Objectors to a stormwater & sewage holding tank to be built under expensive houses along the St Marys Bay ridge overlooking the Westhaven marina had their complaints rejected by a hearing panel last Friday, but a council committee will be back to hear them again this Friday.
Auckland Council’s regulatory committee has called a special meeting to hear objections, and to rule on them in a confidential session the same day.
As with the original hearing decision, the recommendation before the committee is to proceed with the project.
At stake is a $30 million-plus project designed to reduce – close to zero – the frequency of sewage spills into the Waitemata Harbour.
At stake from the property owners’ points of view are:
- Loss of property value through potential development restriction
- Extreme, unavoidable stench through vents
- Concerns about cliff stability
- Construction impacts, including the fear that the foundations of old houses along the route will be disturbed, and
On top of those questions is the issue of separation of storm- & wastewater – required of property owners in this area for the last 20 years when renovating, altering or redeveloping their properties, only to become mixed again at the gate.
Mr Hill commented on separation in the panel decision: “While we might accept the sincerity of the applicant’s (the council’s) assurance that this proposal is a stepping stone to that eventual outcome, the political history of this issue, as amply demonstrated by the submitters, gives no such assurance.”
Against the council desire to move forward with this project now, submitters also suggested further review, including alternatives, benefits & costs, ought to be undertaken.
However, Mr Hill said the panel had no lawful basis for requiring the application to be suspended for further analysis.
The objective of healthy waters
Auckland Council renamed & refocused its stormwater department, calling it the Healthy Waters department (Wai Ora – Healthy Waterways), in a bid to – at long last – rid the western isthmus in particular of the extremely frequent overflows arising when a deluge of rain hits the dual-purpose sewage & stormwater drains.
For years, local body politicians have fallen short of meeting the dirty-water challenge, limiting the budget and thereby ensuring the certainty of continuing spills by not separating sewage from stormwater.
But councils are now required to abide by the 2014 national policy statement for freshwater management in full by the end of 2025.
In Auckland, the Western Isthmus Water Quality Improvement Work Programme is the largest workstream funded through the targeted rate. Its aim is to progressively reduce overflows into the Waitemata Harbour from hundreds of events to 6 or fewer/outfall/year.
Auckland Council figured, at the end of 2015, it couldn’t meet the national policy statement conditions then, and set about establishing programmes last year so it could meet the policy.
Analysing the watersheds
The council has divided Auckland into 10 watersheds, where water drains to a stream, or ultimately to the harbour or open sea, and has drawn up this staged approach:
- Mapping the current state & key issues for each watershed
- Determining how to achieve the objectives & consulting the community, and
- Developing action plans to meet objectives, limits & targets set in collaboration with key stakeholders.
According to the outline on the council website, the third of those stages should be reached by 2020.
The hearing on the St Marys Bay project was held in September, with a final day in late October, and the hearing panel issued its decision on Friday 9 November. The panel was chaired by David Hill with panellists Mark Farnsworth, Dr Sharon De Luca & Nigel Mark-Brown.
Part of the wider western isthmus programme
The project is part of the wider St Marys Bay improvement programme which aims to improve water quality within St Marys Bay. It’s also part of the western isthmus water quality improvement programme for the wider combined sewer network catchment area, and it’s been designed to integrate with all potential long-term options to improve the network without constraining finalisation of a preferred solution.
It involves reconfiguring the Healthy Waters stormwater network, which is also used by the council-controlled Watercare Services Ltd as a means of safely conveying overflow discharges from 5 engineered overflow points in the combined sewer network, returning these overflows back into Watercare’s branch 5 sewer for treatment at the Mangere wastewater treatment plant when there is capacity.
Any residual combined sewer overflow would be discharged into the Waitemata Harbour via a new, longer marine pipeline that will replace the existing failed outfall at Masefield Beach, which would be removed.
The reconfigured network would enable combined sewer overflows to be captured & stored within the pipeline and returned to the sewer when it has capacity, for subsequent treatment at Mangere. As Mr Hill noted in the hearing decision: “This will significantly reduce the number of combined sewer overflows occurring from approximately an average of 206/year (into St Marys Bay & Masefield Beach) to approximately an average of 20/year. In addition, the replacement outfall will extend further into the Waitemata Harbour, such that when overflows do occur during larger rainfall events this will enable better dilution & dispersion.”
Additional information provided at the hearing indicated that the Masefield Beach outfall “currently discharges combined sewer overflows onto Masefield Beach approximately an average of 107 overflows/year”; and that the expected results would reduce the estimated current average annual overflow discharge volume from this part of the network to the harbour from 101,800mᶟ to 35,000mᶟ, and the proportionate contribution from domestic wastewater in those volumes from 18,300mᶟ to 700mᶟ”.
The project requires:
- a 1km conveyance & storage pipeline (1.8m internal diameter, about 2500mᶟ capacity) extending from New St to Pt Erin Park, underground & beneath residential properties, recreation areas & road reserve, with an invert depth ranging between 5m and up to 22m deep
- weir structures, pump stations & odour control units in Pt Erin Park & St Marys Rd Park
- 4 (subsequently reduced to 3) air exchange poles, 8-10m high, within the road reserve on New St & London St
- construction of shafts in Pt Erin Park (8m deep), St Marys Rd Park (9m diameter by 8m deep) and the New St/London St intersection (5m diameter by 24m deep)
- a new 750mm internal diameter gravity pipeline along Sarsfield & Curran Sts connecting engineered overflow points 194 & 196 directly to the Pt Erin Park pump station
- installation of a new 500m long by 150mm internal diameter rising main between Pt Erin Park & Sarsfield St, connecting to Watercare’s branch 5 sewer
- connections to the new conveyance & storage pipeline from 5 engineered overflow points (points 194 & 196 (Sarsfield St), 172 (London St), 180 (Hackett St) & 1020 (New St)) – with point 180 remaining operational
- construction of a new 450m by 1.4m internal diameter marine outfall pipeline with diffusers in the coastal management area off Masefield Beach, and
- removal of the existing failed Masefield Beach 300mm outfall pipeline.
The panel concluded that, while separation is referred to, this would not be a wastewater facility because the volumes of wastewater overflow would be low.
The panel also concluded that the air discharge from the storage tank (distinct from a pipeline where the contents are continuously flushed away) would pass the required odour standard.
Experienced civil engineer Ross Thurlow proffered an alternative to eliminate the tunnelled detention tank & above-ground ventilation poles & electrically driven ventilators. But the panel concluded that his option of an odour ventilation pipe inside an enlarged pipe tunnel with discharge at Pt Erin would require too long a tunnel and would not be viable.
On the issue of land settlement once the tunnel has been put in place, the predicted settlement effects were very low ad the panel accepted that any adverse effects would be detected early to allow appropriate mitigation measures to be put in place.
The panel also accepted that neither the shaft nor tunnel construction would cause groundwater changes that would adversely affect cliff stability. Overall, on stability, the panel said: “We find the investigations sufficiently detailed to allow reasonable predictions of settlement & stability effects. These can & will be further managed through consent conditions, including implementation of a groundwater & settlement monitoring & contingency plan and a construction noise & vibration plan to measure actual behaviours of the ground in terms of groundwater levels, vibration & settlement that will allow early detection and, if necessary, implementation of mitigation measures should the works cause unexpected effects that could affect existing buildings, utilities & roads, or cliff stability.”
The final paragraph of the decision sums up the resource management issues: “While the proposed development does not achieve the outcome sought by many submitters specific to the network discharges management solution advanced in the application, it is a significant improvement over the existing coastal marine discharge situation and, we were assured, is not the end of the matter as far as council (Healthy Waters) is concerned. We have accepted that assurance and, in that context, agree that it represents an appropriate sustainable management response to the identified problem and ‘promotes’ the purpose & principles of part 2 of the Resource Management Act.”
The next round, on Friday, takes the council into more complicated territory, away from the project itself and into the realm of values.
9 November 2018: Hearing decision
Auckland Council, Looking after our waterways
Regulatory committee agenda, 16 November 2018
7, Objections to St Marys Bay & Masefield Beach improvement project
Maps showing project overview & objectors’ properties
Options analysis for location of new infrastructure
Examples of formal notices sent to residents under the Local Government Act 2002
Copies of all objections received
Record of communications
Engineering assessments & review of development controls for each property
C1, Deliberations on objections to St Mary’s Bay & Masefield Beach improvement project (in confidential agenda)
Attribution: Hearing documents & decision, committee agenda.