After the November 14 Kaikoura earthquake, Greater Wellington Regional Council and specialist engineers at Dam Safety Intelligence Ltd inspected the dam as part of its post-earthquake routine.
An earlier survey had shown a surprisingly high amount of sediment so, despite the dam receiving no earthquake damage, engineers reactivated an intake pipeline to lower the water level in case a subsequent earthquake caused a breach.
"The waterfall has been affected but it is better to err on the side of public safety and, in fact, return the dam to its normal operating mode," council parks manager Amanda Cox said.
The water level would remain low for the foreseeable future.
In January council want to reopen another valve, the scour valve, to provide double insurance against water build up. "The valve will need to be reactivated to ensure we have two means of de-watering the dam."
Geotechnical engineers had completed a survey and the council expected their report in January. "There are no indications at this stage of any specific geotechnical site works being required."
Cox said the inspection was routine and entirely precautionary after any unusual events, such as the earthquake and flooding in November.
The dam was built in the 1930s and decommissioned following the opening of the Kaitoke water scheme in the 1950s. It is part of a popular walking track.
http://www.stuff.co.nz/national/nz-earthquake/87642735/waterfall-not-flowing-at-birchville-dam-after-earthquake-inspection
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