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<br />Background <br /> <br />Section 2 <br /> <br />2.2.2 GLEN CANYON DAM AND POWER PLANT <br /> <br />Glen Canyon Dam was authorized in April 1956 by the CRSP Act. Construction of the <br />dam and aU eight associated generating units was completed in 1966. Glen Canyon Dam <br />and power plant (GCD) is located on the Colorado River in northern Arizona, near the <br />Utah border. GCD operations are controIled by Reclamation to meet water storage and <br />delivery requirements to the Lower Colorado River Basin consistent with the laws, treaties, <br />contracts, and court decisions on Colorado River operations. known coIlectively as the Law <br />of the River. <br /> <br />The eight generating units at GCD have a combined nameplate capacity rating of 1,288 <br />MW, and produced 5,506,000 MWh of energy in fiscal year '1996. The generation available <br />from GCD is highly variable; its average annual generation during the last fifteen years was <br />5,166,000 MWh, with a low of 3,599,000 MWh (1992) and a high of 8,818,000 MWh <br />(1985). As the largest of the SLCAIIP generating resources, GCD currently represents <br />about two-thirds of the total SLCA/IP marketable capacity and seventy-five percent of the <br />marketable energy. <br /> <br />Historically, GCD has been used primarily to generate peaking power. While operating <br />this way made the power generated at Glen Canyon more valuable, it also caused <br />significant hourly and daily fluctuations in water releases, These fluctuations caused <br />concern because of their potential effects on downstream recreational, cultural, ecological <br />and biological resources. <br /> <br />The maximum possible release at GCD was designed to be 33,200 cubic feet per second <br />(cfs), With the completed generator uprate and rewind program in 1982, growing concerns <br />developed over the potential impacts from greater magnitude and frequency of releases <br />from GCD. Also at issue was the adequacy of existing environmental documentation <br />prepared by Reclamation. As a result, Reclamation established an institutional maximum <br />release constraint of 31,500 cfs until the growing public concern could be addressed. In <br />December 1982, Reclamation began Phase I of the multi-agency Glen Canyon <br />Environmental Studies (GCES) to respond to the concerns, of environmental and <br />recreational interests regarding GCD operations. Phase I of the GCES was completed in <br />1988, In June 1988, Phase IT of the GCES was initiated to address economic impacts to <br />power customers, along with other concerns. Phase IT also incorporated additional data <br />coIlection from special research flows conducted from June 1990 through July 1991. <br /> <br />2.2.3 OTHER SLCA INTEGRATED PROJECTS RESOURCES <br /> <br />Operations at several other SLCA/IP facilities are also likely to be modified to remedy <br />perceived environmental concerns. These facilities include the Flaming Gorge, AspinaIl <br />Unit, and CoIlbran Project power plants, and possibly the Rio Grande Project Elephant <br />Butte power plant. I Such operational changes could reduce the total capacity available to <br />SLCA lIP customers, <br /> <br />March 1998 <br /> <br />Western Area Power Administration <br /> <br />2-3 <br /> <br />