Construction site best management practices prevent erosion and sedimentation from occurring so that sediment pollution does not occur in off site waterways. Best management practices are designed to keep soil in place, filter out sediment, and to convey, and slow down the release of water to off site areas.
After you finish learning about the correct utilization of best management practices for construction, click here to see examples of non-compliant construction site practices.
Site stabilization uses straw mulch, spread at the rate of two tons/acres, seed, and tack to prevent sediment from washing off in a precipitation event. Stabilization can either be temporary or permanent. Temporary stabilization is used when the final grade is not established. If an area is not going to be worked for more than 5 days, it must be immediately stabilized.
|Erosion and sediment control matting must be used on slopes 3:1 or greater. Matting prevents rills from forming on the slopes.|
|Stabilization by way of hydro-seeding is taking place in this photo. Hydro-seeding mixes seed, and tack with water and is applied at the specified rate. A comparable method of seeding is broadcast where seed is sewn and tack is later applied. Stabilization produces vegetative growth and is the best method to prevent erosion.|
Stockpiles of soil are often stored on site while a site is being developed. Stockpiles must be protected by using perimeter controls and must be stabilized if they will not be worked within 14 days. This control keeps soil in the pile so that it will not pollute waterways.
|Silt fence is the most commonly used perimeter control. Silt fences are long sheets of woven plastic fabric that are approximately 20" above the ground and are fastened to 1.5" by 1.5" wooden stakes. The fabric must be trenched 8" into the ground and maintained at all times. Silt fences are used to prevent sediment from leaving the site and slow rainwater that flows through them.|
Silt fences must stay in place until the site is 90% green. This practice allows vegetation to be completely established prior to removal of perimeter controls.
Stone Construction Entrance
Stone construction entrances are made of 2" to 3" stone applied 6" deep and 50 feet in length over geotextile fabric. Construction entrances are located at all ingresses and egresses on sites. This control prevents sediment from being tracked onto public roads, where it will eventually runoff into waterways.
Inlet protection is a barrier or filter located at storm drain inlets. This practice is used to prevent sediment from entering the drainage system and exiting to off site waterways. Inlet protection is used until the site is completely stabilized.
Concrete Wash Out Area
Concrete wash outs are used to clean out excess concrete material from concrete trucks. Wash out areas are made from a contained areas with impermeable material. Once the concrete hardens, it will can be safely removed and disposed of. In liquid form, concrete has a high pH and will contribute to acidification of waterways.
|Sediment traps are small ponds created to slow down and store water so that sediment can settle before water leaves the site. Traps are temporary and are usually filled or converted to stormwater management facilities when the contributing drainage area has been completely stabilized.|
|This sediment trap contain baffle boards. Baffle boards are designed to increase the time water is in the trap so that sediment has a better chance to settle out. Baffle boards should always be tied into the embankment to prevent failure during a large precipitation event.|
Conveyance channels are waterways that are lined with vegetation or rock and are used to moved runoff within a site or off site. Channels along roads are common examples. Most conveyance channels should be stabilized with matting.
Outlet protection is made by placing rip-rap, which is large, angular rock, at the outlet of conveyance channels, sediment traps, or pipes. This practice slows down and spreads water out, thereby preventing erosion at the point of discharge.