SEWAGE CONTAMTKATIOISr OF OYSTER BEDS. 



217 



Table VII. — Quatitilative analysis of water samples collected in Providence Fuver. 



Though T,he results obtained by this uiethod are by no means as accu- 

 rate as might be desired, nevertheless the}' indicate, as has alread}^ been 

 proved, a gradual decrease in the amount of pollution in the river as 

 it reaches down toward the headwaters of Narragansett Bay. 



The data obtained by the anah^sis of the foregoing water samples may 

 be summed up as follows: The Providence liiver above Conimicut 

 Point is a sewage-polluted body of water, but below this point the 

 water of the river and the headwaters of Narragansett Bay are free 

 from contamination. The presence of sewage may also be detected in 

 Warren River. That section of Mount Hope Bay in which the oyster 

 ground is situated appears to be entirely free from pollution. 



The distribution of sewage in Rhode Island waters, as indicated by 

 the presence of B. coll in water samples, may be readily traced from 

 the principal sources of contamination. As has already been stated, 

 the^eare three in number — the Providence sewage, Warren mill waste, 

 and the sewage from Fall River. Referring once more to the map on 

 page 203, it will be observed that equidistant concentric lines radiating 

 from three different centers have been drawn across the areas repre- 

 senting the Providence River, the Warren River, and Mount Hope 

 Bay. The space between these lines represents 1 mile actual distance. 

 The series of arcs which divide the Providence River into sectors are 

 drawn using the point at which the outlet of the Fields Point sewer is 

 represented as a center, and with their aid the distribution of sewage 

 in the river may be traced as follows: 



The water of the river in the sector included within the arc of the 

 first circle, at no point more than 1 mile distant from Fields Point, is 

 highly polluted. Samples taken from this portion of the river contain 

 B. coli and other fecal bacteria under all conditions of tide and weather. 



These organisms are also found in the majority of samples collected 

 2 miles below the sewer outlet. About 74 per cent of these samples 

 contained B. coli. 



