HYDRO29226

• Permit No: C1980001
• IBM Index Class Name: Hydrology
• Doc Date: 10/5/2006
• Doc Name: Groundwater Points of Compliance Determination
• From: DRMS
• To: Pittsburg & Midway Coal Mining Co
• Permit Index Doc Type: Correspondence
• Media Type: D
• Archive: No

Page 3
undisturbed bedrock was left by a setback of the mine pits to the west from the ridgeline. Thus
there was no extraction of coal or overburden in the Oak Creek drainage. Support facilities of a
conveyor off the ridgeline, east, to a coal railcar loading facility, and offices were located at the
base of the steep slopes in the Oak Creek valley.10
Oak Creek, a perennial stream, flows to the north, contiguous to the southern part of the east
permit boundary for approximately 7,000 feet, parallel (approximately 1000 feet from) to Oak
Creek for another 3,000 feet, and parallel to asouth-flowing, ephemeral, tributary to Oak Creek
for another 5000 feet. ~ ~ No portion of this section of Oak Creek, or the tributary, was considered
as an alluvial valley floor.12
Trout Creek, a perennial stream, flows to the north along the west edge, and base of the
topographic slope, of the permit area. This drainage has developed a wide (2000-foot) valley that
includes an alluvial valley floor. Numerous terraces of alluvial material have developed, the
lower (modern flood plain) being in hydrologically connected to Trout Creek.13
A stratum above the Wadge Coal was intercepted by the incised valley of Trout Creek, but the
Wadge Coal extends, in some azeas, under Trout Creek to the west.14 A section of strata was left
in place between mined areas and the alluvial valley floor of Trout Creek.15 (However, they may
have been a breach of this barrier on the south end of mining.)16 There were no surface
disturbances, other than the setting of monitoring wells and a weir, on the alluvial valley floor.
The Wadge coal seam outcrops near the center of the permit area in the Trout Creek valley.
Alluvial monitoring well TR-1.5 is above the Wadge coal seam, well TR-3 below, and TR-4
below TR-3.
Bedrock Groundwater
Spoil ground water has collected in former (backfilled) pits of the mining operation, and has
manifested itself in springs and seeps at the crest of the former pit low walls.~~
Mining was not anticipated to affect the Trout Creek Sandstone. ~s. No piezometric surface map
was found in the PAP for the Trout Creek Sandstone. The transmissivity of materials between
the Wadge Coal and the Trout Creek Sandstone is very low (2.7 to 10.4 ftz /day)19.
'0 PAP Exhibit 3.6-1
" PAP Exhibit 3.7-1
12 PAP page 4.6-61 c
" PAP page 4.5-62
14 PAP Exhibits 2.2-3 and 2.2-4
15 PAP, Section 3.3, Figure 2
16 PAP, page 2.5-95
'~ 2004 ARR, Exhibit I
18 PAP page 2.5-47
19 PAP page 2.5-50 and Table 2.5-13