Project Overview

Mountain Tunnel is an approximately 19-mile-long water tunnel that has served the Bay Area since 1925 as part of the Hetch Hetchy Regional Water System. The tunnel carries drinking water by gravity from Hetch Hetchy Reservoir through Kirkwood Powerhouse to Priest Reservoir and helps provide reliable water service to approximately 2.7 million customers in the Sierra Foothills and San Francisco Bay Area.

After more than 90 years in service, the tunnel required significant repairs and improvements to address deterioration and maintain its long-term reliability. Much of the work takes place underground and requires the tunnel to be temporarily drained and taken out of service during scheduled construction shutdowns.

Challenge

Inspections identified deterioration of the tunnel lining along with cracking, spalling, groundwater intrusion, leaks, and other deficiencies. These conditions had reduced flow capacity, increased turbidity, and made routine maintenance more difficult. The project team needed dependable repair materials capable of addressing a variety of concrete conditions throughout the tunnel while helping restore structural integrity and reliable water conveyance.

Solution

SpecChem products were used as part of the repair work throughout the Mountain Tunnel. SC Multi-Purpose Grout provided a versatile grouting solution for repair and support applications, while SpecPatch 30 was used to restore damaged and deteriorated concrete. SpecPlug helped address active water intrusion and leaks, and SpecPoxy 1000 provided a high-strength epoxy bonding solution for concrete repair applications.

These products supported broader tunnel improvements that include repairing deteriorated lining, improving maintenance access, restoring hydraulic performance, and addressing other deficiencies throughout the system.

Result

Mountain Tunnel Construction successfully used SpecChem repair materials to address cracks, spalls, leaks, and other deteriorated areas throughout the tunnel. The completed repairs are helping restore the tunnel’s condition and reliability while supporting its continued role in delivering drinking water to millions of customers throughout the Bay Area. The broader improvement program is intended to extend the useful life of the tunnel, improve operational flexibility, and maintain dependable water delivery for years to come.

Products Used