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• GCC RIO GRANDE -RED ROCK PLANT AND MINE <br />SURFACE WATER MANAGEMENT PLAN <br />INTRODUCTION <br />Purpose and Scope <br />This plan describes temporary and permanent surface-water drainage facilities for <br />managing storm water from the Red Rock Plant and Mine (Project). The objective of surface <br />water management is to mitigate drainage impacts during mining and restore drainage conditions <br />after mining to be as good as or better than existing conditions at the site. Drainage impacts aze <br />measured in terms of runoff peak flows, runoff volume, and sediment transport. <br />The plan was prepazed to investigate the technical feasibility of recommended drainage <br />facilities and to provide technical basis For the Regular 112 Operations Application for Mining <br />Permit required by the Colorado Division of Minerals and Geology (Division). <br />The plan is organized as follows: <br />^ Introduction presents the plan's purpose and scope, describes the Project location, and <br />• identifies reference guidance documents. <br />^ Hydrologic Analysis for Existing Conditions explains analysis approach and <br />discusses existing watersheds, precipitation, soil pazameters, and other site <br />information relevant to understanding current drainage conditions. <br />^ Surface Water Management Plan discusses facilities to be used prior to mining, <br />during mining, and after reclamation for achieving surface-water management <br />objectives. The text of the plan provides an overview of the Project approach for <br />managing storm water runoff, and appendices contain calculations and in-depth <br />design information. The plan also addresses process and sanitary wastewater <br />management. <br />^ ASCE Manual of Practice No. 77 (ASCE 1992). The procedures, methodologies, and <br />criteria used to prepare this Storm Water Management Plan aze industry standazds <br />that appear in many documents. The ASCE Manual of Practice summarizes these <br />requirements and was used for guidance in preparing this plan, particulazly the <br />analysis of risk when determining design frequency. <br />The plan supports the Project's associated General Permit for Storm Water Discharges <br />Associated with Heavy Industrial Activity (General Permit), issued by the Colorado Department <br />of Public Health and Environment (CDPHE Stormwater. The General Permit requires a Storm <br />• water Management Plan (SWMP) to be prepared that describes management controls for <br />SWMP BC June 28 2002.doc, 06/28/02 <br />