13 - 



The Bilateral Monitoring Committee has adopted the approach that for the 

 purpose of determining compliance with the proposed IJC long-term 

 objectives, the boron and TDS data are best graphically plotted as a 

 5-year flow-weighted moving average which is advanced one month at a 

 time. Each point represents the flow weighted concentration for a 

 5-year period, with two and one-half years on either side of the plotted 

 point. It must be emphasized that the data base is comprised of all data 

 collected over the twelve months of all years. 



Total Dissolved Solids 



The proposed short-term objective for TDS is 1,500 mg/L. A plot of the 

 3-month moving flow-weighted concentration is shown in Figure 4a. No 

 exceedences have been observed in either the grab sample-generated data or 

 in the regression-calculated data over the period of record. 



The observed relationship between TDS and specific conductance for the 

 entire period of record is: 



TDS = (0.642 X specific conductance + 9.32) (R-squared = 0.87) 



The long-term, 5-year moving flow-weighted concentrations for TDS is shown 

 in Figure 4b. The long-term flow-weighted values remained well below the 

 proposed objective of 1,000 mg/L. Because flow weighting is calculated 

 across five years, a radical change in flow or the instantaneous 

 concentrations can significantly alter the plot of the moving 5-year 

 concentrations (see Figure 4b). The decrease depicted in the graph. 



