Fluorine content of communal water supplies 
°=0.0 0.¢ ppm ©=0.5 0.Ippm o=10 1.4 ppm e=/.5ppm or more 
Ficurpe 1.—Distribution and classification of known fluorine analyses of communal water 
supplies in North and South Dakota. See figures 2 and 3 for a clarification of the 
regional pattern. 
FIGURES 2 AND 8 (facing page).—Distribution of the maximum known fluorine content in 
water supplies of North and South Dakota by counties. Figure 2 includes both com- 
munal and noncommunal supplies; figure 3, communal supplies only. Distribution is 
shown in relation to the geological formations tapped, the key to which is given in 
table 1. (Note that table 1 refers to North Dakota only.) 
TABLE I-NORTH DAKOTA, FLUORINE IN COMMUNAL WATER SUPPLIES 
; From N. Dakota Geol. Survey Bull. If 
Symbols| Number of | Number with Fluorine content of | Average Fluorine 
FORMATION His. 3.4 i gabeiar | Manors 0S-0.9 ppm|/.0-L4¢ppm| /15+ppm 
ALLUVIUM 
LAKE DEPOSITS 
unconformity 
GLACIAL DRIFT 
unconformity 
unconformity 
unconformity 
REALS Bees) 
PIERRE 
BENTON 
DAKOTA 
214 
