Stormwater pollution is a leading cause of water body impairment and has been linked to stream ecosystem degradation, economic loss, and public health issues. Nutrient loads associated with urban stormwater runoff are a particular concern. Nutrients in urban stormwater are a result of wet and dry atmospheric deposition, fertilization, gross solid accumulation and breakdown, and animal waste deposition. Nutrient loads from urbanized land uses can be quite high. Much of the load is due to increases in runoff volume, often by an order of magnitude above pre-development conditions.
Water quality and stream health improvements can be achieved by implementation of stormwater control measures (SCM, a.k.a. BMPs). This project will examine the benefit of three simple design enhancements for SCMs:
- Upflow filters retrofit at wet ponds’ outlets to increase phosphorus sequestration;
- Inclusion of anoxic sumps to improve denitrification within bioretention; and
- Installation of a stormwater harvesting system downstream of a permeable pavement to reduce nutrient loads.
SCM design enhancements shifts the current paradigm of developing new types of SCMs to evaluating how modifications to existing SCMs can improve performance. This is important because of the large number of SCMs (tens of thousands) that are currently in place, and the widespread opportunity for relatively low-cost retrofit. Monitoring will facilitate field-scale assessment of SCM performance. The data from the monitoring sites augmented with data from the literature will be used to develop and test simple simulation models for the evaluation of the performance of SCMs for nutrient removal at the watershed level. The models will include life cycle cost estimates for existing SCMs and retrofit design enhancements to evaluate cost effectiveness.
The overall goal of this project is to compare the nutrient removal performance and life cycle costs of stormwater control measures using existing design criteria and innovative retrofit design enhancements to increase nutrient removal performance at various temporal resolutions. These technologies present the opportunity for improving water quality and restoring critical ecosystems that are impacted by excessive stormwater nutrient loads.