A multi-year project to replace a bridge that carries a major Old Town artery over the Stillwater River, as well as make other improvements on a crash-prone stretch of road, could start as soon as February now that the Maine Department of Transportation has purchased two properties that are in the way. The department plans to replace the bridge that carries Stillwater Avenue over the Stillwater River through a series of projects that will likely last three to four years and cost about $20 million, according to department spokesperson Paul Merrill.