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j Unocal Corporation <br /> f{ 2000 Crow Canyon Place,Suite 400 <br /> PO Box 5155 <br /> San Ramon,California 94583 <br /> Telephone(510)867-0760 t , , _ <br /> Facsimile(510)277-2309 kr ' <br /> UN®CA1. 76 � z9 p�� 2: ro <br /> Northern Region <br /> Corporate Environmental <br /> Remediation&Technology November 23, 1993 <br /> Mr Harlin Knoll <br /> San Joaquin County Public Health Services <br /> 445 North San Joaquin Street <br /> P O Box 2009 <br /> Stockton, CA 95201 <br /> Former Unocal Station No 6015 <br /> 601 E Kettleman Lane <br /> Lodi, CA <br /> Dear Mr Knoll <br /> Please find attached for your reference, a Site Investigation Summary of the subject site <br /> prepared by Kapreahan Engineering, Inc (KEI) on behalf of Unocal Corporation This <br /> summary examines in detail the concerns of Mr Steve Schneider of your office, letter dated <br /> November 6, 1992 and also summarizes the work conducted on the site since that time In light <br /> of the additional SESOIL analysis performed, the review of the regional groundwater hydrology, <br /> the location of potential receptors and evaluation of a complete hydrologic cycle of groundwater <br /> monitoring, Unocal is again requesting closure of this site <br /> Both KEI and Unocal feel the very small amount of residual contamination remaining in the soil <br /> and water does not constitute a health and environmental condition requiring additional work <br /> nor are the concentrations at levels which exceed taste and odor goals as recommended by Jon <br /> B Marshack, the Environmental Specialist for the Central Valley RWQCB in his May 13, 1993 <br /> memorandum We feel that the source of the potential contamination was removed during UST <br /> replacement and subsequent over-excavation of the tank pits Modeling (SESOIL) using a <br /> worst-case situation suggest that any residual hydrocarbons might reach the water table in the <br /> approximately 10 -15 year range We would consider it very unusual for natural degradation of <br /> any remaining hydrocarbons not to occur during this time period <br /> Concern has been expressed concerning contamination found during the installation of <br /> monitoring wells 1 (offsetting the UST pit) and 6 (on the eastern side of the tank pit) Water <br /> quality over the past year in these wells has never exceeded water quality goals for any BTEX <br /> constituent, therefore, we do not consider this residual contamination a threat to groundwater <br />