Do Limestone Quarries Act as “Engineered Sinkholes”? Analysis of Exfiltration of Groundwater from Limestone Quarries in the Boone Formation, Ozark Physiographic Province, Arkansas, USA

Limestone quarries are a source of construction materials that are utilized in our everyday lives. Karst landscapes cover up to 15 percent of the Earth’s surface, and limestone quarries are found in these environmentally sensitive regions where groundwater and surface-water interactions are dynamic and complex. Several studies have provided conceptual models of groundwater flow to and out of quarries. The goal of this research was to describe the geochemistry of water exfiltration from limestone quarries in karst regions via joints, fractures, faulting, or karst features and to determine if limestone quarries are “engineered sinkholes”; that is to say: did quarries, by nature of removal of overlying regolith and subsequent excavation into bedrock, act to increase infiltration into karst groundwater systems, potentially effecting some influence on groundwater chemistry? Water chemistry, water stable isotopes and dye trace data were used as means for characterizing groundwater flow out of and near limestone quarries. Connections between quarries and nearby springs were established based on evaporation indicated by water isotopes and similar trends in nitrate, calcium, chloride, and other water chemistry characteristics data. The dye trace conducted did not prove a connection between a dry quarry and nearby springs during the study period, further highlighting the complexities of groundwater flow in karst landscapes. Nitrate, pH, calcium, and alkalinity water chemistry characteristics between springs near quarries and springs near sinkholes were statistically different indicating that the differences in soil cover may have a great impact on water chemistry and nutrient transport. Because of the differences between sinkholes and quarries, applications of geologic time were considered for the formation of soil and karst features at active, dry, and lake quarry sites. Groundwater is flowing out of limestone quarries in karst landscapes via joints, fractures, and conduits even though signatures of quarry water was not found in all of the monitored springs. The data from this study suggests that a deeper, regional groundwater flow path into large springs and spring-fed streams is the likely output of water from limestone quarries in karst landscapes