The Clean Water Act establishes regulations for limiting the discharge of soil sedimentation into U.S. rivers, streams, lakes and other waterways, including wetlands. Sedimentation runoff from construction sites is typically 10 to 20 times greater than those of agricultural land, and 1,000 to 2,000 times greater than those of forest lands. The purpose of the regulation is to prevent the discharge of soil and other materials from entering into waterways and wetlands.

Construction sites are prone to damage from storm water runoff and erosion. The destruction of ground cover, topsoil stripping and the movement of construction equipment and trucks around a site dramatically increase erosion and runoff. This becomes a safety and risk management issue because rivers, streams and navigable waterways become impaired and water quality is affected.

For land developers and construction site managers, failure to control water runoff and erosion can be costly. When hillsides are stripped of cover by excessive erosion, contractors are required to replace topsoil and reseed to prevent additional damage and return the beauty of the hill. If culverts, sewers, storm drains and curb areas are clogged with sediment they must be cleaned up and returned to normal. In addition to the visible damage, there is often the not so obvious damage to water quality, fishing, critical habitats, submerged aquatic vegetation and recreational activities.
Navigation is affected too. For example, the Miami River in Florida has been severely affected by pollution associated with upland erosion. Sedimentation deposited in the Miami River channel contributes to the water quality and navigational problems of this once-thriving waterway, as well as Biscayne Bay.

The following was reported by Pierre Y. Julien and Chad W. Vensel from the Department of Civil and Environmental Engineering, Colorado State University:

“Sedimentation on the Mississippi River and its major tributaries, like the Missouri, Ohio and Illinois Rivers, has long been an issue of serious concern. Major tributaries and the delta area have been susceptible to significant changes in river discharge, cross section, width, mean bed elevation, water surface elevation and sediment concentration. Additionally, water quality has become an issue of increasing concern throughout the basin due to the vast dependence of life on the river. The sedimentation issues have had broad effects upon several aspects of life, both terrestrial and aquatic, within the Mississippi River Basin.”

Sedimentation does not only create problems on navigable waterways, it also affects land-locked lakes and wetlands. Sediment being transported through streams is a natural process. However, development such as housing, infrastructure, logging and other such activities can have an influence on the amount of sediment and erosion that occur in a watershed. As this sediment continues to be carried through the tributaries, it eventually settles out at the outlets of these streams creating numerous large deltas. Deltas can impede fish migration, and act as bedding areas for nuisance aquatic species, hinder recreational activities, damage the fish population and negatively affect lakefront homeowners and their docks.

Stop Erosion and Limit Sedimentation

Once land is disturbed by construction operations, the problem of runoff and sedimentation can quickly intensify. Therefore, construction managers are required by the EPA, state and local regulations to reduce erosion and retain sediment onsite during and after construction. Prior to starting a project, construction managers and contractors must prepare and implement an erosion and sedimentation control plan describing how they plan to contain erosion and prevent sediment from entering the streams, rivers, lakes, wetlands and the ocean. Appropriate permits must be obtained from the EPA and/or state/local authorities for all construction sites, with very few exceptions including those covering less than five acres that have the potential to create runoff.

Erosion and sedimentation control (ESC) plan documents explain and illustrate the measures that will be taken to control erosion and sedimentation problems on construction sites. Typically, an ESC plan is incorporated into the site planning and will include the following elements:

• Description of predominant soil types;
  
• Details of site grading including existing and proposed contours;
  
• Design details and locations for structural controls;
  
• Provisions to preserve topsoil and limit disturbance;
  
• Details of temporary and permanent stabilization measures; and
  
• Description of the sequence of construction.
  

There are two types of erosion and sediment controls — non-structural and structure. Both are generally incorporated into the ESC. The nonstructural controls would include planning and designing with the natural constraints of the site, minimizing the disturbance of soil, consideration of streams and where runoff will go and stabilizing or protecting cut-and-fill slopes. Structural controls are physical controls such as mulch mats, compost and seeding; the use hay bales, filter fabric or silt fences; and/or channeling runoff into sedimentation traps or basins or pumped water can be collected in sedimentation tanks. Most control plans will incorporate a number of these methods into one plan. Note that sedimentation control is not only about the movement of sediment via water, wind is another factor that must be taken into consideration.

Controls must be in place for sites along roadways. Water entering into sewers and storm drains ends up in a treatment plant or waterway where sedimentation can collect and load up the plant or waterway. Care must be taken to keep sediment and mud from washing into streets, sewers and storm drains even when waterways are not nearby.

Control plans should be designed to prevent sediment from washing off the site when it rains or to provide for a method of filtering water that is discharged from a pump. Survey the site and look for drainage ditches, basins, streams, rivers, sewer and storm drain inlets and other areas where runoff could carry sediment to waterways. After determining how and where sediment could enter waterways, block or filter the flow. For more detailed ideas and methods for controlling runoff visit www.epa.gov/nps/MMGI/Chapter4/ch4-3a.html.

Regular inspection and maintenance are needed for most erosion control practices to remain effective. Management should assign someone the responsibility of reviewing and routinely inspecting the methods that have been implemented to prevent runoff.

Due diligence on the part of contractors is extremely important to reducing the amount of sedimentation that enters U.S. waterways. Clean water is a large part of what NUCA is all about. Therefore, NUCA members should do all they can to prevent runoff and pollution from entering the nations waterways. Don’t stop there — take the opportunity to educate and inform other construction contractors of the need and importance of preventing unnecessary sediment and pollution from entering into streams, rivers, lakes and other wetlands.

George Kennedy is NUCA Vice President of Safety.