Protecting Iowa’s lone urban trout stream is tricky

There were recently two mass trout killings within a year at McLoud Run, a cold water stream in the heart of Cedar Rapids that is regularly stocked with fish by the state.

While that was the first time that trout kills have been reported so close in time at the stream, they are a grudgingly accepted reality of maintaining a sensitive fish population in Iowa’s second-largest city.

“All you need is one bad slug of water going through, and the fish can’t handle it,” said Paul Sleeper, a fisheries management biologist for the Iowa Department of Natural Resources.

Trout are especially sensitive to water temperature and contamination, and in Cedar Rapids the threats are numerous. The two-and-a-half miles of McLoud shadows Interstate Highway 380 and is in close proximity to businesses, industry and houses, with ever-present pesticides, toxic fluids and warm water runoff from concrete. There are about 30 outlets into the stream that drain stormwater from the area.

“Somebody could dump something a mile up in a residential area, and it could get down a storm sewer,” Sleeper said. “And it could be very difficult for us to tell where it came from or even what it was.”

But there is another threat that has proved most deadly in recent years: the city’s drinking water.

Municipal water is commonly treated with chlorine to kill bacteria. The concentration of the chemical is small enough to be safe for humans, but it is high enough to readily kill trout by damaging their gills.

There is no concentration that ensures the safety of drinking water and of trout, Sleeper said.

The most recent large release of drinking water to the stream in January might have killed all of its trout in the affected segment, which was nearly all of the stream, he said.

Iowa’s only urban trout stream

State conservation officials have worked for decades to maintain and restore the dozens of trout streams in picturesque northeast Iowa. They have historically been harmed by erosion and pollution from agriculture.

The DNR stocks the streams with hundreds of thousands of trout each year, and the streams increasingly have fish populations that are reproducing naturally.

That is unlikely to happen at McLoud Run, Sleeper said, so the department will continue to regularly stock it to encourage people to fish for trout. It is the southernmost such stream available in Iowa and is easily accessible. Sleeper said it might inspire anglers to travel to the mountainous hills, exposed bedrock and clear streams farther away.

He said McLoud also serves as an “outdoor learning classroom” for students at local schools and colleges.

The DNR stocks it each year with thousands of trout, ranging in size from fingerlings to adults. McLoud is a catch-and-release stream.

Repeated fish kills

McLoud is poised for increased restocking this year after a water line broke in a vacant commercial building next to the stream and released an estimated 450,000 gallons of water in late January.

The DNR believes water in a fire suppression line in the building froze and then leaked when it later thawed, said Brenda Streicher, an environmental specialist for the department who investigated the incident. The building is about 250 feet from the stream.

Sleeper found 336 dead trout after the incident but said many more likely perished because of the chlorine. The upstream location of the water leak caused it to affect a longer stretch of McLoud than past incidents, and Sleeper did not see any live trout.

“It is very challenging to locate this type of leak and mitigate in a timely manner,” said Kelli Albert, a spokesperson for the Cedar Rapids Utilities Department.

The city is well aware of the threat its water poses to the stream and has procedures to dechlorinate it during planned and emergency releases, she said. The city has been fined twice in the past six years for fish kills the water has caused in McLoud.

Despite that, the city has done “an excellent job” trying to protect the stream, Sleeper said.

Not long before the most recent incident, the city agreed to pay about $24,000 for a March 2023 fish kill that resulted from a water main break. City workers sought to limit the impact of the leak on the stream by adding dechlorination tablets to the water, but it still killed about 1,400 trout, according to a DNR order.

In 2017, a water valve broke during construction work and leaked up to a half million gallons of water. That killed about 1,300 trout, and the city paid about $23,000, according to another DNR order.

In 2016, a contaminant killed several hundred trout, but the department was unable to determine the cause, Sleeper said. There are likely other smaller fish kills that go unnoticed.

“It just depends whether somebody actually reports them,” Sleeper said. “Some of it can just be a few fish here and there, and they can get cleaned up pretty quick by predators.”

Albert, the city spokesperson, said it isn’t possible to make Cedar Rapids drinking water safe for both humans and trout, and it is infeasible to divert stormwater runoff away from the stream. The surrounding area slopes down to the stream.

“We’re constantly improving our practices, systems and approach to control these types of events,” she said of water leaks.