The fate of one of Maryland’s healthiest waterways may be decided this summer, as the elected leaders of one of the state’s fastest growing counties weigh a new long-term growth plan.

After five years of debate, the Charles County Board of Commissioners is set to take votes in July on a blueprint for future development in a land that’s changing from agrarian to bedroom community for Washington, DC. Sharp divisions remain over how the plan’s provisions might affect Mattawoman Creek, a high-quality tributary of the Potomac River in the crosshairs of that transformation, which not long ago was described as “what a restored Chesapeake Bay would look like.”

At a 2.5-hour public hearing in May, the five commissioners heard conflicting claims about the county’s proposed comprehensive plan — that it would either save or doom the creek from a juggernaut of development set in motion by the last growth plan local officials adopted a decade ago.

“Urgent, bold action is necessary,” said Alex Winter, a resident of Bryans Road, a once-rural area in the creek watershed that has been targeted for growth.

Charles was Maryland’s fastest growing county from 2000 to 2010, adding 26,000 new residents to reach a total of nearly 147,000. The rate of growth has eased some in recent years, but remains the third highest in the state. County planners project another 75,000 residents by 2040, a 51 percent increase. Over the same period, the number of housing units is expected to grow by 59 percent.

The proposed plan, approved on a split vote earlier this year by the county’s planning commission, would focus much of the new growth around already developed areas such as Waldorf, an unincorporated “city” that’s home to nearly half of the population. The debate swirls around the future laid out for rural areas, especially natural gems like Mattawoman Creek.

By many measures, the creek is still one of Maryland’s best streams, teeming with largemouth bass and thronged in springtime by spawning runs of migratory fish. It also harbors a diverse array of frogs, salamanders and turtles, a globally rare magnolia bog and more than two dozen species of rare plants and animals, according to biological assessments. It’s become a hotspot for bass tournaments, as well as a draw for ecotourism.

But state and federal natural resource agencies warned nearly five years ago that the creek was at a “tipping point” of irreversible ecological decline because of the human footprint spreading across its 63,000-acre watershed, the bulk of which is in Charles, with a portion in Prince George’s County.

An interagency task force report, prepared by the Department of Natural Resources, said that pavement and buildings were close to covering 10 percent of the watershed, which studies have shown is the point at which biodiversity and fisheries begin to decline beyond hope of recovery. The extent of impervious surface could double to 20 percent, they warned, under then-current development policies.

That warning came as controversy roiled the county over a decision by the planning commission to back a “balanced growth” blueprint put forward by a group of developers and landowners, which overturned recommendations from a series of public meetings to scale back development.

Some county commissioners at the time took umbrage at what they saw as state interference. But the five-member board ultimately rejected the planning commission’s recommendations and sent them back to the drawing board. In the meantime, county voters replaced two of the commissioners in the 2014 election, with the newcomers seen as supporting more limited growth.

Steven Ball, the county’s planning director, said the new plan calls for changes in development regulations and zoning designations intended to protect Mattowaman. The biggest change, he said, would remove the designation of an 18,000-acre chunk of the creek’s watershed as a “deferred development district,” set aside for future growth. It would instead be declared a “watershed conservation district.”

The plan drew praise from Anthony Redman, a planner and policy review chief for the Maryland Department of Natural Resources, who had helped write the state’s Mattawoman warning report.

“Today, after having reviewed the draft plan,” Redman said, “I am hard pressed to find even a single one of the recommendations we made that have not been addressed in some way in this draft plan.” Most important, he said, was the redesignation of the creek watershed, calling it “the first truly low-density zoning measure ever taken by the county.”

But representatives of environmental and community groups contended that little had changed in the plan beyond giving the watershed district a greener sounding name. They pointed out that the zoning in the renamed “watershed conservation district,” permitted one home per 10 acres, the same figures when it was called a “deferred development district.”

Though not mentioned by Redman at the hearing, the state-federal task force had proposed cutting housing density in half in the watershed, to one home per 20 acres. In an interview later, Redman acknowledged that recommendation had been rejected, but cited stormwater retrofits, stream valley protections and other proposed changes. Overall, he said, “they’re moving in the right direction.”

Critics questioned that. “It is time to rein in unchecked growth,” said Jim Long, president of the Mattawoman Watershed Society, who noted that state biologists have already documented declines in spawning and fish populations in the creek. He called on the commissioners to “fix the comprehensive plan,” a refrain heard repeatedly from other speakers throughout the hearing.

Representatives of the county’s business and real estate communities said the county needs “balanced growth,” and its congested rural roads must be upgraded to reduce traffic jams and long commutes.

“We want to see development stay where it’s been planned to stay,” Steve Paul, president of the Southern Maryland Association of Realtors, said in an interview after the hearing. “We don’t want to see any damage to Mattawoman Creek, any part of it. But we do want to see businesses come to our county, and we would like to see them welcomed here. That’s going to take more development in some areas that are being protested.”

The county commissioners have scheduled a series of work sessions in June to review the plan. Another public hearing is set June 21 in La Plata to take comments on any changes commissioners have proposed to the growth blueprint. The board then intends to vote on the proposed changes June 28. A final adoption work session is tentatively set for July 12.

Ken Robinson, a second-term commissioner who had been a dissenting voice on growth before 2014, said he hopes to revise the plan. And he noted that the board now has that authority, thanks to state legislation passed last year.

“I think it’s an improvement over where it was a couple of years ago,” he said of the proposed growth blueprint, “but in my opinion it still doesn’t do enough for preservation and conservation. I think that we can fix that. Mattawoman Creek is a critical stream in Charles County that relates to the whole ecosystem of the Potomac river and Chesapeake Bay. So we only get one chance to save the Mattawoman, and I think we’re going to do that.”