PERMFILE57953 - Laserfiche WebLink

Home Browse Search

Therefore the actual consumptive use after mining will be 21.7 ac ft/yr - 10.66 ac-ft/yr = 1 ] .04 acre feet/vr• This will occur every year that the lake is in place. For the years of mining, a substitute water supply plan will be submitted to the Division of Water Resources for 2.59 acre feet per year. After mining, this amount will be changed to 11.04 acre feet per yeaz. These are the amounts that will be supplemented in the augmentation plan submitted to the Division of Water Resources. The landowner will maintain this augmentation plan after the site is reclaimed. 5. Drainage Facilities The overall design of the sediment control system is to do the following: 1) ensure that water pumped from the dewatering trench into the Farnsworth Collection Ditch to the south will be clean and that the wetland at the bottom will be maintained. 2) contain the runoff from all disturbed areas for the 100 year - 24 hour storm. 3) keep undisturbed water from entering the site for all storms up to the 100 year 24 hour event. As described in the general discussion of the mine plan, a 2' topsoil berm will be used along all sides of the permit area to isolate water on and off the property except for the north side, which will have a lazger topsoil stockpile berm. The slopes of these berms will be 2H:1 V. The irrigation ditch south of Farnsworth Collection Ditch will prevent any water from the south from entering the prop- erty. A small irrigation ditch east of the permit area also prevents any water from entering the site from this direction. Since the operation involves pure excavation of the resource, all water from the pit areas and facility areas will be detained within the 10 acre permit for the 100 year event. It is estimated that the pumping operation may move 1000 to 2000 gallons per minute into the Ditch initially, which will likely lessen to approximately 500 gallons per minute once the site is somewhat dewatered. These flow estimates aze dependent upon the ability of water to flow through the gravel itself, which will not be exactly known until the operation is started. It is expected that the pump will deliver the water to a PVC pipe that enter the Ditch, as shown on Map E-1. All discharges will be regulated under a combined storm water/process water permit that has been applied for with the Colorado Department of Public Health and Environment. As described earlier in this section, the water must go through two sets of gravel berms to get to the pump. The pumped water will be fre- quentlymonitored for compliance with this permit. If the water quality is out of compliance, water will not be pumped until it is in compliance. North Fork Pit Mazch 04 20