PERMFILE43400

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 9/6/2005
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: Yes

Site-specific investigations required for design and permitting of the new ventilation shaft included a
cultural resource survey of potential disturbance areas, soil and foundation characterization as the basis
for shaft pad and access road design, and completion of a wetland/AVF survey for the shaft pad and
access road. The cultural resource survey was conducted by Metcalf Archaeological Consultants, the
engineering soils chazacterization by Northwest Colorado Consultants, and the soils/wetland/AVF survey
by Habitat Management, as described in Section 2.04.
The perimeter of all areas affected by surface facilities will be clearly marked before the beginning of
surface disturbances. The proposed shaft pad surface area is approximately 280' squaze (1.8 acres), with a
total pad disturbance azea (includes cut and fill slopes) of 2.5 acres. The associated access road corridor is
approximately 7,100' long, with a finished top width of 24 feet (road corridor 35 feet wide, 5.7 acres).
See Exhibit 25T, 18 Right Ventilation Shaft Geotechnical Pavement Design, for details on the road, and
Map 24-CDl, a new road profile and cross-section. Approximately 4,400 feet of the access road crosses
upland azeas, with the remaining 2,700 feet crossing lowland azeas where road construction will involve
removal of any large vegetation and stripping and stockpiling of other vegetation, topsoil, and organic
materials.
Given an average topsoil depth of approximately 6 inches in the upland area and a total road disturbance
azea of approximately 5.7 acres, approximately 4,600 CY of topsoil will be salvaged from the road
corridor, and 2,000 CY from the 2.5 acre pad azea. Prior to initiating topsoil removal activities,
stream wetland buffer zones will be mazked with identifying signs to prevent surface disturbance within
buffer zone azeas. The topsoil from the road corridor was initially windrowed downslope beyond the
edge of the 35-foot road disturbance area, and topsoil from the pad azea was placed in a stockpile adjacent
to the shaft pad and within the 100-foot road corridor, for future reclamation use. As a result of concerns
related to protection of windrowed topsoil from erosion and contamination, a decision was made to
recover topsoil from the windrows and place it in stockpile. The topsoil salvage volumes are indicated on
Table 49A. Natural vegetative materials (mulch) incorporated into the topsoil, and seeding with the
topsoil stockpile stabilization seed mixture identified on page 2.05-121 will stabilize the windrowed and
stockpiled topsoil.
Following topsoil removal, required drainage and sediment control structures will be constructed or
installed. These structures include the upslope road drainage ditch, road crossings of smaller ephemeral
drainage channels; dischazge control structure (rock check dam) at the down-gradient limit of the shaft
pad, and a temporary diversion ditch around the up-gradient perimeter of the shaft pad. The drainage
from the shaft pad is addressed under a Small Area Exemption (SAE), as both the associated drainage
azea (4.3 acres) and the pad disturbance (2.5 acres, includes 0.2 acre ditch disturbance) are relatively
small, the pad will be gravel-surfaced, and the remainder of the drainage area is undisturbed and
vegetated. The access road follows variable topography, generally consisting of rolling terrain, and will
be grave]-surfaced, so access road drainage control requirements are minimal. Atypical road drainage
ditch design is provided in Figure 2 of Exhibit 8T, prepared by Water & Earth Technologies, Inc, April
2004. Six (6) culverts are required to remove the flow from the runoff ditches to limit runoff velocities in
the ditches to less than or equal to 3.75 feet per second (fps). This will assure that the ditches remain
stable with no channel scour or degradation during peak flow events. Breaks in the topsoil windrow will
allow runoff to drain. All drainage calculations and documentation are provided in Exhibit 8T, the SAE
demonstration is provided later in this section, and the drainage structures are shown on Map 24. The
SAE demonstration includes ditch sizing for the upland diversion ditch and road ditch.
Construction of the ventilation shaft access road will involve topsoil recovery and windrowing,
installation of required drainage structwes, scarification and re-compaction of surface materials, and
placement and compaction of approximately 8 inches of pit-run gravel and 3 inches of suitable road-base
material. The access road surface will be approximately 24 feet wide and will be graded and crowned to
MROS-194 2.05-45.4 07/2/05