Westport’s flood protection scheme is likely to take three years to build, says a report to today’s Westport Rating District Joint Committee (JC) meeting. But building is not likely to start for eight to 12 months.
The report, prepared by consultant John Hutchings, said it could take up to a year to gain funding, consult landowners, confirm final designs, get consent and tender for services and materials.
Costs, alignments and materials have all changed significantly since the project was consulted on last year, the paper revealed. The latest cost estimate is $26 million instead of $10.2m. Designs preferred by the Technical Advisory Group (TAG) now leave Snodgrass Road and a big chunk of Nine Mile farmland out of the protection area. However, more of Carters Beach, the airport and golf course would be inside the walls.
Recommended materials had also changed significantly since the first proposal.The original proposal was for concrete walls along the central business district part of the Buller River as well as part of Orowaiti Road and the Snodgrass Road bend. The rest of Westport would be encircled by a stopbank.
The TAG has now recommended a combination of concrete, timber and earth-filled walls, depending on each site. It also recommended higher standard walls along the Buller River than beside the Orowaiti estuary.
The new designs incorporate climate change models into the Buller River side of the wall but stick with current one-in-100-year models for the Orowaiti side.
The report said flooding from the Orowaiti had a “less dangerous nature” than Buller River flooding. Lower walls would also lower the cost of the project by $650,000 and reduce environmental and amenity impacts.
River engineer Gary Williams recommended building the walls in eight stages, starting with the riskiest areas, but also considering the ease of construction and “consent-ability”. The stages (in order) were:
• Buller upper ($3.6m): from Buller Bridge, past O’Conor Home;
• Orowaiti upper ($2.5m): from previous section to railway embankment near McKenna Road;
• Buller lagoon ($1.25m): Westport Harbour and lagoon, past Shingle Beach to meet tiphead wall;
• Carters Beach ($1.7m): from Elley Drive to Golf Links Road, behind settlement and state highway;
• Orowaiti lower ($4.8m): from Orowaiti upper section, encircling Kew and Eastons roads, along Orowaiti Road and Craddock Drive;
• Buller lower ($1.4m): parallel to Palmerston Street, connect Buller upper and lagoon sections;
• Coastal ($900,000): behind North Beach to connect Orowaiti and Buller lagoon sections;
• Airport ($2.25m): from Carters Beach section, eastward toward Buller River along Schadick Avenue.
Once all the preliminary work was done and consents gained the stages would be divided into three years of work. Mr Williams said the floodwalls themselves were “simple structures”. “The flood defences are straightforward works to construct. The stopbanks would be constructed using readily available earthmoving equipment.
River engineer Gary Williams recommends building Westport’s $26m floodwalls in eight stages over about three years. Photo: supplied