Seattle Mayor Mike McGinn says the city has reached an agreement with a broadband developer to build out its fiber network for high-speed computing for homes, businesses and services.

Spokesman Aaron Pickus says the deal announced Thursday allows Gigabit Squared of Washington, D.C., to start raising money for engineering work.

Pickus says the project will make use of excess capacity on Seattle’s 500-mile network at no cost to the city.

The plan will begin with a demonstration project serving 50,000 homes and businesses in 12 neighborhoods. Plans also call for a wireless network for Internet services.

The University of Washington is also working on the project.