June 2011

Letter to the Editor

A table in the article “Designing BMPs for Drought” in the January/February 2011 issue—specifically Table 1, Typical BMP Removal Rates on page 49—misrepresents the performance of permeable pavements. This table indicates that permeable pavements offer no water-quality control; no removal of total suspended solids, total nitrogen, or total phosphorus; low fecal removal ability; and medium ability to perform in high temperatures.

The term “permeable pavements” is generally understood to mean porous asphalt, pervious concrete, permeable interlocking concrete pavements (PICP), and a few proprietary products. These materials are placed over open-graded aggregate bases that reduce pollutants. This table does not represent the results of dozens of research papers, including several presented at StormCon conferences!

I am a member of the American Society of Civil Engineers (ASCE) Technical Committee on Permeable Pavements. We are developing a state-of-the-art practice manual for ASCE members on a range of permeable pavements, which includes information on pollutant reductions from academic and agency research. The committee has collected and reviewed hundreds of research papers on the pollutant reductions from permeable pavements. Many of these papers can be accessed via the Internet. Moreover, several state and local stormwater agencies offer credits for these pollutants when permeable pavement is specified as a best management practice (BMP).

While the article brings forward good points about how to design bioretention in areas subject to drought in the Southeast, permeable pavements consistently offer pollutant reductions in a range of climates including those in the Southeast.

On a related subject, I was pleased to read the favorable review of PICP in the March/April issue article “Assessment of Stormwater BMP Cost Effectiveness” by Ben Urbonas and Christopher Olson. The article suggests taking a comprehensive view of cost accounting for PICP that includes savings from using less land. We appreciate your continued coverage on PICP as it is an essential tool among several to reduce runoff volumes and pollutants through infiltration and filtering.

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