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June 16, 2022 <br />91 <br /> <br />stormwater flow, the developer may consider the design flexibility provided by the variance <br />process. <br />3. Maximum use shall be made of the existing on-site natural and man-made stormwater <br />management facilities. <br />4. Storm facilities not located within a public right-of-way shall be centered within an <br />easement. <br />5. Innovative stormwater management and recharge facilities may be proposed (e.g., rooftop <br />storage, drywells, cisterns, diversion structures, aeration of lawns, holding tanks, infiltration <br />systems, stream channel storage, in line storage in storm sewers and grading patterns), <br />provided they are accompanied by detailed engineering plans and performance capabilities <br />that are acceptable to the Planning Commission. <br />6. When Final Plat applications are submitted in sections and if temporary facilities are <br />required for construction of a section, such facilities shall be included in the submitted <br />plans. In the event temporary measures cannot adequately handle the stormwater runoff, <br />the main outfall line shall be included as part of the construction of the proposed section. <br />7. Specials provisions shall be required for outfalls to rivers, county drains, and lakes; including <br />but not limited to tied joints, outfalls structure, and backup protection. <br />8. Flap gates, shear gates and pump stations shall be installed where appropriate to provide <br />flood protection. <br />9. The following principles shall be applied to the design plan and construction schedule to <br />minimize soil erosion and sedimentation using the NDDOT Erosion and Sediment Control <br />Handbook, as it presently exists or may hereafter be amended: <br />a. Stripping of vegetation, grading, or other soil disturbance shall be done in a manner <br />which will minimize soil erosion. <br />b. Whenever feasible, natural vegetation shall be retained and protected. <br />c. The extent of the disturbed area and the duration of its exposure shall be kept to a <br />minimum, within practical limits. <br />d. Temporary seeding, mulching, or other suitable stabilization measures shall be used <br />to protect exposed critical areas during construction. <br />e. Drainage provisions shall accommodate the stormwater runoff both during and <br />after construction. <br />f. Soil erosion and sedimentation facilities shall be installed prior to any on-site <br />grading. <br />(g) System Demand. <br />1. Peak rate of discharge calculations shall be used to determine the configurations and sizes <br />of pipes, channels, and other routing or flow control structures. Runoff volume calculations <br />shall be used to determine the necessity for, and sizing of, detention and retention facilities. <br />2. Stormwater management facilities shall be provided so that the peak discharge of the <br />calculated post development runoff to an adjacent property does not exceed the peak <br />discharge of the calculated pre- development runoff. <br />Runoff calculations for the pre and post development comparison shall consider three (3) <br />different storm frequencies: the two (2), ten (10) and one hundred (100) years storm <br />events.