58 



As shown in Figure 7.7, potassium results were increasing from 1983 to 1988. A large 



spike of 135 mg/L was observed in August 1988, followed by steady results of about 60 

 mg/L to 1990. Like other test results, potassium levels dropped in early 1991 and by the 

 end of the year had increased to previous levels. 



Strontium and uranium values have shown little change from 1988 levels. Uranium levels 



in the lagoons have rarely exceeded detection limits (less than 0.1 ng/L). Strontium 

 values have been decreasing from 1988 and are now consistently below 0.5 mg/L. 



Figure 7.9 to Figure 7.1 1 illustrate calcium and magnesium results compared to changing 

 polishing pond volume and pH results. There is an apparent softening trend of the 

 lagoons from 1988. From 1989, magnesium levels have consistently been below 1 mg/L 

 compared to 5 to 25 mg/L from 1983 to 1988. Calcium levels are also lower after 1988 

 and exhibit a much wider range of fluctuations than previously seen. In February 1991 , 

 calcium concentration was 236 mg/L but in May had dropped to 2.7 mg/L. Polishing pond 

 volumes have likely influenced results for both calcium and magnesium. Solubilities of 

 magnesium may be linked to elevated pH (over 10). However, high pH levels poorly 

 explain calcium results. 



One of the most interesting trends has been the sudden decrease in boron results from 

 1990. Historically, boron results were increasing from 1983 to 1985. This was expected 

 as boron concentration reached solubility limits. From 1985 to 1990, boron 

 concentrations moved within an established range of between 70 and 90 mg/L. 



