174 COMMISSION ON BUILDING DISTRICTS 



at every individual outlet. In order to treat the sewage under the tidal 

 conditions which exist in the harbor waters, it will be necessary to install a 

 separate system of sewers, at least in certain portions of the drainage area, 

 to take the place of the combined system which has been generally in use 

 up to the present time. 



Sewage purification plants will be installed to purify only the domestic 

 sewage and a small quantity of the storm water. To purify the domestic 

 sewage in the combined system it is necessary to construct a weir or some 

 other device to divert all the domestic sewage to the purification plant. By 

 this device the early run-off from the street, which contains a considerable 

 quantity of street sweepings, is also carried to the disposal plant. It is 

 only after a rainfall of two or three times the volume of domestic sewage 

 that it overflows directly into the harbor without purification. In the latter 

 case, however, the sewage is very much diluted and therefore carries a com- 

 paratively small quantity of organic matter into the harbor. 



Effect of height of buildings on sewage purification 



While the quantity of domestic sewage from even very tall buildings 

 does not exert a very marked influence upon the size of the sewers required 

 under the combined system, it adds very materially to the quantity of 

 sewage which has to be purified. It can be seen readily that while the area 

 still governs the quantity of storm water which reaches the sewer, but which 

 will not be purified, the quantity of domestic sewage which will be purified 

 depends entirely upon the consumption of water, which in turn generally 

 depends upon the population and the height of the buildings and also upon 

 their use. 



In order, therefore, that a purification plant may be designed of proper 

 capacity to treat the sewage from a certain area, it should be known in 

 advance what the development of that area will be, both as to the population 

 which will occupy the buildings, which is directly dependent upon their 

 height, and also upon the use to which they are put. 



The segregation of factories to certain areas is, therefore, very desir- 

 able, from the standpoint of sewage disposal, so that purification plants may 

 be designed for the particular kind and quantity of effluent which manufac- 

 turing industries contribute, because it is frequently necessary to adopt a 

 method of purification adapted to the particular kind of trade waste which 

 is produced. If it is known, therefore, what the quality of the sewage in 

 the different sections of the city is, purification plants can be designed to 

 treat it. 



It is my opinion, therefore, that the regulation of the use. height and 

 area of buildings will have a large economical influence upon the design 

 and installation of the sewers and purification plants. 



Statement by \Ym. Jay Schiefff.lin, Chairman, Citizens' Union. May 



5, 1916 



City should have been districted long ago 



The Citizens' Union recognizes in the work of your Commission the 

 first belated step on the part of the city toward an orderly development ami 

 the protection of property owners against their own short-sightedness. 

 Your tentative report indicates the care and thoroughness with which the 

 work has been conducted. The principles followed and the recommendations 

 made in this report must, in the main, meet with the approval of every person 



