GM³ was contacted through its Appin community contact line by a Menangle resident regarding an odour and surface water emergence at Navigation Creek. Investigations have indicated the issue is related to the interaction of sandstone strata gas and groundwater with an historic exploration borehole located adjacent to Navigation Creek. GM³ is working closely with the landholder and has commenced remediation works to manage the issue as of Tuesday, 28 April. Updates will be provided as more information becomes available.

Investigations indicate the discharge is coming from a historical exploration borehole (dating back to the 1950s) located near Navigation Creek.

Natural gas and groundwater within the surrounding sandstone layers have found a pathway to the surface through this borehole. Ground movement in the area, including subsidence associated with longwall mining, is considered a contributing factor.

Importantly, the gas itself is naturally occurring in the rock strata and is not being generated by current mining activities

Water emergence and gas detection has been identified in Navigation Creek near an historic exploration bore, located on private property adjacent to Burrells Road and Quirkes Lane, Menangle.

The water discharge is currently being contained and isolated in a downstream private property dam. No discharge has occurred further downstream of this dam.

Gas detection is localised to the immediate source area at the historic borehole site.

An exclusion area has been established as a precaution.

GM³ would like to reassure nearby residents, with precautionary controls and monitoring in place, there is no risk to public health or safety

Ongoing monitoring shows the gas is primarily methane and carbon dioxide, which are naturally occurring in underground rock layers.

Very small amounts of other gases (trace hydrocarbons, less than 0.1%) have also been detected. These trace gases are likely responsible for the occasional odour that may be noticed.

Water monitoring shows that the quality is generally consistent with natural groundwater from the Hawkesbury Sandstone, and testing is continuing in consultation with the EPA.

The water is currently being contained within a downstream dam, where it is settling and diluting, which limits movement further along the creek.

During the day, groundwater from the creek is also being actively extracted and transported offsite, further reducing the volume remaining in the creek.

Based on results to date, landholders downstream of the dam have been advised that normal water use can continue. Monitoring and management will continue as remediation works progress

Water samples were collected to assess salinity and any broader water quality impacts; the results are generally consistent with the quality of Hawkesbury Sandstone groundwater. GM3 has implemented sediment controls and will continue to monitor the creek to validate current findings.

Based on current monitoring:

• A large dam within Navigation Creek is containing the discharge, preventing it from moving further downstream
• No impacts are expected downstream of Cummins Road.
• For landholders within the section of the creek directly impacted by the discharge, GM³ is providing an alternative source of potable water as a precaution as water quality testing continues.

GM³ will continue to monitor water quality and site conditions closely and will provide updates should conditions change.

Note: the groundwater is from the Hawkesbury Sandstone aquifer. Groundwater from the Hawkesbury Sandstone is routinely used by landholders in the local area for livestock and agricultural/gardening purposes.

GM³ has implemented a range of precautionary measures, including:

• An exclusion zone around the affected area
• Noise and screen blankets
• Ongoing gas and water monitoring
• Sediment and erosion controls
• Traffic management and signage
• Continued onsite presence and inspections

Preparation works, monitoring and investigations have been ongoing since the issue was reported. Controlled works at the borehole have commenced as of Tuesday, 28 April during standard operating hours (7:00 am to 5:00 pm). If work is required outside standard hours, residents will be advised where practicable.

Initially, these works aim to manage the borehole and safety stabilise the area ready for final borehole sealing using a small drill rig. This will involve machinery and increased activity onsite.

The duration is not yet confirmed, as works involve a historic borehole with limited records, requiring careful investigation.

GM³ will continue to provide updates as more information becomes available.

There may be temporary changes to access, including:

• Short-term road closures near Quirkes Lane
• Traffic management in place
• Continued access for residents and emergency services
• Truck's turning around at the intersection of Burrells Rd and Quirkes Ln

GM³ will work directly with landholders to minimise disruption.

We are working closely with Wollondilly Shire Council with our Traffic Management Plans.

GM³ have implemented erosion and sediment controls in consultation with the EPA.

You can stay updated by following this page, where we will provide updates as new information becomes available.

If you would like to speak with someone directly or have specific questions, you can contact our Community Team at:

• 📞 1800 102 210 (available 24/7)
• 📧 community@gm3.au

We are also available to meet with residents upon request