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HYDRO24435
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Last modified
8/24/2016 8:44:30 PM
Creation date
11/20/2007 4:41:01 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1982057
IBM Index Class Name
Hydrology
Doc Date
9/18/1992
Doc Name
SENECA II POND DESIGNS AVERAGE ANNUAL R METHOD
From
DMG
To
SUSAN MORRISON
Permit Index Doc Type
SEDIMENT POND INSPECTIONS
Media Type
D
Archive
No
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iii iiiiiiiiuiii iii ~ <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department o(Nawral Resources <br />1713 Sherman 51., Roam 215 <br />Denver, CO 80203 <br />Phone: (303) 8667567 <br />FAX: 13031 832-8106 <br />DATE: September 18, 1992 <br />TO: Susan Morrison <br />FROM: David Berry ~' <br />RE: Seneca II Pond Designs -Average Annual R Method <br />OF' ~~(O <br />ti~ a <br />~~: <br />~~^~, <br />/9~]6' <br />Roy Romer <br />Governor <br />ntichael B Long <br />Division Director <br />I have conducted a general review of the Seneca II pond design methodology. Specifically, <br />the sediment yield predictions for Pond 009 were reviewed. The methodology can be <br />accepted. <br />The operator originally predicted a total sediment yield to Pond 009 of 9.4 acre-feet (2.27 <br />acre-feet per year for 4.1 years) using the basic Universal Soil Loss Equation. The pond <br />volume was apparently designed, in part, based upon this calculation. The operator, <br />however, also used Sedcad to predict sediment yield (probably the Revised LISLE option) <br />for the purpose of water quality effluent prediction. Based upon this method, a total storm <br />volume of 317.3 tons of sediment was predicted. Recall that the USLE method predicted <br />a total annual sediment yield (2.27 acre-feet), and the Sedcad RUSLE method predicted a <br />storm-specific sediment yield (317.3 tons or approximately .18 acre-feet). <br />Note: I have not reviewed the adequacy of the parameters input to the sediment <br />yield models. You may or may not wish to have your hydrologist conduct <br />such a review. I have assumed that since the values are previously <br />approved, then the input parameters received an appropriate review. <br />The design information received subsequent to pond construction indicates a much <br />smaller as-built volume for sediment storage. Specifically, a total volume of 3.01 acre-feet <br />has been provided for sediment storage. The new submittal has eliminated the previous <br />USLE calculation (2.27 acre-feet/year), and it uses the "Average Annual R Method" as <br />found in the Sedcad manual page 14-4. The Sedcad Average Annual R Method requires <br />that the following variables be input by the user: R (annual), and the number of years <br />over which sediment will be accumulated. The storm specific sediment yield prediction <br />previously derived using Sedcad (in this case, 317.3 tons) is retrieved and automatically <br />input. The R (storm) is calculated by Sedcad. The program may not use the same tons to <br />acre-feet conversion as was given by the operator -- I am not sure about the factor used <br />by Sedcad. <br />The Sedcad RUSLE routine is expected to predict a lesser sediment yield than the basic <br />LISLE method originally used by the operator. This is a function of variable and calculation <br />differences between the two methods. Therefore, changing from the basic LISLE to the <br />Average Annual R method, utilizing the RUSLE method within the Average Annual R <br />
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