The environmental regulation of a coal mine in the greater Sydney area has failed to recognise the importance of and protect a high conservation-value river located in a World Heritage listed area. This study measured the water quality and ecological health (using macroinvertebrates) of the Wollangambe River and its tributaries near the point of the waste water discharge of a coal mine and assessed the longitudinal impact for 22 km downstream. The investigation revealed two important aspects. The first is the significant impact of the waste water discharge when compared to the otherwise near-pristine condition of the high conservation-value river system. The second is the spatial extent of the pollution from the mine that extends at least 22 km downstream from the outflow of coal mine wastes. The resulting water pollution is causing major impairment of the aquatic ecosystem, with reduced abundance, taxonomic richness and loss of pollution-sensitive macroin-vertebrate groups. Water pollution from the mine includes thermal pollution, increased salinity and increased concentrations of zinc and nickel. The mine's waste discharge also strongly modified the river's ionic composition. The study also highlights the failure of the regulatory and governance systems that enable the mine to operate in a manner that causes major environmental impacts.