Bridging the gap for irrigation network

As part of its plan to upgrade and improve road access and water flow across its irrigation network in the Griffith region, Murrumbidgee Irrigation commissioned three new crossings each consisting of three Rocla® crown units with special base slabs and headwalls. The completed bridges opened to traffic at the end of September.

With the existing cast insitu, single span culverts being 60 – 70 years old and only wide enough to carry a single car, new infrastructure was required to better accommodate school buses and machinery for the local farming area.

Murrumbidgee Irrigation’s Infrastructure Planning Manager, Jody Rudd, said the aim was to build a structure that provided similar flow characteristics to the existing structures. The crossings were designed by Murrumbidgee Irrigation and installed by Ladex Industries from Wagga Wagga.

“What’s most unique about this project is that the flows on all the crossings are continuous,” said Jody. “Constructing the culvert crossings presented quite a challenge being on the main drainage system leading out of Griffith.”

Whilst installing culvert crossings is nothing new to Jeff Ross from Ladex Construction Group, diverting channels was a whole new challenge he’d not encountered before. “We worked through all the scenarios,” said Jeff. “We looked at sheet piling or re-diverting the whole canal, but in the end the best option was to create a cofferdam.”

Murrumbidgee Irrigation are pleased with the result and are now underway on a further three crossings utilising Rocla’s M-Lock® Precast Bridge System; a solution for small to medium spans (7 – 15 metres) using precast, reinforced concrete components. This will be a first for Murrumbidgee Irrigation, but not for contractor Ladex. “This is a great solution for the smaller crossings as it will avoid inflow construction activity,” said Jody.

“Rocla have been more than helpful throughout the project,” said Jody. “You try to minimise surprises in construction activities, but there are always some. Rocla were always available to work with us to mitigate costs and timeframe overruns.”