Sourcing groundwater contamination from possible mine drainage in Navarre, Ohio using MODFLOW

Student: Alexis Lanier
Major: Geology
Minor: Ancient Mediterranean Studies
Advisor: Dr. Karen Alley
This study examines an abandoned underground coal mine in Navarre, Ohio to determine if it is the source of nearby groundwater contamination. Sourcing contamination is important to improve efficiency of remediation efforts. Samples were taken from domestic wells surrounding the mine and analyzed geochemically. Two wells were found to have significant contamination, consistent with that typically found in areas affected by mine drainage. MODFLOW, a groundwater modeling software, was used to characterize flow in the area and backward-track contamination at each sample well. Two wells, the same found to have significant contamination, tracked flow back to the mine of interest, while all others tracked flow elsewhere. Geochemical analysis and modeling together provide significant evidence that contamination from the two affected wells originates in the mine and can be considered mine drainage. However, consistent use of terms associated with mine drainage is necessary to protect affected areas.

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Description

Global clean water supply is heavily dependent upon groundwater. Making up about 99% of Earth’s total liquid freshwater, groundwater is not only plentiful, it is also resilient to contamination. Most pollution must infiltrate into the ground to reach aquifers, passing through naturally occurring sediment filters. However, contamination from underground mines can seep directly into groundwater supplies, bypassing the usual mechanisms of infiltration and recharge. As a result, contamination from mines, commonly called acid mine drainage (AMD) or mine drainage, is a major concern in areas where drinking water is obtained from groundwater near mines. My study sought to find a methodology for identifying and sourcing contamination from abandoned underground mines, motivated by the need to protect and sustainably manage groundwater supplies. Continual contamination of water supplies slowly depletes water available for human use, so sourcing contamination is essential for its effective remediation.
I decided to focus my research on contamination in my hometown of Navarre, Ohio. Underground coal mines are common in the area, but are they the cause of groundwater contamination here? I chose a mine to examine, Fox 12, and took well samples from several houses surrounding the mine to be geochemically analyzed. I found that two wells in particular seemed to have higher contamination relative to the rest of the sample wells, and this contamination was consistent with mine drainage. To see if the contamination could be attributed to the mine, I created a groundwater flow model of the area using MODFLOW, a groundwater modeling software. This allowed me to backward-track contamination from each well to its source. Two wells, the same two found to be geochemically more contaminated than the rest, traced flow through the mine of interest. Observed trends in geochemistry and results from modeling agreed, placing the source of contamination for these wells in the study mine.
The specific results of my study conclude that mine drainage is present in Navarre, but not at concerning levels. On a wider scale, these results provide a framework for detecting and sourcing contamination from mine drainage, demonstrating it to be effective for areas with complex hydrogeological conditions. To ensure safe and consistent use of groundwater for human consumption as well as preserve natural freshwater ecosystems, we must protect aquifers from existing contamination, fixing the mistakes of the past to ensure the sustainable and responsible use of groundwater for the future.
Alexis will be online to field comments on May 8:
2-4pm EDT (PST 11am-1pm, Africa/Europe: evening)

Posted in I.S. Symposium, Independent Study on May 1, 2020.