BMP Objective
- Sediment Trapping
- Control Type Code = 3
Description
Inlet protection consists of a variety of methods of intercepting sediment at low point inlets through the use of erosion bales, excelsior logs, synthetic triangular dikes or any other creative means to accomplish effective sediment removal. When designing inlet protection, the main idea is to filter sediment out of the system while allowing clean water to enter the storm drain and continue to the stream.
Primary Purpose/Use/Application/Suitability
Inlet protection is considered a secondary defense in site erosion control. Every inlet that is connected to a stormwater system or has an outlet that discharges to waters of the state needs effective inlet protection. Often on construction sites excelsior logs, erosion bales, and synthetic triangular traps are utilized. On existing roadways requiring modifications curb inlet protection is necessary.
Design Criteria
- Excelsior log, erosion bale, and synthetic triangular traps are all configured in a similar fashion for flared and catch basin inlets. Any of these devices must be trenched in or stapled in, as per specifications, and backfilled. Erosion bale and excelsior logs are trenched in about 6” and 3” deep, respectively, and secured with 50mm x 50mmx 900mm wooden stakes. Backfill with soil, especially on the side that will receive the bulk of the flow. The geotextile fabric underneath synthetic triangular dikes is trenched in and is attached to the ground with wire staples spaced at 6” intervals along panel lips. Stone may be placed on the apron to help hold. Attach foam dikes to ground with wire staples. NOTE: Products like silt fence, erosion bales, and excelsior logs do not allow much water to pass through and may cause water to pond and back up into surrounding areas or roadways. Rock stilling basins or rock inlet protection may be more effective at filtering out sediment and still allowing clean water to enter the inlet.
- Curb protection - Concrete blocks (8” x 8”x 16”) are placed on their sides in a single row around the perimeter of the inlet, with the ends abutting. Openings in the blocks should face outward, not upward. Place ½ x ½” wire mesh over the outside of the blocks covering the holes. Pile filter stone against the wire mesh to the top of the blocks with the base of the stone being about 18” from the blocks. Loose rocks can also be placed in burlap or geotextile bags for containment.
Maintenance Requirements
- Inspect after every significant rainfall or every 14 days. Repair damage as needed. Make sure sediment laden water is not by-passing between around or under the protection device
- Sediment should be removed when it reaches approximately ½ of the height of the inlet protection device