Construction and Its Impact on Stormwater
Dirt Can Hurt
- Dirt and other materials from construction projects are harmful to local creeks and aquatic life (fish and insects). Dirt can smother creek beds where fish and insects breed and hide.
- Construction projects can release dirt and construction materials into the storm drains, which flow directly to the creeks.
- Local, State, and Federal laws require construction projects to minimize the discharge of pollutants, like dirt, from leaving the construction site.
- If you are disturbing the ground, it is important to do your part in protecting stormwater and creeks by implementing Best Management Practices.
- Construction Best Management Practices, also called BMPs, include a variety of measures that help to minimize the discharge of dirt and other pollutants. All projects need to implement basic BMPs to protect stormwater and creeks.
- If your project requires a permit (e.g., building or grading permits) from the City, you may need to develop an Erosion and Sediment Control Plan.
- An Erosion and Sediment Control Plan or ESCP establishes the site-specific plan of actions and BMP that you will take to prevent dirt and other construction materials and waste from leaving your site. You will need to submit your ESCP for City approval with your permit application.
- An ESCP needs to include an effective combination of erosion controls and sediment control to prevent dirt from leaving the site. The ESCP also needs to include good housekeeping practices to prevent construction materials and waste from leaving the site.
Stormwater Pollution Prevention Plans
Larger projects, that disturb an acre or more of land, need to obtain coverage under the State Water Board’s General Permit for Stormwater Discharges associated with construction activities. This permit is commonly called the Construction General Permit or CGP.
If your project will disturb an acre or more of land you will need to obtain coverage under the CGP and develop a Stormwater Pollution Prevention Plan (SWPPP) that meets the requirements of the CGP.
Briefly, a SWPPP is a detailed site-specific plan to protect stormwater quality leaving the site. SWPPPs must be prepared by qualified individuals and assess the pollutant potential of the project and sensitivity of the receiving waters. A SWPPP needs to include the detailed BMP implementation plan as well as a construction site monitoring program of inspections and runoff sampling.
More details on the CGP requirements and SWPPPs can be found on the State Water Board’s Construction Stormwater Program page.
If your project is subject to the CGP, you will need to submit your SWPPP to the City with your permit application or application for development approvals. Before you start construction you will need to provide proof that you have obtained CGP coverage by providing your Waste Discharger Identification Number
Helpful Hints and Tips for Protecting Stormwater Quality During Construction Activities
- Fully implement your BMPs year-round.
- Implement an effective combination of erosion and sediment controls.
- Prevent erosion by stabilizing disturbed soil, paying particular attention to exposed slopes.
- Inspect your site, especially before and during storm events to make sure your BMPs are installed properly and are working effectively.
- Keep BMP replacement supplies at the site to make repairs and handle unexpected events.
- Train your staff and contractors on the BMPs and how to protect stormwater.
- Maintain your construction entrance and exit points to minimize tracking and sweep the streets.
- Maintain drain inlet and perimeter protection year-round.
- Prevent discharges of anything but clean stormwater to the storm drains.
- Protect stockpiles by covering them and surrounding them with perimeter controls.
- Make sure you are prepared for the start of the rainy season
Minimum Control Measures for Small Construction Projects
Remember that storm drains and runoff flow directly to our creeks and rivers untreated. Taking minimum control measures for construction projects as noted below helps protect our waterways and their aquatic life.
Select an effective combination of control measures from each category, Erosion Control, Sediment Control, and Good Housekeeping. Control measures shall be continually implemented and maintained throughout the project until activities are complete, disturbed areas are stabilized with permanent erosion controls, and the local agency has signed off on permits that may have been required for the project. Inspect and maintain the control measures before and after rain events, and as required by the local agency or state permit.
There are 16 activities that can be categorized in to three areas; Erosion Controls, Sediment Controls, and Good Housekeeping.
Erosion Controls
Source control practices that protect soil and prevent soil particles from being detached by rainfall, flowing water, or wind.
1 – Scheduling: Scheduling allows you to plan activities when there is a lower chance of rain and to plan for BMP installation as the activities progress.
2 – Preserve Vegetation & Creek Set Backs: Existing vegetation is the best form of erosion control, doesn’t cost money to install, and requires little maintenance. Preserving vegetation between the site and creeks is especially important and required in some situations.
3 – Soil Cover: Soil cover products, like hydromulch, replace the erosion control benefit of vegetation removed during construction. These products can be quickly deployed over large (or small) disturbed areas for temporary protection and can be incorporated into final stabilization.
4 – Soil Preparation/Roughening: This practice prepares the soil for growing vegetation. Mechanically roughening the soil slows the water down and provides pockets that promote germination. Soil prep also includes testing the soil to identify if any amendments are needed to promote growth.
5 – Erosion Control Blankets: Soil cover products, like erosion control blankets, replace the erosion control benefit of vegetation removed during construction. These products are used for temporary projection and can be incorporated into final stabilization.
6 – Revegetation: Revegetation re-establishes vegetation on the areas of the site disturbed by construction to prevent erosion. It is part of the final stabilization of the site but may also be needed for temporary protection during the project.
Sediment Controls
Practices that trap soil particles (sediment) after they have been detached by rainfall, flowing water, or wind.
7 – Tracking Controls: Tracking controls are a suite of practices that limit the amount of dirt and mud tracked from a project into the street. Keeping dirt out of the street helps to keep it out of the storm drains and reduces complaints from neighbors.
8 – Fiber Rolls: Fiber rolls intercept runoff, reduce its velocity, and trap sediment behind the roll. They also reduce the length of a slope, which reduces sheet and rill erosion.
9 – Silt Fence: Silt fences detain (pond) water promoting sedimentation behind the fence.
10 – Drain Inlet Protection: Drain Inlet Protection (DI) is used as a last line of defense. It temporarily ponds water at the drain inlet, allowing some sediment to settle out. Some forms of DI protection can filter sediment during low flow events.
Good Housekeeping
Practices that prevent pollution by limiting the exposure of construction materials with rain, flowing water, or wind. These practices involve keeping a clean and orderly construction site.
11 – Concrete Washout: These practices prevent the discharge of high pH concrete wastewater into the ground or storm drains.
12 – Stockpile Management: These practices and procedures protect loose stockpiled materials from washing or blowing off the projects site.
13 – Hazardous Material Management: These practices prevent the discharge of hazardous materials by using proper storage of materials and wastes, and by minimizing the quantity of materials stored.
14 – Sanitary Waste Management: Proper management of sanitary waste facilities, e.g., portable toilets, prevents the discharge of wastewater to the ground and storm drains.
15 – Equipment and Vehicle Maintenance: These practices prevent discharges of vehicle fluids and wastes by limiting on-site maintenance and using practices a to contain and clean up small leaks and drips.
16 – Litter and Waste Management: These practices prevent the discharge of trash and wastes from the project site by using covered and contained trash cans and bins.