SPRINGFIELD — Developer Peter A Picknelly, along with Springfield city officials, on Thursday unveiled a proposal to build a new Hampden County courthouse on a 14.5-acre site along the Connecticut River north of the Memorial Bridge. The proposal, which also includes housing and a marina, comes with a pricetag of $475 million.

The plans, unveiled at a press conference, call for a four-story, 210,000-260,000-square-foot courthouse; an 11-story residential apartment building with 120-180 units; and a 50-slip marina on the waterfront and a space for an outdoor restaurant.

The proposal hinges on whether the state decides to replace the troubled Roderick L. Ireland Courthouse on State Street. The state is exploring potential new sites and the cost of building a new courthouse; the existing facility has been plagued by health concerns.

Springfield Mayor Domenic Sarno said that if the state decides to build a new courthouse, the proposed riverfront site would be the ideal location.

Sarno, Picknelly, and Tim Sheehan, Springfield’s chief development officer, all said that a development of this size and with its various components could be a catalyst for growth along the river and in the North End of the city, similar to what the Basketball Hall of Fame has done for the area south of the Memorial Bridge.