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:: <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />303 866-3567 <br />RA x: 303 832~e106 <br />~II ~I~II~~I~I~~~ ~~~ <br />STATE OF COLUxAUU <br />pF COrO <br />l~ ~~90 <br />© ~ <br />' C' <br />. '4„_v <br />~ /876 <br />Roy Ramer. <br />Gwengr <br />Michael B. long, <br />Division D~rettor <br />DATE: May 14, 1992 <br />T0: Steve Wathen, Larry Routten <br />FROM: Kent Gorham ~~7 <br />RE: Colowyo, Prospect Pond Review <br />I have completed my review of the surface water hydrology for the Prospect <br />Pond and associated watershed. The documents reviewed consisted of the <br />SEDCAD+ run submitted by the operator, Maps 4, 12 and 23, Curve Number <br />Justification Document, and a memo by Steve Wathen dated May 1, 1992. <br />Additionally, the SEDCAD+ Users Manual and the Johnson Hydrologic Model from <br />the Trapper Mine were reviewed. My comments are as follows: <br />Points of Disagreement <br />The operator wishes to use two land conditions, undisturbed <br />rangeland and fully reclaimed grassland to describe the watershed <br />for the Prospect Pond design. Clearly this is inappropriate since <br />it does not consider the acreage that would be devoid of vegetation <br />for a considerable time between backfilling and grading and <br />sufficient vegetation establishment to control erosion. This <br />period is estimated to be 1-3 years. <br />2. The operator also states that the pit is itself a sediment pond and <br />traps a large amount of surface runoff which would otherwise go to <br />the sediment pond. I agree that this condition will exist but the <br />operator did not supply any data to indicate the areas which would <br />not flow to the pond. <br />3. The operator did not supply watershed information on his map that <br />could be used to review his SEDCAD+ model. Additionally, the <br />operator did not include particle size information. <br />