Work Underway Soon On Ross Creek Reservoir Dam Refurbishment Project

Dunedin (Monday, 22 April 2013) – Work will begin soon on the first stage of a major project to refurbish the historic Ross Reservoir dam embankment.

The dam has been closely monitored since large cracks appeared in 2010. The monitoring plan to date has included an irrigation system on the dam face and gradual lowering of the water level to prevent further instabilities occurring.

The refurbishment project, which is part of a wider strategy to provide better water security for Dunedin, will involve some bush and tree clearance, temporary track closures and significant construction work.

DCC Water and Waste Services Asset Strategy Team Leader Tom Osborn says the DCC is very aware Ross Creek is one of the city’s most popular recreational areas.

“We will make every effort to retain as much public access as possible during construction, but safety of the public and people working on the site must come first.”

Opus has the contract for the design and construction management for the dam refurbishment. Initial surveying has been completed for the preliminary design, but some clearing work must be done to enable a detailed survey and design of the new dam face to be carried out.

The first stage of the Ross Creek Reservoir dam refurbishment project will involve clearing about 0.5ha of bush and scrub below the main embankment. Tenders for the clearance work will close on 22 April and the selected contractors will start on 6 May. Work is expected to take up to two weeks. Tracks around the embankment, including the crest track, will be closed during this time and there will be noise and disturbance associated with scrub clearance between 8.00am and 5.00pm, Monday to Friday.

After the first stage in May is finished, there will be only minor activity on the site until major construction starts about October. This work is expected to last for about a year. Several of the tracks around the embankment will be closed during this period, but all tracks north of the crest will remain open throughout. Notices will be put up on site to advise track users of closures.

“We are looking at ways to improve the connectivity of these tracks during construction to try to minimise the impact of users of the reserve,” Mr Osborn says.

Mr Osborn says some local road closures or traffic redirections may be required as part of the major construction works later in the year, but the extent of these won’t be known until construction tenders close, which is expected to be in August. The DCC will work closely with affected parties to minimise disruption during this period.

There are no listed significant trees on the site to be cleared and staff are working closely with the DCC Parks and Recreation team who manage the reserve. The new dam face will need to be kept in low-level cover such as grasses, but the remaining area will be replanted when all work is complete.

The Ross Creek Reservoir, which was completed in 1867, has not been used for about 20 years. The dam is the oldest large earth dam in the country, and has Historic Places Trust category one status, but it is in poor condition and needs attention to ensure its ongoing safety. As part of the work, 15,000cu m of fill will be brought in to stabilise and extend the embankment. The DCC is working closely with the Trust on the project.

The refurbishment of the dam would mean the reservoir’s existing capacity of 130,000cu m could be used once more, with the water level in the reservoir restored to its ‘normal’ level after several years of being lowered. The Ross Creek Reservoir dam project is a key part of an overall strategy to ensure the city has water supply options should there be any problems getting water from Dunedin’s main water sources – Deep Creek and Deep Stream.

The first part, which will happen this year, is the construction of a pumping station between the Southern and Mount Grand Water Treatment Plants, expected to cost $600,000.

The next parts are the $2.1 million renewal of the Ross Creek Reservoir dam and the construction of a $3.4 million pumping station and pipeline between Ross Creek Reservoir and the Mount Grand plant.

“Once these projects are complete, water supply could be maintained to the entire city if the Deep Creek/Deep Stream pipelines were lost, for example through a seismic event,” Mr Osborn says.

The Ross Creek/Mount Grand work will require the old Ross Creek treatment plant site to remain off-limits to the public for possibly another year after completion of the dam embankment as it will probably be the field office and yards for the pump station and pipeline project. The old buildings will be used to house the new pump station.

“It’s great to be able to improve the resilience of the city’s water supplies by re-using historic assets.”

The projects that make up this new strategy are considerably cheaper than those originally proposed and budgeted for in previous Long Term Plans. In total, the strategy should deliver savings of up to $11.2 million between 2012 and 2022.
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