Of the roughly 4 million visitors that come to Yellowstone National Park annually, many are drawn to the park’s famous geysers, hot springs, and steam vents. Every few minutes, in various corners of the 3,468-square-mile park, these natural wonders project an immense amount of water into the air. Over time, the condensation turns into precipitation, sending the water back down over the park. When the rain falls, it often accumulates upon the park’s roadways—including Yellowstone’s 142-mile Grand Loop—and runs off into rivers and streams instead of replenishing the aquifers from which much of the water originally came. — Nick Mafi, Architectural Digest
Old Faithful now boasts a porous, clean, flexible walkway that’s made mostly of recycled Michelin tires— between 900 and 1,536 of them, all of which came from Yellowstone’s own truck fleet. Best yet, the new walkway can allow up to 3,000 gallons of groundwater to be absorbed per foot, preventing erosion, preserving the natural patterns of groundwater flow, redistributing water back to natural aquifers, all without leaching oil and contaminants into the surrounding environment.
The pavement surface is made from a material called Flexi-Pave, manufactured by K.B. Industries (KBI). “Flexi-Pave is made of rubber granules and stone held together by a polymer binding agent that is inert when cured. Its open-pore design enables fast evacuation of up to 4,000 cubic inches of water per hour…Unlike asphalt or concrete, which wicks water away from the surface, Flexi-Pave’s porous material allows rainwater to shoot straight into the earth, where it can settle in nearby aquifers.”  “Beyond Yellowstone, this innovative product has a broad range of applications. The thousands of rubber granules making up its surface make it non-slip and it is an ADA-compliant surface accessible to wheelchairs and walkers. The integrity of the materials are not affected by freeze-thaw conditions.”
“Flexi-Pave not only provides an environmentally friendly solution for the Old Faithful area, it prevents thousands of old tires from ending up in a landfill or being burned for fuel,” said Kevin Bagnall, CEO and founder of KBI.  According to Bagnall, Flexi-Pave is currently being used in 200-300 cities in the United States. He is looking forward to expanding the product’s use to every city around the globe due to its environmentally beneficial qualities, especially as compared to standard concrete, paving, and asphalt products. As urbanization and population density both increase, Bagnall says conserving clean water will become a much larger concern. “Our most valuable resource is water,” Bagnall says. “If [Flexi-Pave] can be used in better urban planning, that valuable water is going to go back into the earth where it would naturally go, and therefore we’d be keeping the levels of our aquifer for potable water supplies.” 
Flexi-Pave does face some competition in the “thirsty concrete” market. The British company Tarmac uses fine pieces of granite in place of recycled rubber to create its Topmix Permeable, which can absorb 880 gallons of water per minute, according to company estimates. But KBI, according to Bagnall, thinks rubber is superior to Tarmac’s granite because it has flexibility and isn’t prone to cracking or settling. The recycling of tire rubber is an added bonus, as exemplified by the partnership with Michelin and Yellowstone National Park. 
The Yellowstone Walkway Project around Old Faithful is being held up as a model of what Public-Private Partnerships (PPPs) can do for the country. The project was made possible through a partnership between Yellowstone National Park, park concessioners, the Yellowstone Park Foundation, KBI Industries and the Michelin Corporate Foundation. “Michelin serves as a major corporate sponsor of the Yellowstone Park Foundation, with a goal of helping the park curb operating expenses and reduce the consumption of raw materials. To that end, Michelin regularly donates and helps maintain thousands of tires for Yellowstone National Park’s more than 800 vehicles, including patrol cars, garbage trucks, snow plows and load-hauling tractor trailers. The tires feature the latest in green tire technology to help save fuel and reduce emissions.”  “This project represents the model for collaboration between public and private organizations. We hope that this eco-friendly park walkway will inspire other similar projects that help preserve natural systems,” said Jeff Augustin, vice president of external partnerships at Yellowstone Park Foundation. 
“Yellowstone is the world’s first national park with nearly 150 years of balancing the protection of natural wonders and sharing them with visitors,” said Lynn Chan, a landscape architect for the National Park Service and lead on sustainability at Yellowstone National Park. “It is important to us to rehabilitate the park’s walkways with materials that can help protect this sensitive environment yet still allow visitors to see and appreciate it.” 
1.) “Flexi-Pave is 23% porous, thanks to a careful combination of tires, stone, and a proprietary binder invented by KBI. That allows it to absorb rainwater quickly, which keeps storm runoff from mixing with local contaminants before entering the water supply. That helps decrease water pollution, which is especially important at Yellowstone.” (KBI; Business Insider)
4.) Business Insider
6.) “We are fortunate to have a corporate partner as farsighted, public-spirited and generous as Michelin,” Karen Bates Kress, president of the Yellowstone Park Foundation. “Michelin flew in a team of employees from across the country to help complete the construction of the walkway. The 10 volunteers were winners of a company-wide contest to participate in the project. “The Old Faithful Walkway Project is a great example of what a difference a company devoted to sustainability can make in the world’s first national park,” said Kress, president of the Yellowstone Park Foundation. Yellowstone Insider
7.) Yellowstone Insider
A.) Michelin North America is MNA on the NYSE and includes the brand names Michelin, BF Goodrich, and Uniroyal. According to the company, the tires on the lunar rover come from Michelin.
C.) Yellowstone National Park crosses three states. Its website is here.
D.) Information on the Tarmac Company (UK) can be found here.
E.) A couple things on public-private partnerships (PPPs): via World Bank,via Progressive Policy Institute, via Stanford University, The National Council on Public-Private Partnerships (NCPPP), and here is Economic Policy Institute (EPI) with a con, at least regarding infrastructure. Oh, and Wikipedia, because you know you want to.
F. ) See also: USANews
G.) Nick Mafi, Architectural Digest.