Advancements in Trenchless Technology: San Diego’s First Aqueduct Treated Water Tunnels Rehabilitation Progressive Design Build Project Evaluation

The Project involved rehabilitating three 72-in. tunnels, with unique condition and accessibility challenges, under a compressed design and construction schedule of less than 1 year with three 10-day shutdowns to work in the tunnels. The project team, comprised of Michels Trenchless Inc. and Stantec, implemented innovative solutions to address these challenges. Geopolymer lining and fiberglass reinforced pipe (FRP) were selected to restore the tunnels' integrity and extend their lifespan by 75+ years. The team installed approximately 3,600 ft of the geopolymer liner in the Lilac and Red Mountain Tunnels during two 10-day shutdowns. For the more deteriorated Oat Hill Tunnel, 63-in. FRP sliplining was used. The project team set a new record for the largest diameter and fastest installation of FRP sliplining, completing 3,600 linear feet around the clock in just 3 days. The project achieved timeline milestones, completing the rehabilitation within the three planned shutdowns of 10 days each.