BOSTON HARBOR OUTFALL TUNNEL - AN ENVIRONMENTAL IMPERATIVE

In February 1989, the Massachusetts Water Resource Authority (MWRA) be gan the design and construction of a 15.3-km subsea tunnel and ocean r iser system to discharge effluent in conjunction with the design and c onstruction of a large secondary treatment plant. The court-mandated s chedule required the tunnel and risers to be completed in July 1995. T he paper discusses the project from the viewpoints of management, conc ept design and construction methods, including the ocean riser system. Key to the success of the project is the accuracy of the location of the risers. The design calls for a final tunnel alignment to be driven within 10 m of the riser shafts, beginning at a distance of 13.1 km f rom shore.