52 

 7.5 Lagoon Seepage Estimates 



In 1990, SaskPower submitted tlie report entitled "Hydrogeological Evaluation - Ash 

 Storage Lagoon" prepared by Clifton Associates Ltd., of Regina. A purpose of the report 

 was to review the existing seepage calculations and recommend changes, if required, to 

 the existing method or propose a new method that would increase the accuracy of the 

 calculation. 



The existing method for estimating seepage was confirmed to be acceptable but adopting 

 an updated method was recommended. Before an updated method can be adopted, it 

 will be necessary to obtain additional piezometer level information from within the lagoon 

 area. Installations of new piezometers are planned for the summer of 1992. The existing 

 calculations will be used until newer methods of completing the seepage calculations are 

 approved. In the last quarter of 1991 , comments of the report were received supporting 

 the findings and recommendations of the report. 



Results of these 1991 seepage calculations are summarized in Table 7.1 along with the 

 results of previous calculations from 1984. The total calculated seepage was determined 

 to be 1 .267 L/s and is a large increase over the 1990 calculated value of 0.991 Us. This 

 increase can mostly be attributed to the growth in calculated seepage rates for Ash 

 Lagoon No. 3 North from 0.144 L/s in 1990 to 0.332 L/s in 1991. This was expected 

 because of the elevated operating levels for Ash Lagoon No. 3 during 1991. This was 

 the first year that ash was directed from both units to this lagoon for the entire summer. 



