1987-12-01_PERMIT FILE - C1981017 ‎(194)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Doc Name: Subsidence Study by DR. Bruce Collins
• Section_Exhibit Name: Chapter IV Appendix IV-F-4
• Media Type: D
• Archive: No

BRUCE A. COLLINS, PH.D.
CONSULTING GEOLOGIST
1398 4060 ROAD
PAONIA COLORADO 81428
[phone]
MID-CONTINENT RESOURCES , INC.
REQUEST TO SUSPEND SUBSIDENCE MONITORING PROGRAM
On January 26 , 1981, Mid-Continent Resources, Inc. (here-
inafter referred to as MCR) submitted a Mining and Reclam-
ation Plan for its Coal Basin operations to the Colorado
Mined Land Reclamation Division (hereinafter referred to
as CYLRD) for review and approval . In response to the
recuirements of Rule 2 . 05 . 6 , Subsidence Survey, Subsidence
Monitoring and Subsidence Control Plan, MCR basically
stated that, because of the great overburden depths present
over most of the permit area and the absence of structures
or renewable resource lands, there was little likelihood
of significant subsidence taking place, and if it did no
darace would occur. CMLR.D, in its review process, rejected
this argument, and after several additional submissions
and revisions, an acceptable subsidence survey and monitor-
ing plan was approved, along with the rest of the Mining
and Reclamation Plan, effective May 31 , 1983 .
The subsidence section of the permit application as revised
and approved (Vol . 7 , Chapter IV, pages 23-34) , contains
the following salient points :
1. Renewable resource lands. These consist of limited
grazing areas for livestock and wildlife and possible
aquifer recharge areas. The minimal value of timber in the
area is supported by correspondence with the U.S . Forest
Service dated 9/5/80, 9/16/80 , and 10/14/80. There are no
known threatened or endangered species in the area, and it
is too high to provide winter range for big game animals
(USFS , 9/16/80) . Known aquifers in the area are below the
Rollins Sandstone and will not be affected by subsidence.
All of the known sandstones in the coal-bearing sequence,
including the Rollins which forms its base , are tightly
cemented bya mixture of calcite and silica, and commonly
have a clay matrix. While there are no hard numbers avail-
able, experience in nearly 30 years of mining indicates that
porosity, permiability and transmissivity of these units are
all low. Even on the lower slopes, at the extreme margins
of the permit area on the western side of the basin, bedrock
in the stream valleys draining the area is shallow, and in
addition only the lowermost reaches of Henderson, Coal and
Spring Creeks within the permit boundaries are shown by the
U.S . Geological Survey to be perennial streams (Placita and
Elk Knob 7 . 5 ' quadrangle maps) . It is therefore unlikely
that recharge to alluvial materials in these valleys within
the permit area is significant.