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2021-06-03_PERMIT FILE - M2021021
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2021-06-03_PERMIT FILE - M2021021
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Last modified
1/26/2025 6:01:42 AM
Creation date
6/9/2021 6:33:45 AM
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Template:
DRMS Permit Index
Permit No
M2021021
IBM Index Class Name
PERMIT FILE
Doc Date
6/3/2021
Doc Name
Adequacy Review Response
From
IHC Scott
To
DRMS
Email Name
ACY
Media Type
D
Archive
No
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Rifle Gravel Pit #1 June 2021 <br /> 8.6.1 Water Requirements During Mining Phase <br /> During active mining, depletions to the Colorado River will occur from water lost with mined <br /> aggregate (trucked offsite with mined aggregate) and water used for dust control. Depletions <br /> are not expected from evaporation associated with dewatering efforts; Scott plans to <br /> intercept any groundwater with perforated pipe and pump it to the dewatering pipeline <br /> without evaporation. Gravel pit operations also typically include domestic or commercial <br /> indoor uses; however, Scott expects to provide trucked water from offsite for indoor water <br /> use. <br /> 8.6.2 Water Lost with Mined Aggregate <br /> Scott estimated for the entire property they could meet a production rate of 200,000 tons of <br /> aggregate per year, or 16,667 tons per month assuming a year-round operation. DWR-SEO <br /> uses a standard assumption that aggregate production water depletions are four percent of <br /> the production rate when washed and mined below the groundwater table, which results in <br /> total annual demand of 5.89 acre-feet (AF)for 200,000 tons of aggregate. <br /> 8.6.3 Water Used for Dust Control <br /> Dust control water will be captured from the dewatering well. Scott estimates that the active <br /> mining operations will use 50,000 gallons per day for dust suppression. Based on 20 <br /> operational days per month, this results in an annual demand of 36.83 AF. <br /> 8.6.4 Water Lost Due to Evaporation During Dewatering <br /> Evaporation from exposed groundwater during active mining is expected to be minimal. A <br /> series of dewatering wells (exact number unknown at this time but modeled and <br /> documented in Attachment B reports) will lower the local groundwater table at the site and <br /> allow for dry mining operations. In the instance mining exposes groundwater not pumped by <br /> the dewatering well, a perforated pipe will be buried in a trench at least 3 feet below the <br /> mining floor, allowing this water to be intercepted and directed to the dewatering well. <br /> Hence, it is assumed that no water is lost to evaporation during active mining. <br /> 8.6.5 Water Used Indoors (Domestic and Commercial) <br /> Scott does not anticipate using water from the site for indoor water demands. Because <br /> potable water is not available from City of Rifle or Town of Silt and because drilling a well for <br /> potable water on the property is not feasible given the mining plan, Scott is planning to truck <br /> potable water onto the site to supply employees with potable water. <br /> 8.6.6 Water Requirements During Reclamation Phase (Post Mining) <br /> After mining is completed, water depletions from the site will be solely from evaporation of <br /> the exposed groundwater in the finished gravel pit pond. Annual gross evaporation for the <br /> Rifle area is estimated at 45 inches based on the contours from National Oceanic and <br /> Atmospheric Administration Technical Report NWS 33 dated June 1982, Map No. 3. Annual <br /> evaporation was distributed annually using the DWR General Guidelines for Substitute <br /> Water Supply Plans for Sand and Gravel Pits (DWR Gravel Pit Guidelines) annual <br /> distribution for elevations below 6,500 feet. The evaporation was then reduced to account <br /> for periods when the pit is expected to be frozen over when the average temperature is <br /> below freezing, typically December through February for Rifle. <br /> 36 <br />
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