2014-06-30_HYDROLOGY - M2002120

• Permit No: M2002120
• IBM Index Class Name: Hydrology
• Doc Date: 6/30/2014
• Doc Name: SWSP
• From: DWR
• To: Civil Resources, LLC
• Permit Index Doc Type: Hydrology Report
• Email Name: ECS
• Media Type: D
• Archive: No

Bernhardt Pit SWSP Page 2 of 5
June 30, 2014
approved pursuant to S 37-90-137(11), C.R.S. will be accepted for this plan period; however, in
the future the Applicant will need to either amend the DRMS permit boundary to include the site
of the concrete batching well and concrete batching plant or obtain a SWSP for the well pursuant
to S 37-92-308, C.R.S. or a court approved augmentation plan.
Depletions
Currently 6.52 acres of ground water surface is exposed at the Bernhardt Pit within the three
settling ponds and dewatering trenches (See Figure 1). Consumptive use of ground water from the
Barnhardt Pit consists of 3.33 acre-feet for on-site dust control, and 18.78 acre-feet of evaporation
from the 6.52 acres of exposed ground water. Evaporative depletions were calculated using a gross '
annual evaporation of 43.86 inches, with a credit of 9.29 inches for effective precipitation (based on
an average annual precipitation of 13.27 inches for the Longmont weather station). There is no
aggregate production proposed at the site for this plan period. Consumptive use of ground water
from the concrete batching well (permit no. 60729-F) will consist of 1.23 acre-feet used in the
production of 10,000 cubic yards of concrete (assumes 40 gallons of water per cubic yard of
concrete). The total consumptive use at this site during this plan period is 23.34 acre-feet (See
Table 1). Depletions from mining operations at the Bernhardt site will impact the Big Thompson
River upstream of the Evanstown Ditch (WDID 0400517).
Dewatering at the site commenced in October 2003 at a rate of 750 gallons per minute. In
2004 dewatering decreased to 350 gallons per minute. All water pumped in 2003 and 2004 for
dewatering purposes was pumped from trenches into an on-site pond for recharge back to the Big
Thompson River. In September 2004, pumping of the dewatering water into the pond ceased. All
water pumped from the trenches since September 2004 has been pumped from within the slurry watt
and used for the purposes described in this plan. Based on the analysis previously performed by the
Applicant there are no depletions from past dewatering operations that will accrue to the river
during this plan period.
The depletions from evaporation and dust suppression were lagged to the stream using a Glover
analysis assuming a distance (X) from the centroid of the exposed ground water surface to the stream of
715 feet, a distance (W) to the impermeable boundary of 2,976 feet, a transmissivity (T) of 100,000
gal/day/ft, and a specific yield (S) of 0.2. The depletions from the concrete batching well (permit no.
60729-F) were lagged to the stream using a Glover analysis assuming a distance (X) from the well to the
stream of 1,510 feet, a distance (W) to the impermeable boundary of 2,587 feet, a transmissivity (T) of
100,000 gpd/ft, and a specific yield (S) of 0.2.
The total tagged depletions that are to be replaced in 2014 are 23.26 acre-feet (See Tables 2a,
2b, and 3).
Replacements
The proposed source of replacement for the Bernhardt pit is a lease of 19.08 acre-feet of
excess augmentation credits available to Central Colorado Water Conservancy District ("Central")
(WDID 0203334). Please note that the lease amount is for less than the calculated depletions due to
free river conditions in January, February, March, and part of April 2014, during which no
replacements were required to be made. The excess credits accrue to the Big Thompson River in the
same location that the tagged depletions from the Bernhardt Pit impact the river, therefore, no river
conveyance losses will be assessed. A copy of the Lease Agreement with Central was submitted to
this office on May 16, 2014, and is attached to this letter. A monthly breakdown of depletions and
replacements is shown in the attached Table No. 4.