DPI Update (Issue 55)
JOHN MITAS General Manager, Minerals and Extractive Operations, Chief Inspector of Mines and Quarries Earth Resources Regulation Branch comments on the Department of Primary Industry’s concern with the safety of small dams located on quarry sites.
RECENT heavy rains in Victoria following the prior extended period of exceptionally dry weather has resulted in attention being given to how industry manages its water resources including the storage of water in dams. Water stored behind a dam represents potential energy which can create a hazard to public safety, property and the environment. At all times the risks associated with the storage of water must be minimised.
In Victoria, an ongoing owner responsibility exists under Common Law to maintain dams according to “current standards”. Standards for large dams are set by ANCOLD and new, smaller dams are required to be constructed according to published guidelines. However, for many older small dams constructed prior to the current guidelines being released, reasonable precautions must be in place to protect the public and the environment from the effects of a release of any or all of the retained fluids behind the dam.
From February 2011 Inspectors from the Earth Resources Regulation Group will be conducting unannounced visits to mines and quarries sites to assess the effectiveness of dam management practices.
Th e objective is to ensure site management practices are effective and that risks are minimised. Where risks cannot be eliminated, physical control measures should be implemented to the extent that is reasonably practicable.
The overall operation and management system for a dam should include a process for inspection, maintenance and review. Programs should be based on the site specific conditions for each dam.
An audit tool has been developed for the project that will focus on management plans and systems at sites and is aimed at assessing site control programs with good management practices and compliance with work plan conditions.
A small dam is one less than five metres in height, i.e. from the base of its foundation with the natural ground to its crest. A small dam is also defined as one which retains not more than four metres of water depth and not more than 50 000 cubic metres of water.
The limitation on water depth provides for a minimum free board of one metre. Such a dam is also exempt from registration under the current legislation. Owners of dams larger than this, or of dams which represent significant hazards to life and/or property, should consult the ANCOLD “Dam Safety Guidelines” for information and procedures for the safe operation of their dams.
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