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Role of Sediment as a Stormwater Pollutant

There are a few different contaminants or pollutants that may impact stormwater runoff and related areas for construction sites, and one of the most well-known here is sediment. Often caused by erosion from soil, the presence of sediment in stormwater can be a significant pollutant that must be managed properly on the job site.

At Cearley SWPPP, we're here to help with all stormwater pollution prevention needs in Ogden and nearby areas, from plan creation and permits to inspections, training, signage and more. Here are some basics on what sediment is, the sources it can come from, and why it's a pollutant risk on sites - plus what should be done to control it.

role sediment stormwater pollutant

What is Sediment?

For those unfamiliar with the term, sediment is simply particles of sand, silt, clay and organic material (such as leaves) that become suspended in water. It can come from a variety of sources, including:

  • Erosion: Sediment may come from the natural erosion of soil on a construction site, or any other exposed areas with bare ground.
  • Rain: One possible cause of erosion, rain can also directly affect sediment levels through its direct impact on the exposed soils.
  • Construction activities: Breaking into soil layers during excavation work, or stockpiling dirt and other materials can create an opportunity for sediment to become suspended in water and then released off-site.
  • Runoff from adjacent sites: If there are other construction or development sites in the vicinity, sediment and other pollutants may be picked up in surface water runoff and then transported to your job site.
  • Degrading stream banks: If a stream or river is nearby, sediment can be released into the water from eroding banks.

The Risks Posed by Sediment in Water

There are several ways sediment in waterways can degrade the quality of water and create pollutant and contaminant risks. These include:

  • Suspended sediments and turbidity: When there are large amounts of sediment in water, it can reduce the amount of light penetrating the water, creating turbidity and reducing visibility. This can decrease the ability to spot aquatic life and other organisms that call these waters home. Not only does this block the water from light, it also blocks sunlight and limits the ability of aquatic plants to thrive.
  • Reduced water quality: The presence of sediment in streams and rivers can also degrade the quality of the water, making it appear murky or cloudy. This sediment can deplete oxygen levels, limiting the ability for fish and other species to survive in the area.
  • Higher costs for treatment: If sediment is allowed to reach a water treatment facility, it can cause problems with their operations and require additional treatments. This makes it more costly for the community.
  • Sedimentation of stream beds: One long-term effect that can be enormously disruptive to an environment is sedimentation, when sediment blankets a stream bed and starts choking off the life within. This changes habitat and water chemistry, reducing the biodiversity and life of that area.

Carrying Other Pollutants

Maybe worst of all, sediment often carries other significant pollutants along with it as it flows through water. Here are some examples:

  • Heavy metals: Metals such as lead, copper and zinc may be present in soil and can bind to sediment. When these metals enter water, they can be toxic to aquatic life and other organisms.
  • Organic compounds: Petroleum products, herbicides and pesticides may come into contact with sediment and then make their way into surface water. These pollutants can also impact the local environment in negative ways.
  • Nutrients: Nitrogen and phosphorus are common nutrients that can come from fertilizers or other sources, but they can also become attached to sediment particles. In streams, rivers and lakes this can cause algal blooms that deplete oxygen levels and reduce the health of those waters.
  • Bacteria: Another pollutant that may attach to sediment particles is bacteria. It can enter water from sources such as animal waste, sewage and agricultural runoff, and if it reaches a drinking water source it could be dangerous for human consumption.

Therefore, managing sediment on job sites is essential to protecting the environment, preventing pollution and minimizing potential costs associated with cleanup.

How to Consider Sediment Within SWPPP

Sediment control is a big part of any stormwater pollution prevention plan. It is important to include strategies for sediment control in your SWPPP, particularly if you are working on a job site that has potential for increased erosion or discharge of sediment into receiving waters.

Your SWPPP should include methods and practices for preventing the generation of sediment before it is released off-site, as well as measures for controlling sediment that is already on the job site. These can include things like silt fences, check dams and other best management practices (BMPs) designed to reduce and control sediment.

You should also consider how to prevent erosion from occurring in the first place. This can include slope stabilization practices, using terracing or vegetation, and other methods to reduce the chance of erosion in high-hazard areas. Additionally, consider how you will manage sediment after it is created, such as using catch basin inserts or sandbags for drainage systems.

At Cearley SWPPP, we have a team of stormwater experts who can help you to consider sediment in your SWPPP, so that you can protect the environment and maintain compliance with regulations. Contact us today to learn more about any of our SWPPP services around Ogden.