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California Regional Water Quality Control Board <br /> Central Valley Region ion <br /> `A� <br /> Steven T.Butler,Chair , yr; �1 <br /> Winston H.Hickox 'r Gray Davis <br /> Secretary for Sacramento Main Officev , Governor <br /> Environmental Internet Address: http://www.swrcb.ca.gov/--rwgcb5 P" ��1 3 7 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000.FAX(916)255-3015 <br /> 30 July 1999 <br /> Ms. Katie Hower <br /> Chevron Environmental Management Co. <br /> P. O. Box 6012 <br /> San Ramon, CA 94583-0712 <br /> SOIL AND GROUNDWATER INVESTIGATION, MANSFIELD PROPERTY,TRACY, <br /> SAN JOAQUIN COUNTY <br /> I have reviewed the June 1999 Soil and Groundwater Investigation and Site Status Report, Mansfield <br /> Property, conducted by Geomatrix Consultants for Chevron Pipe Line Company(CPL). The extent of <br /> soil contamination has been defined. A grab groundwater sample from the original soil boring MB-1, <br /> located within a soil contamination plume, has concentrations of 660 parts per billion(ppb) total <br /> petroleum hydrocarbons (TPH) as gasoline and 700 ppb TPH as diesel. There are no significant <br /> detections of benzene, toluene, ethyl-benzene, and xylenes in the grab groundwater samples. <br /> Also, there are no detections of TPHg or TPHd in the groundwater surrounding the identified soil <br /> contamination. <br /> Groundwater samples were not taken in all the downgradient pathways. Therefore, Geomatrix <br /> recommends collecting one additional sample downgradient of MB-1 to define the extent of soil and <br /> groundwater contamination in the northeasterly direction. This proposal is approved but the placement <br /> for the additional boring is not identified and the schedule for the additional work is not included in this <br /> report. By 15 August 1999 please submit a map indicating where the proposed boring will be located, <br /> the analysis that will be performed on the soil and groundwater, and the schedule for conducting the <br /> work and submitting the results. <br /> I will be leaving the board in Mid August, and Mr. Philip.Isorena will take over this project. If you have <br /> any questions please call me at (916) 255-3076 until 17 August or Mr. Isorena at(916) 255-3081 after <br /> that time. <br /> KRISTEN ROCHA <br /> Site Cleanup Unit <br /> cc: Mr. Michael Infurna, San Joaquin County Public Health Services, Stockton <br /> Ms. Darlene Mansfield, Mansfield Property, Tracy <br /> Ms. Elizabeth Lu, Geomatrix Consultants Inc., San Ramon <br /> Mr. Michael Kiem, Geomatrix Consultants Inc., San Ramon <br /> California Environmental Protection Agency <br /> 0 Recycled Paper <br />