In 1986, a wastewater collection, treatment, and disposal system was established in Seacliff to serve the local community. The system operated smoothly until 1994 when a minor portion of the disposal area experienced seaward slumping.
Dr Barry Douglas, a geologist, was appointed to assess the site and propose remedial measures and surveillance recommendations. Since the remedial measures were implemented, the system has operated effectively.
New treatment system
In September 2019 the DCC applied to the Otago Regional Council for a new consent to discharge treated wastewater locally, as the existing consent was expiring.
Upgrade work includes new septic tanks and dosing tank, refurbished sand filters and new pipework, a new treated wastewater storage or dosing tank and other improvements designed to accommodate future demands.
A map showing what is being constructed is attached to the end of this letter. There are some things worth noting in the map:
- Initial wastewater treatment facilities (dark red squares).
- Paddocks for wastewater irrigation with plans for tree and shrub planting (yellow areas).
- Groundwater monitoring wells (indicated by "X"s).
- A reserve area for wastewater disposal (light red area).
- Swales to divert stormwater away from irrigation fields.
Land stability
We recognise the historic land stability issues along the coastal area from Warrington to the outskirts of Karitane. In response to this concern, we have undertaken several measures:
- Seeking advice from respected national and international experts.
- Expanding the area for wastewater disposal.
- Diverting rainwater/stormwater away from irrigation areas.
- Implementing extensive planting to enhance soil water absorption.
- Installing a monitoring system for early land stability risk detection.
- Constructing a reserve disposal system for contingency.
When the Otago Regional Council assessed the application in 2021, its Natural Hazards Unit noted “that the revised disposal plan seems a pragmatic approach given the site constraints and seeks to minimise any effect on land instability. Effects on land stability and erosion is considered to be isolated and no more than minor.”
Since then, we have received the new consent with an expectation that the new treatment system would be built and working by the end of September 2023. Due to delays in awarding a construction contract, DCC has started trucking of treated wastewater to Dunedin City to ensure uninterrupted service and environmental responsibility during the upgrade. The new system is now expected to be built by mid-2024.
Checking the sewers at Seacliff
Due to concerns of stormwater infiltration, we have recently used cameras to investigate the condition of the foul sewer network in Seacliff and are currently reviewing this footage. If any further investigation or repair work is found to be necessary, either in the street or within private property, we will communicate directly with any residents that may be affected by this.
Kilgour Street watermain renewal
We also plan to replace the water supply pipe on Kilgour Street (from the Palmer Street intersection to the entrance to the treatment plant). The current pipeline is too small for the existing number of properties and we need to add an extra connection to the treatment plant so equipment can be washed down. There has been some recent work to repair several leaks in the area. This renewal will also help to guarantee a more reliable service.
The methodology of this work is still to be confirmed; however, this work will involve laying a new watermain within the formed roadway and ensuring each property has their own compliant shutoff at the boundary. The DCC and our contractor will work with you to help minimise disruption where possible throughout this work.