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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 to assess leachate movement. 



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 began in 1995. The limited data so 

 far do not show any unusual or unexpected values. 



Piezometers C867A, C868A and C871A are completed immediately above the liner system, within the 

 ash stack of Ash Lagoon #1. The 2001 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. Meaningful information is only available from piezometers installed 

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

 C890A and C893 A have been completed above the liner system of new Ash Lagoon #3 South and are 

 now being monitored. Monitoring of these piezometers in 2001 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 piirpose 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 ground- 

 water mound beneath the ash lagoons. The mound extends from the west side of the Polishing Pond to 

 the east side of Ash Lagoon No. 2. Isolated ground-water mounds have developed within the area of the 

 oxidized ground-water mound. Piezometers located in the oxidized till suggest limited leachate activity. 

 No seepage activity is evident in the unoxidized till. 



