ARCHIVED REPORTS XR0012864 - Laserfiche WebLink

Home Browse Search

Stockton 99 Speedway Preliminary Endangerment Assessment Workplan April 12,2007 t 2.0 PROJECT SCOPING 2.1 Project Goals i The goal of the Stockton 99 Speedway PEA is to evaluate the risks to human health and the environment posed by chemicals detected at the Site and to implement appropriate remedial actions to mitigate the identified risks. Scoping includes evaluating the Site background and existing data to develop a [ preliminary conceptual model for the Site and to develop a plan for gathering additional data as necessary. These data will be collected to meet the objectives of the PEA. Background information on the Site is presented as a basis for this Workplan and future remedial action decisions. This information will be synthesized and expanded upon in the PEA Report. The conceptual model of the Site may be modified, pending evaluation of the results gathered during the PEA. 2.2 Geographic Setting The City of Stockton is located in the Great Valley Province in the northern San Joaquin Valley of California, a broad structural trough situated between the Coast Ranges on the west and the Sierra Nevada on the east. The City of Stockton is located on the low alluvial fan and plain deposits of the Calaveras River and other streams that drain the uplands and foothills of the Sierra Nevada to the east (Page, 1986). 2.3 Hydrogeological Setting In the Stockton area, groundwater occurs primarily within a leaky-aquifer system of Younger and Older Alluvium, the Turlock Lake, and the Laguna Formations (Page, 1986). Sediments from these formations formed deltas and fans at the apex of the Calaveras River and other stream valleys. The hydrogeologic setting in the Stockton area is comprised of a sedimentary sequence of alluvial fan and stream deposits of sand, gravel and silt. Gravels and sand .in the alluvium yield significant quantities of groundwater to wells (Page 1986). No field investigations conducted at the Site have encountered groundwater. However, a Phase I Environmental Site Assessment conducted by Kleinfelder for the Site indicates that groundwater is expected to be encountered at a depth of 55-60 feet below ground surface (bgs), (Kleinfelder 2005a). Li PEa M00an.Finai.doc 2-1 The Source Group,Inc.