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<br />CHAPTER II - DESCRIPTION OF AL TERNA TlVES <br /> <br />This chaptcr presents the alternatives considered in detail. the alternatives eliminated from <br />detailed study. and a summary comparison of the alternatives and their impacts. The No- <br />Action Alternative is the continued cold.\\:atcr release from the penstock elevation. The <br />Action Alternative \,,'ould modify the intakes of the dam so warmwater could be released <br />from the dam. <br /> <br />NO-ACTION ALTERNATIVE <br /> <br />The No-Action Alternative would continue to release cold water (usually between 8'T to <br />lOOe) through the existing power penstock intake elevation. <br /> <br />ACTION ALTERNATIVE (Temperature Control Modifications) <br /> <br />The Action Alternative would modify the intakes of the dam so warm ''''ater could be <br />released from the dam. The proposed modification would make extensive use of the existing <br />(hollow) trashrack structure to convey water from the surface. <br /> <br />As was mentioned earlier in the Scoping section of this repon. there are complicated <br />ecological interactions in the Grand Canyon which add a small. but very serious. degree of <br />risk to the outcome of <br />temperature comrols. The <br />potential interactions of native <br />and non-native fish (and the risk <br />10 humpback chub) and their <br />ecosystem remain uncenain. <br />The goal of ",'arming the water <br />in the main channel of the river <br />is to provide suitable spa\\ning <br />and gro\\1h temperatures for the <br />native fish (i.e.. humpback chub. <br />tlannelmouth sucker. bluehead <br />sucker. and speckled dace). <br />However. warm water may also <br />benetit non-native competitors. <br />Temperature controls are likely <br />to be bcneticial. but an adaptive <br />management program would be <br />used to monitor and refine the <br />operation of the facility to <br />optimize its bene tits. <br /> <br />Maximum Normal <br />Water Surface <br />Elevation <br />3700 feel <br /> <br />Proposed LocatJon to( <br />New. Warm Water <br />Inlak.es for Penstocks <br /> <br />Existing <br />Trashrack. <br />SlrtlcttJre <br /> <br />ExislJng Cold <br />Water <br />Intak.esfor <br />Penstocks <br /> <br /> <br />Figure" ~ Photo of upstream side of Glen Canyon Dam <br />showing intakes for po\".-er penstocks soon after <br />construction was completed (before the reservoir was <br />filled). <br /> <br />It was this uncenainty that led <br />Reclamation to seek a relatively <br />