THE legion of navvies who dug out Breakout Creek in the 1930s would surely be impressed with how it looks today. Back then, flooding along the lower reach of the Torrens River regularly inun dated as far inland as where Adelaide Airport is today. Breakout Creek, designed to cope with a 1-in-200 year flood, diverts the river out to sea at Henley Beach South. The area became urban as houses were built; the creek was fenced off and used for the agistment of horses and little else.

In the 1990s, the Torrens Catchment Water Management Board now part of the Adelaide and Mount Lofty Ranges Natural Resources Manage ment Board, came up with a staged wetlands project for 1.2 km of the river. In 1999, 500m upstream from Henley Beach Road at Lockleys was made into a demonstration wetland at a cost of $550,000. Bulk earth works for the remaining 700m/10ha between Henley Beach and Tapleys Hill roads were completed in July, having taken three months. The existing waterway was widened and deepened so that two channels of open water flow around submerged islands of reeds (to be planted). At the time of writing (winter 2009), 40,000 out-of-water plants had been planted; in spring, 20,000 water plants will go in.

Connell Wagner, now part of the Aurecon Group, won the design, documentation and superintendency contract; and BMD e*3 won the construction contract. Greening Australia was tasked to grow all the plants, and is subcontracted by BMD to plant and maintain them for two years. Excluding tsemi tipper drivers, a peak workforce of 24 cut 60,000m³ of material; half was reused on site while the rest was reused off-site as it was excess to the design.

Equipment included four 7t to 33t excavators, two bobcats, 12 semi tippers, “an incredibly manoeuvrable” 25t articulated dump truck a GPS-controlled small dozer (to trim to level) and two 12t rollers. An 8” (20 cm) stationary pump and a variety of smaller pumps were used to control water levels. Project manager Sam Phillips says “the whole timing of wetland projects is to complete the earthworks in time to plant the plants at the right time of the year. The bulk earthworks and one of the two concrete weirs were completed when one of the big rains started. It was beautiful timing.”

A week was lost when Torrens Lake weir malfunc tioned on the night of February 11 and “let go” a slug of water flowing up to 1.5m deep through the site. A big rain event cost another week. Phillips says the horse fences have come down, the horses are further downstream and there’s a network of paths down to the water similar to the first stage.

“What was there before was not a biodiverse environment. We have removed more than 30 weed species,” he says. The new wetland will have grassed areas and viewing platforms, and a boardwalk crossing will connect the east and west banks. Like stage one, it will have permanent water and increase the habitat for native fish (arriving via a fish ladder at Henley Beach South), frogs and water birds. Expect koalas, too, as one was seen recently in the stage one area. Phillips expects the 1.6 km section from Tapleys Hill Road to the sea (now an agistment area) to become a wetland at some time in the future.