The multi-million dollar cost of fixing the city’s well heads has been revealed.
A city council report has shown two options to regain water secure status. The preferred will cost $21.5 million.
Temporary chlorination began on the city’s water on March 26 following the discovery in December that it had lost secure status due to the condition of some well heads.
City councillors voted in January to temporarily chlorinate water while well heads were repaired.
The cost is due to staff recommending well heads be brought above ground.
“The estimated cost of converting 81 well heads to above ground well heads and drilling a replacement well at Auburn Pump Station is $21.5 million,” the report said.
But there is insufficient funding allocated in the draft Long Term Plan to cover the cost.
The report said there was no “budget provision” for the work.
The draft Long Term Plan includes $34.1 million, but this is allocated for other work on wells.
Using some of that budget would mean fewer wells could be renewed and some are in “poor condition”, warns the report.
However, staff have recommended a review of the “overall capital programme” in the LTP to identify funding sources.
The report said this option risks chlorination being necessary for longer than 12 months.
The other option is to leave 76 of the well heads below ground and raise five above ground.
“The estimated cost of making 76 below ground well head secure, raising five well heads above ground is $10.5 million.”
But the report said this option does not comply with the recommendations of the Havelock North Drinking Water Inquiry, is unlikely to meet future Drinking Water Standards for New Zealand Requirements and will mean well heads are harder to maintain.
The report also reveals 18 of the bores are “unlikely” to achieve secure status left as they are. “This is due to their shallow draw off depth from Aquifer 1, location or inaccessibility for remedial works,” the report said.
“Either these 18 wells could be replaced with deeper secure wells or UV disinfection could be installed at some or all of these sites.”
Drilling replacement wells would cost $15 million if these were located at existing pump stations. But this may not be possible.
Installing UV treatment at the 10 pump stations where the 16 wells are would cost $5 million.
“The overall cost for making all below ground wells secure status is very dependent on the solution chosen for the 16 wells that are unlikely to achieve secure status.”
The report said costings are subject to +/- 30 per cent as they are at concept level.
An update will go to the city council or infrastructure, transport and environment committee in May.
For more information about the temporary chlorination of Christchurch water go to ccc.govt.nz/water-chlorination.