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1 <br />I~ <br />~~96 <br />Wrighl Water Engineers, Inc. <br />DENVER OFFICE TULSA OFFICE GLENWOOD SPRINGS OFFICE <br />2490 West 26th Ave.. Suite SSA 707 South Houston, Suite 302 818 Colorado Avenue <br />Denver, Colorado 80211 Tulsa, Oklahoma 74127 P.O. Box 219 <br />(3031 480-1700 (9181 584-7136 Glenwood, Springs, Colorado 81602 <br />January 26, 1987 1303) 945-7755 <br />Denver Direct Line: 893-1608 <br />SUPPLEMENT TO ENGINEERING REPORT <br />Paula Phillips IdATER AUG)4ENTATION ALAN FOR WEST <br />Carlson, Hammond s Paddock, P.C. ELK COAL COMPANY, JULY, 1986 <br />1700 Lincoln Street, Suite 2750 <br />Denver, CO 80203 <br />Re: West Elk Coal Company's Plan of Augmentation <br />Case No. 86CW38 <br />Dear Ms. Phillips: <br />This is an ammended version of our letter dated November 21, 1986, in res- <br />ponse to three items that the State Engineer's Office would like to see <br />clarified regarding the July 1986 Engineering Report for the West Elk Coal <br />Company Water Augmentation Plan. The items covered in this letter are 1) <br />contribution factors, 2) historic return flows, and 3) augmentation credit <br />administration. <br />Contribution Factors <br />A contribution factor, as defined in this augmentation plan is the ratio of <br />tributary stream flow to Minnesota Creek stream flow. The factors are <br />based on average monthly flow. There are 12 contibution factors for Lick <br />Creek and 12 for Dry Fork. <br />The West Elk Coal Company Plan of Augmentation calculates stream depletions <br />l by comparing the actual (tmeasured) flows (Dry Fork and Lick Creek) with <br />"expected" flows. Expected flows are determined on the basis of historic <br />flow correlations between Minnesota Creek and the potentially affected <br />stream. A table of "Contribution Factors" was developed which defines the <br />expected flow in Dry Fork and Lick Creek as a percentage of Minnesota Creek <br />flow. <br />The average monthly flow in Minnesota Creek was determined using U.S. Geo- <br />l~ logical Survey records for the Minnesota Creek Gage near Paonia which oper- <br />1 <br />