Following extensive research and investigations undertaken in conjunction with the Department of Environment and Science (DES), ponded water contained on the Sunshine Coast Airport Expansion Project site will be released to the ocean.
The region experienced above average rainfall from March to June this year, leading to significant volumes of water ponding across the site.
Deputy Mayor and SCAEP Project Control Group Chairman and Finance Portfolio Councillor Tim Dwyer said council had taken the most cautious and environmentally responsible approach by containing the water on site whilst reviewing all available options.
"The release of ponded water from the site direct to the ocean is the optimum solution, as it ensures the stored waters are released at a much greater rate, whilst minimising any potential impacts," Cr Dwyer said.
"Importantly, the ocean release proposal is supported by DES as being safe for humans, fish species, animals and the environment.
"Surface water and any extracted groundwater will be tested by a qualified and experienced company, and, if required, treated in an onsite water treatment plant to ensure it is below the PFAS National Environmental Management Plan (NEMP) levels, prior to its release.
"These actions are consistent with the prudent and responsible approach council has taken with this project since day one, and ensures that we are delivering the best solution for the project and for our ratepayers, whilst ensuring we are acting responsibly in terms of our environmental obligations.
"Council is committed to going the extra mile and exceeding requirements. The contaminant concentrations of the water at the release point will be almost 200 times below the allowable level.
"DES considers this to be the most responsible solution as part of our multi-faceted approach and an outcome which not only lowers the risk of bio-accumulation, but also minimises the impact of the alternative release of fresh water into an estuarine environment."
The fresh water will travel to the sea via an underground pipeline which will be installed approximately 4.5 metres under David Low Way and then extend under the dunes, the beach and the seafloor (at a depth of 12 to 14 metres) to reach 400 metres east of the Lowest Astronomical Tide (LAT) mark.
The pipe outlet will protrude approximately 50 centimetres above the sea floor at a depth of about 10 metres below the LAT level. It will not be visible from the beach.
This installation will not impact the beach and dune in any way.
The pipe will be installed by early October and be operating in mid-October.
The cost to establish the pipeline is estimated to be in the vicinity of $2.5 million, although final costings are being determined. The project budget includes allowance for latent conditions such as those encountered in this instance.
Council will fund the cost of the pipeline within the Airport Expansion project budget allocation.
The Airport Expansion project is funded from borrowings which will be repaid in full when council receives the final project payment from Palisade Investment Partners in July 2022. There will be no enduring cost to the ratepayer from the delivery of the new runway or the installation of this pipeline.
Up to 8 mega litres (ML) of water will be pumped through the pipe per day, allowing the currently ponded water to be removed from the site within 20 days, weather permitting, and also allowing future average rainfall events to be discharged within 24 to 48 hours for the remainder of the construction period.
Cr Dwyer said that much of the water had runoff from the vegetation areas in the adjacent national park, and, when released, may have a tannin stain.
"Typically, when freshwater is mixed with sea water, a foam can form in the mixing zone, particularly if there is significant wave action," Cr Dwyer said.
"While this foam may appear brown in colour, council is advised there is no health risk.
"Council wants our residents to be informed of this process and to understand what it will entail.
"Council is taking a responsible approach to this matter and is working closely with all relevant authorities.
"We are satisfied that this ocean release process demonstrates we are taking the most prudent action – environmentally, socially and financially."
Cr Dwyer said while delays had been experienced, the most recent fine weather had allowed work on the new runway to resume in earnest and council had continued to work with the contractor to mitigate delays.
Based on advice from the contractor, the Airport Expansion project remains on track to be completed by Christmas 2020.
