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CV31\ <br /> A S S O C I A T E S I N C <br /> Back round <br /> MTBE and total xylenes have been detected in groundwater samples taken from well MW-1 since <br /> monitoring began in February 1999 Total xylenes were detected in well MW-1 at a concentration <br /> of 3 8 ppb in February 1999 and have not been detected during any of the other sampling events <br /> MTBE was detected in well MW-1 at a concentration of 514 ppb in February 1999 MTBE <br /> concentrations in well MW-1 have decreased over time and MTBE was not detected during the <br /> most recent sampling event on November 28, 2000 <br /> a letter from the San Joaquin County Public Health Services, Environmental Health Division <br /> (PHS/EHD) dated July 20, 2000, PHS/EHD requested that an additional subsurface investigation <br /> be conducted to determine the lateral and vertical extent of the MTBE plume ATC is submitting <br /> this work plan in an effort to meet that request <br /> Scope of Work <br /> Planning <br /> Following the approval of this workplan, ATC will schedule field personnel and equipment, notify <br /> Underground Services Alert to locate underground utilities as required, and perform any other <br /> necessary field preparation and fob start-up activities A private underground utility locating <br /> service may be warranted due to the proximity of nearby underground sewer, gas, and electrical <br /> lines A well permit application and associated fee (check #550) are attached to this report <br /> Installation of Soil Borings <br /> To further assess the extent of Impacted soil and groundwater, a total of five soil borings will be <br /> advanced at the site (Figure 2) To address lateral definition, four perimeter borings will be <br /> advanced to depths of approximately 55 feet bgs One boring will be advanced approximately 15 <br /> feet north ofMWl, one boring will be advanced approximately 30 feet east of MW1, one boring <br /> will be advanced approximately 30 feet west-southwest ofMW1, and one boring will be advanced <br /> in the downgradient direction from MW 1, approximately 35 feet south of MW 1 To address <br /> vertical definition, one boring will be advanced approximately 5 feet south of NMI to a depth of <br /> at least 80 feet bgs The proposed boring locations are shown on Figure 2 <br /> The four shallow borings will be advanced utilizing hollow-stem auger drilling techniques A <br /> State-licensed (C57) drilling company will conduct drilling and a field geologist will be present to <br /> log all soil samples Descriptions of soil types encountered and sample collection intervals will be <br /> recorded on boring logs Soil samples will be collected at five-foot intervals and all soil samples <br /> will be field screened with an FID for volatile organic compounds (VOCs) At least two samples <br /> from each of the borings will be submitted for laboratory analysis Sol] sample selection will be <br /> based on FID measurements and field observations (i a odor and soil discoloration) Soil cuttings <br /> generated from drilling activities will be stored on-site in 55-gallon steel drums Grab <br /> groundwater samples will be collected from each boring at first encountered groundwater, <br /> w lwordpro117292117292 011Reporlsl4 qmr 2000 doc 3 <br />