Wet Pond Maintenance for Phosphorus Retention

Status:  Complete
Report Date:  07/26/2022


Rainwater washing over streets and other areas picks up pollutants that are harmful to water quality. Thousands of stormwater retentions ponds, including some in parks and other community settings, are designed to trap these pollutants in sediment to prevent them from overflowing into lakes and streams. New research gives cities and counties cost-effective methods to ensure the ponds continue to operate as intended. After high concentrations and releases of phosphorus—the culprit of toxic algae blooms—were found in some older or failing ponds, the Local Road Research Board worked with researchers to mitigate sediment phosphorus release. Dredging and disposing of contaminated sediment, which is the traditional response, can be too costly and logistically challenging. Using modeling, field measurements and data analysis, researchers discovered that treating the sediment with alum or iron filings, installing air diffusers for mechanical aeration, or sometimes using both practices are successful, cost-effective methods for preventing the release of excess phosphorus into Minnesota’s waterways.

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