The New South Wales Department of Infrastructure, Planning and Natural Resources released the Flood Study this week fulfilling one of 112 conditions set for the project’s approval.

Condition 67 - a Flood Study - needed to determine the 1-in-100 year flood level for the Mandalong Valley and define present and future flood hazards resulting from mining. The majority of the proposed underground mining area is located within the Mandalong Valley drainage system.

The flood study used hydrological and hydrodynamic models to produce a description of flood behaviour.

In addition, airborne laser scanning surveys were undertaken for the entire Mandalong Valley, providing a grid containing some 12 million data points. This high resolution data allowed further refinement of the network to incorporate additional detail into the definition of the landform and specific features such as houses, access tracks and creeks.

The report found that only four structures were vulnerable to flooding in the event of a 1-in-100 year event.

In addition, the models developed for this study were used to assess the effects of subsidence from longwalls 1 and 2. Since its completion the mine plan has been refined as further geological knowledge has been gained from ongoing exploration. The result is the design of the first two longwall panels has been narrowed from 250m to 125m with expected subsidence projected at a maximum of 250 mm.

The model indicated that flood levels would be lowered by up to 180 mm and that flood levels adjacent to structures would be lower than or equal to the existing conditions in all cases.

“As required by Condition 67 of the Minister’s approval for expansion of the mine, this study provides a robust analysis of the 100 year ARI flood and further definition of the flood hazard characteristics of the floodplain,” the report said.

Mandalong Progress Association, a group opposing the mine development, yesterday described the result as a "deplorable process" The Newcastle Herald reported.

Centennial's projected start date of January is looming and the public has until December 15 to comment on the flood study. The Mandalong community has indicated this won't be adequate time to review the flood study.

Throwing in his two cents last week, Andrew Fowler of the ABC's Investigative Unit reported on Friday the New South Wales Government has a vested interest in getting the mine to produce on time.

“With the state facing increasing demand for electricity there's pressure to keep the power station furnaces stoked,” Fowler said.