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<br /> <br />iii iiiiiiiiniu iii <br />STATE OF COLORADO <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 />Fax 303 832-8106 <br />04 cow <br />~~'~> <br />ne <br />`~ (TQQ7 ~ <br />~ r876 <br />Roy AOmer. <br />Governor <br />Fred A. Barra, <br />Division Director <br />October 7, 1991 <br />Twin Pines Limited Partnership <br />c/o Mr. Larry White <br />1650 M Street <br />Penrose, CO 81240 <br />RE: Technical Revision 4, Twin-Pi-nes No. 2 ,4ine <br />~~ ~ <br />Dear Mr. White: <br />The staff has completed their review of the sedimentation pond emergency <br />spillway revision. Please modify your submittal to respond to the following <br />issues: <br />1. Please use 2.6 inches for the 10-vear storm event, 3.0 inches for <br />the 25-year storm event and 4.0 inches for the 100_year storm <br />event, per the original application submittals. <br />2. As Twin Pines is attempting to provide documentation that the upper <br />bench pond does not need an emergency spillway through Rule <br />4.05.6(6)(b), you may want to route water from the upper bench and <br />the slope above the upper bench through the lower pond. <br />3. Please submit specifications from the geoweb manufacturer <br />documenting the Manning's 'n' available with the 2 to 3 inches <br />clear stone fill. Please document the limiting erosive velocity or <br />critical tracture force which the fill is capable of handling. <br />4. Please clarify the crest evaluation of the lower pond embankment. <br />The 'Lower Sediment Pond' figure indicates that the crest will be <br />5,736 feet, while the 'Analysis of Lower Pond' says it will be <br />5,735.5. <br />5. Please label the slopes of the outslope of the embankment on the <br />lower pond on Sketch No. TPS-Z. <br />