SWDC Water Supplies
Overview, history, challenges, high level investment needs: July 2024
Agenda: 1) Refresher/overview of Wellington Water, our trusted advisor model, and how we are funded 2) Council's community outcomes and wellbeings, how Wellington Water's service goals align, and how these relate to the water supply strategy 3) Brief history of SWDC drinking water supplies 4) Timeline of events, and the changing regulatory environment 5) Wellington Water ~4 years in, and what we have learnt 6) Summary of key investment needs for the region 7) High level options for Memorial Park, and alignment with SWDC outcomes and WWL service goals
Wellington Water, our trusted advisor model, and how we are funded
Wellington Water's role - SWDC's trusted advisor
Council's community outcomes and wellbeings, how Wellington Water's service goals align, and how these relate to the strategy
Council community outcomes and wellbeings (Healthy, Safe, Resilient, Economic wellbeing, Environmental wellbeing)
Safe and Healthy Water
Key considerations/principles that relate to these and inform the water supply strategy include: -Compliance with drinking water standards (as a minimum) -Providing a network that meets the Code of Practice for Firefighting Water Supplies -Condition and performance of assets to minimise safety risks -Applying the six principles of safe drinking water, being: Principle 1: A high standard of care must be embraced Principle 2: Protection of source water is of paramount importance Principle 3: Maintain multiple barriers against contamination Principle 4: Change precedes contamination Principle 5: Suppliers must own the safety of drinking water Principle 6: Apply a preventive risk management approach
Respectful of the Environment
Key considerations/principles that relate to these and inform the water supply strategy include: -Minimising water loss through Prevention (asset renewals, pressure management, network calming); Awareness (Supply zone and District Meter Area management, data consistency, flow analysis); Location (active leakage control, acoustic correlation, non-acoustic methods); Repair (Cut-out and replace or clamp, no-dig methods) -Community education and engagement -Compliance with consents -Minimising disruption for the community
Resilient networks support the economy
Key considerations/principles that relate to these and inform the water supply strategy include: -Building in operational resilience -Providing duty/standby facilities -Providing multiple routes/directions of supply where possible -Being mindful of the burden of cost to the community (rate payers)
Brief history of SWDC drinking water supplies:
Featherston
Original water supply network started in the early 1900s.
Supply link from Abbots Creek flowing under gravity into the centre of town.
Prior to 1999 the Greytown and Featherston supplies were separate water supplies.
Abbotts Creek
Raw water intake, providing an untreated supply of water to Featherston prior to 1960s.
Low head (pressure) supply, significantly limited during summer months.
Boar Bush Reservoir
Concrete storage tank constructed in 1954 together with a chlorine contact tank. Originally built to store surface water supplied from the Boar Bush Gully stream, and allow treatment with chlorine only.
The only storage of treated drinking water on the Featherston side of the Tauwharenikau river.
Provides ~6-8hrs storage for Featherston at current average day demand.
Boar Bush Gully Dam
Built in the 1960’s to provide additional untreated water storage.
Water quality from the dam is poor. Regularly experiences algal blooms (see additional photo above) - toxin risk and taste and odour issues.
Unsuitable for use without significant additional treatment. Capacity insufficient for Featherston supply.
The dam requires a comprehensive dam safety management system to be implemented to comply with regulations coming into effect in 2024.
Dam fully isolated from the treated water reservoir to ensure no possibility of contamination of treated water from the dam (passing valves etc.).
Taits Creek
Weir and pipeline constructed in 1980's connecting to the Boar Bush Reservoir, supplying raw (untreated) water.
Last used in 1999.
Poor access. Significant washouts occurred in 2018 not repaired for cost/benefit reasons.
Fully isolated from supply to ensure no possibility of contamination.
Waiohine Water Treatment Plant to Taits Creek
Pipeline constructed in 1999 from Waiohine WTP to supply Featherston. Prior to 1999, the Waiohine WTP supplied Greytown only.
Waiohine Water Treatment Plant
Site originally developed in the 1940s when a weir was installed at Bassets Creek to supply a raw (untreated) storage pond.
In 1956 a reservoir was constructed (the Greytown reservoir), allowing treatment using chlorine and supply to Greytown only.
In the 1960s a second pond was constructed. A pump station was also built on the river terrace to supply from the water race.
In 1999 an Ultrafiltration treatment plant upgrade was completed with the intention of serving both Featherston and Greytown.
Ongoing difficulties providing consistent water quality from the UF plant resulted in the establishment of a shallow bore in Memorial Park, and by 2005 Memorial Park became the main source for Greytown.
The Waiohine WTP connection to Greytown allows a backup source of supply to Greytown.
Due to continued difficulties supplying water from the UF plant, in 2015 three bores were developed beside the Waiohine River replacing the river pumps. An extension was built on the WTP building to house new Ultraviolet treatment units and the ultrafiltration plant was mothballed (2017).
Fourth bore drilled 2019-2020 (commissioned 2021) to assist with flow limitations caused by turbidity in the existing bores during low river flows or when the river is in flood.
One pond was converted to treated water storage using a bladder. Sufficient for ~3 days for both Featherston and Greytown at average demand.
Maximum output capacity of the four bores operating together is theoretically sufficient to supply the average total demand for Featherston and Greytown. However is insufficient for supply to both towns in peak periods. The bores also experience turbidity issues that reduce output capacity significantly when river levels are low or the river is in flood.
Hydraulic constraints between WTP and Greytown reduces supply pressure during high flow/daytime demand periods, including in the event of a fire. Driving head is insufficient - so additional supply source is required in Greytown (provided by the Memorial Park treatment plant).
Featherston Groundwater Investigations
In 2012 Groundwater Investigations adjacent on the Featherston side of the Tauwharenikau River were completed and concluded that 'the groundwater potential in this area is poor'.
Greytown
Original supply started in early 1900's from Moroa water race, and wells throughout Greytown.
Supplied from Bassets creek in the 1940s before river pumps were installed in the 1960s to supply water from the Waiohine treatment plant.
Bassets Creek
Historic source installed in the 1940's from a spring fed stream.
Pipeline installed to a storage pond at the current Waiohine WTP site.
Memorial Park Water Treatment Plant
Bore originally drilled in Memorial Park to supplement the supply from Waiohine WTP. However due to Waiohine supply reliability issues is understood to have become the primary supply for Greytown by around 2005.
Until 2019 was treated using chlorine only, and used soda-ash for pH correction (corrosion protection).
Chemical storage and dosing via a room attached to the Memorial Park swimming pool.
UV installed by Wellington Water in November/December 2019 under urgency.
Woodside Rd and Humphries Street Control Valve
A 300mm dia. pipeline (2016-2017) links Waiohine WTP to Greytown via Woodside Rd and Humphries Street, where it connects to a smaller pipeline along Main Street (2000).
Pressure in Greytown is controlled using a valve at Humphries Street. Valve closes when the Memorial Park bore is running to maintain system pressure and flow during high demand periods.
When demand in Greytown is too low the Memorial Park bore stops. System pressure then drops and the valve opens allowing supply from the Waiohine WTP.
Martinborough
Supplied from the Huangarua River in 1955. Supply needed frequent maintenance to ensure sufficient flow to town.
River water was pumped up to reservoirs on Hinakura Rd. Water was then treated using chlorine only.
Network expanded in the 1980's primarily to support growth of vineyards.
Supplied from bores located off the end of New York St West, in Herricks Farm, since the 1990s.
Huangarua River Intake
Originally developed in 1955
The source is an emergency/backup supply only, and can supply to the Martinborough storage reservoirs.
2019 Contamination Incidents
E.coli (indicator of faecal contamination) detected in the water supply in January 2019. Boil water notice remained in place until late February 2019.
Wellington Water provided assistance to implement a risk based approach to the incident and determine the most probable cause. Malfunction of the UV plant identified as most probable cause.
Remedial works completed under urgency, and network flushed prior to lifting the boil water notice.
Further boil water notice was issued in April 2019 remaining in place until May 2019. Various improvements made within the distribution network, but probable cause unable to be confirmed.
Council decision made to chlorinate supply using a single lower manganese bore pending construction of a manganese reduction plant that would allow permanent chlorination of the network without the risk of water discoloration.
Martinborough Water Treatment Plant
Three bores developed in Herricks Farm in the 1990s. Additional bore developed in 2012.
Agreement with the property owner for the supply and a pipeline connecting the bores to the network. As part of agreement stockwater is supplied from the bores.
Bores and treatment plant located within stock grazing areas.
Access is poor.
Ultraviolet disinfection system installed in 2012, together with a chlorine disinfection system. However chlorine was not used prior to 2019 due to manganese content of the water which reacts with chlorine causing significant discolouration (turns water black).
Manganese Reduction Plant
Built 2020 on leased land, to allow treatment of supply with chlorine without black water issues. Operates in combination with the WTP.
Martinborough Reservoirs
2 concrete reservoirs built in 1955 and 1964 with capacity 860m³ each, and 2 timber tanks built in 1999 and 2004 with capacity 980m³ each.
Approximately 3-4 days average water demand.
Pirinoa
8 connections to the water supply including the store, Community Hall/rugby club and school.
Originally the network was fed from a farm spring.
In 2017 after large number of leaks and contamination incidents network was renewed in the road corridor. All connections now metered.
Pirinoa Water Treatment Plant
Built in 1995 when the drinking water standards were created, and the school was worried about compliance.
Single shallow bore supplies the treatment plant which uses a combination of Ozone treatment, sand filtration, cartridge filtration, UV and chlorine.
UV with two stages of cartridge filtration were installed by Wellington Water in 2019 with an automated chlorine dosing system.
Treated water pumped into the Pirinoa supply.
Timeline of events and the changing regulatory environment (for context)
Jan - Mar 2019
Martinborough Water Supply Contamination incidents. Wellington Water assistance provided. Key outcome is progression of Manganese Reduction Plant to allow permanent chlorination of supply.
1st Oct 2019
SWDC becomes shareholder of Wellington Water
Oct - Nov 2019
Rapid process audits/assessments of all treatment plants completed against DWSNZ 2005 (2018). Numerous issues with existing treatment plant assets identified across all locations. Most significant issue/risk confirmed as Memorial Park WTP due to lack of Protozoa barrier. Non-compliant with urgent risk reduction measures required
Nov 2019
Council approves installing Ultraviolet treatment in temporary arrangement at Memorial Park under urgency, and then progressing with upgrade of treatment plant to achieve compliance
Dec 2019
UV installed in temporary containerised arrangement at the Memorial Park Water Treatment Plant
Feb 2020
Featherston Boil Water Notice - required due to stream washout damaging supply pipeline following ex-tropical cyclone. Urgent pipeline realignment completed
Aug 2020
Water Services Act 2020 passed, establishing the Water Services Regulator - Taumata Arowai. Increases scrutiny and regulatory accountability for Council assets to meet the requirement of the drinking water standards
Late 2020
'Blue water' (cuprosolvency) complaints in Featherston and Greytown due to poor condition and performance of pH correction systems at both the Waiohine and Memorial Park Water Treatment Plants. Sodium hydroxide dosing systems installed in temporary containerised arrangements at both Waiohine WTP and Memorial Park WTP to address the issue.
Jan/Feb 2021
Fourth bore commissioned at Waiohine Water Treatment Plant (supplies Featherston and Greytown when Memorial Park is offline). Significantly improves operational resilience for treatment plant particularly when river levels are low. Despite the new bore, ongoing reliability issues continue due to lightning strikes, power supply reliability, and vulnerability to poor weather conditions
Feb 2021
Martinborough Manganese Reduction Plant construction completed, constructed on leased land. Allows permanent chlorination of Martinborough water supply without 'black water'.
Oct 2021
Water Services Act 2021 passed. Requires Water Safety Plans and Source Water Risk Management Plans (SWRMPs) to be prepared
Feb 2022
Boar Bush reservoir contaminated due to surface flooding from ex-tropical cyclone Dovi and poor condition of reservoir and contact tank. Chlorine contact tank demolished, reservoir spot repairs and site drainage improvements implemented to reduce the risk of future occurrence.
May 2022
Waiohine Water Treatment Plant treated water reservoir (bladder) commissioned. Significantly improves resilience of supply of safe drinking water to Featherston (and Greytown during low flow periods when Memorial Park is offline). Allows continuation of supply while Waiohine water treatment plant is offline for maintenance or other unforeseen issues.
Mid 2022
Taumata Arowai issues new drinking water standards and rules. Requires SWRMPs to be submitted by November 2022
Nov 2022
SWRMPs completed and submitted to Taumata Arowai. Work confirms that upgrades required at Memorial Park, Martinborough, and Waiohine WTP's to achieve compliance (compliance cannot be demonstrated for these treatment plants currently).
Late 2022
Planning for completion of Memorial Park treatment plant upgrade identifies significant risks for commissioning including inadequate system pressure and insufficient firefighting flows when Memorial Park is offline. Additional bore proposed by project team as pragmatic means of mitigating risk and increasing system resilience. Preferred location in car parking/vehicular area not endorsed due to planned sports pavilion extension. Potential location in grassed area within Memorial Park baths identified.
Jun 2023
Hydraulic models developed for SWDC supplies
Jul 2023
Memorial Park hearing for additional bore proposal. Council decision to not endorse proceeding with the bore within the swimming pool grassed area and investigate and assess alternative locations within Greytown.
Wellington Water ~5 years in, and what we have learnt
Summary of investment needs/high level water supply strategy for the region
Key investment needs include (but are not limited to):
- Memorial Park water treatment plant upgrade or replacement
- Martinborough water treatment plant upgrade (including run to waste system)
- Waiohine water treatment plant permanent soda ash replacement system
- Boar Bush reservoir replacement
- Tauwharenikau river crossing realignment
- Water supply network renewals and upgrades
We prioritise these improvements based on the risk to the service goals through not progressing these projects.
Firefighting supply risk when Memorial Park offline
High level options and alignment with SWDC and WWL outcomes
