June 20, 1995 The water table elevations recorded on May 9, 1995, were used to prepare a potentiometric 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 0 07 feet since the February 16, 1995, monitoring event The groundwater movement beneath the site flows generally to the north at an average gradient of 0 001 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 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 May 9, 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 May 1995, dissolved TPH-g and benzene was detected in wells MW-1, MW-2, MW-4, MW-5, and MW-7 The dissolved TPH-g and benzene concentrations detected in groundwater samples from MW-1 and MW-2 were higher than the results from the sampling performed on February 16, 1995 Concentrations of TPH-g and benzene detected In groundwater samples from MW-4, MW-5, and MW-7 were within the range reported in previous quarters TREATMENT SYSTEM OPERATION AND MAINTENANCE The soil treatment system currently extracts vapor phase hydrocarbons from wells MW-1, MW-2, MW-3 and MW-4 The groundwater treatment system extracts groundwater from well RW-1 During the quarter, 13 site visits were made to perform system operation and maintenance work Work performed during each maintenance event included ■ taking flame-ionization detector (FID) measurements of catalytic oxidizer vapor influent and effluent • ■ monitoring and recording the catalytic oxidizer operational data 42020102 STR ❑❑®CROUNDWATM ❑❑❑TECHNOLOGY