Abstract 

For the past three decades, municipalities in the United States have successfully addressed pollution in the watershed by collecting and treating their wastewater. Currently, all municipalities provide secondary treatment and in some cases tertiary treatment. Industries provide the best available and most practicable treatment. This has had great benefits—more rivers are meeting water quality standards and public health is being protected from waterborne disease. The challenge now is to address pollution associated with storm water runoff.

It is less costly to prevent the generation of polluted runoff than to treat it. Today, many municipalities are implementing low-cost best management practices (BMPs) that prevent runoff. The lowest-cost BMPs, termed nonstructural or source control BMPs, include practices such as limiting pesticide use in agricultural areas and retaining rainwater on residential lots (currently termed “low-impact development”).

High-cost BMPs involve building a structure to store storm water until it can be discharged into nearby receiving water. Construction is more costly, especially in areas where land prices are high. The most commonly used structural treatment BMPs, and the ones considered in this document, are:

• Ponds – wet ponds (retention ponds), dry ponds (notably extended detention ponds), and infiltration basins
• Vegetated biofilters –vegetated filter strips, bioretention cells and grass swales
  (grass swales include traditional ones, those with media filters, and wet swales)

The state of the science is such that the performance of treatment BMPs shows promise regarding pollutant removal and existing designs vary. This document presents factors that should be considered in the design of treatment BMPs to improve water quality.

Contact

Michael Borst

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