Sediment Removal from Above-Ground Detention Basins

Understanding Sediment Basins & Sediment Removal from Ponds

Stormwater isn’t clean. Within its flowing waters are many different types of sediment buildup with differing particle sizes. This can include:

• Sand
• Organic matter
• Silt
• Sand
• Clay
• Other floatable debris

When the velocity of the water slows, gravity helps to pull down these particles, known as sediment disposition. Larger particles are more accessible to remove, while smaller particles, such as silt, pose some challenges. This is why silt removal methods and sediment removal from ponds are necessary.

Sediment Removal Solutions: Where Sediment Collects

Sediment removal is necessary for several stormwater sediment traps and structures. Sediment collects in many different areas, including:

• Lakes
• Ponds
• River eddies
• Fluvial flood plains
• Stormwater basins

There are two main types of sediment control basins, so what is the difference between detention vs retention basins and detention ponds vs retention ponds?

A detention basin is made to store stormwater permanently and requires robust detention pond maintenance and sediment removal to help keep it and the surrounding environment clean. In contrast, a retention basin is only meant to hold stormwater temporarily. A benefit of retention basin maintenance is that it often requires less elbow grease because it can be smaller. A retention sediment pond can be used on any size site, while detention basins and ponds are much larger and may require industrial pond sediment removal. Both are equally important to maintain when it comes to sediment removal.

Best Management Practices for Erosion and Sediment Control

What are the methods of sediment removal? Because many different particle types and retention and detention basins differ in size, various methodologies are required for sediment removal from water. Some of the best practices and preferred techniques for detention basin maintenance are listed below:

Manual Removal

Larger pieces of particles can be removed by hand by shovels or rakes. This is a more likely sediment removal method for retention pond maintenance, as these are often smaller bodies that temporarily hold water. Manual methods would be less effective for detention basins or organic sediment removal.

Mechanical Removal

Mechanical sediment removal is a common best practice. Workers can use excavators or backhoes to dig up sediment for smaller particles and larger surface areas. Additionally, sediment dredging is an option. Dredging uses heavy machinery to remove sediment trapped in the basin’s bottom.

Hydrological Removal

Hydrological methods can be used for more challenging removal jobs. Controlled flushing can help discharge sediment, while aerators can stir sediment up to make removal easier.

The following is a list of many different types of sediment removal:

• Mechanical dredging
• Hydraulic dredging
• Chemical sediment removal
• Dredging equipment
• Pumping systems
• Separation equipment
• Dewatering

How Do You Dispose of Sediment Removal?

Now that we know what can remove sediment from suspension in stormwater, where does the sediment go once it’s been removed? There are several different ways to accomplish this.

First, you must comply with local laws and regulations regarding removal and disposal. Before attempting any sediment removal techniques, you must check with local officials to see if you require a permit for the job. In most cases, it depends on the size of the stormwater detention basin.

Safety is also imperative. The water quality should be checked and monitored, and all workers on site should wear the proper personal protective equipment (PPE).

In general, sediment removal is disposed of using landfills, recycling, or composting. Landfills, however, are not absolute, and you must check with your town first before you use this method. Organic sediment is best for composting; in many cases, sediment can be recycled for future construction projects. Once removal is complete, it’s time to think about how you fix sediment runoff and how you reduce sedimentation in suspension.

Detention Basin Maintenance and Preventing Future Problems

Once sediment has been cleared, maintenance is paramount. Proper maintenance and sediment trap erosion control can help prevent large sediment removal projects down the road. Some techniques used to help minimize sediment buildup include:

• Vegetation management: Managing and controlling vegetation growth in a basin can also help prevent sediment accumulation.
• Sediment traps: These are simple ways to collect sediment before removal is required. However, smaller particles may still accumulate.
• Erosion control: Erosion control, particularly within sediment traps and on surrounding slopes, can help negate the need for frequent sediment removal.

Overall best practices for detention basin maintenance include controlling runoff on the slopes, controlling vegetation, manually removing debris and particles when possible, sediment removal, and equipment maintenance. These best practices can help keep your areas maintained and free of debris and your stormwater runoff successful and environmentally friendly.