30 



The greatest changes in chloride and boron concentrations within the oxidized till have occurred where 

 piezometric levels have changed the most. Although increasing water levels do not automatically 

 suggest that the water affecting the piezometers is leachate, changing piezometric levels do suggest 

 groundwater movement. Oxidized till piezometers C868B and C869B located in the middle of the 

 lagoons, between Ash Lagoon No. 1 and No.2, have shown increased piezometric levels but no chemical 

 information to suggest leachate influence. On the west side of the Polishing Pond, the boron levels have 

 changed only slightly in the oxidized till piezometers C728A and C728D, where the chloride levels have 

 changed more significantly. The chloride level for C728A has decreased fi"om 403 mg/L in 1 983 to 244 

 mg/L in 2000. The chloride level for C728D has increased from 185 mg/1 in 1983 to 372 mg/L in 2000. 

 Although these piezometers are close in proximity and installed at the same level, they are being 

 influenced by different water. Chloride results for C728A suggest initial seepage and it is to be expected 

 that over time the same observation will be seen in C728D. 



The piezometric surface of the Empress Gravel indicates a regional flow fi-om northwest to southeast 

 below Morrison Dam. As a general observation, Empress piezometers respond to changing reservoir 

 levels. Results for the Empress layer do not indicate seepage activity with the majority of the analyses 

 showing little real change in boron or chloride results. 



Sand lens piezometers C712B, C766 and C767 are located between the polishing pond and the cooling 

 water canal. C767 is located on the top of dyke G and C766 and C712B are located at the toe of dyke G. 

 These piezometers have historically been of interest as the sand lens provides a preferential pathway for 

 leachate migration of boron concentrations. C766 shows an increasing trend up to October 1988 with a 

 peak of 43.0 mg/L in 1995 April. Since 1995 the boron levels have declined modestly and have 

 remained between 25 and 38 mg/L. 



Up to April 1988 the boron concentration for C767 was increasing and peaked at 49.4 mg/L. Since this 

 peak the boron concentration steadily decreased to the end of 1991 where it leveled off near 5 mg/L and 

 has since remained with one exception, a concentration of 1 1 .7 mg/L in October 2000. 



Piezometer C712B has been monitored for several years. Historically, boron levels were below 1 mg/L. 

 From 1992 to 2000, boron levels have remained relatively steady around between 12 and 20 mg/L. 



