​What information is needed?

LWU’s should assess as much information available, as described below, to better understand their sources. Depending on the aquifer type, not all the information may be needed to make a determination. The information compiled should be used to answer key questions about the potential health risks from groundwater:

• How does the aquifer get recharged? What type of aquifer is it? Is there any hydrogeological evidence that the aquifer is confined and sufficiently protected from downward flow?
• Are there pathogen risks in the predicted recharge area for the bore?
• How much protection from surface influence is provided by the soil and rock overlying the aquifer?
• Do bore construction details and casing integrity condition prevent cross-contamination by water ingress from surface and other water-bearing zones to the target aquifer?
• Is water from the bore usually low in turbidity and have there been reports of dissolved material that might interfere with effective disinfection?

If limited information is available to inform the level of protection of the groundwater source, the water utility should consider engaging an external contractor to gather the outstanding information and assess the level of risk from pathogens. Potential activities can include downhole inspection, aquifer testing or hydrogeological assessment, potentially also including a predictive contaminant transport and decay model where relevant. 

Utilities should share reports from such investigations with their local Public Health Unit, along with their self-assessment of the level of protection of the groundwater source and associated risks. There may be benefit in some cases for the LWU to conduct a dedicated risk assessment, with the Department of Climate Change, Energy, the Environment and Water and Public Health Unit participation, into which the compiled information could feed.​

Bore details

Parameters of interest

• Total depth
• Depth to top of screens
• Screened interval length
• Presence of a grout seal above the screens
• Current bore state (overall, casing integrity, protective bore head presence and integrity)
• Age/history of repairs/ maintenance

Possible source of information

• Drilling and construction logs
• Downhole inspection reports
• Bore rehabilitation reports
• Utility records

Hydrogeology/ geology

How much protection from surface influence is provided by the soil and rock overlying the aquifer?

Parameters of interest

• Aquifer name and material
• Confined/ partially confined/ unconfined
• Permeability, transmissivity
• Depth to groundwater; does this change in response to rainfall?
• Depth to top of aquifer and aquifer thickness
• Soil type and thickness
• Predominant material in the vadose (i.e. unsaturated) zone

Possible source of information

• Hydrogeological investigation report
• Drilling logs for this and nearby bores
• Aquifer testing report
• Geophysical studies
• Australian Groundwater Explorer from Bureau of Meteorology​​​

Pumping regime

Parameters of interest

Seasonal / year-round, and pumping rate

Possible source of information

Council utility manager & operators

Groundwater vulnerability

Parameters of interest

• Existence of an established wellhead protection area (WHPA)
• Town water supply groundwater vulnerability assessment and index
• Evidence of groundwater-surface water interaction

Possible source of information

• Utility wellhead protection planning
• Modified DRASTIC index and Land Use index from DCCEEW’s Town Water Supply Groundwater vulnerability assessment framework and tool
• Hydrogeological investigation reports

Water quality information

Parameters of interest

• Radiological activity
• PFAS concentrations
• Indicators of faecal contamination
• Inorganic chemical concentrations
• Physical characteristics, how do these characteristics change in response to rainfall?
• Pesticide concentrations

Possible source of information

• Gross alpha and gross beta screening (NATA accredited)
• NATA accredited laboratory test
• NSW Health Pathology groundwater investigation project

New bore testing guid​ance

Samples should be collected when field tests such as pH and temperature indicate that water being pumped from the bore has settled to consistent quality. This water should be representative of the aquifer from which the bore is drawing.

Collect samples for:

• E. coli and total coliforms for testing by NSW Health Pathology
• the regular inorganic chemistry suite by NSW Health Pathology
• gross alpha/gross beta screening through an appropriate laboratory
• pesticides through NSW Health Pathology, where indicated by the risk assessment
• PFAS through a laboratory that can test to below the Australian Drinking Water Guideline values, where indicated by the risk assessment
• other organic compounds as identified through risk assessment e.g. hydrocarbons where there is a risk of contamination from fuel storage, where indicated by the risk assessment

A wider range of inorganic characteristics can be tested by NSW Health Pathology if indicated by the risk assessment.