From the magazine, HDD

Protecting Bendigo bush with HDD

Stage 1 of the 22.4 km pipeline project commenced in October 2010 and was completed in July 2011. Coliban Water commenced Stage 2 of the project in July 2012, which involves constructing 11 km of 250 ODE PE water supply pipeline to connect Raywood and Sebastian to the Bendigo supply network.

Leed Engineering and Construction were contracted to complete Stage 2 of the project, and have subcontracted the horizontal directional drilling (HDD) portion of the works. An impressive 6.8 km of the pipeline will be constructed using HDD, and only 3.8 km of the pipe installation will be via trenching.

Coliban Water General Manager Infrastructure Dr Dharma Dharmabalan says the water authority is extremely pleased to see work underway again, given the delays the project had experienced.

“The project has experienced significant delays as a result of severe wet weather, unexpected soil conditions, resolving planning permit conditions and contractual matters.”

Challenging geology

The bore path runs through incredibly variable soils, ranging from rocky shale, alluvial flood plains, Shepparton formations and silty clay.

The project has four Ditch Witch rigs in operation and a fifth rig on standby. Three of the rigs are Ditch Witch JT3020 rigs, and the fourth rig is a larger JT4020 MATCH 1 drill, which has been key to drilling through the more solid, rocky and otherwise challenging installation conditions.

HDD pushes through wet weather

Wet weather conditions impacted mostly the trenching aspect of the project, and boring was able to continue through the wet weather. Additional drilling fluid transportation trucks were required through the wetter parts of the project, due to rainwater mixing with drilling fluid and requiring more frequent trips to drilling fluid dumpsites.

A green approach

It was a high priority for Coliban Water to protect native vegetation while performing the installation. The area, which once would have been covered in Australian natives, has been greatly reduced of vegetation by farming settlements, with the majority of bushland in this area remnant vegetation in road reserves.

The Rusty Head Orchid, a rare Australian native, is known to grow in prolific clusters within the boundaries of the project area, and as such was one of the contributing factors in the decision to use the environmentally sensitive installation method of HDD.

HDD was also utilised as a means to cross under a creek, which would have been costly, environmentally disruptive and impractical to trench around.

Looking ahead

The project has been progressing well and is currently on schedule.

Dr Dharmabalan says “We anticipate works to be completed in September 2012, weather permitting.”

The bore path runs through incredibly variable soils, ranging from rocky shale, alluvial flood plains, Shepparton formations, and silty clay.

Send this to a friend