The completion date for the Casey Arborway, which had already been pushed off three months, has now been delayed another nine months. That means the mammoth project is expected to be finished a full year later than originally forecast, the Massachusetts Department of Transportation announced Wednesday. The project is behind schedule due to issues with jet fan procurement, according to officials at a public meeting Wednesday evening held at English High School. The necessary jet fan system is expected to be received in August and installed this fall, and consist of six mounted fans that ventilate and cool the tunnel system, according to MassDOT officials. In the meantime, officials will juggle the schedule of what gets done when so crews can work away from jet fan areas, including Shea Circle, west of South Street and south of the Arborway.