A local working group has the difficult task of trying to keep as much sediment as possible from flowing into the Shoshone River and stacking up behind the Willwood Dam. Currently, they’ve set their eyes on an old bentonite mine outside of Cody.

Willwood Working Group 3 formed in 2017 after a large amount of sediment was released during repairs to the Willwood Dam, creating a hazard to aquatic life downstream. The water turned to sludge, impacting recreation and agriculture. 

Working Group 1 dealt with the initial cleanup, and Working Group 2 continues to study how to mitigate sediment releases during operations at the dam south of Powell. 

As for group 3, Chair Carmen McIntyre said they’re tasked with trying to “understand, document, and where feasible, mitigate sediment influx into the lower Shoshone River which results in sediment buildup behind the Willwood Dam.”

This year, the group began exploring mitigation strategies on a reclaimed bentonite mine the group identified as an important contributor to sediment into Sulfur Creek, a tributary of the Shoshone. 

The mine, which is located west of Cody off Diamond Basin Road, was released from bond by the Wyoming Department of Environmental Quality and the Bureau of Land Management in 1998, having ceased operations some time before. The reclamation on the mine was done according to industry standards and regulations at the time, which were more lax than they are today. 

The mine is 10 acres of noticeably bare clay and rock surrounded by shrubs and grasses. 

“It looks nothing like the surrounding area,” said Dave Sweet, a member of the East Yellowstone Chapter of Trout Unlimited, which is just one of the organizations contributing time and resources to Working Group 3.

Sweet points to rocks now perched on pillars of dirt to illustrate the amount of sediment flowing off the site. He said much of the rock was once on the surface or just below it, before water and wind eroded away the sediment underneath. Further down the slope of the mine, closer to the creek, are foot-wide tunnels where silt has eroded away.

Bentonite mine operators were required to set aside topsoil for reclamation work, but the area didn’t have much topsoil to begin with. So what amounts were used in reclamation were subsequently washed and blown away.

Members of the BLM, Trout Unlimited, Merit Energy and local conservation districts visited the site this summer and decided to take on what McIntyre described as “an adaptive management approach,” which has been effective in other locations.

In summer, the group’s partners submitted a proposal to the BLM’s Cody Field Office to evaluate approaches to promoting native vegetation on the site.

“Because of the lack of vegetation on this area, silt, sand, and clay sediment has been transported offsite over the years during precipitation events,” McIntyre said. 

The group is using a three-fourths acre section of the 10-acre site as a study area. They’ve divided it into three subplots and a control plot. Last month, they began testing combinations of erosion control and seeding techniques to assess which are the most effective at facilitating vegetative cover. 

Creating the test plots was a bit of a challenge. A team of volunteers from Trout Unlimited, as well as staff from the BLM and Wyoming Game and Fish Department, were at the site in October, laying out native seed mixes, mycorrhizal fungi powder, erosion control blankets and straw wattles. They also applied hydromulch to the seeded areas, which will hold the seed to the soil and give it a chance to germinate. 

Without a water source to draw from, the team had to transport water a few miles from Diamond Basin Road to the remote mine site, along with all the machinery and other materials for the seeding and mulching.

There was a lot of trial and error, such as figuring out what level of mulch consistency would flow through the pipe but still put an adequate layer on the test plots. 

Each plot will be evaluated for seed germination and growth at one month, six months, 12 months and 24 months. At that point, the group hopes to have a better understanding of what methods work. They can then replicate the best approaches across the whole mine — and there are other bentonite mines in the area that might benefit from the research as well. 

Sweet pointed out that most of the people building the test plots are volunteers, without which the Willwood Working Group 3’s efforts wouldn’t be possible.

“A big thanks to them. That’s first and foremost,” Sweet said. 

He said they’ve already learned a couple things: For instance, if they do replicate the seeding across the entire site or other mines, they’re going to need a larger hydromulcher. It took several days to cover the three-fourths-acre area. 

“We could only mix up 100 gallons of mulch at a time, and that was very time consuming,” Sweet said.

Fortune was on the group’s side, however. The weather cooperated to not only allow them to complete the work, but provide a good rain afterwards.

“That was perfect. That will help that seed germinate,” Sweet said. “Now, we’re just going to wait and see.”

In the future, McIntyre said the site might serve as an outdoor classroom for students to study geology, hydrology, botany, soil science and other topics that focus on natural resources and their importance to the environment. 

The seeding effort isn’t the only erosion control action that’s been taken at the site. The BLM installed rock check dams in 2009, which McIntyre said continue to trap sediment and slow the velocity of the water draining down into Sulfur Creek. And last summer, BLM employees repaired an area of tunnelling and gullying near one of the dams; they also reconstructed a channel and installed a series of dikes to help mitigate erosion.

McIntyre added that the BLM has been very supportive of the group’s work, which would have been much harder and taken a lot longer without it. 

“They’ve been great partners,” she said.

With an area stretching miles along a wide corridor along the Shoshone River, Willwood Working Group 3 (WWG3) includes work from the Wyoming Department of Environmental Quality, Cody Conservation District, Powell Clarks Fork Conservation District, and the Bureau of Reclamation.

“The WWG3 is excited to put planning efforts of the last several years into action and continue its collaborative efforts with the BLM, State of Wyoming, and others to address sediment loading to the Shoshone River and its tributaries,” McIntyre said.

Anyone interested in learning more about the group can contact McIntyre at 307-578-8335.