Mammoth Cave National Park is home to the longest-known cave system in the world. Most people don't think about air quality issues in national parks, but Mammoth Cave lies in the East and there are a lot of what's called mobile sources, which are cars and trucks and diesel engines.
There's just a lot of traffic...all around us. In the early 2000s...we started thinking about changing our vehicle fleet to alternative fuels. It was mostly because of air quality. We've made this change to alternative fuels gradually. We've had a lot of help from a group called the Kentucky Clean Fuels Coalition. And also, the Clean Cities initiative through the Department of Energy.
We have tour buses that we use to bring people from the visitor's center out to outlying caves entrances. We run about 7 buses every day and they're going all day long, back and forth, on short trips. We were able to change those over from diesel fuel to propane and they perform just beautifully.
We've also got a couple propane pick-up trucks that our rangers use when they go out to check outlying cave entrances, do visitor assists. We have several electric vehicles in the park. Some that are almost like small trucks that can carry things.
Our rangers staff, like in our campgrounds, uses the small GEM vehicles for patrolling. We also use biodiesel in the park, and we have found that it works very well in our equipment and even our ferry boat, which runs short trips back and forth across the Green River. To be good stewards of the land, we thought that this was one option to put forward. As a National Park, we're mandated to take care of everything that's here. So that's the cave, the rivers, the forest, the animals that live here and air quality plays a role in all of that.