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<br />Hydraulics <br />Culverts <br />Culverts shall be analyzed using methodologies used in the preparation of the municipal stormwater <br />management plans. <br /> <br />Anti-Seepage Collars <br />It is recommended that anti-seepage collars be used on culverts under public streets when there is: <br /> <br />· Water and ponding structures with a pool depth of two feet and a 2-day duration. <br /> <br />· 250-acre watershed or more. <br /> <br />. Design head of 10 feet or more. <br /> <br />The collars shall be installed so as to increase the creep distance or seepage line along conduit by 15 <br />percent. <br /> <br />Emergency Overflows <br />Existing, natural occurring or man-made emergency overflow hydraulics from detention areas shall <br />be calculated and be analyzed as part of the design of the structure. <br /> <br />Minimum Building Elevation <br />The minimum building elevation shall be two (2) feet above the 100-year level. The 100-year level <br />shall be on the highest lOO-year level resulting from a single event analysis, a multiple day runoff <br />event analysis, or the critical event analysis. The starting elevation of the pond/waterbody prior to the <br />runoff event shall be equal to the invert elevation of the formal outlet. The LRR WMO will complete <br />its review using a "critical event analysis." <br /> <br />In addition to evaluating the I OO-year level, an effort shall be made to identify and evaluate the <br />location( s) of an overflow other than the formal outlet discussed above. The evaluation shall include <br />a comparison of the overflow elevation to minimum building elevations and an evaluation ofthe risk <br />for plugging of the formal outlet. <br /> <br />Infiltration/evaporation analysis is accepted as a management tool for controlling volumes of runoff <br />generated from urbanizing areas and water quality treatment. Infiltration is an essential means in <br />meeting the municipal nondegradation requirements. <br /> <br />For Areas without Formal Outlets (i.e., Landlocked Areas) <br />Wherever practical, the construction of a low level outlet is recommended. Where the construction of <br />a low level outlet is not practical, the following shall apply: <br /> <br />Water Management Plan <br />P:IMpls123 MNI02123020471WorkFiles\3rd Gen WMPILRRWMO_3rd Gen WMP _July 2009_Draft.doc <br /> <br />80 <br />