As expected, the Williams Company has filed an application with the Federal Environmental Regulatory Commission (FERC) to build a 1.2-mile natural gas pipeline extension through the Princeton Ridge. A newsletter detailing the filing, which was entered with the agency on Monday, is being mailed by the Oklahoma-based company to property owners whose homes lie within the area that is part of the Leidy Southeast Expansion Project.

Residents have been vocal about their concerns regarding certain aspects of the proposed project, particularly its potential effects on the environment. Chris Stockton, a spokesman for the Williams company, said that the input from the homeowners was responsible for tweaks and changes to the original plan.

“A lot of people would look at this and say it’s the beginning of the process,” he said Tuesday. “But it’s actually the culmination of more than a year of planning, public meetings, and conversations with landowners. After meeting with the stakeholders in Princeton, we committed to doing the construction work within the existing tree line rather than a wider corridor, to try and avoid the tree loss that would have been associated with this project.”

The fact that Williams has filed with FERC does not mean that input from the public is no longer possible. “This is a significant milestone, but it doesn’t mean that the process is over,” Mr. Stockton said. “We can still make changes. It’s just more difficult at this point.”

Princeton Council will discuss whether to officially become an intervener in the process at its next meeting on October 14. That status provides access to legal submissions during the approval process, which allows the town to contest FERC’s final decision. Clinton Township, which has property on the proposed pipeline, has become an intervener, as has the New Jersey Sierra Club and the group New Jersey Environmental Action.

The review process usually takes between eight and 10 months, said Mr. Stockton. “There are various opportunities for the public to weigh in throughout the process. They’ll issue a draft environmental assessment, and the public can speak if there are any outstanding issues. And people can still submit comments to FERC.”

If approved by FERC, the construction of compressor stations for the project would begin in the fall of 2014, with pipeline construction following in the spring of 2015. The Leidy Southeast pipeline is part of a 10,200-mile system that provides natural gas transportation and storage services for markets throughout the northeastern and southeastern United States.

Since the Williams company’s plans were announced last February, citizens have met with representatives and walked the length of the Princeton Ridge with them to detail their concerns. “This pre-filing process, which we’ve been in for the past year, is designed to facilitate a dialogue between the pipeline operator and the communities,” said Mr. Stockton. “This particular project is a good example of the way the process is supposed to work because it gets the issues out early on.”

A copy of the filing is available on FERC’s website and at area libraries including the Princeton Public Library.

“We’re still listening to people,” Mr. Stockton said. “We can still make tweaks and changes.”