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Mining of coal by TransAlta from around Lake Wabamun has been ongoing since 1962. Currently, TransAlta removes approximately 14.6 million tonnes of coal per year from both the north and south sides of Lake Wabamun. During the actual mining process, water is pumped from the pits in order to dry the coal out and permit safe working conditions.
Prior to mining at Whitewood Mine on the north side of the Lake, the water table in the area must be lowered. This is accomplished through a process called dewatering. Essentially water wells are drilled ahead of the mining process and the wells are pumped continuously in order to dewater the water bearing zones both above and within the coal. Water from the north side of the Lake is diverted to the catchment area to which it would naturally flow. If the water normally flowed to the south, the water is diverted towards the Wabamun Power Plant via ditches, which ultimately lead to Lake Wabamun. If water normally flowed to the north, it is being pumped into the Lake Isle/Lac St. Anne water shed. In 2001, 626,000 m3 were pumped to Lake Wabamun and 1,560,900 m3 to Lac. Ste. Anne watersheds, respectively.
Post mining groundwater monitoring indicates that water levels are returning to their pre-mining elevation which is a positive indication that the mining will not have long term implications on the local groundwater regime.
On the south side of the lake, mine dewatering occurs as each mine pit advances to the south. Interceptor ditches divert surface water around the pits and into Lake Wabamun. Surface and groundwater inflow into the active mining area is diverted to the Sundance cooling pond, due to its silt content, for settling. In 2001, 4,200,900 m3 was diverted to the Sundance cooling pond.
All of the mine related dewatering south of the Wabamun Lake has an impact on Lake Wabamun. This impact is accounted for in the water balance calculation that TransAlta is required to do by Alberta Environment.
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