The Calumet Water Reclamation Plant received 3.5 billion gallons of water during the historic flooding over the Fourth of July weekend this year.

But the plant didn’t reach half of its capacity at that time.

Engineers at the plant said that’s by design. A WBEZ analysis found that roughly 172,000 properties in Cook County have a high risk of flooding. Another analysis shows that from July 2-18 this year, there were more basement flooding reports filed with the city’s non-emergency helpline than in 2021 and 2022 combined.

“I’ve been in the wastewater industry for 24 years now. And it seems like more and more events we’re having,” said Dan Mikso, one of the engineers at the plant.

Despite more frequent floods, plant officials said they are ready for the challenge.

The plant is responsible for cleaning the stormwater across Chicago’s South Side and the nearby suburbs that often is contaminated by sewage to be sent back out into the waterways.

It has extra pumps and tanks on site that are used specifically to handle any of the excess rain that comes through.

“People ask, ‘Why do you need the plant this big?’ We have to be prepared, because if we don’t have the plant this size, sewage is either going to back up into people’s homes, or it’s going to be released into the receiving waters,” Mikso said.

The plant has 100 tanks of varying types in total and can treat and clean up to 430 million gallons of water per day.

And they are prepared to cover the added energy costs when using these backup devices, without it hurting their budget.

The plant is able to use the fats, oils and greases that come in through the sewage to create methane, which powers the facility.

“It ultimately lowers the amount of cost for the taxpayers of Cook County, so we don’t need to purchase natural gas,” Mikso said.

If there is a storm large enough that the extra pumps and tanks manage to reach capacity, the plant also has a quarry 350 feet below ground that can hold up to nearly 8 billion gallons of water.

To date, the quarry has never been full.

As events like the ones this summer become more common and the extra equipment is used more frequently, Mikso said future proofing the plant is at the forefront of his mind.

“We have to do our part now so that the future people who take this over can be ready for these more and more events if it keeps occurring like this,” Mikso said.

Part of those efforts for the future include ensuring the plant will be fully staffed in the years to come.

“I try to stress to younger people when we have high school students come in here that it’s a rewarding job because you can see you are making a difference,” Mikso said. “Instead of, ‘oh yeah, I’m just here pushing paper,’ you can actually see the difference you are making.”

Noah Jennings is WBEZ’s afternoon news producer. Follow him @noahajennings.