Water Resources Research Act Program

Details for Project ID 2015DC168B

Evaluating Long-term water quantity and quality performance of Bioretention systems in Washington, DC using monitoring and modeling

Institute: District of Columbia
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $10,000 Total Non-Federal Funds: $23,870

Principal Investigators: Arash Massoudieh, Arash Massoudieh

Project Summary: The main role of low impact development (LID) practices in the context of sustainable urban stormwater management is to reduce the volume and the peak flow rate of stormwater hydrographs and also to retain the contaminants through processes such as particle deposition, filtration and adsorption to the underlying soils. Achieving these goals has multiple environmental benefits to the receiving waters such as the reduction in the high contaminant concentration discharge during the first-flush period, erosion reduction, and most importantly decreasing the frequency of emergency bypass operations of non-treated stormwater in locals with combined sewer systems and limited waste water treatment plant capacity. Other benefits of such system is reducing flood risk and reducing the cost of stormwater conveyance system. These environmental benefits become more pronounced in highly urbanized areas like Washington, DC where the majority of the city is a combined sewer network and thus the storm runoff exceed the capacity of the wastewater treatment plant during large rain events. The District of Columbia bypasses large amounts of non-treated stormwater into the surrounding waterways including the Anacostia and Potomac Rivers and the Rock Creek stream. For these reasons implementation of LID practices such as bio-retention systems has been promoted by the city. Tools that predict the performance of various designs of bio-retention systems are essential in evaluating their effects on improving the overall stormwater quality and also for finding the design parameters of these LIDs resulting in their optimal effectiveness. The modules representing the behavior of LIDs in commonly-used stormwater modeling programs such as SWMM (Rossman, 2004) are still extremely simplified and cannot capture many of the processes affecting the water retention behavior of the LIDs. Our goal is to evaluate the long-term performance of bioretention systems using a combined monitoring and modeling effort. For this purpose a detailed physically-based model considering various processes affecting water retention and contaminant transport in bioretention systems will be developed and calibrated to the monitoring data. Then the calibrated model will be used to evaluate the long-term performance of bio-retention system and also to evaluate the effect of different designs on the long-term performance of such system. Our plan is to conduct extensive monitoring on the bio-retention structures recently constructed in the District of Columbia. The modeling tool developed will allow us to interpret and generalize the data obtained during the monitoring. The outcome of this study will be used as complimentary data for a larger contract with the U.S. EPA. The specifics objectives are summarized, as follows: • Obtain long-term monitoring data of water quality/quantity and precipitation from a bio- retention system. • Develop and calibrate a detailed stand-alone bioretention model. • Evaluate the effectiveness of the specific bio-retention system as installed. • Better understand the internal biogeochemical processes affecting contaminant transport and retention in bio-retention system. • Inform the realistic representation of a bio-retention system in a larger modelling context.