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0 Q ante6group 2.2 GROUNDWATER MONITORING WELL ABANDONMENTS Before pressure grouting,the drilling contractor will clear around each well to 120 percent of the original borehole diameter to a depth of 6.5 feet below ground surface(bgs) using an air-knife with a vacuum truck and/or hand-auger equipment. In addition,total depth and depth-to-water will be measured for each well and the casings checked for obstructions.The drilling contractor will use a tremie pipe and pump to backfill each monitoring well casing from the bottom up with neat cement grout mixed at a ratio of 6 to 7 gallons of water to 94-pounds of Portland Type 1/II cement. Evacuated groundwater will be collected and stored onsite for profiling. Once the well casing is full of neat cement grout,an adapter equipped with a pressure gauge will be secured atop the wellhead and a pressure of 25 pounds per square inch (psi)will be applied for a minimum of 5 minutes. For each pressure grouted well,Antea Group will record the number and weight of cement bags and the volume of water used to mix the grout,and the total volume of grout used to backfill the well.A pressure grout attempt will be considered successful if the final grout volume is within 10%of the estimated volumes calculated using the original well construction details. A summary of estimated pressure grout volumes with deviation tolerances is presented in Table 2. Following successful pressure grouting,the driller will remove the protective vaults and surrounding concrete atop each well. Each position will then have the hole around the casing expanded to at least one foot larger in diameter than the original borehole for the well to a depth of 3 feet bgs.The well casing will be cut 6-inches from the bottom of this excavated section to be removed.The grout used for pressure grouting will be allowed to spill over and fill the excavated hole to within one foot of the surface.The well boreholes will be finished at grade in a manner consistent with the surrounding material. 3.0 WASTE MANAGEMENT Soil cuttings,wastewater,and construction debris generated during well destruction activities will be contained in labeled, Department of Transportation (DOT)-approved 55-gallon drums and temporarily stored onsite pending waste characterization and profiling. Belshire Environmental Services, Inc.will transport the drums from the Site to an approved disposal facility. Following receipt,Antea Group will provide the executed disposal documents to the CVRWQCB along with a report documenting the well destruction activities. �I NOGEN® ALLIANCE us.anteagroup.com 2