Work began on repairing the leak on Monday. Photo / Leanne Warr
Work began on repairing the leak on Monday. Photo / Leanne Warr
Tararua District Council has been tracking a “mystery leak” in Dannevirke’s main street, but has been hampered by a number of challenges.
Council group manager of infrastructure Chris Chapman said complaints had been received about the water coming out to the roadside near the intersection of Stanley and Stairs Stsand at first it was coming from a subsoil drain.
“It always flows when there’s rain or high water tables,” Chapman said.
A council spokesman said council testing prior to September had confirmed the water was stormwater flowing from the rail corridor.
He said this changed in early September when the first positive test for chlorine was received, indicating treated water was now included, and the water flow increased.
“That’s when it indicated it was a leak,” Chapman said.
Council staff did acoustic leak detection surveys, however, those were hampered by traffic noise on the highway, so they also used ground-penetrating radar and excavation.
Chapman said some of the records from the past were not “overly great”.
“We had to confirm the pipes that were in the ground and where they were.”
He said layout records of the network weren’t correct, adding to the challenge.
Council was always making changes to its asset data, but because they were dealing with pipes in the ground it would become expensive to confirm everything, Chapman said.
Issues such as location, what materials were used, how deep, measurements and age had to be confirmed, he said.
“It becomes very challenging.”
This was not unique to Tararua district because much of the old infrastructure around the country wasn’t recorded.
“It’s quite important to have that information, but very easy for it to be out of date.”
Chapman said he understood there were frustrations around the “perceived lack of action”.
He said there were other issues such as the location of the leak, which was in a pipe along the rail corridor, and council had to make decisions around that.
“We’d need to close the rail line down while that work was being done,” Chapman said.
There were also requirements and restrictions that council contractors would have to meet around depth and protection of the rail, especially if the decision was to put in a new pipe.
The council spokesman said due to the dangers of working within the rail corridor, the council had assessed the best remedy was to reline the existing pipe.
He said specialist contractors had been engaged to undertake the relining work, expected to be completed within the first half of December.
Chapman said to the best of his knowledge there was only one contractor that did that type of work, “so that’s been a challenge”.
Tararua Alliance staff had completed preparatory work, including the installation of new valves to enable the pipe to be isolated for the repairs, and staff had been engaging with stakeholders such as KiwiRail and Waka Kotahi to ensure all the necessary permits and approvals were in place.
Rawhiti St was down to single lane, as was the area near the roundabout at the intersection of Stanley and Stairs Sts. Photo / Leanne Warr
The work was due to start this week and would include a single-lane shutdown in Rawhiti St, a single-lane shutdown before the roundabout, and a traffic management plan would also be in place during the work.
