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28 August 2003 AGE -NC Project No. 03-1063 Page 3 of 7 2.4. REGIONAL GEOLOGIC CONDITIONS The site is situated within the Great Valley Geomorphic Province of California, a large, elongate northwest tending, asymmetric structural trough. The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to Recent, creating a nearly flat lying alluvial plain, which extends from the Tehachapi Mountains in the 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. Rocks composing the basement complex of the province have not been completely defined but are believed to be of metamorphic and igneous origin. The Great Valley Province has been subdivided into two major divisions identified as the Sacramento and San Joaquin Valleys. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500 -square mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. 3.0. PROCEDURES Procedures for soil excavation, soil sampling, soil disposal and monitoring well abandonment are outlined below. The work was preformed in accordance with AGES Interim Soil Remediation Work Plan, dated 25 July 2003, included as Appendix A. Neither the San Joaquin County Environmental Health Department (SJCEHD) nor the Regional Water Quality Control Board required the remediation of the contamination associated with the former hydraulic lift. Furthermore, both agencies declined to provide oversight and review of the work plan and/or reports. The excavation work at the site was performed as a voluntary operation for site mitigation. The abandonment of the monitoring wells was performed under permit from the SJCEHD. Furthermore, all field procedures were overseen by an AGE representative under the supervision of a California Registered Geologist. 3.1. SOIL EXCAVATION On 25 July 2003, hydrocarbon -impacted soil from a former hydraulic lift area; AGE personnel were on site to collect and field -screen soil samples and to direct the excavation. Excavation was performed using a backhoe and operator provided by Valued Engineering of Stockton, California. Approximately 90 tons of soil were excavated from the area of a former dual -post -hydraulic lift (vicinity of probe boring P-6). As excavation proceeded, the soil was monitored for the presence of Advanced GeoEnvironmental, Inc.