Inspire : Public Works Professional Sept - Oct 2013
24 Public Works Professional September-October 2013 ECO ENTERPRISE "All major works had to be completed and the site reinstated by mid-December to allow full public access during the busy summer period," says Council Project Manager, Corey Fox. But time constraint wasn't the only issue, recalls Fox. "We had to work on a site that hosted a maze of underground services, including a network of inter national submarine fbre optic cables. Needless to say, you have to tread pretty carefully around obstacles like that -- especially when you're driving an augur bore right alongside them!" RELIABLE SUPPLY SOURCE The main off-take for the Bondi stormwater scheme is from a large Sydney Water Corporation (SWC) junction pit, at the southern end of the park, which receives water from the 115-hectare Bondi South catchment. Water fows at a rate of four litres per second into this pit and, after passing through SWC gross pollutant traps, is conveyed via a single-trunk drain for discharge at Bondi's southern shoreline. The Bondi stormwater scheme draws water at the rate of two litres per second from this source. However, it also handles polluted run-off from Campbell Parade -- the busy tourist strip that runs the length of Bondi Beach. For this run-off, the system uses Hydrocon porous pipe fltration technology to remove heavy metals, hydrocarbons and phosphorous. A bio-retention garden was originally planned to isolate and treat the Campbell Parade r un-off, but at the time of construction, a master plan for Bondi Park was still under review, so the underground Hydrocon fltration system was designed as an alternative to better manage the water. Not only does this work to improve the water quality at Bondi Beach, it has also improved system operation by reducing oil content in the har vested stormwater, which was fouling the backwash screen. DISINFECTION FULLY AUTOMATED The Bondi stormwater system uses grinder pumps to har vest water, which is then subjected to 100-micron backwash fltration and UV treatment. The system is fully automated with 24/7 inline monitoring of UV transmission rates to ensure effective disinfection. According to Fox, the monitoring of UV transmission was chosen over turbidity measurement because an earlier stormwater-har vesting project at nearby Bronte Beach had demonstrated there was little correlation between turbidity levels and UV kill-rates. The system incorporates state-of-the-art technology with telemetry control, which enables staff to remotely manage it using a smartphone application. Built with support from the NSW Government's Climate Change Fund, the scheme is delivering signifcant cost savings for Waverley Council. It also had community support from the outset, with the council keeping residents and visitors constantly in the loop via explanatory signage, Web updates, newsletters and bulletins. ••• The site hosted a network of bre optic cables. Needless to say, you have to tread carefully when you're driving an augur bore right alongside them!
Public Works July Aug 2013
Public Works Nov Dec 2013