Texas Boom Company has produced a number of silt curtains recently from dredging projects across the US.  As you would expect, as a dredging operation takes place, mud and sand are stirred into the adjacent water.  This material remains suspended in the water until it washes away or settles back to the bottom.  Dredgers use floating silt curtains (turbidity curtains) to keep silk and sediment from migrating while suspended.  This helps to avoid muddying local waterways during the dredging process.  Whether used to meet regulatory requirements or simply as a courtesy to others, silt curtains are effective in helping to reduce sediment runoff. 

Three recent projects are highlighted below, selected because our customers were kind enough to share pictures of the silt curtains in use.  

The first project was a roadway construction project here in Texas.  As can be seen in the image, the silt curtain is effective in keeping the sediment from escaping the construction area.  Because the silt is contained, it will eventually settle in place, leaving the area water clear and free of an abundance of eroded mud. 

Cattail Marsh is a 900 acre wildlife area located in Beaumont, Texas.  This marsh is located adjacent to Tyrrell Park and serves as a component of the waste water filtration system for the city.  The marsh features a 520 foot boardwalk that was installed in 2016 at a cost of $285,000.  Cattail Marsh and the surrounding area support a wide variety of local wildlife and is a popular bird watching site. 

As is common in many bodies of water in the area, Water Hyacinth has taken root and spread rapidly across the entire marsh.  Water Hyacinth is an invasive plant species that is recognized as one of the fastest growing plant species in the world.  The plants primary means of reproduction are runners that eventually form sister plants.  It also produces large volumes of seeds that remain viable for up to 30 years.  Because of its ability to rapidly reproduce, coverage areas can double in periods as quickly as two weeks.  

If left unchecked, Water Hyacinth can completely cover a body of water, resulting in reduced water flow, complete blocking of sunlight to submerged plant species, and a depletion of oxygen from the water itself.  These results can have a major detrimental impact on plant and animal species.  This plant is difficult to control once introduced to a lake, pond or stream.  Water Hyacinth has no know direct food value for wildlife.  

Whether you are installing oil spill containment boom or turbidity curtains, these products are only one of the items you will need for a successful deployment.  Factors such as wind, tide levels, currents, boat traffic, and safety issues are all considerations when developing your plan. Texas Boom Company offers a wide range of accessories that can make your installation easier, safer, and more effective.  Anchors, lines, buoys, lights, beach stakes, and tow bridles can all be important additions to a successful installation.  

Installation layouts can result in varied layouts and patterns to best accomplish the intended goal of containing material or silt.  These same considerations come into play with traditional oil spill containment boom, sorbent containment boom, inflatable containment boom, shore barrier boom, or permanent type fence boom.  Texas Boom Company offers installation instructions and a number of diagrams that show different layouts for containment boom installation or turbidity curtain installation. 

Layout:

Furling lines (also referred to as reefing lines) are an optional feature on turbidity curtains.  These ropes run vertically spanning the height of the turbidity curtain on both sides at set intervals.  The furling lines are attached at the top through tabs with grommets, at the bottom at the ballast chain through a grommet, and then looping back to the top on the reverse side of the skirt to another attachment tab.  The furling lines can be used to adjust the depth that the skirt extends below the surface.  They can also be used to slope the bottom of the turbidity curtain to mirror the contour of the bottom.  Because the depth of the turbidity curtain can be adjusted, it allows the curtain to be used in multiple locations, at locations with varying depths, and at locations with significant tidal swings.

Turbidity curtains are most effective when the bottom of the skirt is suspended a foot above the bottom.  This prevents the build-up of silt on the base of the skirt which over time can result in the freeboard of the turbidity curtain becoming submerged below the water surface.  The bottom of a turbidity curtain dragging on the bottom can also generate additional silt.   When the skirt drags on the bottom, it can also reduce the life of the turbidity curtain.  Finally, but leaving a gap between the skirt and the bottom of the body of water, it allows for fish and other wildlife to freely bypass the turbidity curtain without harm. 

Furling lines can also aid in the deployment and retrieval of turbidity curtains.  It is typically easier to handle a turbidity curtain when the skirt is furled or bundled against the flotation.  This reduces the impact of tides, currents, and wind.  The furling lines are typically loosened once a turbidity curtain is anchored into place, allowing the skirt to drop.  Likewise, the furling lines can be used to bundle the turbidity curtain skirt while it is still in the water, making the removal less burdensome as well. 

Differences between Containment Boom and Turbidity Curtains

To the casual observer, it may be hard to differentiate between a spill containment boom and a turbidity curtain.  They do in fact look similar when deployed in the water and differences can be subtle and hidden below the surface of the water.  Depending on the application, oil spill containment boom can be used as an effective silt barrier when the skirt length required is shorter due to shallow water conditions.   In the image shown below, a spill containment boom has been deployed to serve as a turbidity curtain. 

Turbidity curtains, also referred to as silt curtains, offer a means to keep suspended particles from vacating the immediate area in a body of water.  The curtains hang from floats down into the water and impede the flow of the turbidity or silt.  Over time, the suspended sediment settles back to the bottom.  These floating curtains can be made from solid fabrics that impede all flow of water, or built using a geotextile mesh  fabric that allows water to flow through while still blocking the silt or other particles from escaping. 

One application for turbidity curtains is to contain runoff from storm drain or pump station discharge points.  These are typically exit points for storm drains systems that provide drainage from developed urban areas in order to prevent or minimize flooding.  Because the water is collected from public streets and other areas, the water is prone to wash away trash, dirt, and other debris.  Instead of simply dumping this water into waterways, the systems may run the water through filtering processes to remove garbage and larger debris.  However, these filters may not capture all of the materials suspended in the water. 

Every day there are countless ongoing dredging and marine construction projects ongoing across the United States.  These marine projects are driven by the need for repairs, development, and shoaling.  These work zones typically require equipment and operations to be ongoing in waterways that are normally navigated by boat traffic.  As these projects are executed, safety hazards can often arise not only for the workers themselves, but also for anyone on a boat in the area.