Automatic Recording and Control Devices in Tacoma's Water System

Abstract

ELIMINATE, wherever possible, the unreliable features in the operation of the water supply and distribution systems of Tacoma, Wash., which are due to the manual operation of certain control units, numerous automatic recording and pressure control devices have been installed during the last few years. The use of these devices has improved pressure conditions over large areas, particularly during times of peak demand, has lessened the demands on operators, and has provided the department with necessary basic information for making additional future improvements. The principal source of Tacoma's water supply is the Green River, from which water is piped to the city through a gravity system. The intake for this system is located approximately 28 mi. east of the city in the foothills of the Cascade Mountains, the crest of the diversion dam being at an elevation of 908 ft. A single pipe line, 26.6 mi. long and of varying diameter, conveys 52 m.g.d. to McMillin Reservoir, the main storage reservoir on the system.* Capacity of the two compartments of McMillin Reservoir is 110 mil.gal., and its water level is held at 588 ft. From the reservoir, two large pipe lines, with a combined capacity of 92 m.g.d., supply the water to the distribution system in the city. The older of these lines is 15.3 mi. long and was designed for gravity flow opera-