Performance of Low Impact Development Practices on Stormwater Pollutant Load Abatement

Abstract

Stormwater runoff is a major contributor to the impairment of surface waters in the United States. With high connected impervious surfaces and concentrated human activities, urban land uses are involved in discharging most of the stormwater volume and pollutant loadings during a storm. Stormwater pollution prevention involves the installation and maintenance of stormwater low impact development (LID) practices in urban areas. These include infiltration basins and trenches, porous pavements, rain gardens, vegetative swales, and filter strips. LID practices infiltrate and detain stormwater to reduce stormwater runoff volume and improve water quality via filtration and other processes. The reasons for assessing the performance of the LID practices include fulfilling stormwater permit regulatory requirements, engineering and design due diligence, scheduling maintenance and TMDL studies. The results of the assessment allow for an improved understanding of the role of the various system components (i.e. soil, plants, etc.) in pollutant removal and volume reduction.

This project is designed to assist MS4s in the assessment of their stormwater BMPs and the utilization of these BMPs in watershed TMDL analyses. Objective B of this project focuses on the infiltration performance of low impact development (LID) practices. The infiltration capacity testing developed for rain gardens (Asleson, et al. 2009) was to be refined, altered and expanded for other types of LID practices including infiltration basins and trenches, vegetative swales and filter strips. The Modified Philip Dunne (MPD) infiltrometer is implemented as a low-effort, low-cost method to determine saturated hydraulic conductivity, a predictor of infiltration capacity. This infiltration tests have been performed on rain gardens, infiltration basin, swales and turf areas.