Electrical Power for Valdez and the Copper River Basin-1981

3. have adequate flows for flushing of the gravels." Does the Corps haveany additional mitigating measures, such as mecha~ical flushing, plannedfor cleaning spaw~ing gravels if necessary? This topic needs to bediscussed in greater detail in the FEIS.Section E, page EIS-154. This section discusses, among other things, the concept of a two tailracesystem to regulate the quantity of water being released into AllisonCreek. It appears that water from the powerhouse .... ill be available tosupplement the flow in Allison Creek as needed. It is imperative thatthis water does not differ substantially from the normal flow in AllisonCreek with respect to temperature, dissolved oxygen, etc. This projectshould be designed to ensure that adequate natural stream flows areavailable if needed (Le. if the powerhouse is shut down or if thequality of water from the powerhouse is inadequate with respect totemperature, etc.).5. This section also contains a brief discussion of the potential forcumulative impacts resulting from construction of the ALPETCO facilityand dock, the city dock expansion, the Solomon Gulch hydroelectricproject and some proposed development on Mineral Creek. This sectionshould be expanded to include a description of each of these projectsand some discussion of the potential impacts.3. Allison Creek is relatively free of small grain materials and fines. Theperiodic spilling of Allison Lake and the expected SUrm1er flo .. s '.;auldprobably be sufficient; therefore, no sedimentation of the stream isanticipated. However, if additional studies show that sedimentation ofspawning gravels does occur, the problem would be rectified by methodsagreeded upon during the AE&D phase prior to construction.4. If a moderate to large percentage of the flow is discharged from thepowerhouse it is possible that a temperature change could occur. Most ofthe spawning occurs intertidally and the effects of the warmer dischargeon incubation is unknown. The planned installation of an intergravel,intertidal thermograph and expanding knowledge of the winter flow regimewill aid in refining mitigative measures. Adequate flows would bemaintained by scheduling turbine maintenance during times when sufficientnatural stream flow for egg incubation is available.5. The Alaska District agrees the cumulative impacts in the Valdez area arean important aspect to further development. Environmental ImpactStatements or Environmental Assessments have been published for theseprojects and are reasonably available. In accordance with NEPAguidelines, this information has been incorporated by reference.CLEARANCE:;!,/~TIJREF/HP: Ken ROberts~\ rt, U---z"¥----=tUm DATE:Ii-,: .