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VI. Surface Water Hydrology - Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05 <br />All of the above-mentioned sediment structures were designed and <br />constructed under the supervision of a registered professional engineer. <br />The ponds will contain the runoff from a 10-year, 24-hour precipitation <br />event without discharging. The emergency spillways will pass a 25-year, <br />24-hour event and still maintain the required freeboard. <br />Maintenance of the ponds includes periodic inspection to ensure the <br />integrity of the structure. Sediment volumes are checked monthly and <br />cleaned when 607. of the design sediment storage volume is attained. <br />Runoff from the Barren Ridge and Federal Lease Areas of the mine is <br />passed through one of two sedimentation ponds. These ponds (No. 004 and <br />005) serve to drain the runoff for at least 24 hours to allow solids to <br />settle out. The resulting discharge is able to meet federal and state <br />water discharge standards (NPDES limits). The Division reviewed the <br />adequacy of the operator's sediment control system to ensure that the <br />water quality discharge standards form these ponds will be met. <br />The discussion of the drainage and sediment control system for the <br />Federal Lease Area can be found in Volume I, Section 2.05-19 through 22 <br />of the federal Lease permit revision application. The sediment control <br />system is displayed on Map 8. Detailed engineered designs can be found <br />in Volume I, Exhibit 7. <br />Within the Federal Lease permit revision area the drainage and sediment <br />control system utilizes diversion to divert undisturbed drainage away <br />from the mine site. Check dams and riprap are used to reduce flow <br />velocities, and terraces are used on the backfilled areas to reduce the <br />potential of rilling and gullying on reclaimed slopes. One stipulation <br />was included in the Permit Revision No. 1 approval document regarding <br />sediment pond dewatering mechanisms. A second stipulation in that <br />approval document pertained to controlling erosive ditch velocities. <br />Both stipulation have been satisfactorily resolved. A number of <br />modifications to the runoff control structures for the Revision No. 1 and <br />Barren Ridge Areas (including issues addressed by the stipulations) which <br />were contained within Technical Revision 11 approved by the Division <br />March 15, 1985 and subsequently incorporated into the current permit <br />revision. <br />Stipulation No. 5 of the Permit Revision No. 1 Findings Document set <br />forth in the surface water monitoring schedule and parameters. The <br />monitoring requirements have been altered to some extent by Technical <br />Revision 12, approved January 19, 1986, which reduced the number of <br />required parameters and Minor Revision 21, approved June 9, 1986, which <br />required periodic ocular survey and reporting of spring and seep <br />development in the East Pit Area. <br />-7- <br />