Laserfiche WebLink
B. <br />' 1. <br />2. <br />3. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />r <br /> <br /> <br /> <br />Specific Details <br />Discussion of drainage problems encountered. One possible drainage problem with a <br />runoff retention approach is potential flooding of the active mining and processing areas. <br />As mining progresses to the low points in the sub-basins, runoff from larger storm events <br />could accumulate and back up or rise into the processing azea. CMI has experienced this <br />situation at the Ditmaz Quarry, but ponding usually infiltrates or evaporates within two to <br />three days. In addition, CMI will use the erosion control techniques discussed above to <br />help reduce inundation of the active areas. <br />Discussion of detention storage and outle[ design. Not applicable. <br />Discussion of maintenance access. Maintenance will be required for the erosion and <br />sediment control structures. Most of these structures will be located near the active <br />mining azea or along roadways. There aze no foreseeable problems in accessing these <br />structures for maintenance. <br />4. Discussion of easements and tracts for drainage purposes. CMI will help confine <br />drainage to the pit azea by prohibiting mining disturbance within 100 feet from the mesa <br />edge and the minor draingeways. <br />A. Compliance with Standard <br />V CONCLUSIONS <br />The Phase III Drainage Study report and plans are in compliance with the standards set <br />forth in the DCSDDTC manual. The submittal requirements for this study have been <br />carefully reviewed and executed. <br />B. Drainage Concept <br />CMI plans to confine drainage to the Castle Rock Quarry site. This stormwater retention <br />will be accomplished by leaving a 100 foot wide rim of undisturbed ryholite around the <br />cut stone and crushed stone pits. This study demonstrates that the final pit configuration <br />contains adequate storage to contain back-to-back 100-yeaz 24-hour storm events. There <br />is also adequate freeboazd (minimum 2 feet) to contain additional stormwater. These <br />figures have been outlined in the Post-Mining Storage Volume Tables on the Post-Mining <br />Plan Maps. <br />This drainage concept will confine erosion and sedimentation to the areas of disturbance. <br />Drainage to the active mining area will be trapped in the pit. Thus, any sediment carried <br />by storm runoff will be contained on-site. Erosion and sediment control techniques will <br />be used to minimize any disturbance. In addition, reclamation will be concurrent with <br />mining so the total area of distwbance will be no more than 60 acres at any time in the <br />life of the mine. <br />12 <br />