USEPA Proposes Technology-Based Effluent Limits for Construction Sites

              On November 19, 2008, USEPA sent to the federal register a proposed rule to control stormwater discharges from construction sites. 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.  The proposed rule would require all construction sites to implement a range of erosion and sediment control best management practices (BMPs) to reduce pollutants in stormwater discharges.

Construction sites disturbing ten or more acres at a time would also be required to install sediment basins to treat their 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,* their stormwater discharges would be required to meet a numeric limit on the allowable level of turbidity (13 NTUs).  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).   In order to meet the proposed numeric turbidity limit, USEPA advises that many sites would need to use chemical treatment and filtration of their stormwater discharges.  The turbidity limits will not apply, however, in the event a storm event causes a pond to overflow if the pond has been designed, constructed and operated to contain the runoff from a 2 year, 24 hour storm event. 

This article was authored by Robert G. McLusky, Jackson Kelly PLLC. For more information on the author see here.

* These requirements apply to construction activities located at a site with 10 percent or greater by mass of soils less than 2 microns in diameter that has an annual rainfall erosivity factor (R factor) of 50 or higher as defined by the Revised Universal Soil Loss Equation (for construction activity located in Alaska or a U.S. territory where the R factor applicable to the activity has not been calculated, the 30-year average total annual precipitation of 20 inches or more shall be used in place of the R factor).