2021-10-19_HYDROLOGY - M2001085 ‎(2)‎

• Permit No: M2001085
• IBM Index Class Name: Hydrology
• Doc Date: 10/19/2021
• Doc Name: Substitute Water Supply Plan
• From: DWR
• To: DRMS
• Email Name: JPL
• Email Name: JLE
• Archive: No

GSL Sand St Gravel Substitute Water Supply Plan Page 2 of 5
October 19, 2021
in November 2014 the Applicant began backfilling the pond which reduced the exposed groundwater
surface. As of September 2020, current exposed groundwater surface area is 0.90 acres.
Net evaporative depletions were calculated using a gross annual evaporation of 45 inches from the
exposed water surface, with a credit of 10.8 inches for effective precipitation. The net depletion
of groundwater due to evaporation of groundwater exposed at the site has been calculated to be
2.59 acre-feet for the November 1, 2021 through October 31, 2022 period. The mining depletions
from January 2009 through October 31, 2022 are shown in attached Table 2.
The Alluvial Water Accounting System ("AWAS") model was used with the alluvial aquifer boundary
condition option to lag depletions to the South Platte River. The following parameters were used in
the model:
X- Dist to W- Boundary Harmonic
Location river (feet) Dist (feet) Transmissivity Specific yield
(gpd/ft)
Gravel Mine (mining and 2,295 3,836 63,000 0.2
dewatering depletions)
Henderson Water Ski Lake 1,808 5,300 61,600 0.2
(recharge)
Evaporative and operational losses were considered back to January 1, 2009. Total consumptive use
is 2.59 acre-feet per year, and lagged evaporative and operational depletions are 2.78 acre-feet for
this SWSP period, as shown on the attached Tables 3 and 4. Dewatering depletions and accretions
were also considered back to January 1, 2009.
Replacements
The replacement source for this plan period is fully consumable water leased from the City of Aurora
("Aurora"). The fully consumable water will be released to the South Platte River at the outfall of
the Metro Wastewater Reclamation District's Robert W. Hite treatment facility ("Metro Sewer,"
WDID 020070). Metro Sewer is located approximately 10.78 miles upstream of the site. As such an
irrigation season (April through October)transit loss of 5.39% (0.5% per mile) and a non-irrigation
season (November through March) transit loss of 2.7% (0.25% per mile) will be assessed on all
releases. These transit losses are subject to change by the Water Commissioner or Division Engineer.
A copy of the signed lease agreement dated November 24, 2020 is attached. The term of the lease
is for the period of November 1, 2020 through October 31, 2021 and is renewable for up to five
additional one-year extensions provided by written notification from Aurora. According to the
attached October 11, 2021 letter from Aurora (Aurora lease extension) a one year extension has
been granted for the period of November 1, 2021 through October 31, 2022. The proposed
replacement schedule is provided in Exhibit A of the revised delivery schedule provided with the
Aurora lease extension.
Long-term Depletions
The final reclamation plan for DRMS Mining Permit No. M-2001-085 once had been to create a water
storage reservoir through the installation of a slurry wall. The slurry wall was constructed but did
not receive its liner approval from DWR. Based on the Applicant's statements, the slurry wall leaked
in multiple locations and the pit filled completely with groundwater. This was not in accordance
with their DRMS permit reclamation requirements. Therefore, the Applicant obtained approval of
an amendment to the reclamation mining permit from DRMS to allow for backfilling of the pit.