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2 . 41 <br />2.4 Mining Hydrology <br />• The objective of related studies was to provide an evaluation of the hydrologic impact that the project <br />will have on the mine area, and to serve as a basis for final design of diversion and sedimentation control <br />facilities. <br />2.4.1 Surtace Water Hydrologic Controls <br />The surface runoff area has been subdivided into "disturbed" and "undisturbed" areas. Runoff <br />from most disturbed areaz will be conveyed into a sedimentation pond and detained in accordance <br />with applicable criteria before eventual discharge into East Sak Creek Runoff from three areas <br />addressed in Section 2.4.4.2 will be treated with alternate control meazures. Runoff from the <br />undisturbed areaz will be diverted around the disturbed area, and conveyed to the receiving <br />ephemeral channel. Figure 2.2-3 depicts the flow of water azsociated with disturbed and undisturbed <br />areas. <br />• The undisturbed area waz divided into sub-basins designated C-I through C-15. The disturbed <br />area is divided into four sub-basins, designated D- I through D-4. These sub-basins during mining are <br />shown in Figures 2.2-3 and 4.2-1a; their areas and hydrologic parameters are given on Table 4.2-10. <br />The sub-basins vary in size from 3 acres of disturbed area up to 322 acres for the main McClave <br />Creek drainage, see Figure 4.2- I a. Rainfall values fora 10-year, 24-hour storm were taken from the <br />NOAA Atlas; runoff was estimated according to Soil Conservation Service procedures, as given in <br />Procedures for Determining Peak Flows in Colorado. <br />Runoff nlculations for the reclaimed configuration of the mine site are shown on Table 4.2-I I. <br />Table 3.1-I contains the alculations for ditch and rip rap sizing. To provide the necessary detail to <br />evaluate the drainage basin boundaries after mining, the areaz are desiniated on Figures 4.2- I b and <br />3.1-I. <br />~~ <br />Mo Volume 1 10-12.97 <br />