68 



lagoon chloride levels. A waterfront may be moving through this area ahead of a 



leachate front. 



There has been little change in boron or chloride levels for most of the oxidized till 

 piezometers located by the reservoir. The only significant change in any of these 

 piezometers has been C719 where chloride levels have decreased to 87 mg/L. The 

 calculated groundwater movement in the oxidized till from the polishing pond to the 

 reservoir is about 18 metres from 1981 to 1991. This is theoretically not yet far enough 

 to affect this piezometer. 



Like for the oxidized layer, a groundwater mound has also developed for most of the 

 unoxidized till piezometers extending from the east side of Ash Lagoon No. 2 to the west 

 side of the polishing pond. The size of mound does not extend as far as the oxidized 

 layer and not all unoxidized till piezometers are affected. For example, unoxidized till 

 piezometer C764D is located within the mound area but has historically reacted to the 

 reservoir and is showing a decreasing level. An examination of the boron and chloride 

 levels does not indicate any distinct trends. 



The piezometric surface of the Empress gravels indicates a regional flow from west to 

 south east below Morrison Dam. Around the lagoon area, there is a noticeable drop in 

 piezometric head at the east side of Ash Lagoon No. 2. There is also an increasing 

 mound at the east end of Ash Lagoon No. 3 North. 



