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RULE 4 PERFORMANCE STANDARDS <br />,v~..__ ~, ~..._ _. n ~,mr <br />_-~ W ,~ _r,,;,~.W,~,,_.z.-- <br />Sediment will be removed from all sedimentation ponds on an as needed basis or when the sediment level <br />will not allow effective treatment of the runoff resulting from the 10-yeaz, 24-hour precipitation event in <br />accordance with Rule 4.05.2. Quarterly inspections will note the level of sediment in each pond. Ponds <br />will typically be cleaned of sediment when water levels are lowest, and the least amount of precipitation <br />is expected. The removed sediment will be used as topsoil or subsoil if it meets the suitability criteria <br />discussed under Section 2.04.9. The Division will be notified of this determination if the material is <br />selected as overburden material that can be substituted for or as a supplement to topsoil. <br />All sedimentation ponds will be designed so that the minimum elevation at the top of the settled <br />embankment is at least one foot above the elevation of the water surface in the pond with the emergency <br />spillway flowing at design depth. <br />Colowyo will design, construct, and maintain the sedimentation ponds to prevent short-circuiting to the <br />extent possible. As a general rule, the inflow to the ponds will be at the opposite end from the outflow <br />azea. The constructed height of the sedimentation pond embankment will be designed to allow for <br />settling. During construction, a registered professional engineer will ensure that the appropriate <br />embankment height is accomplished. For all sedimentation ponds, the entire embankment, including the <br />surrounding areas disturbed by construction, will be seeded after the embankment is completed, using the <br />Topsoil Stockpile/Pond Embankment seed mix described below. The active upstream side of the <br />embankment where water will be impounded will be riprapped or otherwise stabilized, where necessary. <br />Areas in which revegetation is not successful or, where rills and gullies develop, will be repaired and <br />revegetated. <br />Colowyo will inspect the condition of each sediment pond, sediment trap, orfuture postmining stock <br />reservoir on a quarterly basis. All of these types of structures meet the requirements of an impoundment, <br />and the inspection procedures will meet the requirements under Rule 4.05.9 (17). Previously, Colowyo <br />has received a waiver from quarterly inspections for several existing stock reservoirs within the current <br />permit area as described under Section 4.05.9. This waiver changed the inspection frequency to annual. <br />Following construction of any future postmining stock reservoir proposed in the South Taylor area, <br />Colowyo may request a similaz waiver but until that is approved, the quarterly frequency would apply. <br />Results of all impoundment inspections will be submitted annually. <br />Topsoil Stockoile/Pond Embankment Seed Mix* <br />Western wheatgrass @ 4 Lbs PLS/Acre <br />Thickspike wheatgrass** @ 4 Lbs PLS/Acre <br />Yarrow*** @ 0.15 Lbs Pls/Acre <br />*mix will be modified as a result of an updated Reclamation Plan submitted after PR-02 approval. <br />Colowyo existing permit Section 4.06.3 must be modified to reference the updated seed mix in this location <br />at that time. <br />**option to replace Thickspike wheatgrass with Beardless bluebunch wheatgrass or Sheep fescue <br />***option to replace Yarrow with Cicer milkvetch <br /> <br />South Taylor/t.ower Wilson-Rule 4, Page 10 Revision Date: 3/30/07 <br />Revision No.: PR-02 <br />