25 



installed on the west side of Ash Lagoon No. 1 closely matched levels in other piezometers on the 



west side of the ash lagoons and these levels did not affect calculations. However, the new 

 piezometers on the east side of Ash Lagoon No. 1 did indicate large increases in piezometric levels 

 from background values and when these levels were added to the calculation, the calculated 

 seepage rates increased. The piezometers on the east side of Ash Lagoon No. 1 provided data in an 

 area where there was no previous information. Calculated liner permeabilities for the ash lagoons 

 have remained about 1 0"^ cm/sec. 



The calculated total seepage from the ash lagoons is well below the seepage limits proposed in 1 979 

 by the International Poplar River Water Quality Board of the International Joint Commission. 



3.3.3.2 Montana 



Samples for water-quality analysis were collected from Montana monitoring wells 5-11, 15, 16, 19, 

 23, and 24 in 1992. Graphs of total dissolved solids for selected wells are shown in Figure 3.12. 



200 



Jan-79 Jan-81 Jan-83 Jan-85 Jan-87 Jan-89 Jan-91 Jan-93 Jan-95 



Date 



Figure 3.12 Total Dissolved Solids in Samples from Montana Monitoring Wells. 



