Abstract
A case study was conducted on the application of modeling in site assessment. We determined the potential for migration of 3 heavy metals and several organic compounds from a site 300 yards north of a swimming area. The site has a history of environmental issues and incidents dating back to 1985. In 2010 the Minnesota Pollution Control Agency (MPCA) measure levels from 638 to 6847 mg kg-1 of ethyl benzene, toluene and xylenes (BTEX) compounds in manholes, tanks, and soil on the site. Previously, lead (Pb), cadmium (Cd) and chromium (Cr) concentrations in soil ranged from 210 to 18,000 ug kg-1. Using reactive transport models with MODFLOW, plumes were developed for metals and BTEX compounds based on data from sediment testing, geological features, and site data from MPCA. Our plume models predict that heavy metals would enter of the swimming lake through surface water runoff and a BTEX plume would enter the swimming lake and the Minnesota River through groundwater. Sediment samples from a drainage ditch adjacent to the site contained concentrations of Cd and Cr 10 times higher than a nearby reference site supporting our plume results. Sediment samples also indicated that Cd and Cr concentrations decreased down gradient, further supporting model predictions. BTEX compounds were not detected in sediment or water samples during the study. We find that incorporating three-dimensional groundwater modeling into a site assessment can provide a useful estimate of a plume’s direction and concentration and aid in determining future sampling locations.
Highlights
1.1 Site AssessmentsPhase I and Phase II site assessments normally are an integral part of the buying and selling of commercial properties the United States
Using reactive transport models with MODFLOW, plumes were developed for metals and BTEX compounds based on data from sediment testing, geological features, and site data from Minnesota Pollution Control Agency (MPCA)
We find that incorporating three-dimensional groundwater modeling into a site assessment can provide a useful estimate of a plume’s direction and concentration and aid in determining future sampling locations
Summary
Phase I and Phase II site assessments normally are an integral part of the buying and selling of commercial properties the United States. In following the American Society for Testing and Materials (ASTM) for Phase I site assessment, all recognized environmental conditions should be identified (ASTM, 2005). If a Phase I site assessment indicates a high probability of contamination, a Phase II assessment should be completed (ASTM, 2005). Phase I site assessments do not incorporate groundwater modeling as a standard practice (Federal Register, 2005). Groundwater-modeling software may provide useful insight in estimating contaminant transport and fate and in determining sampling locations for the Phase II. This case study focuses on an industrial site (referred to as the “site”), which is located at 110 West Lind Street in Mankato, MN. The new owner discovered previously undocumented underground tanks
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