WWTP AERATION BASIN - RANGIORA
The works also involved significant pipe installation to connect the new aeration basin to existing ponds, distribution structures and the new pump station. All the pipework installation on this project was completed directly by Hunter Civil staff. The depths, grades and the sizes of the pipelines varied from 4m through to shallow depths of 1m. The deep trenching required the use of mobile trench shields and shallow “sump/well” dewatering within the pipe trench. The pipe sections installation included:
120m of 825mm dia at 2m deep
70m of 825mm dia at 3.5m deep
40m of 450mm dia at 1.8 deep
100m of 450mm dia at 1-2.5 deep
30m of 335mm & 250mm dia at 1.5m deep
Punched Novacoil Drainage – 550m of 200mm dia at 1.5m deep for dewatering
One of the large new structures was the distribution chamber. It was a reinforced concrete control structure with a large GRP pipe cast in the center of it. The chamber had wall thicknesses of approx. 400mm, including two layers of reinforcing, waterstops/bars and constructed with high spec concrete to prevent water leakage. The structure had to be water tested for 7 days and passed without issue. The temporary works required to complete the chamber included 8m FSP3A sheetpiles, whaler beams, corner whalers and props.
The project included several differing work types. From site clearance and earthworks, drainage & pipeline installation, reinforced concrete, sheetpiling, dewatering, PE liner works, mechanical and electrical installations. This project demonstrates Hunter Civils ability to complete extensive wastewater pipeline/structure construction and an array of different work types within the environment of a live treatment plant. It also demonstrates an ability to manage several sub-contractors including client nominated subcontractors.
May 2017 - May 2018
Waimakariri District Council
This project involved the construction of a new earth wastewater treatment aeration basin at the Rangiora Wastewater Treatment Plant (WWTP). The site was an active wastewater treatment plant, and the contract works were carried out at the same time as other significant construction works to construct a new inlet pump station, control building and screening channel. The earthworks involved 37,000m3 of material removal and 27,000m3 of imported fill to construct/shape the new pond. A HDPE liner was then installed over a layer of sand bedding across the pond.