Wet Pond Modeling for Contaminant Retention and Maintenance

Project summary:

Many of the more than 30,000 ponds in Minnesota are connected to stormwater pipes and act as a part of the stormwater treatment system by storing runoff and settling solids along with associated pollutants to the bottom of the pond. Older, non-maintained ponds may no longer be providing the water quality benefits of the original design. Researchers have found that many ponds are stratified at one foot of depth and have high organic matter levels, often creating a bottom region of low dissolved oxygen water. The low dissolved oxygen concentration will cause these ponds to rerelease phosphorus trapped in the bottom sediments back into the water column (i.e., internal phosphorus loading). It is critical to maintain both stormwater ponds (infrastructure created to treat pollution) and natural water bodies that receive stormwater which can be managed to reduce pollution to downstream priority waters (a flooded wetland of varying type or type 5 wetland), and develop methods to improve their functionality, but specifications are minimal.

Through modeling efforts and field measurements, this research will further investigate maintenance approaches to mitigate phosphorus pollution from ponds. Thus, this project will 1) model pond maintenance methods that can reduce internal phosphorus loading on at least four additional ponds beyond those in Taguchi, et al. (2022) and with additional maintenance procedures increasing the diversity of conditions represented and 2) collect field measurements and perform data analysis to verify the model, including on recent novel pond treatments, toward improvement of pond phosphorus retention performance. Results from this project can be used to maintain and apply design retrofits to existing and new ponds to improve pond performance and benefits for use along roadways throughout Minnesota and the United States.