State Water Resources Research Institute Program (WRRI)

Details for Project ID 2015CO316G, 2015

Trace Organic Contaminants (TOrCs) in Urban Stormwater and Performance of Urban Bioretention Systems: a Field and Modeling Study

Institute: Colorado
USGS Grant Number:
Start Date: 2015-09-01 End Date: 2018-08-31
Total Federal Funds: $249,960 Total Non-Federal Funds: $253,099

Principal Investigators: Christopher Higgins, Edward Furlong, Terri Hogue, John McCray

Abstract: Urbanization has degraded the quality and quantity of water supplies, motivating the adoption of new water management strategies. In particular, instances of flooding and erosion due to stormwater runoff have worsened as urban landscapes have become less permeable.2 Urban stormwater is a major source of nonpoint pollution to surface waters, and water quality protection has increasingly become a stormwater management priority. However, despite the increasing application of low-impact development (LID) for urban stormwater management, it is still unclear whether LID systems and other best management practices (BMPs) designed to improve drainage are also improving stormwater quality. While performance data are beginning to emerge for traditional stormwater contaminants, much less performance data are available on the removal of potentially hazardous trace organic contaminants (TOrCs). Indeed, even identifying urban sources of TOrCs is difficult, making it particularly challenging to understand their removal by BMPs or model their loadings to receiving water bodies. This proposal seeks to address this lack of data by identifying sources of TOrCs in urban environments, evaluating their removal in bioretention systems, and evaluating existing stormwater models for predicting loadings to receiving water bodies. This proposal addresses three key research questions: 1) How prevalent are TOrCs in urban stormwater and is their occurrence associated with specific land use types?; 2) How well do conventional bioretention systems perform with respect to removal of TOrCs?; and 3) What are the current data and parameterization gaps in advanced stormwater models and can we improve their predictions through inter-model comparisons and new collected data streams? To answer these research questions, the proposed research will build on and augment existing field and modeling studies in both Wisconsin and Colorado to test the following hypotheses: 1. Strong relationships will be evident between specific classes of TOrCs in stormwater and specific land use types (i.e., residential use herbicides in residential areas, etc.), though some TOrCs will not be strongly associated with any particular land use type (i.e., rubber additives). 2. Bioretention systems will effectively remove (>90%) hydrophobic TOrCs and achieve effluent concentration compliance (when appropriate), but will be considerably less effective for polar TOrCs (corrosion inhibitors, urban-use pesticides, etc.). 3. The availability of high resolution BMP and pollutant load sampling, coupled with systematic model evaluation, will help identify key data-model gaps and help improve parameterizations in two of the most advanced stormwater modeling systems currently in use. These hypotheses will be addressed through the completion of the following three tasks: Task 1: Evaluation of land use impacts on occurrence of TOrCs in stormwater. The occurrence of a broad suite of TOrCs will be evaluated as a function of different land use types. Task 2: Bioretention cell performance TOrC removal. The influent and effluent of bioretention systems in both Wisconsin and Colorado will be sampled to evaluate TOrC removal efficiencies. Task 3: Model Evaluation. Data-model gaps and recommendations for improvements in BMP parameterization will be identified for two stormwater models, EPA SUSTAIN and WinSLAMM through evaluations of the Colorado and Wisconsin bioretention sites.