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2023-02-01_HYDROLOGY - M2002120
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2023-02-01_HYDROLOGY - M2002120
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Last modified
2/7/2023 4:36:11 PM
Creation date
2/7/2023 10:34:48 AM
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Template:
DRMS Permit Index
Permit No
M2002120
IBM Index Class Name
Hydrology
Doc Date
2/1/2023
Doc Name
Substitute Water Supply Plan
From
DWR
To
Division of Water Resources
Email Name
ECS
MAC
Media Type
D
Archive
No
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Bernhardt Pit SWSP Page 2 of 5 <br /> February 1,2023 <br /> An alluvial well has been constructed to provide water for concrete batching. This well was constructed <br /> under permit no. 60729-F (WDID 0405678) and is located outside the boundaries of the existing slurry wall. <br /> The SWSP request does not seek to pump water from this well during the plan period. Well no. 60729-F has <br /> not been used for concrete batching since 2008 and all lagged depletions from previous pumping from the <br /> well have already impacted the stream. A flow meter has been installed on the well, as is required by <br /> condition of approval #9 on well permit no. 60729-F, and the meter is currently in compliance with the <br /> South Platte Well Measurement Rules. <br /> Depletions <br /> Mining operation at the site occurs within the approved liner of the slurry walls, therefore no water lost <br /> with the mined product is accounted for in the SWSP. Additionally, based on the analysis previously <br /> performed by the Applicant, there are no lagged depletions from past dewatering operations that will <br /> accrue to the river during this plan period. <br /> Evaporative Depletions <br /> The plan proposes to expose 4.3 acres of groundwater at the Bernhardt Pit within the settling ponds. Net <br /> evaporation is defined as gross evaporation less the consumptive use of water by vegetation that naturally <br /> occurred at the site prior to construction of the pit. The historical consumptive use was assumed to be <br /> equal to the effective precipitation. Evaporative depletions were calculated using a gross annual <br /> evaporation of 43.86 inches (based on the NOAA Technical Report NWS 33) with a credit of 9.29 inches for <br /> effective precipitation (based on an average annual precipitation of 13.27 inches for the Longmont weather <br /> station). Evaporative losses are 2.88 acre-feet/acre, or 12.39 acre-feet for this SWSP period as shown on <br /> attached Table 1. <br /> Operational Depletions <br /> Consumptive use of groundwater from the Bernhardt Pit consists of 0.18 acre-feet/month for on-site dust <br /> control, or 2.16 acre-feet for this SWSP period as shown on attached Table 1. <br /> Lagged Depletions <br /> The total consumptive use at this site during this plan period is 14.55 acre-feet (see attached Table 1). The <br /> depletions from evaporation and operational losses were lagged to the stream using a Glover analysis <br /> assuming a distance (X) from the centroid of the exposed ground water surface to the stream of 715 feet, <br /> a distance (W) to the impermeable boundary of 2,976 feet, a transmissivity (T) of 100,000 gpd/ft, and a <br /> specific yield (S) of 0.2. <br /> The total lagged depletions are 14.56 acre-feet for this SWSP period as shown on attached Tables 2 and <br /> 3. Depletions from mining operations at the Bernhardt site will impact the Big Thompson River upstream <br /> of the Evanstown Ditch (WDID 0400517). <br /> Replacements <br /> The proposed source of replacement for the Bernhardt pit is 14.56 acre-feet of leased water from the <br /> GMS of the CCWCD. The replacements will be delivered from the Bernhardt Reservoir (WDID 0403395 <br /> decreed in case no. 02CW269) and will accrue to the Big Thompson River in the same location that the <br /> lagged depletions from the Bernhardt Pit impacts the river, therefore, no river conveyance losses will be <br /> assessed. A copy of the Lease Agreement is attached to this letter. A monthly breakdown of depletions <br /> and replacements is shown in the attached Tables 3 and 4, respectively. <br />
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