Sediment Pollution: Reducing Its Impact On Our Environment

Sediment pollution is a pressing environmental issue that arises when excessive particles of soil, sand, and silt wash into water bodies, degrading water quality and harming aquatic life. This issue is predominantly caused by construction activities, agriculture, and deforestation, which increase erosion and runoff. To protect our waterways and marine ecosystems, it is crucial to understand the sources and impacts of sediment pollution and implement effective prevention and remediation strategies. This paragraph introduces the topic of sediment pollution and its effects, highlighting the need to explore strategies for mitigation.

Implement erosion control measures on construction sites

Construction sites are a major source of sediment pollution, as soil erosion can cause sediment to enter nearby water bodies. To reduce sediment pollution, implementing effective erosion control measures on construction sites is essential. Here are some detailed strategies and techniques to achieve this:

Planning and Design

Before starting construction, it is crucial to develop a comprehensive construction plan that incorporates erosion and sediment control measures. This includes sequencing construction activities to minimize the area disturbed at any given time. Construction phasing, or intentionally clearing one area at a time, helps prevent large areas from being bare and exposed to erosion. Proper planning can reduce the need for costly and larger structural sediment control solutions. It is also important to schedule excavations and earthworks for dry seasons or periods of minimal rainfall to minimize erosion potential.

Vegetation and Land Management

Vegetation plays a vital role in preventing soil erosion. Establishing and maintaining vegetated buffer zones around water bodies, natural areas, and trees can protect these sensitive areas from sediment runoff. Additionally, preserving topsoil and limiting disturbance to existing vegetation, especially on steep slopes, is essential. When clearing land, only clear the areas essential for construction to minimize soil exposure.

Structural Controls

Implementing structural controls can effectively manage sediment runoff and prevent erosion. This includes the use of sediment basins or traps, which are engineered structures that allow sediment to settle out of urban runoff. Filter fabric fences can also be used to filter out sediment from sheet flow runoff. For drainage systems, fiber logs, such as straw, wood, or coconut fiber logs, can be employed to slow water flow and filter sediment. Rock construction entrances are another effective measure, where vehicles passing in and out of the site can help remove sediment from their tires.

Soil Stabilization

Soil stabilization techniques are crucial for preventing erosion. This includes covering disturbed soil with vegetation, mulch, or erosion control blankets to reduce the risk of displacement. Seeding and fertilizing disturbed areas can aid in establishing vegetative cover, which controls soil erosion once established. In areas with steep slopes or highly erodible soils, hydraulic mulching can be applied using hydroseeding equipment.

Perimeter Controls

Implementing perimeter controls is essential to prevent sediment from leaving the construction site and polluting nearby waterways. Silt fences, staked turbidity barriers, and sediment dikes can be used to filter water and retain sediment. These measures ensure that any sediment disturbed on the site remains contained and does not impact the surrounding environment.

By following these erosion control measures, construction sites can significantly reduce their contribution to sediment pollution and minimize their environmental impact.

Use vegetation to stabilise soil

Vegetation is a powerful tool in the fight against sediment pollution. Plants stabilise soil, reducing the amount of sediment that ends up in our waterways. This is especially important given that sedimentation is the leading cause of non-point-source pollution.

Plant roots bind sediment together, making it harder to erode. They also help to hold the ground in place, preventing soil movement into streams, rivers, and lakes. The roots of marram grass, for example, can grow up to 3 metres long, reaching down to the water table.

The stems and leaves of plants cover the ground, protecting sediment from wave, wind, and tidal erosion. They interrupt the flow of wind and water, reducing their velocity and encouraging deposition.

Vegetation also slows water movement, reducing soil erosion. Leaves, stems, and other plant parts interrupt raindrops, reducing the velocity of their impact on the soil. Well-established vegetation slows water movement across the soil surface, allowing more water to soak in.

In addition to their stabilising effects, plants also add organic matter (hummus) to the soil when they die, improving its ability to retain moisture and nutrients.

To make use of these benefits, it is important to maintain vegetation near waterways. Michigan, for example, has established guidelines recommending that a buffer strip of at least 100 feet of vegetation, known as a riparian management zone (RMZ), be left intact next to waterways.

Improve stormwater management systems

Stormwater management systems can be improved by implementing low-impact development (LID) practices, also known as green infrastructure. This approach focuses on reducing runoff and improving water quality. LID practices help to maintain natural hydrologic cycles by utilising site grading, vegetation, soils and natural processes to absorb and filter stormwater onsite. Here are some specific ways to improve stormwater management systems:

Vegetated Swales/Dry Swales

Swales are drainage paths or vegetated channels used to transport water. They can be employed in small drainage areas with low runoff instead of underground storm sewers or concrete open channels. Swales help to slow down runoff, facilitate infiltration and filter pollutants as the water flows through the system.

Curb and Gutter Elimination

Curbs and gutters rapidly collect and transport runoff to stormwater drains without allowing for infiltration or pollutant removal. By eliminating curbs or adding curb cuts, runoff can be redirected into pervious areas and filtered through LID features. Swales can also serve as an alternative to curbs and gutters, providing a more natural means of conveying runoff.

Vegetated Filter Strips

Vegetated filter strips consist of dense vegetation bands through which runoff is directed. They are well-suited for gently sloping areas without channelised flow. These strips can effectively treat runoff from roads, highways, roof downspouts, small parking lots and impervious surfaces. The vegetation acts as a natural filter, trapping pollutants and sediment before they reach water bodies.

Sand and Organic Filters

Sand and organic filters are highly effective in removing pollutants from stormwater. An example of this is the EPA's Region 7 Office in Lenexa, Kansas, which uses vegetated swales, sand filters and a constructed wetland to treat and infiltrate 100% of the stormwater on its 30-acre property. The runoff passes through sand beds, removing floatables, particulate metals and pollutants before being discharged.

Constructed Wetlands

Constructed wetlands are designed to mimic natural wetlands, capturing and filtering stormwater while creating diverse wildlife habitats. They can hold standing water on the surface or just below the soil surface. These wetlands not only improve water quality but also provide essential habitats for various species.

Permeable Surfaces

Permeable surfaces, such as pervious concrete, porous asphalt or interlocking concrete pavers, allow stormwater to infiltrate through porous surfaces into the soil and groundwater. By using permeable pavements for parking lots, driveways or sidewalks, the amount of stormwater runoff can be significantly reduced, preventing excess water from overwhelming natural waterways.

By implementing these improved stormwater management practices, we can better control sediment pollution, protect natural habitats, and ensure cleaner, healthier water sources for both human and ecological well-being.

Sweep driveways and sidewalks instead of hosing them off

Sweeping driveways and sidewalks with a broom and dustpan is a simple yet effective way to reduce sediment pollution. This practice is encouraged because hosing off these surfaces can cause a range of pollutants to enter nearby water sources. When you use a hose to clean your driveway or sidewalk, you are essentially washing pollutants such as dirt, grass clippings, oil, fertilizers, and other contaminants into the street. These pollutants can then make their way into local water bodies, including lakes and rivers, causing sediment pollution.

Sediment pollution has detrimental effects on the environment. It occurs when water carries sediment through runoff downstream, leading to significant financial damage and ecological harm. Sediment pollution clouds the water, reducing sunlight penetration and hindering the growth of natural vegetation. It also disrupts the food chain by making it difficult for animals to see their food.

By choosing to sweep instead of hose, you prevent these pollutants from entering the water drainage system. Sweeping allows you to collect and properly dispose of the debris, ensuring that it doesn't end up in our water sources. This simple act contributes to maintaining clean drinking water and preserving the habitats of aquatic life.

Additionally, sweeping your driveway and sidewalks helps conserve water. Water is a precious resource, and by reducing unnecessary usage, you are ensuring that it is available for more essential purposes.

So, the next time you want to clean your driveway or sidewalk, reach for a broom instead of a hose. It's a small action that makes a big difference in protecting our environment and water sources from the harmful effects of sediment pollution.

Use silt fences and sediment traps

Silt fences and sediment traps are widely used to reduce sediment pollution, particularly on construction sites. They are often used in tandem, along with erosion controls, to retain sediment in place where soil is being disturbed by construction processes.

Silt Fences

Silt fences are a type of temporary sediment control device used to protect water quality in nearby water bodies from sediment (loose soil) in stormwater runoff. They are typically made of a synthetic filter fabric (geotextile) stretched between wooden or metal stakes. The design and placement of the silt fence should create pooling of runoff, allowing sedimentation to occur. While water can seep through the fabric, sediment particles often block the fabric, and clean water can be released by disturbing the fabric a few hours after a storm.

Silt fences are commonly used as perimeter controls, installed before soil disturbance begins and placed down-slope from the disturbance area. They are most effective when used on level ground along the construction site's contour lines to intercept sheet flow and spread it across the fence, maximising the impoundment area.

Sediment Traps

Sediment traps are another form of temporary sediment control. They are used to intercept and remove soil and debris from sheet flow runoff on construction sites. Removal mechanisms include ponding the runoff to allow for settling, and physically filtering sediment as it passes through a sediment barrier.

Sediment traps are often used in conjunction with perimeter controls, which direct sheet flow runoff to the sediment trap for treatment. They are considered the last line of defence in a system of erosion prevention and sediment control and are usually placed near the downgradient borders of disturbed areas and soil stockpiles.

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