A proposal to build a large swine feedlot in Fillmore County is facing stiff opposition from some of its neighbors, who say the state’s environmental agency needs to do a more thorough assessment before issuing a permit.

Nearly 50 opponents descended on Minnesota Pollution Control Agency (MPCA) offices Tuesday, the last day for public comment on an environmental assessment for the proposed project. They issued a demand for a full-fledged Environment Impact Statement (EIS), something that is rarely done for such farm facilities.

Catalpa LLC is proposing a new 4,980-sow farrowing operation about 10 miles east of the town of Harmony, in the far southeastern corner of the state. It would produce an estimated 7.3 million gallons of liquid manure, which is proposed to be stored in reinforced concrete pits, removed each fall and injected into farm fields as fertilizer.

Neighbors, including some farmers, contend the environmental impact potential is “enormous” because it would sit on an environmentally sensitive area known as the karst region of the state. They worry about manure seeping into drinking water and odor wafting throughout the area.

An Environmental Assessment Worksheet was completed through the MPCA in April. Agency officials use such assessments to decide whether a project has potential for significant environmental impact and needs a more in-depth Environmental Impact Statement.

Based on the proposer’s permit application, though, the agency’s commissioner made a preliminary and tentative determination to issue the permit for a term of approximately three years.

Wearing yellow T-shirts and holding signs in front of the agency’s building, about 50 opponents chanted “Say yes to EIS!” Tuesday afternoon before delivering written comments to an assistant commissioner. The group later met privately with Gov. Mark Dayton.

The proposed project “puts our drinking water, health, property values and economy at risk,” said Dayna Burtness, a neighboring farmer who raises pastured pigs. “In fact, it jeopardizes the future of our rural community.”

Karst geology includes extremely porous bedrock that absorbs water quickly and creates sinkholes easily. That makes drinking water especially susceptible to contamination, especially after heavy rains.

“Water can travel down hundreds of feet in a matter of minutes,” said Aaron Bishop, a geology graduate whose family owns a nearby cave. “Anything that happens on the surface, we will eventually see farther down.”

Waukon Feed Ranch, a family-owned company in Iowa, has been hired to help build the facility and see it through the application process; the company would also manage the facility once is it built.

Daniel Dykstra, Waukon’s assistant general manager, said the application process has already been long and complicated. Started more than a year and a half ago, it included getting a geotechnical engineer to walk the site to confirm sinkholes and other karst features, as well as doing air quality modeling over several square miles.

“There are very few people that understand how intensive, how rigorous the state and even the county’s rules already are,” Dykstra said. “There are many, many things that go into that.”

A local farmer owns the land on which the facility would sit and would be the majority owner in the facility as well as its nearest neighbor, Dykstra said.

County and state officials say the project, which would house sows and baby pigs up to 22 days old, would become the largest on a single site in Fillmore County as measured by “animal units,” which take into account species and size to approximate impact of resources consumed and excrement produced.

The proposed facility would contain 1,992 animal units on a single site. The next largest feed lot — a dairy facility on a single site in the western part of the county — has 1,942 animal units. The next largest swine facility on a single site in the county has 1,110 animal units.

But another operation with two adjacent sites in Fillmore has 6,300 pigs of varying sizes, adding up to 1,365 animal units.

The proposed operation will not be the largest swine feedlot in the state by far, however. According to MPCA numbers, 280 swine sites have a higher head count than the Catalpa proposal. There are 54 swine facilities in the state with animal units over 1,992. One farrowing site in Freeborn County, for instance, has 11,238 swine that weigh more than 300 pounds each, equaling 4,495 animal units.

The group from Fillmore, most of whom traveled to St. Paul on a bus, said they are not anti-agriculture.

“I’m a huge advocate of not putting my nose in somebody else’s business,” said Mark Spande, a farmer who said he lives about a mile north of the proposed site — upwind but downhill. “But when your business potentially harms my quality of life or my neighbor’s quality of life, I think it’s very fair that we do put our nose in that business and make sure that it’s accounted for.”

Once a proposal gets to the stage that Catalpa’s is in, it’s unusual for the pollution control agency to require an EIS, said agency spokeswoman Cathy Rofshus.

“Usually everything is worked out that it’s going to meet the conditions for the permit,” Rofshus said. Additional conditions are sometimes added at this stage, though, she pointed out.

Pollution Control Agency Commissioner John Linc Stine is expected to decide in about six weeks whether an EIS is needed.