The man in charge of Lower Hutt’s trunk main outfall remains confident it is in good condition, and won’t need replacement in the short-medium term.
Councillors rattled by a stress fracture in the pipe in the heart of Eastbourne, forcing another month of discharge of treated sewage into the harbour while it’s repaired, said last week that it’s bad for the Hutt’s reputation.
This latest shutdown of the trunk main comes on top of a six-week, $500,000 repair job on 11 joint seals along the 18km pipeline and led Cr Ross Jamieson to query if the city is being too optimistic on the robustness of the outfall.
City Services general manager Bruce Sherlock admitted that the fact the latest leak is due to a crack in the pipe rather than a joint failure “is a concern”. That’s why, as an extra precaution, during this forced shutdown E Carson & Sons contractors will walk the entire length of the pipeline to inspect its internal integrity. Previously, CCTV cameras had been used for the inspection.
As at last Friday, contractors had inspected 9km of the outfall including random checks on joint seals and had found no other problems. They’re mystified as to what caused the stress fracture near the corner of Muritai Rd and Rimu St.
The rest of the pipe will be inspected this week but the outfall is expected to be out of action for another three weeks because of a delay over parts needed to repair the fracture.
Mr Sherlock said he’d be able to assure councillors “with more confidence” when the inspection is complete. But he reminded them a 2004 in-depth investigation, including core sampling, found the 1960-commissioned main trunk to be in good condition, with an anticipated useful life of another 30 years or so.
Replacing the pipeline would cost about $30 million, but a government subsidy of 28% would be available. It’s a possibility any new pipeline would be laid under the harbour.
The council has put in its 10-year budget a $30 million contingency, mostly coming into effect from 2019. Mr Sherlock says an upgrade to the capacity of the outfall will be necessary if the resource consent allowing discharge of treated sewage overflow into Waiwhetu Stream in times of heavy rain is not renewed in 2013 (though he’s confident it will be renewed), or if growth in the city requires a bigger/better pipe from Korohiwa to the outfall (the section where pressure is the highest).
He said if it was found necessary, some of that money could be diverted to replace all 4,000 of the joint seals along the pipeline at a cost of $3,000 each.
Cr Jamieson said the pipe shutdowns annoy fishers and other harbour users, cause traffic disruption while repairs are done, and – despite the assurances that the material being released into the harbour is secondary treated sewage from the Seaview plant, with a quality and appearance close to water – ”Waiwhetu Stream stinks. It does!”
Fellow Eastbourne councillor Joy Baird said the pipe shutdowns damage council’s credibility but Mayor David Ogden said he refuted that. The Hutt Valley had spent $60 million on a modern treatment plant at Seaview that it could have built out at Pencarrow Heads. It had taken all the care it could to inspect the main trunk pipeline, ”and I have said consistently if we need to build a new pipeline, we will”.