712 ECONOMICAL ASPECTS 



ANNUAL COST OF OPERATION 



A depreciation of 5 per cent ($21,800) has also been charged to 

 this development. No taxes or interest is charged, the under- 

 taking being done by the Government. Assuming 7 per cent 

 for interest and taxes the total operating expenses would amount 

 to $62,000. A total of about 15,000,000 Kw. hr. were delivered 

 during one year, thus corresponding to a cost of $0.0041 per 

 Kw. hr. 



ACTUAL COST OF 20,000-Kv.A. HYDRO-ELECTRIC POWER DEVEL- 

 OPMENT OF THE CITY OF TACOMA, WASHINGTON 



This development comprises a concrete dam approximately 

 45 feet high and a spillway of 260 feet. Intake, racks, regulating 

 gates and a settling channel, the latter being 780 feet long, 40 

 feet wide and 20 feet deep. From the settling basin the water is 

 carried through an 8 X 8-foot tunnel, 10,000 feet long, to a reg- 

 ulating reservoir approximately 500X500 feet, having a capacity 

 of about 3,000,000 cubic feet available for use during peak loads. 

 Each main turbine has a separate riveted-steel penstock about 

 780 feet long and ranging in size from 78 inches at the top to 48 

 inches at the gate valves in front of the turbines. The two 

 exciter wheels are supplied from one 24-inch pipe which divides 

 in the generator room. 



The power-house consists of three buildings of the common 

 wall type of construction of concrete and brick, with galvanized- 

 iron roof supported by steel roof trusses. There are four 8000- 

 H.P. horizontal main turbines operating under a 415-foot effective 



