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Stormwater infiltration targeted

Council is taking a pro-active approach to stormwater infiltration which could save thousands of ratepayer dollars every year.

Stormwater is a major issue for the Wairoa township and an action plan to solve the historical problem and partner with the community is underway.

Council’s Inflow and Infiltration Programme has included CCTV footage of the sewerage network, smoke testing and an efficient cloud-based web portal and tablet which have been used to identify issues.

Council’s Group manager community assets and services Stephen Heath believes the problem could be solved within three-years saving thousands of ratepayer dollars and having huge environmental benefits.

“There is so much water being pumped into the sewerage system and treated at the sewerage plant which doesn't need to be.

“Inflow and Infiltration can be through downpipes plumbed into the sewer network, ponding of water on properties that builds up and flows into gulley traps or stormwater getting into the sewer network via cracked or broken pipes.

“Whatever the infiltration process, it is costing Council thousands of dollars and prematurely wearing out the sewer infrastructure by running at over capacity when stormwater enters the sewer network.

“Inflow and infiltration into sewer networks is not just limited to Wairoa, it is a nationwide problem, and we are fortunate our township is agile enough to make significant changes to achieve a world-class wastewater system.

“On some occasions, Council is processing 10 times more wastewater than it should be and using a system that was designed to cope with four times the capacity."

Part of the process will include identifying and removing illegal connections to the sewer network in a staged approach occurring over the next five months.

Stormwater connected to the sewer and the likes of gulley traps is not allowed, and initially, Council will partner with the community to remove illegal connections at no direct cost to the property owner.

Mr Heath said Council wants to provide a more reliable network, so it can meet its aim of having no untreated wastewater overflow into the river by 2020.

“On a daily basis council processes 1500 cubic metres of wastewater, and that can spiral to 8000 cubic metre when it rains.

“We have a high rainfall, and because our systems are not where they should be, we are treating a t of rainwater that we don’t need to be.”

He says some of the issues are historical and relate to 20-30 years of legacy and historical regulation.

“Some of the historical plumbing work where roof downpipes are plumbed directly into the sewerage system is so old so the house may have been sold on a couple of times, and the current owners are not even aware their connection is illegal.

“Another issue is properties built in the 1950s or 60s with gully traps at ground level so as soon as rainwater starts ponding it runs into the sewerage system."

“It is also important to acknowledge that environmental expectations and regulations have changed considerably over the years.

Removing illegal stormwater connections will in some cases be a challenge, however, non-compliance is not ok. This is a journey we want sustainable solutions and an engaged community that is thinking long-term."

Mayor Craig little said water infiltration into the sewer network had been an issue for decades.

“I commend the council and staff for tackling this historical problem and for recognising it is an issue and the consequences it creates, it is great to see Council is getting on with fixing it.

"It's important that we seek to future proof our infrastructure, that it is as efficient and effective as possible. Finding these efficiencies saves on costs and therefore does not become a burden on our ratepayer."

13 February 2019

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