Linwood Water Tunnel

Challenge

Originally constructed in 1920, this 1.3-mile tunnel is buried 80 to 120 feet below grade. The tunnel connects the Riverside pumping station to the Linwood Water facility.

Every 20 years, the Linwood Tunnel is inspected and maintained. The tunnel was completely lined with concrete as part of a previous repair, which can conceal structural details.

Solution

In 2014, Kapur partnered with a national tunnel firm to act as the local presence on the Linwood Tunnel investigation and rehabilitation. The purpose of the project was to address deficiencies in the tunnel, vents, and structures at both ends of the tunnel. Our role was to investigate, report, prepare plans, and assist in surveying the gate and vent areas for repair.

Among the tasks were removing more than 3.5 million gallons of water from the tunnel, ventilating and lighting the length of the tunnel for survey, and completing inspection in 36 hours. Kapur survey staff provided horizontal and vertical control, alignments, scanning, and sectioning to ensure tunnel integrity (roundness). Our inspectors evaluated 15 gates at both ends of the tunnel as well as ventilation areas along the entire stretch of the 9-foot high tunnel.

Results

Despite the fact that the gates and tunnel were in good condition, longitudinal cracking in the tunnel necessitated more than 7,500 linear feet of grout repair. To reduce dewatering efforts and expedite repairs, all work was completed during the winter and within the planned 90-day window.