Inside the new visitor center at the Mammoth Cave National Park in central Kentucky, a chimney envelops the information desk. A skylight at the top of the chimney directs natural light onto the desk area. © National Park Service/Steve Kovar
The National Park Service replaces a nondescript visitor center with an impressive structure inspired by classic Works Progress Administration designs.
March 19, 2013—Each year more than 1 million people travel to central Kentucky to visit Mammoth Cave National Park, a 52,830-acre tract featuring the longest known cave system in the world. The system’s mapped area comprises 400 mi of tunnels, and new passages continue to be discovered.
The National Park Service (NPS) recently unveiled an impressive new visitor center to greet park guests. The structure replaces an outdated, nondescript two-story masonry and steel structure that more closely resembled an elementary school and dated to 1964.
“The Park Service was very interested in a traditional parklike building,” says Tom Brooks-Pilling, a vice president of Parsons Brinckerhoff, of New York City, which designed the project. “When you think of Yellowstone and you think about the visitor center there, that’s what they wanted—a big, uplifting space.”
Using the robust stone and wood structures built during the years of the Works Progress Administration as inspiration, Brooks-Pilling sketched the basic shape of the new center on a napkin one evening. The NPS approved the concept.
The design quickly moved from a napkin to a building information modeling (BIM) program in Revit—produced by Autodesk, Inc., of San Rafael, California—which made it easier to manage the complex project. Because the existing visitor center was ideally situated amidst the park’s infrastructure and trails, the NPS wanted the new center at the same location. The design team developed a plan that incorporated a portion of the existing building, essentially encapsulating it within the new center.
More than 1 million people a year visit Mammoth Cave National
Park, and many will pass through this new, state-of-the art visitor
center, which incorporates the structural framing of the previous
center within it. © National Park Service/Steve Kovar
“I think [BIM] helped us through quite a few of the challenges,” Brooks-Pilling says. “We built the existing visitor center within a building information model, and we dismantled it, and we rebuilt the new building around it. And that really helped us coordinate the design between the existing construction and the new construction.”
The center was designed as a two-phase project to accommodate the NPS budget. In the first phase, a portion of the existing structure—an outdated and unused 5,600 sq ft administration wing—was demolished. A new structure was built comprising an entry hall, an impressive 360-degree information desk, an orientation area, public restroom facilities, a technology room, and a mechanical plant.
The second phase, which was expedited with funds from the American Recovery and Reinvestment Act of 2009, encompassed the extensive renovation of the existing structure’s visitor center. The structure was stripped to its steel framework, which was then integrated into the new visitor center. That portion of the new center includes an exhibit hall complete with a replica of one of the caves.
“Using a phased approach, in which we had to leave the [old] visitors’ center operational while we built the new visitor center, worked out really well,” Brooks-Pilling says. “They were able to continue operations while we were constructing the first phase. Then, once that was opened, they moved operations into the first phase. And we were then able to start dismantling and renovating for phase two.”
There were two reasons that the team decided to reuse the existing structure, he says. “One is [that] it is a good steel frame. Rather than remove it and replace it, why not recycle it? We were able to do that, with a certain degree of savings,” Brooks-Pilling says. “Two, the park liked the relationship of the visitor center to the trail that brought [visitors] down to the cave entrance. The infrastructure for vehicles was already in place. Across the ravine from the visitor center is the Mammoth Cave Hotel, where people who aren’t camping [stay]. There is a bridge across the gorge from the hotel to the existing visitor center.”
In fact, the visitor center site is surrounded by a vast parking lot for the more than 5,000 guests who arrive each day during the peak summer months. To make the new center more identifiable to visitors at a distance, the design team developed an innovative solution.
This elaborate re-creation of a portion of Mammoth Cave is part of
the new visitor center, offering an educational glimpse of the cave
below and how it was formed. © National Park Service/Steve Kovar
“One of the fun components that we came up with was a chimney element that does many different things,” Brooks-Pilling says. “It pokes up through the gabled roof of the building and projects really high. So, as you turn into the campus, you will certainly start to see this chimney element.”
Inside the building, the chimney is integrated into the information desk, creating a dramatic focal point. A skylight complete with mirrors at the top of the chimney brings natural light into the desk area. The mirror assembly, and the photovoltaic array that powers it, track the sun to maximize the use of natural light.
“The chimney also has operable vents on the sides at the top,” Brooks-Pilling explains. “During spring days and fall days, when the humidity isn’t so high, we can open the building’s windows and then [these vents] create a stack effect to circulate air.”
The design team specified locally sourced sandstone for the facade, and the massive timber beams were easily sourced through the robust timber industry in the vicinity. Visitors who look very closely at the “slate” roof will probably never realize that the tiles are actually made of rubber recycled from automobile tires. The tiles have an expected life span of 50 years.
Easier to discern on the roof is the vast photovoltaic array. Its capacity, 30 kVA, is such that excess electricity can be fed back to the power grid. The roof is also designed to channel rainwater into a 30,000 gal system of underground cisterns for reuse in the center’s toilets.
The cisterns presented a construction challenge. The center is sited on top of a cave, which means abundant rock formations close to the surface. Some mild site grading was needed to fully bury the fiberglass tanks.
The roof—which appears to be slate—is actually recycled
automobile tires. The solar photovoltaic array provides 30kVA of
the building’s electrical demand and can feed excess energy
back into the power grid. © National Park Service/Steve Kovar
During demolition, the team made an interesting discovery in the rock. It seems that during construction of the previous building, workers carved tunnels into the rock large enough for workers to crawl through for some of the building’s mechanical systems. The new building utilizes those tunnels as runs for power and communications cables.
Another interesting feature under the old building—one that was not available for reuse—was a small tunnel carved through the rock into the cave that for a time was used to draw the cool underground air—a nearly constant 54°F—into the structure during the summer. That tunnel was closed off earlier to avoid introducing contaminants into the sensitive cave environment, home of the eyeless cave shrimp, and to prevent radon from the cave from entering the building.
The design portion of the project began in 2006. Construction work on the first phase began in 2009, and the center was completed late in 2012. According to Sarah Craighead, the superintendent of Mammoth Cave National Park, the completion of this new visitor exemplifies a team effort. “The park service team, our consultants, and our contractors all worked hard to make this outstanding facility a reality. It will certainly help us meet the needs of our park visitors for the next 50 years,” she said in written comments to Civil Engineering online. “But more importantly, it will give us the opportunity to educate our visitors about the features that have been incorporated into this new building that make it sustainable and energy efficient.” In fact, it is hoped that the vast array of sustainability measures that have been incorporated into the building will qualify the structure for gold certification in the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program.