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Manteca Bean Facility, 229 Moffat Boulevard, Manteca, California June 22, 1992 <br /> Golden Grain Company Page 2 <br /> Monitoring Well Sampling <br /> Following well gauging, groundwater samples were collected from eight monitoring wells in <br /> accordance with the LUFT guidelines The samples were submitted under a chain-of-custody <br /> manifest to Sequoia Analytical Laboratories in Sacramento, California Each sample was <br /> analyzed for benzene, toluene, ethylbenzene and xylenes (BTEX), and total petroleum <br /> hydrocarbons-as-gasoline (TPH-G) by Environmental Protection Agency (EPA) methods <br /> 50301801518020 Historical and recent analytical data are summarized in Table 2 The <br /> laboratory analyses reports, and the chain-of-custody manifest for the May 21, 1992, samples <br /> are included in Attachment I Maps of dissolved TPH-G and benzene concentrations are <br /> included as Figures 3 and 4, respectively <br /> Discussion <br /> The potentiometnc surface elevations in the site-related groundwater monitoring wells <br /> decreased in 14 of the wells an average of 1 46 feet since the last monitoring event conducted <br /> on February 21, 1992 MW-3 was dry Groundwater beneath the site flows approximately <br /> east-northeast at an overall gradient of 0 002 The gradient at the southern end of the site is <br /> relatively steep compared to the nearly flat gradient in the central and northern portion of the <br /> site A sheen (<0 01 ft) of separate-phase petroleum hydrocarbons was noted in MW-4 <br /> Of the eight monitoring wells sampled in May 1992, dissolved TPH-G was found only in <br /> samples MW-2 and MW-7 at concentrations of 260,000 and 27,000 parts per billion (ppb), <br /> respectively Benzene concentrations in these two wells were 22,000 and 3,700 ppb, <br /> respectively These levels are consistent with those observed last quarter Trace <br /> concentrations of toluene and xylenes are detected in MW-12 <br /> Please contact Groundwater Technology's West Sacramento office if you have any questions or <br /> comments regarding this report <br /> Sincerely, <br /> Groundwater Technology, Inc Groundwater Technology, Inc <br /> Written/Submitted by Reviewed/Approved by <br /> SCOTT E GABLE, R E A ,<< {c U) �`,k' y,SIMONIS, R G <br /> Environmental Geologist "v� "'Senio Environmental Geologist <br /> Project Manager <br /> � cn <br /> SEGIEKS rc No 4422 G <br /> Attachments ,1- <br /> GROUNDWATER <br /> ,4660292 LTH TECHNOLOGY <br /> rt <br /> f r a,tit <br />