Final Environmental Impact Statement Volume II Appendix K, Part 2

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EPA -9 til o. COMMENTS OF U.S. ENVIRONMENTAL PROTECTION AGENCY In an effort to fully coordinate and share our position with the state on the standard compliance issue, EPA met with NDEQ on July 6, 1994, and the Governor's staff on July 7, 1994. In response to the meeting with NDEQ, EPA was asked to provide any questions that we had regarding the issuance of the section 401 certifications for these projects in writing. We responded to this request on July 13, 1994 (Ronald R. Ritter, Acting Director, EPA Region VII Water Division, to Randy Wood, NDEQ), asking a number of questions in an attempt to clarify the basis for NDEQ's issuance of its section 401 certifications. We are aware that, in a letter to FERC dated July 12, 1994, the Governor cited the above attempts to certify the projects and concluded that "(t]he State of Nebraska has no plans to change or reconsider these 401 certifications." In order to ensure adequate compliance with the state water quality standard for temperature, FERC should require that the projects meet certain minimum summer instream flow conditions as a condition of the final licenses. The projects should be required to meet the temperature standard because they, in majority, control the timing and amount of downstream instream flow releases. Since the closure of Lake McConaughy, the Platte River channel has been degraded through lack of sediment inflow and resultant vegetative encroachment (see DOI letter to Lois Cashell; cover letter, Attachments 2 and 3, November 15, 1991). According to DOI, "Projects 1417 and 1835 have contributed to the loss of channel width and vegetative encroachment through sediment trapping, reduction of sediment transport flows, reduction of peak scouring flows, diversion of flows, and consumptive use of water. Losses of active channel width and migratory bird use have been greatest in those reaches of the North Platte and Platte River where project operations bypass or store most of the flow during the nonirrigation season. The projects control flows in the central Platte River throughout the year, including flows within and below the designated critical habitat of the whooping crane. Since large areas of Gosper, Kearney, and Phelps Counties are overlain by Project 1417, we believe that the project has contributed to wetland losses in this area. For example, the delivery of surface irrigation water to the area by Project 1417, and the higher water table resulting from project seepage, has encouraged irrigation development in the region (including the associated landscape and drainage modifications needed to accommodate irrigation) and, therefore, has been an important factor in these losses RESPONSES TO U.S. ENVIRONMENTAL PROTECTION AGENCY EPA -9 Our analysis (Appendix E) shows that the maximum daily water temperature in the Big Bend Reach is influenced by both maximum daily air temperature and mean flow. Further, the variation in air temperature accounts for the majority (64 percent) of variation in water temperature. The probability of maximum water temperature exceeding the 32 °C standard decreases with higher specified minimum flows, but the probability levels off at about 14 percent at flows of 1,500 cfs. We conclude that it is unreasonable to require these projects to operate in a manner that guarantees achievement at Grand Island of the 32 °C standard. Our analysis shows that flow, by itself, may never be sufficient to guarantee achievement. Requiring a 900 -cfs minimum flow, as suggested by EPA, results in our simulation in a probability of exceedance of the 32 °C standard of 17 percent. EPA apparently recommends a 900 cfs minimum (when Lake McConaughy volume exceeds 900 KAF) on the basis that little improvement in standard exceedance occurs beyond this flow rate. Our analysis shows that little improvement occurs beyond a 1,100 cfs minimum.