Editor’s Comments: EPA’s New Construction General Permit

In February EPA released its new construction general permit, which covers construction sites of more than one acre. Although it directly applies to four states, as well as to US territories and tribal lands, many states that have their own construction permits closely follow EPA’s, so this document will have far-reaching implications for the next five years.

Just 11 days after the permit was issued, Greg Schaner of EPA’s Office of Wastewater Management spoke at the general session of EC12, the International Erosion Control Association’s annual conference. He covered the permit’s main points and fielded audience questions, and I’m passing along here a summary of his comments.

First, the thing that many people have been expecting and preparing for-a numeric turbidity limit for stormwater discharges-is the one thing the permit doesn’t include. It does, as promised, incorporate many other parts of EPA’s construction effluent guidelines, which were published in 2009 and which at that time contained a numeric effluent limit of 280 nephelometric turbidity units (NTUs) for discharges from most 10-acre-or-larger construction sites. However, EPA stayed that limit in 2011 because of problems with the way the number had been calculated. As of now, no EPA or state permits are required to include a numeric limit (although some state permits do).

According to Schaner, a numeric limit-even if EPA does issue one before this five-year permit expires-will not be added, but would instead be included in the next construction general permit. “I don’t know what’s coming with that,” he said, noting that EPA, after rescinding the 280-NTU limit, is now in an “exploratory phase.”

The new permit does, however, incorporate many other aspects of the 2009 guidelines-the narrative part of those guidelines, essentially-including those relating to erosion and sediment control provisions like natural buffers, sediment discharge controls, soil stabilization, and guidelines on the use of treatment chemicals to reduce turbidity. When proposing a numeric limit, EPA-and many others-had expected that the use of chemicals, at least for passive treatment of stormwater discharges, would increase tremendously. The agency became concerned about the use of cationic treatment chemicals and began examining the toxicity risks; the same positive charge that causes these chemicals to bind to sediment particles and makes them effective might also harm fish, Schaner noted, and some states already heavily regulate such chemicals. Even in the absence of the numeric limit, the permit calls for minimizing the use of chemicals, especially near aquatic environments; this includes using conventional erosion and sediment controls in addition to any treatment chemical, using only the amount needed for the site conditions and soil type, and ensuring those who apply the chemicals have the necessary training.

Schaner covered various aspects of the other ESC controls and answered audience members’ questions about specific interpretations. Among other provisions, the permit calls for leaving a natural buffer of 50 feet between construction activity and a surface water or, if that isn’t possible because of a narrow right of way, adding ESC controls to achieve a sediment load reduction equal to that of a 50-foot buffer. There are some exceptions-as when pre-existing development has already eliminated the buffer entirely, for example-and some flexibility for smaller sites.

Other highlights of the permit: It places increased emphasis on sediment trackout from construction sites, specifies when perimeter and additional controls must be in place, and says that sediment basins must provide enough storage for a 2-year, 24-hour storm or 3,600 cubic feet per acre drained; it also calls for withdrawing water from the surface of the basin (rather than draining from the bottom) if feasible. For soil stabilization, the permit carries forward the guidance in the 2009 rule calling for some sort of non-vegetated control to be in place within 14 days of stopping construction.

You can find a pdf of the complete permit at http://www.epa.gov/npdes/pubs/cgp2012_finalpermit.pdf.