Groundwater injection plans not ruled out

Gosford Council has not ruled out the possibility of adding high quality recycled effluent from Woy Woy sewage treatment plant to groundwater on the Peninsula.

The Council resolved to "note the progress being made on the water recycling strategy and drinking water substitution projects".

However, a council spokesman told Peninsula News last week: "The use of recycled water as a salt water intrusion barrier for the Woy Woy borefield was raised in conjunction with 30 other options proposed to the Gosford Wyong Water Authority for consideration to assist with drought management contingency plans.

"However, this proposal is not considered necessary for the borefield scheme presently being implemented," he said.

A report to Gosford Council's Strategy Policy Workshop stated that "recycled water" from the Woy Woy sewage treatment plant could be injected into the Woy Woy aquifer to prevent sea water intruding into the aquifer, under a medium to long term project currently being considered.

It could also increase the yield from the borefield.

The project had been identified by council as part of an Integrated Water Cycle Management Strategy which it said had the potential to supply a "significant volume of water to the region".

Peninsula News submitted a number of questions to council staff on Friday about the status, process and consequences of implementing the project.

"A more detailed response to questions raised by the Peninsula News can be provided early next week should you wish to defer publishing the article," the spokesman said.

The "Water Sustainable Seawater Barrier Scheme" involves the injection of recycled water from the Woy Woy sewage treatment plant into the Woy Woy aquifer, according to the report to Council.

This was designed to prevent seawater intrusion into the aquifer, providing "up to 100 per cent additional flow from the ground water to the drinking water supply system".

The report stated that the aquifer was a "shallow unconfined sand aquifer".

"A drinking water project is underway to extract the freshwater from this aquifer to augment the Gosford potable supply.

"The sustainable yield for the drinking water project is four megalitres per day.

"The sustainable seawater barrier scheme consists of a series of injection bores around the perimeter of the freshwater aquifer.

"Recycled water will be injected into the salty-freshwater interface to create a barrier to prevent seawater intruding into the fresh drinking water aquifer.

"This project provides an additional three megalitres a day to the sustainable yield of the drinking water extraction scheme.

"Preliminary hydro-geological modeling has been undertaken and indicates that the groundwater flows towards the saltwater perimeter of the aquifer, consequently it is unlikely that the recycled water will be drawn back against the hydraulic gradient towards the drinking extraction bores, however further modeling is required."

Council reported that the cost of the project would be $26.6 million.

Other schemes being considered are located at Bateau Bay, Toukley, Warnervale, Charmhaven and Wyong South.

Other schemes include a water factory flow substitution at lower Wyong River, a Gosford CBD water mining demonstration project, the Kincumber Dual Reticulation Scheme, the Niagara Park Stormwater Harvesting Scheme and the Terrigal Water Mining Scheme.

The schemes all fall under council's Central Coast Water Recycling Proposal.

The report from council staff stated that the Gosford and Wyong Water Authority were in the process of completing an integrated water cycle management strategy that had identified a "range of potential options" for meeting a shortfall in water availability.

It stated: "A key component of this strategy is the increased use of recycled water.

"A number of potential projects that could be developed in the short to medium term have been identified that could significantly increase the level of water recycling in the area."

The report was provided as part of an update on the status of water recycling and other demand substitution projects operating, underway and planned for the Gosford Council area, at its strategy and policy workshop held on February 20.

It stated: "Water recycling is anticipated to be a major component of Gosford's Integrated Water Cycle Management (IWCM) strategy.

"It is important that the water recycling strategy and individual projects are developed and communicated in the context of IWCM and that sustainable outcomes are achieved."

Council agenda SF.2, March 27