The Plains Hydrology and Reclamation Project , an interdisciplinary study of rock-water interactions in reclaimed landscapes, completed five years of research in 1984. The geology , soils, hydrology, and hydrogeochemistry of two sites in the plains region of Alberta have been intensively studied both in unmined and reclaimed settings. Although project studies are continuing, several significant findings have emerged.
Large amounts of soluble salt are liberated in mined landscapes, primarily from pre-existing secondary salt in the soil zone but to a lesser extend from weathering of fresh overburden. Solution of this salt results in spoil water 3 to 7 times more saline than premining groundwater . Chemical equilibrium constraints related solution of all the available to the abundance of calcium preclude salt thereby preventing extremely high salinity but extending the period of time over which water of elevated salinity is present. Prediction of salinity and chemical composition of post-mining groundwater has become possible with considerable accuracy using aqueous extract data from overburden in conjunction with the chemical equilibrium model PHREEQE.
Spoil contaminated groundwater has been found in aquifers as much as 1.5 km from reclaimed areas. The only other significant offsite effect anticipated is the potential for soil salinization or saline seep development in favourable settings.
No evidence of soil salinization as a result of groundwater discharge has been found in reclaimed areas. Studies are continuing to assess the potential for salinization from surface ponding in depressions created by differential subsidence of the spoil and from shallow water table conditions. Management of post reclamation surface hydrology to minimize groundwater recharge appears the most promising approach to long-term prevention of salinization.