The Hells Canyon Case 157 



than storage utilization over the total hydraulic system's critical 

 period of two to three years.^° 



What is the economic significance of this decision in quantita- 

 tive terms? While it is not possible to obtain a refined estimate 

 of unquestionable precision, at least a crude approximation can 

 be attempted. 



First, the annual costs associated with the smaller investment in 

 the two-dam plan of operation would be approximately $472,000 

 less than under the three-dam set of facilities (see Tables 22 and 

 24). Increased power generation from the two-dam plan would 

 amount to about $374,000 annually. ^^ Furthermore, increases 

 amounting to approximately $400,000 in average annual flood con- 

 trol benefits and $50,000 in average annual navigation benefits 

 would accrue if the two-dam plan of development were undertaken. 

 In sum, an annual economic gain averaging approximately $1.3 

 million represents the advantage of the two-dam plan over the 

 Idaho Power Company's three-dam alternative. 



These estimates relate only to the difference which is assumed 

 in project design, comparing both alternatives under the assump- 

 tion that they would be operated under a constraint to maximize 

 output of the entire system. This, in turn, would require that all 

 facilities be operated under co-ordinated management. For exam- 

 ple, the increase in the total river system's prime hydroelectric 

 power from the three Idaho Power Company dams, operated under 

 hydraulic and electrical integiation, would be 702,000 kilowatts, 

 of which 585,000 kilowatts would be generated at site, 104,000 kilo- 

 watts generated at eight downstream installations, and 13,000 kilo- 

 watts would be attributable to operation under system integiation. ^^ 



^Testimony of Witness Hogg, op. cit., pp. 5716, 5729-30. 



" This assumes an increase of about 9,000 kilowatts of prime power valued 

 at $41.58 per kilowatt. The increased downstream generation made possible by 

 the added storage capacity would not require additional facilities downstream 

 for the two-dam as compared with the three-dam plan. See, for example, FPC, 

 Exhibits, op. cit.. No. 186, 28a. 



^ Ibid., No. 50, p. 77. These estimates are based on the assumptions that 

 Glacier View Reservoir is replaced in the comprehensive plan by increased stor- 

 age provided at Libby, as a partial offset; stream flows will be depleted con- 

 sistent with an assumed increase of irrigated acreages in the upper reaches of 

 the Snake amoimtlng to 366,650 acres, and a critical stream flow period of 

 thirty-two months. 



