Essential Infrastructure Repairs

  Wharf update as March/April 2023

Repairs to the Holcim and Kawatiri wharves at Westport will enable fishing and bulk shipping vessels to continue to use the port.

This is one of the largest projects under this programme and work is expected to begin in the third quarter of this year. It will then take about a year to complete.

Meanwhile, the demolition of the KiwiRail buildings adjacent to the port is progressing. All asbestos has been removed and a clearance certificate issued. Excavators are accelerating the demolition process which aims to recycle and salvage as much material as possible.

 Wharf update as at February 2023

KiwiRail will start work removing two buildings from its land north of the port at Westport in February 2023 starting with site set up and the installation of fencing.

The buildings are deemed to be unsafe. The full removal will take approximately two months to complete.

Up until late last year the building was leased from KiwiRail by the Railway Preservation Society and the Buller Cricket Association. New homes have been found for the machinery and artefacts previously housed there. The building was originally a storage facility for freight coming onto and leaving the rail network.

The demolition professionals engaged will be looking to salvage and recycle as much as possible. Locals should expect trucks and excavators on site during demolition.

Once the old sheds are removed, Buller District Council will access the Kawatiri Wharf for essential repairs. That wharf, and Holcim 2 Wharf, were damaged during the July 2021 and February 2022 flood events in Westport. Repairs on the two wharves is expected to take approximately a year.

 Background

Buller District Council is responsible for more than 1.5km of wharf assets. This project focuses on an area of around 300 metres of flood-damaged wharf (at the upstream area of the river wharves). This portion of the overall wharf area is considered critical to current and future Port operations.

Repairs to the Holcim and Kawatiri wharves will enable fishing and bulk shipping vessels to continue to use the port. Among other issues, holes have opened up in the decking of the Ex-Holcim Wharf due to underlying flood induced failure and significant deflection has occurred in wharf piles.  Holes and slumping are visible.

A project manager has been appointed to oversee repairs to the Holcim and Kawatiri wharves.

A crucial part of the wharf repair project is understanding ground conditions so that the repair design is appropriate. In September 2022, a specialised drilling rig drilled three 20-metre-deep holes along the length of the damaged wharf and tested ground conditions at regular (1m) intervals.

The foundation design of the repaired structure will be informed by the results of this investigation work. The overall repair strategy, design and approvals are scheduled to be completed in the first half of next year, with physical repair work forecast to commence in Autumn 2023 and take approximately a year to complete.

 The floods caused a build-up of debris and gravel/silt in the navigable part of the river and port. Approximately 240,000 m3 of debris, gravel and silt that needs to be removed to return the river to a state that it can be serviceable to the bulk carriers expected to be using the port in the future.

The Kawatiri Dredge was in Nelson for maintenance and to carry out dredging work from October until early December 2022, and has recently returned to Westport. It has now commenced dredging of the shipping channel.

March/April 2023 Update

Dredging of the shipping channel is underway with almost 60,000 cubic metres of debris, silt and gravel removed so far.  The goal is to remove 240,000 cubic metres of debris in total for this programme.

Expert advice we’ve received indicates that dredging as part of flood resilience isn’t seen as cost effective. This is because the river in flood moves enormous amounts of silt and gravel to create space for itself. The objective of the current work is to keep the Buller River’s shipping channel clear.

February 2023 Update

The Kawatiri Dredge started dredging the shipping channel on 18 January and finished this swing on 14 February.  During that period, 29,350^m3 were removed.

Note, the dredge is working regularly in the river from its berth out to the dump site past the tipheads at the entrance to the river.  The dredge is restricted in its ability to manoeuvre when dredging.  Boaties are asked to call on VHF radio channel 14 to seek permission and instruction for safe passing.  All recreational and commercial boat users to keep well clear of the dredge to ensure that all river users are kept safe.

 Tiphead repairs complete – update as at 31 March 2023

Work to repair with Eastern Tiphead wall (officially known as the Eastern Westport River Training Wall)has been completed.

The tiphead is a Buller District Council port asset at the mouth of the Buller River. It sustained damage during both the July 2021 and February 2022 weather events.

Rosco Ltd have been carrying out work since mid January to reinforce the tiphead wall and the road on it, with more than 6,000 cubic metres of rock put in place. The project, which was projected to be completed in March, came in on time and within budget.

The repairs were focussed on the first 360 metres of tiphead from the Coates Road/Craddock Drive intersection. The entire tiphead is about a kilometre long.

The work means that if in the future the tiphead and Coates Road (which sits on it) are overtopped by the river in flood, the energy of the water is absorbed by the rock, reducing erosion as the water runs down the back of the wall and out to sea. 

The site has now been ‘demobilised’ meaning contractors have packed up and removed any traffic management signage. The mountain bike track is back in use.

Trees and shrubs that were removed to allow access to the site will be replanted. Buller District Council is working with the Department of Conservation on possibly holding a volunteer replanting day on the site. This will focus on planting hardy, ground-covering species such as tutu, flax, cabbage tree and ngaio to provide food for local birds and compete with the weed species that are already there such as gorse and broom. If the volunteer day doesn’t go ahead, the project will ensure the area is replanted.

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Tiphead repair update (Feb 2023)

More than 3,000 tonnes of rock was placed against the rock wall in the first few weeks of repair to the Eastern Tiphead. Work by Rosco Ltd got underway in mid January 2023, and is set to finish in March. The work will reinforce the Tiphead itself as well as the road on it. The Tiphead was breached and overtopped in the floods, undermining the groyne by removing supporting rocks and base infill. Without this repair work, the road and Tiphead risk being compromised in another severe weather event.

22 December 2022

Contractor appointed for repairs to Westport’s north-eastern tiphead

The contract to repair to the eastern tiphead wall (officially known as the Eastern Westport River Training Wall) has been granted to Rosco Contractors Ltd, following a tender process.

The tiphead is a Buller District Council port asset at the mouth of the Buller River. It sustained damage during both the July 2021 and February 2022 weather events.

Flood waters flowed through the structure and overtopped the inner revetment wall. The overflow undermined the groyne by removing supporting rocks and base infill. Runoff scoured the revetment foundation and ultimately undermined a large section of the revetment wall. Remedial work is required to prevent a major breach of the tiphead.

The repairs are being funded by the National Emergency Management Agency (NEMA) as part of a $17million programme of essential infrastructure repair work in Buller.

Buller District Council Chief Financial Officer Douglas Marshall says the project consists of placing around 3,000m³ of Riprap (rock) on the eastern side of the tiphead road to reinforce the road embankment. The 360m area of embankment will be broken up into four 90m sections.

The trees, bushes and topsoil will be cleared before backfilling with rock. The trees will then be replanted once the rock has been placed.

“In terms of impacts of the work, we recognise that some of the land area required for the work site is used by a local cycle group. They have also recently replanted this area. Unfortunately, the plantings will need to be uplifted, but the area will be replanted and cycle trails reinstated once the tiphead is repaired.

“We also ask local residents to bear with us as there will be about 10 truck trips per day carrying rock to the site for about 25 days. We will try and reduce the impacts on residents as much as possible while we complete these repairs,” says Mr Marshall.

Draft design for the tiphead repairs is complete and Rosco Contractors Ltd will commence work in mid January 2023. Works are expected to be completed in March.

Note, Tiphead repairs will impact on cyclists and pedestrians using paths in the area for about two months from mid January 2023. Roscos will have traffic management in place, but cyclists are warned to be aware of changes to the track layout and large vehicle movements during that time.

26 May 2023 Media release

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Update as at March/April 2023

The historic Reefton landfill was badly damaged in the February 2022 floods. This caused a significant amount of landfill material to be scattered downstream.

NEMA approved more than $1m for the repair of the rock wall which will protect the historic landfill from future Inangahua River inundations. However, this only applies to the areas directly affected by flooding and potentially leaves other parts of the rock wall exposed to future failures. Buller District Council has agreed to an additional $250,000 excl GST to strengthen the rest of the wall to withstand a 1 in a 50-year flood. The contract for this work is expected to be awarded by late April, with construction works taking place between May and June 2023.

The northern bank of the closed Reefton Landfill was scoured away by the Inangahua River during the severe February weather event, causing waste to be swept away.

Major clean-up and enabling works at the historic Reefton Landfill site have been ongoing since February in preparation for the repair of a section of the flood-damaged rock wall that protects the historic landfill site from the river. Buller District Council contractor Rosco’s will continue to maintain the site to ensure it is protected prior to construction getting underway in the coming months.

As at December 2022, a contract to design remedial works required for a section of the flood-damaged rock wall was awarded to WSP NZ.

WSP is working on design work for the rock revetment to re-cap the disturbed landfill and landscape the area.

During 2022, river training work was carried out to reinstate the flood stopbank that protects the Reefton campsite and reserve from flooding from the Inangahua River. 

Council has been monitoring the river and some additional river training is scheduled for April/May 2023 

The Reefton Campground is a community asset. The stop bank protects the reserve and Reefton town.

[Aeration diffusers that deliver oxygen to the aerobic digestion phase of the wastewater treatment process have been replaced.]

Repairs to 3 Waters infrastructure March/April 2023

The Flood Recovery 3 Waters repair work programme is nearing completion. Note, this is separate to the government’s 3 waters reforms.

The efficiency of the storm and wastewater networks was severely compromised following the July 2021 and February 2022 floods. The ‘red’ weather events deposited silts and debris through 60% of the networks in Westport.

• All post-flood CCTV and pipe cleaning works have been completed.
• The final grit clean out for the Westport wastewater treatment plant was carried out in March. The aeration diffusers that deliver oxygen to the aerobic digestion phase of the wastewater treatment process have been replaced.
• All recovery-approved open drain clearing works is complete.
• Reefton’s drinking water reservoir access track requires further repairs. A culvert to redirect the damaging surface water run-off was installed in March but further works on the track are still required over the upcoming months.
• A repair strategy is being worked out for repair of the historic Brick Arch section of the stormwater network running under Brougham/Palmerston Streets. Thus far this work has centred on seeking and achieving access permission from stakeholders such as Kiwirail and Heritage NZ and starting on engineering design.
• Replacement of the final electrical components of Westport’s Wastewater pump stations is close to fully complete. A flowmeter at Pakington Street pump station and two overflow sensors are the final items to closeout.

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Three Waters – Remaining repairs (less than 10% to complete as at September 2022)

• Work is due to start (in early October) on final CCTV inspections of underground pipes. Contractors will be returning to areas that CCTV couldn’t previously access due to suspected pipe blockages.
• Westport Waste Treatment Plant silt/grit clean out of the plant. The third clean out is complete and the fourth is planned for February next year.
• A small number of open drains still require cleaning, these will be completed as the ground dries out into summer.
• Reefton’s drinking water reservoir access track requires further repairs which are currently being planned (to be completed by November 2022).
• Buller District Council (BDC) can complete the Waimangaroa drinking water trunk main replacement once Department of Conservation (DOC) has completed the culvert replacements on Conns Creek Road.
• A repair strategy is being worked out for repair of the historic Brick Arch section of the stormwater network running under Brougham/Palmerston Streets.
• Replacement of the final electrical components on two of Westport’s Wastewater pump stations is complete.

3 Waters – Progress since July 2021 (90% complete as of 31/08/22)
It has taken a full year of flushing, cleaning, and CCTV works to return the stormwater and wastewater networks to pre-flood condition.
Flood silts within the wastewater network also worked their way through the underground network and pump stations to the Westport waste treatment plant. To remain operational, the treatment plant has needed several cleanouts.
Several of Westport’s wastewater pump stations were inundated by flood waters, damaging several critical electrical components. Replacement of parts has been ongoing since July 2021.
Council’s maintenance contractor (Westreef) has been clearing open drains across the region, repairing underground pipes and tomo’s (sinkholes) in the roads arising from damaged pipes.
Waimangaroa water supply’s main trunk line was destroyed in three places along a 1.5km section of access track when culverts were washed out by extremely flooded tributaries. Inangahua and Reefton also required repairs to main trunk lines and access tracks, in the case of Reefton, the work is still ongoing.

What is betterment?

‘Betterment’ projects are those that would benefit from improvement/upgrading/updating whilst carrying out the overall repair programme. Whilst assessing the repair package for 3 Waters, several projects were identified that largely relate to Westport stormwater and wastewater improvements.

Summary of projects to be delivered:

• Upgrading backflow prevention in critical stormwater outfall pipes that drain into both the Buller and Orowaiti Rivers. This will assist in keeping river water out of the stormwater pipes as rivers rise.
• Lifting flood-prone pump station electrics.
• Upgrades to the Westport Waste Treatment Plant to allow it to better manage grit in any future flooding events Westport may face.
• Upgrades to some existing (and addition of some new) critical stormwater assets to better cope with surface flooding and severe weather events in Westport.

Betterment Projects in more detail (as at March/April 2023):

• Lifting flood damaged Wastewater Pump Station electrical cabinets above 1 in 100 year flood height. Council is working towards appointing a contractor.  
• Providing backflow prevention to 5 stormwater outfall locations. Two WaStop valves have been installed and three more are planned over the next 3 months.
• A consultant is being appointed to manage grit and sediment removal and a replacement screen at the Westport wastewater treatment plant.
• A consultant is being appointed to oversee the investigation into an alternative drinking water supply for the town.
• Design for the Coates Steet stormwater upgrade is underway.
• The stormwater reinstatement scope at the Westport Domain changed to the installation of a new sump, completed in March.
• Roebuck Street SW manhole was completed in March.
• Mill Street SW manhole is scheduled for April 2023.

The aim is to help provide ongoing resilience. For example, as well as repairing a flooded pump station electrical cabinet, flood-prone cabinets will be lifted above a 100-year flood level.

You can see our update on Coates Street, which is the first of the betterment projects to proceed.