Extra strong EUROFLO® pipe has formed part of the solution in a roading project designed to reduce the flooding risk on a section of State Highway 6 (SH6) in the South Island.

Fulton Hogan had the contract for this Waka Kotahi/NZ Transport Agency project and chose to use EUROFLO®’s 1700mm SN8 culvert pipe and rubber rings, to deliver a durable, high-capacity solution.

The work was carried out on SH6 near Kingston on a section of the highway that acts as a critical route for freight and emergency services.

In early 2020 and early 2021 two separate heavy rain events resulted in flooding, mud and debris on the road — trapping vehicles and causing closures which saw the Southland town cut off from important services.

Discussing the project in a Waka Kotahi video, Mark Stewart, the maintenance contract manager for Central Otago, said the agency realised the existing pipe was potentially not fit for purpose.

“We realised that the existing pipe was potentially under capacity for the amount of rain coming off the hills. So we worked towards increasing the size to a larger pipe with the aim of making this section of road more resilient during heavy rain events.”

Fulton Hogan’s decision to use the 1700mm diameter SN8 culvert pipe means the solution will stand up to very high flow during heavy rain events in the future.

EUROFLO®’s civil SN8 is a twin-walled culvert pipe made from high density polyethylene (HDPE) with a double-ribbed exterior for extra strength and a smooth bore for superior flow with reduced silt built-up.

EUROFLO® pipes have a projected lifespan of 100 years in New Zealand conditions.

Another added advantage of the EUROFLO® pipe is that it is easier to handle, weighing in at around 5% of the weight of concrete pipes.

“Being able to easily handle a much greater length pipe meant that we were able to minimise the disruption to motorists by spending less time on the bedding material and on the pipe installation,” says Gerard Williams, operations engineer for the Fulton Hogan-led Aspiring Highways alliance.

“There is no alternative route through this area so closing the road was not an option. With the 5.8-metre lengths we were able to effectively install the pipe across two nights, whereas we would have expected to have taken up to five nights with conventional concrete pipe.”

WHERE: State Highway 6 (near Kingston, South Island)
WHEN: March 2021
WHAT: Culvert upgrade to reduce flooding risk for SH6
EUROFLO®: 5.8m lengths of 1700mm SN8 EUROFLO® pipe, plus rubber rings

Download a copy of the case study here.