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 groimd- water monitoring program was expanded in 1994 as a result of Ash Lagoon No. 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 No. 1 . The 2003 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 fi-om piezometers installed 

 within Ash Lagoon No. 1 where ash has been deposited for many years. The 2003 monitoring results of 

 Ash Lagoon No. 3 South piezometers completed above the liner system (piezometers C886A, C887A, 

 C890A and C893A) 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 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. 



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