2013-01-15_HYDROLOGY - M2010071

• Permit No: M2010071
• IBM Index Class Name: HYDROLOGY
• Doc Date: 1/15/2013
• Doc Name: EXPANSION SUBSTITUTE WATER SUPPLY PLAN
• From: DWR
• To: PETER WAYLAND
• Email Name: MAC
• Media Type: D
• Archive: No

Mr. Wayland
Goose Haven #2 Expansion SWSP
January 9, 2013
273,333 tons to be mined in 2013 and 400,000 tons to be mined in 2014. The mined material
will be in a dewatered state and washed and therefore, pursuant to paragraph 13 of the General
Guidelines for Substitute Water Supply Plans for Sand and Gravel Pit (April 2, 2011), a 4%
moisture content by weight is charged as a groundwater diversion. This relates to a
groundwater Toss from mined product of 8.04 acre -feet in 2013 and 11.77 acre -feet in 2014.
The Alluvial Water Accounting System ( "AWAS ") model was used with the alluvial
aquifer boundary condition option to lag depletions to Boulder Creek. The following parameters
were used in the model: transmissivity (T) = 44,883 gallons per day per foot, distance (X) from
the centroid of the surface of the exposed ground water to the river = 3709 feet, distance (W)
from the aquifer boundary through the exposed ground water to the river channel = 4,400 feet,
and specific yield (SY) = 0.2. The location of the stream depletion is assumed to be
perpendicular to the river. The lagged depletions due to evaporation and mining operations
during the SWSP period are estimated to total 3.88 acre -feet for 2013 and 13.64 acre -feet for
2014.
The depletions to occur in this plan period are summarized below. The attached Tables
AI.5 & 6 show the monthly breakdown of these values.
Table A — Depletion Summary
2013
2014
Total
Evaporative
Loss
1.99
2.61
4.60
Mined
Product
Loss
8.04
11.77
19.81
Dust Control
Loss
3.75
Total
Consumptive
Use
13.78
3.75 18.13
7.50 31.91
Replacements
Page 2 of 5
Lagged
Depletions
3.88
13.64
17.52
Dewatering
Dewatering will occur and is projected to remain continuous throughout the duration of
this SWSP approval period. Water will be discharged into sediment ponds and ultimately
discharged into Boulder Creek via Lafayette's return flow canal. The return flow canal is a
concrete lined canal that discharges to Boulder Creek into the initial reach of the Boulder &
Weld County Ditch downstream of the diversion structure, but upstream of the ditch headgate
and overflow canal back to Boulder Creek. For dewatering analysis it is assumed that the
sediment ponds do not allow infiltration and that the dewatered water is returned to Boulder
Creek the same month the dewatering occurs. As long as dewatering remains continuous, the
net accretions should be sufficient to replace the lagged depletions. At least three years prior to
the planned cessation of dewatering, the operator must submit a dewatering analysis that
shows how post pumping depletions will be replaced. As this analysis requires knowledge of
the total volume dewatered, all dewatering activities must be metered with a totalizing flow
meter that is recorded and reported on the submitted monthly accounting.
Replacement water for depletions under this SWSP will come from fully consumable
water owned by Lafayette to be delivered to Boulder Creek from Lafayette's waste water
treatment plant ( "WWTP ", WDID 0602300) or through release from Lafayette's Goose Haven
Reservoir Complex (WDID 0603998). This WWTP discharges to Coal Creek, a tributary to
Boulder Creek. Intervening water rights between the site and the Coal Creek confluence are
the Boulder & Weld County Ditch (WDID 0600515), Howell Ditch (WDID 0600536), and the
Wittemyer Ponds (WDIDs 0606006 through 0606010). Should one of these rights call the