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ENVIRONtENTAL HEALTHINEPARTMENT <br />Donna K. Heran, R.E.H.S. <br />Director <br />Al Olsen, R.E.H.S. <br />Program Manager <br />Laurie A. Cotulla, R.E.H.S. <br />Program Manager <br />SAN JOAQUIN COUNTY <br />304 East Weber Avenue, Third Floor <br />Stockton, California 95202-2708 <br />Telephone: (209) 468-3420 <br />Fax: (209) 464-0138 <br />Website: www.sjgov.org/ehd/ <br />Unit Supervisors <br />Carl Borgman, R.E.H.S. <br />Mike Huggins, R.E.H.S., R.D.I. <br />Douglas W. Wilson, R.E.H.S. <br />Margaret Lagorio, R.E.H.S. <br />Robert McClellon, R.E.H.S. <br />Jeff Carruesco, R.E.H.S. <br />WAN 131 <br />DONNA SARTINI—GARDNER RONALD JR & BONNIE BARBER <br />1206 W STRUCK 10411 SMALL RD <br />ORANGE CA 92667 MANTECA CA 95336 <br />RE: 26056 (26090) N. Thornton Road, APN 00115048 <br />Thornton, CA <br />San Joaquin County Environmental Health Department (EHD) has reviewed the <br />"Work Plan to Further Define the Lateral and Vertical Extent of Contamination <br />and Access the Risk to Thornton Municipal Well No. 2" dated November 29, <br />2005, prepared by H2OGEOL for the above referenced site. The work plan is <br />not approved. A new work plan is to be prepared based on the following EHD <br />comments and submitted to EHD by February 15, 2006. <br />The lateral and vertical extent of soil contamination cannot be defined by <br />collecting soil samples from a depth of four feet to the depth of first encountered <br />groundwater. Depth to groundwater has fluctuated between 8 and 11 feet below <br />ground surface (bgs). The soil samples collected beneath the underground <br />storage tanks (UST's) when they were removed and were confirmed to be <br />contaminated were collected from a depth of 12 feet bgs. Remarks on the boring <br />logs and/or soil sample results from borings SB2, SB4, SB7, SB8 and MW4, as <br />well as excavation floor samples at 15 feet and the excavation north sidewall <br />sample at 11 feet all showed soil contamination below groundwater depth. The <br />lateral and vertical investigation of soil contamination should occur at depths <br />where contamination has been found previously and continue until contamination <br />is no longer found (i.e. SB4 at 30.5 feet) which is below first encountered <br />groundwater. <br />H2OGEOL did not provide a technical justification for the geoprobe investigation. <br />Collection and analysis of groundwater samples from monitoring wells MW1, <br />MW2, MW5 and MW6 may continue to define the extent of the shallow <br />groundwater contamination to the east, south and southwest of the former UST <br />location. At this time, EHD does not consider a geoprobe investigation of shallow <br />groundwater to be warranted. <br />The proposed locations for the deeper screened monitoring wells may be <br />appropriate but the screen interval may be too shallow and too long. The well log <br />of the Thornton Municipal well indicates there is sand from 25 to 60 feet below <br />grade so the deeper portions of this sand interval are of concern. In sand, 5 feet