2008-009 (5) - Laserfiche WebLink

Home Browse Search

" Chapter 4. - Best .Mana ement Practices for Erosion. and Sediment Control. Embankment Qross-Section The embankment must have aminimum top width of a feet (2 .5 m) . The side slopes must be 2 : 1 or flatter. The embankment may have a maximum height of 10 feet (3 m) if the side slopes are 2: 1 . If the side slopes are 2.5 : 1 or flatter, the embankment may have a .. maximum height of 15 feet (4.5 m) . Soillway Desion The outlets for the basin may consist .of a combination of principal and emergency spillways or a principal' spillway alone. In either case, the outlet(s) must pass the peak runoff expected from the drainage area for. a 1t0 year storm without damage to the embankment of the basin . Runoff computations shall be based upon the soil cover conditions which are expected to prevail during the life of the basin . Refer to Chapter 3 of • this manual for calculation of the peak rate of- runoff, The spillways designed by the procedures contained in this BMP will not necessarily result +. in any reduction in the peak rate of runoff. If a reduction in peak runoff is needed ; the appropriate hydrographs should be generated to choose the basin and outlet sizes. n. To increase the efficiency of the basin , the spillway(s) must be designed to maintain a permanent pool of water between storm events. .. Principal Spillway The principal spillway shall consist of a solid (non-perforated) , vertical pipe or box of r corrugated metal or reinforced concrete joined by a watertight connection to a horizontal pipe (barrel) extending through the embankment and outletting beyond the downstream toe of the fill. If the principal spillway is used in conjunction with an emergency spillway, the .. ve a minimum capacity of 0 .2 cfs per acre (0 .015 m3 /sec. per ha) principal spillway shall ha of drainage area when the water surface is at the crest of the emergency spillway. If no emergency spillway is used , the principal spillway, must be designed to pass the entire w peak flow expected from a 10-year storm . . See Appendix 1 . 26A of The Florida Development Manual. for design details . w Design Elevations If the principal spillway is used together with an emergency. spillway, the crest of the principal spillway shall be a minimum of one foot (30 cm) below the crest of the emergency spillway. if no emergency spillway is used , the crest of the principal spillway shall be a minimum of 3 feet (90 cm) below the top of the embankment. (See Plate 4 .26b .) In either r case , a minimum freeboard of one foot (30 cm) shall be provided between the design high water and the top of the embankment. w 4-81