26 



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

 where piezometric levels have changed the most. This is an expected result as changing 

 piezometric levels suggest groundwater movement. Increasing boron concentrations on the east 

 and south side of Ash Lagoon 2, together with decreasing chloride concentrations suggests 

 leachate influence. On the west side of the polishing pond the boron concentrations have not 

 significantly changed. 



Little change in boron or chloride concentrations has been observed for most of the oxidized till 

 piezometers located by the reservoir. The most significant change in samples from any of these 

 piezometers has been C719 where chloride concentrations have decreased 92 mg/1 overall since 

 1983 to 19 mg/1. The change in quality is suspected to be the result of reservoir influence rather 

 than ash lagoon influence. 



A groundwater mound has developed in the unoxidized till, similar to that in the oxidized till, 

 extending from the east side of Ash Lagoon 2 to the west side of the Polishing Pond. The 

 groundwater mound is known to be discontinuous as piezometers 764D and 87 IC are located 

 within the mound area and are reacting to reservoir levels. A review of boron and chloride 

 concentrations does not show any significant trends. 



The piezometric surface of the Empress gravels indicate a regional flow from northwest to 

 southeast below Morrison Dam. Monitoring since 1983 generally shows that the piezometric 

 surface in the lagoon area reacts to the reservoir level. Results for Empress gravel water quality 

 do not indicate any leachate influence with the majority of piezometers showing little change in 

 boron or chloride concentrations from background values. 



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. 



A review of the boron concentrations for C766 shows an increasing trend up to October 1988 

 when levels peaked at 12.6 mg/1. Boron concentration decreased to 6.99 mg/1 in April 1990, then 



