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ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: STORMWATER SOURCE AREA TREATMENT DEVICE: STORMWATER MANAGEMENT INC., STORMSCREEN� TREATMENT SYSTEM
Citation:
NSF INTERNATIONAL. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: STORMWATER SOURCE AREA TREATMENT DEVICE: STORMWATER MANAGEMENT INC., STORMSCREEN� TREATMENT SYSTEM. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-05/099, 2005.
Description:
Verification Testing of the Stormwater Management, Inc. StormScreen treatment technology was performed during a 12-month period starting in May, 2003. The system was previously installed in a city-owned right-of-way near downtown Griffin, GA., and is a device for removing trash, debris, and large suspended particulate matter at high flow rates. The system consists of an inlet bay, cartridge bay, and outlet bay, housed in a 16 ft. by 8 ft. precast concrete vault. The inlet bay serves as a grit chamber and provides flow transition to the cartridge bay where the water is screened and discharged through flumes to the outlet bay and discharge pipe. The StormScreen has 20 radial flow cartridges equipped with screens with a standard opening size of 2.4 mm. Each cartridge has a design flow capacity of 224 gpm for a total capacity of 4,488 gpm. The City of Griffin requires that all storm drain systems be designed to accommodate the 25-yr storm. For a 25-yr storm event, a 5.42 min time of concentration was determined for the drainage basin, generating a peak runoff of 46.80 cfs. Verification testing consisted of taking samples during a minimum of fifteen qualified storm events requiring: a total rainfall depth of 0.2 in. (5 mm); flow through the device was successfully measured and recorded over the duration of the runoff period; a minimum of six hours between qualified events; and, visual observations noted in the log for the inlet bay, cartridge bay and effluent chambers. The fifteen events used for this verification covered a wide range of storms with total rainfall amounts varying from 0.22 in. to 3.06 in. Flow data and observations indicated that the maximum flow through the StormScreen during the verification test was considerably lower than the design flow capacity. In at least nine events, some bypass occurred at runoff flow rates less than the design capacity of the StormScreen system. Flow data from the effluent showed that the system was typically treating between 150 and 250 gpm when the system was flowing at a steady rate. Each event had a peak discharge rate (typically 300 to 600 gpm) that was higher than the steady rate, but still significantly below the design flow capacity of 4,488 gpm. An accumulation of trash and debris was observed in the cartridge bay after every event as was sediment and hydrocarbon sheen. By the end of the test, the screens were occluded by a significant quantity of organic detritus and fine clay. Based on the findings of the ETV test and subsequent tests conducted by the vendor, occlusion of the cartridge screens by organic detritus and clay apparently resulted in the decrease of the StormScreen system’s flow capacity at this installation. The test concluded that a more frequent maintenance schedule, including cleaning the cartridge screens, would be required to achieve a higher flow capacity for applications with an expected high loading of organic detritus and fine clay.