The Cost and Effectiveness of Stormwater Management Practices Final Report

With the implementation of the United States Environmental Protection Agency’s (USEPA) National Pollution Discharge Elimination Systems (NPDES) Phase I and II programs, strong interest has developed in the area of water quality treatment of stormwater runoff. While little is known about the cost effectiveness of available stormwater treatment technologies, called Stormwater Management Practices (SMPs) in this report, municipal agencies are now, or soon will be, required to meet certain pollutant removal criteria based on the Phase I and II regulations. Of primary concern are nutrients such as phosphorus (P) and nitrogen (N), which are just one of the pollutant categories being targeted for removal from stormwater runoff. Excess nutrients can initiate large algae blooms that generate negative aesthetic and eutrophic conditions in receiving lakes and rivers (USEPA, 1999a). In inland water bodies phosphorus is typically the limiting nutrient (Schindler, 1977) and can be contributed to stormwater from various sources such as fertilizers, leaves, grass clippings, etc. (USEPA, 1999a). Another pollutant of primary concern in stormwater is dirt, sand, and other solid particles which are commonly quantified by measuring the Total Suspended Solids (TSS) of a water sample. TSS can severely and negatively impact an aquatic environment. The solids increase turbidity, inhibit plant growth and diversity, affect river biota and reduce the number of aquatic species (Shammaa et al., 2002). Also, organic suspended solids can be biologically degraded by microorganisms in a process which consumes oxygen, which is important to the aquatic biota.