MINNEAPOLIS (WCCO) – New challenges are popping up at a brand new Minneapolis pool.

Just two days after its opening, the Webber Park pool in North Minneapolis implemented some new safety rules.

The $6 million pool is the first public swimming pool in North America to have a natural filtration system that uses plants in a nearby pond rather than chemicals to treat the water.

During the first couple days the pool was open, there was a drowning scare and pool staff say they noticed some unattended children under 13 years old.

The city says parents and chaperons were leaving the pool area without the children, which is unsafe at any pool or near any body of water.

Nicholas Williams of the city’s parks and recreation board said Webber pool is unique because it is within walking distance of several neighborhoods and has a nearby recreational center and park. Williams says there has not been a need to implement such a policy at other Minneapolis pools.

Williams said he can understand why some chaperons may think of sending their children to the park to play, but they can’t be unattended at a pool.

“There are certain dangers near any body of water, and we need parents and chaperons to always be watching their children closely,” Williams said.

On Sunday, parks officials implemented a new rule: Staff issue each adult chaperon a wristband inscribed with the number of kids they brought under the age of 13. The chaperons are not allowed to leave unless they are accompanied by the same number of children.

The Minneapolis Park and Recreation Board said the clear water in the natural pool looks green because vinyl lining on the bottom of the 11-foot-deep pool is green.

There is also some algae in the water, like in most lakes, which staff works to eliminate.

Since its opening, staff said the pool has been very popular, drawing in around 1,000 people per day. The pool’s capacity is 500.

Williams said the hope is the wristband rule will help lifeguards get proper support from chaperons and parents to keep an eye on the children in the crowded pool that looks more like a lake.

The Minneapolis Park Board said swimming lessons — with scholarships available — will be offered soon at the Webber pool.

This summer the pool is only open Fridays through Sundays because it takes a few days for staff to manually clean the bottom of the pool.

The city hopes to have a self-cleaning system in place for next summer so it can be open every day.

The Webber pool will be holding an open house from 4 p.m. to 6:30 p.m. this Thursday.