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ROPHYSICAL <br /> NORCAL CONSULTANTS , INC . <br /> 1 � <br /> ' <br /> February 10, 2005 <br /> ' Mr. Jay G. Kamine <br /> URS Corporation <br /> 2520 Venture Oaks Way, Suite 250 <br /> Sacramento, CA 95833-3200 <br /> Subject: Geophysical Investigation <br /> World Enterprises Site, Stockton, CA <br /> NORCAL Job # 05-628.52 <br /> ' Dear Mr. Kamine: <br /> ' This report presents the findings of the geophysical investigation performed by NORCAL <br /> Geophysical Consultants,Inc. at the World Enterprises Site in Stockton, CA. The field survey was <br /> conducted on January 17-19,and February 1,2005 by NORCAL Geophysicist Donald J.Kirker and <br /> ' geophysical technicians Travis Black and Chris Blom. Logistical support was provided by Jay <br /> Kamine of URS Corporation. This investigation was conducted under URS Contract No. <br /> SC04S4200 and Radio Shack Contract No. 1533-03-14. <br /> ' PURPOSE AND SITE DESCRIPTION <br /> ' According to URS Corporation,the World Enterprises property was formerly permitted as a debris <br /> disposal site during the 1970's. The disposed debris included wood,concrete,and other rubble from <br /> ' demolished buildings,as well as some residential trash. Also,methane gas has been detected within <br /> the northern perimeter of the site. Since the location of this debris is poorly documented,the purpose <br /> of this geophysical investigation was to obtain subsurface information to aid in further identifying <br /> the lateral and vertical extent of buried landfill material. <br /> The survey area, designated by URS Corporation, is a vacant parcel of land that covers <br /> ' approximately 8.9 acres, as shown on Plate 1. It is bound by a wire fence on all sides, and is <br /> accessed from French Camp Turnpike Road through a small gate in the southwest corner. The <br /> survey area is relatively flat and is covered with grass and low vegetation. Several vapor monitoring <br /> ' wells are located around the perimeter of the property. <br /> FIELD INVESTIGATIONS <br /> ' Equipment <br /> ' Based on the objective of this investigation, we used the electromagnetic (EM), vertical magnetic <br /> gradient(VMG), and electrical resistivity(ER)methods. The EM method is used to determine the <br /> approximate boundaries(lateral extent)of the buried landfill material. The EM records two different <br /> tmeasurements referred to as terrain conductivity (TC) and in-phase component (IPC). TC values <br /> indicate the electrical conductivity of the subsurface to a depth of approximately 12 to 15 feet. These <br /> ' 321A BLODGETT STREET • COTATI, CA 94931 • TELEPHONE (707) 796-7170 • FAX (707) 796-7175 <br /> www.norcalgeophysical.com <br />