2008-10-07_PERMIT FILE - C1981047 ‎(4)‎

• Permit No: C1981047
• IBM Index Class Name: Permit File
• Doc Date: 10/7/2008
• Section_Exhibit Name: Section 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: No

• level in the coal waste material. P-6 is 12.2 feet deep with a
bentonite seal at 2 feet on up to the surface. It is designed to
measure the water level in the cover material. The piezometers are
close enough together so it can be determined if the water level in
the cover material and the coal waste material are independent of
each other.
The water level in P-5 averaged 18.6 feet deep during 1992. At the
end of the year the water level in P-5 was 9.6 feet deep measured
from the bottom of the hole, (28.2 - 18.6).
The water level in P-6 decreased to 10.2 feet during 1992. At the
end of the year the water level in P-6 was 2 feet deep measured
from the bottom of the hole, (12.2 - 10.2).
The respective water levels in P-5 and P-6 indicate there is no
relationship between the water level in the cover material and the
water level in the waste material. The water level in P-5
indicates there is water in the coal waste material.
A network of gravel underdrains were installed under the coal waste
as it was being placed. These underdrains surface in three
locations which are referred to as the north, middle and south
underdrains. The middle underdrain has had measurable discharge
only once since its completion. Both the north and south
underdrains have discharged water during each year since their
• installation with the south underdrain discharging the largest
volume. The fact that they are both still discharging water is an
indication that the underdrain system continues to function
properly.
1988 6 1989 REPAIRS
The 1988 S 1989 slumps were believed to have occurred because the
cover material became saturated during the spring melt. The
saturated cover material, which became unstable on the slope, slid
down the slope until some of the moisture in the material was freed
and the effective slope was reduced enough for the cover material
to become stable. The slumps could be described as a scarp and a
bulge.
To repair the slump, the prior operator decided to install french
drains across the slump areas. It was anticipated that the french
drains would stop the cover material from becoming completely
saturated. The french drains were installed at the top of the
slump area, another across the center of the area and one across
the lower portion of the area. The french drains were installed
approximately at the interface between the cover material and the
coal waste material. The drains were constructed of four inch
slotted drain pipe wrapped in a geotextile fabric. The slump areas
were regraded to blend in with the surrounding slope.
n
LJ
113vi (Rev. 06-25-93)