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Blue Pit 112 Permit Amendment <br />The concrete plant is not operated by Western Slope Aggregates and it is anticipated that upon <br />mining and reclamation being completed the concrete plant will remain in place. No revegetation <br />is planned in the industrial area since it is currently being used for that purpose. The access road <br />leading to the concrete plant will also remain in place until the concrete plant is removed. The <br />concrete plant will have some stockpiles associated with it. The entire facility will be within the <br />reclaimed pit. The pit will have sufficient capacity to prevent stormwater discharges from ever <br />occurring. Therefore, the concrete plant facility does not require additional drainage control. <br />The Stormwater Catchment Benches <br />The slopes of the reclaimed Blue Pit are very long and need to be protected from erosion. The <br />maximum amount of unbroken slope that will be allowed in the reclamation is 30 vertical feet. The <br />breaks in the slope are going to be the Stormwater Catchment Benches which will collect the water <br />and transport it to the Grouted Channels, which bring the water to the bottom of the site. The <br />Stormwater Catchment Bench design is shown below. <br />Longest segment of Stormwater Catchment Bench <br />Curve Number <br />Drainage Basin Area <br />Precipitation Event <br />Type II Storm Rainfall <br />Runoff <br />Watercourse slope <br />Time of Concentration <br />Peak Discharge <br />Side Slopes <br />Manning Coefficient <br />Depth of Flow <br />Freeboard Depth <br />The Grouted Channels <br />2,700 feet <br />79 <br />6.19 acres <br />24 Hour ioo year <br />2.4 in <br />0.4o acre -ft <br />2.0% <br />19.7 min <br />4.07 cfs <br />3H:1V, 8H:1V <br />0.02 <br />o.65 feet <br />o.10 Feet <br />The Stormwater Catchment Benches collect the water from the slopes and transfer it to the Grouted <br />Channel to be taken to the pit floor. There are three grouted channels planned at the Blue Pit. All <br />channels will have the same design and the channel in the northeast portion of Mining Area 1, <br />which receives the most water, will be the basis of the design. This grouted channel receives runoff <br />from multiple catchment benches and the longest one was used to figure the time of concentration. <br />Longest segment of Grouted Channel <br />Curve Number <br />Drainage Basin Area <br />Precipitation Event <br />2,100 feet <br />79 <br />18.9 acres <br />24 Hour loo year <br />Blue Pit May 2014 G -3 <br />