Overview
The Cheesman Dam had significant hydraulic leaks in its in-water and topside gates. Rapid execution of emergency repairs to the submerged mid- and low-level auxiliary gates, and the topside jet-flow gate was crucial, as leaking hydraulic fluid had caused one gate to fail without warning. Another failure was assumed imminent based on additional visible leaks in the reservoir, threatening public safety and the local fly-fishing industry which relies on a closely monitored marine environment.

Scope of Work
Ballard worked with Denver Water to repair and refurbish a total of three cylinders and their respective hydraulic bypass lines to resolve the immediate concern. Testing identified the extent of leaking and subsequent damage to the submerged systems, allowing the development of a technical repair plan to proceed. The root cause of the leaks around the upper and lower seals of the hydraulic cylinders was significant microbial corrosion in the crevices of the stainless-steel connecting hardware, and damage to the internal seals due to excessive testing pressure during original commissioning. In response to the significant amount of corrosion, Denver Water and Ballard began designing a Cathodic Protection (CP) and anode system.

Innovative Solutions
The CP and anode system was designed to preserve the dam’s hydraulic structures from further deterioration associated with excessive corrosion. Requiring installation of anodes and reference electrodes at each gate, each wire was brought to the surface and secured at the dam’s main control building for integration into Denver Waters future control system. The secondary line of defense for the CP and anode system was to install ten cast iron anodes per gate—each sixty inches long and two inches in diameter—with pipe straps to the rock face. Each anode wire was routed through bundles secured along the reservoir bottom to the shoreline, with nylon protective wrap where required.

Results
Ballard refurbished all three cylinders which included the machining, installation of new seals, and reassembly of these cylinders. Final acceptance testing followed re-installation of the three submerged gates. Ballard performed this emergency work on a short notice and time critical schedule requiring pinpoint precision to complete the work before a catastrophic failure occurred. After installing the new hydraulics, as well as the cathodic protection system, Ballard supplied Denver Water with a new level of security within their system.