REP50071

• Permit No: C1981044
• IBM Index Class Name: Report
• Doc Name: REGULATION OF COAL MINE SUBSIDENCE IN COLO
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

The~Colorado subsidence regulations provide the
following guidance for the completion of the
:determination of whether the worst-possible
consequences of subsidence could cause material
iamage or diminution of reasonably foreseeable use
~r value. Rule 2.06.6(6)(e)(ti) states "Material
subsidence damage means, with respect to
structures, changes which make it technologically
or economically infeasible to promptly restore the
affected structures to the condition they would be
in if subsidence had not occurred." That same
rule further states "Material subsidence damage
means, with respect to renewable resource lands,
changes which disrupt an aquifer, or a recharge
area to an aquifer, which serves as a beneficial
use of water or changes which make it
technologically or economically infeasible to
restore the productivity of the affected renewable
resource lands, expressed in terms of food, fiber
or forage, to the level it would be if subsidence
had not occurred."
That same regulation also states that a
determination of diminution of reasonably
foreseeable use or value of structures or
renewable resource lands shall consider the
capability of those structures and lands, before
and after subsidence occurrence, to support the
pre-mining an~i post-mining land uses of the permit
and adjacent area, giving consideration to factors
such as soil or foundation characteristics,
topography, vegetative cover, surface hydrology
and ground water hydrology.
If the applicant determines that the
«orst-possible consequences of subsidence would
not cause material damage or diminution of
reasonably foreseeable use, and the Division
concurs with that conclusion, the application must
include a subsidence monitoring program designed
to verify that conclusion. Of the twenty-seven
permit applications whose subsidence inventories
delineated structures or renewable resource lands
within their permit and adjacent areas, five
applicants demonstrated to the satisfaction of the
Division that the worst-possible subsidence
consequences would not result in material damage
or diminution of reasonably foreseeable use or
value (Table 2).
If the applicant determines that the
worst-possible subsidence consequences would cause
material damage or diminution of use or value, the
applicant has the option of either preparing a
subsidence survey, including a sophisticated
technical subsidence pre di rtion, or a subsidence
control plan.
Subsidence Surv
In contrast with the preceding application
procedures, a subsidence survey includes a
sophisticated state-of-the-art subsidence
prediction and a detailed description of the
rojected consequences of the predicted subsidence
yhenomena, in terms of material damage and
diminution of reasonably foreseeable use or
value. In completing a detailed prediction of
anticipated subsidence phenomena, the applicant is
~VJ
required to describe planned mining methods,
geologic properties which could influence
subsidence occurrence, local experience concerning
subsidence, predicted subsidence phenomena,
predicted angle of draw, and the areal extent of
anticipated subsidence. Having completed a
prediction of the anticipated subsidence
phenomena, the applicant is required to complete a
detailed description of material subsidence damage
and diminution of reasonable foreseeable use or
value of inventoried structures and renewable
resource lands which could result from the
predicted subsidence.
The applicant is required to apply
state-of-the-art predictive techniques in
analyzing the potential nature and impacts of
subsidence. Applicants have chosen a variety of
analytical techniques for the completion of their
required subsidence Surveys, as summarized in
Table 1. British National Coal Board (1975)
empirical projection techniques have proven to
predict greater subsidence magnitude, higher
strain levels and larger angles of draw than have
been observed in the western United States.
Correction techniques applied to the NCB
predictive techniques, developed by Abel and Lee
(1980) have enjoyed popularity among Colorado mine
operators. A number of operators have chosen to
apply more sophisticated mathematical techniques
of subsidence prediction.
Coal mining has been conducted in Colorado
since the mid-1800's. Several operators were
fortunate to have historic or modern underground
mine workings on or adjacent to their permit
areas. Observations of subsidence phenomena
related to these existing mine workings have
provided valuable empirical evidence for the
correlation of analytical predictive techniques.
If the applicant, having completed the required
subsidence survey, concludes that subsidence will
not cause material damage or diminution of
reasonably foreseeable use or value of the
inventoried structures and renewable resource
lands, and the Division concurs «ith that
conclusion, the application must include a
subsidence monitoring program to verify the
conclusion. If, on the other hand, the
application determines that material damage or
diminution of use could occur, the application
must include an acceptable subsidence control
plan, in order to insure the control or mitigation
of potential subsidence effects. As of May 1,
1986, twenty-one permit applications had included
subsidence surveys. Two of those surveys
determined that the proposed mine plans would
preclude material damage and diminution of
reasonably foreseeable use or value of structures
and renewable resource lands. The remaining
nineteen permit applications contained subsidence
control plans.
Subsidence Control Plan
The final component of the subsidence portion
of many underground coal mine permit applications
is a subsidence control plan. A subsidence