Update on the Anglesea Borefield

Update on the Anglesea Borefield

Friends of the Barwon Committee members were recently briefed, by both Barwon Water and the Friends of the Anglesea River, about issues affecting the Anglesea River and its estuary. In recent times the Anglesea River has experienced prolonged periods with low pH levels, to the detriment of the biodiversity in the waterway. Although the exact cause of this has not been fully settled, the Friends of the Anglesea River suggest a potential cause is an 80% – 90% reduction in flow in Salt Creek over the last 60 years. They claim the reduced flow is evidence of an unacknowledged vertical leakage from the perched aquifer above a cone of depression which underlies the Alcoa mine after 46 years of dewatering pumping.

Alcoa, who ran the coal mine at Anglesea, have plans to pump water from the Upper Eastern View Formation (UEVF) to contribute to the rehabilitation of the mine site. This is being considered in conjunction with the Eden Project. Previously, water was taken from the UEVF to help the cooling process in the associated power station and returned to the Anglesea River. This amounted to 1.6 GL each year. Now the mine and power plant are no longer in use this water is not being returned to the river.

Barwon Water have a Bulk Entitlement for water in the Lower Eastern View Formation (LEVF). The LEVF is separated from the UEVF by the Middle Eastern View Formation that acts as an aquitard between the two aquifers. It was indicated that pumping would only occur as a last resort in the event of serious water resource challenges such as occurred in the Millenium Drought. In these cases, water from the LEVF would be piped to the Wurdee Buloc Reservoir to supplement Geelong’s water supply. The current conditions allow for 40 ML/day and 10 GL/year to be piped with a maximum amount of 35 GL in a period of five years. Unlike the Barwon Downs Borefield which was used during the Millenium Drought, where a volumetric licence was given, the extraction from the LEVF is regulated by DEECA under a bulk entitlement. Extraction will be strictly monitored to ensure there is no adverse effect on the environment from the pumping. The Monitoring and Assessment Program (MAP) will cover aspects like ground water level, ground water quality (salinity, pH, temperature and sulphates), aquatic and terrestrial ecology, stream flows and levels as well as rainfall. This information will be used to assess impacts on both aquifers. Barwon Water is developing a hydrogeological model which will be used by them and Alcoa in their respective applications for pumping rights. Alcoa are obliged to contribute their data to ensure the model is robust.

It is expected given current water storage levels in the region it will be some time before Barwon Water uses the Anglesea Borefield to supplement Geelong’s water supply. Barwon Water is also increasing the reach and capacity of its Melbourne to Geelong Pipeline supply, which will improve short to medium water security for the region.  In the meantime, it was reassuring to see the amount of work being undertaken to ensure the environment is protected and, if changes occur through the Environmental Monitoring Plan, they can be detected before compounding the situation in the river. Hopefully in the interim, headway will be made on the use of recycled water to augment our potable water supplies and the borefield will not be needed. Alcoa is still progressing their licence application to use water from the UEVF to rehabilitate the mine-site but approval is not guaranteed. Barwon Water have offered an alternative solution using A class water from its Black Rock treatment plant. Alcoa have rejected this offer on the basis of costs involved.

By Trevor Hodson, FOTB Chair

Photo: Water monitoring in the Anglesea River. Courtesy of Estuary Watch