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Estimated costs for flood protection work on the Water of Leith and Lindsay Creek have more than doubled to $53 million, latest figures released by the Otago Regional Council show.
However, council staff have proposed an alternative 15-stage scheme that could reduce the costs to ratepayers by about $22 million and still fit within the resource consents already granted for the work.
The alternative scheme would still cost $10 million more than the $21.4-million, six-stage scheme taken to public consultation in 2005, which aimed to improve the standard of flood protection to North Dunedin, the University of Otago campus and the central business district.
At present, the standard of flood protection is lower than accepted for the type of land use bordering the waterways.
At the council's engineering and hazards committee meeting tomorrow, councillors will consider the revised cost estimates and alternative plan.
They will also be asked to recommend that another report be written on the impacts of the changes, the viability of the scheme and how the scheme could be funded, for presentation to the full council.
Council engineering manager Ramon Strong said in the report the council had already spent $10.3 million on the project, including the completed works at Rockside Rd, repairs arising from the April 2006 flood, gaining the consents, fighting an appeal and the current works from Cumberland St to Dundas St.
Of highest priority was the Dundas St to Forth St works on the Leith through the University of Otago campus, as there was high risk of floodwaters escaping from the river bed at several places - which could lead to flooding of a significant area of central Dunedin, he said.
The council had already spent time and resources on developing a detailed design of the work to be done on the stretch, "only to have much of it potentially made redundant" with the release of the campus master plan last May, Mr Strong said.
However, the master plan, if implemented, could provide less expensive and "more robust" options for the flood protection work - but could also require new investigations and possibly resource consents.
Critical to the whole scheme was the university's timeline to implement the master plan, as it suggested demolition of its building that straddled the Leith.
"The further into the future this is planned for, the more it creates issues for council in terms of how the flood risk is managed," he said.
"... The timeline for the scheme as a whole is impacted by decisions made in relation to the campus master plan."
The university released the campus plan in May last year.
The university council has yet to publicly consider which projects should be progressed and how they might be funded.
Mr Strong said in his report the regional council's revised scheme relied on being able to progress issues with the university, but if there were delays, work on Lindsay Creek would progress instead, with the focus on North Rd to Watts Rd.
It was also assumed works could progress beyond the 2018 consent expiry date by applying for a variation, he said.
1997: ORC first looks at enhancement for Leith Lindsay.
2003: Dunedin urban flood protection scheme adopted in long-term plan.
2003: Opus contracted to provide scheme design.
2005: Council endorses the scheme and public consulted.
2006-07: Resource consents granted. 2008: Environment Court appeal held and declined.
2009: Opus provides updated cost estimate on scheme.
2010: Campus Master Plan announced.
2010: Work starts on Cumberland St to Dundas St works.