Assessing the environmental impact of coal ash disposal

Ash produced from the combustion of brown coal in Victoria's Latrobe Valley is currently slurried into ash disposal ponds for storage. Subsequent to a review of ash production rates at the Loy Yang Power Station, a number of options for ash pond management were considered. These included excavating the aged ash from the existing pond and then depositing them downstream of the pond or into a nearby overburden dump. Prior to the re-classifying of ash, analytical testing was generally conducted on a total concentration basis and did not consider the leachable fraction of various elements from the ash. The current study of ash leaching involved the collection and testing of ash in three states, aged ash, slurry ash, and fresh ash. The analysis confirms that the aged ash, deposited within the disposal pond for 6 to 12 months, has reached the steady state point and can be considered to have a low potential for adverse impact on the beneficial use of groundwater and surface waters when excavated from the pond and dumped at other locations. It should also be noted that batch tests, where the material is shaken overnight, represents a worst case scenario of leaching. Such vigorous mixing would not normally occur in the field and consequently the leachates produced in the field can be expected to have a lower salinity for a longer period of time. (author). 6 tabs., 10 refs