69 



As a general observation, the closer the Empress piezometer is to the reservoir, the 



larger the decrease in water levels have been from 1983 to 1991. There appears to be 

 less of a decrease beneath rather than around the lagoons. This may be due to upper 

 horizon influences such as leachate movement or pore pressure or the water mound on 

 the east of Ash Lagoon No. 3 North. 



The boron and chloride results for the Empress layer do not indicate significant changes. 

 The largest change in boron near the lagoons is 0.48 mg/L. 



Leachate movement was also reviewed at piezometer C71 2B in the intra till sands on the 

 north side of the polishing pond. Boron levels continue to show an increasing trend 

 (Figure 7.14) and chloride results have been steady over the last several years (Figure 

 7.15). A slug of leachate is probably affecting this piezometer rather than a continuous 

 plume. Comprehensive monitoring should continue at this location. 



7.9 Ash Surcharging 



From October 26, 1991, to November 16, 1991, the dykes on Ash Lagoon No. 1 were 

 built up making room for future ash stacking operations. Most of the activity during this 

 period was concentrated at the south end of the lagoon, and the south half of the east 

 ash dyke. The ash dykes in these areas were raised about two metres. 



