Water, Air, & Soil Pollution

, Volume 218, Issue 1–4, pp 529–538 | Cite as

An Evaluation of the Toxicity of Accumulated Sediments in Forebays of Stormwater Wetlands and Wetponds



Forebays, small settling basins placed at the inlet of Stormwater Best Management Practices, encourage sedimentation with the intention of pollutant consolidation and capture. Regularly, accumulated sediments are excavated to restore forebay storage volume and to further prevent contamination of downstream waterbodies during large storm events. Disposal measures vary according to the toxicity of sediments. To test for the potential toxicity of forebay spoils, 30 stormwater wetland and wetpond forebays of varying age, size, and upstream landuse were sampled across North Carolina and analyzed for seven metals: cadmium, chromium, copper, iron, lead, nickel, and zinc. Ten of 30 sites were also sampled near the outlet structures for spatial comparison of settled sediment and pollutant presence. The relative toxicity of all sampled sediment metal concentrations was evaluated using existing aquatic health sediment guidelines and US Environmental Protection Agency standards for the land application of biosolids (40 CFR503). Of 30 sites, 17 exceeded sediment guidelines for aquatic health, emphasizing the need for routine forebay sediment removal. However, all samples were less than 40 CFR 503 limits with factors of safety ranging from 2.3 to 28, indicating that land application of forebay sediment is unlikely to pose an environmental threat. Additionally, forebay sediment tended to have lower metal toxicity than sediment collected at the pond or wetland outlet.


Sediment Forebays Stormwater wetlands Stormwater wetponds Water quality Land application 



Several NCSU students and faculty assisted with data collection of this project: Cole Ammons, Robert Brown, Amelia Clark, W. Evan Corbin, Shawn Kennedy, Trisha Moore, Bill Price, and Erica Tillinghast. Public works officials in the following municipalities are very much appreciated: Apex Charlotte, Durham, and High Point. Each assisted with pond and wetland identification and location. Officials in Durham expended a substantial amount of effort in helping the research team and are especially thanked.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Department of Biological and Agricultural EngineeringNorth Carolina State UniversityRaleighUSA
  2. 2.Department of Biological and Agricultural EngineeringNorth Carolina State UniversityRaleighUSA

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