To build levee, Cedar Lake water will be pumped into Cedar River

CEDAR RAPIDS — Within the next few months, 30 new wells will pump millions of gallons of water from a sectioned-off portion of Cedar Lake into the Cedar River each day.

The “dewatering” project will pave the way for a levee to stretch more than 2,000 feet across Cedar Lake’s west bank.

“Originally, the flood control system stopped south of this area. The recreational and community opportunities were such that we were able to move that protection northward” to include Cedar Lake, the city’s community development director Jennifer Pratt said.

“That is extra insurance against future flooding. And that is great for long-term water quality.”

The urban lake was previously used as a cooling pond for the adjacent Alliant Energy coal-fired power plant, which has since been demolished. The company sold the lake to Cedar Rapids for $1 in 2019.

Since then, the lake has played an integral part in the city’s ConnectCR project — and now, it represents another piece of the city’s $750 million flood control system master plan coming to fruition.

Cedar Lake Levee Dewatering Project

The Cedar Lake dewatering project consists of 30 wells that suck water from a partitioned portion of Cedar Lake and pipe it over to the Cedar River.

Source: Iowa Department of Natural Resources

From lake to levee

At their basic level, dewatering projects remove groundwater and surface water from sites to dry out and stabilize them, readying areas for construction. It’s a necessary step for the Cedar Lake levee, which will overlap with a 100-foot-wide chunk of the lake’s current western edge, estimated Cedar Rapids public works director Bob Hammond.

Contractors broke ground around a year and a half ago to separate the stretch of water from the rest of the lake. They created a causeway by dumping large amounts of dirt in a line across Cedar Lake, running parallel to the shore.

Thirty wells — half of them rooted in the causeway, half of them rooted in the original shoreline — will pump around 600 gallons of water a minute from the site. The water will flow into underground pipes that eventually dump into the Cedar River. Altogether, it will amount to around 25 million gallons of discharged water per day.

Once the water is sucked from the area, there will be a 3-to-4-foot layer of “goo” along the bottom of the area, Hammond said. The wells will continue running until the muck — too unstable to build atop — is dry enough to be excavated.

To construct the levee, layers of earthen, clay-like materials will be compacted on top of each other to reach around 22 feet tall — similar to the height of Quaker Oats’ flood wall. It will take around two years to complete.

“It will effectively be, then, the west bank of the Cedar Lake,” Hammond said.

A discharge permit granted by the Iowa Department of Natural Resources said the project could start discharging into the Cedar River on March 1. The wells are already constructed, but the piping still is being completed. Pumping is expected to begin in the next couple of months, Hammond estimated.

Minimal water quality impacts expected

The Cedar River wasn’t the original destination for the discharge from the Cedar Lake dewatering process. Rather, it was the McLoud Run — Iowa’s only urban trout stream that runs parallel to I-380 before cutting into the Cedar River.

However, sampling revealed elevated levels of ammonia nitrogen and iron in one of the dewatering wells. Amounts of other potential contaminants from the lake’s industrial past — like volatile organic compounds or pesticides — were not anticipated to impede water quality standards.

The contaminated groundwater had no direct correlation with the lake’s surface water, Hammond said. But the city still needed to find an alternative outfall.

Among the options considered, releasing untreated lake water into the Cedar River was deemed the most reasonable and affordable option at $1 million. Plus, the river’s larger flow can dilute pollutants better than McLoud Run, Hammond said, so the discharge shouldn’t majorly impact the ecosystem. The outfall into the river is downstream of any active Cedar Rapids wells that pull the city’s drinking water.

The discharge permit administered by the Iowa DNR sets monthly limits on the amount of ammonia and iron released into the Cedar River. A maximum of 12.9 milligrams of ammonia per liter, or 2,700 pounds a day, can be released in June. The project can discharge 10 milligrams of total iron per liter, or 2,085 pounds a day, year-round.

Contaminant levels should easily adhere to those discharge limits, Hammond said.

Although ammonia levels reportedly reached 13.1 milligrams per liter, average concentrations were around 4 milligrams per liter. Similarly, while total iron concentrations peaked at 40.9 milligrams per liter, their levels averaged 5.3 milligrams per liter.

Ammonia and iron levels in the discharge will be sampled every week, and if the contaminants impede their limits, contractors can shut down pumping from individual wells.

“This isn't large quantities of this stuff,” Hammond said. “It's just that it was picked up and sampled, and it was determined that we really needed to have an alternative.”

Cedar Lake is used for fishing and recreation. It was taken off the state’s impaired waterways list in 2015, and a 2019 Iowa DNR study found its waters were safe for recreation.

Because of the investments in flood control and water quality — like the stormwater mitigation project planned for the water body’s south cell — Cedar Lake qualifies for the Iowa DNR’s lake restoration program.

“We would work with the DNR hand-in-hand in figuring out what is the long-term lake restoration plan,” Pratt said. “But we had to get these protective components in place before we were eligible to work with the state.”

Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; brittney.miller@thegazette.com