ARCHIVED REPORTS_2010_22 - Laserfiche WebLink

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s Mr. Robert McClellan October 1 , 2010 Page 4 For the Austin Unit wells, the same drill rig will be used advance a 35-inch borehole through waste to the depths listed in Table 2. During drilling,the on-site engineer or geologist shall document the depth of the interim cover(the approximate depth is provided in Table 2). The well construction materials (pipe,perforated section, annular materials)will be the same as those used in the Forward Unit wells. The pipe sections and bottom caps will be connected using butt fusion. The Austin Unit wells will be double completion. Once the target depth is reached,the deep interval well will be installed, consisting of six-inch HDPE perforated and solid pipe placed approximately one foot above the borehole depth. Gravel will be installed to approximately four feet below the interim cover section. Approximately one foot of clean, soil-plug Geonet with heat-bonded geotextile shall be installed above the gravel. A ten-foot section of a hydrated bentonite seal shall be installed above the soil plug. The ten-foot bentonite seal must intersect the interim cover section. The shallow extraction well will be installed approximately one foot above the top of the bentonite seal. Gravel will be installed to approximately two-feet above the perforated section. On-site soil will be used to fill the borehole annulus to approximately three feet below ground surface. A two-foot bentonite seal will be installed above the soil layer, and then soil will be installed to the ground surface. During installation of the materials,the well installer shall use a weighted measuring tape to verify proper placement of the materials. Each well will be fitted with a wellhead that will be connected to a LFG lateral. The lateral will be connected to the existing on-site header, and routed to the flare for destruction. The specifications included in Attachment B detail the well header design, and lateral connections and design. The SVE wells will be installed south of the Forward unit, outside of waste. The construction personnel should verify the location of the liner/anchor trench prior to any drilling and trenching activities. At each location, a drill rig will advance an 8-inch minimum borehole to approximately 30 feet below ground surface. Once the target depth is reached, a 30-foot, 4-inch well will be constructed at each location. The well will consist of a 20-foot section of solid schedule 80 PVC and a 10-foot section of 0.010"machine-slotted PVC. Pea gravel will be installed around the slotted section,to approximately two feet above the slotted section. A bentonite chip seal shall be installed to approximately five feet above the gravel. A bentonite slurry seal shall be installed above the bentonite chip seal to approximately two feet below the ground surface. The remaining two feet will be temporarily filled with soil, and a temporary well cap will be placed on the top of the well casing. The SVE well will be connected to a subsurface lateral, approximately 2 feet below ground surface at the well location. The specifications in Attachment B detail the well lateral connections. EVALUATIONOPERATION AND The new LFG extraction wells will enhance LFG recovery within the Forward and Austin Units. The new SVE wells will be operated to collect LFG that has migrated under the Forward base liner from the Austin unit, and to prevent the outward migration of that LFG. The wells will be monitored monthly using a field meter for a period of six months to determine the levels of methane, carbon dioxide, oxygen,balance gas, and vacuum levels at each well location. The vacuum and flow at each well will be adjusted to obtain the optimum collection efficiency.