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A ECOM imagined. I�'� t]elivered. top of the well casing for any hanging lines, shining a flashlight into the open hole, and lowering a measuring tool to the total depth of the well. If obstructions are seen and/or felt while lowering the measuring tool, they will be removed by either removing the hanging lines or fishing the obstruction out with a three-pronged hook or similar tool. Each well will be over-drilled to the total depth of the original boring to remove the well casing and annular material using a Hollow Stem Auger(8 inch outside diameter).After all casing has been removed, the auger will be rotated at the bottom of the boring to remove all well construction debris to create a satisfactory seal between the new grout and the boring wall. Each boring will then be backfilled with neat cement grout, (i.e., Portland Cement-Type 1/II 3-5% bentonite) emplaced via tremie pipe.As the grout is pumped, the tremie pipe will be positioned so it is below the top of the grout rising in the boring. The bottom of the auger stem will always be positioned below the top of the grout seal to prevent possible caving of the sides of the boring. The volume of neat cement grout added to the well will, at minimum, be equal to the calculated amount shown for each well in Table 2. Any monitoring well water rising to the surface during grout placement will be contained and placed in Department of Transportation (DOT) approved 55-gallon drums Each well head box will be removed, and the former well vault cavity will be filled with a continuation of grout to form a"mushroom"cap at the top of the drilled out well. The uppermost few inches will be topped off with native soil to match the surrounding surface. All well destruction locations will be recorded using a hand-held Trimble-brand (or equivalent) global positioning system unit. In accordance with California Water Code Section 13751, the licensed C-57 water-well drilling subcontractor will file a Well Completion Report (Well Destruction)with DWR within 60 days of the completion of the work. Investigation-Derived Waste Investigation-derived waste (IDW)will be generated during well destruction activities and will include the boring soil, well casing and annular material removed from each boring, possible monitoring well water and decontamination water. The soil will be placed in a 20-yard roll-off bin, and the water will be contained in DOT-approved 55-gallon drums. The IDW will be covered and temporarily stored at the Site pending sampling and analysis for waste profiling purposes. It is anticipated that both the soil and water will be classified as non-hazardous. Four IDW profile samples (two soil and two water)will be composited from the bin and drums and sent to Eurofins Test America Laboratory, a State of California-certified analytical laboratory in Sacramento, California, for waste profiling purposes.The IDW samples will be labeled with site-specific labels and placed under chain-of-custody in a cooler chilled with ice and shipped to the laboratory for analysis. The samples will be analyzed on a standard 10-day-turnaround time. Each soil sample will be analyzed for: • TPH-g,TPH-d, and TPH as motor oil by United States Environmental Protection Agency (EPA) Modified Method SW8015; • Volatile organic compounds (VOC) by EPA Method SW826013; and • California Title 22 Metals by EPA Method SW6010B. Each water sample will be analyzed for TPH-g and TPH-d by EPA Modified Method SW8015, and VOC's by EPA Method SW8260B. aecom.com Our Reference 60632236 3/6