An Upstart New York Architect Dreams Up a Swimming Pool in the East River

Conceptually, the notion is so simple that it seems almost elementary: The + POOL will be "like a giant strainer," Wong explains, with walls built out of several layers of varying permeability: a loose, net-like material to catch larger chunks of garbage and debris, all the way down to one with holes fine enough to let water in while keeping bacteria out.

The floating structure is shaped like a giant plus sign, with each axis forming a separate, Olympic-size pool. The water comes straight from the source (either the Hudson or the East River, depending on the site the team chooses); with the help of the numerous pumps and fans affixed to its sides, the pool will pull water through layer after layer of geotextiles, porous fabrics that filter and transform it from the toxic brown water New Yorkers see from their windows into something more akin to what comes out of their taps. All told, the pool will clean more than a half-million gallons each day, drawing water from the river into the pool and recirculating it into the river.

The specifics are still up in the air, says Nancy Choi, a senior engineer at Arup, an international engineering firm that was the team's first partner on the project. Choi expects the final pool to have two or three different types of geotextiles in its walls.

"Getting all of the obvious floatables out of the water" — the garbage, the animals — is the first step, she says, and is something that can be accomplished with a more porous material.

Chemicals and bacteria, on the other hand, will require something much tighter. "A coffee filter is a good way of thinking about the fabrics," Choi explains. "It keeps the coffee out, but it allows the water to pass through."

The challenge, says Columbia University professor and + POOL advisor Wade McGillis, is finding a sweet spot that keeps the undesirable things out while permitting the water to steadily flow in: "It's a trade-off between how fine the filter is for particle and pathogen removal, and having something that can actually seep."

The team is adamant that the pool must do its work without the help of chlorine.

"It sort of defeats the whole purpose for us, of swimming in natural water," Wong says. "And we don't want to introduce all these chemicals to the river."

It's a tall order to spin appealing summer fun out of a river that's known more as a punch line ("Luca Brasi sleeps with the fishes") than a source of recreation. It's an even taller order when it must be done without the help of the chemical cleaner used almost universally in conventional swimming pools.

And it's not just the water that needs to be reckoned with. People are dirty, too. Especially in a New York summer, when bathers will enter the pool coated in sweat and rank city air.

The members of the + POOL team have thrown their faith behind their filtration system. The walls of their West Village workspace are covered with to-do lists, diagrams of materials, and plans for the final, four-armed structure: each axis measuring 50 meters end to end, with areas for lap-swimming, lounging, sports, and children. For the sake of not overexerting the filters, Wong says, the pool will stay shallow throughout, likely about five feet deep, with a shallower kids' section. In the drawings, a floating walkway connects the shore to the pool, which will extend anywhere from 100 to 300 feet into the river, depending on the site.

Also scattered throughout the office are photos from summer 2011, when the team conducted its first filtration test at Brooklyn Bridge Park, pumping water from the river into and back out of a giant tank onshore. That was the first step toward actually building the pool. The second came in April, when Wong, Coates, and Franklin launched Float Lab, a small floating dock off Hudson River Parks.

Thirty feet long by 10 feet wide, with a garish blue plywood top supported by a plastic bottom, it's designed to look like any other floating dock but for the three squares cut into its middle. Those contain aluminum frames, each five feet deep, which in turn contain the heart of the project: three tubs, each created from some combination of different filter materials of increasingly fine mesh.

Just getting the Float Lab into the water required permits from the Army Corps of Engineers and the New York Department of State. The Hudson River Park Trust, the city-state partnership that operates the five miles of parkland, had to grant access to the pier. Two naval architects pitched in as well, and secured permission to assemble the rig at the Liberty Landing Marina in New Jersey. River Project, a Manhattan–based environmental group, is providing lab facilities. The partners check in with a handful of city agencies, including the health and parks departments, to keep them up to date.

Throughout the summer, the team will evaluate the water in each tub for everything from temperature and pH to algae and bacteria content, looking at which combinations of filters create the highest water quality across the board. They'll also chart river currents, rainfall, and anything else that affects the Hudson's behavior. In late summer, Wong says, they'll tow Float Lab around the tip of Manhattan to the East River and restart the process, working into the fall.

For the time being, it's a game of wait-and-see. The success of Float Lab's filters will determine the success of + POOL.