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• The design calculations for determining runoff and sediment storage <br />requirements, pond dewatering and emergency spillway design are provided in <br />the appendix to this exhibit. Anon-clogging dewatering device is designed as <br />a corrigated plastic sheet perforated with numerous 1 1/2 inch holes placed <br />around the principal spillway riser below an access platform. <br />Pond Water Treatment <br />Water entering the pond from a pipe draining abandoned underground workings on <br />the site (Map 12) has indicated pH measurements below 6 standard units. <br />Discharges vary dependent on time of the year. Pumpage of water from the <br />active mine workings and surface drainage may also be acidic. In order to <br />maintain the pond effluent within NPDES requirements, treatment of water to <br />• neutralize acidity may be required. The plan for pond water treatment will be <br /> followed as described below: <br />1. Monitor pH of pond water on a weekly basis. <br />2. If pH falls below 7.0, addition of lime (calcium carbonate) in <br />sufficient quantities to bring the water to a pH of 7.0 will be <br />performed prior to any discharge from the pond. Lime will be hand <br />spread on the pond water surface away from the outlet and near the <br />portal inflow location. <br />3. Quantities of lime to be added to the pond to adjust the pH from 6 to <br />7 are based on the following relationships: <br />r1 <br />Revised 9/12/86 <br />3 <br />