Original Sewerage Design Retained for Messenger Tce

Private sewage pumping stations will still be required for many residents on Oakura’s Messenger Tce, following an investigation of alternative sewerage designs by New Plymouth District Council.

At the request of some residents, the council reviewed three options for providing gravity-fed sewers for properties from 39 to 105 Messenger Tce.

“We had previously examined the possibility of a gravity-fed sewer in this area before finalising the current sewer design as the best solution given the topography, but we decided to look again to see if there was any feasible way of making it work,” says Manager Water and Wastes Brent Manning.

“We looked closely at the possibility of installing a pipe above the face of the bank that runs parallel to the beach, or a shallower sewer along the contoured face of the bank, or a sewer behind the existing rock sea wall at the toe of the bank.

“None of the options are feasible for a variety of reasons, including the bank’s stability, construction and maintenance access, erosion, time delays for legal work and the increased price that would result.

“In our view the best solution is for these properties to have private sewage pump stations to connect to the new sewerage network.”

Today’s (Tuesday's) Kaitake Community Board meeting also heard that the Oakura sewerage project’s cost has risen from $19.1 million to $24.27m. The increase will be met by raising additional debt.

Mr Manning says there have been a number of factors behind the price rise.

A trial dig of the site for the booster pump station on Shearer Reserve had mixed results. In some areas the ground conditions were better than expected; however an aquifer was identified which makes construction of the pump station at the original depth very risky.

Also, the general ground conditions made the construction of deep sewers impractical.

“We are now redesigning these areas to meet the demands of the environment,” says Mr Manning.

“We are also constructing two additional small pump stations to serve about 18 sections at both The Key and on Messenger Tce – or 36 properties in total.

“These factors, along with the actual tendered rates of the construction contracts, have led to the increased project cost.”

Meanwhile, construction of the 11km main trunk sewer from Oakura to New Plymouth is about 65 per cent complete. Tenders for the last of five construction contracts within Oakura are now being evaluated, with work well under way on the other four contracts.

Of the 691 properties able to link to the sewerage system, the owners of 529 properties have opted to connect.

The report on the Messenger Tce sewer design will be considered by the council’s Monitoring Committee on 6 May, while the progress report on the sewerage project will be considered by the Policy Committee on 13 May.