In 2018 Auckland Council (Healthy Waters) was granted a resource consent to build a large drainage tunnel through the foot of St Mary’s Bay as part of a project to prevent sewage spills from a single and ancient pipe which regularly overflowed after even moderately heavy rainfall. The SMBA and others appealed that consent. The St Mary’s Bay Association (and others), guided by expert advice, negotiated revised conditions for the consent with Healthy Waters. Once those were agreed, the appeals were withdrawn. The Environment Court recorded that settlement in a consent order made on 25 November 2019.
As is frequently the case, this outcome was a compromise by both sides. The Association, adopting the expert advice, decided that it was unlikely to succeed on its preferred options (having the project dropped or the route changed). So it concentrated instead on negotiating changes to the conditions of the resource consent to minimise risks to properties and adverse effects on the environment.
The changes to the conditions for the tunnel project will work hand in glove with the agreement reached earlier in 2019 to separate the existing combined wastewater and stormwater system in St Mary’s Bay and Herne Bay. Together the two projects will mean that in almost all weather only stormwater will be discharged into the harbour. This will bring about a very substantial improvement to water quality in St Mary’s Bay/Westhaven and the Herne Bay beaches. The commitment to separate was formalised in an agreement signed in November 2019.
For many years there has been a limited amount of separation within properties, as new builds and major renovations have been required to install two separate sewerage pipes – one for stormwater and one for wastewater – to the property boundary, and in more recent time some form of sump or holding tank. However, as the separated pipes on these properties are separated only to the road frontage the stormwater and sewage still flow into a single pipe where sewage becomes mixed with stormwater. After any significant rainfall the system cannot cope with the extra stormwater and the contents are discharged into the Waitemata Harbour.
We still await a start date for separation.
The key changes to the original drainage tunnel design are:
- The level of the tunnel is being lowered. Importantly, this will minimise instability concerns for properties above, and will allow above ground structures in reserve areas to be reduced or removed. The pump station at Pt Erin will be landscaped to surrounding ground level and there will no longer be any above-ground structures in the grassed area at St Mary’s Park;
- Odour control poles planned for London Street have been removed and odour control/air vent poles in St Mary’s Park and Pt Erin Park will be relocated to minimise visual effects;
- The pump station in Pt Erin Park is to be altered to prevent build-up of water in the tunnel (which will no longer be used for medium/long-term storage);
- An old stormwater pipe running down from Hackett Street, under properties in lower St Mary’s Road, is to be re-lined to avoid risk of leakage and erosion under properties; and
- The head of the outfall pipe into the harbour is being modified to improve dispersal of stormwater and any overflows of wastewater.
In addition to these design changes, various conditions provide improved checks on compliance with the conditions. As part of this, a monitoring group (the St Mary’s Bay Project Liaison Group or SMB-PLG), comprising representatives of all key stakeholders, has been established. This will allow community oversight of the project throughout the construction period. It is too early to say whether we will need to re-engage our expert on any of the design matters, or any other experts for that matter, but we will keep the fighting fund in place until it is clear that we no longer have a need for it.
Work on the tunnel started in January 2020. Not unsurprisingly there were some early teething troubles, but these were worked through and solutions were found. These included getting transport management plans in place, particularly in the confined spaces in lower St Mary’s road. After an initial set-up period in December/January, construction work commenced in January. The first steps were to excavate large chambers in Pt Erin Park and St Mary’s Park, to allow for the tunnelling machine to be put in place.
A separate but related project is underway in Hackett Street. This involves construction of a replacement inspection chamber for the intersection of wastewater and stormwater pipes at that point. Hackett Street was closed to through traffic in January to allow this work to take place and the Shelly Beach Rd end of Hackett St has been opened to two-way traffic for residents on that side of the Hackett St closure, for the duration of the closure.
In the meantime, design work is continuing, with community members of the SMB-PLG playing a part. Dilapidation surveys of properties potentially affected by construction of the tunnel have been undertaken. The SMBA is not party to those surveys, other than in a very general sense through reports to the SMB-PLG.