The Suisun Marsh — known as the largest swath of contiguous wetlands on the West Coast and a haven for thousands of migrating waterfowl — has become the Bay Area’s latest battleground between fossil fuel producers and environmentalists hellbent on fighting climate change.

A Brentwood company, Sunset Exploration Inc., announced in January it wants to explore for natural gas by drilling a section of the 116,000-acre marshland about 9 miles southwest of Suisun City in an area known as Hunter’s Point, according to the U.S. Army Corps of Engineers.

Sunset proposes to construct a gravel drilling pad almost an acre large and drop a volleyball-sized drill bit about a half-mile into the sandstone ground, probing to see if there’s enough gas worth extracting. This first-phase process would last several weeks.

If the well yields enough natural gas, Sunset next plans to build a pipeline from the drilling pad to send the gas to an existing pipeline about a mile and a half away, There, the gas would be tapped to serve about 30,000 homes in the surrounding region for up to 10 years.

Because Sunset already has mineral rights to more than 4,400 acres in the Suisun Marsh, it can technically drill without a permit. But it won’t be able to if the Army Corps determines the well and pipeline would harm the environment.

A coalition of environmental groups, including San Francisco Baykeeper and Center for Biological Diversity, has already taken a stand against the project and wrote a Feb. 26 letter urging the Army Corps to reject Sunset’s request for a permit.

They contend the drilling operation would contribute to climate change because combusting natural gas to produce energy releases carbon emissions. Plus there’s the added risk of gas leaks.

In addition, opponents contend the project would threaten hundreds of bird, fish, mammal and reptilian species that thrive in the marsh, as well as sensitive plants such as the Suisun thistle that doesn’t grow anywhere else on Earth.

So swift and fierce was their response that Sunset is contemplating a retreat.

“It may not be worth the fight,” Bob Nunn, president of Sunset Exploration, said in a recent interview.

Joining the chorus against the project is the state Department of Justice’s Office of the Attorney General, which sent its own letter recently telling the Army Corps that it’s concerned drilling would disrupt natural habitats and produce more carbon emissions at a time when the state is attempting to tamp down its fossil fuel production.

“The proposed fill and drilling in areas of Suisun Marsh could harm unique and irreplaceable habitat for endangered California Ridgway’s rail and salt marsh harvest mouse, numerous migratory bird species, listed fish species, and the very rare Suisun thistle,” the attorney general’s office wrote.

Asked why a state law enforcement agency would weigh in on a drilling project, the office replied in an email, “We’ll let the letter speak for itself.”

Even if the Army Corps signs off on the drilling plans, Sunset Exploration would need to get the OK of other federal and state environmental regulatory agencies, such as the California Department of Fish and Wildlife and the California Regional Water Quality Control Board.

If approved, Sunset’s wouldn’t be the only natural gas well at Suisun Marsh. Several other active gas wells operate there, their locations shown on an online map created by the California Geological Energy Management Division. About a dozen other gas wells have been plugged and are no longer active for various reasons. Nunn said these wells are similar in size to what he proposes to build.

“We were surprised at the level of opposition,” Sahrye Cohen, a regulatory chief at the Army Corps who will review the permit application, said in an interview. “I think it’s an indication of the times. People don’t want fossil fuels in California.”

Sunset’s Nunn acknowledged his company is pondering whether the costs of an extended review process are justified given the stiff resistance.

“The environmental community likes to thrust longer and longer delays on the smaller projects, until eventually the project becomes unrealistic and the operator says, ‘To hell with it,’” Nunn said.

While natural gas is cleaner than oil, producing less greenhouse gas emissions when it combusts, it still is a fossil fuel — and California’s goal is to reduce its emissions by 40% before 2030, an ambitious plan that involves transitioning to fully renewable energy sources.

Nunn called critics of oil and gas drilling hypocritical for participating in a carbon-fueled society and argued that shipping oil to California from elsewhere emits more carbon than would his local drilling project.

San Francisco Baykeeper’s executive director described Nunn’s comments as “nonsense,” saying there’s no tolerance in the Bay Area for “dinosaur oil companies” amid a transition to cleaner energy sources.

“Any time there’s drilling in the vicinity of wetlands, you need to evaluate thoroughly the environmental impacts of that drilling,” Sejal Choksi-Chugh said in an interview. “The Bay is no place for oil and gas drilling — the fact that (the company) is reconsidering is a big step and we’re pleased to hear that.”

Jacob Klein, an organizer with the Sierra Club’s Redwood Chapter, described Nunn’s justification for drilling locally and extracting natural gas instead of oil as “common talking points” that ignore the bigger picture.

“Rather than make comparisons between petroleum-based energy sources, we just need to be leaving (natural gas) in the ground,” Klein said.

Project opponents also point to the immediate environmental damage that drilling can wreak. A pipeline operated by energy company Kinder Morgan burst in 2004, spilling more than 120,000 gallons of oil into the marsh and killing numerous species.

Sunset Exploration acquired an existing Solano County permit and 4,400 acres of mineral rights for Hunter’s Point in 2018 after previous holder Venoco went bankrupt as it was seeking to obtain a drilling permit from the Army Corps.

Sunset was hoping to finish the job, though the opposition is now giving it second thoughts.

“They’re singling me out,” Nunn said. “If this gets drawn out for months and years, the real loser will be the environment.”