Silt curtains are protective barriers used in a marine environment to control pollution caused by suspended sediments, such as silty soil or stone dust. When water runoff or construction activity creates sediment in waterways, silt curtains are used to contain this suspended sediment. By confining the sediment to a specific area, the rest of the waterway is protected from the damaging effects of pollution.
In many areas of the world, the use of silt curtains is mandated by governments to control pollution of the waterways. In the United States, for example, the Environmental Protection Agency (EPA) and the Clean Water Act have been developed to control pollution of natural resources, including waterways. The Clean Water Act specifically mandates the use of silt curtains as a barrier to contain and reduce pollution caused by construction activity and shoreline stabilization procedures.
Silt curtains are also called silt barriers. These protective barriers are available in floating and staked designs. Floating silt curtains are available in three types.
A type I floating silt curtain is designed for use in calm waters. Calm water applications might include small ponds or inland lakes and canals. This type of silt curtain is well suited to controlling sediment pollution caused by rain water runoff associated with nearby construction or agricultural activity.
Type II floating silt curtains are designed for use in medium waters. This silt curtain type is more rugged than the type I silt curtain. It is used in rivers and streams with a more noticeable current and surface activity. The type II floating silt curtain is commonly used during bridge construction or demolition and to control sediment created during shoreline stabilization efforts.
A type III floating silt curtain is built for use in rough waters and intercoastal waterways. These silt curtains are designed for deployment in areas that have high currents and heavy surface activity. Commonly seen in areas where there is construction of a large building near the waterway or in cases of environmental disaster, the type III silt curtain is suitable for the cleanup of industrial spills and the control of heavy metal runoff. Custom designed type III silt barriers are commonly used in the cleanup and containment of oil spills.
Staked silt barriers and silt fences are designed for the control of sediment in areas of extremely shallow water with very limited current and no surface activity. This type of silt curtain is commonly used in roadside ditches or very shallow canals to control runoff from road construction or erosion. It is designed to confine sediments in one place but it is not built to withstand the current and surface activity of the floating silt curtains.