856 



PARKS 



disposal by dilution is contemplated the local or state health authorities 

 should be consulted in regard to the location of the outlets. 



Many service areas in parks and reservations are so located that it is 

 impracticable to dispose of the raw sewage by dilution, and some other 

 form of treatment must be employed. In such instances the most feasible 

 method of treating sewage involves the use of some form of a septic tank. 

 In a septic tank the solid portions of the sewage are liquefied, certain of 

 the unstable substances are reduced to stable compounds, and many of 

 the disease-producing germs are killed. These changes are produced by the 

 action of bacteria which live in the depths of the tank. 



The ordinary septic tank consists of a closed concrete basin, through 

 which the sewage flows at a rate which will permit a certain amount of 



TOP VIEW 



9'n 



STEEI. MIR PLATE BOLTED TO CONCRETE, 

 WITH TOP SET PEPFECTLY LEVEL X 



"OVERFLOW 



6" OUTLET 



WHERE DlMCAISIOrt C IS OPEAT. 



LOOSE OC WET SOILS, OR WHEPE 

 EXTRA PPECAUT4C/N IS DESIBED, 

 ErtDA SIDES OF MAI/S 

 WITH FE/SCC WIPET. 



PLATE No. 333 



SECTION THROUGH SEPTIC TANK SHOWING THE POSITION OF THE BAFFLE BOARDS 

 WHICH ARE USED INSTEAD OF AN INVERTED TEE 



(Pennsylvania State Department of Health.) 



Septic tank for 25 persons: length, 9 feet; width, 4 feet 6 inches; depth below flow line, 4 feet 6 inches. 

 Siphon chamber of such size as to discharge the effluent from the tank from one to three times each 24 hours, 

 according to local conditions. 



