Diving into an urgent repair

“Nothing’s easy,” Chad Paup, an Iowa DNR wildlife biologist for 23 years, said.

It certainly describes a complicated repair project the Iowa Department of Natural Resources has been performing on Green Valley Lake. In an unusual situation which requires unusual action, the lake has been the site for a dive team repair to stop escaping water.

With factors ranging from the approaching hunting season, aluminum sulphate application and the complications involved with sending a dive team for underwater repairs, the operation will be anything but easy.

Mitchell Marsh flooding

Part of the Iowa DNR’s involvement in Green Valley Lake involves managing water for the various wetland areas surrounding it. One of these areas is Mitchell Marsh, a 300-acre area used as public hunting grounds for waterfowl and pheasants.

To maintain the area and the 60 acres of water within the marsh, which is a part of the 250 acres of Summit Lake, the DNR annually floods the marsh with water from Green Valley Lake through the state park dam.

Flooding the marsh encourages migrating waterfowl to settle in the fall, making the area perfect for hunting. It’s a tradition for the area and a part of an annual cycle of area maintenance. During the spring and summer, the marsh is dry, encouraging wetland vegetation.

This year, a delay has been put in place as the DNR proceeds with construction. A 72-feet pipe that’s been in use for over 30 years for flooding the marsh will need to be replaced as it approaches the end of its life.

As a part of the replacement, four other tubes will be replaced which are used for overflow. These tubes transport water from Mitchell Marsh to nearby Summit Lake.

The flooding can take place over two days; as of now, the process depends on when materials can arrive at Green Valley and when repairs to the lake’s sluice gate can be performed. Paup says the flooding will most likely still take place before the hunting season in October and November.

The sluice gate

However, that’s only “one of the pieces of the puzzle,” according to Paup. The other pieces lie on the other side of the pipe within Green Valley Lake, and are far more complicated than a simple replacement.

The lake’s sluice gate, which controls how much water is released from Green Valley, is not operating correctly. The gate works from a crank in the Green Valley dam which controls a vertical gate, blocking water to raise or lower the lake’s elevation.

Installed in 1952, the sluice gate is used regularly for various facets of lake management, including the flooding of Mitchell Marsh. Due to the consistent use, the gate stayed in relatively good shape as deterioration was limited.

After over 70 years, the gate has finally shown its age. The problem was initially unknown.

“We’ve been trying to figure out whether it’s off-track or actually broken, but we’ve got some water coming through and it’s spraying enough water where we can’t see what’s happening there,” Paup said.

Either way, there’s a significant amount of pressure built in the sluice gate. As the structure typically holds water within Green Valley Lake, a failure could mean losing control of the water.

Alum application

Usually, this problem could be solved by removing the water within the lake. This has been done in the past to monitor sediment or remove fish. However, with uncertainty to the integrity of an aging structure and recent alum applications to the Green Valley Lake, this option isn’t viable.

Instead, the DNR has secured the help of contractors and the Ringgold Community Water Emergency Team to create a diving operation to plug the sluice gate. It’s a complicated job.

“Nothing’s easy,” Paup said. “We don’t want to just play with that sluice gate, which is extremely hard to maneuver up and down safely.”

Green Valley Lake is in the middle of an alum application, where aluminum sulphate is injected into the lake’s water. The process reduces phosphorus release in the lake with the eventual goal of restoring the water quality in the lake.

In order to do this, regular scheduled applications into fall 2026 are planned, with the first series of applications having already taken place this summer in May and a second series in October.

To have the intended effect, water in Green Valley has to remain undisturbed so the alum settles at the sediment level of the lake. The water must not be removed.

“We have such a small watershed in our lake and, with water quality improving, having that application and money spent on it, it’s a big deal,” Green Valley Park Ranger Jason Hyde said, calling the planned diving operation “unprecedented.”

Combine all factors, including the drought affecting the nearby Three Mile Lake, and simply draining the lake is not an option for the DNR.

Paup described a scenario where the sluice gate opens for the Mitchell Marsh flooding, but is unable to close. The water in Green Valley would be lost, and the contracts and funds spent for the alum application would be void.

Diving in

Requiring the help of the Ringgold County dive team, which includes members from across Southwest Iowa, the first operation took place last Friday. Three divers, along with members of the Iowa DNR and park service, installed a plug in the sluice gate to stop the water spray and find the solution.

One of those divers is Creston Fire Assistant Chief Daniel Stull. Ever since receiving his license in 2010 while working for the fire department in Ringgold County, Stull has assisted with the Ringgold County Water Emergency Team.

As part of the dive team, Stull has assisted with search and rescue and body recovery, as well as pond fixes for private individuals. He said working in Green Valley would most likely be easier.

“Once you get used to that, you know you have a job to do underneath the water,” Stull said. “You’re comfortable in the water, you just go down and handle it. There’s always some investigating.”

Green Valley Lake was originally built through a three-entity collaboration: the state of Iowa, the city of Creston and Central Iowa Power Cooperative, known at the time as Southwestern Federal Power Cooperative. CIPCO still plays a notable role with Green Valley, as they provide water for CIPCO’s generator, and was in contact during the first dive operation.

CIPCO has the ability to shut down water flow pumps, and temporarily did so during the first dive. Safety is a number one concern for the dive team.

“We started this over a year ago, starting communications with [SIPCO] and saying this is something we need to do,” Hyde said. “These relationships that we’ve built, keeping touch; this isn’t willy nilly, this is precise.”

The dive team assembled consists of volunteers from all forms of emergency occupations, from firefighters to EMTs. It’s a unique situation for most. To the DNR and diving volunteers used to the call of the wild, there’s a certain appeal to the project.

“To some extent, when you’re working in nature and on the landscape, that’s part of enjoying the work,” Paup said. “From cutting trees in the dead of the winter — it’s a gorgeous, cool time of year — to creating a fish habitat on the ice; I can make a long list."

On Friday, the team dove for a first look and set buoys for the project. To plug the gate, an air bladder was deployed into the sluice gate’s 36-inch tube, allowing for divers safely maneuver an inflatable plug.

With the pressure built over time, the sluice gate’s slot hole opened after the tube was plugged, meaning another dive is scheduled for additional work this Thursday.

These operations, along with the other work the DNR performs to keep state parks like Green Valley and other local areas running, mostly happens without fanfare or celebration. With seasonal workers behind the scenes, these areas wouldn’t be the recreational hot spots they’ve become.

“[The seasonal help] all summer are weed-whipping, mowing, trimming trees and cleaning bathrooms,” Paup said. “They’re like busy bees, all over the park and from here to Nine Eagles State Park. And most people don’t even see them; without them, this place would look like a jungle.”