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CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />1 <br />1 <br />k <br />k <br />L <br />I1 <br />0 <br />P <br />P <br />3. Clean energy dissipater if sediment builds up. <br />3.3.11 BMP C220: Storm Drain Inlet Protection <br />Purpose is to prevent coarse sediment from entering drainage systems prior to permanent stabilization of <br />the disturbed area. <br />Conditions of Use <br />For use where storm drain inlets are to be made operational before permanent stabilization of the <br />disturbed drainage area. Protection should be provided for all storm drain inlets downslope and within <br />500 feet of a disturbed or construction area, unless the runoff that enters the catch basin will be conveyed <br />to a sediment pond or trap. Inlet protection may be used anywhere to protect the drainage system. It is <br />likely that the drainage system will still require cleaning. <br />Table 3.9 lists several options for inlet protection. All of the methods for storm drain inlet protection are <br />prone to plugging and require a high frequency of maintenance. Drainage areas should be limited to <br />1 acre or less. Emergency overflows may be required where stormwater ponding would cause a hazard. <br />If an emergency overflow is provided, additional end -of -pipe treatment may be required. <br />Table 3.9 Storm Drain Inlet Protection <br />Applicable for <br />Emergency <br />Paved/Earthen <br />Type of Inlet Protection <br />Overflow <br />Surfaces <br />Conditions of Use <br />Drop Inlet Protection <br />Excavated drop inlet <br />Yes, temporary <br />Earthen <br />Applicable for heavy flows. Easy <br />protection <br />flooding will <br />to maintain. Large area <br />occur <br />Requirement: 30 x 30-feet/acre <br />Block and gravel drop inlet <br />Yes <br />Paved or <br />Applicable for heavy concentrated <br />protection <br />Earthen <br />flows. Will not pond. <br />Gravel and wire drop inlet <br />No <br />Applicable for heavy concentrated <br />protection <br />flows. Will pond. Can withstand <br />traffic. <br />Catch basin filters <br />Yes <br />Paved or <br />Frequent maintenance required. <br />Earthen <br />Curb Inlet Protection <br />Curb inlet protection with a <br />Small capacity <br />Paved <br />Used for sturdy, more compact <br />wooden weir <br />overflow <br />installation. <br />Block and gravel curb inlet <br />Yes <br />Paved <br />Sturdy, but limited filtration. <br />protection <br />Culvert Inlet Protection <br />Culvert inlet sediment trap <br />18 month expected life. <br />Design and Installation Specifications <br />1. Excavated Drop Inlet Protection — An excavated impoundment around the storm drain. Sediment <br />settles out of the stormwater prior to entering the storm drain. <br />a. Depth 1 to 2 feet as measured from the crest of the inlet structure <br />b. Side slopes of excavation no steeper than 2:1 <br />Volume ll — Construction Stormwater Pollution Prevention <br />3-49 <br />