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11 September 1997 AGE-NC Project No. 97-0369 Page 2 of 5 south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively. The Great Valley Province is subdivided into two major divisions designated the Sacramento and San Joaquin Valleys. FurtheMlore, based on the General Sol] Map from the San Joaquin County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Jacktone-Hollenbeek-Stockton (JHS) association. The JI-IS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils. The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from mixed rock sources. 2.3. REGIONAL GROUND WATER DEPTH AND GRADIENT According to the map titled Limes Of Equal Depth To Groundrt)aler - Spring 1996, published by the San Joaquin County Flood Control and Water Conservation District, the estimated depth to ground Nvater at the property is between 10 and 20-feet below surface grade (bsg). Prevailing ground water flow direction in western Stockton is generally toward the northeast, although flow directions may vary locally and seasonably. 3.0. SCOPE OF R'ORK In a letter dated 21 July 1997, the PHS-EHD directed that a Nvork plan be submitted to define both the lateral and vertical extent of petroleum contamination at the site. Therefore, subsurface assessment will be necessary to delineate the full extent of hydrocarbon-impacted soil and/or ground water at the site. 3.1. DRILLING AND SAMPLING AGE proposes to initially advance three soil probe borings near each former UST area to a minimum depth of 20-feet bsg. Probings will be advanced using a Geoprobe 5400 soil probing unit. Proposed soil probe boring locations are illustrated on Figure 2. Discrete soil samples will be collected at five-foot intervals beginning at a depth of 5-feet bsg utilizing a Geoprobe soil sampling assembly loaded with pre-cleaned 1. 125-inch by 6-inch brass sleeves. At least one probe boring near each UST location will be continuously sampled using a Geoprobe Macro-core sampler and 36-inch acetate sleeves. Soil samples will be preserved by covering both ends of the second brass sleeve with Teflon sheets, plastic end caps and sealed with tape. Each sample sleeve will be labeled with the following information: soil probe boring location, depth, time, date and Advanced GcoEnvironmental,Inc.