The video of a Tennessee mountainside crashing down onto U.S. 64 in Polk County on Nov. 10 was indeed spectacular and made national news. A rockslide that closed I-40 in North Carolina has also garnered its share of headlines and impacted thousands of motorists. With clean-up at both sites expected to take months, these events show the impact rockslides in mountainous areas can have on our transportation system, local economies and the commuters who rely on these routes.

Given Tennessee's terrain and the vagaries of weather and other factors, the threat of such rockslides is ever present.

Several years ago, TDOT began implementing a Rockfall Mitigation Program to address these transportation pitfalls. The program first identifies potential rockfall sites, and then assigns a hazard rating to each location. The hazard rating is based on the potential for a rockfall event and the impacts to travelers and surrounding communities.

By 2005, we developed a list of nearly 2,000 locations vulnerable to rockslides. From that initial list, 36 sites were identified as high priority. In 2008, TDOT launched the first three projects to address high priority areas. One early project was located along I-40 in Cocke County, just four miles west of the rockslide that closed the interstate in North Carolina in late October. A second dealt with an area on I-75 in Campbell County where a slide had already occurred, and another involved the busy I-440 corridor in Nashville, where loose, overhanging and unstable rock was removed from a slope near Hillsboro Road. Today, two additional projects are underway on another section of I-40 in Cocke County and a stretch of I-40 in Putnam County.

Topographical characteristics make some areas harder to address than others. TDOT has identified eleven sites along U.S. 64 in Polk County that have a high potential for rockfall events, including the site where the rockslide occurred on Nov. 10th, but addressing these sites is both costly and would negatively impact motorists and communities. U.S. 64 is a narrow corridor. In order to safely address all ten remaining high priority sites the road would have to be closed for as much as a year and the cost would be more than $40 million, not to mention the negative consequences to local economies. That's why it's important to continue development of an alternative route through this area.

Watching the video of the slide in Polk County it's hard not to imagine the "what if's." While the risk of injury or death for motorists is low for any rockslide incident, as we've seen in recent weeks the economic and traffic impacts are very high. We have no guarantees against these natural forces, but TDOT isn't waiting for rockslides to make headlines. Our approach will remain aggressive. We will continue to closely monitor these areas, initiate preventative maintenance and projects, and dedicate the funds necessary to keep Tennesseans safe and in motion.