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Ground-water quality in the vicinity of the ash lagoons can potentially be affected by leachate 



movement through the ash lagoon liner systems. The piezometers listed in the Technical Monitoring 

 Schedules are used to assess leachate movement and calculate seepage rates. Piezometric water 

 level, boron and chloride are the chosen indicator parameters for these assessments. 



The ground-water monitoring program was expanded in 1994 as a result of Ash Lagoon 3 South 

 construction. In total, 20 new pneumatic piezometers and 28 new standpipe piezometers were 

 completed within their target zones. Testing of these piezometers is scheduled to begin in 1995. 

 Nine existing piezometers were also decommissioned at the time of Ash Lagoon 3 South 

 construction including: 530, 531 . 729A, 729B, 729D, 774B. 774C and 774D. 



Piezometers 867A, 868A, and 871 A are completed immediately above the liner system, within the 

 ash stack of Ash Lagoon 1 . The 1994 monitoring results appear to confirm the trend first observed 

 in 1993 that the boron concentration decreases with depth within the ash stack. 



The chemistry of water immediately above the liner systems is therefore suspected to differ from the 

 surface water of the lagoons. Information is only available from piezometers installed within Ash 

 Lagoon 1 where ash has been deposited for many years. The effect of ash thickness on leachate 

 quality is not completely understood. New piezometers 886A, 887A, 890A, and 893A have now 

 been completed above the liner system of new Ash Lagoon 3 South. Monitoring of all piezometers 

 completed above the lagoon liner systems will be continued to confirm the trend noted above and to 

 improve the understanding of leachate quality and flow from the ash lagoons. 



The piezometric surface measurements for the oxidized till continue to show the presence of a 

 ground-water mound beneath the ash lagoons. Relative to the 1993 position, the size and extent of 

 the ground-water mound has not significantly changed. The mound extends from the east side of 

 Ash Lagoon 2, where levels have increased 6 metres, to the west side of the polishing pond, where 



