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y Ai Atlantic Richfield Company • 2 ARCO 4932,16 East Harding Way,Stockton,CA December 14,2000 activities Confirmation soil samples collected after over-excavation indicated that petroleum hydrocarbons had impacted the soil beneath the site In August 2000, three groundwater monitoring wells (MW-1, MW-2, and MW-3), one groundwater monitonng/vapor extraction well (MW-4), and one vapor extraction well (SVE-1) were completed at the site by West Hazmat Drilling of Rancho Cordova, California Groundwater monitoring wells MW-1, MW-2, and MW-3 were set at approximately 40 feet bgs and screened from 10 to 40 feet Groundwater monitoring/vapor extraction well (MW-4) was set at approximately 40 feet bgs and screened from 5 to 40 feet Vapor extraction well SVE-1 was set at approximately 30 feet bgs and screened from 5 to 30 feet Boring logs showing well completion details are available in SECOR's Site Assessment Report, dated November 6, 2000 Initial groundwater samples collected from the groundwater monitoring wells in September 2000 were reported to contain TPHg, benzene, and MtBE at maximum concentrations of 166,000 ppb, 10,500 ppb, and 708,000 ppb, respectively (all from MW-4) Quarterly monitoring and collection of groundwater samples and analytical data from the monitoring wells at the site is ongoing Based on September 2000 groundwater elevation data, depth to groundwater at the site ranged from 26 45 feet bgs to 27 60 feet bgs Groundwater flow is estimated to be towards the northeast at a gradient of 0 005 PROPOSED SCOPE OF WORK Task I —Pre-Test Activities Prior to initiation of field activities, SECOR will obtain any necessary permits for performance of this DPE pilot test from San Joaquin Valley Air Pollution Control District SECOR has also prepared a site-specific Health and Safety Plan (HASP) The HASP is required by the Occupational Health and Safety Administration (OSHA) "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) The Health and Safety Plan will be reviewed by the field staff and contractors prior to beginning field operations at the site and is included as Attachment B Task 2—Interim Remediation/Feasibility Testing Interim remediation/feasibility testing is planned to last five days and will be conducted using a trailer-mounted DPE system capable of generating flow rates up to 300 cubic feet per minute (cfm) and vacuums up to 29 inches of mercury (in/Hg) SECOR can connect the DPE system to one well at a time, or to multiple wells, and can extract soil 10 vapor and liquid simultaneously from the well(s) A thermal oxidizer is used to treat extracted soil vapors in accordance with permit conditions established by the local air quality management district The period of extraction from a given well is determined 077 43030 1501pilottest-dnalphase