Lake Paluma is a drinking water storage facility owned by Townsville City Council and is situated close to Mount Spec, high above the Paluma Range National Park. Lake Paluma has a capacity of 11,800 megalitres. The dam is part of a unique water supply system that gravity feeds up to 50 megalitres of water per day to the city of Townsville. For most of the year, water flowing from the Mount Spec part of the national park is collected and filtered at the Crystal Creek intake and then piped under gravity to Townsville. When Crystal Creek water levels are low, water is released into the creek from Lake Paluma via another gravity pipeline. Flow into the pipeline is controlled via three 750mm gate valves located in a valve tower structure, situated 50m inside the dam wall. Access to inspect each valve is by a permanently fixed ladder system and a 70m long tunnel, which also contains the outlet pipe.
Prior to SURV’s involvement, the top and middle valves were operable, although with some difficulty. The top and middle valves are installed 8.5m and 14.6m below the floor level of the valve control room, respectively. The SURV team exercised the top and middle valves using a handheld pneumatic actuator, from fully open to fully closed and back to open. This cycle was repeated two further times for each valve. On completion, both valves were noticeably easier to operate by hand, than had previously been experienced. The bottom, or Scour valve was inoperable and the last recorded successful exercise of the valve was in 1998. Preliminary enabling work had taken place to facilitate replacement of the Scour valve, which is installed 18.6m below the floor level of the valve control room.
Due to the restricted access issues and the size of the asset, if the valve needed to be replaced it would have to be dismantled in situ, before removal would be possible. Also, the replacement valve would need to be dismantled and rebuilt in situ for the same reasons. The estimated cost of replacement was $62,702.50 for the Scour valve and approximately $180,000 for all three assets.
The SURV valve release equipment was installed on the 18m long Scour valve extension spindle and varying levels of resonance were applied. After approximately 30 minutes release was achieved. The valve was then cycled to fully open and back to closed, without the use of resonance whenever possible. Subsequently, the valve was operated by hand, through 50 complete revolutions (approximately 25% open) and back to a fully closed status.