Alteration of habitat following subsidence due to longwall mining has been formally listed as a key threatening process under the NSW Threatened Species Act. The final ruling was made following a preliminary ruling by the NSW Scientific Committee in November 2004 and a public submission period.

NSW Scientific Committee chair Lesley Hughes told International Longwall News more than 30 submissions were received during the consultation period, including those from coal companies.

The DEC is currently deciding whether to implement new measures to reduce subsidence threat to habitats or whether existing measures are sufficient.

“The threat abatement plan will try to put into place practices that will reduce the threat to threatened species and communities in the future of that particular process – in this case subsidence due to longwall mining. Potentially that could mean more environmental compliance measures,” Hughes said.

She said the plan was consultative, with the DEC in talks with various stakeholders, including coal companies, environmental companies, community groups and the NSW Department of Primary Industry.

“The immediate impact is very little except they [coal companies] need to be aware there has been a scientific body that has looked at the available evidence for the impact and has found there are problems,” she said.

Although no firm date of when the plan will be released for public submission has been confirmed, typically, similar plans take at least one year to complete.

The ruling specifically targets mining under water where subsidence can cause cracking of valley floors and creek-lines, which affects surface and groundwater hydrology.

The Scientific Committee report last year cited a long list of water courses that had substantial damage from subsidence including North Wambo Creek, Upper Nepean, Cordeaux and Cataract catchments.

It referred back to perhaps the most notorious subsidence case at South Bulli, where cracking of the Cataract riverbed caused the river downstream of mining to dry up. Water that re-emerged downstream was notably deoxygenated and heavily contaminated with iron deposits.

Other cases named included the Georges River affected by the West Cliff longwall and the Wongawilli Creek affected by Elouera.

The committee said mitigation measures, specifically grouting, to repair cracking creek beds had experienced limited success.