Supporters of the group Save The Mozino Forest attended the council meeting, applauding speakers who called for keeping the wooded area - located between State and Township Line roads - unchanged.
"It's one of the last forests in Upper Darby Township," said Lee Jordan of Drexel Hill.
Rockwell Development Group, which owns the property, is seeking to rezone the tract from its current designation allowing 56 single-family homes to a mixed-use plan that includes townhomes, apartments, retail and a park.
Members of Save The Mozino Forest argued the proposal would harm the community.
"We feel that we are very densely populated right now. Building that many homes would be a public health and safety issue for our area," Jordan said. "You can't even get down State Road. Traffic is horrible. It would be an extreme strain on our public services."
Environmental concerns were also raised.
"This tract has over 2,000 trees, has a creek running through it. It's a soak-up place for stormwater," said Bonnie Hallam of Drexel Hill.
In a statement, Rockwell President Greg Lingo said, "We have been working tirelessly with the neighbors and broader community to create a new community for us all to be proud of, in an area that already has significant traffic issues."
He also said, "This mixed-use plan provides open space, significantly higher net income to the Township and School District, pedestrian connectivity and a much-needed variety of new housing types."
Hallam questioned that claim, saying, "I don't know that they worked with the neighbors."
Residents said they hope council members will reject the zoning ordinance.
Upper Darby Council Vice President Noah Fields said leaders are still evaluating the proposal.
"It's going to be built on, and so the question is not should we build or should we not build. It's private property.... I think we should build the future. It shouldn't just be something that happens to us, and we should build something that makes sense for the future of Upper Darby," Fields said.
Fields said no vote is currently scheduled.
Residents say they plan to continue meeting with local leaders as they work to preserve the Mozino Tract.