REVISION - 5/22/2009, 7:59:00 AM-MR1

Home Browse Search

4FrTmN FF.. ,FnIMFNTCONTRU SC 5: SEDIMENT TRAP • Half of this volume shall be in the form of wet storage or a permanent pool. The other half shall be in the form of dry storage. When possible, the wet storage volume should be contained within the excavated port;,on of the trap. • The wet volume is measured from the low point in the trap to the base of the embankment. • The drv volume should be measured from the base of the embankment to the crest of the spillway. • The depth within the wet storage area should be a maximum of 4 feet, although 2 feet is preferred. Shape • A rectangular and shallow trap, with a length-to-width ratio of 2A or greater is recommended. Embankment • Maximum embankment height shall be 5 feet measured on the downstream side. The minimum top embankment width shall be 4 feet. Side slopes for the embankment and the excavated areas shall be 21 or flatter. • Fill material for the embankment shall be free of roots or other vegetation, organic material, large stones, and other objectionable material. Spillway • The spillway shall consist of a stone section in the embankment forme 3 by a combination coarse aggregate/riprap to provide for filtering/ detention capability. Riprap shall be 4- to 8-inch rock, while the coarse aggregate shall be 1/2 to 3/4 inches. The spillway crest shall be at least 1 foot below the top of the embankment. Installation • Sediment traps, along with other perimeter controls, shall be installed before any land disturbance takes place in the drainage area. • The area under the embankment shall be cleared. and stripped of any vegetation and roots. • A geotextile should be placed at the stone-soil interface to act as a separator. Maintenance and Inspection Sediment shall be removed from the trap when the wet storage volume is reduced by half. Sediments removed must be properly disposed. • 3-57