As the expanded Cotter Dam inches towards completion, three internal galleries deep within the dam wall are crawling with workers wiring, drilling and fitting out a nerve centre which will gather data and help maintain and control the multimillion dollar infrastructure.
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Equipment sits in the main horizontal gallery under 700,000 tonnes of concrete.
To eliminate downtime during construction of the wall, the gallery was carved out of concrete, rather than erecting formwork for walls and ceiling.
A monster trencher which Actew project manager Ray Hezkial describes as a chainsaw on steroids chewed into the concrete creating a long void.
Afterwards, precast concrete lids were dropped into place in the void, creating a roof for the gallery.
Safety inspectors now walk into the three-metre by three-metre gallery looking for any signs of seepage.
Inside the gallery, core samples of concrete are extracted over the weeks and months after pouring to assess whether it is setting and strengthening in line with engineering assumptions.
The samples are crushed and checked for bonding and compressive strength in a laboratory which operates around the clock on-site.
''It's a continual process, the concrete is checked across the entire face of the wall,'' Mr Hezkial said.
Thermometers set within the wall, hard-wired and GPS-located, send temperature measurements to a data-collection case on one of the gallery's walls.
The case can be unplugged and hooked up to software to allow engineers to keep tabs on the concrete temperature.
Drains on either side of the gallery floor take away water which empties out of smaller intercept drains, spaced 15 metres apart and running vertically down the wall on the upstream face of the wall. The drains relieve pressure which otherwise could fracture the wall, and ease uplift pressure on the wall as well.
Two incline galleries on either side of the wall each have more than 80 stairs which were also precast to save time building formwork.
Within the next month, drilling rigs will be assembled inside the gallery to bore holes from the wall into foundation bedrock and abutments on both sides of the wall.
Grout will be pumped into these holes, forming a curtain to stop water escaping through fissures or voids under the dam wall, or from the abutments.
Major valves in an intake tower can be unbolted and taken out through the galleries for maintenance and repairs. A heavy door opens from one of the incline galleries into the intake tower and can be closed to withstand the water pressure in the reservoir in the unlikely event of the pipe failing.
The $400 million project is due to be completed by the end of the year.
Chief Minister Katy Gallagher will officially re-open Cotter Avenue this morning at an Open Day at the dam. The public is invited to walk over the new Cotter foot bridge and up to the Cotter Dam Discovery Trail. There will be a sausage sizzle, coffee, live music, face painting and activities available at the site from 9.30am. Visitor parking will be available at Cotter Bend and Cotter Campground, with a shuttle bus running from Cotter Campground.