ARCHIVED REPORTS_XR0003103 - Laserfiche WebLink

Home Browse Search

' Mr.Marty Hartzell February 16,2001 Page 3 of 8 freshwater habitat, wildlife, fish migration, and fish spawning (CRWQCB Water Quality Control ' Plan, 1994). The existing and potential uses of groundwater in the area include irrigation, private and municipal water supply, stock watering, process water, and service supply (CRWQCB Water Quality Control Plan, 1994). The "older alluvium" is the most extensively developed geologic unit in the area and hosts both unconfined and confined zones. The unconsolidated, mostly ' coarse grained nature of the aquifer material results in high well yields. Specific capacities of wells completed in the older alluvium average 42 GPM/ft (USGS Professional Paper 1401-D, 1989). Regional groundwater flow in the site area is generally in a northwesterly direction, toward the San Joaquin River Delta and a regional groundwater depression centered about 4 miles east of Stockton (San Joaquin County Flood Control and Water Conservation District, Fall 1998). City of Escalon personnel also indicated that groundwater flows northwest. ' Published data from the San Joaquin Flood Control and Water Conservation District (Fall 1998) indicate that the current depth to groundwater in the vicinity the site is approximately 65 feet below grade. ' According to City of Escalon personnel, the nearest active water supply well is located approximately 1,200 feet south (generally upgradient) of the subject site. A water supply well has reportedly been recently installed approximately 3,000 feet northwest (downgradient) of the subject site. ' 3.0 INVESTIGATIVE PROCEDURES On November 20 and 21, 2000 four soil borings were advanced at the site to investigate the lateral and vertical extent of hydrocarbon contamination. Soil boring locations are shown on Figure 2. ' Spectrum advanced the borings under the supervision of field geologist Sean Garvey and project manager John Lane, a California Registered Geologist. Boring SB 1 was advanced to a depth of approximately 60 feet below ground surface(bgs) within the former 1,000-gallon gasoline tank pit. ' Perimeter borings SB2, SB3 and S134 were advanced to depths of approximately 50, 55 and 60 feet bgs, respectively (Figure 2). Spectrum utilized a CME-85 drilling rig equipped with hollow stem augers to advance the borings and collect soil samples. Soil samples were collected using an 18- inch long core sampler lined with new 2-inch diameter brass sleeves, affording soil identification and subjective evaluation for contamination. A flame ionization detector (FID) was used to ' monitor for the presence of volatile organic compounds in the soil. Subsequent to collection, the samples were sealed, labeled, and immediately placed in an iced cooler and transported to Argon Labs under chain-of-custody protocol. Soil samples were selected for analysis based on observations and field screening results. ' datalgrounzelgonzaleslsunuptdoc