Sediment control measures
Sediment Basins
A suitably located temporary or permanent earthen embankment, barrier, dam, or excavated basin designed to capture sediment.
To retain sediment on the construction site and prevent sedimentation in offsite water bodies, properties, etc.
Used where erosion control measures are not adequate to prevent offside sedimentation on sites with disturbed area of 5 acres or more.
Hazard class must be considered so failure does not jeopardize property or lives. The location of the basin must be able to collect all of the site runoff.
Drainage area is between 5 and 150 acres. The flow length through the basin length to width ratio should be 2:1 or greater. Sediment basin must be sized to handle 3600 cu. ft. of storage per acre of land drained.
Temporary Sediment Trap
A small temporary ponding basin formed by construction an embankment across a drainage swale, by excavating a pond or by rock fill.
Detain sediment-laden runoff from small, disturbed areas long enough to allow the majority of the sediment to settle out.
Used at the outlet of drains, diversions, channels, and other runoff conveyances. May be installed during early site development.
Access to trap must be maintained to periodically remove sediment for proper disposal., Structure life is limited to 18 months.
Used for drainage areas of 5 acres or less. Minimum storage area is fixed to meet 80% removal efficiency. Side slopes of the excavated trap should be 2:1 or flatter. Maximum height is 5 ft.
Silt Fence
Sediment barrier consisting of synthetic filter fabric stretched across supporting posts with the bottom of the fabric being entrenched.
To catch and hold small mounts of sediment from disturbed areas by reducing the velocity of sheet flow to allow sediment deposition.
Used below small, disturbed areas less that 1.4-acre per 100 ft. of fence, and where runoff can be stored behind the fence without damaging the fence or the area behind it.
Should be located only where shallow pools can be formed. Sediment deposition should be periodically removed at 1/2 capacity of silt fence and properly disposed of. Turnouts or breaks in the fence should be used to minimize drainage areas.
Fence should be stable for the 10-year storm. The slope should be no longer than 100 ft. and have a gradient of 2:1 or flatter. The minimum fabric height is 18 inches while the maximum is 24 inches. Maximum post spacing is 6 ft.
Rock Ditch Checks
Small permanent/temporary dams constructed across a swale or drainage ditch to reduce the velocity of concentrated storm flows.
Used to reduce erosion of the channel by restricting the velocity of flow in the channel. Not to be installed in live channels or waters.
Used as a temporary or emergency measure to limit erosion by reducing flow in a small open channel.
Ditch checks should not be used in live streams but are intended for temporary ditches and swales. Check in grass channels may kill the vegetation. Ditch checks shall be promptly removed when their useful life has been completed.
Drainage area should not exceed 10 acres. The maximum height is 2 ft. at the center. The center should be at least 6 inches lower than the outer edges. The maximum spacing between checks should be such that the toe of the upstream check is at the same elevation as the top of the downstream check. The maximum size of stone used should be no greater than 8 inches in diameter.
Stabilized Construction Entrance
A gravel driveway or pad located at a point where vehicles enter and exit a construction site.
To reduce the amount of mud and soil transported onto public roads by traffic leaving the construction site.
Used wherever traffic leaves a construction site and enters a public right-of-way, street, alley, sidewalk, parking lot, or other paved area.
Construction plans should limit all traffic to properly constructed entrances and exits.
Stone should be KTC #3 or larger. Pad thickness has a 6-inch minimum with a required geotextile fabric underlying the stone. The minimum width of the entrance shall be 24 ft. while the minimum length shall be 100 ft.
Storm Drain Inlet Filters
A sediment filter or an excavated impounding area surrounding a storm drain inlet.
To retain sediment on the construction site by slowing and filtering runoff before it enters the storm drainage system.
Used where storm drain inlets are to be made operational before permanent stabilization of the disturbed area occurs.
Must not be used near the edge of fill material and must not divert water over cut or fill slopes.
- Filter fabric inlet protection
- Stone bag inlet protection
- Block and gravel drop inlet protection
- Gravel and wire mesh inlet sediment filter
- Drop in box/filter
The drainage area must be no greater than 1 acre with a slope less than 5%.
Vegetated Filter Strips
Zones of vegetation through which sediment and pollutant-laden runoff are directed before being discharged to a concentrated flow channel.
Filter strips are used to remove sediment from overland sheet flow but are not effective in removing sediment from concentrated flows.
Used where runoff from land undergoing development needs to be filtered to reduce sediment damage to adjacent properties, streams, or sinkholes.
Effectiveness can vary depending on vegetation, height, type, and density, season of the year, soil eroded particle size characteristics, size of disturbed area, and site topography.
The general design criteria are:
- Minimum Width: 15 feet
- Minimum Ground Slope: 1%
- Maximum Ground Slope: 10%