What will it take to make Sloan’s Lake deep again?

The view of the park from Cohen’s back window looks similar to how it did from her childhood home, located on the opposite end of the park. The lake still sparkles in the sun as parents push strollers and neighbors walk their dogs. Cohen catches pink sunsets set against the mountains to the west of the park almost every evening.

But changes to the lake, and surrounding neighborhood, are just as noticeable to Cohen as what has remained the same. 

When Cohen was a baby, she said, her parents could push her in a stroller across the frozen lake in January and February. As a kid, she and her friends ice skated on the frozen lake after school.

Over time, stormwater runoff carried soil, debris and pollutants from surrounding streets into the lake. The debris has settled on the lake floor and made it much shallower, reducing oxygen levels and causing the water to heat up faster. 

A Denver Parks and Recreation assessment in January found that sediment collecting in the bottom of the lake has brought its depth to 3.5 feet. In the 1900s, it was 15 feet deep. 

The lake’s current warmer, nutrient-rich conditions create a perfect environment for blue-green algae (cyanobacteria) to thrive. These algae blooms deplete oxygen, harm aquatic life and can produce toxins that make the water unsafe for people, pets and wildlife.

“Sloan’s Lake used to be the center of recreation in Denver,” Weaver said. “And there are all kinds of things that happened there that we can bring back if we can dredge it, like swimming and a beach.”

Dredging the lake and removing all of its sediment is the key to returning the lake to 15 feet of depth and making it safe for swimming again, said Weaver, whose estimates and advocacy are based on findings from Denver Parks and Recreation and the Mile High Flood District. Both agencies have identified dredging as essential to restoring the lake’s long-term health but cite budget constraints as the primary obstacle. The Denver Parks and Recreation Environmental Analysis also identifies dredging as a necessary solution.  

However, the bond package headed to voters in November does not include funding to dredge the lake.

The Sloan’s Lake Park Foundation planned to apply for grant funding from the United States Environmental Protection Agency, but that agency has canceled about 400 grants and $1.7 billion in aid since January.

“We may not have another six, eight or 10 years to dredge,” said Weaver, who lives near the lake and has been involved in efforts to fix it for about 10 years. “When we think about a puddle that’s just sitting in the sun for days on end and drying up, that’s what we’re risking.”

Denver Parks and Recreation has not explicitly labeled Sloan’s Lake at risk of fully drying up, but its environmental assessment highlights that the lake’s decline from 15 feet to 3.5 feet deep has fueled low oxygen levels and harmful algae blooms.

At least 2,000 carp and crappies died in the lake in 2024, when temperatures were around 100 degrees outside and 85 degrees in the water. The parks department pumped in cold water from the Sloan’s Lake Park irrigation system to prevent more fish from dying.

The Colorado Dragon Boat Festival, which celebrates Asian American, Native Hawaiian and Pacific Islander culture in the Rocky Mountain region, has been held at Sloan’s Lake Park since its inception in 2001 but took place in September this year after the city barred all events on the water due to toxic algae bloom. The Denver Gazette reported that festival organizers have considered moving its location if the lake’s conditions don’t improve.

In the absence of EPA grants, Weaver knows finding $120 to $130 million is a steep task. Denver operates the park, and Denver Parks and Recreation is primarily responsible for it.

A report from several city departments identified repairing damaged banks, installing wetland plants, increasing riparian buffers along the shoreline and eventually dredging the lake bottom as necessary goals.

Stephanie Figueroa, Denver Parks and Recreation spokesperson, said the agency could not comment on the specifics of the project’s progress unless and until the bond passes.

Lakewood, Edgewater, Wheatridge and Denver — which all surround Sloan’s Lake — are also partners in the Mile High Flood District, which assists with water quality projects and provides oversight to ensure the lake can manage runoff from the cities. The district provides funding through partnerships and cost-sharing programs, and Weaver is hopeful it could provide some funding to the dredging project. Still, he knows it's unlikely the surrounding cities or the state could support the multi-million dollar project without the federal government’s help.

Colorado Parks and Wildlife used to stock the lake with walleye, catfish, perch and trout and stopped doing so in January 2024. Currently, catfish and carp still swim in the lake, and fishers are still permitted to fish.

“I would love to see the lake be swimmable and fishable like it was decades ago,” said Glenn Whitman, who lives four houses north of the lake and volunteers as the chair of the Sloan’s Lake Park Foundation board.

“We have to create more oxygen for the fish and by doing that, the lake will also be healthier for humans,” he said.