INVESTIGATION OF DRINKING WATER SUPPLIES 165 



in the hands of an untrained observer who is often incompetent 

 to undertake the work. This same unskilled individual is 

 entrusted with the duty of securing samples of water that 

 must be properly collected if satisfactory results are to be 

 obtained. These samples are then shipped to the laboratory 

 and subjected to a most careful examination by a skilled 

 technician when there is little assurance of the accuracy of 

 their collection. This method makes it necessary for the skilled 

 worker to accept facts from an untrained person on the funda- 

 mental features of an investigation on which the safety of 

 a water supply is to be judged. The fallacy and danger of 

 such practice is very evident when these points are considered. 

 The importance of thorough investigation work on water 

 supplies is illustrated in the following tables. These tables 

 include six years of investigation work on existing water sup- 

 plies by the Minnesota State Board of Health. 



TABLE I. WATER SUPPLY INVESTIGATIONS, 1912-1918 



The investigations recorded in Table I represent both sur- 

 face and underground water supplies from a variety of 

 sources including wells (dug, bored, drilled, driven), springs, 

 lakes, rivers, creeks, etc. This table shows that 1,119 existing 

 water supplies were investigated during the period indicated. 

 Three hundred eighty-nine, or 34 per cent, were shown to 

 be safe and 730, or 66 per cent, were found to be unsafe 

 sources in their existing condition. 



TABLE II. UNSATISFACTORY WATER SUPPLIES, 1912-1918 



Shown Unsatisfactory by 



