Operations & management |


change resilience by enabling improved water management. Eligible applicants, including water and irrigation districts, water associations, universities, state agencies, private sector entities, and non- governmental organisations, have been invited to submit projects that meet the following criteria: Emerging snow monitoring technologies. Improvements to existing snow monitoring technologies. Deploying existing snow monitoring technologies in underserved areas. Improving the use of snow monitoring data to enhance water supply forecasts.


Elk River


Members of the Arnold Air Force Base crane and rigging crew recently supported a preventative maintenance project at Elk River Dam. The dam impounds the 16km2


Above: The crane and rigging crew at Arnold Air Force Base in Tennessee complete annual maintenance at Elk River Dam (US Air Force photo)


US Bureau of Reclamation NW Construction has been awarded a US$43,599,090


contract by the US Bureau of Reclamation to carry out modifications at Fresno Dam in the US. Built in 1939 on the Milk River in north-central Montana, the 84-year-old homogenous embankment earth dam has experienced 2-3m of settlement since construction. Reclamation evaluated the risk associated with differential settlement-driven cracking and internal erosion, and determined that a modification was required. To mitigate the risk, Reclamation will add a sand and gravel filter and toe drain system, with an embankment fill overlay and a vertical sand filter trench. Project construction is scheduled to begin in April 2023 with initial site activities set to include mobilisation of equipment and materials, installation of monitoring wells, and site preparatory work. Fresno Dam is a compacted earthfill structure that stands 33m high with a crest length of 630m, and an overflow-type spillway at the north end of the dam providing for a flow of 1454m3


/sec through


the concrete-lined channel. Project benefits include irrigation and municipal water supply, fish and wildlife enhancement, flood control, and recreation. Work is also underway at Trinity Reservoir in California as part of Reclamation’s ongoing dam maintenance. The task at hand includes the installation of Trinity Reservoir’s refurbished penstock intake structure. Work began on the project to rehabilitate the reservoir’s hemispherical bulkhead during low lake levels last year. Trinity Reservoir which feeds the 140MW


References


Storing Water for the Environment. Operating Reservoirs to Improve California’s Freshwater Ecosystems. PPIC Report August 2022. Sarah Null, Jeffrey Mount, Brian Gray, Kristen Dybala, Gokce Sencan, Anna Sturrock, Barton “Buzz” Thompson, and Harrison “HB” Zeff. Public Policy Institute of California (PPIC)


hydropower project is heavily dependent on spring snowmelt to fill and, as of 22 March 2023, it was at 36% of capacity (50% of historical average). Reclamation says that snow plays an important role in water supplies in most of its watersheds and understanding snow conditions is critical for water supply forecasts relied upon by reservoir operations and broader water management in the Western US. Climate change is impacting precipitation and snow accumulation/ melt patterns and uncertainty remains about snow conditions, timing, and magnitude of snowmelt runoff. With the above in mind Reclamation is making


up to US$11.75 million available for emerging snow monitoring technologies to help build climate


20 | May 2023 | www.waterpowermagazine.com Woods Reservoir, which serves


as the source of water for Arnold AFB, headquarters of Arnold Engineering Development Complex. Water from Woods Reservoir is used at the base for cooling test cells, fire protection, sanitation and drinking. Upkeep on the three large tainter gates, two sluice


gates and the leaf gate of Elk River Dam are completed annually. The work must be performed during the winter months, as this is when the endangered grey bats that reside at the dam for most of the year migrate to caves to hibernate. “This requires a lot of work to be accomplished in about a three-month period which also happens to be in the middle of the winter, exposing the workers to some of the most extreme cold periods of the year,” said Jason Farris, Operations and Maintenance Superintendent Manager for the AEDC Test Operations and Sustainment contractor. Crews received word that the last two bats had


departed the dam in early December. “All gates were inspected quickly, effectively and well before the end of the three-month work window,” said Tyler Swann, Air Force Utility Asset Owner and Dam Manager. “Preventative maintenance was executed while having a very late-start opportunity.” Stoplogs must be installed in each of the three


tainter gates to block off the water and allow the gate to be cycled while the trunnion pins and other mechanical equipment are lubricated and checked for proper operation. Each gate must be cycled fully open to fully closed several times. “Cycling the gate is part of ensuring reliability, so


the routine of installing the stoplogs is critical to that process,” Farris said. “While the stoplogs are installed, it allows a chance for visual inspection of the gates and spillways so any problems can be caught early and repaired.”


As well as inspecting and maintaining the hydraulic


systems that operate the sluice gates and leaf gate, workers also test and perform maintenance on the gate control systems. Each year, after all the work is completed, the crew inspects and repairs the stoplogs to get them ready for use the following year. The work provided by the crane and rigging crew at Elk River Dam supports a number of preventative maintenance projects overseen by Base Civil Engineering. “We provided over 1600 manhours to this effort with no accident,” Farris said, commending the crew’s focus on safety in each and every task daily.


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