Customer: Watercare Services Ltd Contract: Design & Construct Location: Warkworth, Auckland

McConnell Dowell (MCD) was awarded this design and construct contract by Watercare and the project is a component of the Warkworth to Snells Transfer Pipeline scheme, which conveys wastewater from Warkworth to Snells Beach.

The North East Wastewater Servicing Scheme will cater for future growth and enable Watercare to decommission the existing Warkworth Wastewater Treatment Plant which discharges into the Mahurangi River. The overall scheme comprises of a pump station, associated rising mains and a final gravity sewer that terminates at the proposed site for the new Snells Beach WWTP. 

The scope of works includes construction of a new 247 l/s Wastewater Pump Station located adjacent to the existing Lilburn Street Pump Station in Lucy Moore Memorial Park. The pump station is designed to be a wet well / dry well facility and includes: 

• an above ground structure approximately 4.4 m high, 9.2 m long and 4 m wide 

• belowground structures including inlet chamber, gantry crane, drywell, wet well and emergency storage to a depth of approximately 12 m. 
• an overflow pipe from the pump station to the existing stormwater pond 
• ancillary above ground structures, including odour control (biofilter), standby generator, transformer, flowmeter chamber and welfare facilities; and 
• an access road and carpark 

The challenge  

The Warkworth pump station site is located within Lucy Moore Memorial Park, adjacent to the Mahurangi River. The park is an open green space which contains a number of walking tracks, a skate ramp and flying fox. The park is a popular community amenity and provides a thoroughfare to the town centre. 

Lucy Moore Memorial Park is named after Warkworth’s own botanical legacy, Lucy Moore who was often referred to as the ‘mother of New Zealand botany’, gaining both national and international recognition for her achievements. 

The park and the river link to the historic Portland Cement Works further downstream. The cement works was closed down some years ago and the ruins remain on the banks of the river behind what has become a marina. 

The solution:  

The pump station and storage tank will be constructed using an innovative caisson (sunk shaft) construction method which provides the following benefits:  

• Reduced construction footprint due to a reduction in the working space  
• Less noise and vibration impact because there is no significant backfilling required 
• Minimised time required on-site, which further reduces overall community impact 
• Enhanced safety to site workers and park users 

The key to success

The construction methodology was developed with input from specialists and experts to comply with statutory, contractual and consent requirements. This includes the development of environmental controls to protect the sensitive park and river environment, engaging an arborist to identify and protect trees and vegetation, iwi consultation, and a strategy for effective stakeholder management of impacted residents and the invested community. 

Construction started in September 2021 and is scheduled for completion in November 2023.