Concrete Reservoir Adit Tower Rehabilitation

The Crystal Springs Reservoir, constructed in 1888, is located in San Mateo, California and is owned and operated by the San Francisco Public Utilities Commission. The Crystal Springs outlet structure transfers water from lower Crystal Springs Reservoir to Crystal Springs pump station. The outlet structure consists of three adit towers. Adit towers are generally vertical, large-diameter concrete pipes that serve as vaults for valves that are used to drain and fill a reservoir. 

Many of these towers and reservoirs, like Crystal Springs, are old and deteriorating. External cracking is typical above the waterline; weeping and leaking cracks are often present on the interior; and the valves, piping, and infrastructure are often corroded. 

The Crystal Springs adit tower is approximately 129 feet deep and 14 feet in diameter. The tower was constructed of mortar-lined, unreinforced brick masonry. The concrete walls of the adit tower were cracked and spalled. The cracks were clearly visible on the exterior surfaces above the waterline and leaks were observed at many elevations within the tower. The leaks also resulted in corrosion of the steel surfaces within the tower.

For this project, the team used our pressure-injected 151-HG hydrophobic grout to stop leaks. The grout reacts with water to form a foam with significant strength and adhesion. Once all active leaks were stopped, the team then coated the interior walls. What was unique about this project was that the interior surfaces exhibited moisture permeating from the exterior of the tower. Typically, coatings need to be applied to a dry surface as the moisture can cause disbondment of the lining. However, Warren’s epoxy has proven results being applied to damp surfaces. It was able to line the entire interior of the adit tower. Steel surfaces such as the flange and valves were coated as well. 

The project was reinspected four years later and showed no signs of leaks in the walls of the tower. The lining remained free of blistering or pinholes, and the carbon steel was corrosion-free.