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deliver the water to the river as shown on Map C-2. Prior to any mining operations, this sedi- <br />ment control system will be installed. The inlet to the ditch will be fitted with a sliding gate <br />so that the outflow to the river can be shut down if the water has not had enough time to set- <br />tle out the suspended solids. An NPDES Permit, COG-500328, is active for the discharge <br />from the entire site although its outfall location will need to be moved to the discharge from <br />the settling basin described above. Water discharge will be sampled according to [he parame- <br />ters of the NPDES permit for this discharge. In any case, the discharge will be short-lived <br />(only during pit excavation fot 3 months). After this time, the pit lake will be allowed to fill <br />up to its water equilibrium level, which is expected to be slightly higher than the river water <br />elevation, as shown on Map C-4. <br />B- Protecting the Embankment <br />The plan for protecting the embankment consists of 4 items. First, a jetty made from large <br />durable rock will be placed immediately upstream of the lake to direct water away from the <br />lake embankment. Second, two rows of special-formed concrete blocks will be placed along <br />the toe of the embankment facing the river. Third, the upper portion of the embankment will <br />be topsoiled to a depth of 14 inches and will be seeded with an aggressive native mix suited <br />for this location. Fourth, an Excelsior erosion control fabric will be placed on top of the <br />seeded soil embankment to provide long term bank protection. This was chosen to provide <br />protection for the bank while providing a more aesthetic and natural slope. <br />Item 1 -Rock Jetty <br />The rock jetty will consist of durable, angular rock of minimum size DSo = 4.75 feet. The rock <br />will be either awell-cemented sandstone or igneous/metamorphic rock that is durable. It willl <br />be placed as shown on Map C-6. The location and height of the jetty is meant to direct the <br />water from the 100 year event away from the lake embankment. The jetty will be at least 9 <br />feet wide at the top and will have O.SH:I.OV sideslopes. This sideslope can be used only <br />when the rock boulders are angular and carefully placed to make the jetty stable. The top ele- <br />vation of the jetty is 6665.0 feet, which is 1.5 feet below the elevation of the 100 year flood at <br />this particular location in the river. This elevation was determined from the US Army Corps <br />Received <br />Thomas Pit 2/02 14 <br />MAR O 7 2002 <br />Durango Field Office <br />Division of Minerals & Geology <br />