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Florida Erosion and. Sediment. Control Inspector's Manual . 4 . A Storm Inlet Sediment Trap consists of a basin formed by excavation or natural ground that discharges through an opening in a storm drain inlet structure . This opening, can either be the inlet opening or a temporary opening made by omitting bricks or blocks in the inlet. The trap shall be between 1 ' and 2' (30 - 60 cm) deep measured from the low point of the inlet. A yard drain inlet or an inlet in the median strip of a dual highway would use the inlet opening for an outlet. (See Plate 4. 25e) A curb inlet would require a temporary opening . (See Plate 4.25f) The trap should be out of the roadway to .avoid interference with construction . Placing the trap on the opposite side of the opening and diverting water from the roadway to the trap is one means of accomplishing this . 5 . Other applications Attimes a small trap may be constructed in a drainage channel using the culvert for a road crossing . Straw bales or gravel filled bags maybe used provided that there are no gaps in the installation . (See Plate 4.25g) In larger traps baffles may be required to insure adequate flow length and prevent short- circuiting : (See Plate 4 .25h) Construction Specifications 1 . The area under the embankment shall be cleared, :grubbed ; and stripped of any vegetation and root mat. To facilitate cleanout, the pool area should be cleared . 2. Fill material for the embankment shall be free of roots or otherwoody vegetation , organic material, large stones, and other objectionable material . The embankment should be compacted in 8 inch. (20 cm) layers by traversing with construction equipment. 3 . The earthen embankment shall be seeded with temporary or pe rmanent vegetation (see Sections -6 .65 and 6 . 66) within 15 days of construction . 4. Construction operations shall be carried out so that erosion and water pollution are minimized . 5 . The structure shall be removed and the area stabilized when the upslope drainage area has been stabilized : Maintenance 1 . Sediment shall be removed and the trap restored to its original dimensions when the sediment has accumulated to 112 the design volume of the trap: Sediment removed from the basin shall be deposited in a suitable area and in such a manner that it will not erode . 2 . The structure should be checked regularly to insure that it is structurally sound and has not been damaged by erosion or construction equipment. The height of the outlet should be checked to ensure that its center is at least one foot (30 cm) below the top of the embankment. 4-74