HYDRO30917

• Permit No: M2002120
• IBM Index Class Name: Hydrology
• Doc Date: 6/5/2007
• Doc Name: Substitute Water Supply Plan
• From: OSE
• To: Leaf Engineering, Inc.
• Media Type: D
• Archive: No

Mr. Forrest Leaf
May 30, 2007
Page 2
Depletions
Currently 10.72 acres of ground water surface is exposed at the Bernhardt pit.
Consumptive use from the operation of this site consists of 11.77 acre-feet of water lost in
product (4% moisture of 400,000 tons of raw material), 3.31 acre-feet for on-site dust control,
11.51 acre-feet used in the production of 75,000 tons of concrete and 30.89 acre-feet of
evaporation from the 10.72 acres of lake surface exposed after December 31, 1980. The total
consumption at this site from mining operations is 57.48 acre-feet.
The evaporation calculation has been accepted for this plan period, however any SWSP
renewal request must demonstrate that the evaporation calculation is accurate for the specific
location of the Bernhardt pit.
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 Pond 2, shown on attached Figure 1,
for recharge back to the Big Thompson River. In September 2004, pumping of the dewatering
water into Pond 2 ceased. All water pumped from the trenches since September 2004 has
been pumped from within the slurry wall and used for the purposes described in this plan.
Based on the analysis 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, water lost in mined product and dust suppression were
lagged to the stream using a Glover analysis and assuming a distance to the stream of 1,015 feet,
distance to the impermeable boundary of 2,976 feet, transmissivity of 100,000 gal/day/ft and
specific yield of 0.2. The depletions from well no. 60729-F (concrete production) were also lagged
to the stream using a Glover analysis and assuming a distance to the stream of 1,510 feet,
distance to the impermeable boundary of 2,587 feet, transmissivity of 100,000 gpd/ft and specific
yield of 0.2.
Replacements
The proposed source of replacement for the Bernhardt pit is leased excess
augmentation credits (43.01 acre-feet) available under the Town of Milliken ("Milliken")
substitute water supply plan ("SWSP") approve pursuant to C.R.S. 37-92-308(4) on March 12,
2007. The court case associated with the Milliken SWSP is Division 1 Water court case no.
02CW339. The excess credits from Milliken accrue to the Big Thompson River in the same
location that the lagged depletions from the Bernhardt Pit impacts the river, therefore, no river
conveyance losses will be assessed.
The plan estimates that in the event that the operator were to cease mining and
dewatering at the site there would be 6.87 acres of exposed water surface located outside of
the slurry wall. To provide the security of a permanent, renewable source of replacement
water, 2 shares of Kern Reservoir (a.k.a Windsor Lake) are hereby dedicated to this plan and
made appurtenant to the tract of land where the gravel pit is located, until a permanent
augmentation plan for the gravel pit has been adjudicated or all consumptive use at the site has
ceased and all lagged depletions have been replaced. The depletions resulting from
evaporation off of the 6.87 acre pond are estimated to be 19.8 acre-feet. According to the
analysis provided in the plan, the 2 shares of Kern Reservoir have a historical consumptive use
of 22.69 acre-feet, therefore, the shares are found to be adequate. A copy of this approval