- 35 - 



The 1987 calculated seepage was approximately the same as that 

 calculated for 1986 . The calculated total seepage is well below 

 the seepage limits (5.0 L/s to Cookson Reservoir and 2.0 L/s to the 

 East Poplar River) proposed in 1979 by the International Poplar 

 River Water Quality Board of the International Joint Commission. 

 The permeability of the Ash Lagoons No. 1 and 2 and Polishing 



Lagoon liners was calculated and found to be the same order of 



-9 

 magnitude (2 to 11 x 10 cm/s) as originally calculated by 



T.A. Prickett. The linear permeability for Ash Lagoon Mo. 3 North 



-9 

 was found to be 0.17 x 10 cm/s. 



The advancement of the seepage front towards the reservoir in the 



oxidized till was calculated to be 8.31 m since the lagoons were 



initially filled, which is an increase of 2.20 m since 1986. The 



< 

 seepage front in the Empress formation was calculated to have 



advanced 912 ra southeast of the lagoons, an increase of 135 m since 



1986. However, examination of Empress formation and till water 



chemistry continue to show no significant changes attributable to 



lagoon seepage. Thus, leachate flow into Cookson Reservoir and 



into the East Poplar River has not been measurable. 



The Saskatchewan Department of Environment and Public Safety 

 requires that the Saskatchewan Power Corporation maintain the 

 stability of the ash lagoon system dykes. In addition to the 

 regular visual inspections, an annual investigation by a 

 geotechnical engineer was conducted in October, 1987. Some 

 recommendations were made regarding remedial measures for erosion 

 protection and locations for further observation. SPC intends to 

 implement their recommendations during 1988. The freeboard 

 requirements were exceeded during May and June, 1988 to minimize 

 ash blowing problems from Ash Lagoon No. 1. Satisfactory freeboard 

 maintenance has been subsequently practised. 



