The U.S. Environmental Protection Agency (EPA) is seeking comments on its proposed guidelines to control the discharge of pollutants from construction sites. The proposal would require all construction sites to implement erosion and sediment control best management practices (BMPs) to reduce pollutants in stormwater discharges.

In addition, for certain large sites located in areas of the country with high rainfall intensity and soils with a high clay content, stormwater discharges from a construction site would be required to meet a numeric limit on the allowable level of turbidity. To meet the proposed numeric turbidity limit, many sites would need to treat and filter stormwater discharges.

The proposed rule is intended to work in concert with existing state and local programs, adding a technology-based "floor" that establishes minimum requirements that would apply nationally. According to EPA, once implemented, these new requirements would significantly reduce the amount of sediment and other pollutants discharged from construction sites.

Construction sites disturbing 10 or more acres at a time would also be required to install sediment basins to treat stormwater discharges. In addition, if sites 30 acres or larger are located in areas of the country with high rainfall intensity and soils with a high clay content, stormwater discharges would be required to meet a numeric limit on the allowable level of turbidity.

The turbidity limit is intended to remove fine-grained and slowly settling or non-settleable particles contained in stormwater. Particles such as clays and fine silts contained in stormwater discharges from construction sites typically cannot be effectively removed by conventional stormwater BMPs (such as sediment basins). To meet the proposed numeric turbidity limit, EPA says, many sites would need to use chemical treatment and filtration of stormwater discharges.

Information on the proposal is available onine at www.epa.gov/ost/guide/construction.