indicate that total dissolved solids and boron had an average annual 

 increase of 3.75 milligrams per liter (mg/L) and 0.0285 mg/L, respec- 

 tively. Minor excursions of other water-quality objectives have occurred 

 on occasion, but no excursions remained consistent with time. Concentra- 

 tions of total dissolved solids and boron have increased with time up- 

 stream in Cookson Reservoir. 



Monitoring of ground-water levels indicated that dewatering activities of 

 the Coronach coal mine created a cone of depression that currently is 

 fluctuating with the 1 metre drawdown contour approximately 1.8 

 kilometers north of the International Boundary. From 1987 through 1989, 

 pumpage at the mine decreased by 62.4 percent. Pumpage for 1990 

 reflected an increase of 56 percent over that of 1989. 



The calculated total seepage from the ash lagoons remains well below the 

 seepage limits proposed in 1979 by the International Poplar River Water 

 Quality Board of the International Joint Commission. The advancement of 

 the groundwater front towards Cookson Reservoir in the oxidized till was 

 calculated to be 15.42 metres since the lagoons were initially filled. 

 The front in the Empress Gravel formation was calculated to have advanced 

 1,269 metres southeast of the lagoons. 



In 1989, Prairie Coal Limited moved mining operations to the South Block 

 (Willow Bunch Mine) which was developed in 1988. The Willow Bunch Mine 

 will require little dewatering and therefore, not provide supplemental 

 water to Cookson Reservoir. Although decreased from past pumpage, ground 

 water continued to be pumped from the abandoned Coronach mine during 1990 

 to supplement Cookson Reservoir water supply. 



- viii - 



