Editor’s Comments: The Magic Number—EPA’s Effluent Guidelines

March 1, 2009

By now, most of us who will be affected by the EPA’s proposed effluent limitation guidelines are probably at least somewhat familiar with them and-pleased or irate-have debated their implications.

The guidelines, officially “Effluent Limitations Guidelines and Standards for the Construction and Development Point Source Category,” were published in the Federal Register in November; the 90-day public comment period ends on February 26, soon after this issue of Erosion Control is published.

The guidelines are intended to tighten the controls on discharges from construction sites by establishing technology-based effluent limits and performance standards. This can be achieved through the use of erosion and sediment control best management practices-as it is done now, in most places-but the document also contains some provisions lacking from most existing state and local regulations.

First, under the new guidelines, sites of 10 acres or more would need to have a sedimentation basin or something that controls sediment to the same extent. Second, for some sites-“large sites located in areas of high rainfall energy and with soils with significant clay content”-the EPA is proposing a numeric turbidity limit of 13 nephelometric turbidity units (NTUs). That number is lower than many had expected, but-contrary to what some groups had been proposing-it doesn’t apply to every site.

In places with fine silty and clay soils, this turbidity level is difficult to achieve by settling that occurs naturally in a sedimentation basin. The EPA acknowledges this and says these sites will most likely need active treatment systems, such as those that promote flocculation through the addition of polymers-chitosan or other types-followed by some type of filtration. The guidelines also mention electrocoagulation as a technology capable of reducing turbidity levels.

The sites subject to this 13-NTU limit would include those of 30 acres or more with an average soil clay content of more than 10% and a rainfall erosivity factor (the “R” factor from the Revised Universal Soil Loss Equation) of 50 or greater. (If you view the complete document, see option 2 for more details on which sites would be subject to the numeric limit. The guidelines and related documentation are available online at www.epa.gov/waterscience/guide/construction.)

The EPA estimates that meeting the new standards will cost about $1.9 billion per year, and the document includes a detailed discussion of how it arrived at this figure. The agency also considered other scenarios (see option 3 in the full guidelines) that would essentially require all sites where more than 10 acres of land are disturbed to meet a numeric limit. The estimated cost to achieve this is double what the EPA is actually proposing, or $3.8 billion per year.

In upcoming issues, we’ll have opinions from experts in the field on the guidelines (including some thoughts on enforcement). I invite you to add your thoughts-on the overall guidelines, their enforceability, or the cost to implement them. Please join the discussion at www.erosioncontrol.com.

About the Author

Janice Kaspersen

Janice Kaspersen is the former editor of Erosion Control and Stormwater magazines.