Preventing Stormwater Pollution: Best Practices For Construction Site Operators

Stormwater runoff is a significant environmental concern, especially on construction sites where land disturbance can lead to erosion and the release of harmful contaminants into nearby water sources. Construction site operators play a crucial role in preventing stormwater pollution by implementing effective stormwater management strategies. This includes understanding the causes of stormwater pollution, developing and adhering to stormwater pollution prevention plans (SWPPP), and adopting best management practices (BMPs) to control and mitigate the environmental impact of stormwater runoff.

Implement a Stormwater Pollution Prevention Plan (SWPPP)

Implementing a Stormwater Pollution Prevention Plan (SWPPP) is a crucial step in ensuring construction site operators effectively prevent stormwater pollution. Here are the key components and considerations for developing and implementing an SWPPP:

Understanding Stormwater Runoff

Firstly, it is essential to comprehend the nature of stormwater runoff. When precipitation occurs, water flows over the construction site, collecting pollutants such as sediment, debris, chemicals, and nutrients. This contaminated water then drains into nearby storm sewer systems or directly into bodies of water like rivers, lakes, or coastal waters. Understanding this process is fundamental to designing effective pollution control measures.

Site Assessment and Planning

Before initiating construction, a thorough site assessment is necessary. Identify potential sources of pollution and areas vulnerable to erosion and sedimentation. This includes recognizing the presence of hazardous materials, chemicals, and waste products that could contaminate stormwater. Additionally, consider the size and location of the site, as well as the specific construction activities that will take place. All these factors will influence the design of your SWPPP.

Implementing Control Measures

Install appropriate erosion and sediment controls, such as silt fences, sediment traps, erosion control blankets, and storm inlet drains. These measures help slow down the velocity of stormwater runoff, allowing for the filtration and removal of harmful pollutants. Ensure that any stockpiles of sand, gravel, topsoil, or mulch are securely stored on-site and not on roads or footpaths, where they can be washed away by rainwater.

Waste Management and Housekeeping

Establish proper waste management practices to minimize the risk of pollution. Keep the site clean and properly dispose of any waste, including litter, construction debris, and hazardous materials. Wash any equipment used for painting, plastering, or concreting on-site, ensuring that the wash-up area is located away from stormwater drains to prevent contamination.

Employee Training and Education

A critical aspect of a successful SWPPP is training your employees on proper waste management practices and erosion control measures. Ensure they understand the importance of preventing stormwater pollution and their role in implementing the SWPPP. Educated employees can become your allies in minimizing the environmental impact of your construction project.

Compliance and Permits

Familiarize yourself with local and federal regulations regarding stormwater pollution. In the United States, the Environmental Protection Agency (EPA) requires construction sites disturbing more than an acre of land to obtain a Clean Water Act permit and develop an SWPPP. Check with your local council or environmental agency to understand the specific requirements and permits needed for your project.

Control erosion and sediment

Construction site operators can employ various strategies to control erosion and sediment, thereby preventing stormwater pollution. Here are some detailed and instructive guidelines:

Planning and Site Management

Site planning and management are crucial to controlling erosion and sediment. Construction managers should aim to minimise the size of bare soil areas and the length of time disturbed areas are exposed to the elements, especially for long, steep slopes with easily erodible soils. This can be achieved by carefully sequencing construction activities to limit the area disturbed at any given time. Additionally, implementing measures to divert or control the volume and location of water flow onto the site from adjacent areas is essential.

Soil Cover and Vegetation

Covering bare soil with vegetation, mulch, erosion control blankets, turf reinforcement mats, gravel, rock, or plastic sheeting can effectively prevent erosion. Vegetation, such as native grasses, and mulch help stabilise the soil by absorbing the energy from rainfall and runoff, providing protection, and promoting vegetation growth.

Sediment Control Structures

Implementing sediment control practices, such as silt fences, drop inlet screens, and fiber rolls, is essential. These structures physically trap soil particles by filtering sediment-laden runoff or allowing sediment to settle in temporary ponds, traps, or small pools created by berms, silt fencing, or inlet protection dikes.

Inlet Protection

Inlets to the stormwater conveyance system must be protected. This can be achieved using fiber logs, including straw, wood, or coconut fiber logs, compost logs, and rock logs, which slow down water flow and filter sediment.

Vehicle Tracking Control

Vehicles can carry mud from construction sites onto roads, which can then be washed into the stormwater system. Rock construction entrances, made of clear aggregate rocks, help remove sediment from vehicle tires. Periodic cleaning or replacement of these rock entrances is recommended.

Temporary Seeding and Erosion Control Blankets

Temporary seeding allows plants to stabilise the soil through vegetation and root growth. Rye grass, winter wheat, and oats are commonly used for this purpose. Erosion control blankets, made of netting layered with natural or man-made fibers, shelter the soil from rainfall and runoff while retaining moisture, aiding in plant establishment.

Sediment Basins and Ponds

Constructing temporary sediment basins or ponds can capture runoff, slowing down water flow and allowing sediment to settle, thereby preventing it from entering stormwater systems.

By implementing these measures, construction site operators can effectively control erosion and sediment, minimising the environmental impact of stormwater runoff and protecting local water sources and ecosystems.

Prevent pollution from chemicals

Construction site operators can take several measures to prevent stormwater pollution from chemicals. Here are some detailed and direct instructions:

Firstly, it is crucial to understand the sources of chemical pollutants on construction sites. Chemical pollutants can come from various sources, such as paints, oils, greases, construction chemicals, and building materials like stucco. Identifying these sources is essential for implementing effective prevention measures.

Secondly, construction site operators should ensure that wash-up areas for activities like painting, plastering, and concreting are located away from stormwater drains. By doing so, they can prevent chemical wash-off from directly entering the stormwater system. This includes properly managing and treating wastewater from concrete washout, paint washout, and the cleaning of equipment and vehicles.

Thirdly, implementing erosion and sediment controls is vital. While sediment is not inherently toxic, it can increase water turbidity, blocking sunlight and harming aquatic life. Effective sediment controls, such as silt fences, sediment traps, erosion control blankets, and storm inlet drains, can help capture pollutants, including chemicals, and prevent them from entering stormwater runoff.

Additionally, proper storage and protection of chemicals and other materials on-site are essential. This includes storing stockpiles of sand, gravel, topsoil, and mulch on-site and away from roads or footpaths. By keeping these materials contained, operators can reduce the risk of them being washed into stormwater systems during rain or storms.

Furthermore, construction site operators should implement measures to control stormwater runoff. This can include the use of retention ponds, sedimentation basins, or wetland systems that capture and treat stormwater before it is discharged. These systems can help remove pollutants, including chemicals, and prevent them from reaching local water bodies.

Lastly, construction site operators should ensure that they are compliant with all local and federal regulations regarding stormwater pollution. In the United States, for example, the Environmental Protection Agency (EPA) requires construction sites disturbing more than an acre of land to obtain a Clean Water Act permit and develop a Stormwater Pollution Prevention Plan (SWPPP). These plans outline specific measures to control stormwater runoff and prevent pollution from chemicals and other contaminants.

Protect stockpiles of sand, gravel, topsoil and mulch

Construction site operators play a crucial role in preventing stormwater pollution, especially as land disturbances can lead to erosion and the release of harmful contaminants into nearby water bodies. To protect stockpiles of sand, gravel, topsoil, and mulch, several measures can be implemented:

Firstly, the location of stockpiles is crucial. It is important to avoid placing stockpiles over other parts of the deposit from which future extraction is intended. This is to prevent the costly process of having to relocate the stockpile. Additionally, the location of stockpiles should be chosen to facilitate safe and efficient operations.

Secondly, the stockpiles should be protected from stormwater runoff. Construction site operators can implement measures such as building a system of culvert pipes, ditches, and collection pools to effectively manage surface runoff and prevent erosion. This is essential as stormwater can carry contaminants from the stockpiles into nearby water bodies.

Thirdly, fences and gates around the stockpiles can serve multiple purposes. They can help deter trespassing, prevent livestock intrusion, discourage garbage dumping, and enhance security by reducing theft. Additionally, these structures can provide legal protection for the developer in the event of accidents.

Furthermore, it is important to ensure that the stockpiles are not visible from public roads for privacy and safety reasons. This can help minimize the risk of unauthorized access and potential hazards associated with the stockpiled materials.

Lastly, the stability of sand and gravel stockpiles should be carefully managed. The face of the stockpile should not exceed a safe height, typically no higher than 20 to 25 feet, to ensure safe extraction. For thicker deposits, a technique called "benching" can be employed, where benches or steps are created to facilitate safer and more economical extraction and subsequent land restoration.

Control concrete waste

Concrete waste is an inevitable part of construction, with wastage levels typically estimated at 3-5%. However, waste levels exceeding this range can increase project costs and hinder progress, so it is crucial to implement measures to control concrete waste.

Firstly, effective planning is essential to minimising concrete waste. Before commencing concreting, a concrete pour card should be prepared to determine the precise quantity of concrete required. The production of concrete should be aligned with the pouring speed to prevent concrete from setting before it is placed in the formwork. Estimating the approximate concrete quantity needed and informing the batch plant operator when the work is almost completed will help to prevent excess concrete supply.

During concrete placement, unforeseen issues may arise that temporarily halt pouring. In such cases, the supervisor must promptly inform the batching plant operator to pause production and supply. If excess concrete is produced, it can be used elsewhere to avoid unnecessary waste.

To effectively control concrete waste, site supervisors must be well-trained to manage the site and address any issues that may lead to increased waste. Implementing proper planning procedures before and during the concrete placement process is vital to minimising waste and ensuring the efficient progression of the construction project.

Frequently asked questions