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■ <br /> TAIT Environmental Management, Inc. <br /> f Environmental - Engmneenng - Compliance <br /> March 16, 2001 <br /> Ms. Kerry Wasson <br /> County of San Joaquin <br /> Facilities Management Division <br /> 1722 East Scotts Avenue <br /> Stockton, California 95205 <br /> Subject: Workplan to Perform an Additional Site Assessment at the San Joaquin County Motor <br /> Pool Facility, 1810 East Hazelton Avenue, Stockton, California <br /> Dear Ms. Wasson: <br /> Tait Environmental Management, Inc. (TEM), is pleased to submit this workplan on behalf of the County of <br /> San Joaquin Public Works to perform an additional soil and groundwater site assessment at the San Joaquin <br /> County Motor Pool facility (Site) located at 1810 East Hazelton Avenue, Stockton, San Joaquin County, <br /> California. <br /> BACKGROUND <br /> This work plan has been prepared based on the results of a site assessment conducted by TEM during the <br /> period March — April 1999. The results of the site assessment were reported by TEM to the San Joaquin <br /> County Public Health Services, Environmental Health Division in the Site Assessment Report for San Joaquin <br /> County Motor Pool Facility, dated May 11, 1999. Overall, the results of the site assessment found elevated <br /> concentrations of petroleum hydrocarbons as gasoline(TPHg); benzene, toluene, ethylbenzene, total xylenes <br /> (BTEX); and methyl-tert-butyl ether (MTBE) in the soil and groundwater. The San Joaquin-County Public <br /> Health Services (SJCPHS), Environmental Health Division reviewed the report and in correspondence dated <br /> August 18, 1999 directed that the lateral and vertical extent of soil and groundwater contamination be <br /> delineated at the Site. <br /> TECHNICAL APPROACH <br /> The additional site assessment will consist of two phases. Phase One will involve drilling exploratory borings <br /> on a grid pattern to delineate the lateral and vertical extent of soil and groundwater contamination. Phase <br /> Two will involve locating and installing groundwater remediation and plume monitoring wells based on the <br /> results of Phase One. <br /> Phase One <br /> The Phase One exploratory borings will consist of initial and step-out borings. The locations of the initial <br /> borings are illustrated on Figure 1 (attached). Advancement and sampling of the exploratory borings will <br /> proceed until the lateral and vertical extent of soil and groundwater impact is delineated based on the results <br /> of laboratory analyses. If soil and/or groundwater contamination is evident in samples collected from the <br /> initial borings, the grid pattern will be expanded to locate and advance additional step-out borings. <br /> Advancement of step-out borings would continue until soil and/or groundwater impact is no longer evident. <br /> Locations and rationale for the step-out borings, if any, would be reported verbally and via correspondence to <br /> the San Joaquin County Public Health Services, Environmental Health Division. A separate work plan for <br /> advancement of step-out borings would not be submitted. This reporting scenario will allow the <br /> supplementary contamination assessment to proceed continuously. <br /> 701 North Parlxcenter Drive• Santa Ana, California 92705 • (714)560-8200 • (714)560-8235 fax <br /> Regional Offices: San Diego •Concord •Sacramento •Phoenix •Reno <br /> www.TAIT.com <br />