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Trinity River Restoration Program, Weaverville, CA

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Bureau of Reclamation, Interior.


Notice and correction regarding implementation of program.


On December 19, 2000, the Secretary of the Interior (Secretary) signed the Record of Decision (ROD) implementing the Trinity River Restoration Program (Program), which adopted the Preferred Alternative analyzed in the Trinity River Mainstem Fishery Restoration Final Environmental Impact Statement (FEIS). The Department of the Interior (Department) has identified a discrepancy in the description of the hydrologic forecast used in the annual flow regime component of the Program. The impacts analysis in the FEIS was based upon modeling the historic inflows into the Trinity River watershed above the Trinity Dam and categorizing this data into five water-year classes. These classes and their probability of occurrence were displayed in the FEIS and are repeated below:

Table A.—Values from Final EIR/EIS Table 1 (page C-3)

[WY 1912-1995]

Water-year classTrinity River allocation (T AF)Annual runoff into Trinity Lake (TAF)Probability of occurrence
Critically Dry369<6500.12
Extremely Wet815,000>20000.12

This discrepancy occurred because the FEIS narrative in Appendix C incorrectly references use of a 90% exceedence forecast in determining classes for the upcoming water year. Use of the 50% exceedence forecast more accurately reflects the occurrence of water year types identified in the chart above and more closely approximates the impact analysis in the FEIS.

The corrective action taken by the Department will ensure that any potential impacts from implementation of the Program are consistent with the FEIS. This correction does not require any new action or the modification of an existing action, so no further National Environmental Policy Act (NEPA) analysis is necessary. Moreover, correcting this error in the FEIS Appendix C narrative will have no new impacts on the goals of the Program, or on water and power users beyond what has already been disclosed and analyzed in the FEIS, and there is no change in the ROD itself. By making this correction now, Reclamation's actions with regards to determining the water year type for the 2006 water year will be consistent with the impacts analysis approved in Westlands Water District v. Department of the Interior 366 F.3d 853 (9th Cir, 2004). In summation, the NEPA and Trinity River Flow Evaluation Study (TRFES) analysis are unchanged and Reclamation is simply ensuring that implementation of the Program reflects the analyses used in the FEIS and ROD.


The Secretary is not proposing to take any new action as a result of this Federal Register notice. Accordingly, the Department is not establishing a specific date by which comments must be submitted.


You may submit written comments to Douglas Schleusner, Executive Director, Trinity River Restoration Program, P.O. Box 1300, Start Printed Page 265611313 South Main Street, Weaverville, California 96093.

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Douglas Schleusner at (530) 623-1800.

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On December 19, 2000, the Secretary, with concurrence of the Hoopa Valley Tribe, signed the ROD for the Program. The decision outlined in the ROD called for the implementation of the Preferred Alternative, which incorporated the recommendations developed in the TRFES and evaluated in the FEIS under the Flow Evaluation Alternative, coupled with additional watershed protection efforts identified in the Mechanical Restoration Alternative contained in the FEIS.

A component of the Flow Evaluation Alternative is a flow regime that is intended to achieve various anadromous fishery habitat objectives associated with meeting the goals of the Program. The recommended flow regime and the water year class, which determine the volume of water available in a given year, were developed from historic annual hydrologic records of the Trinity River watershed. Under the ROD, the water year class for any given year is determined based on the total water runoff (unimpeded flow) forecasted to occur in the Trinity River watershed above Trinity dam, as of April 1 of each year. The water year classes and expected probability of occurrence are stated in the chart above.

Appendix C of the FEIS sets out the process for the water year class forecast. On page C-4 the FEIS states: “Annual basin runoff is calculated by summing the amount of runoff that has occurred form October 1 until April 1 and a volume of water that Reclamation forecasters predict (90 percent probability of exceedence) will run off during the months remaining in the water year (i.e. April through September) using the April 1 runoff forecast projection from the California Cooperative Snow surveys, California Department of Water Resources, Bulletin 120. Total water runoff is then compared to the ranges in Table 1 [of Appendix C] to designate the water year class.”

In fact, the 50% exceedence value enables a substantially more accurate forecast of a water year class than the 90% exceedence value. Program staff have determined that use of the 90% exceedence criterion would under-predict (i.e. predict a drier year than actually occurred) the actual water year class in 18 of the 49 years from which the necessary records were available to conduct the analysis. Of the 18 years, 8 years had later rain events in May or June.

The results of such under-prediction would negatively affect the successful implementation of the Program. The identification and evaluation of impacts associated with the alternatives evaluated in the FEIS were based on the historic hydrology of the Trinity River, and how that water was allocated between diversions to the Central Valley Project and flows down the Trinity River. The modeling of impacts associated with each alternative, especially with regard to impacts to water supply delivery and hydropower generation by the CVP for any given year class, was based upon what actually happened in that water year class historically, not upon what an April 1 forecast using a 90 percent exceedence criterion would have been.

As documented in the Final Report on the TRFES and in the FEIS, the majority of the geomorphic work to restore and maintain anadromous fishery habitat in the mainstem of the Trinity River is expected to occur during “wet” and “extremely wet” years. Continued use of the 90 percent exceedence criterion would result in a failure to experience the number of wet years anticipated by the ROD over the extended implementation of the Program, which would jeopardize the success of the Program.

Reclamation is correcting the reference to the April 1 exceedence criterion from 90 percent to 50 percent, based upon investigations by Program staff, with input from the Hoopa Valley Tribe and the Trinity Adaptive Management Working Group (TAMWG). Program staff determined that use of the 50 percent criterion would correctly predict 44 of 49 of the years for which the necessary records were available. Additionally, of the remaining years, three resulted in underestimating the year class and two resulted in overestimating the year class. The resultant accuracy rate when using the 50 percent exceedence criterion is approximately 90 percent when compared to the historic record, with the errors almost balanced in over and under predicting the water year class. Thus the 50 percent exceedence criterion is approximately 90 percent accurate while the 90 percent exceedence criterion success rate is only slightly above 63 percent, with the errors consistently resulting in a prediction that is drier than that which ultimately occurs. This correction will not affect the decision adopted in the ROD or the supporting environmental analysis in the FEIS.

The Department hereby corrects the process by which the water year class is identified in the FEIS for the Trinity River Mainstem Fishery Restoration Program in order to implement the alternative selected in the ROD for the Program. The correction replaces the 90 percent exceedence criterion used by Reclamation to forecast runoff in the Trinity River watershed as of April 1 of each year, with a 50 percent exceedence criterion.

Submitting Comments

The Secretary is not proposing to take any new action as a result of this Federal Register notice. Accordingly, while the Department welcomes comments, the Department is not establishing a specific date by which comments must be submitted. Public comments on other aspects of this Adaptive Environmental Assessment and Management (AEAM) program may always be submitted to the TMC, the TAMWG, or the Executive Director.

Our practice is to make comments, including names and home addresses of respondents, available for public review. Individual respondents may request that we withhold their home address from public disclosure, which we will honor to the extent allowable by law. There also may be circumstances in which we would withhold a respondent's identity from public disclosure, as allowable by law. If you wish us to withhold your name and/or address, you must state this prominently at the beginning of your comment. We will make all submissions from organizations or businesses, and from individuals identifying themselves as representatives or officials of organizations or businesses, available for public disclosure in their entirety.

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Frank Michny,

Regional Environmental Officer, Mid-Pacific Region.

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[FR Doc. E6-6794 Filed 5-4-06; 8:45 am]