Days Bay. Photo: RNZ / Angus Dreaver
Wellington's water provider hopes it can start excavating the site of a broken sewerage pipe in the Eastbourne harbour in Lower Hutt on Monday morning.
Since the main wastewater outfall pipeline next to the pump station in Days Bay burst on Saturday afternoon, it has been leaking treated and untreated wastewater into the harbour.
The overflow has also forced the closure of three public beaches, at Days Bay, York Bay and Sunshine Bay, and local iwi are considering a rāhui.
The repairs are likely to take several days and Eastbourne residents are being asked to flush toilets less and avoid taking long showers to conserve water.
Wellington Water's head of network management Jeremy McKibbin said it was not a straightforward leak, and repairing it had required further discharging wastewater into the harbour in order to drain the pipe.
Wellington water working to fix broken sewer pipe in Lower Hutt
Several wastewater pump stations are in the immediate area, he added.
To reduce water flows and make it safer for repair crews, the main wastewater outfall pipeline to Pencarrow Heads had also been closed. As a result, treated wastewater was being released into the Waiwhetu stream.
McKibben said it was difficult to know what had caused the break until excavation got underway. But he said initial assessments had found that two valves near the leak may have been affected.
"One valve connects the pump station to the pressure main that supplies water back to the Seaview treatment plant for treatment; the other valve connects into the main outfall pipe, that takes treated waste water out to Pencarrow. Two different valves, connecting to two different parts of the network."
The repair was "extremely complex" because it was in a "challenging location".
"It's quite deep, and in the tidal zone, so once you dig down to it, it's affected by tide, ít's also affected by the main outfall pipe - the wastewater in there - we actually need to get that drained down because it's quite a high volume."
McKibben said Wellington Water acknowledged the impact the incident had had on the environment and on recreational users in the area.
"This is why we are working as fast as we can to undertake the repair."
Crews had worked "at pace" throughout the weekend and on Sunday night, while trucks had been going back and forth to transport untreated wastewater to the Seaview treatment plant.
They were collecting it at two pump stations to reduce the amount going into the harbour.
McKibben said the main outfall pipe at Days Bay was in a "reasonably poor" condition.
"We do have challenges with that pipeline pretty regularly. It's a very expensive piece of infrastructure that needs renewal. It's in the Long-Term Plan but that's a while off."
'Complicated operation'
Lower Hutt Deputy Mayor Tui Lewis told Morning Report it was a "complicated operation".
"It's in a tidal area as well, you know. they've got a big job on their hands but they've made great progress."
She spoke with Wellington Water on Monday morning, saying they had the situation "totally" under control.
"Nobody likes the environment to be impacted with human waste, and it's not good. So hence there is speed on this job to fix this and get it going back to normal. A rahui will be placed I'm sure, with iwi - they're all engaging, talking, discussions on what to do in that area and to the range of which it will cover."
There were concerns some fishers would still try to catch food in the harbour, despite the risks.
"A lot of fishers come from all over the region going on to use that harbour. It's easy access off the cycleway, walkway that's going in there. So definitely there'll be engagement there with people that are trying to get kaimoana out of the sea.
"The residents have been fantastic. They understand what's going on, and I know that they will be reducing their use, and they're very patient. They want everything repaired as fast as possible as well, and I'm sure they will engage with any fishers they see that are trying to get there and fish. A lot of the fishers that come to the area are not New Zealanders, so language is a barrier as well - but that can be easily fixed."
She expected a timeline for the fix to come out of a meeting by midday Monday.
"I'm sure they will come back with a… time that they can put on it, that they will be finished."