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Groundwater 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 to assess leachate movement. 



The groundwater 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 began in 1995. The limited data so far do not 

 show any unusual or unexpected values. 



Piezometers C867A, C868A and C871 A are completed immediately above the liner system, within the 

 ash stack of Ash Lagoon #1. The 2000 monitoring results continue to suggest confirmation of the trend 

 first observed in 1993 that the boron concentration decreases with depth within the ash stack. The effect 

 of ash thickness on leachate quality is, however, not completely understood. 



The chemistry of water immediately above the liner systems is therefore expected to differ fi-om the 

 surface water of the lagoons. Meaningfiil information is only available fi"om piezometers installed 

 within Ash Lagoon #1 where ash has been deposited for many years. New piezometers C886A, C887A, 

 C890A and C893A have been completed above the liner system of new Ash Lagoon #3 South and are 

 now being monitored. Monitoring of these piezometers in 2000 supports the theory that boron levels 

 decrease with depth within the ash stacks. Future monitoring of all piezometers completed above the 

 lagoon liner systems will continue with the purpose of confirming the boron trend noted above and to 

 improve the understanding of leachate quality and flow fi-om the ash lagoons. 



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

 groundwater mound beneath the ash lagoons. The mound extends fi-om the west side of the Polishing 

 Pond to the east side of Ash Lagoon No. 2. Isolated groundwater mounds have developed within the 

 area of the oxidized groundwater mound. Piezometers located in the oxidized till suggest limited 

 leachate activity. No seepage activity is evident in the unoxidized till. 



