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COMBINED SEWER OVERFLOW - BALANCING FLOW FOR CSO ABATEMENT
Citation:
Gorndran, A., R Field*, K. Dunkers, AND D. Moran. COMBINED SEWER OVERFLOW - BALANCING FLOW FOR CSO ABATEMENT. WATER ENVIRONMENT AND TECHNOLOGY. Water Environment Federation, Alexandria, VA, 43(5):54-58, (1991).
Impact/Purpose:
information
Description:
Instead of using conventional storage units, e.g., reinforced concrete tanks and lined earthen basins, which are relatively expensive and require a lot of urban land area, the in-receiving water flow balance method (FBM) facilities use the receiving water body itself for storage volume. The FBM facilities receive and contain urban-storm-induced discharges between flexible plastic, e.g., fiberglass reinforced PVC (polyvinyl chloride) curtains suspended from floating wooden pontoons. The curtains are anchored to the receiving-water bottom by concrete weights. he Flow Balance Method of storage is low cost due to its low-cost materials of construction, i.e., plastic and wood; installation time, i.e., several days to weeks; and the absence of land requirements. Studies show that costs could be about 5 to 15 percent and 40 to 50 percent of conventional concrete tank costs for freshwater and saltwater applications, respectively (without including land costs). The FBM facilities have been operating successfully for approximately ten years for control of separate stormwater entering relatively quiescent freshwater lakes in Sweden, and are able to take ice and wind loads without adverse impact. The objective of the project which this paper discusses is to demonstrate a facility for Combined Sewer Overflow (CSO) storage in a harsh estuarine/marine site having tidal exchange, freezing, and coastal storm phenomena. The prototype demonstration facility located in Fresh Creek, a tributary of Jamaica Bay in Brooklyn, New York, U.S.A. started operation in November 1988. The evaluation includes CSO capturing efficiency under the impediments and flow saltwater and freshwater density differences and curtain leakage; structural ability to endure the harsh coastal marine environment; and floatables and settleable solids removal effectiveness. Interim data (including that from salinity profiling) from several storm-flow occurrences indicates that the saltwater-freshwater stratification phenomenon is enabling the facility to operate effectively and detailed results of the evaluation are presented.
