A GIS Approach to Assess Groundwater Contamination Risk in a Limestone Quarry under Post-Mining Land Use Scenarios

Drinking Water
Poster Presentation

Prepared by K. Tran
Austin Community College, 2605 Quiet Moon Trail, Cedar Park, TX, 78613, United States


Contact Information: [email protected]; 512-955-0190

ABSTRACT

Approximately 25% of the world's population relies on karst aquifers for drinking water. However, karst geology remains highly vulnerable to contamination due to its rapid transport of runoff. Quarrying for limestone greatly worsens this vulnerability. Despite growing trends in quarry redevelopment, research on the impacts of urbanization on quarried karst remains limited. The Lime Creek Quarry in Cedar Park, Texas, situated on the Edwards Aquifer Recharge Zone, exemplifies this challenge. Although mining ended in 2023, 173 years of excavation removed protective karst layers below the water table, exposing the recharge zone. The city's proposed urbanization of the 216-acre site raises concerns about channeling contaminated runoff into the Edwards Aquifer, which 2.5 million Texans rely on for drinking water. This study assessed how groundwater contamination risk will spatially vary under different post-mining scenarios considered by the city. The GIS workflow established baseline vulnerability by analyzing geologic, soil, infiltration, and karst conditions, followed by pollutant load mapping from referencing conceptual plans and assigning multiplicative scores. Final risk maps were generated by overlaying vulnerability and hazard layers for each scenario. Results showed that enhanced stormwater controls reduced high-risk area by 39% compared to minimal reclamation, and park development reduced it by 58% total. Risk models were validated through sensitivity analysis and groundwater sampling, with measured nitrate concentrations correlating with predicted vulnerability (r=0.82). This study not only informs local decision-making but also provides a transferable approach for communities worldwide experiencing quarry reclamation. Overall, it was demonstrated how contamination of karst aquifers is highly sensitive to land use changes.