The state is on the verge of taking control of the 88 acres in South Buffalo where it plans to build the RiverBend clean-energy and technology hub.

Buffalo Urban Development Corp. on Tuesday approved an agreement to sell the city-owned property, located on the former Republic Steel site, to the state, clearing a key hurdle in the development of one of the Cuomo administration's major projects under the Buffalo Billion economic-development initiative.

The $2.5 million sale is expected to close within a couple of weeks, BUDC and state officials said. Once that happens, officials expect a flurry of preparation to begin on the property, from utility and road work to final site cleanup, and, within a matter of weeks, groundbreaking for the first building in the complex.

"This is going to be a great, great development for the city and the region," Mayor Byron W. Brown said.

"It's happening. It shows that the phenomenal development we're seeing in the City of Buffalo is real."

"The project is moving at an excellent pace," Brown said. "I think it's going to be accelerated. The state really wants to move on this."

Under the deal, the state, through its Fort Schuyler Management Corp., is acquiring the 88.25-acre site for $28,300 per acre, or about 42 percent more than the property's value, under a December 2013 appraisal.

A pair of California-based companies - solar panel manufacturer Silevo and LED lighting-maker Soraa - have agreed to become the first two tenants in the complex, which is being based on the same economic-development model that the state used to build a thriving semiconductor industry in the Albany area.

Under that model, the state plans to invest $225 million in the RiverBend complex, which ultimately is envisioned to have at least six buildings.

The state money will be used to acquire the site, install the infrastructure - such as water, sewer, utility and roads - and construct the buildings at RiverBend. The state also will buy and own the equipment that is within the complex and used by the companies, which will not get direct state funding.

The first phase of the project will involve construction of a 275,000-square-foot building that will be shared by Silevo and Soraa, with the solar panel manufacturer occupying more than 80 percent of the space. A public event to show off the plans for RiverBend is expected to be held in the coming weeks, Brown said.

As part of the development, the state expects to spend nearly $60 million on infrastructure and site improvements, with almost half - $28.5 million - going toward the installation of utilities at the site.

Other preconstruction efforts will range from $6.7 million in site remediation work at the brownfield site to $9.2 million on site preparation. An additional $10.5 million is expected to go toward construction of roads, parking, drainage and site lighting. Landscaping, pedestrian trails and other final-stage site work is expected to cost $5 million, BUDC officials said.

Silevo is hoping to move into the building by March 2015, while the Soraa portion of the Buffalo River facility is being targeted for completion in June 2015, said BUDC President Peter M. Cammarata.

Because the first building on the site will be owned by a state entity, it will not be subject to property taxes. But the sale agreement stipulates that the second building and any others built afterward will be subject to 10-year payment-in-lieu-of-taxes agreements, or PILOTs, similar to those used by the Erie County Industrial Development Agency for regionally significant projects.

"We've been waiting for this for a long time," said BUDC Vice Chairman Dennis M. Penman. "People have been out there talking about silver bullets in the past. This is a real deal."