Shoshone-Bannock Tribes - Idaho Power

Responses to CommentsIdaho Power CompanyRESPONSE TO COMMENT SBT1-161Dissolved oxygen (DO) levels measured in the tailrace of Hells Canyon Dam are suboptimal forwhite sturgeon during brief summer periods. The river receives considerable aeration afterentering a series of rapids some 8 miles downstream; however, it may not achieve 100%saturation or meet Oregon’s standard for salmonid spawning as far downstream as theSalmon River. IPC is not aware of any sturgeon mortalities related to water quality (includinglow DO) that have been recorded in the reach below Hells Canyon Dam. IPC has proposedupstream measures to improve DO conditions in the tailrace of Hells Canyon Dam, which areexpected to benefit white sturgeon.RESPONSE TO COMMENT SBT1-162Comment noted.RESPONSE TO COMMENT SBT1-163IPC agrees that the effects of low DO levels on native resident salmonids are uncertain butlimited spatially and temporally. IPC studies of redband and bull trout showed that fish utilizecoldwater refuge areas when temperature and DO conditions become less than suitable in projectreservoirs.RESPONSE TO COMMENT SBT1-164IPC appreciates the Shoshone-Bannock Tribes’ support for its proposed measures.RESPONSE TO COMMENT SBT1-165This comment appears to accurately reflect the conclusion in the DLA.RESPONSE TO COMMENT SBT1-166Thank you for the comment. No response is required.RESPONSE TO COMMENT SBT1-167IPC appreciates the Shoshone-Bannock Tribes’ support of its proposed measure to install flowdeflectors on Hells Canyon Dam.RESPONSE TO COMMENT SBT1-168Thank you for the comment. No response is required.RESPONSE TO COMMENT SBT1-169IPC agrees with the Shoshone-Bannock Tribes.Page 72Hells Canyon Complex