North Denver’s largest lake has been through a lot lately. Last year, thousands of fish washed ashore in the largest fish die-off on record. This year, a deadly algae bloom closed the lake for several weeks until conditions improved. Now the city is looking at a number of options to keep the lake healthy (and open). Cinceré Eades, the Parks Resilience Principal Planner for Parks and Recreation, talked with The Denver North Star about what the city is doing now and what they’re considering for the future.
One of the biggest problems, according to Eades, is that sections of the lake have an estimated 10 feet of sediment, leaving the average depth only three feet. Shallow waters heat up more quickly, which is a contributing factor to unhealthy types of algae growth. When shallow waters aren’t circulating enough, the problem becomes worse. While they are analyzing long term solutions, the department has installed Solar Bees on the lake, small solar powered devices that draw in and pump water, distributing cooler temperatures. They can’t solve the problem alone Eades says, but they can help with hot spots. It’s part of what she calls a “holistic approach to managing the lake.”
The pump systems, like the bees, focus on the top few feet of water only and don’t disturb the sediment. That’s important, she explained, because too much disruption of the sediment can also aggravate the issues. That answer likely comes as a disappointment to power boaters, whose boats move the water, but sit deeper, which churns up more sediment. Powered boats are still banned from the lake, though human-propelled small crafts like kayaks are allowed.
Parks has added two more monitoring sites to the lake to help spot problems earlier and recently doubled the lake management staff. They are evaluating how much more sediment is entering the lake and how much has been there for decades, which will help them make decisions down the road.
Part of their decisions may depend on Denver’s neighbors too, as water in Jefferson County drains into the lake. “Sloan’s Lake is the bottom of the basin,” Eades explained. “Denver Parks is evaluating partnerships to collectively manage Sloan’s Lake as a regional asset.”
As part of the evaluation process, they’re mapping the bottom of the lake and getting estimates on different options. One of those that’s widely discussed is dredging: a process of removing sediment. Sometimes lakes are drained first but not always. Dredging estimates vary and Parks hopes to have more details next year, but the sum of $50 million has come up in several conversations. Eades said that decision is a “political conversation above my pay grade.” To put that number in perspective, the 2D bond voters just approved was for $52.7million and is slated to fund eight different parks projects (including renovating the Sloan’s Lake boathouse, which has an estimated price tag of $7million). The entire Parks section of the Parks and Rec budget is only $42.7Million in 2021, so dredging would almost certainly have to come from some specific funding source (such as a city bond or regional investment).
Asked about the urban legend that there’s a large boat that sank in the early 1900s at the bottom of the lake, Eades said their mapping hasn’t shown anything of the sort, though of course draining and/or dredging could reveal any number of things about the lake’s past. It could be the largest lost and found in the city’s history.
Sloan’s Lake is one of the most frequently asked about topics in North Denver and we’ll bring you more updates as there are further developments.