The primary focus of this report is two-fold; to provide a literature review on what has been previously learned about highway runoff in relation to karsts aquifers and to characterize a karsts highway site in Kentucky that can be used to evaluate a variety of best management practices. From research findings, the main sources of pollutants in highway runoff came from vehicles, atmospheric fallout, and precipitation. The behavior of pollutants and their interaction with the environment can dictate where they will be found and how to best minimize their effects. Although it would seem that traffic volumes would greatly influence the accumulation of pollutants on roadways, past studies have not proven this. Instead, no clear relationship between traffic and water quality has been reported. Removal processes such as air turbulence (both natural and the result of vehicles) limit the accumulation of solids and other pollutants on road surfaces, thereby obscuring the relationship between the traffic volume and runoff loads. Of the various precipitation characteristics, intensity was found to have the greatest impact on the type and quantity of pollutants found in highway runoff. This was expected due to the greater velocity traveled by runoff during high rain intensity events which does not allow suspended particles a chance to settle out and often results in greater friction along the runoff travel routes. In all experiments previously conducted, highway paving material appears to have minimal impact. Of the best management practices examined, vegetated controls received the highest recommendation because of their wide adaptability, low costs, and minimal maintenance requirements.

Water quality testing results from the location off I-65 South demonstrated very low levels of select pollutants, when compared to national averages. The existing vegetative controls in the highway median and along the drainage paths are considered to be effective at mitigating a large quantity of runoff from reaching the drainage point into sinkhole.

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The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.