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PUBLIC HEALTH SERVICES <br /> p�l...N <br /> SAN JOAQUIN COUNTY <br /> r. <br /> ENVIRONMENTAL HEALTH DIVISION H s< <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer •' <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 RECEIVED <br /> KENNETH R EARNEST JUN 2 3 1997 <br /> ULTRAMAR INC JUN 2 0 07 <br /> PO BOX 466 <br /> 525 W THIRD ST <br /> HANFORD CA 93232 <br /> RE: Beacon Station #474 SITE CODE: 1173 <br /> 3440 E. Main St. <br /> Stockton, CA., 95205 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS- <br /> EHD), has reviewed the recently submitted Quarterly Monitoring Report for the March <br /> 27, 1997 groundwater sampling event and has the following comments. <br /> MW-2 recorded 2,800 ug/I of MTBE for this quarter. Compared to the last two quarter's <br /> that recorded MTBE at less than 500 ug/I, PHS-EHD now considers this significant <br /> change in groundwater contamination a new release and will file an "Unauthorized <br /> Release Form" and a "Notification of Hazardous Waste Discharge-H&S Code 25180.7". <br /> The groundwater gradient beneath this site has varied since their installation. For the <br /> last two quarters the flow has been recorded in the south-southeast direction. In order <br /> to accurately assess the impact to the groundwater in this direction, PHS-EHD will <br /> require an additional groundwater monitoring well to be installed in the southeast corner <br /> of the site. The screened interval for this well should be placed so that the interface <br /> between the vadose and saturated zone is adequately within this interval at the time of <br /> construction. Future changes in the depth to water may require additional wells as <br /> determined by PHS-EHD's evaluations. <br /> The depth to groundwater has been over the top of the screened interval for MW 1, 2, <br /> and 3 since June, 1995. In order to better assess the impact to the groundwater in the <br /> area of highest TPH-G and Benzene concentrations, PHS-EHD will require an <br /> additional monitoring well be placed very close to MW-2. The screened interval for this <br /> well should be installed so that there will be a two foot (2") overlap of the new well's <br /> lower screened interval with MW-2's upper screened interval. PHS-EHD recommends <br /> no more than a fifteen foot (15') screened interval in the new well. <br /> Soil samples from MW-2 and SB-1's installation indicated only low levels of petroleum <br /> contamination in soil that was reported as predominately silty clays. This data does <br /> A Division of San Joaquin County Health Care Services <br />