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Revise3Work Plan for Additional GroundwateWhvestigation <br /> Quik Stop Market No. 132 <br /> 3555 West Hammer Lane <br /> �- Stockton,California <br /> i This location operated as an unbranded (Quik Stop Gasoline) site with gasoline being provided by <br /> different suppliers from the date the store opened in 1985 until May 1993. The store operated as <br /> an Exxon branded site with fuel being supplied exclusively through an Exxon jobber from May <br /> �- 1993 until July 1998. The site reverted to an unbranded location in July 1998. <br /> The use and occurrence of MTBE in gasoline at this location mirrors the use and occurrence of <br /> MTBE in gasoline statewide. MTBE first appeared in gasoline as an octane enhancer when lead <br /> was phased out in the late 1970s. High concentrations (11% + or -) of MTBE first occurred <br /> i around 1990 when it was added to gasoline during winter seasons to reduce CO and NOX <br /> �- emissions. <br /> OBJECTIVE <br /> V <br /> The objective of the proposed scope of work is to determine the vertical extent of petroleum <br /> hydrocarbon impacted soil and groundwater in the vicinity of the groundwater monitoring well with the <br /> �. known highest contaminant concentrations detected to date. <br /> SCOPE OF WORK <br /> The following scope of work has been proposed to meet the objective: <br /> Task 1 Obtain Boring Permit; <br /> i Task 2. Advance boring and perforin sampling and analysis;and <br /> i <br /> Task 3. Prepare a Groundwater Investigation Report. <br /> 1 <br /> L WORK DESCRIPTION <br /> Task 1. Obtain Boring Permits <br /> t" An Application for Well/Pump Permit will be completed and filed with the San Joaquin County <br /> Environmental Health Division. <br /> Task 2. Advance Boring and Perform Sampling and Analysis <br /> i In order to determine the vertical extent of petroleum hydrocarbon impacted soil and groundwater in <br /> 1 the vicinity of the groundwater monitoring well with the known highest contaminant concentrations <br /> detected to date, one boring is proposed near groundwater monitoring well MW-2 as shown on Figure <br /> 4. Results of the June 8, 1998, sampling event indicated that groundwater monitoring well MW-2 had <br /> a maximum MTBE concentration of 6,600 ug/L. Furthermore, the proposed soil boring will also be <br /> located downgradient of the existing USTs and associated pump islands. <br /> i <br /> v. The proposed boring will be completed to a maximum drilling depth of approximately 50 feet bSs� The <br /> T proposed boring may be terminated at a shallower depth if a competent fine-grained unit with a <br /> thickness of five feet or more is encountered during drilling activities. This will be done to minimize <br /> k\vwma%ad n+ tuxzkouASIwkWORULAN(cVDP )2.e 5 <br /> t. <br />