PERMFILE134266

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 70 REFUSE PILE EXPANSION
• Media Type: D
• Archive: No

REFUSE PILE EXPANSION
1.0 INTRODUCTION
This report summarizes work performed for
i Mountain Coal Company (MCC) by Harding
Lawson Associates (HLA) to obtain a technical
revision to CDMG Permit C-80-007 to construct a
new refuse pile on approximately 20 acres
immediately east of the existing MCC Lower
Refuse Pile. In addition, the exhibit will be
periodically updated to reflect current conditions of
the RPE construction. The location of the Refuse
Pile Expansion (RPE) and the current Lower Refuse
Pile (LRP) is shown in Figure A-l. This new refuse
pile is required due to [he limited amount of refuse
volume left in the current LRP in conjunction with
the need for additional refuse storage space
projected for the next 10 years.
The RPE was designed under the regulations set
forth in the August I, 1995, revision of the
"Regulations of the Colorado Mined Land
Reclamation Board for Coal Mining" per "Rule 4:
Performance Standards" for coal mine waste.
The significant work that was needed for this
technical revision included the following:
~~
I. Conducting a field geotechnical and
geological investigation of the proposed
RPE site. This work included a detailed
geologic mapping of the site and a
subsurface investigation to obtain soil and
rock samples for strength and classification
testing and to develop accurate soil
stratigraphy and groundwater elevation of
the site for the slope stability analysis.
2. Development of four phases of the RPE to
maximize resources and available volume
for refuse.
3. Performance of a slope stability analysis of
[he embankment [o ensure the RPE meets
the stated performance standards.
4. Performance of a surface and groundwater
hydrology study to size sediment and clear
water ditches and to design a sediment
control pond at [he RPE site.
r
5. Determination of suitable locations for the
excavated topsoil and subsoil.
6. Design of the haul road for access to the
RPE.
Each of these topics is discussed in detail in the
following sections.
2.0 DESCRIPTION OF PILE
CONFIGURATION AND PHASING
2.t Phasing
The RPE site is located approximately 1,000 feet
east of the existing LRP and east of Sylvester Gulch.
The pre-existing topography is depicted in Figures
B-I and B-2.
Construction of the RPE has been divided into four
phases. Phase I involves construction of runoff
controls, sediment pond, soil stripping, liner
installation, and some coal refuse placement.
Phases 2 through 4 involve placement of the
majority of coal refuse. The design goals were to
achieve maximum refuse storage, utilize existing
resources, and conform with existing topography.
2.1.1 Phase One -Site Development
Site preparation will occur during Phase 1 and
includes construction of a sediment pond, runoff
controls, subsoil cut, and liner installation. Four
sub-phases, 1-A through 1-D have been established
to minimize exposure of the cu[ slope during the
construction of the RPE. The sub-phases require
sequential liner installation and placement of refuse
as the subsoil cu[ is advanced southward. Figures
B-3 through B-14 illustrate sub-phases I-A through
I-D and delineate area disturbances involving
vegetation, topsoil, and subsoil stripping. Table I
gives the disturbed area quantities and estimated
volumes of removed soil and placed refuse. The
majority of Phase 1 Construction was completed
during 1997.
Topsoil was placed north of Highway 133, directly
opposite from the main mine entrance, known as the
North Soil Storage Area (NSSA). Subsoil from
Phase 1 and 2 were used for the development of rite
Harding Lawson Associates 1