After a century of renovations and updates, a Minneapolis park’s swimming hole will return to its freshwater origins and become the nation’s first “natural” public swimming pool.
The $4 million pool project, which is part of a new master plan
for the 22-acre Webber Park in north Minneapolis, is currently in
the design stage. Construction is expected to begin next year, with
a 2014 opening. “We really wanted to create a natural place
where people will want to gather,” says Robert Schunicht,
vice president of Landform, the Minneapolis planning and
engineering firm handling the park’s renovation.
The plans for Webber Park’s new pool are drawing local and
national attention. “The community is really excited about
this,” says Jon Olson, who represents the neighborhoods near
the new pool on the Minneapolis Park and Recreation Board. At
28,000 square feet of swimming area, the pool will offer triple the
recreation space of the park’s aging concrete pool and wading
pool — without any of the chlorine. The preliminary design
includes lap lanes, a diving area, water slide, and a
non-swimmers’ area with a maximum depth of 39 inches.
But instead of the traditional pool chemicals, the Webber Park
pool will rely on a European approach that uses a biological,
plant-based filtration system. As designed, the water in a natural
pool flows from the swimming area to a biological filter and from
there it percolates through a regeneration pond filled with
hydroponic plants, gravel, and other aggregates.
Unlike some chlorine-free pools, “there are no plants in
the swimming pool, and there is no soil,” explains James
Robyn, CEO and president of BioNova Natural Pools, a
New-Jersey-based branch of the German firm BioNova Global, which
will be working with Landform on the project.
The filtered water then returns to the swimming pool via
standard pumps and pipes. Depending on the climate where a natural
pool is built, those plants can vary. For this installation, the
designers are talking with Minnesota growers to develop the right
mix of non-invasive, native plants for the filtering, says Brady
Halverson, Landform’s project designer.
In terms of materials, the pool’s floor will be lined with
a commercial PVC membrane, which less flexible and thicker (60 mil
vs. 30 mil) than a residential pool’s vinyl liner.
“It’s also field-seamable,” Robyn said. “It
comes in rolls. We cut it and heat-weld the pieces together. It
doesn’t have to be preconfigured.”
Unlike many traditional swimming pools, there will be no main
drains at the Webber pool and theoretically a lower risk of
entrapment for users. “We will have Virginia Graeme Baker Act
considerations for the [proposed] water slide, because the water
used to operate the slide will need high-performance pumps,”
Robyn said. “But the biological flow is done with smaller pumps.”
In some ways, the Webber Park project sounds more like a lake
than a swimming pool, but that was part of its appeal to the
community. “We don’t have lakes on the north side of
Minneapolis,” said Olson. “People wanted to be able to
go to the beach.”
Fittingly for this project, Webber Park’s very first pool,
built in 1910, was a spring-fed swimming pond, according to a city
parks history. That original pool was converted to chlorinated city
water in the 1920s. The existing pool, scheduled to be demolished
in 2012, was built in 1979.
The hybrid nature of the new Webber Park pool required some
special considerations. The Minneapolis Park and Recreation Board
operates 60 wading pools, two water parks, and 12 beaches on the
city’s lakes, but this project didn’t fall into any of
those categories. As a result, the board last spring had to get
special state legislature approval to build the Webber pool and
regulate it not as a pool, but a public bathing beach. The city
only monitors E. coli levels at its beaches, closing them as
necessary for health reasons.
“From a microbiological standpoint, our water quality
standards are based on the European standards for public natural
swimming pools, which are roughly twice as strict as what are
required at many public bathing beaches,” Robyn said.
Webber’s plant-based filtering system is expected to cost
less to operate than a traditional chemical pool, according to
those involved in the project, although specific figures
weren’t available. (The park board’s budget includes
more than $414,000 in 2012 for aquatic recreation services, which
includes management, staffing, and lessons for swimmers and sailors
at Minneapolis lakes, pools, and water parks.) Due to the expected
cost savings, Olson said the city would no longer charge visitors
to use the Webber Pool when it reopens.