26 



At location 9a, at the west end of the polishing lagoon, piezometers 728B 

 and 728C show a general increase in uranium level over the period 1983 to 

 July 1985, but the concentrations drop off again slightly in October 1985. 



The variability in the concentration for most chemical species observed 

 both spatially and temporally in the tills can probably be attributed to 

 localized geochemical conditions adjacent to piezometer intakes and to 

 variability in recharge rates through the tills. In the case of sulphate, 

 this is supported by the observation of gypsum lenses in the tills in 

 drill cuttings recovered at the time of piezometer installation. The 

 ground water chemistry in the tills is therefore influenced by the amount 

 of net ground water recharge over the area, as well as the mineralogic 

 content of the tills at the sampling point and along the flow path of the 

 infiltrating water. 



Water Quality in the Empress Gravels 



No significant water quality trends are evident in the Empress Gravels. 

 Figure 7 shows that TDS levels remain generally unchanged over the period 

 of record (1980 to 1985). 



Piezometer C533 appears to have undergone a very slight increase in 

 chloride concentration over the period of record, but no other chemical 

 species have increased consistently. For instance, uranium has remained 

 at a relatively stable concentration since early 1981 in all 

 Empress-completed piezometers (C533, C534, C726E, and C728E). Boron 

 levels decreased in C533 since 1980, and showed no significant trends in 

 C534, C726E, and C728E. 



