"Turbidity" refers to water that is murky due to sediment. Of course, all water will have some natural sediment, so this will cause some turbidity. Still, man-made actions like construction and excavation can cause more sediment, damaging the surrounding ecosystem.
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Type 1 Curtains
Type one curtains are designed for bodies of water with calm conditions and no waves or tides, such as canals, small ponds, and small lakes. These curtains range in size from 50 to 100 feet (15.24 to 30.48 meter) long. They can be made as deep as necessary.
Note: The type 1 DOT 5' x 50' curtain is a stock item and typically ships within 1 business day. All other type 1 DOT curtains typically require a 5-7 business day fabrication period prior to shipping. All prices include shipping to any address within the continental United States.
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Type 2 Curtains
Type two curtains are best in medium waters that move at a maximum of 1.5 knots and waves up to three feet, including rivers, harbors, and ports with little wind and current. They are typically used for demolition work, dredging, pile driving, and other construction activities.
Note: All type 2 DOT curtains typically require a 5-7 business day fabrication period prior to shipping. All prices include shipping to any address within the continental United States.
Call us at (800) 748-5647 for pricing and additional information.
Type 3 Curtains
Type three curtains are the most heavy-duty type and are used in demanding water conditions. A type three turbidity curtain should be used if a construction site is near a river, bay, harbor, or inter-coastal waterway.
Note: All type 3 DOT curtains typically require a 5-7 business day fabrication period prior to shipping. All prices include shipping to any address within the continental United States.
What Is a Turbidity Curtain and How Does It Work?
A turbidity curtain is a barrier used to trap sediment in bodies of water. The curtains are weighted at the bottom, so sediment doesn't get underneath the curtain, and they are supported at the top with a flotation system. These curtains prevent sediment from work sites from getting into the body of water.
Turbidity curtains are typically installed so that they’re parallel to the direction of flow, and the height of the curtain should rise to the height of the maximum expected water level. The bottom of the curtain should always be in contact with the bottom of the body of water and should be held down by a weight.
These curtains should be made of nonwoven material in bright colors so boaters and swimmers can avoid them.
Where Are Turbidity Barriers Needed?
Turbidity barriers are needed on construction sites near bodies of water where conventional erosion and sediment controls can't be used. A turbidity barrier should be used wherever water is at risk of being dirtied by contaminated sediment.
The following activities near bodies of water benefit from the use of a turbidity curtain:
Turbidity barriers used during shoreline construction
What Are the Environmental Construction Requirements for Turbidity Sediment Control?
Construction projects must abide by numerous environmental requirements regarding turbidity sediment control, including the Clean Water Act, the National Pollution Discharge Elimination System, state D.O.T. requirements, and local regulations.
Let's take a look at these regulations and requirements:
The Clean Water Act (C.W.A.) regulates the discharge of pollutants into bodies of water in the United States. All bodies of water with a "significant nexus" to "navigable waters" are covered. This vague terminology allows some judicial interpretation.
The C.W.A. established the National Pollutant Discharge Elimination System, which is a permit system that regulates sources of pollution, including:
Sewage treatment plants
These sources cannot discharge pollutants into waters without a permit.
Each state uses different terminology in their Department of Transportation regulations regarding turbidity curtains, so contractors must carefully consult their state's requirements to ensure they comply.
sediment turbidity curtain
Most states use the phrase "turbidity curtain" and distinguish between type one, type two, and type three curtains, but there are some exceptions:
sediment turbidity curtain
Connecticut: Names four different types of curtains in their regulations: Flat Water, Lightweight, Middleweight, and Heavyweight.
Florida: Refers to turbidity curtains as "floating turbidity barriers."
Iowa: Refers to turbidity curtains as "floating silt curtains." Instead of distinguishing between type one, type two, and type three curtains, the state identifies two kinds of curtains: Still Water and Moving Water.
Minnesota: Describes turbidity curtains as "floating silt curtains" or "silt barriers."
Mississippi: Uses the "floating turbidity barrier" terminology.
Nebraska: Uses the term "turbidity barrier."
New Jersey: Uses the terminology "floating turbidity barrier."
North Dakota: Uses the same terminology as Iowa.
South Carolina: Refers to turbidity curtains as "floating turbidity barriers" and identifies three types: Light Duty, Medium Duty, and Heavy Duty.
Tennessee: Uses the phrase "floating turbidity curtain."
Some states are more lenient than others, so contractors must be up-to-date before bidding on a project.
Local regulations have different requirements for specific issues with turbidity curtains, such as whether or not a curtain needs to be lit. Contractors must comply with these regulations.
Installing a Turbidity Curtain
Turbidity curtain installation is not a small undertaking, and it is different for every project based on the construction site environment, available equipment, and the operator. Standard turbidity curtains come in sections that are fifty feet in length or one hundred feet in length. Therefore, the first step of any installation process is to:
Standard turbidity curtains come in sections that are fifty feet in length or one hundred feet in length. Therefore, the first step of any installation process is to lay out these sections and connect them to form the length the specific project needs. The sections must be connected before being put into the water.
Ensure that the turbidity curtain sections are laid on an area with no sharp objects or rough surfaces that could damage the curtain. If the construction area is a rough surface, you should lay a tarp or a plastic sheet over the land to avoid damage.
Turbidity curtains are usually shipped in bundles and on pallets. Take care when removing the wrap and the straps around the curtains.
Most curtains will have connectors attached to the ends of the curtain sections. Use these connectors to attach the curtain sections together. Attach the skirt ends together with the rope and the grommets. After this, fold the skirt back underneath the float elements and tie the straps around the skirt and the flotation system.
Use a two bridle to tow the curtain to its final location, then begin anchoring.
The anchoring plan will vary depending on the environment and anticipated wind and wave conditions.
Inspecting a Turbidity Curtain
Maintaining a turbidity curtain is not complete once it is installed. While in service, the curtain should be inspected regularly.
Turbidity curtains installed in areas with high winds and currents should be inspected every day, as well as those in areas with high marine traffic. If the curtain is in a calmer area, an inspection once a week will suffice unless there is a storm.
Inspections of turbidity curtains should address and/or check:
U.V. radiation damage
Refuse in silt screen or curtain
Obstructions to water flow
Curtain in upright position
Curtain chains, bands, plates, and joint connectors are intact
Turbidity curtains are useful tools, but they must be maintained for optimal performance.
Floating & Staked Turbidity Barriers
Turbidity curtains are created to prevent the flow of stormwater runoff loaded with sediment from construction sites. These barriers will keep this runoff contained in a specific and limited area allowing the sediment to settle out before being carried into waterways. These turbidity barriers are available in two different styles either staked or floating.
Floating turbidity curtains are also known as Floating Turbidity Silt Curtains. This barrier consists of a flotation boom on the top and an impenetrable fabric curtain that extends down under the water. There is a heavy galvanized steel chain that is sealed into the hem that runs along the entire bottom of the curtain. This keeps the curtain vertical in the water. The ends of them are sealed around a rope and grommeted to allow for the attachments.
There Are 3 Types Of Floating Turbidity Barriers:
First DOT Floating Turbidity Barriers:
This is the most popular barrier in the Tough Guy ® line. This kind of barrier is recommended for sites that are located in protected areas that are only exposed to light winds and currents that run less than one foot per second. These water elements may be ponds, small streams, shallow lakes, or marshes.
In order to maintain the barrier's position will require anchoring with stakes, concrete blocks or an anchor kit. Sections of the barrier are connected by rope lacing or nylon ties.
Second DOT Floating Turbidity Barriers:
In the Tough Guy ® line, this is the workhorse of the group. This barrier has a top load cable and special stress plates for reinforcing the corners and is specifically designed to handle severe conditions. This kind of barrier is highly recommended for areas that have currents that run up to five feet per second. These elements are found in lakes, streams, inter-coastal, and tides.
It is highly recommended that you contact a qualified engineer for assistance when facing these conditions because the anchorage and installation must be designed exactly to meet these situations The barrier sections are connected with rope lacing or nylon ties.
Third DOT Floating Turbidity Barriers:
This barrier provides approximately 20% of the skirt fabric being replaced with a polypropylene filter fabric that conforms to some State DOT Specifications. The filter fabric is in place to reduce pressure on the curtain while it retains silt. The filter fabric is woven tightly to retain the silt but not so much that it will reduce pressure on the curtain.
If this fabric is not woven tightly enough, it will not be able to hold most silt and sediment particles. Also, the fabric cannot be heat sealed causing a reduction in the curtain's strength and longevity.
Installation Of Barriers:
Installation and anchoring must be designed to meet the site's condition. Floating Turbidity Barriers that are being installed in moving water, tidal conditions and windy areas must be anchored in place.
All 3 - First, Second and Third Meet Or Exceed All Known Federal And State Governmental Specifications, Including NPDES Phase II Requirements.
The standard length is 50-feet with depths of 3-feet, 4-feet, or 10-feet. Custom lengths can be created up to 100-feet with depths of 2-feet to 100-feet which can be manufactured and shipped quickly.
Custom colors and accessories are also available such as the Lighted Navigation Buoys and Anchor Kits.
Tough Guy® Anchor Kits come with everything that is required to anchor the floating turbidity barriers. You will get an anchor, chain, rope, thimbles, anchor buoy, and shackles. You do not have to assemble anything because they are pre-assembled in the factory.
Floating turbidity barriers that are installed in moving water, tide areas and/or windy conditions must be anchored in order to stay in place. Having an anchoring system that is assembled in the factory will make the entire installation process much easier.
• Anchor Kit A has an 18 lb anchor plus a 50-foot rope or longer if required. • Anchor Kit B has a 25 lb anchor plus a 50-foot rope or longer if required.
Both these kits are very easy to install. Just snap onto the cable loop at the joint of the barrier's top load line. Re-position, position, and/or remove using the Retrieval or Positioning Buoy.
All DOT barriers should meet certain state specifications but check your state's requirements first.
The Staked Turbidity Barriers:
These barriers are uninterrupted panels of impenetrable fabric made of vinyl-polyester that can stop stormwater runoff or can re-direct it to an area for holding. When installed on land, these barriers are similar to silt fences. They should be 8 inches below the grade and 36 inches above the grade and attached to stakes. These barriers can be installed in as much as 18 inches of water.
The curtain is approximately 44 inches wide and has a heat-sealed hem along the top edge. There should be an 8-inch trench along the perimeter line and then stakes are driven every 6-feet along the downside of the slope.
The upper area of the barrier is attached to the stakes using staples, nylon ties, or wire. The top of the barrier must be 36 inches above the grade. The bottom edge of the curtain must be placed in the trench which is then backfilled.
This barrier system works best with porous soil that is on a moderately sloping site. The stakes can be made of wood or metal but must be purchased separately.
The standard color of the staked barriers are Yellow. For a quote or any questions on the staked barriers, please call us at 800-748-5647. Also, for additional information please call AER-FLO (800.823.7356) , the manufacturer of the Tough Guy turbidity curtains.
Humans are going to continue engaging in construction activity, which will impact the environment around the project. A turbidity curtain is one way to minimize the negative effects of construction on marine ecosystems. Not only does the curtain protect the environment, but it also helps the project stay in compliance with federal, state, and local laws and regulations.