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used to detect leachate movement and calculate seepage rates. In 1992, 15 new piezometers were 



installed to obtain additional information on leachate effects and seepage from the ash lagoons. 



The piezometric surface for the oxidized strata shows a ground-water mound that has developed 

 beneath the ash lagoons. The ground-water mound extends from the east side of Ash Lagoon No. 

 2, where a 6-metre increase has been noted, to the west side of the Polishing Pond, where levels 

 have increased about 4 metres. The new oxidized-till piezometers installed along Dyke B confirm 

 the ground-water mound that has developed. The oxidized-till piezometers closer to the reservoir 

 have shown a decreasing trend in piezometric levels reacting to lower reservoir water levels. 



The largest changes in chloride and boron concentrations have occurred where the water levels 

 have changed the most. This would be expected because changing water levels suggest leachate 

 movement. Increasing boron concentrations on the east and south sides of Ash Lagoon No. 2, 

 together with decreasing chloride concentrations, suggests leachate influence. On the west side of 

 the Polishing Pond, boron concentrations have not changed significantly. 



Little change in boron or chloride concentrations has been noticed in samples from most of the 

 oxidized-till piezometers located by the reservoir The only significant change in samples from any of 

 these piezometers has been at C719 where chloride concentrations have decreased by 96 mg/L 

 since 1983, to a concentration of 14.7 mg/L in 1992. This piezometer is beside the reservoir and the 

 change in quality is due to the lower water levels of the reservoir rather than ash-lagoon influence. 



During the 1991 review, a ground-water mound was concluded to have developed in the unoxidized 

 till similar to that in the oxidized till, extending from the east side of Ash Lagoon No. 2 to the west 

 side of the Polishing Pond. The ground-water mound was known not to be continuous because 

 some unoxidized-till piezometers within the mound area had no increase in piezometric level. The 

 new piezometers installed along Dyke B (C868C, C869C, and C871C) provided some valuable 

 infonnation. These piezometers located in the middle of the lagoon area are illustrating a 



