1502 WALL ST IMAGINE CHILDRENS MUSEUM 2022-08-25

Table 11-3.10: Storm Drain Inlet Protection Type of Inlet Pro- Emergency Applicable for tection Overflow Paved/ Earthen Sur- Conditions of Use faces Drop Inlet Protection Excavated drop Yes,temporary Applicable for heavy flows. Easy inlet protection flooding may Earthen to maintain. Large area requirement: occur 30'x30'/acre Block and gravel Applicable for heavy concentrated flows. drop inlet pro- Yes Paved or Earthen tection Will not pond. Gravel and wire drop inlet pro- No Paved or Earthen Applicable for heavy concentrated flows. tection Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet pro- Small capacity Used for sturdy, more compact install- tection with Paved wooden weir overflow ation. Block and gravel curb inlet pro- Yes Paved Sturdy, but limited filtration. tection Culvert Inlet Protection Culvert inlet sed- N/A N/A 18 month expected life. iment trap Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet. Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include: • Provide a depth of 1-2 ft as measured from the crest of the inlet structure. . Slope sides of excavation should be no steeper than 2H:1 V. . Minimum volume of excavation is 35 cubic yards. . Shape the excavation to fit the site,with the longest dimension oriented toward the longest inflow area. . Install provisions for draining to prevent standing water. . Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume ll- Chapter 3-Page 357