Wastewater project brings benefits

The $39.5 million Gisborne Wastewater Project is bringing benefits to the community through jobs, goods and services and, by early next year, cleaner wastewater going into the bay.

Gisborne District Council project manager Peter McConnell says local people are getting a good chunk of the project pie.

“While difficult to quantify in dollar terms, the project has contributed to winter earnings for more than half a dozen local businesses and provided jobs on various sites involved in the project. Apart from that, there have been beneficial spin-offs for owners of rental accommodation, whose houses have been filled by out-of-town contractors, and food and beverage retailers.”

About half of the 40 workers now working on the Banks Street site are from Gisborne.

Colin Newbold, project manager for lead contractor HEB Structures, says out-of-town contractors are contributing to the local economy, with most living in Gisborne and making occasional trips home at weekends.

“Gisborne subcontractors are involved in concrete supply, construction, pipe laying and mechanical installation works.”

They include Currie Construction, which is responsible for the above-ground construction of the pre-treatment and control buildings; Electrinet, responsible for welding 5000 cubic metres of plastic media blocks that fill the biological trickling filter tank; McLeods Concrete Contractors, Aitkens Concrete and Ritchies, which together have provided and poured the 3500 tonnes of concrete delivered to the site to date; Lloyd Contractors, involved in drainage work for HEB and Downers; Eastland Scaffolding; and engineering firms Eastland Engineering and Universal Engineering.

Universal Engineering has a significant subcontract fabricating and installing pipework and fittings in the pre treatment building and the three major pump stations on site. Gisborne-based Downer EDI Works won the $1.1M contract to build the western industrial pipeline, which is on track to finish in October.

Mr Newbold said work was progressing well on the four main concrete structures on the Banks Street site – the biological trickling filter tank, the pre-treatment and control buildings, and the outfall pump station – a massive engineering feat that alone has 2000 tonnes of concrete and about 120 tonnes of steel reinforcement. The structures are expected to be ready for mechanical and electrical fitout by the beginning of September.

All bar a few of the 40 pre-cast concrete panels – each of them 8.8m tall and 8.5 tonnes -- have been erected to form the external wall of the biological trickling filter tank. Concrete has been poured in the vertical gaps between the panels and the structure will shortly be tied together by tensioning steel cables in ducts within the wall panels. The tank will be covered with an aluminium dome roof, the apex of which will be 15m above ground level.

Mr McConnell said the layers of plastic media within the tank would sit on a raised concrete grid floor.

“A grid of fibreglass pipes is being laid under the floor section. This air extractor system draws out the odour from the bottom of the tank, recycles three quarters of it, and pushes the remaining quarter out into specially designed odour beds – bark beds that are kept watered.

“The walls of the biological trickling filter tank are held together by a series of steel wires, in conduit within the walls, that are held in permanent tension.”

The biotransformation process achieved through the biological trickling filter tank will see human waste transformed into plant-like matter before being discharged through the existing outfall 1.8km into the sea.

“Despite a late start, the Awapuni industrial separation programme is progressing better than expected thanks to the skill of Connell Contractors and the use of glass reinforced plastic pipes and manholes.”

Mr McConnell says the Banks Street site was running slightly behind the tight programme and had been hampered by seven working days lost to wet weather.

“Council, consultant and contractors are all working well with the same common objective of working in a partnership to complete the works to a high standard and under forecast budget.”