Slick tunnel snakes under Sacramento

摘要

Sacramento's new Upper Northwest Interceptor (UNWI) is currently being constructed using a novel tunnel lining technique never before used in the US. The 3.6-mile long (5.8km) tunnel is being lined with PVC-coated segments, which have a low frictional coefficient, particularly when wet. The design for the wastewater tunnel was selected to minimize deterioration by corrosive sewer gases, and eliminate the need for carrier pipe. Workers clean water from the invert and heat-weld strips of PVC between rings as the project's 14ft (4.25m) diameter Robbins EPB advances. By the time the tunnel is completed, crews will have performed over 62 miles (100km) of welds, creating a seamless inner liner.