Highway stormwater runoff in karst areas — preliminary results of baseline monitoring and design of a treatment system for a sinkhole in Knoxville, Tennessee

Groundwater is vulnerable to contamination in karst areas where highway stormwater runoff may flow directly into karst aquifers with little or no natural attenuation and transport highway-derived contaminants rapidly from sinkholes to locations in the aquifer. The primary goal of this investigation is the development and evaluation of practical remedial measures for treating highway runoff draining into sinkholes. Field testing sites are located in Knoxville, TN, and Frederick, MD. This paper presents a summary of preliminary results of baseline monitoring in Knoxville. Quantitative dye tracing and hydrograph analyses have demonstrated that water draining into the I-40/I-640 sinkhole passes through a phreatic conduit and resurges at Holston Spring ca 128 m (420 ft) from the sinkhole. Stormwater quantity has been monitored continuously for more than 1.5 years, and runoff quality has been monitored during a storm event. For most of the contaminants analyzed, peak contaminant loading at Holston Spring lagged behind the peak at the sinkhole by approximately 1 hour. The movement of stormwater from other sinkholes in the drainage basin to Holston Spring is regulated by partial blockage of the conduit-dominated flow system. Urban development of the karst terrane in eastern Knoxville may be responsible for this observed phenomenon. A pilot-scale stormwater runoff treatment system has been designed using peat, sand, and rock to remove contaminants by sedimentation, filtration, and adsorption.