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Mr. Gabriel Gonzalez, EHS June 19, 2015 Page 2 of 4 The construction details for the eight site groundwater monitoring wells are summarized in the following table: WELL BORING BORING WELL WELL SCREEN FILTER BENTONITE CEMENT ID DEPTH DIAMETER DEPTH DIAMETER INTERVAL PACK SEAL SEAL MW-1 65' 8" 65' 2" 45-65' 43-65' 41-43' 0-41' MW-2 65' 8" 65' 2" 45-65' 43-65' 41113' 0-41' MW-3 65' 8" 65' 2" 45-65' 43-65' 41-43' 0-41' MW-4 60' 8" 60' 2" 40-60' 38-60' 33-38' 0-33' MW-5 60' 8" 60' 2" 40-60' 38-60' 35-38' 0-35' MW-6 60' 8" 60' 2" 40-60' 3"0' 33-38' 0-33' MW-7 60' 8" 60' 2" 40-60' 38-60' 35-38' 0-35' MW-8 60' 8" 60' 2- 40-60' 38-60' 35-38' 0-35' As directed by EHD in their letter dated April 16, 2015, monitoring wells with concentrations of petroleum compounds above laboratory reporting limits in the most recent groundwater sampling event must be destroyed by the over-drill method. Monitoring wells without concentrations of any petroleum compounds above laboratory reporting limits in the most recent groundwater sampling event can be destroyed by the pressure grout method. As such, the driller will destroy MW-1 through MW-6 by the over-drill method, and MW-7 and MW-8 by the pressure grout method. Prior to destroying all of the wells, the driller will measure the total depths of the wells to ensure that the well casings remain clear and intact. The driller will destroy six site monitoring wells (MW-1 through MW-6) by the over-drill method. The driller will first remove the street boxes, and drill out the wells with 8-inch diameter hollow- stem augers, equal in diameter to the well borings. Drilling will continue until the total depths of the wells are reached and all well screens,well casings, filter packs, and annular seal materials have been removed. Following the over-drilling of the wells, the driller will install a tremie pipe to within 5 feet of the total depths of the cleared well boreholes, and will fill the boreholes with neat cement grout through the tremie pipe to within three to five feet below surface grade. The driller will complete the upper three to five feet of the borings with compacted soil. The driller will destroy two site monitoring wells (MW-7 and MW-8) by the pressure grout method. First, the driller will expand the diameters of the upper three feet of the well borings to at least 20- inches (i.e., 12 inches larger than the 8-inch diameters of the well borings). While leaving the well casings in place, the driller will then completely fill the well casings with neat cement through a tremie pipe installed to the bottoms of the casings. The driller will then apply 25 pounds per square inch(psi)of pressure for ten minutes on each of the cement-filled wells. If the well casings are unable to withstand this pressure, they will be destroyed by the over-drill method. Following pressure grouting, the driller will cut-off and remove the well casings six-inches above the bottoms of the excavations (i.e., 2.5 feet below surface grade). Immediately after the wells are destroyed, the driller will then place neat cement in one continuous pour into the excavations to create a"cap" with a vertical thickness of one foot(between two and three feet below surface grade). The driller will complete the upper two feet of the borings with compacted soil.