ARCHIVED REPORTS XR0002762 - Laserfiche WebLink

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1 • . 4 • r Atlantic Richfield Company(ARCO) ARCO Station #4932 16 E Harding Way,Stockton,CA January 15 2002 The test activities and findings were summarized in SECOR's report titled Interim Remediation/Multi-Phase Extraction Feasibility Test Report dated May 4, 2001 From July 9 to July 16, 2001,West Hazmat Drilling of Rancho Cordova, California drilled two soil borings and five groundwater monitoring wells at the site Soil borings SB-1 and SB-2 were drilled to 80 feet and 78 feet bgs, respectively Monitoring wells MW-5,MW-6,MW-7,MW-8, and MW-9 were installed at 40 feet bgs TPHg, benzene, and MtBE were vertically defined in soil through borings SB-1 and SB-2 TPHg and benzene concentrations have been defined to the limits of detection by wells MW-6, MW-7, and MW-8 MtBE concentrations appear to attenuate with depth near SB-1 and SB-2 Higher MtBE concentrations off-site appear to follow groundwater flow to the northeast The presence of TPHg and benzene in upgradient well MW-9 suggests an additional source(s) of petroleum hydrocarbons may be present in the area In the Td Quarter 2001, separate phase hydrocarbons (SPH) was discovered in wells SVE- 1 and MW-4 Upon discovery, SECOR notified the SJCPHS and initiated weekly SPH removal SECOR performed weekly SPH removal until the SPH was no longer present (six weeks) Currently, SPH is not present at the site however, SECOR periodically checks site wells to verify this IF SPH is rediscovered, SPH removal will be reinitiated SITE ASSESSMENT ACTIVITIES Proposed scope of work The scope of work for this site assessment will include the installation of three shallow and three deep groundwater monitoring well at the approximate locations shown on Figure 2 These groundwater monitoring wells have been proposed to delineate the lateral and vertical extent of petroleum hydrocarbons in shallow and deep groundwater at the site The specific scope of work is discussed below 0 Site Health and Safety As required by the Occupational Health and Safety Administration (OSHA) Standard"Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), SECOR will prepare a Site-Specific Health and Safety Plan prior to the commencement of fieldwork The Site-Specific Health and Safety Plan will be reviewed by the field staff and contractors before beginning field operations at the site The Site Health and Safety Plan is included as Attachment B • Shallow Monitoring Well Installation. Three 2-inch diameter groundwater monitoring wells will be installed at the locations shown on Figure 2 The wells will be installed using a 8-inch diameter hollow-stem auger rig to a WKPLAN4932—1-11-02 doe