Development of mixed-use or multifamily projects can take years and many compromises to overcome local residents’ worries about increased traffic and housing density, several executives said in presentations Wednesday to a regional planning group.

Representatives from Uniondale-based RXR Realty, Virginia-based AvalonBay Communities Inc. and The Engel Burman Group in Garden City told members of the Long Island Regional Planning Council that some large, mixed-use developments melding retail, housing and recreational uses are crucial to Long Island’s future. Multifamily projects, particularly those built near train stations, are just as important, they said.

Those kinds of developments are ways to meet the needs of seniors who are downsizing and young adults looking for more affordable rentals, as well as to create “vibrant” destination communities that attract workers and retain young people, the developers said.

Frank Haftel, director of the Garvies Point project for RXR Realty, noted the two-decade timeline for the nearly $1 billion waterfront redevelopment project on 56 acres in Glen Cove.

RXR came on board the project, which officials call a public-private partnership, in 2008. It involves 1,110 residential units — about half condos and half rental units, including 111 affordable “workforce housing” — a waterfront esplanade, boardwalks, a park, preserve, an amphitheater, a restaurant, offices and other amenities.

It’s “an effort to create a diverse, multicultural, vibrant community,” Haftel said.

advertisement | advertise on newsday

Compromises along the way have included a reduction in the number of stories of the residential buildings, he noted.

After getting the planning board’s approval in October, there’s been “some dissent at the eleventh hour,” Haftel said, referring to a lawsuitfiled by opponents in November.

Christopher Capece, AvalonBay’s senior development director, listed common concerns that often greet multifamily housing development projects. He cited quotes from recent news items about concerns regarding a “transient population,” traffic congestion and housing density.

“But we know what the need is” for rental housing on the Island, Capece said. “It’s well-documented.”

“Why is the situation more acute? This is the reason,” Capece said, highlighting statistics showing the millennial generation of young adults has superseded baby boomers on the Island. “They’re coming of housing age. They can’t live with Mom and Dad forever.”

Members of that group, Capece said, are “going to leave in greater volumes” if they can’t find affordable places to live.

AvalonBay has 3,200 housing units in 12 communities on the Island, Capece said, highlighting its developments in Rockville Centre, Great Neck and Huntington Station.

He rejected what he said was a big concern of opponents: that multifamily housing leads to large increases in the school-age population, potentially overwhelming local school districts.

“If anybody’s telling you there’s one school-age child for every unit, they don’t know what they’re talking about,” Capece said. He cited AvalonBay statistics showing that in several of its complexes with 200- to 300-plus units, school-aged children numbered only 20 to 40, and in some cases far fewer.

He predicted greater acceptance as more people experience these developments. “I do believe that success breeds success at the end of the day.”

advertisement | advertise on newsday

The developers, as well as council members, noted the school districts that are closing or considering closing schools amid enrollment declines.

That has led to opportunities for Engel Burman, said Scott Burman, a partner in the firm, which owns and operates several Bristal assisted-living developments and has built several commercial and residential projects. He said Engel Burman has bought school buildings for redevelopment projects, calling that a “real phenomenon.”

Burman said while Engel Burman is looking to expand its assisted-living developments across Long Island and beyond — there are 12 currently on the Island — it’s also looking to focus on “transit-oriented development.” Burman said many Long Islanders “are looking for easy access to rail.”

Burman said his firm is seeking opportunities to build housing for “people who can’t afford a home on Long Island — yet. But they want to be here.”