HIGHWAY STORMWATER RUNOFF MANAGEMENT IN KARST AREAS: WATER QUALITY AND LAND STABILITY

Wanfang Zhou, Barry F. Beck, and Thomas Green

In karst-rich regions, it is inevitable to construct highways on karst landscapes. Two major concerns are closely associated with highway construction in karst areas-the risk of sinkhole collapse under or near the roadway and the negative impacts on water quality from highway runoff. More importantly, these two groups of problems are interrelated and they both can be caused by poor management of stormwater runoff, especially in areas where highway runoff is transferred quickly into subsurface conduit networks through open sinkholes and/or sinking streams. Because roadbuilding across karst landscapes faces both environmental and engineering challenges, it is essential to conduct a systematic study of karst geology/hydrology and formulate a comprehensive stormwater runoff management plan before the highway construction. The commonly used "best management practices" can help manage the stormwater runoff effectively in some sites and in some other sites, site-specific management plan is needed to address these issues. A peat filtration system constructed at the I-40/I-640 interchange in eastern Knoxville, Tennessee was intended to remove highway runoff contaminants prior to being transported into the underlying karst aquifer while maintaining the stability of the site. Preliminary field tests indicate that the system can significantly decrease the concentrations of analyzed constituents including PAHs (polyaromatic hydrocarbons), Copper, and Zinc. The removal efficiency depends on the concentration of the contaminants in the runoff.