Management and control technology for urban stormwater pollution
A number of proven and promising measures for managing and controlling water pollution caused by urban runoff and combined sewer overflows are re viewed in this paper to help guide planners and design ers in developing control programs suited to their local needs. This review summarizes a series of nationwide evaluations of urban stormwater management ap proaches, methodologies, and processes, sponsored by the U. S. Environmental Protection Agency (EPA).1"5 The evaluations include recent efforts to focus on most promising technology, and to identify receiving water, socioeconomic, and environmental impacts and benefits, in addition to assessments of the control measures' per formance, costs, and effectiveness. Urban stormwater problems are characterized by surface runoff events that are intermittent, unpredict able, and vary greatly with time, location, and in mag nitude. They are also characterized by a variety of pol lutants that may originate from a number of different types of sources. Control strategies, therefore, need to be specifically planned, evaluated, and designed to ac count for local characteristics. Clearly, they will differ markedly from measures used to control dry weather pollution. Wet weather control measures are classified into two broad categories: structural measures, and best man agement practices (BMPs) Structural measures are generally end of pipe facilities designed to control vol ume and pollution from stormwater and combined sewer overflows (CSOs) BMPs are nonstructural and low struct ral management alternatives for controlling urban ru off pollution; they include institutional and source control measures. The adoption and documentation of BMPs lags sig nificantly behind that of the structural alternatives for CSOs, in spite of the apparent greater cost effectiveness of BMPs. In part, this has resulted from the past em phasis of the EPA research and development program, which principally focused on controlling CSO problems in larger cities. Recent studies, however, indicate that pollution from urban runoff and other non point sources has caused major receiving water problems, including nutrient enrichment, introduction of toxic materials, turbidity, and sediment deposition.4,6"9 These problems arise with all types of development, both urban and rural. The magnitude of the urban runoff problem, therefore, may be comparable to the CSO problem, particularly whe floo ing and erosion impacts are con sidered. All costs are based on an Engineering News Record (ENR) Construction Cost Index of 3 000 (1913 100) approximating June 1979 dollars, for comparison pur poses.