Proponents of closing GenOn Energy’s Potomac River Generating Station lauded the news Tuesday that the plant is to be shuttered by late 2012.

“This was a long fought but well won victory for the citizens of Alexandria and the nation's capital,” U.S. Rep. Jim Moran (D-8th) said in a statement. “What once was the largest stationary source of air pollution will be no more. Through citizen involvement and committed city officials, the Potomac River Generating Station and its 1949 coal-fired boilers will finally be shuttered.”

Del. David Englin (D-45th), who represents parts of Alexandria as well as parts of Fairfax and Arlington Counties, called the agreement a “major victory for the people of Alexandria,” but asked citizens to focus their efforts on ensuring GenOn hits the Oct. 1, 2012 closure date for the plant.

"Our community owes a great deal to the citizen activists who have worked with such unfailing dedication and perseverance to get us to this point,” Englin said in a statement. “While there is reason to celebrate, the agreement does allow some wiggle room on the closing date, which means we must continue to be vigilant until the day the plant finally and permanently closes its doors."

D.C. Mayor Vincent Gray (D), who expressed concerns about the plant’s harmful emissions earlier this summer, called the announcement “great news.”

“I am relieved by GenOn’s decision to close the Potomac River Generating Station in Alexandria, Va.,” Gray said in a statement. “Doing this will relieve the District of the burden of this pollution that is adversely affecting the health and well-being of our residents, particularly those in Ward 8.  Additionally, as a nation, we must begin to aggressively deploy technologies that will relieve us of our addiction to coal-fired power plants that can detrimentally impact public health and the environment. This is a step in the right direction.”

The Sierra Club, Greenpeace, Chesapeake Climate Action Network and other organizations participating in the “GenOff” campaign to close the plant staged a press conference Tuesday afternoon next to the facility.

Every representative said the announcement to close the generating station was the culmination of 10 years of work starting at the grassroots level.

“We look forward to a day when this corporate entity, GenOn, shuts down more of these plants,” said Robert Gardner of Greenpeace.

Keith Thirion, lead Virginia organizer with CCAN, said the plant is one of the largest sources of planet-warming carbon emissions in the Washington, D.C. area. The retirement of the plant, he said, is a necessary step in preventing the impacts of climate change on the region.

Greg Staple, CEO of the American Clean Skies Foundation, called it “a historic day for Alexandria and the Washington region,” adding that the ill-effects associated with plant emissions have increased healthcare costs for nearby residents. 

ACSF unveiled a plan three weeks ago to close the plant and redevelop the land with mixed-use buildings.

In a statement released earlier Tuesday, Staple said, "We look forward to working with the city to open up the riverfront to the public and make this site a clean energy showcase and job creator.  

“Once GenOn did the math, it looks like the company came to the same economic conclusion we did: This site is simply more valuable for other uses." 

Alexandria City Councilman Paul Smedberg, who attended the press conference, said there are concerns about the 25-acre plot because of the hazardous materials it has housed for 62 years.

However, he did say the area had the potential to be a “gateway to the city” considering its location along near Alexandria’s northern border and along the Potomac River.

“This really has a chance to redefine North Old Town,” he said.

Alexandria Mayor Bill Euille said Tuesday morning that the announcement to close the generating station would not alter current discussions about redeveloping Old Town’s waterfront.

“I think the Council and the community is committed to moving forward with the waterfront process,” Euille said.

Boyd Walker, chair of the Greater Alexandria Preservation Alliance, released a personal statement Tuesday afternoon urging to suspend consideration of the current waterfront plan and that a new plan be drafted with consideration to the GenOn site.

“I hope that the Chamber of Commerce, The Alexandria Convention and Visitors Association, Old Town Civic Association, The North Old Town Civic Association and others to join me in asking that the city set aside the proposed plan so that we can come up with a new plan acceptable to citizens, that includes the GenOn site, as well as looks at the impact of development on all of Alexandria, not just a small area,” he wrote.

Walker is also co-chair of Citizens for an Alternative Alexandria Waterfront Plan, a group that opposes the commercial development in the city’s designs for the waterfront.

• Patch editors Shaun Courtney and Sharon McLoone contributed to this report.