Waimea Water Ltd (WWL) says the forecast cost and timeframe for the build of the Waimea Community Dam have been revised after encountering unforeseen geological conditions.
The projected new cost is $129.4 million and there is now a two to four-month delay, largely attributable to problems identified with the rock-fill during testing in early 2020. The dam’s construction had been costed at $104.4 million in 2018, and the project is currently two months behind due predominantly to the region’s fires last year.
WWL CEO Mike Scott said much of the rock has met expectations, such as embankment foundation. However, earlier this year some areas of rock designated for use as drainage material in the embankment became a concern.
“Some rock was found to be more fractured and breaking up more readily than expected. This particular rock was to be used for the drainage zones of the embankment, but testing has confirmed that it is not of a high enough quality to be used for this purpose,” says Scott.
“We’re now looking at potential solutions, which may include purchasing and importing some rock from a nearby quarry for the drainage layers or using rock from other locations in the valley. We estimate the issues with the quality of rock and additional stabilisation predominantly contributes to adding $25 million to the project,” he says.
“As always we are looking for opportunities to review components of the dam’s design to save on costs wherever we can; all without compromising on the safety, efficiency or reliability of this significant infrastructure project.”
Scott said that WWL has always been open and upfront about the risks around the project, particularly about the potential challenges with the geology and topography of the site.
“We always knew, the extent of the risk would not be fully understood until excavation and construction was well underway, and risks will persist throughout the period of construction. Risks will dissipate as construction progresses and as we come out of the ground later in the year. We’re managing every step of the project really closely to ensure that we are across any changes that might be needed early in the process,” says Scott.
The dam is continuing to make good progress with construction on the right-hand abutment, left-hand plinth, permanent stabilisation above the right-hand side plinth and the diversion culvert underway. On any given day of the working week, approximately 100 people are now working on site. “We understand the importance of this much-needed infrastructure project for the region and remain committed to constructing and operating the dam as sustainably, efficiently and reasonably as possible.
“We’re holding a public forum at the Richmond Town Hall at 6.30pm on 31 March to give people the opportunity to hear more about the design and build of the dam, and answer any questions that they might have,” says Scott.
Anyone interested in attending is asked to register and provide any questions or outline what you would like to hear about by emailing firstname.lastname@example.org by Friday, 27 March.
More information about the project will be available in WWL’s mid-year report and draft Statement of Intent due to be presented to the Tasman District Council on 26 March 2020.