The Dannevirke dam problems are still ongoing

Repairs were carried out in June last year, but in the process it was identified that the lining and underground drains were in a worse condition than expected and the council was advised to carry out repair work during the 2023/24 construction season.

In October last year, the council had decided to delay the remedial works until design work was completed, geotechnical investigations were completed and pre-treatment and additional storage of raw and treated water.

Earp said no significant deterioration had been observed on the ground in the seized supply when the ROV was used last month.

“We’ve had a review from Tonkin & Taylor (and) their comment is that obviously the dam could deteriorate rapidly, but there’s nothing to definitively indicate that at this point.”

He said the next stage was to get divers to re-mark the depressions so they could continue to be monitored to ensure that if there was significant deterioration it could be recorded.

Earp assessed that there would be some frustration among councilors in relation to last year’s approval to start pre-treatment.

He said that because they didn’t have all the information about the status of the seized supply, he felt it was important to delay those decisions until “we were sure we knew where we were going at that point.”

“The total cost was still unclear and for me there were too many unanswered questions to commit significant amounts of money, five to six million, with all that uncertainty.”

The previous decision had been to buy a relocatable sewage treatment plant, but this had turned into a permanent additional sewage treatment plant.

“Given that the plant we were looking at buying had never been built before, so it was a first,” Earp said.

“Personally I’m very glad we didn’t proceed with it at the time and now we can go out to the market and get some designs for a permanent treatment plant.”

Chief executive Bryan Nicholson said at the time of the decision last year, there were many unknowns regarding the seized supply and it had been a collective decision-making process about the postponement.

There had also been an independent review from which he endorsed the council’s decision.

Councilor Peter Johns said he was disappointed the council had not proceeded with an additional treated water tank or storage and pre-treatment.

“We’re back to where we were a year ago.”

Nicholson said the council had been monitoring the seized supply and it had been working.

“The current supply we have been providing to the Dannevirke community was the same as before the leaks were detected, so there is a fully functional dam.”

He said the risk had been analyzed and felt there was enough time to delay hiring any contractor to do the work while they understood the problem much more than they did at the time.

“So I think it was 12 months doing more due diligence on that.

“The last thing we want is to put all that in place and then it wasn’t the right decisions either, so I think the 12 months have been beneficial for us to understand the whole system more than we did 12 months ago .”

Mayor Tracey Collis asked what would happen if there was a dry summer and if there was a plan to ensure people had water.

“Are you sure how the dam is running right now that we might know?”

Earp said if conditions similar to 2020 are faced again this summer, there would be some challenges, but a leak detection program is being finalized.

He said the program would specifically look at rural areas where water has been used up and was confident it would help manage that demand.

“The other thing I would stress is that the approach that was taken around all of the water management over the last summer seemed to work very successfully.

“We didn’t have any water restrictions at Dannevirke and it’s just going to be such close, regular monitoring of how we’re going, monitoring our rivers, monitoring our reservoirs and we’re monitoring demand.

“We are able to do that effectively and efficiently and that definitely helped us manage the situation last summer, so I would recommend it again this summer.”