Landfill boss faces questions over gas leak
A joint council landfill boss has faced questions over a gas leak described by a councillor as “incredibly serious” and “dangerous”.
At a meeting of the Nelson-Tasman Regional Landfill Business Unit on Friday, general manager regional sewerage and landfill Nathan Clarke described an incident in which a section of pipe was broken at a join while a contractor was searching for leachate pipework.
This resulted in a “significant gas release” at the York Valley landfill in Bishopdale, Nelson, on January 10.
“As soon as the pipe as struck and essentially came loose, it let more gas out into the excavation.”
Nelson City councillor Mel Courtney, reading from the report, said that eventuated in a gas release of 40,000 parts per million.
“That, to me, is incredibly serious. Dangerous. What are we going to do to make sure this doesn’t happen again?”
The first element, Clarke said, was whether they should have known a leachate pipe was, and the answer was “probably yes”.
“There was an issue in and around us having accurate as built information for that particular pipe, so that was the reason we were having to dig to find it ... ”
Secondly, the amount of gas in the air, at 40,000 parts per million, was below the combustible range of methane.
Around 5%, or 50,000 parts per million, through to about 15% was the combustible or explosive range, he said.
However, Clarke also said the incident was “definitely what we consider a high risk”. “It definitely would have gone through a combustible range somewhere in that hole as it was coming out of the pipe.”
Other health and safety incidents over the last quarter included a man vaping beside a gas well, despite signage at the landfill about not smoking, which wasn’t “ideal”.
In another incident, in which the report noted gas levels were “explosive”, a contractor shifted the traffic manager’s hut next to a gas well which hadn’t been capped properly and had some “fugitive emissions”.
The gas was managed, the well was sealed with clay, and the hut moved.
Clarke also commented that the leak on January 10 “wasn’t really an incident”, and was what they called an “improvement opportunity”.
After the pipe was dislodged, everyone regrouped, and the gas permit was redone with completely different controls to fix the issue that occurred.
“It was actually the system working properly as it’s meant to do,” Clarke told councillors.
The landfill had previously purchased a laser methane analyser, additional personal gas safety meters, and a trailer with fans and generators to tow up to holes and dissipate gas. A permit system was in place whereby contractors required a gas permit for every activity involving gas on every day, which had to be renewed daily, he said.