SITE HISTORY - Laserfiche WebLink

Home Browse Search

r+ ARCADIS Ms. Lori Duncan October 8, 2008 northwest and southeast of P3)were below the California Regional Water Quality Control Board (RWQCB) Environmental.Screening Levels (ESL)for deep soils (RWQCB, 2005). Soil samples collected from 65, 70, 75, and 85 feet bgs in borings B1 and B2 had no detections above the laboratory reporting limits. Summary tables of historical soil analytical results are provided in Attachment 1. Historical boring locations are included in Attachment 2. One 2 inch outside diameter(OD) polyvinyl chloride (PVC) monitoring well (MW-1, screened from 65 to 85 feet bgs)was installed on August 21, 2006. Groundwater samples collected from MW-1 during the fourth quarter of 2006 had concentrations of TPH-g (1,300 micrograms per liter [Ng/L]), toluene(9 pg/L), ethylbenzene(2 pg/L), total xylenes (22.5 pg/L), and 1,2-dichloroethane(1,2-DCA)(970 pg/L). Petroleum hydrocarbons have not been detected in water samples collected from the domestic well located near the northern property,boundary. Summary tables of historical groundwater analytical results are provided in Attachment 1. L Regional Geology 9Y The Stockton area is underlain to a depth of approximately 150 feet below grade by Holocene age alluvium and the Victor Formation, which is comprised of unconsolidated Quaternary age deposits. These formations are heterogeneous consisting of laterally discontinuous lenses of sand and gravel with varying amounts of sand and silt interstratified with units of clay and silt. Hydrology and Hydrogeology Surface water bodies present in the vicinity of the site include Morman Slough, _ located approximately 3,000 feet to the north,.and Walker Slough located approximately 6,000 feet to the south. Groundwater monitoring and sampling for MW-1 was initiated during the third quarter 2006. Monitoring and sampling was not performed after the fourth quarter 2006. However, monitoring and sampling activities resumed during the second quarter �+ 2008 following activities described within this report. Depth to water(DTW) measurements show groundwater levels ranging from 57.35 feet bgs (MW-3, June 2008)to 65.60 feet bgs (MW-1, November 2006). Page: 2/10 --cis-usbo icedata\Sacramento-CA\ENVICHEVROM309075\8Deliverables\Repods\Assessment\309075 Assessment Report_181810950.doc.