Minneapolis Goes All-Natural

By Ben Johnson

Minneapolis Park and Recreation Board (MPRB) Superintendent Jayne Miller closed her eyes and took a deep breath amid a buzz of last-minute preparations on a sweltering, mid-summer afternoon. Then she opened her eyes and broke into a wide, blissful smile while looking over the Webber Park Natural Swimming Pool (Webber NSP) just minutes before it debuted on July 24, 2015.

It took nearly five years of lobbying, troubleshooting, and unwavering commitment to successfully open the first public pool in North America that entirely eschews chemical treatments to clean its water. Instead, the Webber NSP—free for all users during regular hours—relies on a network of filters, robotic vacuums, and an adjacent 16,000-square-foot “regeneration basin” full of aquatic plants to keep the water clean and clear.

The first seeds of the complicated, innovative project were planted shortly after Miller was hired to head up the award-winning, 6,800-acre park system in November 2010. The old Webber Pool closed permanently that summer after more than three decades of use, and a master-planning process for the park was launched in early 2011.

“The community championed eco-friendly design and innovation during the extensive engagement process regarding the park’s master plan,” remembers Miller. “Building a natural swimming pool aligned perfectly with both the neighborhood’s history and its priorities looking forward.”

Return To Freshwater Swimming
“Webber Park was one of the city’s first freshwater swimming holes, and it’s great to get back to that,” says MPRB Commissioner Jon Olson, who represents North Minneapolis, where Webber Park is located. “Pollution shifted us away from natural swimming more than 80 years ago, but now better technology and a greater understanding of ecological processes gave us an opportunity to return to a chemical-free experience.”

Shingle Creek, which runs through Webber Park before feeding into the Mississippi River, was dammed in 1908 to create Camden Lagoon. With limited access to Minneapolis’ famous Chain of Lakes strewn across the southern half of the city, the lagoon became popular among North Minneapolis residents looking to go swimming or ice skating.

Shortly after the dam was built, local philanthropists John and Mary Webber donated money to construct a two-story bathhouse and public pool that used water diverted from the lagoon. The John Deere Webber Memorial Baths opened in 1910 and attracted thousands of swimmers each summer. Upstream pollution forced a change to chlorinated water in 1927, and the pool was relocated next to a new recreation center in 1979, where it stood until closing in 2010. In 2015, more than a century after the first bathhouse opened at Webber Park, the Webber NSP began a new era of freshwater swimming.

Naturally Cleaned
The first private, natural swimming pool was built in Austria in the 1980s, and the first public one opened in Germany in 1998, so the science behind the self-cleaning technology isn’t new.

1)     Gravity carries water from the pool’s overflow gutters to an underground filtration tank that catches small particles of debris. Water drains from the tank into the regeneration basin.

2)     In the regeneration basin, ultraviolet sunrays, zooplankton, and biofilm covering the basin’s gravel bed all help reduce bacteria.

3)     Thousands of aquatic vegetation planted into the gravel bed feed on excess nutrients to help limit algae growth and keep water clear.

4)     A network of drain tile disperses water throughout the basin, and two pumps send clean water back into the pool.

5)     Pool staff cleans the biological filters daily, and during off-hours three small robotic vacuums remove algae from the pool’s liner.

All 500,000 gallons of pool water complete a cycle from the pool to the regeneration basin and back to the pool every 12 hours. Daily care keeps plants healthy and prevents debris from accumulating, and when fresh water is added to offset plant uptake and evaporation, it first passes through a phosphate filter to minimize algae growth.

Challenges: Politics, Mother Nature, And Malfunctioning Robots
Before ground could be broken, staff and lobbyists took to the state capitol to try to change a law mandating that all public swimming pools must be treated with chemicals to keep water clean. The Webber NSP was eventually granted a special exemption from that law, thanks to supportive local lawmakers.

Then more state legislation was required to allow Webber Park to receive regional park funds, which contributed $2.6 million of the pool’s $7.1-million total cost. Both state legislative pieces passed in 2012, ground was broken on the project in 2013, and funding was secured by 2014. But additional challenges remained.

The winter of 2012-13 was unusually cold, which delayed construction. After the ground thawed, intense storms and rainfall in June 2013 wreaked havoc at the construction site. Finally, two months before the pool opened, staff members discovered the robotic vacuums designed to clean the pool liner didn’t work. New vacuums were ordered, but it would take several months to have them custom-built and shipped from Europe. For most of the 2015 season, pool maintenance crews spent 16 hours a day cleaning the liner by hand.

“Effectively communicating the various challenges we encountered and the solutions to those challenges was critical to maintaining community support,” says Miller. “We had a very successful first season, in large part due to our incredibly dedicated staff.”

Education And Ice Skating
The Webber NSP’s hours were limited to Friday, Saturday, and Sunday in its first season to ensure high water quality. The pool still drew more than 9,200 visitors during the 22 days it was open.

“It’s already one of our most popular summer attractions, and we anticipate its impact continuing to grow as we expand environmental and recreational programming, including exciting wintertime activities,” Miller says.

On June 14, 2016, pool hours were expanded to Tuesday through Sunday. The pool closes after Labor Day weekend, but plans are in place to transition it into a year-round amenity. After the pool freezes over, it will be converted into a neighborhood skating rink, and the pool house will become a warming house, complete with a natural-gas fireplace.

The pool’s state-of-the-art engineering, which operates within full view of park users, inevitably sparks scientific curiosity, so environmental-education opportunities figure heavily into the park’s future plans. Hands-on programs, which are centered on caring for and studying the regeneration basin, are in development.

A Replicable Model
Americans are becoming increasingly wary of chemicals’ pervasive presence in daily life, and natural swimming pools could become a more attractive option for agencies overseeing public recreation, as more and more citizens seek to shift to a natural lifestyle.

The Webber NSP is a model for cities to emulate when residents ask public agencies to explore the feasibility of a natural swimming pool. It took a lot of work to make it happen: The project consisted of political capital to obtain a legislative exemption, allowing for a non-chlorinated public pool, fundraising from multiple public agencies to pay for the project, and troubleshooting from staff members to ensure high water quality. This project blazed the trail, and the trail was full of surprises.

Representatives from several North American cities have already visited for tours and information on building a public, natural swimming pool, and the MPRB sincerely hopes its experience can help make the next public, natural swimming pool even better. For more information on the Webber NSP please visit www.minneapolisparks.org/webberpool.

Ben Johnson is a Communications Representative for the Minneapolis Park and Recreation Board. Reach him at BJohnson@minneapolisparks.org.