Wilkins Road Wastewater Pumping Station

Scope

• Sheet piled cofferdam (including 2 staged waler beam) and significant dewatering
• Construction of new pump station with in-situ concrete wet well
• Installation of two DN560 PE rising mains for discharging flows into the existing treatment plant
• Upgrade works in a live treatment plant and connection of the new pump station to the existing asset
• Construction of a DN700 GRP overflow pipeline and headwall
• A Sika Epoxy waterproofing and protective Coating membrane to the inside of the Wet-well walls.
• Construction of a new Control room housing the Main Switchboard and Variable speed drives for the 4 Wet-well Pumps
• Electrical works, supply and installation of pumps and required appurtenances
• Mechanical installation, testing and commissioning, provision of as-built information
• Site restoration
• Delivery of works in full compliance with the consent conditions

Project Description

This project was to construct a new pump station with a 9.5m deep in-situ concrete wet well structure to lift wastewater flows from Ashburton township into the existing Ashburton Wastewater Treatment Plant.

The flow from Ashburton township to the pump station was transported via a new 800mm diameter pipeline, which was installed by Seipp across the Ashburton River under a separate contract.

Prior to construction starting on site a full design handover workshop was completed with WSP and the Council to discuss the key requirements of the design. This included details around how the pump station would be constructed to ensure it would be watertight, how joints and protective epoxy membrane would be installed, and how hold points and testing would be carried out to an agreed ITP to ensure high-quality construction. Clever formwork shuttering, steel fixing, and scaffolding methodology and sequencing were developed in house in order to construct the wet well structure in two pours. This enhanced the watertightness of the structure by virtue of there being fewer construction joints to seal.

Works were undertaken in the flood plain of the Ashburton River and extensive dewatering had to be carried out within the sheet pile cofferdam to achieve a dry building pit. A dewatering strategy was developed and designed in house including all environmental controls. Several resource consent conditions needed to be complied with in regards to this activity and all works were conducted in liaison with, and to the satisfaction of, ECAN. Our team was awarded a certificate by ECAN for its exemplary attitude towards compliance and collaboration.

Our innovative approach to all aspects of this project significantly contributed to its successful delivery. Value adding innovations ranged from proposed design changes that were accepted by the client to optimised pour sequencing to mitigate the risk of potential leaks and bespoke formwork and cofferdam shoring designs to accelerate the programme.

On completion the Seipp Construction team were acknowledged, not only for what we delivered, but also for the way in which we delivered it. The project was completed under budget and on programmed and the acknowledgement from Neil Brown, Mayor Ashburton District Council, summarises the clients satisfaction with our delivery approach: “ The feedback I received is that you have been truly professional to deal with, and the close working relationship with you, developed with our staff and stakeholders, has been key to the success of this project. Your ability to get the job done, to work through and resolve any problems, big or small, has been appreciated."

Start Date: November 2019

Completion Date: November 2020