The control of sedimentation from construction sites is accomplished through the utilization of a variety of erosion and sediment control Best Management Practices (BMPs). Essentially, any device, practice, or procedure that has demonstrated to effectively control either the quality and/or quantity of stormwater runoff while maintaining compatibility with the planned land used are classified as BMPs.
BMPs are mainly used to implement the goal of limiting the quantity of sediment being eroded from, andS leaving the construction site. BMPs are classified into many catergories, including Erosion Prevention,Sediment Control, Runoff Control, Low Impact Development, and Structural Water Quality Control.
Choosing the correct BMPs for your site is crucial and should be left to design professionals. Incorrect usage and/or installation of BMPs may allow for the release of more sediment then what may occur in their absence. Please consult SC DHEC's BMP Handbookfor more information.
SC DHEC's Stormwater BMP Handbook
Sediment is not the sole culprit of what has caused the degradation of South Carolina's waterways. Other polluntants commonly found in surface water runoff, such as oils and fertilizer, hace also contributed to this problem. Fortunately, sediment and other polluntants can be controlled through various Sediment Control BMPs .
All stormwater management plans must should that polluted runoff is reduced to best extent practicable.
Stormwater Pollution Prevention Plans are required to be submitted with every request for coverage.
Low Impact Development is a concept that addresses stormwater management at its source.
Erosion Prevention BMPs
Each year, millions of tons of sediment have the potential to enter South Carolina's waterways via erosion of the land caused by surface water runoff, especially over exposed soil on construction sites. This process, unabated, will have adverse impacts to downstream waterways, not only to the water clarity and the affiliated public but also to the wildlife these waterways sustain. To counteract this possiblity, the state of South Carolina has adopted the use of various Best Management Practices (BMPs) that excel at prevention of erosion, reducing the amount of sediment that finds it's way into South Carolina's waterways. This group of BMPs is called Erosion Prevention Measures.
Erosion Prevention Measures are a specific set of approved BMPs that are used during and after construction site preparation in order to safely convey clean water to storm drains or towards downstream waterways. Such measures include but are not limited to: phasing and construction sequencing, surface roughening, temporary seeding, mulching, erosion control blankets, and reinforcement matting. Each of these measures is discussed in detail in the South Carolina DHEC's Stormwater Management BMP Handbook.
Sediment is not the sole culprit of what has caused the degradation of South Carolina's waterways. Other polluntants commonly found in surface water runoff, such as oils and fertilizer, hace also contributed to this problem. Fortunately, sediment and other polluntants can be controlled through various Sedimont Control BMPs.
Sediment Control BMPs
Similar to the Erosion Prevention Measures , Sediment Control BMPs is a set of approved BMPs that are used to reduce/elimnate the amount of sediment and other pollutants that are found in surface water runoff.
Uncontrolled runoff from construction sites are a cause for concern because of the devastating effects that sedimentation can cause on downstream waterways, particularly small streams. Numerous studies have shown that the amount of sediment transported by surface water runoff, stormwater, from construction sites with no sediment controls is significantly greater than from sites with approved BMPs designed for sediment control.
In addition to sediment, construction activities yield pollutants such as pesticides, petroleum products, construction chemicals, solvents, asphalts, and acids that can contaminate surface water runoff. During storms, construction sites may be the source of sediment-laden runoff, which can overwhelm a small stream channel's capacity, resulting in streambed scour, streambank erosion, and destruction of near stream vegetative cover. Where left uncontrolled, sediment-laden runoff has been shown to result in the loss of in-stream habitats for fish and other aquatic species, an increased difficulty in filtering drinking water, the loss of drinking water reservoir storage capacity, and negative impacts on the navigational capacity of waterways.
Polluted stormwater from construction sites often flows to MS4s and ultimately is discharged into local rivers and streams. Sediment is usually the main pollutant of concern. Sediment runoff rates from construction sites are typically 10 to 20 times greater than those of agricultural lands, and 1,000 to 2,000 times greater than those of forest lands. During a short period of time, construction sites can contribute more sediment to streams than can be deposited naturally over several decades. The resulting siltation, and the contribution of other pollutants from construction sites, can cause physical, chemical, and biological harm to our nation's waters. For example, excess sediment can quickly fill rivers and lakes, requiring dredging and destroying aquatic habitats.
There are numerous methods available to assist in the control of sediment, all of which are discussed in detail in the South Carolina DHEC's Stormwater Management BMP Handbook.
Runoff Control BMPs
Stormwater runoff is rainfall or snowmelt that runs off the ground or impervious surfaces such as buildings, roads, and parkways into natural or manmade drainage ways. Improperly controlled runoff can cause serious problems and downstream impacts, especially in areas where urbanization occurs. During urbanization and most land disturbing activities the percentage of impervious surfaces increases directly causing the percentage of runoff to increase.This increased runoff uncontrolled can damage roads, utilities lines, bridges, flood homes and yards, and erode stream banks adversely effecting the natural flora and fauna of the associated waterways. The following runoff control BMPs can be used to reduce these effects from increased runoff: pipe slope drains, runoff diversion measures, level spreaders, subsurface drains, and construction de-watering.More information on Runoff Control BMPs can be found in the South Carolina DHEC's Stormwater Management BMP Handbook.
Structural Water Quality Control BMPs
Structural Water Quality Control BMPs are recommended for use with a wide variety of land uses and development types. These controls have demonstrated the ability to effectively treat runoff volume to reduce the amounts of pollutants discharged to downstream waterways. Examples of these BMPs are wet detention ponds, dry detention ponds, underground detention systems, stormwater wetlands and bioretention areas. More information on Structural Control BMPs can be found in the South Carolina DHEC's Stormwater Management BMP Handbook.