Christchurch City Council presented their Update on Deep Bore Injection Option Locations and Costs to the Akaroa Treated Wastewater Reuse Options Working Party on Friday 27 April. The Council are planning to go ahead with a Deep Bore Injection test bore in May. One of the slides on the presentation shows the preferred list of test sites:
1. The Old Coach Rd WWTP site
2. Takamatua Peninsula
3. Takamatua Valley
4. Robinsons Bay Valley (Robinsons Bay geology appears to be less suitable for DBI at this stage)
They plan to do up to two test sites - the Wastewater Treatment Plant site at Old Coach Road and if that is not successful then out on Takamatua headland. They will do an initial bore to get the soil samples and this will become the monitoring bore, and then the actual disposal bore which they will tip the water down to test. It will have salt in it which they can then detect in the monitoring bore and with some above ground ionasation testing.
Drilling a single hole costs around $200,000 and takes 2 to 3 weeks (possibly quite noisy). This will only analyse that exact spot. There can be significant differences within a short distance. The Beca Geologist indicated that underground drilling searches were not always fruitful.
Ngai Tahu have not yet stated their position on DBI but have agreed to investigations being carried out.
CCC will undergo a fly-over in the Goughs Bay area to do Lidar mapping next week to try and establish if there is enough suitable space for storage ponds if a land based irrigation scheme was set up in that area.
FRIENDS of Banks Peninsula had made the suggestion of piping the whole wastewater scheme to Christchurch, (without the solids) which may seem a more extreme solution, but this would have ruled out the need for any treatment plant in Akaroa at all. The budget allocation for the plant could then have been put towards the piping costs, with the added opportunity for other communities along the pipe line to be able to hook into the system along the way as well, thus overcoming their own wastewater issues. Although this idea had no beneficial use for the wastewater CCC will be in the position in future years where they will have to look at land based options for the whole Christchurch scheme once the current Bromley consent ends.This idea was ruled out at the Working Party meeting on grounds of cost and that the sewage would be odorous and corrosive by the time it reached Christchurch.
The next Working Party meeting is in two weeks time by which time the Council will be underway with their test bore and will be able to start gathering information to begin their analysis of the viability of D.B.I.