On summer’s high holiday with temperatures pushing triple digits, the Webber Park pool in the north Minneapolis remained closed to swimmers, as it has been for days, including last weekend’s sweltering heat.

The pool has not been open since June 24, due to water-quality issues.

The ill-timed closing is the latest hitch for a pool that is supposed to be both an innovation in pool engineering and an asset to North Side neighborhoods.

“The reason people get upset when it’s closed is that it’s hugely popular when it’s open,” Minneapolis Park and Recreation Board spokeswoman Dawn Sommers said. “We’re as disappointed as the public.”

When the Webber Park pool debuted in late July 2015, the project was over budget and overdue by almost two years. Still, it received national acclaim for the engineering and science innovations that made it the first-of-its-kind freshwater outdoor public pool in the United States. The water in the 21,000-square-foot pool is cleaned without chemicals by cycling through an adjacent natural pond.

The natural cleaning process, however, can be less efficient than the traditional chlorine used in pools. Heavy rainfall challenges the pool’s ecosystem. If a swimmer urinates, vomits or deposits fecal matter in the pool, the delicate balance is upset and the pool must be closed. A regular pool can get an extra dose of chlorine to take on the contamination, Sommers said. “There’s a ton of benefits of a natural swimming pool. The downside is it’s a small lake,” she said.

When the old Webber Park pool closed in 2010, Park Board members sought to give residents on the North Side something new, a fresh amenity like the beaches available throughout the southern part of the city. The pool, at 4330 Webber Pkwy., is free for open swim and was a hit from day one, often reaching its capacity of 500.

The pool has something for everyone — a lap area with lane lines, a deep area with a diving platform, a zero-depth entry for youngsters and grassy areas for sunbathing.

Before the pool ever opened, there were problems with ducks and toads depositing fecal matter in the cleansing pond. The price tag climbed to $7 million from the initial estimate of $4 million during planning in 2012. Webber Park’s 500,000 gallons of water gets circulated between the pool and the pond, which has some 7,000 aquatic plants rooted in limestone and granite gravel, according to the Park Board’s website.

Unlike natural lakes, which are bigger and allow more dispersal, contaminants get concentrated and become problematic at Webber Park. At city lakes, some beaches can be closed for water problems while others at the same lake remain open, Sommers said.

She also pointed out that the city is adhering to stricter, European standards of water quality for Webber Park.

As of Thursday afternoon, a large “pool closed” sign hung on the chain link fence that surrounds the pool, which sat still and empty as two blue-shirted staff members walked the deck. Children played under shade trees in the nearby grass.

Earlier in the day, new water samples were taken and will be analyzed at a lab by noon Friday to determine if the pool can reopen for the weekend.

An explanation of the Webber Park tests and most recent findings is online. The testing of all city pools and beaches looks for indicators of fecal matter and excess sediment.

Webber Park pool has been closed 10 days for water quality, more than last year when it was closed for six days all season for that reason, Sommers said. “It’s very unfortunate,” she said. “We can’t control when we get that deluge of rain.”

Hennepin County Commissioner Mike Opat, who lives nearby, said he is not pleased, noting the county’s $300,000 contribution to the project. “It is truly disappointing to drive by, as I do most days, and see it closed,” he said. “The recent heat spell makes that especially distressing.”

Roberta Englund, executive director of the Webber-Camden Neighborhood Organization, isn’t much of a swimmer, but she said she likes the pool. The current run of closings is a “complex” concern, she said. “Is it worth it?” she asked. “I think that’s still up for debate.”

When it does reopen, to avoid getting sick, swimmers should adhere to the rules: showering before, using the restrooms and refraining from drinking the pool water.