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RIECENED <br /> BBI <br />' JUL 13 2006 <br /> an ARCADIS company ENVIRONMENT HEALTH <br /> PERMIT/SERVICES <br /> 1 <br /> Transmitted Via Federal Express <br /> June 27, 2006 <br />' James L L Barton, P G <br /> Engineering Geologist <br />' Regional Water Quality Control Board <br /> Central Valley Region <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, California 95670 <br /> Re Second Quarter 2006 Groundwater Monitoring Report <br />' Chevron Facility 9-6171 <br /> 6633 Pacific Avenue <br /> Stockton,California <br /> BBL Project# 44646 002#10 <br />' Dear Mr Barton <br />' This Second Quarter 2006 Groundwater Monitoring Report has been prepared by Blasland, Bouck& Lee, <br /> Inc (BBL) for Chevron Service Station 9-6171 located at 6633 Pacific Avenue in Stockton, California <br /> Quarterly groundwater monitoring and sampling was conducted on site on April 20, 2006 by Gettler- <br /> Ryan Inc (G-R) on behalf of Chevron The groundwater monitoring program consists of water-level- <br /> elevation monitoring, sample collection, and chemical analysis of samples as described below <br /> Field Procedures <br /> G-R collected water-level measurements from 13 monitoring wells on April 20, 2006 Water-level <br /> measurements were used to calculate the water-table elevation at each well and develop a potentiometnc <br /> surface map for the site A groundwater elevation was not calculated for MW-14 because a surveyed top <br /> of well casing reference point is not available for the well These data allowed for subsequent estimation <br /> of the groundwater flow direction <br /> Groundwater samples were subsequently collected from 12 monitoring wells (MW-2, MW-3 MW4 <br /> MW-5, MW-6, MW-7, MW-9, MW-10, MW-11D, MW-12, MW-13, and MW-14) Samples were not <br /> collected from monitoring well MW-8 due to insufficient water Groundwater samples were collected in <br /> accordance with California Environmental Protection Agency (CaIEPA) procedures outlined in <br /> Representative Sampling of Groundwater for Hazardous Substances (CaIEPA, 1995) <br />' A three-well-volume purging and sample technique using a decontaminated stack pump and/or disposable <br /> bailers was used for groundwater purging and sample collection from monitoring wells with the exception <br /> of monitoring well MW-9 Due to the minimal amount of water in MW-9, the monitoring well was not <br /> 009603054 doc <br /> 2033 North Main Street.Suite 340•Walnut Creek,CA 94596 <br /> Tel(925)274-1100•Fax(925)274-1103+www bbl-inc com.Offices Nationwide <br />