2009-09-21_PERMIT FILE - C1981010A ‎(45)‎

• Permit No: C1981010A
• IBM Index Class Name: Permit File
• Doc Date: 9/21/2009
• Doc Name: pages 2-523a to 2-576u
• Section_Exhibit Name: 2.7 Hydrology Part 4
• Media Type: D
• Archive: Yes

• 2.7.5.4 Ground Water Use
Prior to submittal of Trapper's initial permit application, an inventory of water wells within one
mile of the proposed permit area was conducted. Design information for these wells is provided
in Tables 2.7-22b and 2.7-22c. This inventory indicates a number of water wells are present in
the area. Map M-31 shows the locations and permit numbers of wells. Only wells completed in
the Third White Sandstone of the Upper Williams Fork formation and situated south of the Big
Bottom Syncl ine are believed to have any potential to be affected by the mine. Wells 93848 and
80998 fit this criteria (refer to Map M-31). In addition, two springs (Lux Springs) with flows of 0.4
and 0.7 cfs are present in the southeast quarter of Section 29, T6N, R91 W.
Well 93848 will likely not be impacted by mining operations that occurred in the Browning and
Colt pits. The strike and dip of the coal seam and overlying strata in the vicinity of this well
make contact with the backfill aquifers in these pits unlikely. Well 80998 appears to have at
least some minor potential to be influenced by mining operations in the Flume drainage. This
well is approximately 3,500 feet from the edge of the Trapper permit boundary. Water levels
and yields from this well are not expected to be measurably affected by mining upgradient of this
Third White sandstone well. Mining upgradient in the Third White Sandstone has been shown
not to affect water levels downgradient of the mining zone due to the generally quick recovery of
water levels at the northern boundary of the mine pits. Higher permeability backfill materials
drain water to the northern edge of the pits and allow the back-fill aquifers in these areas to
recover quickly. No water-level effects were observed in the Third White Sandstone well, P8,
approximately 1,000 feet downgradient of mined areas. Monitoring of Third White Sandstone
wells GC-2 and GP-9 will define whether any potential water level or water yield impacts can be
expected further downgradient in the vicinity of well 80998. No impacts are evident to date.
• Backf ill aquifers at Trapper can be characterized by higher major constituent concentrations such
as TDS in some areas. These higher TDS concentrations might persist for an extended period
of time. The higher concentrations from the backfill aquifers may recharge the Third White
Sandstone and, therefore, eventually increase major constituent levels in this aquifer as well.
Wells completed in this aquifer could potentially be affected. The increase in TDS concentration
might be offset somewhat by the influence of higher quality underburden inflows. Continued
monitoring at wells GC-2 and GP-9 will better define the potential for water quality influences at
Third White Sandstone well 80998. No impacts are evident to date.
Well CA-2259 provides water to the two MacNamara Ditches (Map M-31). The well was
adjudicated for irrigation, stock water and domestic water use.
Periodically, Trapper reviews the filings for Water Division 6, District 44, and updates Map M-31.
Revised Map M-31 illustrates all filings within one mile .of Trapper's permit boundary. The
aquifers to which the adjudicated wells are completed to are as follows:
Aquifer
Adiudicated Permit Number
First White Sandstone W-1406-78
Second White Sandstone 8577-5A.
2-524 Revision
Approves! 9?=/ o?.__