J. Bradley Mikula, Penn State Harrisburg, 777 West Harrisburg Pike, TL 105, Middletown, PA, 17057, Tel: 717-948-6358, Fax: 717-948-6580, Email: jum170@psu.edu
Shirley E. Clark, Penn State Harrisburg, 777 West Harrisburg Pike, TL 173, Middletown, PA, 17057, Tel: 717-948-6127, Fax: 717-948-6580, Email: sec16@psu.edu
Katherine H. Baker, Penn State Harrisburg, 777 West Harrisburg Pike, TL 105, Middletown, PA, 17057, Tel: 717-948-6308, Fax: 717-948-6580, Email: khb4@psu.edu

Urbanization has been responsible for an increase in the amount of impervious surfaces, leading to an increase in stormwater runoff and a decrease in groundwater recharge. Stormwater runoff contains pollutants, such as nutrients, pathogens, heavy metals, solids, organic compounds, pesticides, and chlorides, which have greatly contributed to the degradation of receiving waters due to surface discharge of stormwater. A high demand for groundwater combined with a decrease in stormwater infiltration locations also has led to a decline in water tables. This has prompted stormwater managers to consider implementing more infiltration practices into their designs. However, past studies have shown that infiltrating stormwater could contaminate the groundwater, and in some cases contamination actually has occurred. Therefore, methods for easily predicting contamination potential need to be developed.

Stormwater pollutants interact with the soils in the unsaturated zone as they migrate towards the groundwater. The specific type of soil and its properties have a profound effect on the movement of water and pollutants. Through the use of the SESOIL model, this research will evaluate which soils are best for preventing stormwater pollutants from reaching the groundwater, while still allowing groundwater recharge. Factors such as pollutant concentration, rainfall, depth to groundwater, hydraulic conductivity, organic content, and soil pH will be evaluated to determine which ones have the greatest influence on pollutant migration. They will be evaluated using a factorial design analysis. Zinc and sodium chloride were chosen to be the pollutants of interest because of their prevalence in stormwater, solubility, and differing migration rates. Initial concentrations used in the model ranged between 32 and 2100 μg/L of zinc and 69 and 3400 mg/L of sodium chloride. In addition, long-term simulations using actual rainfall data will be performed to evaluate the effects of frequent storms and drought conditions on predicted pollutant movement.    

Testing New Capabilities for Simulating Free and Dissolved Phase Transport using MT3DMS

Matthew Tonkin, S.S. Papadopulos & Associates, Inc, 120 Main Street, Rt. 6A, Yarmouth Port, MA, 02675, Tel: 508-362-7014, Email: matt@sspa.com
Chunmiao Zheng, Professor of Hydrogeology and SSPA Faculty Fellow, Department of Geological Sciences, University of Alabama, Tuscaloosa, AL, 35487, Tel: 205-348-0579, Email: czheng@ua.edu
Jim Weaver, US EPA, Office of Research and Development, Athens, GA, Tel: (706) 355-8329; Email: weaver.jim@epa.gov
Chris Muffels, S.S. Papadopulos & Associates, Inc, 7944 Wisconsin Avenue, Bethesda, MD, 20814, Tel: 301-718-8900, Email: cmuffels@sspa.com

The vadose zone free-phase simulation capabilities of the US EPA Hydrocarbon Spill Screening Model (HSSM) were recently linked with the multi-species dissolved-phase contaminant transport simulator MT3DMS.  The HSSM simulates a spill release, its one-dimensional migration to the water table, and the development and dissolution of a floating lens of product upon the water table. The linkage enables the analytical treatment of vadose zone transport from multiple spill-type sources to be included in a numerical simulation of dissolved-phase aquifer contamination. The codes were linked by compiling relevant modules of the HSSM as a Dynamic Link Library (DLL), and developing a time-varying source package for MT3DMS referred to as the Hydrocarbon Spill Source Interface Package (HSS Package). We outline the approach adopted for linking the simulation codes, and present a real-world groundwater flow-and-transport simulation in which MT3DMS executes the HSS Package.  This simulation illustrates some benefits of the linked simulation approach, in particular the simultaneous calibration of parameters from both models to field data using programs developed to support the use of the HSS Package with PEST.

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Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

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