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concentration on the order of 1000 mg/1 or less. Trace elements <br />concentrations will be very small with iron and manganese being present <br />at levels of about 0.3 mg/1 and 0.03 mg/l, respectively. These <br />conclusions are based on the chemical analyses of the final effluent <br />samples from the leach tests conducted on existing refuse. <br />As mentioned previously, surface runoff from the exposed refuse <br />will be routed to a sediment pond. The pond is designed to retain for <br />at least 24 hours the total runoff from a 24 hour storm with a 10 year <br />recurrence interval. Applicable limitations on suspended and settleable <br />solids will be achieved prior to discharge. <br />Average precipitation at the New Elk Mine is about 17 inches per <br />year. In an abnormally wet year, the annual precipitation may be as <br />great as 23 inches. The corresponding quantities of direct runoff from <br />the refuse are estimated at 1.5 and 2.5 inches per year. Expressed as <br />a percentage of precipitation, these runoff values are somewhat greater <br />than the measured values for entire watershed above the Madrid gaging <br />station. The maximum surface area of exposed refuse will be about 66 <br />acres. The expected range of runoff volume is 7.6 - 12.7 ac-ft/yr. <br />Using a total dissolved solids concentration of 1000 m9/1 for discharge <br />from the sediment pond, about 10 to 17 tons of dissolved solids will be <br />added to the river in the year of maximum exposed refuse area. These <br />values of salt loading represent 0.1 to 0.2 percent of the total salt <br />load as measured at the Madrid gaging station. The corresponding average <br />increase of in -stream concentration of dissolved solids is 0.3 to 0.5 <br />mg/l. Furthermore, runoff from the refuse will occur when runoff is high <br />from other parts of the watershed and dilution will be a maximum. <br />The proposed refuse pile will be located well above the floor of <br />the Picketwire Valley. The foundation material, beneath the generally <br />thin soil cover is bedrock that dips to the northeast, away from the <br />valley. The small draw in which the refuse is to be placed has incised <br />the bedrock,and the surface of contact between the refuse and the <br />foundation materials slopes steeply toward the river. <br />RN -6 <br />2.05-93 (Repaginated 10/21/16) <br />