Central Interceptor Submission

Introduction

1. Having sat as commissioner hearing sewage network discharge applications in various parts of the Auckland region, and having chaired North Shore City Council’s Works and Environment Committee throughout the period when it was required to upgrade, augment and otherwise maintain its sewage network and wastewater treatment plant, I consider myself to be reasonably expert in Auckland sewage operational and consenting issues .

2. This submission relates to Auckland Council District Plan (Auckland City Isthmus Section and Manukau Section), Central Interceptor Scheme – Main Project Works (Western Springs to Mangere Wastewater Treatment Plant).

3. Specifically it relates to both the Notices of Requirement for Designations (Proposed Plan Modification 332 - Isthmus District Plan, Proposed Plan Modification PA58 – Manukau Plan), and also to Applications for Resource Consents (R/LUC/2012/2846–Isthmus Plan and NES consents, PRC40962 – Manukau Plan and NES consents, master consent 40834 for the various regional consents).

4. The pre-amble provided by Watercare describing the Central Interceptor project and associated works states:

Watercare’s statutory objective (obligation) under the Local Government (Auckland Council) Act 2009 is (amongst other things) to:
“Manage its operations efficiently with a view to keeping the overall costs of water supply and wastewater service to its customers (collectively) at the minimum levels consistent with the effective conduct of its undertakings and the maintenance of the long-term integrity of its assets.”
The specific objectives for the proposed works are as follows:
* To provide additional sewer network capacity for growth and development across the Auckland Isthmus; and
* To reduce existing wastewater overflows from the combined sewer system into urban streams and the Waitemata Harbour.
A further objective is to minimise construction and operating costs, whilst having regard to the sustainable management of resources.

My submissions, in part, relate to this latter objective. I submit that the Central Interceptor project is significantly more expensive to construct than alternatives, and that because it is an approach that does not lend itself to staged implementation, minimal environmental benefits will be delivered until the whole project is complete. I enlarge upon these submissions below.

5. The NZ Herald public notice relating to both the designations required and the resource consents sought states:

....The applications for various regional resource consents for the whole of the project cover the area described above and include earthworks, tree removals, the removal of a structure on public open space and construction of network utilities, the diversion and discharge of stormwater from impervious surfaces (during construction and permanent), disturbance of contaminated sites, groundwater take and diversion, air discharges, and works and discharges to the Coastal Marine Area (CMA)....

My further submissions relate specifically to the last of this suite of consents – namely the consents for discharges to the Coastal Marine Area (CMA). In summary, my contention is that Watercare has a legal obligation to seek regionwide discharge consents for its whole network – not just for the part of the network described as the Central Interceptor. Officials and commissioners need to be able to consider the operations and effects, now and into the future, of the whole of Watercare’s sewage network (because they are interconnected) including those parts that operate as combined stormwater sewers. The present application seeks consents for discharges from just one part of the network, leaving discharges for other parts of the network unconsented – despite the RMA requiring consents for all discharges to the CMA.

I enlarge upon this submission below.

NSCC Storage Tank approach

6. Large centralised sewage systems are typical in New Zealand’s urban environment. These are expensive to build and - as environmental expectations increase – alarmingly expensive to maintain. North Shore City Council discovered this when community pressure obliged Council to fix its network and prevent wet weather overflows from sewer pipes which were closing local beaches. While I was Chair of North Shore City Council’s Works and Environment Ctte officers investigated sewer augmentation options not unlike Watercare’s proposed Central Interceptor Tunnel, but rejected them on the basis of cost. Instead North Shore City Council adopted a dual programme to reduce stormwater infiltration into its sewer network, and to build underground storage tanks which collected the most damaging and frequent overflows. When the storm has passed and the sewer network has drained sufficiently, the collected wastewater that would otherwise have polluted beaches, can be pumped to the treatment plant. The benefits of this approach were many. It was not capital intensive and could be funded from rates revenue. It was an approach that could be staged – environmental benefits were immediate when the first overflow storage tank was constructed. It allowed for a de-centralised approach to network management – which lent itself to computer control in response to concentrated weather events.

7. Watercare’s EIA for the Central Interceptor notes the constraints on its network that the discharge consents for its Mangere Waste Treatment Plant impose. These constraints effectively constrict the ability of Mangere WWTP to cope with increased inflows during wet weather events. To meet Watercare’s objective (quoted from above) “to reduce existing wastewater overflows from the combined sewer system into urban streams and the Waitemata Harbour” it is more appropriate to provide for enhanced storage of wastewater that would otherwise discharge, than it is to augment flows to Mangere – because of its inability to cope with increased flows. The North Shore City Council exemplar of distributed storage tanks provides that sort of storage capacity, whereas the Central Interceptor approach (given the limited storage capacity provided in the pipes) does not.

8. While I am not familiar with the exact lay of the land where discharges currently occur on the Auckland Isthmus, it is my understanding that locations exist near major discharge points where underground storage tanks could be located. Based on my North Shore experience and knowledge of construction costs of storage there, I believe there would be savings with such an approach on the Auckland Isthmus. In addition, a key benefit with NSCC’s incrementally built storage tank system, is that environmental benefits are delivered as soon as the first tank is in place and operational. The Central Interceptor will not produce benefits from reduced discharges until it is virtually complete. This is a typical negative of centralised infrastructure. The separate storage tank approach delivers an intelligent de-centralised system which can be controlled remotely to respond to the kind of localised weather-bomb type events that can very quickly overwhelm traditional sewage systems. While I understand that Watercare does not need to show that it has considered every alternative, in my opinion its lack of consideration of the NSCC approach to the problem is not in keeping with Watercare’s stated objectives and is not consistent with the overall purpose of the RMA.

Network Discharge Consent Process

9. Watercare’s EIA for the Central Interceptor project states:

Once the Central Interceptor scheme is completed, the scheme will reduce the average annual wastewater overflow volumes discharged from this network by approximately 80%. This equates broadly to network overflow discharges in 6 – 12 storm events in an average year, down from the many hundreds of events that currently occur....

It is important to note that this means that there will still be discharges of untreated sewage from “this network” even after the Central Interceptor works are completed. The same – but different – outcome was anticipated in the case of NSCC’s sewage network infrastructure improvements which were delivered at significant ratepayer cost. In that case residents were given the option of “no overflows in a typical year” – at a cost of almost $1 billion, “2 to 4 overflows in a typical year” – at a cost of around $400 million, and so on. Affordability was a key issue. So too were considerations as to which overflows would be prioritised. Because it was not possible to contain all overflows in every storm event.

10. I sat as one of the commissioners who considered NSCC’s wastewater network discharge consent application. The critical information was drawn from a computer model of the entire network. This predicted the magnitude of discharges from different discharge points, under different storm events. The model allowed engineers to simulate the environmental effects of different improvement scenarios. This information was central to the decision-making of commissioners. It enabled them to decide conditions of consent for the upgrade and operation of the network – considering environmental effects of discharges from the whole network – alongside a committed budget and program of works for the network.

11. The Central Interceptor is one possible upgrade for one section of the sewage network on Auckland’s Isthmus. Implicitly it deals with some of the existing overflow points, and at the same time will allow overflows (the 20% volumes that will discharge, 6 to 12 times a year) from other overflow points. Other sections of the Auckland Isthmus network will continue to discharge as they do now. But commissioners will not be in a position to decide or recommend operating conditions that meet whole of network concerns. They will be required to take Watercare’s word. This is not a satisfactory situation. Watercare mentions the possibility of a “Northern Interceptor” which could collect overflows and sewage flows and direct them to the Rosedale WWTP. I am aware that there is also a need for a CBD Interceptor that would collect the discharges that presently flow untreated into the Viaduct and other parts of Auckland’s developing waterfront putting sporting and other activities at risk (for example Triathlon events).

12. The Watercare Central Interceptor project resource consent process is fundamentally flawed because commissioners and officials considering the application will not be able to consider the function of the network as a whole. Nor will they be able to assess the Central Interceptor proposal weighed against other projects or proposals that address discharges in other parts of the Auckland Isthmus sewer network. The application should not be permitted to proceed to hearing in its present form. There is insufficient information for commissioners to process the application that is in accord with the purpose of the RMA.