Ocean intake and outfall pipes for a potential large-scale desalination plant on Walsh Point would run under the Hunter River and Stockton before emerging in Stockton Bight, technical reports show.
In addition to discharging concentrated brine solution, the infrastructure could further complicate efforts to manage severe erosion on Stockton Beach.
Recycled water schemes, new dams, stormwater harvesting, groundwater and increased water conservation are among other options under investigation.
Walsh Point is being considered as the location for either a drought response or baseload capacity desalination plant.
A drought response plant, similar in size to the unit proposed for Belmont, could produce about 30 megalitres a day.
Such a unit would draw water from the ocean and discharge into the Hunter River. However, a larger plant would require direct ocean inlets and outlets.
Independent MLC Justin Field received several reports about a Walsh Point desalination plant as part of a call for papers into the Lower Hunter Water Plan.
Consultants WSP Australia prepared a desktop geotechnical report for a Walsh Point "desalination plant with an ultimate capacity of 160 megalitres a day" in July 2020.
It is estimated that such a plant could cost up to $500 million to take about three years to build.
The report shows two potential sites on the eastern side of Walsh Point and one on the northern end.
A separate feasibility study prepared by GHD notes that Hunter Water does not own the sites.
"Walsh Point sites are not owned by Hunter Water and would require long term leasing or purchasing arrangements with property owners," the report says.
"The most opportunistic site is owned by the Port of Newcastle at the southern end of Walsh Point."
The site on the southeast corner of the point shows two pipes running from it under the river and Stockton and into the ocean to illustrate how a potential large plant would receive and discharge water.
The area under consideration for inlet and outlets falls within zones 6 and 7 of City of Newcastle's Coastal Management Plan for Stockton Beach.
Zone 6 extends from the northern boundary of Corroba Oval to the southern boundary of Fort Wallace. Hunter Water already owns most of the land in this area. Zone 7 extends from the southern boundary of Fort Wallace to the Newcastle local government area boundary.
The report notes the area under consideration has been identified for intensive coastal protection under the coastal management plan.
"Given the predominant sediment transportation pathway in the Stockton Bight, the area between the north end of the seawall and Fort Wallace are proven to have high turbidity levels. Sand replenishment or recharge is the preferred option from the community for recovering the beach. A groyne field is also under consideration," the report says.
It also notes the impact of turbidity caused by dredging.
"The constant dredging of the channel and dumping of sediments can affect the water quality along the study area. Although, this would be a short-term impact, it should be reviewed before placing the intake for the desalination plant."
"Dredging can also release contaminants into the water column which has the potential to change chemical properties of the sediment and reduce water quality at both extraction and dumping sites for a short-term after dredging has ceased."
IN OTHER NEWS:
Hunter estuary flood plumes could also impact on water quality.
"It will be critical that the strategy for the proposed plant considers these weather induced high turbidity events in the design of the pre-treatment system and the operational planning for managing water production during 'flushing events...," the report said.
Hunter Water will release in March the results of community and business feedback gained during the Lower Hunter Water Security Plan review process. A draft of the revised plan is due to be released mid-year.
A Hunter Water spokesman said no decisions had been made about the preferred portfolio of options in the revised plan, with all options on the table for consideration and assessment.
"As with each of the shortlisted demand and supply options under the Lower Hunter Water Security Plan review we have carried out high-level, desktop studies into potential locations for a desalination plant at Walsh Point to provide an understanding of the feasibility of desalination options," he said.
"Desalination is being considered at a range of sizes and as both an ongoing baseload water supply option and an emergency drought response measure at the site next to Belmont Wastewater Treatment Works and the potential locations at Walsh Point."
"More extensive environmental assessments, as well as technical investigations such as geotechnical and marine studies, would be required should any major infrastructure option be included as part of the final plan, but no decisions have been made about which options will be included."