Wastewater plant on schedule

20:01, Jan 23 2013
timaru wastewater
ALL GO: Timaru District's new wastewater treatment plant is taking shape.

About one-third of the work on the Timaru district's new $15 million wastewater treatment project in Aorangi Rd is now complete.

Originally the project included a buffer period, with work expected to be completed about six weeks ahead of the December 2013 project completion date.

Three floods and heavy rain in August and September meant subcontractors forming the three ponds on the 48-hectare site lost a lot of time, district council drainage and water manager Grant Hall said yesterday. Much of the site was under water from July to October, with minimal earthwork possible.

Some of that time had been made up, and Mr Hall was confident the December completion date would be met.

The all-up cost of the project, including piping treated liquid from the Geraldine, Pleasant Point and Temuka schemes to the Aorangi Rd maturation pond, new sewer pipes in Timaru city, splitting of commercial and domestic waste, and the Aorangi Rd project, will set the council back more than $40m.

The new treatment system has been designed to meet the district's needs for at least the next 50 years. It is also required to ensure wastewater treatment was to the higher level now required for schemes with ocean outfalls.


Between 25 and 30 staff are working on site at present, with that number expected to increase to closer to 40 towards the end of the contract. While Downer was the main contractor, Mr Hall said the subcontractors were mostly local companies. About $1m worth of work is being carried out each week at present.

About 200,000 cubic metres of the 565,000 cubic metres of material being shifted to form the two treatment ponds, maturation pond and 10-hectare wetland, has now been excavated. The ponds and wetland are capable of holding a similar amount of liquid as 200 Olympic-sized swimming pools.

Silt from the site, which needs to be excavated to form the ponds, is being used to line them. At this stage enough silt has been harvested to line the completed sections of the ponds with none needing to be bought and transported in. Using a synthetic liner would have added millions of dollars to the project. By comparison the synthetic cover on the town's two-hectare water reservoir cost $500,000 15 years ago.

One of the next major phases of the project involves installing the pre-cast concrete sections of the screening structure. Substantial piping work is still required over much of the site.

The Timaru Herald