11 



3.2.5.2 Boron 



During 1992, boron concentrations in the East Poplar River at the international Boundary varied from 

 1.40 mg/L (March 16) to 2.34 mg/L (May 19) (Figure 3.6). 



2.4 



<J 2.0 



OB 



6 



^— 1.8 



a 

 o 



I 1-6 



1.4 



1.2 



- • • • • - 



• • • 



- • 



1992 



N 1993 



Figure 3.6 Boron Concentrations for 1992 Grab Samples from East Poplar River 

 at International Boundary. 



Three-month boron FWCs for the period of record are shown in Figure 3.7. The short-term objective 

 of 3.5 mg/L boron was not exceeded for the period 1975-1992. The similarity in shape between the 

 TDS and boron plots (Figures 3.4 and 3.7) is a strong indication of the influence of discharge on 

 FWC functions. 



The 5-year boron FWCs, displayed in Figure 3.8, remained well below the long-term objective of 2.5 

 mg/L boron. From mid-1988 to the end of 1990, there was a slight increase in the 5-year boron 

 FWC. The 5-year boron FWC increased slightly from 1 .90 mg/L in 1991 to approximately 1 .95 mg/L. 

 The 5-year calculations for boron were significantly influenced by discharge in exactly the same way 

 as was TDS. 



