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Work Plan for Additional Assessment S E C O R ARCO Service Station 2130 Stockton, California Page 6of 15 Task 4 — Well Development The newly constructed monitoring wells will be developed a minimum of 48 hours following well construction. Development will be accomplished by alternately surging each well with a vented surge block followed by bailing to remove accumulated sediment. Final purging will be performed with either a submersible pump or bailer, and pH , temperature, and conductivity will be measured at regular intervals during purging. Development will be considered complete when either 1 ) 8 well volumes have been removed and physical- chemical parameters trends have stabilized over three consecutive measurements (<0 . 05 pH , 3% conductivity, and 10% temperature) , 2) 10 well volumes have been removed , or 3) until the well has been purged dry (if the well does not sustain flow or is slow to recover) . Task 5 — Waste Handling and Disposal All investigation derived waste (IDW), including soil cuttings and purge water from well installation and development will be stored on- site in Department of Transportation- approved 55-gallon drums and/or roll off bins pending the results of chemical analyses. Analytical results will be used for waste profiling and disposal. After profiling , IDW will be transported and disposed at an appropriate State-certified disposal facility. Task 6 — Surveying Once all proposed wells are installed, a California- licensed land surveyor will survey the location and top of casing elevation of newly installed wells relative to a known benchmark according to the North American Datum of 1983 (NAD83) and the National Geodetic Vertical Datum of 1929 (NGVD29) . The new wells will be surveyed relative to the same benchmark used for the existing wells on- site. REPORTING Upon completion of the work proposed herein , SECOR will prepare a report summarizing field activities and analytical results of the investigation and the bench scale testing. The report will be submitted to Atlantic Richfield Company and the SJCEHD and will include tabulated field , analytical , figures depicting subsurface conditions including soil and groundwater chemical analytical results; and appendices containing laboratory reports, well completion and soil boring logs, and copies of field notes and data sheets. In addition, this report will be uploaded into Geotracker. SCHEDULE SECOR and the Execution Contractor are prepared to initiate field activities upon approval of this work plan by the SJCEHD. We anticipate that field work will require approximately 12 to 16 weeks to complete, following the receipt of valid well installation permits from San Joaquin County. If off-site access is required due to alternate proposed locations, field work will begin following the receipt of executed access agreements between the affected property owners and ARCO .