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1 � <br /> PUBLIC FTEALTH SERVItTS <br /> SAN JOAQUIN COUNTY Q :� <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 4 ��P <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 ' oR <br /> 209/468-3420 QV 121%7 <br /> WILLIAM CHASE ROBERT CHASE <br /> AUTO INVESTMENT CO &ASSOC AUTO INVESTMENT CO &ASSOC <br /> HARTMANN &SETNESS 6310 HIDDEN ACRES <br /> 3203 W MARCH LANE, SUITE 120 STOCKTON CA 95212 <br /> STOCKTON CA 95219 <br /> RE: 423 N MADISON SITE CODE: 1163457 <br /> STOCKTON CA <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has <br /> reviewed the September 30, 1997 Addendum to Corrective Action Plan, the February 28, 1997 <br /> Revised Corrective Action Plan, and the February 1996 Corrective Action Plan (CAP), prepared <br /> by Advanced GeoEnviron mental (AGE) for the above referenced site. These documents together <br /> comprise the completed CAP. <br /> There are four locations at the site where Underground Storage Tanks were located. The primary <br /> location is the area where tanks 3,4,5 and 6 were nested. Two additional areas of concern have <br /> been identified as the tank 1 location and the tank 8 location. Data obtained from assessment of <br /> tank area 2 indicates that additional corrective action is unnecessary. <br /> Tank Area 3,4,5,6 <br /> In the CAP AGE states that hydrocarbon concentrations in ground water show a decreasing trend <br /> and the impacted groundwater plume does not appear to be migrating. AGE recommends natural <br /> attenuation as the most cost effective remedial alternative for this area. PHS/EHD concurs with <br /> this conclusion based on groundwater monitoring data. <br /> Tank Area I <br /> In the CAP AGE estimates that removal of 150 cubic yards of both contaminated soil and <br /> overburden will be required to remove all but small volumes of impacted soil. PHS/EHD has data, <br /> obtained during the assessment of this area, which indicates that contamination is present at 15 <br /> feet and non detect at 20 feet. Groundwater was measured at approximately 20 feet below grade <br /> on November 4, 1997. There is less than 5 feet between contamination and groundwater. In order <br /> to prevent the migration of contamination from soil to groundwater corrective action in this area is <br /> indicated. PHS/EHD concurs with the selected alternative of overexcavation due to the estimated <br /> volume of affected soil. <br /> Tank Area 8 <br /> Soil contamination is documented to the total depth of borings GP-1, GP-2 and GP-4 at 25 feet. <br /> The extent of contamination at depths exceeding 25 feet is currently unknown. Groundwater at <br /> this site is, currently, approximately 20 feet below grade. The general lithology from 15 to 25 feet <br /> is sand. Excavation below groundwater in sandy soil requires the use of dewatering equipment <br /> and the use of equipment to mitigate the potential for caving. In the CAP, AGE recommends <br /> A Division of San Joaquin County Health Care Services <br />