ARCHIVED REPORTS_XR0002658 - Laserfiche WebLink

Home Browse Search

November 12, 1996 Page 2 1 � r-• '�� - — and consisted of two generations of produci facilities (Figure 2)4x The first generation _ �____w facilities, based on available data, consisted of four steel underground storage tanks (USTs), (4,000-, 3,000-, 1,000-, and 550-gallon) which were initially abandoned in place In 1984, a second set of USTs were installed and consisted of three fiberglass gasoline USTs (10,000-gallon) Iocated in a common excavation in the central portion of f the site, and one fiberglass waste-oil UST (1,000-gallon) located behind the former service station building Both generations of facilities have been rernoved from the site t The site is bounded to the east by a Unocal service station, to the west by a residence, to the south by a restaurant and ARCO AM/PM`Mini-Mart, and to the north by medical offices ` 1 Geology/Hydrogeology The site is Iocated in the northern part of the San Joaquin Valley and is underlain by approximately 3,000 feet of alluvial gravel, sand, silt, and clay Groundwater in these alluvial deposits'is unconfined to serniconfined (GTI, March 1994) Significant ground- water extraction for irrigation and public water supply has reduced groundwater eleva- tions in Stockton to approximately -30 to,-40 feet mean sea level (MSL) Subsurface investigations indicate that the site is underlain by interbedded clayey silts, and silty clays with sand Ienses to the total depth explored (70 feet below ground surface [bgs]) Historically, depth to groundwater has ranged from 35 36 feet'bgs (Well MW-8, i February 7, 1989)to 58 01 feet bgs (Well MW_10, October 26, 1992) Quarterly A groundwater monitoring data from November 1988 to present indicate that groundwater beneath the site consistently flows in a northeasterly direction at an approximate gradient of 0 002 to 0 003 feet per feet The nearest surface water to the site is Yosemite Lake located at the east end of Smith Canal, approximately 3,500 feet west of the site, and the deep-water channel of the San Joaquin River located approximately 4,500 feet south of the site The site lies at'an approximate elevation of 13 feet above MSL, topography'in the vicinity is essentially flat Regional groundwater flow paths merge toward central and western Stockton due to extensive pumping of water wells in this area (EA Engineering, Science and Technology, Inc [EA], January 1989) ' 4 A well survey (EA, 1988) was performed for the site using data from the California State Department of Water Resources (DWR) Using these data, seven water wells were; identified within 1/2 mile of the site The closest well is a domestic well located at 919 Center Street approximately 1,700 feet south (upgradient) of the Chevron station (Figure 1) ' 320133713\CLOSURE2 e c