After giving up on plans to build an indoor salmon farm on the Eastern Shore, a Norwegian company shifted its sights to the banks of the Susquehanna River in Northern Maryland, saying the new location is better equipped to withstand environmental impacts.

The Susquehanna is the Chesapeake Bay’s largest tributary, and Oslo-based AquaCon said the wastewater it plans to emit from its plant wouldn’t have a signficant impact due to the big river’s volume. Also, the Susquehanna isn’t a spawning site for Atlantic sturgeon like the little Eastern Shore creek, where AquaCon abandoned its original effort in 2023.

Environmentalists aren’t convinced.

In a court filing this week, the Chesapeake Bay Foundation argued the environmental permit for AquaCon’s plant on the Susquehanna isn’t sufficient to protect the river’s water quality, its underwater grasses or nearby habitat for numerous fish species, including blueback herring, alewife and American and hickory shad.

The environmental nonprofit, alongside two watermen, challenged the permit in Cecil County Court, asking a judge to review its terms for the plant’s discharges.

“The Susquehanna River is already overloaded with nitrogen and sediment pollution that runs off of farms and suburban developments,” said Gussie Maguire, a staff scientist for the Chesapeake Bay Foundation. “While we have made tremendous progress reducing that pollution, development pressure continues to strain the health of our waterways. MDE [Maryland Department of the Environment] must adequately consider this risk for new, experimental projects like AquaCon.”

Aquacon plans to build its plant on 160 acres of a former naval training ground in Port Deposit, downstream from the Conowingo Dam and about five miles upstream from the Susquehanna Flats, the largest bed of seagrasses in the Chesapeake Bay and an important habitat for marine life.

Once at full capacity, AquaCon aims to produce 20,000 metric tons of salmon a year, according to regulatory filings with MDE.

The permit, issued March 15 by MDE, would allow the Norwegian company to discharge up to 1.9 million gallons of “purge water” into the Susquehanna each day, a similar volume to levels it was seeking at the smaller Marshyhope Creek on the Eastern Shore.

MDE spokesperson Jay Apperson said the agency is reviewing the Bay Foundation’s petition.

“We respect the legal process, and we remain committed to applying environmental laws and regulations fairly and transparently,” Apperson said.

AquaCon executives did not respond to a request for comment on the court challenge. The company’s Maryland attorney, Ryan Showalter, also did not respond.

A cold-water fish, salmon haven’t swum in the Chesapeake Bay in many years, and traditional salmon farming — conducted in open-water pens — can come with a host of environmental consequences. AquaCon is among a group of companies pitching indoor farming as a more sustainable solution.

The process involves drawing water from the river and cooling it to be cycled through indoor ponds holding the growing salmon. To refresh the water, it would discharge some water — with fish waste removed — each day at temperatures much lower than normal for the Chesapeake Bay watershed.

But in its statement the Bay Foundation cast skepticism on the buzz around land-based salmon farms, pointing to problems with similar efforts in other places. Indoor farms in Florida and Canada have seen mass die-offs of the salmon, and a fire at a Denmark plant caused a toxic fluid to leak from the facility.

AquaCon’s cyclic process would create methane gas used to power the plant, while a solid waste byproduct would be exported off-site for use as a fertilizer on farms, according to regulatory filings.

AquaCon’s method requires salmon to be kept for several days in “purge” tanks. The purging process separates the salmon from their waste and rids them of a substance called geosmin, a naturally occurring compound that develops in these indoor farms that can leave the fish with an earthy taste.

The impacts of geosmin on the flavor of downstream fish was among the concerns that prompted backlash to AquaCon’s effort on the Eastern Shore.

The Susquehanna provides half of the Chesapeake Bay’s fresh water, and the Bay Foundation raised concerns that purge water could come with sediment, along with nitrogen and phosphorous pollution. Those two nutrients are the main drivers of the Chesapeake Bay’s ailing health.

The MDE permit requires AquaCon to use ultraviolet light to sterilize bacteria in the purge water and run the water through a filter to remove remaining solids before releasing it into the Susquehanna through a pipeline. Regulators also would require AquaCon to offset its phosphorous and nitrogen pollution into the Susquehanna and monitor levels of geosmin in the river and local fish tissue.

In a response to comments on its permit decision, environmental regulators said sediment in the purge water leaving AquaCon’s plant would be lower than amounts in the water coming in.