Wet Pond Maintenance for Phosphorus Retention

Abstract

This report considers the outcomes of the pond maintenance strategies of sediment treatment to reduce internal loading of phosphorus, mechanical aeration, alteration of pond outlet to pull water off the bottom, reduction of wind sheltering, dredging, outlet treatment by iron enhanced sand filtration and reduction of phosphorus loading from the watershed. The strategies were analyzed with the model CE-QUAL-2E, where inputs to the model were initial conditions, morphology, inflow rate and total phosphorus and soluble reactive phosphorus concentrations, sediment oxygen demand, sediment release of phosphate, and meteorological conditions. The model as applied in this research simulates stratification, wind mixing, outflow and vertical profiles of temperature, dissolved oxygen, chloride, soluble reactive phosphorus, and total phosphorus. The model is calibrated on data from Alameda pond, verified on data from the Shoreview Commons pond, and applied to maintenance and remediation strategies for the Alameda, Shoreview Commons, Langton, and Minnetonka 849W ponds. Costs of maintenance or remediation strategies are estimated and the cost per reduction in total phosphorus release is calculated.