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MODULATING STORM DRAIN FLOWS TO REDUCE STREAM POLLUTANT CONCENTRATIONS
Citation:
Frick, W E. AND D. L. Denton. MODULATING STORM DRAIN FLOWS TO REDUCE STREAM POLLUTANT CONCENTRATIONS. Presented at First Interagency Conference on Research in the Watersheds, Benson, AZ, October 28-30, 2003.
Impact/Purpose:
A main objective of this task is to combine empirical and physical mechanisms in a model, known as Visual Beach, that
â— is user-friendly
â— includes point and non-point sources of contamination
â— includes the latest bacterial decay mechanisms
â— incorporates real-time and web-based ambient and atmospheric and aquatic conditions
â— and has a predictive capability of up to three days to help avert potential beach closures.
The suite of predictive capabilities for this software application can enhance the utility of new methodology for analysis of indicator pathogens by identifying times that represent the highest probability of bacterial contamination. Successful use of this model will provide a means to direct timely collection of monitoring samples, strengthening the value of the short turnaround time for sampling. Additionally, in some cases of known point sources of bacteria, such as waste water treatment plant discharges, the model can be applied to help guide operational controls to help prevent resulting beach closures.
Description:
Pathogen and toxic chemical concentrations above the chemical and toxicity water quality standards in creeks and rivers pose risks to human health and aquatic ecosystems. Storm drains discharging into these watercourses often contribute significantly to elevating pollutant concentrations during wet weather, especially following extended periods of dry weather over which pollutants accumulate, or after seasonal pesticides applications that cause high concentrations in retention structures and flood control basins drained by the storm drains. In many instances the discharges from the storm drains are controlled by pumps that run intermittently in response to water level elevations in the retention basins. These pumps usually run at full volume, modulated only in stepwise fashion when more than one pump serves the overflow structure. The on-off mode of operation is insensitive to conditions in the ambient flow or the effluent. Modulating storm drain flows can ameliorate the impact of pathogens or toxic residues found in the storm drain effluent by controlled and optimum mixing of the effluent and ambient streams. Plume models simulating the mixing process in real time based on continuously measured stream levels and storm drain volumes, together with variable flow pumps, could be used to blend the effluent with the receiving stream in a way that mitigates the impact of the storm drain on the environment. The Visual Plumes model is used on a storm drain discharging to urban Arcade Creek in Sacramento, California to demonstrate the potential benefits that may be realized by implementing this strategy.