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Water within this basin drains to the northwest where it can infiltrate into the soil. The surface <br /> drainage patterns will not be affected in these two basins until Phase 2 and 3 of mining. <br /> 6.1.1. Mining <br /> During all phases of mining, and for each drainage basin, surface water runoff will drain to the <br /> active mining pit. For Drainage Basin 1, some runoff will collect in the reclaimed lake. Map C-2 <br /> shows the anticipated drainage patterns during mining. The site road will be graded to drain into <br /> the pit area. Grading of the site to drain internally ensures that no sediment laden water flows <br /> enter the river or any other natural waterways. There is more than enough storage within the <br /> pits to contain the 5-year and 100-yr storm events. <br /> Water collected within the pit will be routed to the pit dewatering pump to be pumped to the <br /> existing lake, which acts as a settling pond. Process water from the processing area will drain to <br /> the existing lake. This settling pond will allow for suspended solids to settle so clean water can <br /> be discharged to the permitted discharge location in the Relief Ditch. As the water is being <br /> discharged into the drainage canal via a pump, the discharge rate can be controlled to prevent <br /> erosion of the ditch. <br /> 6.1.2. Post Reclamation <br /> The drainage patterns during mining will be retained following reclamation of the site. Any <br /> surface water runoff will collect in the reclaimed ponds where it can either infiltrate into the <br /> groundwater aquifer or evaporate. There is enough storage capacity above the anticipated lake <br /> level and the top of the lake to store the 5-year and 100-year storm events. More on those <br /> calculations is provided below. <br /> 6.1.3. Flood Protection <br /> The proposed Pit 3 gets as close as 100 feet from the Gunnison River on the north side. Due to <br /> this proximity to the river, measures will be taken to protect the riverbank from erosion during a <br /> flood event. An inflow and outflow structure will be constructed between the Gunnison River and <br /> north end of Pit 3 during the final stages of mining and reclamation of the pit. This structure will <br /> allow for the exchange of flood waters between the pit and river which prevents erosion of the <br /> riverbank. Details of the inflow/outflow structure are shown on Map F-1. <br /> 6.2. Disturbed Area Runoff <br /> During all stages of mining, there is enough water storage capacity to contain the 5-year and <br /> 100-year 24-hour storm events and prevent erosion from surface water discharge. The <br /> expected rainfall from these events at the Delta Paving Site is provided in Table G-2 below. <br /> Delta Paving Gravel Pit G-4 Lewicki&Associates <br /> September 2022 <br />