Clarrie Hall Dam Reopened
Council's $7.3 million upgrade of Clarrie Hall Dam was unveiled on 22 May 2014 by the NSW Minister for Natural Resources, Lands and Water, the Hon. Kevin Humphries, MP.
By widening and extending the spillway and raising the dam's wave wall, it now meets the revised standards of the NSW Dam Safety Committee and provides greater control of extreme flood levels in the dam.
A number of innovations during design and construction resulted in the project being delivered on schedule and $300,000 under budget.
During the ceremony, Local, State and Federal Government representatives praised the innovation of the project management team, which included construction contractors, Entracon Civil, Tweed Shire Council, NSW Office of Water and NSW Public Works.
Innovations during design and construction helped to overcome a number of challenges, including the terrain and extreme weather and flood risk, but also resulted in the project being delivered on schedule and $300,000 under budget. Innovations included:
- The design and construction of an angled spillway crest to increase the length of the spillway and enable more water to pass over it at any one time, while also avoiding costly excavation into the adjoining extremely hard rock face.
- Pouring more than 200 concrete blocks onsite to reduce transportation time and cost. These blocks could also be reused if the storage capacity of the dam is ever increased as part of future supply augmentations."
- To overcome the issue of limited access at the site, an 85-tonne crane was perched on top of the existing dam wall, a feat within itself. The crane was used to move building material and machinery into and around the construction site.
The event was also attended by members of Council's Aboriginal Advisory Committee, descendants of former Tweed Mayor, Clarrie Hall and other guests.
New signs at the site further recognise the cultural significance of the local area for Indigenous culture.
The State Government contributed $1.2 million to the project.
Clarrie Hall Dam Reopening Photos (2.84mB PDF).
About the Upgrade
The upgrade provides greater control of flood levels in the dam. The $7.3 million project increased the spillway capacity to ensure the dam can safely pass extreme flood events in accordance with new standards established by the NSW Dam Safety Committee.
When Clarrie Hall Dam was commissioned in the early 1980s it complied with the engineering standards of the day. Since then however, the NSW Dams Safety Committee have revised these standards as access to rainfall and extreme weather predictions and data has improved.
Clarrie Hall Dam can pass floods many times greater than the largest flood on record. However, Tweed Shire Council has now upgraded the dam’s spillway capacity to ensure the dam continues to meet safety requirements and more importantly protects the safety of public and property downstream of the dam in the unlikely event of extreme flood.
Construction is complete
Construction involved widening and extending the existing spillway.
The upgrade raised the spillway crest and there was no change to the storage’s full supply level or the storage inundation area. However, an existing parapet wave wall across the dam crest was raised to avoid overtopping of flood waters and create a larger margin between the top water level and the top of the dam structure.