We invite you to comment on the draft wastewater permit for the 3M Chemical Operations facility in Cottage Grove.

The draft industrial wastewater permit for 3M’s facility in Cottage Grove that the MPCA previously put on public notice from July 1, 2024, through Aug. 30, 2024, has changed due to comments received during the public notice. The changes are noted in the draft permit and listed in the public notice document.

3M’s facility in Cottage Grove manufactures a diverse group of products including abrasives, organic chemicals, polymers, resins, ceramic solutions, fluorochemicals, tapes, films, coatings, and extrusions. Chemical production includes a variety of per- and polyfluoroalkyl substances (PFAS). The facility treats its own sanitary wastewater and stormwater as well as non-contact cooling water, wastewater that it creates from its production processes and pilot production lines, contaminated groundwater, leachate from SKB Environmental’s Rosemount landfill, water from LSP’s Cottage Grove power station, and water from activities related to decommissioning the site’s incinerator.

The facility discharges up to 15.2 million gallons of treated wastewater per day to an unnamed creek that flows into the Mississippi River.

The draft water quality permit protects water quality for aquatic life, recreation, and human fish consumption by limiting pollutant discharge as required by federal regulations and applicable water quality standards. It sets new or lower discharge limits (as compared to the 2003 permit) for:

·                    five PFAS compounds

·                    seven heavy metals

·                    55 semi-volatile or volatile organics

·                    aggregate toxicity to aquatic organisms

·                    ammonia

·                    phosphorus

The draft water quality permit also requires PFAS monitoring:

·                     in all treated wastewater

·                     at 21 stormwater discharge locations

·                     in seven internal waste streams

·                     at upstream and downstream surface waters

·                    in the tissue of fish caught in the Mississippi River near the facility and downstream of it

The draft permit also includes new routine monitoring for semi-volatile and volatile organics, metals, and salts.

The MPCA proposes to modify the maximum load of total suspended solids from the facility in the South Metro Mississippi River total suspended solids study. The maximum load of total suspended solids in the study, approved by the EPA in 2016, was 545 kilograms per day at a single monitoring station. The addition of a second monitoring station will bring that maximum load to 1,532 kilograms per day. The modification will not contribute to the total suspended solids impairment in the South Metro Mississippi River.

All comments submitted on the July 1, 2024, public noticed draft permit will receive responses prior to the final permit action. There is no need to resubmit a previously submitted comment. Any comments on the re-public noticed draft permit (Dec. 18, 2024) should be submitted according to the procedure for public participation found in the public notice.

Wastewater from industrial and commercial sources may contain pollutants at levels that could adversely affect the water quality in area wetlands, streams, rivers, and lakes. Water quality permits - or National Pollutant Discharge Elimination System (NPDES) permits - establish specific limits and requirements to protect Minnesota's surface and groundwater quality. All wastewater must be treated before it goes into surface water to protect human health and aquatic life. Permits are regularly reviewed and updated as they expire, allowing the MPCA to incorporate new information about the impacts of pollutants on the environment in future permits.