Performance of Low Impact Development Practices on Stormwater Pollutant Load Abatement

Project summary:

This project will focus on the performance of low impact development (LID) practices on watershed pollutant load computations. These computations are required for a Total Maximum Daily Loads study. Researchers will refine and alter the infiltration capacity testing and simulated runoff methodologies that were developed for rain gardens and expand them for other types of LID practices, including infiltration basins and trenches, porous pavements, vegetative swales, and filter strips. Researchers will select several study sites and adapt different types of LID practices to them; they will then assess long-term performance using an infiltration-capacity testing method adjusted to the particular infiltration practice. The maintenance information on the LID practices will be obtained from the operators, and the maintenance frequency will be correlated with the measured infiltration capacity. Researchers will use previously developed methodologies, which were developed under the contract "Assessment and maintenance of stormwater best management practices," for sampling the size and density of suspended solids. These methodologies will assist in infiltration practice operation (pretreatment) and maintenance needs. Researchers are using infiltration capacity tests before and after maintenance activity to investigate the instant recovery rate of infiltration capacity by maintenance and restoration. The ability of the soil and engineered media to remove and retain chemicals will be assessed with ten column tests, running in parallel, and by installing flux meters directly in the BMPs. Researchers will therefore be able to see the effects of the maintenance. When fines are removed, the infiltration rate and the percolation rates will presumably go up. The uptake capacity for chemicals will decrease as the practices age, which will lead to a larger leaching of chemicals, which can be measured and quantified.