CONSTRUCTION OF CRTS AMBRIES 39 



is much traffic they are best covered by heavy, perforated iron 

 plates. These ditches should have a slope of at least one-eighth 

 inch per foot, their depth must necessarily depend somewhat on 

 their length and the depth of the main sewer pipe into which 

 they discharge. It is not advisable to have these ditches more 

 than about 40 feet apart, for rapid drainage of the floor. 



The main sewer pipe, catching the drain discharges, should 

 be of large capacity, not less than six inches in diameter for a 

 small creamery and eight to twelve inches for a creamery manu- 

 facturing over 500,000 pounds of butter. Where the creamery 

 waste is disposed of through the municipal sewer, there should 

 be installed between the drain and the sewer pipe, outside of the 

 factory, a catch basin, or sediment tank. This is a tight cistern 

 through which all the creamery sewerage must pass and in which 

 the curdy material is given an opportunity to separate out and 

 rise to the surface, forming a dense layer. This curdy material, 

 if allowed to pass off into the municipal sewer, is prone to coat 

 and ultimately clog the town sewer pipe. This is especially 

 prone to happen, where the town sewer line has relatively little 

 fall. This catch basin must be cleaned out, removing the ac- 

 cumulated curdy scum, at reasonable intervals. 



In order for this cistern to operate efficiently, it should be 

 large enough to hold the waste of at least one day's run. Its 

 intake from the creamery should terminate above the surface of 

 the accumulating scum in the cistern, and its outlet should extend 

 to near the bottom of the cistern. This arrangement will prevent 

 the outlet from becoming plugged up with scum. The chief solid 

 matter in creamery sewerage floats on the surface. There is very 

 little sediment deposited at the bottom. 



Light. It is advisable to install a reasonable number of 

 properly screened windows, so as to enable the operation of the 

 plant without artificial light, especially in winter, late fall and 

 early spring. 



The sanitary value of natural light in the creamery has been, 

 in the past, greatly exaggerated and over-estimated, especially by 

 the average sanitary inspector. The tendency has been toward 

 a hysterical eulogy of the purifying action of the direct rays of 

 the sun. The fact is that even in creameries with a great abun- 



