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An extensive review of the seepage calculations has been completed by 

 Sask Power. Several different methods were used to calculate estimated 

 seepage rates and lagoon liner permeabilities. The seepage rate values 

 obtained were higher but in the same order of magnitude as the seepage 

 rates obtained by the existing method. While this confirms the existing 

 method of seepage calculation, Sask Power still recommends proceeding 

 with the adoption of an updated method following acquisition of 

 additional piezometric information. 



The Saskatchewan Department of Environment and Public Safety requires 

 that Sask Power 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 1990. The geotechnical 

 consultant indicated that the ash lagoon dykes and liners have good 

 integrity and the ash is contained effectively. The consultant noted 

 that the lagoon system is performing as designed. No special recommen- 

 dations were made other than continued routine monitoring. The freeboard 

 limits were not exceeded during 1990 for Ash Lagoon No. 2, Ash Lagoon No. 

 3, and the Polishing Pond. Freeboard limits were exceeded on Ash Lagoon 

 No. 1 during 1990; however, the intent of the freeboard limit was no 

 longer relevant due to the ash dykes within the clay dykes. The 

 freeboard limit for Ash Lagoon No. 1 was removed from the new permit 

 issued by Saskatchewan Environment and Public Safety in November 1990. 



Sask Power continued to experiment with the surcharging of ash into the 

 lagoons. A geotechnical review of the ash surcharging project was com- 

 pleted in 1990. The report indicates that slopes of 25 percent should 

 pose no problems. The report also recommended that the ash stacks be 



