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negligible, because these structures have been designed to minimize impacts to the <br />• hydrologic balance (see Tab 13, Facilities). The diversions and culverts involve such <br />minor areas of disturbance that chemical and sediment changes in the flows will be <br />unmeasurable. <br />Effects of Runoff from Reclaimed Areas on the Quantity of Streamflow. The effects of <br />runoff from the proposed Nucla East mining area on Streamflow quantity (runoff and <br />sediment loads) have been estimated using the lumped-parameter computer model SEDIMOT II. <br />The impacts of runoff from reclaimed areas established at the Nucla Mine are inferred from <br />this modeling exercise. As previously mentioned, the absence of detailed premining <br />mapping, and also the lack of comprehensive soils and vegetation data for the Nucla Mine <br />prior to the onset of mining precludes the use of SEDIMOT II to obtain meaningful <br />premining estimates of runoff and sediment loads for comparison with postmining estimates. <br />SEDIMOT II has been developed to predict runoff and sediment loads from watersheds that <br />have been mined or are in the process of active mining. Input parameters take into <br />account precipitation, soils, topography and vegetation. Adjustment of these parameters <br />allows for the evaluation of watershed response changes resulting from mining. <br />• <br />Input parameters selected for the model reflect both premining and postmining (reclaimed) <br />conditions, and resulted in two separate model outputs: 1) premining runoff and sediment <br />loads; and 2) postmining runoff and sediment loads. Both outputs include runoff volumes <br />and rates (peak discharge), sediment concentrations and sediment yields. The following <br />sections discuss the scope of the modeling efforts, the selection of input parameters, and <br />a summary of the model results with corresponding significance determinations. The reader <br />should refer to the SEDIMOT II Manual on'Modeling Techniques (Wilson, et al., 1981) and <br />the SEDIMOT II User's Manual (Warner, et al., 1981) for reference. <br />The watershed area directly above the proposed 007 pond (Nucla East mining area) was <br />selected for evaluating runoff and sediment loads using SEDIMOT II. The small area <br />located in the southeastern portion of the Nucla East mining area that is drained by the <br />proposed diversion ditch was not included, as both the diversion and the sediment pond <br />will be removed after bond release (postmining conditions). Exhibits 17-1 and 17-2 <br />present the approximate drainage areas and respective topographies for both premining and <br />postmining conditions. <br />• <br />17-82 Revised 04/11/88 <br />