Turbidity Curtains and Barriers

Floating turbidity barriers or curtains are barriers that control suspended solids and turbidity in a water column generated by dredging and disposal of dredged material. They are considered to be the last line of defense against sediment migration into nearby marine environment.

 

A floating turbidity barrier may be a permeable or an impermeable device used to isolate the near shore work area and to confine the sediment entering into a body of water. These devices may be deployed in areas where sediment discharge to a stream is unavoidable. The curtains are designed to effectively deflect and contain sediment within a limited area and to provide sufficient retention time for the sediment particles to settle in the bottom of the reservoir.

 

Our turbidity curtains consist of a permeable or impermeable body fabric that is suspended vertically in a body of water, with floats at the top and ballast chain in the bottom to hold the curtain in a vertical position. They are commonly used in the vicinity of marine environments to protect the contained water from turbulence, allowing particles to fall out of suspension.

 

Standard floating turbidity curtains come in three different constructions. They are referred to as Type 1, Type 2 and Type 3 as per the U.S. Army Corp of Engineers (USACE) specifications.

 

Type 1 turbidity curtains should be used in protected areas where there is no current and the area is sheltered from wind and waves. Some of the applications include ponds, shallow lakes, small streams and marshes.

 

Type 2 turbidity curtains should be used in areas where there may be slow to moderate running current (up to 2 knots or 3.5 feet per second) and/or wind and wave action which can affect the curtain. It has a top load cable and special stress plates for reinforcing the corners and is designed to handle more severe conditions. It is recommended for lakes, streams, intercostals and tidal areas.

 

Type 3 turbidity curtains should be used in areas where considerable current (up to 3 knots or 5 feet per second) may be present, where tidal action may be present, and/or where the curtain is potentially subject to wind and wave action. A woven polypropylene monofilament fabric screen is sewn to the body fabric to offset any hydrodynamic forces acting on the curtain.

 

Turbidity curtains should be installed at the location shown on the plan and according to the manufacturer’s guidelines or as directed by the engineer. The curtain must be installed considering site details such as current velocity, water depth, bottom sediment types and background levels of turbidity.

 

During recent years there have been increased concerns regarding the potential impacts that dredging of contaminated sediments may have on the nearby environmental resources. Turbidity curtains are designed to control suspended sediment dispersion in a body of water caused during dredging or construction activities in the vicinity of a marine environment.