1 Executive Summary

This report is the result of independent review of the numerical groundwater modelling component of the Narrabri Gas Project (the Project) Environmental Impact Statement (EIS). Construction of the numerical groundwater model is deemed to be based on sound reasoning and consideration of background information, and is consistent with standard industry practice and relevant guidelines.

There is a lack of observation data used to calibrate the model parameters with the exception of the net flux to groundwater over the Naomi Alluvium aquifer. As a result, the selected model parameters are based on expert review of background information and as such, have greater uncertainty than model parameters calibrated to observation data. The key model parameters and predictive model stresses influencing predictions of groundwater impact, have a large level of uncertainty, which results in high uncertainty in the model predictions.

Andrea Broughton, Groundwater Solutions International

I am a Senior Hydrogeologist trading under the name Groundwater Solutions International as part of Gradient Limited. I worked for the formerly named Department of Water Resources, NSW, from 1992 until 1995 as a Project Hydrogeologist and was located in Gunnedah/Sydney. As a result of my work I obtained a good understanding of the hydrogeological processes that occur within, and between, the southern Surat Basin and Gunnedah Basin geological units, having undertaken an intense property-by-property three year study of bores. Data collected and reviewed included bore and well hydrographic and water quality records; geological records from both the bores, wells and mining exploratory bores; hydrological data from creeks and rivers; and climatic data. I ran educational workshops for property owners and government employees working in the area. Since leaving Australia I have reviewed groundwater impacts of mining operations at the request of community groups. I maintain a keen interest in respect to any hydrogeological investigations, and other relevant scientific studies, undertaken in the Namoi Valley Catchment.