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�. Additional Site Assessment Work Plan - February 2003 <br /> ' BOB'S MUFFLER SHOP <br /> 466 Moffat Boulevard, Manteca, California <br /> ' 1.0: INTRODUCTION <br /> t At the request of Mr Tom Barbour, Advanced GeoEnvironmental,-Inc. (AGE) has prepared the <br /> enclosed additional site assessment work plan for 466 Moffat Boulevard,Manteca,California(site). <br /> The scope of work includes the advancement of two offsite soil borings for the collection of soil <br /> and ground water samples. The location of the site is illustrated on Figure 1. A plan of the site is <br /> illustrated on Figure 2. <br /> ' The San Joaquin County Environmental Health Department (EHD) has directed by letter dated 25 <br /> September 2002 that a workplan be prepared to investigate the lateral extent of contamination at <br /> the site in the down-gradient direction, towards the northwest(Appendix A). This work plan has <br /> ' been prepared in accordance with Central Valley Regional Water Quality Control Board <br /> (CVRWQCB) guidelines for the investigation of underground storage tanks (UST) sites. <br /> 2.0. BACKGROUND <br /> ' The site is situated in a commercial area of Manteca, and consists of a roughly triangular parcel of <br /> land bordered on the northeast by Moffat Boulevard. Structures on` the site include one small <br /> building which formerly housed the muffler shop, a tall canopy and two former pump islands. The <br /> ' site setting is,illustrated in Figure 1. The layout of the property and locations of wells and soil <br /> borings are depicted in Figure 2. <br /> 2.1. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING <br /> ' The site is situated within the southern portion of the Great Valley Geomorphic Province. of <br /> California, a large, elongate, northwest trending, asymmetric structural trough; the northern and <br /> ' southern portions of the Province have been designated the Sacramento and San Joaquin Valleys, <br /> respectively.The Province is bordered by the Coast Ranges to the west,the Klamath Mountains and <br /> Cascade Range to the north, and the Sierra Nevada to the east. <br /> 1 The Great Valley,has been filled with sediments derived from both marine and continental's ources. <br /> Thickness of the sedimentary fill ranges from thin'veneers along the valley edges to more than <br /> 20,000 feet in the south central portion of the valley.The sedimentary formations range iri age from <br /> Jurassic to Recent,with the older deposits being primarily marine in origin and the younger deposits <br /> being primarily continental. Continental-:derived sediments were primarily deposited in lacustrine, <br /> fluvial;and alluvial environments with sediment sources being the mountain ranges surrounding the' <br /> valley(Olmsted and Davis, 1961);the site itself is located on unconsolidated and semi-consolidated <br /> -.alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and <br /> 1 <br /> Advanced GeoEnvironmedtal,Inc. <br /> 1 <br />