Something fishy is happening at Woollen Mills Dam
07 April 2017
Something fishy is happening at Korokoro Valley’s historic Woollen Mills Dam
Work is soon to begin on strengthening Belmont Regional Park’s Woollen Mills Dam in the lower Korokoro Valley to make the dam more resilient to floods and easier to pass for fish.
A 2015 Damwatch Engineering report, commissioned by Greater Wellington Regional Council following flooding in May that year, found that water scouring has undermined the dam’s foundations by about one metre.
“There’s no imminent danger but the dam fails stability criteria for 100-year flood loading so we will repair it to ensure it returns to its 100-year flood and 500-year earthquake loading. We’ll also install a fish passage to enable aquatic life to navigate the dam,” says Principal Ranger Assets and Maintenance Bronek Kazmierow.
Contractors will be on-site from this week and work will continue for between six and eight weeks depending on weather.
Two areas will be repaired. Concrete will be pumped under the damwall to reinforce the toe of the dam; the downstream section of the dam’s spillway, damaged by a rockfall, will be repaired.
A fish passage ladder will also be installed by the dam’s slipway to enable fish to migrate up and downstream between different habitats within the stream’s freshwater. The ladder will slow and pool the water to ensure fish movement is possible.
“If these movements are delayed or blocked completely, fish may be unable to reach critical habitats for completing their lifecycle.” says Bronek.
The neighbouring Korokoro track will remain open, but the area under construction will be fenced off and track users should watch out for construction traffic.
ENDS