GROUND WATER QUANTITY 



Coal Seam Dewatering Saskatchewan 



Data on ground-water levels were exchanged for five piezometers in Sasi<atchewan 

 near the International Boundary for the purpose of monitoring drawdown due to 

 coal seam dewatering at the Poplar River Mine, A decrease in 198z of 0.56 meters 

 was observed in piezometer 52, closest to the mine. Levels at the four other 

 piezometers increased from 0.13 to O.AO meters. 



A map of the cone of depression, prepared for the Saskatchewan Department of 

 Environment Is shown in Figure k. Near the mine site the drawdown cone exceeds 

 20 meters. The cone of depression extends south to about one-half mile of the 

 International Boundary. The Committee will maintain close scrutiny of any 

 expansion of the cone of depression, and in I983, will endeavor to undertake 

 activities to relate the initial ground-water model to the monitoring results. 

 That is, the Committee recommends that the United States initiate water-level 

 monitoring near the International Boundary south of the point of maximum 

 expansion of the cone of depression. Additional test wells may be required. 



Montana 



Ten wells which penetrate the following formations were monitored and sampled 

 in the United States portion of the East Poplar River basin near the International 

 Boundary. The wells penetrate the following formations: Alluvium (0-15 meters 

 in thickness); Flaxville (0-26 meters in thickness); Fort Union, including the 

 Hart coal seam, (2kk plus meters in thickness); Fox Hills (26-36 meters in 

 thickness); Hell Creek (67-85 meters in thickness). Water level observations 

 were made quarterly. Four of the wells were equipped with continuous water- evel 

 recorders. 



Small increases and decreases in water levels have occurred in all wells during 

 the two and one-half year observation period, but no trends are noticeable. 

 During April and May I982, small increases were noted in shallow wells 5, 6, 

 and 10, probably due to above average precipitation. Dewatering of the Hart 

 coal seam north of the International Boundary has, to date, no apparent effect 

 on any of the U.S. observation wells. 



17. 



