In 2005, BC Hydro commissioned a study to assess the reliability of the spillway gate systems at 11 BC Hydro dams. These assessments, which were carried out between June 2005 and August 2006, revealed various site-specific and several “systemic” deficiencies at each of the sites reviewed. It was concluded that equipment and procedural improvements would be required to ensure that the flood discharge gate systems at all BC Hydro sites have adequate reliability for flood discharge on an ongoing basis.

In September 2006, BC Hydro appointed the consultant team of Hatch Energy, with subconsultants Cegertec Inc. and Alcan Primary Metals (Centre of Excellence in Energy), and Manitoba Hydro International, to evaluate the BC Hydro findings for seven sites, and confirm, categorize and prioritize the issues raised, as well as identify other possible deficiencies through further site visits and discussions with BC Hydro staff (identification study phase).

In July 2007, BC Hydro appointed the same consultant team to undertake a definition phase study of the seven sites to further investigate the specific tasks extracted from the identification study findings.

Scope of Services
The initial identification study phase of the assessment of spillway gates at seven dam sites, including Cheakamus, Stave Falls, Ruskin, Terzaghi, Seton, Hugh Keenleyside and Duncan, involved the following:

• Workshops with BC Hydro to review minimum requirements for gate reliability and safety, and the needs of the program
• Search for and review of drawings and other records and relevant documentation for each site
• Visits to each site to review the gates and associated structures, operating systems, related instrumentation, protection and controls, operational reliability, power supplies and related issues
• Assessment of existing equipment reliability against BC Hydro standards
• Structural analyses of the gates and supporting structures including the consideration of updated seismic loading criteria
• Recommendation of action items to be initiated immediately to improve operations and safety in the short term
• Review of upgrade items that would be required to meet BC Hydro requirements, including review of options and associated cost estimates
• Preparation of comprehensive reports that documented all investigations along with recommendations on which of the reviewed options should be implemented by BC Hydro to upgrade the gates and systems

The definition phase advances the previous work by developing designs for upgraded electrical and mechanical systems and refurbishment and in some cases replacement of concrete structures.

• The mechanical systems upgrades include replacement vertical wheeled gates, hoists with alternative drives and hoist structures, reinforcement and modification of existing radial gates to meet current design standards. The electrical systems upgrades include multiple power supplies and multiple hard-wired control stations, all aimed at meeting the required degree of redundancy and separation necessary to meet the high level of reliability demanded of a flood discharge system. In some instances, higher than normal factors of safety will be employed rather than adding redundancy since this was found to be a more cost-effective method of achieving the target level of reliability
• A fault tree analysis was undertaken of the selected designs to demonstrate that the target level of reliability was met.
• Preliminary designs and drawings were prepared in accordance with the developed design basis memoranda. Implementation project schedules and detailed first principle budget cost estimates were prepared for each site and used in the preparation of the owner’s business case documentation. It is anticipated that three of the projects will be implemented during the next three years and the remaining four the following two years