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• Scope of Work: The purpose of this project is to drill five off-site geoprobe borings and, if necessary, an additional five step-out geoprobe soil bonngs and collect soil and groundwater samples from each boring j1hThe site is a 170 by 170 foot square-shaped parcel located on northeast corner of Cambridge Street and Louise Avenue in Lathrop, California, and is an operating Circle K and TOSCO service station In November 1997, Pacific Environmental Group (PEG) performed oversight and sampling during the removal of one 4,000-gallon and two 10,000-gallon underground storage tanks (UST's), product dispensers, and associated product piping from the site during facility upgrade activities Approximately 1,241 tons of hydrocarbon impacted soil from beneath the UST's and from the new tank pit excavation Additionally, approximately 17,000 gallons of hydrocarbon impacted groundwater from the new tank pit excavation Total petroleum hydrocarbons as gasoline (TPHg) were reported at concentrations ranging from 130 ppm to 5,800 ppm Methyl tert-butyl ether(MtBE) was reported in soil at concentrations ranging from 0 19 ppm to 3 6 ppm In July1998, one Geoprobe Tm boring was advanced to a depth of 40 feet below ground surface (bgs) downgradient (north) of the former UST excavation Laboratory analysis of soil reported maximum concentrations of TPHg and MtBE of 1,900 ppm (GP-I-10') and 0 31 ppm (GP-1-10'), respectively Laboratory analysis of groundwater reported concentrations of TPHg and MtBE of 52,000 ppb and 61 ppb, respectively From August through September 1998, IT Corporation (IT) dnlled and installed four groundwater monitoring wells (MW-1 through MW-4) to approximate depths of 26 to 28 feet bgs Laboratory analysis of soil reported maximum concentrations of TPHg and MtBE of 6,800 ppm (MW-3-16') and 7 2 ppm (MW-2-1 i'), respectively Laboratory analysis of groundwater reported maximum concentrations of TPHg and MtBE of 29,000 ppb (MW-1) and 4,000 ppb (MW-2), respectively On December 2000, IT drilled and installed five groundwater monitoring wells (MW-5 through MW-9) to approximate depths of 24 feet bgs Laboratory analysis of soil reported maximum concentrations of TPHg and MtBE of 473 ppm (MW-9-10') and 0 119 ppm (MW-6-20'), respectively Laboratory analysis of groundwater reported maximum concentrations of TPHg and MtBE of 72,000 ppb (MW-6) and 750 ppb (MW-6), respectively Groundwater monitoring has been performed since August 1998 Fourth Quarter 2001 groundwater monitoring reported high concentrations ( 10,000 ppb) of TPHg in wells MW-1, MW-5, MW-6, MW-7, and MW-9 The highest concentrations of benzene and MtBE were 780 ppb (MW-7) and 660 ppb (MW-6) Groundwater flow was to the northeast with a gradient of approximately 0 001 ft/ft Depth to groundwater ranged from 12 50 (MW-9) to 14 32 (MW-3) feet bgs All work for this project will be scheduled during typical daylight hours Site plan is in Attachment 1. Emergency Response: A. Injury or Illness: If an injury or illness occurs, take the following action Determine if emergency response (fire/ambulance) staff is necessary If so, dial 911 on cell phone or closest available phone, which is located in the station building If it makes sense to take an individual to the hospital, use the directions on page 2. SECOR International Incorporated 4