WERF: STRATEGIES FOR MANAGING STORMWATER:INFILTRATION VS. SURFACE WATER DISCHARGE
Abstract:Stormwater managers are increasingly faced with the need to address many potentially-conflicting issues as part of their activities. First, they need to control the potential flooding waters generated after urbanization. This has led to the use of detention facilities and control of peak flow rates to pre-development levels. However, this has not addressed the need to control the energy of these reduced peak flows in the stream, nor has it addressed the need for localized groundwater recharge. Developments in stormwater management policies such as mimicking pre-development hydrology were designed to address this problem. These incorporate both infiltration and surface treatment and discharge into the management plan.
There is, however, a concern that the potential for groundwater contamination is not well-known and likely not well-documented. Pollutant removal in the subsurface has not been addressed regularly by authors who have either advocated infiltration and/or researched the effectiveness of infiltration at reducing surface water discharge volumes and pollutant loadings. The limited research available on stormwater infiltration's potential to contaminate the groundwater shows that the potential definitely exists for some common stormwater pollutants.
This project has a dual focus: (1) to review the circumstances under which infiltration is practiced, and (2) to determine if vadose zone modeling is capable of predicting the pollutant migration of stormwater pollutants in the vadose zone below infiltration devices. This project has returned to the theory of treatment processes to evaluate whether improved predictions of performance can be made. In particular, this section of the final product focuses on the ability of the natural soils found below infiltration basins to remove three representative stormwater pollutants effectively: zinc, sodium and chloride. Vadose zone modeling was used to predict the depth of migration of these pollutants in the subsurface under realistic conditions to determine which factors influenced migration. Rainfall was the common link to pollutant migration.
Concentration affected the zinc migration whereas intrinsic permeability affected the pollutant depth for sodium and chloride.
Other questions that were raised during the literature review included the following:
How effective are current and proposed stormwater management techniques at protecting surface water quality and habitat, as well as protecting groundwater?
Can a better use of the known theory assist in better predictions of BMP performance and reduce the uncertainty that has to be associated with every stormwater pollutant removal calculation?
How do the chemicals secreted by microorganisms affect pollutant mitigation in the surface and subsurface environment? What role does the local microbiological flora and fauna play in the trapping of pollutants and in the release of previously-trapped pollutants?
Document Type: Research Article
Publication date: January 1, 2005
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