By Maria Saporta and Ellie Hensley

The developer of the former Doraville General Motors plant said Wednesday about $300 million in development is underway or poised to start over the next six months, as the massive transformation of the site cranks up.

The mixed-use development, which likely will total 10 million square feet over the next decade, is slated to rise on the site of the 165-acre GM plant, which has sat idle since it closed in 2008.

Speaking in an interview on Tuesday evening, Perry said the project will cost about $1.5 billion and take a decade to complete.

“That’s our projection, and to support that development, there would need to be about $180 million of public infrastructure that would need to be done,” said Perry, chairman and CEO of The Integral Group LLC, the developer behind Assembly. “That would be phased to support the private development as it’s being done.”

The project will move forward in the first quarter of 2017 after being put on hold in summer 2016, when DeKalb School Superintendent Stephen Green rejected a proposal to form a tax allocation district that would provide about $185 million in infrastructure funding.

Integral retooled its plan to include government grants and loans and created the Assembly Community Improvement District (CID), which could issue about $180 million in bonds in three phases to finance infrastructure improvements at the site.

“Most likely, [the infrastructure funding] would be done in three separate bond issues — about one-third each,” Perry said. “The first of those is estimated to close in the first quarter. That not withstanding, significant development has already happened with private investment and some assistance for the state.”

The CID will not cover the entire cost of infrastructure improvements, but Integral was able to get a tax abatement from the DeKalb County Development Authority to help bridge the gap.

These infrastructure improvements include covering Park Avenue from underneath the existing Norfolk Southern rail lines and MARTA transit lines to downtown Doraville and the MARTA station. The covered street is not expected to be part of the first phase of infrastructure improvements.

“We are going to do a lot of the infrastructure for a third of the site and fully design the entirety of the site for infrastructure,” Perry said. “The first part is heavily skewed to the area adjacent to Chamblee.”

Matt Samuelson, president of Integral-Guide Program Management, said the company has about a million square feet of prospective tenants linked up. In the interview with the ABC, Perry said this included corporate office users and “significant” retail developments.

“There’s considerable interest and negotiations ongoing with a number of prospects — predominantly corporate offices, financial services and retailers,” Perry said. “…We actually have super-heated demand to be on the site. We have been emphasizing development on the side that is closest to Chamblee.”

Assembly would include nearly 10 million square feet of office towers, apartments, stores and restaurants along MARTA’s Gold Line. It would create up to 8,000 office, retail and light manufacturing jobs. Third Rail Studios, a $10 million film and television studio with 60,000 square feet of stages, has already been completed on the site and is open for business.

“The studio is open and filming what we believe is the largest film for 2017,” Perry said. “The whole studio has been leased out.”

The project has the potential become a regional nexus for transportation along the Atlanta Perimeter, where MARTA and I-285 converge at Peachtree Industrial Boulevard.

Ellie Hensley covers the film industry for the Atlanta Business Chronicle.