Construction activities, such as clearing, excavating, and grading, significantly disturb the land. The disturbed soil, if not properly managed, can easily be washed off construction sites during storms. Pollutants discharged from construction sites, which includes sediment, turbidity, and nutrients, can adversely affect water quality and water resources.
EPA has had requirements for controlling stormwater discharges from construction sites since 1990. Existing regulations require discharges to be covered by an NPDES permit, and to implement control measures. The new requirements are technology based, and will require construction site owners and operators to implement , at a minimum, a range of erosion and sediment control practices and stormwater pollution prevention practices. In addition, for the first time larger sites will be subject to monitoring requirements and enforceable numeric limits.
Most of the new requirements go into effect on February 1, 2010. These requirements applied to construction sites that are one acre or more. The requirements are:
Erosion and Sediment Controls.
At a minimum, these controls must:
- Control stormwater volume and velocity within the site to minimize soil erosion.
- Control stormwater discharges, including peak flow and total volume, to minimize erosion at discharge outlets and downstream receiving points.
- Minimize the amount of soil exposed during construction activity.
- Minimize sediment discharges from the site.
- Provide and maintain natural buffers around surface waters and direct stormwater to vegetated areas, unless infeasible.
- Minimize soil compaction and, unless infeasible, preserve top soil.
- Stabilization of disturbed areas must, at a minimum, be initiated immediately when earth disturbing activities have permanently ceased on any portion of the site, or temporarily ceased on the portion of the site and will not resume for a period exceeding 14 days.
- Discharges from dewatering activities, including trenches and excavation areas, are prohibited unless managed by appropriate controls.
Pollution Prevention Measures.
At a minimum, these measures must:
- Minimize the discharge of pollutants from equipment and vehicle washing and other wash waters.
- Minimize exposure of building materials, construction waste, and other materials present on the site to precipitation.
- Minimize the discharge of pollutants from spills and leaks and implement spill and leak prevention and response procedures.
- Wastewater from washout of concrete, unless managed by an appropriate control.
- Wastewater from cleaning of stucco, paint, curing compounds and other construction materials.
- Fuels, oils, and other materials used in vehicle and equipment operation and maintenance.
- Soaps or solvents used in vehicle and equipment washing.
- When discharging from basins and impoundments, utilize outlet structures that withdraw water from the surface, unless infeasible.
In addition to the above requirements, for the first time certain construction sites will be required to comply with a numeric limit for their stormwater discharges. The numeric limit is for turbidity, and the average discharge for any day must not exceed 280 units. This numeric limit is phased in for construction sites. The numeric limit goes into effect on August 1, 2011 for construction sites that disturb 20 acres or more of land. The numeric limit goes into effect on February 2, 2014 for construction sites that disturb 10 acres or more of land.
As is normally the case, these EPA requirements establish a baseline that must be met around the Country. State and local agencies are free to have more stringent requirements.