Water Supply Problems in Alaska— Alter 



227 



been completely submerged in sewage and the domestic water 

 supply has been contaminated with sewage. Utilidors must be 

 constructed in such a manner that they will not be flooded with 

 suprapermafrost water. Flooding of water lines with either 

 ground water or sewage creates a very undesirable and unsafe 

 condition. Figure 3 illustrates the manner in which utilidors 

 may become flooded with ground water and it also shows how 

 waste heat may maintain a thawed area around a utilidor. 



REMOVABLE TOP ON CAST-I N- PLACE UTILIDOR 



Fig. 1. 



Recirculating water mains, as the name implies, are distri- 

 bution lines in which the water is circulated. The water may 

 be circulated continuously or at intervals necessary to keep the 

 system from freezing. The mains are constructed so that they 

 constitute a closed circuit and a heating plant is placed near the 

 point where the water enters the system. Sufficient heat is added 

 to the water at the source of supply to maintain temperatures 

 above freezing throughout the distribution system. 



Recirculation may also be maintained in the service connec- 

 tion either by use of a dual main distribution system or by use 



