Engineers Australia

Impacts of longwall mining and coal seam gas extraction on groundwater regimes in the Sydney Basin: Part 2 – Practical applications

S. E. Pells and P. J. N. Pells

Abstract

Part 1 of this paper presented simple equations for transient and steady state downwards flow in saturate and unsaturated ground that are considered to be useful in understanding flow and pressure regimes above extensive areas of longwall mining and coal seam gas extraction. This Part 2 paper presents filed data from longwall mines in the Sydney basin and relates the data to findings from Part 1. This part also analyses how different views have been expressed in relation to impacts of longwall mining on groundwater regimes and proposes that these differences have largely arisen out of poor differentiation between seepage flows and pressures.

The field data presented in this part support a finding of Part 1, namely that the question that should be asked in respect to groundwater impacts from longwall mining, and CSG extraction, is not “if” impacts will occur, but “how long” will they take to occur.