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CONSIDERATIONS IN THE DESIGN OF TREATMENT BEST MANAGEMENT PRACTICES (BMPS) TO IMPROVE WATER QUALITY
Citation:
O'Connor*, T P. AND D A. Sullivan*. CONSIDERATIONS IN THE DESIGN OF TREATMENT BEST MANAGEMENT PRACTICES (BMPS) TO IMPROVE WATER QUALITY. Presented at Water Environment Federation TMDL 2003 Specialty Conference, Chicago, IL, 11/16-18/2003.
Description:
Today, many municipalities are implementing low-cost best management practices (BMPs). The lowest cost BMPs, termed non-structural or source control BMPs, include practices such as limiting pesticide use in agricultural areas. There are a set of higher cost BMPs, which involve building a structure of some kind to store stormwater until it can be discharged into a nearby receiving water. The three most commonly used structural treatment BMPs that will be discussed in the presentation are ponds (detention/retention), vegetated biofilters (swales and filter/buffer strips) and constructed wetlands.
Historically, structural BMPs were employed to capture peak flows, assist in local drainage, and manage the quantity of runoff produced during wet-weather flow (WWF), i.e., flood control. Current design typically still focuses on rainfall events that range from 2 to 10 inches of daily rainfall and occur at much longer return periods ranging from 2 to 100-year. These storms may contain significant pollutant loads, but their contribution to the annual average pollutant load is really quite small due to the infrequency of their occurrence. In addition, longer periods of recovery are available to receiving waters between larger storm events allowing receiving water systems to flush themselves and the aquatic environment to recover.
Water quality control of urban runoff is still a relatively new and developing technology. The addition of water quality considerations in the design of BMPs has introduced a new dimension to the traditional hydrologic considerations for BMP design. Water quality considerations have created a shift from flood events to a continuous long-term rainfall-runoff BMP design volume approach and the pollutant loads associated with these volumes.