GENERAL47948

• Permit No: C1981013
• IBM Index Class Name: General Documents
• Doc Date: 12/15/1982
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

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within the area being mined. In actuality, projecting an angle of draw of
30o from the boundary of the proposed development mining to the surface
overlying those development mains, only 17 of the 31 indicated structures
could potentially be affected by subsidence during the first five-year permit
period. Further, these l7 structures are divisible into several different
categories, for which different types of monitoring are appropriate.
Subsidence could potentially affect two San Isabel power company overhead
suspended powerlines (structures No. 1 and No. 7), the C&W railroad spur which
terminates at the Allen Mine (structure No. 2), a Mountain Bell buried
telephone cable (structure Na. 4), and three segments of Colorado Highway No.
12 (structure No. 6). (The preceding numbers in parentheses refer to
structures identified on Map 17 of the amended permit application.) Each of
these structures is amenable to visual monitoring, which the applicant
proposes to accomplish on a quarterly basis.
Subsidence could also potentially affect the Purgatoire River and its
associated alluvial valley floor and alluvial aquifer (structure No. 3) along
three separate reaches of the channel. The alluvial aquifer, designated as
renewable resource land within the application, is to be monitored through the
use of alluvial monitoring wells. The applicant does propose an alluvial
monitoring well program within the amended application. However, no alluvial
wells exist above the First North Mains, which are proposed by the applicant
to be physically monitored to observe the mechanical effects of subsidence.
It would be desirable to have an additional alluvial monitoring well installed
immediately above the centerline of the proposed First North Mains, preferably
in the immediate area of the proposed line of survey monuments: This
installation would allow verification of the immediate effects of undermining
upon the alluvial aquifer, through comparison of upslbpe and downslope
alluvial monitoring well water levels.
Subsidence could also potentially affect the Trinidad city water supply
pipeline (structure No. 5). CF&I has committed to immediate repair of the
Trinidad city water pipeline should damage occur;
Five barns are known to exist within the area of potential subsidence effects
projected during the first five-year permit period (structures 8, 15, 26, 29
and 30). CF&I has committed to perfi orming apre-mining photographic survey of
these five structures. In addition, the applicant will visually inspect these
potentially affected structures on a quarterly basis.
CF&I's subsidence control plan indicates that five adobe houses exist within
the area of potential subsidence effects during the first five-year permit
term (structures No. 14, 27, 28, 31 and 32). The monitoring requirements of
Rule 2.05.6(c)(i)(C) apply verbatim to these inhabitable structures; ... °The
orientation, location and elevation of each structure ... shad be
monitored." The applicant commits to monitoring of these five adobe houses.
However, the applicant indicates that these surveys will be performed on an
annual basis. Rule 2.05.6(6)(c)(i)(D) specifically requires performance of
the monitoring surveys on a quarterly basis. For this reason, it is necessary
to impose the following stipulation in order to comply with the Rule.