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Stormwater Management

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file icon Real Life Solutions to SUDShot! 04/20/2005
Authors
Alex Stephenson
Abstract
A novel integrated system providing ‘hard’ or engineered solutions to SUDS, Source Control and Rainwater re-use is described. The system is made up of several facets; a stormwater storage element (Stormcell
file icon Providing Engineered Solutions to the Challenges of SuDShot! 06/17/2004
Author
Mr Alex Stephenson
Abstract
A novel integrated system providing hard engineered solutions to SuDS, Source Control and Rainwater re-use is described. The system is made up of four key facets; a flow control / attenuation element (Hydro-Brake
file icon Providing a sustainable urban village communityhot! 09/21/2007
Authors
A.G. Stephenson, S. Boots
Abstract
The problems surrounding how we deal with stormwater run-off and issues such as drought, flooding and water pollution have been well publicised in recent years fuelled, to great extent, by the growing consciousness of climate change. This has lead to an increasing number of guidance documents and initiatives which help explain how we can adopt a sustainable and more holistic approach to stormwater management. There are many methods available and approaches in the SUDS ‘toolbox’ but all too often designers are restricted to ‘soft’ options or what have become known as traditional SUDS, failing to consider some of the innovative proprietary solutions that have been used for many years which have provided very robust, cost effective and reliable answers. This paper will use an interesting case study to demonstrate how these systems have been used in conjunction with traditional SUDS options resulting in a complimentary, holistic solution helping create a whole sustainable community.
file icon PROTOCOL FOR ASSESSING SEDIMENT RETENTION IN STORMWATER TREATMENT CHAMBERShot! 07/26/2006
Authors
Kwabena Osei, Robert Andoh and Lisa Glennon
Abstract
In approving stormwater BMPs, regulators usually review sediment removal data as the basis for their decisions. One factor that is usually overlooked is the ability of a treatment device to retain captured material in the event of high flow rates. Lately, some agencies are requiring vendors to indicate washout prevention of their stormwater treatment systems. However, no standard protocol exists that measures how much of previously captured pollutant is resuspended and carried downstream of the treatment device during high flows.

This paper discusses an effective test protocol for evaluating the sediment retention efficiency of proprietary stormwater treatment systems. The sump of a full-scale treatment device is filled with a known mass of sediment or sediment tracer. The unit is run at steady-state for a specified duration that exceeds several multiples of its effective detention time. Repeated tests are undertaken at different flow rates and the amount of material retained in the device for each flow rate is determined. The sediment retention efficiency is then calculated based on a comparison between mass of material retained in the sump after running flows through the unit and the original mass of material deposited in the sump.

Test data using this protocol for different device configurations are discussed and this highlights the importance of chamber geometry and hydrodynamic regime on the sediment retention efficacy of stormwater treatment devices.

file icon Pollutants Washout - The Missing Dimension in Urban Stormwater Treatmenthot! 05/16/2007
Authors
R.Y.G. Andoh1, R.M. Alkhaddar , M.G. Faram and P. Carroll
Abstract
Several configurations of proprietary ‘flow-through’ stormwater treatment devices have evolved to address the need for compact and effective systems that remove sediment and other pollutants from stormwater runoff. Whilst a number of these systems have been the subject of several field monitoring and independent laboratory studies, differences between design methodologies, unit sizes and capacity, test protocols and site conditions in the field have made direct comparisons of results very difficult. Most studies to date have focused mainly on the pollutant removal efficiency (effectiveness) of these systems.

Though removal efficiency is a good indicator of a devices’ effectiveness in terms of separating pollutants from stormwater, particularly under low flow conditions, it does not provide a complete description of device efficacy especially in terms of its ability to retain previously captured pollutants under moderate or high flows. The phenomenon of ‘Washout’ defined as the tendency to re-suspend (re-entrain) and discharge previously captured pollutants is of particular importance in practice as stormwater treatment devices are typically maintained on an infrequent basis.

The paper describes results of work undertaken at Liverpool (JM) University to determine sediment retention performance of different stormwater treatment chamber configurations under controlled laboratory conditions that provides a true comparative assessment using identical testing protocols and methodologies. General conclusions drawn from the results include the observation that the phenomenon of “pollutants washout” from stormwater treatment chambers is very real and must be taken into account in system selection for practical application. The rate of stored pollutants washout was found to be extremely sensitive to chamber design with re-suspension and washout rates ranging from close to zero to close to 100 percent depending on device configuration, nature and type of flow modifying components and whether or not sediments are stored in isolated storage zones.

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