Greymouth floodwall repairs to avoid whitebaiting season

Nicole Mathewson Reporter from The Press

By local democracy reporter Brendon McMahon:

Repairs will soon begin on a slumping section of the Greymouth Floodwall at Blaketown, ahead of a wider upgrade to raise and widen the wall.

West Coast Regional Council area engineer Paulette Birchfield said a slumped section of the wall needed to be fixed on the Blaketown Tiphead, just east of the Blaketown Rugby Club.

It was being timed to follow the end of the whitebaiting season.

Birchfield said the work, costing $60,000, would require a road closure on the Tiphead, anticipated for two days in early November. Henry Adams has been contracted to carry out the work.

The work was routine, although the narrowness of the Grey River at the repair point had a bearing.

"Any rock work does need maintenance over time … generally it's fairly stable."

The river channel generally moved within the bed over time and the main flow was currently hard up against the true left bank by Blaketown.

The resulting scouring effect impacted on the rock facing of the wall, with stone slumping down the wall face into the channel.

The solution was to top the rock up, from above.

Birchfield said the wall was constructed knowing regular maintenance would be needed, as for any river protection wall in the region.

About 400 tonne of rock would be transported from one of council's quarries, with each piece placed from the top using a claw on a digger.

A similar fix costing $75,000 to repair rock rip rap on the Punakaiki seawall was completed last month.

Meanwhile, the bigger project to widen and raise the Greymouth Floodwall across its entire footprint is moving towards the tender stage.

A report to council's Infrastructure Governance Committee on October 10 noted tender documentation had been issued to a pre-approved group of contractors at the end of September.

The existing resource consent for the floodwall was also undergoing a legal review.