ARCHIVED REPORTS XR0008681 - Laserfiche WebLink

Home Browse Search

S ECOR QUARTERLY SUMMARY REPORT Second Quarter 2005 Former 76 Service Station #4409 1502 North EI Dorado Street, Stockton, California City/County ID #: Stockton County: San Joaquin i SITE DESCRIPTION The site is located on the northeast corner of North EI Dorado Street and East Harding Way 6d in Stockton, California. The site is a former 76 Unocal service station that dispensed gasoline and diesel fuel beginning in 1982. No fuel has been dispensed since the underground storage tanks (USTs) were removed in 1999. The surrounding land is a mix of commercial and residential properties. There is a co-mingled plume study being done with the neighboring ARCO station located west of the site at 16 East Harding Way. GROUNDWATER MONITORING ZONE CLASSIFICATION Prior to the most recent vertical assessment conducted in November 2004 and April 2005, 'shallow' and 'deep' were used to identify the groundwater monitoring zone for wells � completed to depths ranging from 45 to 50 feet bgs (MW-1 through MW-4) and 79 to 83 feet bgs (MW-5 through MW-14), respectively. However, the three wells installed as part of the most recent vertical assessment were completed to a depth of approximately 120 feet bgs, which is below the previously termed 'deep' groundwater monitoring zone. Therefore, 'shallow' and 'deep' will no longer be used to describe the groundwater monitoring zones and will be replaced by the A monitoring zone and the B monitoring zone, respectively. The three new wells (MW-15 through MW-17) installed to approximately 120 feet bgs are in the L. third groundwater monitoring zone, which will be classified as the C monitoring zone. PREVIOUS ASSESSMENT &W On April 7, 1999, three 10,000-gallon capacity underground storage tanks (USTs), which contained gasoline and diesel fuel, were removed from the site. The tank pit area was overexcavated. Excavation dimensions were approximately 35 feet by 40 feet by 15 feet �" deep. Initial remedial activities included source removal by excavation of obviously impacted soil `B to a depth of approximately 18 feet below ground surface (bgs) beneath the center of the western fuel tank. Additional remedial activities included source removal by excavation of obviously impacted soil in the area beneath the former dispenser and product lines. A concrete pad restricted the lateral extent of excavation. During excavation of impacted soil, unidentified fiberglass piping was found. Additional excavation and sampling was completed on April 8, 1999, to remove the unidentified piping. Samples were collected from the bottom and sidewalls of the excavated area. V