Natural swimming pools, which eschew chlorine and chemicals for bio-inspired filtration systems, have taken off in Europe but are still uncommon in North America. So when Pat Hanson, founding partner and creative director at the architecture firm Gh3, set out to build Canada’s first natural outdoor public swimming pool, her team first had to convince their client, the city of Edmonton, that the water would be safe. When Borden Park Pool opened last year, locals lined up all summer to experience the water—and the elegant, stone-lined architecture—for themselves. What is going for a dip in a pool scrubbed by zooplankton really like? “It has a different feeling than being in a chlorine pool,” says Hanson. “The water feels a bit smoother.”
The gravel bed
The pool water is circulated over a large bed of locally sourced granite gravel, which serves as a natural cleansing filter as the water percolates through it.
In these ponds, living plants provide a breeding ground for zooplankton, and these helpful microorganisms feed on bacteria, cleansing the water.
The water is tested and pumped back into the pool, a process that takes about 12 hours.
A version of this article appeared in the October 2019 issue of Fast Company magazine.