Sediment control
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A sediment control is a practice or device designed to keep eroded soil on a construction site, so that it does not wash off and cause water pollution to a nearby stream, river, lake, or sea. Sediment controls are usually employed together with erosion controls, which are designed to prevent or minimize erosion and thus reduce the need for sediment controls. Sediment controls are generally designed to be temporary measures, however, some can be used for storm water management purposes.
A sediment control is a practice or device designed to keep eroded soil on a construction site, so that it does not wash off and cause water pollution to a nearby stream, river, lake, or sea. Sediment controls are usually employed together with erosion controls, which are designed to prevent or minimize erosion and thus reduce the need for sediment controls. Sediment controls are generally designed to be temporary measures, however, some can be used for storm water management purposes.
Commonly used sediment controls
Check dam Diversion dike (temporary) Fiber rolls Gabions Gel Flocculant Siltbusters Sand bag barrier Sediment basin Sediment trap Silt fence Storm drain inlet protection Straw bale barrier Turbidity curtain
Active treatment systems
Treatment of silt impacted water using equipment and chemical addition, commonly called an active treatment system, is a relatively new form of sediment control for the construction industry. These systems are designed to reduce Total Suspended Solids (TSS) from entering nearby water bodies where silt pollution can be of environmental concern. Sediment-laden stormwater is collected and or pumped, and a chemical flocculant is added to aide in clarification. Types of flocculant include; Natural Polymers: Derived from natural sources, such as starch, chitosan, and guar gum. Synthetic Polymers: These include polyacrylamide and their derivatives, which can be tailored to specific water treatment needs. They are effective at lower dosages compared to inorganic flocculants. Inorganic Flocculants: Aluminum Sulfate (Alum), Ferric Chloride, Ferric Sulfate, Polyaluminum chloride Extreme caution should be observed when using cationic flocculants like chitosan or positively charged polyacrylamide or polyDADMAC which cause hypoxia in fish. The use of anionic,negatively charged, flocculants is best practice on open loop treatment systems to ensure the protection aquatic habitat, fish and invertebrates. The water is then either filtered (sand or cartridge filter,) or settled (lamella clarifier or weir tank) prior to discharge. Chemical sediment control is currently used on some construction sites around the United States and Europe, typically larger sites where there is a high potential for damage to nearby streams. Another active treatment system design uses electrocoagulation to flocculate suspended particles in the stormwater, followed by a filtration stage. Active treatment systems require technical expertise to operate effectively as multiple types of equipment are utilized.
Regulatory requirements
All states in the U.S. have laws requiring installation of erosion and sediment controls (ESCs) on construction sites of a specified size. Federal regulations require ESCs on sites and larger. Smaller sites which are part of a common plan of development (e.g. a residential subdivision) are also required to have ESCs. In some states, non-contiguous sites under are also required to have ESCs. For example, the State of Maryland requires ESCs on sites of or more. The sediment controls must be installed before the beginning of land disturbance (i.e. land clearing, grubbing and grading) and must be maintained during the entire disturbance phase of construction. Approval for use of any chemical flocculant must be obtained prior to its deployment.
See also
Certified Professional in Erosion and Sediment Control (CPESC) Geotechnical engineering Geotextile (material used in erosion & sediment controls) Nonpoint source pollution Stormwater Universal Soil Loss Equation
References
External links
Erosion Control - a trade magazine for the erosion control and construction industries International Erosion Control Association - Professional Association, Publications, Training “Developing Your Stormwater Pollution Prevention Plan: A Guide for Construction Sites.” - U.S. EPA Gel Flocculant - Type of semi aqueous flocculant used in Passive water treatment systems
Text derived from https://en.wikipedia.org/w/index.php?oldid=1328410303 under CC BY-SA 4.0; modifications have been made.