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1229 North 23~ Street, Suite 201 • Grand Junction, Colorado 91501 <br />(970) 241-6027 • Fex: (970) 256-7992 <br />~~ www.rhinoengineers.com • email: reinc23~tlwest.net <br />7tme 9, 200ti <br />Mr. Steve S. Shuey <br />Stain of Colorado <br />Division of Minerals and Geology <br />Department of Naittral Resources <br />1313 S1terman St, Raom 213 <br />Denver, Colorado 80203 <br />Re: Upland Gravel, Permit No. M-2001.088 <br />Application for Conversion to 112e (CN-01) <br />Response to Second Preliminary Adequacy Revtew Comments <br />Deer Mr. Shuey, <br />The following responses addrcas two cammeats regarding stormwater detention disclosed iut the <br />second prolitttittary adequacy review wmments. <br />The Upland Gravel property was divided into two drainage areas. Please refer to attached <br />Drainage Map- Drainage Area 1 will drain to the existing wash located in the southeast comer of <br />the property. Stormwater from the remaiaiag area, Arainage Arce 2, will be captured by the two <br />proposed gravel pits. The property was detenatvaed to be unaffected by offsite drainage. Please <br />refer to attached calculation sheets. <br />• Response To Commeat #3 <br />Since no outlet will be provided iut either grave) pit, the maximum 40-hoot release time will <br />depend on rho percolation rate of the Boils in each pit. According to aoJl percolation testing <br />conducted by Lincoln - DeVoze, lno. Geotechnical Consultants, an average sell percolation <br />rate of 20 minutes per Inch (based on 27 exploration pits) was identidaed fez High Aesert Aft <br />Subdivision located immediately west of Upland Gravel pzoptxry. <br />Using m average percoladon rate of 20 minutes per inch, the rcleaae time for the stozagc <br />depths in Pit #1 aad Pit #2 identified below in the response to Comment #13 weze calculated <br />as 10 hours and 4 booze respectively. This complies with the 40-hoot maximum release time. <br />• Response To Commem #13 <br />The ] 0 year, 24-hour storm event will wntribute a total of approximately 14,500 cubic fee oP <br />stormwater ro Pit # 1, with a maximum depth of 2.5 feet, Maximum storage is Pit u2 will be <br />4,750 cubic feet with a depth of 1.0 feet. Storage dtptlts were calculated utilizing proposed <br />caltotu's as shown in dte attached prainage Map. <br />$erytng Ca/oreOa, (Nab & Nevetla <br />