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Sea Conditions Hamper Ocean Outfall Completion

Fuseworks Media
Fuseworks Media

Poor sea conditions have hampered the final section of the Ocean Outfall pipeline construction and have delayed the completion of the project.

The work has been running to schedule, but unforeseen poor weather in the marine section of the pipeline construction has delayed the last section from completion. There is only six weeks of physical work to complete but it is dependant on good sea conditions allowing access to the pipeline.

Mark Christison, Unit Manager City, Water and Waste says: "Although the end of the work is very close and our contractors are working every opportunity they can in the available weather windows, it is a priority to minimise risk with the work and not compromise health and safety. Because of this, the contractor is reliant on good weather conditions.

"The delay has occurred in the marine section of the work where the dredging, crane barge and diver crews can only work in favourable sea conditions with waves up to a certain height. Prolonged storm conditions have also caused open sections of the marine trench to infill, which then require re-dredging."

"This is a major project for the City, and we're very proud of what has been accomplished by the engineers and contractors. Since work began on site almost three years ago, 5 km of pipe has been installed. Approximately half was tunnelled wiith concrete pipe which extends from the pumping station at the Treatment Plant oxidation ponds, across the Estuary and South Brighton spit, and 500 metres off-shore. The other half which takes the outfall 3 km out into Pegasus Bay, is marine polyethylene pipe. The only work left to complete the outfall is fitting of the remaining 8 of 13 diffuser risers and completing the connection between the tunnel and marine pipe. All other work on the pipeline has been completed, and the tunnelling construction sites in South New Brighton Park and in the dunes have been reinstated. The pumping station was completed late last year and is ready to commission the outfall."

Because of the delays, the project is likely to miss the consent deadline on 30 September 2009 for the Ocean Outfall pipe line completion. The Council is working closely with Environment Canterbury regarding the consent requirements, and have held a special meeting with the Discharge Audit Group and other interested parties, to inform them of the current status of the project. The treated wastewater from the Christchurch Waste Water Treatment Plant will have to continue to be discharged into the estuary as it is now, until the Ocean Outfall is completed and the wastewater can be discharged 3 km out to sea.

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