ARCHIVED REPORTS_XR0005743 - Laserfiche WebLink

Home Browse Search

Atlantic Richfield Company 2 ARCO 595,6100 North Highway 99,Stockton,CA December 11,2001 Ethyl tert-but 1 ether ( tBE)� tert-amyl methyl ether(TAME), 1> 2-dichloroethane (1,2- DCA), and ethylene dibromide (EDB) were reported as nondetectable in the samples Approximately 189 tons of soil generated during the removal of the underground facilities and the trenching for new piping were disposed of at BFI Landfill in Livermore, ' California Mstoncal maps and soil analysis data are included in Attachment B From June 1 to June 6, 2000, four groundwater monitoring wells (MW-1 through Mw- 4) and three soil borings (B-1, B-2, and B-3) were completed at the site by West Hazmat Drilling of Rancho Cordova, California, under the direction of SECOR staff Site assessment activities showed that petroleum hydrocarbons had impacted the soil and ' groundwater beneath the site Historical soil sample data is included in Attachment B, and historical groundwater data in Tables 1 and 2 ' Quarterly groundwater monitoring is currently ongoing Groundwater flow direction is generally to the west and northwest ' ASSESSMENT ACTIVITIES AND FINDINGS Prior to beginning site assessment activities, SECOR secured well permits from SJCEHD t Caltrans approved an encroachment permit for access to the offsite well MW-6, and San Joaquin County Public Works approved an encroachment permit for wells MW-5 and MW- 7 From July 17 to July 24, 2001, three groundwater monitoring wells (MW-5 through MW-7) and two soil borings (PSB-1 and PSB-2) were completed Groundwater monitoring wells MW-5, MW-6, and MW-7 were set at 70 feet below ground surface (bgs) and screened from 50 to 70 feet bgs Borings PSB-1 and PSB-2 were drilled to a total depth of 100 feet bgs, and backfilled with grout upon completion Well completion details are included as Table 3 Boring logs are included as Attachment C Field procedures are ' described in Attachment D Subsurface Conditions ' Soil encountered during drilling activities generally consisted of interbedded layers of sands, silts, and clays The most prominent soil types beneath the site appear to be sandy silts and silty sands First groundwater was encountered at approximately 50 to 64 feet ' bgs Groundwater levels stabilized at approximately 60 feet bgs The groundwater appears to be under unconfined conditions within sand to silty clay Geologic cross- sections are included as Figures 3 and 4 Soil Sampling and Analysis Borings PSB-I and PSB-2 were continuously cored from 50 to 100 feet bgs to evaluate changes in soil stratigraphy Soil samples from MW-5, MW-6, and MW-7 were collected at 5-foot intervals Selected samples were analyzed for TPHg by EPA Method ' 8015, benzene, toluene, ethylbenzene, xylenes (BTEX), and MtBE by EPA Method 8020, and fuel oxygenates, including MtBE, TAME,DIPE, ELBE, TBA, 1,2 DCA, and ' EDB by EPA Method 8260 ' 077 43029 330/well msta112 doe