Tennessee Department of Tourism Commissioner Kevin Triplett was in Warren County yesterday in the depths of Cumberland Caverns.He watched as workers maneuvered around the Volcano Room on ledges and on ladders making final preparations for the three-day PBS taping of Bluegrass Underground, which begins tonight.The TV show has drawn more than the attention of the state’s tourism commissioner. It’s helped to bring people to Warren County by the carload, appearing in 183 PBS markets in 49 states during its five-year run. Filming this weekend is for Season 6.