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Cleansing/rinsing of the sampling equipment will be performed prior to the collection of each soil I sample by washing the equipment with an AlconoxTM solution followed by subsequent tap water and deionized water rinses. Soil cuttings and rinseate generated during the drilling activities will be temporarily stored onsite in labeled, Department of Transportation-approved, 55-gallon drums pending the results of the laboratory i analyses and subsequent disposal following regulatory protocol. r— A permanent reference mark will be made on the top of each well casing, and a California-licensed r land surveyor will survey the top of casing elevation at the reference mark. I No sooner than 48 hours after completing the grout sealing of the new wells, each new well will be developed to remove sediment that may have infiltrated the wells during construction. The well development will be performed using a combination of bailing and pumping with a portable electric i submersible pump. Measurements of pH, conductivity, temperature and turbidity will be periodically recorded during the development activities and noted on a field log. Development will continue until turbidity measurements are less than 5 nephelometric turbidity units or 10 casing volumes have been removed from the well, whichever is sooner. The purged water generated from well development will be retained in 55-gallon drums and disposed of as previously described. Groundwater samples will be collected from the four new groundwater monitoring wells during the subsequent groundwater monitoring event. 3.2.2 Well Destruction Activities Groundwater monitoring wells MW-1, MW-3 through MW-6 and MW-12 will be destroyed by pressure-grouting the casing and annulus to the total depth of each well. The sealing material will consist of neat cement with a 3% mixture of bentonite. The cement will be introduced with a tremie i pipe extending to the bottom of each monitoring well. After the wells are grouted to a depth of approximately 3 feet below the ground surface, we will utilize a backhoe to remove the upper three I feet of casing and the soil from an area 12 inches larger than the original 10-inch borehole. Once the soil has been removed, additional grout will be added to the casing and allowed to "mushroom" over the casing and into the surrounding 3-foot-deep excavation. The excavation will then be backfilled with concrete to the ground surface. Black dye will be applied to the concrete at the ground surface to match the surrounding asphalt. The excavated soil will be contained in labeled Department of Transportation-approved, 55-gallon drums and stored temporarily onsite until transportation to an appropriate disposal facility can be arranged. The 3-foot sections of well casing will be placed in a waste receptacle. i Project No.Stockton Yard,Task Order No.45 6 Caltrans Contract 03A1368 EA No. 10-ON8300 4 Project No.S9300-06-45 January 28,2009 i