SEWAGE CONTAMINATION OF OYSTER BEDS. 205 
THE SOURCES OF SEWAGE POLLUTION OF NARRAGANSETT BAY. 
The sewage of the city of Providence and immediate neighborhood 
is collected at the sewage pumping station at Fields Point, about 12 
miles below the city, and is discharged into the river through a single 
large main. The outlet of this drain is indicated on the map on page 
203. Though it is covered by 25 feet of water at low tide, it may be 
readily located on a calm day by the greasy, turbid stream of sewage 
which rises rapidly to the surface of the water at that point. 
In 1900 an average amount of nearly 14,000,000 gallons of sewage 
was daily pumped into the river through the Fields Point sewer, and 
at that time was thrown into the river in a > or ‘Suntreated” 
6s 
crude ” 
state; that is, it was simply passed through a screen to remove the 
solid matters before being sent on to the outfall pipe. The screen con- 
sisted of a rack or frame of parallel iron rods placed about an inch 
apart, and was set at an angle of about 20 degrees from the perpen- 
dicular. The stream of sewage was allowed to flow through this 
apparatus, and whatever constituents were too bulky to pass through 
the grating were scraped off with a rake and otherwise disposed of; 
but, as might be expected, considerable amounts of solid matter slipped 
through, and the beaches within half a mile of the outlet were strewn 
with this refuse. 
Before these investigations were completed, however, the city put 
in operation a sewage disposal plant at the Fields Point Station. 
After screening, as already described, the sewage is subjected to the 
action of sulphate of iron and chloride of lime, which process causes 
about 50 per cent of the total solids then in suspension to precipitate 
out and sink to the bottoms of large reservoirs in which the sewage 
is allowed to remain for twenty-four hours. The clearer fluid is then 
drawn off and turned into the river, while the ‘‘ sludge” which remains 
on the bottom of the basin is strewn over the land. Before this 
method was employed the gray scum from this sewer could often be 
traced on the surface of the water several miles below Fields Point, 
where it had been carried by tidal currents. The station has one other 
large outlet, the ‘‘storm” sewer, which opens into the river from the 
northern shore of the point. This sewer isa culvert built in the form 
of an arch, which is entirely out of water at low tide. It is used only 
in case of accident to the large main or during heavy rain storms, 
when 20,000,000 and sometimes 25,000,000 gallons are discharged in 
twenty-four hours. . 
Two other small overflow sewers help to drain the east side of the 
city, pipes discharging into the Seekonk River between Red Bridge 
and Washington Bridge. The sewage from these drains, together with 
that of the city of Pawtucket, situated on this same stream 3 miles 
above Providence, and the waste from the various mills along the banks 
of the river pass down the Seekonk into the head of the Providence 
