2016-02-03_HYDROLOGY - M1979191

• Permit No: M1979191
• IBM Index Class Name: Hydrology
• Doc Date: 2/3/2016
• Doc Name: Substitute Water Supply Plan
• From: DNR Water Resources
• To: DRMS
• Email Name: ECS
• Media Type: D
• Archive: No

Middle Poudre Combined SWSP Page 3 of 8
February 3, 2016
A stream depletion model using the Glover method was used to calculate the lagged
depletions to the Cache La Poudre River. The alluvial aquifer model was used with the following
aquifer input parameters: transmissivity (T) = 45,000 gallons/day/foot; the distance of centroid of
the exposed ground water to the Cache La Poudre River (X) = 1,900 feet; the distance from the
parallel impermeable boundary to the Cache La Poudre River (W) = 4,800 feet; and the specific yield
(S) = 0.2.
The depletions to be replaced under this SWSP are summarized in Table B below. A monthly
breakdown of the lagged depletions can be found in the attached Table 1.
Table B - Depletion Summary (all amounts in acre-feet)
Evaporation Water Lost in Dust First Lagged Lagged Total
Site Name Total Dewatering Lagged
Loss Mined Product Control Fill Depletions
Depletions Depletions
Three Bells 33.19 21'57 19.33 N/A 91.58 90.23 Oa 90.23
Pit (732,725 tons)
a So long as the site is continuously dewatered, the water returned to the stream system is considered to be
adequate to offset depletions attributable to the dewatering.
Replacements
Replacement water for this combined plan will come from a combination of accretion credits
from past recharge of 5.0 shares of the Box Elder Ditch Company and past and projected recharge of
1.0 share of the Box Elder Ditch Company.
Lafarge previously owned and dedicated to this plan 5.0 shares in the Box Elder Ditch Company.
The 5.0 Box Elder Ditch Company shares were sold but recharge credits continue to be available for
replacement use under this combined plan for water that was delivered to recharge through the 2014
irrigation year. Accretions from past (2014 and earlier) recharge of the shares will continue to accrue
to the stream in 2016 and beyond. In addition, the Applicant obtained approval from Steamboat
Partners Investments, LLC for the use of their 1.0 Box Elder Ditch Company share in the 2015 and 2016
SWSPs.
The Box Elder Ditch is divided into 64 Box Elder Ditch Company ("BEDC") shares. The 5.0 shares
previously dedicated to this plan are from the group of 5.5 shares previously owned by Lafarge that
were historically associated with the Three Bells Farm. The 1.0 share owned by Steamboat Partners
comes from this same group of 5.5 shares. A total of 6.0 BEDC shares were historically utilized for the
irrigation of 344.3 acres at the Three Bells Farm. The historical consumptive use credit for the 6.0 BEDC
shares used to irrigate the Three Bells property was determined to be 307.0 acre-feet (51.2 acre-feet
per share), based on a historical consumptive use analysis submitted with the 2014 SWSP request.
Table 2 from the 2014 SWSP request shows the average ditch diversion for the Box Elder Ditch
from 1950 to 2007. Table 3 takes the average ditch diversions for the Box Elder Ditch from 1950 to 1984
and analyzes the historic consumptive use and return flows for the 6.0 BEDC shares. Table 4 breaks this
information down further to come up with the monthly historic farm headgate diversions and return
flows for the 5.0 BEDC shares previously utilized in this plan. As shown on Table 4, the average annual
farm headgate diversion associated with the subject 5.0 BEDC shares is 457.0 acre-feet (91.4 acre-feet
per share) with an associated return flow obligation of 201.1 acre-feet (40.2 acre-feet per share). This
leaves a net consumptive use credit of 255.9 acre-feet, or 51.2 acre-feet per share.