WASHINGTON, DC-By any measure, Property Group Partners' Capitol Crossing is an ambitious project. The proposed $1.3-billion development is designed to be 2.2 million square feet, 70,000 of which will be devoted to retail. It will be built, in part, on decking over Interstate 395, connecting Capitol Hill to the East End, and finally as PGP’s principal David Happ puts it, “fill in the void that 395 gashed through the city.”

Once the project gets off the ground it will represent a decades-long effort. So, what more could a project need to be labeled an envelope-pusher? How about a specially crafted LEED designation all its own?

That is how things are shaping up, as the Property Group and USGBC discuss the green features of the project, many of which are so cutting edge that USGBC has concluded none of its existing designations fit, Happ tells GlobeSt.com. At first, PGP thought the LEED neighborhood program would be suitable, but the unique deck the company expects to develop nixed that. “This is the first time anyone has done a project of this scale transforming an urban landscape,” he says.

Sean Cahill, vice president of development at PGP, tells GlobeSt.com that the platform will allow the buildings to plug into a novel ecosystem. “Buildings will have access to sustainable components that other buildings on terra firma wouldn’t have,” he states. “There will be water storage in enormous quantities, rainwater and underground water, that we will capture and treat and put back in the buildings.” The buildings will be able to function off of the grid and control their utility expenses to a far greater degree than many green buildings can now, he adds.

PGP has been working with USGBC to create a program for urban deck infill projects, Happ says. A few other cities have explored this concept but not with the environmental use case that PGP has in mind. “We are the first that is trying this via green development,” he says. A LEED urban deck infill program probably won’t be ready until the project is poised to break ground.

That day, however, is not that far off, as piece after complicated piece of this project falls into place. PGP has procured an equity investor, name unknown, willing to back the project. It has approvals from the D.C. Zoning Commission and from the Federal Highway Administration. It has selected the architects for two of the three office buildings and has just opened a marketing center to sell the project to prospective tenants. “We would like to have this project up and running in mid to late 2015,” Happ says.