NORTH QUEENSLAND also interconnected the Tully and Nyleta schemes at Mission Beach which allowed the diversion of more clean water into Mission Beach from this source and keeping more of Mission Beach off boil water when the Tully supply scheme was affected. There have been some lessons learned in relation to the works. Council did have problems with the operation of the bore pumps. The relatively shallow filters did not provide adequate submergence to the bore pumps, and it was necessary to set up a vacuum within the bore pump casings to improve pump output. The sand bed filters can clog over time, but Council has found that by using the Nyleta Creek pressure and backfeeding through the intake manifold it can flush the sand bedding. Council also installed 50 micron pressure screens before the reservoir but the benefit of these filters is minimal although they do keep out some of the sand material that passes the 250 micron screens at each intake. Costs associated with the Nyleta scheme water quality improvements are: • Design and preparatory works for the new reservoir including bulk earthworks, slope stabilisation works, concrete access road, and approach water mains $2.3M • 3.3 ML concrete reservoir with aluminium roof $1.9M • Ergon Connection $155K • Chlorination building and dosing facility $258k • Sub bed filtered intake and pumping system and associated electrical and civil works $0.95M • 50 micron pressure filters and enclosure $145k. Council recognises the assistance of the State Government which provided funds of $3.7M through DILGP grants to assist with these costs. In 2017/18 Council started the planning for improvements to the Tully and Cardwell supply schemes.
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South Liverpool Creek Intake - Sectional Elevation – Inclined bore pumps.
South Liverpool Creek Intake - Manifold pump housing.
Water Quality Improvements to Cardwell Water Supply Scheme Meunga Creek is the water source for the Cardwell Water supply scheme area. The intake for this scheme is located well inside the National Park and a 300 mm pipe delivers the water some 18.2 km to reservoir storages in Cardwell. Council had initiated the drilling of two bore sites outside the National Park area in the hope that the water from these sources could be used to supplement or replace the Meunga Creek supply when it was affected by turbidity or low flows in drought conditions. The water quality from one of the bores was unacceptable
ENGINEERING FOR PUBLIC WORKS | SEPT 2021
for consumption but the other bore proved to be reasonable. The only issue was a marginally low pH but all other parameters were excellent. Council then progressed the development of the bore including sizing and installation of the pump, disinfection system, pH correction and a control building. In addition to developing the bore, Council also installed turbidity analysis monitoring equipment near the Meunga Creek intake as well as auto isolation valves, all connected to SCADA. When Meunga Creek was impacted by turbidity greater than 5 NTU, the pipeline from the intake would be automatically shut and the bore started. A valve
