The Planning Board voted unanimously Tuesday night to approve the master plan to redevelop 10 acres on Portland’s eastern waterfront, amid organized opposition from local residents.

The board’s job was to ensure that the general development plan conforms with the city’s comprehensive plan and zoning rules.

“I do find this project is in conformance,” said Chairwoman Elizabeth Boepple before the vote. “There is no ambiguity in my mind.”

The developer will have to seek site plan approval for each phase of the project, which is expected to be built over the next decade, probably beginning with a new marina.

James Brady, a principal with the CPB2 development team, expects it will take two to three phases to complete.

“We really see this as an amazing opportunity for the city of Portland to create a new neighborhood and create new housing and create new jobs,” Brady said.

Opponents of the ambitious plan to convert the tract of industrial land into a six-block urban neighborhood outnumbered supporters 2-to-1 Tuesday night during a public hearing that lasted more than an hour. CPB2 is proposing to build the project at 58 Fore St. It would include retail, housing, restaurants, offices and the marina.

Portlanders for Responsible Development opposed the proposal, arguing that it does not comply with the city’s Eastern Waterfront Master Plan, which was adopted in 2004. The city staff and a city attorney disagreed with that assessment.

Portlandlers for Responsible Development is a nonprofit group that was registered with the state Dec. 1 by Barbara Vestal, an attorney and former Planning Board member. Vestal was a leader of Save the Soul of Portland, which in 2015 led an unsuccessful campaign to cap building heights at the site. Both groups share a Portland-based post office box.

CONFLICT OVER BUILDING HEIGHTS

Much of Tuesday’s testimony focused on how building heights should be measured.

Opponents believe the heights should be measured from the flood plain, while the city staff, the City Council and developers maintain they should be measured from the average grade. That distinction would mean the difference between four-story buildings and nine-story buildings on the easternmost portions of the site.

CPB2 is planning to build a single parking structure underneath three development blocks in that area. Once the grade is averaged over the 130,000-square-foot structure, the base height is 50 feet above sea level because of the steep slope of the land. That allows the developer to build eight- to 10-story buildings, instead of four-story buildings.

Portlanders for Responsible Development, which says it has 70 supporters, was given 15 minutes to make its case. The group’s members contended that the proposal does not conform to the city’s master plan for that area, and they showed their own renderings of what compliant buildings would look like if heights were measured from the flood plain.

Vestal called developers’ method of calculating heights “a trick,” and her husband, Ned Chester, called it “fiction.”

“I’m stunned we’re even considering these 9- to 10-story buildings,” Chester said. “This is a complete fiction. We shouldn’t even be talking about this. This doesn’t pass the straight-face test.”

One opponent, Paula Agopian, held up a sign that read “litigation.”

About 18 people opposed the plan and nine people supported it over the course of the 75-minute public hearing.

Opponents claim the City Council specifically capped building heights below Fore Street in 2004, but James Cohen, who served on the council at the time, said that was not the case.

“I remember clearly that Portland Co. was taken off the table,” Cohen said. The issue of heights “was focused on those buildings closest to Franklin Street, not the Portland Co. complex.”

Susan Morris, a resident and local developer who moved to Portland from Washington, D.C., said she trusts city planners to ensure the development respects the waterfront and surrounding community.

“Portland is on the cusp of becoming a great world-class city,” Morris said. “We’re at a point where momentum is building. We need to move forward.”

CPB2’s development plan calls for 638 units of rental and resident-owned housing, 132 hotel rooms, nearly 60,000 square feet of retail space, a new marina and nearly 124,000 square feet of office space.

THE MEETING’S CONTENTIOUS START

The meeting got off to a contentious start, with Planning Board member Lisa Whited recusing herself, citing a “perceived conflict” of interest without saying what it was.

“It is not a legal conflict of interest,” Whited said. “The perceived conflict is enough for me to recuse myself.”

Vestal asked board member Kristien Nichols, who missed several workshops, to explain how he has studied the issue to give an informed opinion.

A city attorney, however, told the board that such a declaration is not needed, since Nichols hadn’t missed any formal meetings, only informal workshops. Nichols later said he had reviewed all of the relevant materials.

Senior Planner Christine Grimando said in a memo to the board that the master plan for the project is consistent with the zoning and the comprehensive plan.

The City Council voted in July 2015 to rezone the land in accordance with the Eastern Waterfront Master Plan, which allows for buildings in some areas to be up to 65 feet tall. The council voted that those heights should be measured by averaging the steeply sloped land, allowing for tall buildings.

After that vote, a citywide referendum to limit building heights was defeated by nearly 4,800 votes, 63 percent to 37 percent.

CPB2’s development plan calls for 638 units of rental and resident-owned housing, 132 hotel rooms, nearly 60,000 square feet of retail space, a new marina and nearly 124,000 square feet of office space. A total of 736 parking spaces are proposed for the site, mostly on the ground floors of the buildings.

At least 10 percent of the housing units would have to be made affordable to middle-income residents. However, CPB2 could buy its way out of that requirement for $100,000 per unit. As much as $6 million could be infused into the city’s housing trust fund, which provides incentives for affordable housing developments.

The Narrow Gauge rail line and the Eastern Promenade Trail would remain on the land, although they may be moved closer to the water, pending state approval.

The site also includes 13 acres of submerged lands that would be made into a new marina for 220 boats.

Last week, Portland’s Historic Preservation Board recommended the elimination of nine to 12 townhouse units originally planned on Fore Street to preserve public views of the former railroad foundry.

CPB2, which includes Casey Prentice and Kevin Costello, bought the 10-acre site for $14.1 million in 2013 from Phineas Sprague Jr.

CORRECTION: This story was updated at 8:28 a.m. to correct the spelling of Kristien Nichols’ name.