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GEOPHYSICAL <br /> CONSULTANTS, INC . <br /> •lig <br /> September 25, 2001 <br /> Ms. Aubrey Cool <br /> Cambria Environmental Technology, Inc. <br /> 270 Perkins Street <br /> Sonoma, CA 95476 <br /> Subject: Geophysical Investigation <br /> Former Shell Service Station <br /> Stockton, California <br /> Dear Ms. Cool: <br /> This letter presents the findings of the geophysical investigation performed at a former Shell <br /> Service Station located at 1267 Country Club Boulevard, Stockton, California. The investigation <br /> was conducted on September 6, 2001 by NORCAL Geophysicist David Bissiri. Ms. Cynthia Vasko <br /> of Cambria Environmental Technology assisted with the field work. <br /> SITE DESCRIPTION <br /> The former service station property is currently occupied by a vacant bank building. The site is <br /> • bounded by Pershing Avenue on the west; Country Club Boulevard on the south; and block walls <br /> on the north and east (see Plate 1). The area of investigation is an approximately 165- by 105- <br /> foot "U"-shaped portion of the property surrounding the bank building. The bank building is <br /> surrounded by hedges on the south and west and has three vehicle aisles under a canopy on the <br /> north. In addition, three monitoring wells, two storm drain catch basins, and a steel door lying on <br /> the ground are also present. <br /> PURPOSE <br /> The purpose of the geophysical investigation is to determine if underground storage tanks(UST's), <br /> or other notable subsurface features exist within the investigation area. <br /> METHODS <br /> The geophysical methods used for this investigation include total field magnetic intensity (TF), <br /> metal detection (MD), and ground penetrating radar(GPR). In brief, TF is used to determine the <br /> locations of buried ferrous objects; MD is used to detect metallic objects and determine their <br /> extent; GPR is used to further characterize buried objects or features detected with TF and MD. <br /> Detailed descriptions of these geophysical methods and instrumentation are provided in Appendix <br /> "A» <br /> DATA ACQUISITION <br /> We performed the geophysical investigation using the seven tasks summarized below: <br /> Task 1 The MD and GPR methods were initially used in two portions of the site that could not be <br /> investigated with TF because of the presence of physical obstructions or expected magnetic <br /> 1350 INDUSTRIAL AVENUE, SUITE A • PETALUMA, CA 94952 • TELEPHONE (707) 763-1312 • FAX (707) 762-5587 <br /> www.norcalgeophysical.com <br />