Written by Bijan Khamanian for Trenchless Technology®

Through a design-build alternative delivery method, San Diego County Water Authority undertook the rehabilitation of its First Aqueduct Treated Water Tunnels located in Escondido, California.

The timely rehabilitation of the First Aqueduct is part of the Water Authority’s proactive asset management program. An essential element of providing safe and reliable water supplies is assessing the agency’s 310 miles of large-diameter pipeline and making the upgrades necessary to continue serving the region. That work, funded through water bills paid by residents and businesses across the county, sustains the region’s $245 billion economy and quality of life.

“The First Aqueduct delivered imported water to our region for the first time more than 70 years ago, and it remains critical to water supply reliability for our region to this day,” said Gary Croucher, chair of the Water Authority’s Board of Directors. “Coordination across Water Authority departments and collaboration with our member agencies allowed us to complete this extraordinarily complex project and ensure these pipelines operate for generations to come.”

Through a lengthy statement of qualifications and approval process, the agency awarded the project to Michels Trenchless Inc. and Stantec. The initial design package identified several methods for relining these tunnels. Welded in place steel plates, sliplining with FRP, cured in place pipe and spray on liners.