Client name:
Auckland Council – Healthy Waters
Site:
Mayfair Crescent / Ramsgate Terrace, Mairangi Bay
Project overview:
To provide professional services for the investigation and design for Mayfair Crescent Stormwater renewals. This project is to address growth in this area and catchment. Our work included construction supervision, stormwater renewal and network extensions. .
Goal:
- Increased Level of Service
- Enabling growth and development
The value that Thomas Consultants team added:
Due to an upcoming Auckland Transport pavement rehabilitation project, we needed to expedite the stormwater upgrade. This was crucial to avoid disrupting their scheduled work and prevent unnecessary excavation of their newly paved area.
During the project, we encountered a gas main which was directly connected to the existing public stormwater main and cesspit lead.
The agreed-upon solution was:
- The gas main to be re-aligned by Vector, moving it 200mm upwards from its original position.
- We cut the existing pipeline to the collar and replace the section with a DN300mm uPVC SN16 pipe, secured with two shear bands.
- The cesspit lead to be relocated further upstream and connected to a stormwater manhole (SWMH).
Another challenge we faced at this site was the significant amount of groundwater encountered. The contractor installed three pumps discharging into a stormwater cesspit and provided stormwater protection around the cesspit using geotextile cloth and silt socks. However, the stormwater protection proved inadequate, as evidenced by the condition of the downstream watercourse (a sensitive stream) shown in the picture below.
We also recommended that the contractor deploy a Lamella clarifier (with HIAB) to the site (image below left). This unit features automatic flocculant dosing and requires bi-weekly cleaning by a sucker truck. The Lamella effectively removes solid particles and at the next site visit, the water was significantly clearer, as seen in the below photo (right).
Services provided:
Key staff members for project were:
Jason Lee
Partner we worked with
Fulton Hogan.
Outcome
The stormwater infrastructure is now able to handle higher volumes of stormwater, reducing the risk of flooding and ensuring better drainage. This also enables future development and expansion in the area by providing a reliable and efficient stormwater system.
Project completion:
August 2024
