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Projects great success - harbour water is clean

 
This page contains information about our harbour water.
Updated: 23/11/2018 12:14 p.m.

​Whangarei District has had no harbour closures due to sewage spills following storms since 2012 and has achieved this result at a total of $24m.  

In the past, storm water and groundwater flowed into the District’s sewer system during major rainstorms and a mix of storm water and untreated sewage overflowed into the environment. That is not the case any more. 

 “In 2008 the community told us loud and clear that that kind of closure was unacceptable and we needed to fix the system," said Council Waste Water Manager Andrew Carvell. 

“We asked what the community really wanted – was it to prevent storm water from getting into the waste water system and causing untreated overflows (at a cost of around $200m), or was it being able to rely on a clean harbour and still be able to fish, gather shellfish and swim after storms? 

“The people wanted a clean harbour, so we looked at how to achieve that. Rain runs to the lowest point in any system, and ultimately to the sea. We could not realistically keep it out of our sewerage system, but we found we could make sure it was held, treated and controlled, rather than discharged untreated as it had been in the past. 

“We sought advice from tangata whenua, the Northland Regional Council, Northport and contracted local engineers and branches of construction firms including United Civil Contractors, Fulton Hogan, Downers and Hydrotech. 

“We worked together with a single goal in mind – a clean, safe harbour water, fish and shellfish after storms and we achieved the result we, and the community wanted. 

“We looked at ways to prevent the storm water getting into the sewer system and the price to achieve that would have been about $200 Million. Our community could not afford that, so we decided to expand our sewer system and build new facilities to hold it and treat the huge quantities of wastewater going into it.  That way we could control the water that discharged into the environment and make sure it was very clean. 

 “We have also reorganised our network to reduce sewage spills at specific spots. Since this work was done we have had no harbour closures associated with sewer overflows and we have had a steady improvement in customer satisfaction.”

“As a result of our $24m programme of projects the risk to public health from sewer spills in wet weather has largely been addressed with key overflow sites eliminated or the bacterial discharge reduced by more than 99.9%. 

“The last major work in the series is the overflow tank at Tarewa Park (Tarewa Tank). It includes a 650m3 storage tank and an ultraviolet disinfection system, to hold and treat the water that comes into the system during big storms. 

“Other projects have included pipeline renewals and upgrades and improvements to the sewer treatment and disposal systems.

Overview of completed wastewater overflow projects

 

Project​ ​Cost ​Comment
Okara Park pump station and new rising main​ ​$4.5m ​2011 - Stopped biggest raw sewage overflow site
Hatea storage and treatment tank ​ ​$5.5m ​2012-14 - Stores up to 1,000m3. UV disinfect anything over this
Storm UV system at treatment plant ​ ​$3.0m ​2013 - 100% of wastewater going to Kioreroa plant is disinfected. Capacity of 125000m3
Kioreroa Wetland  upgrade​ ​$2.0m ​2014 - All wastewater to go through refurbished wetland using floating media
Sewer relining project and pipe upgrades​ ​$3.0m ​2014-17 - Fix leaky sewer. Include 1.3km relining ($2m less than replacement). Includes Denby Crescent
​Hatea storage tank
stage 2
​$0.5m  ​2015 - Allows diversion of wastewater from Mill Rd sewer into Hatea Tank if sewer network is full
New off load site Tarewa Park​ ​ $5.3m ​2014-16 - Construct another Hatea system
Overall cost  ​ ​$23.8m ​Original containment solutions were $50 - $200m with no guarantees about performance
 

“The work will never stop though – our community is growing, and future focus is on managing growth, renewing aging infrastructure and improving levels of service in areas such as odour control. Future projects will include:

  • Takahe St Sewer Diversion: Council is currently working towards engaging a contractor to construct a sewer diversion line to resolve the sewage overflow that currently occurs in Takahe St, Tikipunga during periods of high rainfall
  • Whangarei WWTP Odour Control: Beca have been working with Council to develop a programme of works for managing the odour generated at the wastewater treatment facility.  Beca have now been awarded the contract to design the detail of the odour control works, and construction is planned to be in 2019/2020
  • Kioreroa Rd consent renewal
  • Whangarei Heads Sewerage Scheme Upgrade: Whangarei Heads sewer network is now being overwhelmed during storm events due to a combination of inflow and infiltration and an increase in properties connecting to the scheme. Council plans to commence investigations and design for the network upgrades next year with construction planned to start during 2021-22. 

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