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Florida Erosion and Sediment Control Inspector's Manual The outlets shall be designed , constructed and maintained so that sediment does not leave the trap and that erosion of the outlet does not occur. A trap may have several different outlets with each outlet conveying part of the flow based on the criteria below. The combined outlet capacity shall be sufficient for the drainage area , For example , a 12 foot (3 . 6 m) earth outlet, adequate for 2 acres (0 .8 ha) , and a 12 inch (30 cm) pipe outlet, adequate for 1 acre (0 .4 ha ) , could be used for a three acre ( 1 . 2 ha) drainage area . There are four types of outlets for sediment traps . Each sediment trap is named according ` to the type of outlet that it has . Each type has different design criteria and will be discussed separately. 1 . An Earth Outlet Sediment Trap consists of a basin formed by excavation and/ or an embankment , The trap has a discharge point over or cut into natural ground . The outlet width (feet) shall be equal to 6 times the drainage area (acres) . If an embankment is used the outlet crest shall be at least one foot (30 cm ) below the top of the embankment . The outlet shall be free of any restriction to flow , The earthen embankment shall be seeded with temporary or permanent vegetation (see Sections 6 . 65 and 6 . 66 ) within 15 days of construction . (See Plate 4 , 25a) 2 . A Pipe Outlet Sediment Trap consists of a basin formed by an embankment , or an excavation and an embankment . The outlet for the trap is though a perforated riser and a pipe through the embankment , The outlet pipe and riser shall be made of corrugated metal . The riser diameter shall be of the same or larger diameter than the pipe . The top of the embankment shall be at least 1 . 5 feet (45 cm ) above the crest of the riser. At. least the top 2/3 of the riser shall be perforated with 1 /2 inch ( 13 mm ) diameter holes spaced 8 inches (20 cm ) vertically and 10- 12 inches (25 - 30 cm) horizontally. All pipe connections shall be watertight (See Plate 4 . 25b) . Select pipe diameter from the following table : Minimum Pipe Diameter in inches (cm ) Maximum Drainage Area in acres (ha) 12 (30 cm ) 1 (0 .4 ha) 18 (45 cm ) 2 (0 . 8 ha) 21 (53 cm) 3 ( 1 .2 ha) 24 (60 cm ) 4 ( 1 . 6 ha) .� 30 (75 cm) 5 (2 .0 ha) 3 . A Stone Outlet Sediment Trap consists of a basin formed by an embankment or excavation and an embankment, The outlet for the sediment trap shall consist of a crushed stone section of the embankment located at the low point in the basin . The minimum length of the outlet shall be 6 feet times the acreage of the drainage area (4 .5 m times hectares) . The crest of the outlet must be at least 1 foot (30 cm) below the top of the embankment, to insure that the flow will travel over the stone and not the embank- ment. The outlet shall be constructed of FDOT No . 1 size crushed stone . (See Plate 4 . 25c) A very temporary alternate trap can be constructed from straw bales with a stone outlet . (See Plate 4 . 25d ) Straw bales shall be installed per Section 4 . 05 STRAW BALE BARRIER ( ES BMP 1 . 05 ) . 4 . A Storm Inlet Sediment Trap consists of a basin formed by excavation or natural 4-74