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• The existing inlet concrete headwall at the 120-inch diameter CMP will be modified to allow for <br /> installation of the culvert inlet cutoff structure. The inlet concrete headwall will be modified by <br /> removing the headwall portions as depicted on Drawing No. 6-807-1005, including any <br /> surrounding vegetation to perform the work. <br /> • Drawings depicting the Secondary Containment Concrete Cutoff Structure layout,foundation <br /> details, concrete specifications, dimensions, reinforcement plan, and tests/inspection <br /> requirements are contained in Drawing Nos. 6-807-00112 through 6-807-00117. <br /> • Note that the design and construction plans specify a 12-inch diameter pipe penetration (18- <br /> inches long, with a blind flange on the interior of the cutoff structure)through the front of the <br /> containment cutoff wall. The purpose of this pipe is to allow for potential pumping of the <br /> collection pool for sediment removal or other maintenance activities. <br /> Pump Station <br /> • An 18-inch diameter corrugated HDPE (CHDPE) intake pipe will run from the collection pool (at <br /> elevation 10,357 ft amsl)to the wet well. This pipe will supply the wet well and is depicted in detail <br /> in plan and cross-section on Drawing No. 6-807-00104. <br /> • A deicing agitator will be installed in the center of the containment pool with mooring cables and be <br /> electrically powered. The agitator is depicted on the plan view on Drawing No. 6-807-00104. <br /> • The pump station will generally consist of a wet well (fed by the 18-inch diameter CHDPE pipe), a set <br /> of submersible pumps (described more fully in the Hydrology Analysis above), an outlet piping <br /> system and a pump building. The pump station location Is depicted on Drawing No. 6-807-00104. <br /> Dimensions, materials and detailed plan and cross-section views are depicted on Drawing No. 6-807- <br /> 00109. <br /> • The 2-inch (-50 gpm with VFD) and 3-inch (-200 gpm) submersible pumps will feed into a manifold <br /> on a 6-inch diameter pipe inside the pump building. This will transition to an 8-inch diameter HDPE <br /> buried pipeline just outside the pump building. The pump lines within the wet well will be fitted <br /> with check valves to prevent the system from unintentionally'backdraining'from the discharge end <br /> (at the Mayflower Clear Pond) back into the wet well. The discharge system will be fitted with a <br /> separate 3-inch diameter drain back to the wet well to allow for manual pipeline draining when the <br /> 3-inch diameter gate valve is opened. <br /> • The system will be fitted with a pressure gage and flow meter to track how much water is pumped <br /> back to the Mayflower Clear Pond. The pump building will also be fitted with a jib crane for pump <br /> maintenance. Miscellaneous details such as wet well grating and pump building safety bollards are <br /> depicted on Drawing No. 6-807-00110. <br /> • The normal water level in the containment pool and wet well will be maintained at approximately <br /> 10,359 ft amsl. <br /> • The 8-inch diameter HDPE discharge pipe will convey water from the wet well to the Mayflower <br /> Clear Pond. The plan and profile of this line is depicted on Drawing No. 6-807-00106. Details of the <br /> pipeline trench and the discharge point are depicted on Drawing No. 6-807-00108. <br /> Construction Schedule <br /> • A construction schedule is attached in accordance with Rule 6.4.21(15). The schedule is based on <br /> task lengths (in case start date gets delayed and renders subsequent dates inaccurate). Upon TR <br />