We've had a lot of meetings, a lot of communication, and we intend to continue to communicate.”

US Holcim Aggregates Manager Tom Schmit

Now open through Jan. 17, comment on the Nelson Backwater Mine EIS can be made via email to eis@cottagegrovemn.gov, or by mail to:

Ms. Emily Schmitz, Community Development Director

12800 Ravine Parkway South

Cottage Grove MN 55016

HERO Training Center
10125 85th St. S
Cottage Grove, MN 55016
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Appearing to a packed house Dec. 19, Holcim US laid out its Nelson Backwater Mine Proposal at the HERO Center in Cottage Grove. Now in the Environmental Impact Statement (EIS) phase of the project, the proposal comes as the current mine on Lower Grey Cloud will exhaust itself in four to five years.
Proposed mine details (including alternates) were presented by US Holcim Aggregates Manager Tom Schmit.
Among alternatives listed in the EIS for the Nelson backwater mine was doing nothing, which would mean Holcim needing to find a new supplier for aggregate materials that the mine would provide. The sand and gravel deposited by river currents at both the current and proposed mine sites is used in everything from home to road construction, with 70 percent of metro area resources built over and inaccessible.
Also listed in alternatives to the proposed Nelson Backwater Mine was a mine at Baldwin Lake, the Baldwin Lake site expanding from the present site and located within Cottage Grove city limits. Last for alternatives was a new mine facility at Coates, located to the south in Dakota County.
As for the Coates alternative, the site would impact 720 acres in all, requiring 600 acres to mine the same amount as the Nelson mine. The Coates alternatives would also require new mining infrastructure and was affected by the presence of lands marked for agricultural preservation, comprising 32 percent of the site.
As for the Baldwin Lake alternative, it would share many details of the Nelson backwater site, being located to the southwest of the present mine site and within Cottage Grove city limits. The site would impact 231.9 acres in all, including the mine (220 acres) and supporting areas, and would use the existing barge system for most transport to market. Use of barges as opposed to trucks was held to require fewer trips and mean greenhouse gas emissions.
As for the proposed Nelson Backwater site itself, the mine if approved would utilize existing mine infrastructure to carve a pit 200 feet deep as the company mines sand and gravel alluvium deposited above the bedrock, said bedrock belonging to the Tunnel City group. One site plan for the proposed Nelson backwater mine (alternative B) would impact 265.4 acres, while another (alternative E) would be smaller in scope and impact 235.9 total acres, starting further east than alternative B. A floating dredge unit would be used to mine, with a conveyor network constructed prior to mining to connect with the existing mine. The materials would be transported from the backwaters to processing any conveyor, with the already existing barge system used in transporting the resulting aggregate to market.
Following active mining at the site, site reclamation at the Nelson Backwater site would reduce the pit depth to 100 feet, the backwater mine proposed to run for 20 to 25 years from early March to November each year, exact mine life affected by market factors. Mining in both alternatives would begin on the western portion and progress eastward.
As for plant and animal impacts, several species stand to be impacted or potentially impacted by the proposed project.
"Birds, butterflies, bats is what we're thinking about here," Schmit said in laying out the land animal impacts. The process started by querying state and federal databases to learn what species were potentially within one mile of the project area. Among animal species potentially within the proposed project area are Northern Long Eared Bats, Rusty Patch Bumble Bees, Bald Eagles, Loggerhead Shrikes, and the Henslow's Sparrow.
Schmit said the company had done surveys on bees in 2021.
"No bees were found, but suitable habitat was found," he said.
As for birds, the company had done surveys in 1997 and 2009 in the backwaters area to document migratory species’ use of the area, with 40 species found.
"Basically the birds are using it as a stopover site,” Schmit said. “They're not using it as a nesting or feeding area.”
The area is located within the larger Mississippi Flyway.
Impact to Northern Long Eared Bats could be avoided by controlling when trees were removed, Schmit said, while impact to Rusty Patch Bumble Bees could be mitigated by doing surveys before disturbing areas and planting flowering species after site disruption, to support bee life. Bald eagle impact could be mitigated by conducting surveys for nests prior to disturbing new areas, while impact to sparrows and other birds could be avoided by not disturbing habitat during breeding season.
"These are things we're currently doing at different locations," Schmit said of mitigation efforts for land animals.
As for aquatic life present, Schmit also spent time talking about company efforts to mitigate impact.
"What we're worried about here is mussels, fish, and aquatic plants," he said.
The company completed a level 1 survey in 2021 in conjunction with both the US Fish and Wildlife Service and state DNR. The level 1 survey involved divers surveying half-acre sections for 20 minutes and then using this to create a map. The survey catalogued a total of 5,900 mussels within 22 species, a level 2 survey finding 489 within species. Included in the surveyed mussel species were Higgin's Eye, Pistolgrip, and Wartyback, among others. The Higgin’s Eye is listed as endangered under the Endangered Species Act.
"Permitting when we go to mine this area will take permits for relocation," Schmit said. "We know where to find the relocation experts. They did this work for us and they did a very good job."
Mussel relocation would involve moving them in small batches as the company moved through the site to mine it, Schmit said.
"We would take these mussels and move them into newly mitigated areas," he said of possible mitigation strategies.
As for fish, the company completed a survey in 2023 and 2024 using both fiche and gill nets, along with electrofishing. The 2023 survey found 580 fish in 31 species, the 2024 survey finding 3,668 fish in 44 species. No federal or state endangered fish species were found, with Schmit saying permitting would be required for mitigating loss of habitat at the mine site.
As for plants, the company generated a 35-page report from an eight-day survey with staff who were DNR approved. The survey found no federally endangered species, with Minnesota listed species including water hyssop and hooded arrowhead. Schmit said a "take" permit would be required from the DNR for the state listed species.
Also completed in site evaluation for the proposed Nelson backwater mine meanwhile was an archaeological survey, the site being located just south of the Schilling Archaeological District. Several tribes were contacted in preparation of a prior 2010 EIS, with some tribes seeking engagement and others declining. The Schilling Archaeological District pertains to the Woodland era of indigenous settlement in Minnesota, with pottery and mounds both on site.
As for surveying the proposed backwater mine site just south, Schmit said no historic artifacts had been recovered from the backwaters area, though 11 archaeological sites located within a one-mile radius. Schmit said the company had done shovel tests in 2008 as well as a backwater survey in 2010, which involved dredge holes and a detailed square survey.
"We've had a lot of meetings, a lot of communication, and we intend to continue to communicate," Schmit said of the archaeological assessment process. "This is a process that can't be done in a vacuum. We've tried our best to communicate and let people know what we're doing."
Closing out his presentation by addressing potential pollution factors from the mine, Schmit said that both PFOS and PFBA had been identified at the site, not as a result of mining but part of broader PFAS contamination in South Washington County.
The proposed Nelson site is located along the Cottage Grove Fault, which runs southwest to northeast across Lower Grey Cloud Island towards East Cottage Grove. Schmit said the mine site is part of a discharge area in terms of the water table, meaning that water flows outward towards the Mississippi River.
"Our experts out there can tell you the difference between those," Schmit said of the Nelson site's PFAs contamination by PFOS and PFBA. "Both were below the residential, recreational FRB's out there. So they exist but they're at very low concentrations.”
Holcim US Marketing & Communications VP Jocelyn Gerst shared more on the proposed Nelson mining project after the Dec. 19 presentation at the HERO Center.
“The proposed project is an expansion of the existing Nelson Sand and Gravel operation where we have extracted for the Twin Cities economic development, including residential, commercial and critical infrastructure needs,” Gerst said. "Holcim has been operating the twin clamshell dredge mining to depths of up to 200 feet since the early 1990s. The proposed process extracts unconsolidated sand and gravel reserves above bedrock and doesn’t involve drilling blasting or mining of bedrock. Any excess sand is used for site reclamation activities. The EIS contains all required analyses. Should you need additional geological information, you can also reach out to the Minnesota Geologic Survey.”
Those seeking information on the Nelson Backwater Mine site may access it via the city website using Google search, as well as via the following tab link sequence: Home, Your Government, Departments, Community Development, Planning Division, Current Projects, Nelson Backwaters Project EIS. Computer access can be obtained at the Park Grove Library, if needed.
Now open through Jan. 17, comment on the Nelson Backwater Mine EIS can be made via email to eis@cottagegrovemn.gov, or by mail to:
Ms. Emily Schmitz, Community Development Director
12800 Ravine Parkway South
Cottage Grove MN 55016
Request for comment from the Indian Affairs Council on the proposed Nelson backwater mine was not returned by press time.