REV97049

• Permit No: C1982057
• IBM Index Class Name: Revision
• Doc Name: TAB 16 PROTECTION OF HYDROLOGIC BALANCE
• Type & Sequence: PR2
• Media Type: D
• Archive: No

Average Annual Water Depletion Estimate
Evaporation from sediment ponds and haul road watering will be the primary causes of surface water
depletion in the II-W South area. Seneca II-W has three 131 existing ponds and is proposing to
construct three 131 additional ponds over the life of II-W South operation. The annual net lake
evaporation for Hayden, Colorado is 26.46 inches.

Total maximum evaporation from the three existing ponds has been calculated at 13.2 acre-feet
annually, while the proposed ponds would result in the loss of additional 6.0 acre-feet annually. This
estimate assumes that all ponds are full to the level of the principal spillway at all times (i.e. worst
case scenario).
Based on eight 181 years of records maintained by the State Engineers Office and SCC, the annual
usage of water to suppress dust on the haul roads has averaged 11 .4 acre-feet per year. This results
in a total annual usage of 30.6 acre-feet of surface water per year and is approximately 30 percent of
the Windy Gap trigger level of 100 acre-feet annually.
Overall, this would be a minimal indirect depletion occurring over the life of the operation. See Tab
16, Attachment 16-A, "Water Rights Investigation and Plan for Augmentation" for further details.
AVERAGE ANNUAL WATER DEPLETION ESTIMATE
Facili Acres Acre-Feet
Pond 005 lexistin 1 1.4 3.1
Pond 006 lexistin 1 2.8 6.2
Pond 009 )existing) 1 .8 4.0
Pond 015 (proposed) 0.7 1.5
Pond 016 (ro osed) 1.1 2.4
Pond 017 1 ro osed) 0.9 2.0
Haul Road Waterin 11.4
Total 8.7 30.6
Note: Surface acres of the ponds assume that water level is at principal spillway elevation.
Water usa eon the haul roads derived from 8- ear avers a 11 991-1 9981.
In general, [he hydrologic characteristics of reclaimed mined lands will result in lower spring run-off
volumes but higher summer and fall flow base volumes. Water depletions to the Yampa River from the
mining activities at II-W South will be minimal. SCC's current plan for augmentation includes the
availability of 37.4 acre-feet of water from the J.C. Temple Reservoir No.1 and up to 50 acre-feet of
water from the Stagecoach Reservoir to offset any potential depletions to the Yampa River.
The table above represents the only sources of water depletion at the Seneca II-W Mine. There are no
water depletions due to pit water evaporation, conveyor sprays, coal processing, bath house
consumption or domestic water use.
1 Revised 8/27/99