BOARD00431

• Board Meeting Date: 5/24/1999
• Description: ISF Section - Request for Findings of De Minimis Impact - Henderson Mine
• Board Meetings - Doc Type: Memo

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Colorado Water Conservation Board

Department of Natural Resources
1313 Sherman Street
Denver, Colorado 80203
Phone: [phone]
fAX: [phone]

STATE OF COLOMDO

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MEMORANDUM

Bill Owens
Governor

To:

CregE. Walcher
Executive Director, DNR
PeterH. Evans
Director, ewes

Members, Colorado Water Conservation Board

From: Dan Merriman,
Greg Espegren

Date: May 12, 1999

Re: Agenda Item 13, May 24,1999, Board Meeting-
lnstream Flow Program - Request for finding of De Minimis impact - Henderson Mine

Staff received the attached letter from W.W. Wheeler and Associates, Inc. regarding a proposed
substitute supply plan for water uses at the Henderson Mine, located on the Williams Fork River
near Parshall in Grand County, The letter states that anticipated depletions to the Williams Fork
River and South Fork Williams Fork River will be less than 1% of the Board's decreed instream
flow water rights (see Table 4 of the attached letter report). The letter requests that the Board
make a de minimis determination so that the State Engineer's Office may grant their request for a
substitute supply plan through December 2000. The CWCB staff has been in contact with the
State Engineers Office and they have indicated that they will grant the requested substitute
supply plan if the de minimis impact is approved by theCWCB.

Prior to this request, there has only been one other de minimis impact within the Williams Fork
River drainage basin, That 0.10 cfs impact occurred within the most downstream Williams Fork
River insiream flow segment, located between Keyser Creek and Williams Fork Reservoir. It
resulted in a 0.263% impact to the Board's summer instream flow right and a 0.526% impact to
the Board's winter instream flow right.

The de minimis impacts associated with the proposed substitute supply plan at the Henderson
Mine will range between 0.01 and 0.10 percent depending on the reach of stream affected and
the time of year. The impacts will not cause a cumulative impact of greater than I % to any of
the Board's Williams Fork River or South Fork Williams Fork River instream flow water rights.

Staff Recommendation
Based on the information presented in the attached letter and this memorandum, staff
recommends that the Board make a determination that the impacts associated with substitute
supply plan, as described in the attached letter, will result in a de minimis depletion to the
Board's Williams Fork River and South Fork Williams Fork River instream flow water rights.

L:\BOARDMEM\May 99\13 May 99 Henderson Mine de minimis detennination.doc