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PUBLIC HEALTH SERVICES `oP Boz <br /> SAN JOAQUIN COUNTY <: <br /> N: y < <br /> JOGI KHANNA M.D,M.P.H 4 <br /> Health Officer <br /> r <br /> P.O. Box 2009 0 (1601 East Hazelton Avenue) 0 Stockton, California 95201 . <br /> (209) 4683400 <br /> CHUCK NICHOLS �`` J <br /> USA PETROLEUM <br /> PO BOX 1839 JAN 0 4 199` <br /> SANTA MONICA CA 90406 <br /> RE: USA Petroleum #110 SITE CODE: 1669 <br /> 2132 Mariposa Road <br /> Stockton, Ca <br /> San Joaquin County Public Health Services, Environmental Health <br /> Division (PHS/EHD) has completed the review of the "Additional <br /> Site Characterization of Soil and Groundwater" Report dated <br /> December 10, 1992 , submitted by Park Environmental Corporation, <br /> and has the following comments. <br /> The three replacement wells that were installed in this last <br /> phase of field work provide additional data on the soil and <br /> groundwater contaminant plumes. As discussed in the report, the <br /> full extent of these plumes has not yet been determined. <br /> Additional soil borings/monitoring wells shall be installed as <br /> needed until the full extent of the soil and groundwater <br /> contaminant plumes are identified. In addition, a monitoring <br /> well shall be installed in each downgradient flow direction <br /> identified for this site. <br /> Please submit a workplan to investigate the full extent of the <br /> soil and groundwater contamination to PHS/EHD by February 25, <br /> 1993 . <br /> The data collected to date on the gradient direction for this <br /> site indicate that the gradient direction is divergent. This may <br /> be due to the influence of the many domestic wells in the area. <br /> The additional monitoring wells will generate needed information <br /> on the groundwater contaminant distribution and the groundwater <br /> gradient flow directions. They will also provide a better <br /> understanding of the influences affecting groundwater flow <br /> patterns and plume migration for this site. <br /> The detection limits used for the benzene, toluene, ethylbenzene <br /> and xylene analysis in the groundwater were too high at 1. 0 parts <br /> per billion (ppb) . A detection limit of at least 0. 3 ppb should <br /> be used for future groundwater analysis. <br /> A Division of San Joaquin Counry Health Cy Services 1/ <br />