- Boston, USA
- PBA 818
The Boston Outfall, in Massachusetts, U.S.A., is the world's largest tunnel outfall. The outfall represents the latest in tunnel outfall technology and when completed will discharge up to 1300 million gallons per day of secondary treated effluent through a system of seabed diffusers, nine and a half miles off the coast of Boston.
For the actual drilling of the riser holes two new Wirth PBA 818 casing top drilling rigs were purchased. Along with bottom hole assemblies for diameter 1,7 m and 1,35 m.
The soil has a compressive strength of 105 MPa. When execute drilling their where two mayor storms, but the project was finished ahead of schedule.