APPCOR12591

• Permit No: C1980007
• IBM Index Class Name: Application Correspondence
• Doc Name: UNSUITABILITY ANALYSIS AND REPORT
• Media Type: D
• Archive: No

-11-
`. 817.121 Subsidence Control
38. The regulatory authority directs ARCO to complete the installation of the
subsidence monitoring network prior to the initiation of extraction of
coal within the panel designated in Exhibit 3. 4.S.A (of [he mine plan)
for subsidence monitoring. The monitoring network is designed [o monitor
the fifth panel from the entrance of the main portal, west frov. the main,
within section 16. This monitoring network shall consist of substantial '~
monuments designed to resist frost-heave, fire, and the actions of cattle
and wildlife. ARCO shall submit a monument design to the regulatory
authority for approval and installation shall not occur prior to approval
of the monument design.
39. The regulatory authority directs ARCO to submit reports of its subsidence
monitoring program on a semi-annual basis, commencing one month after the
installation and initial surveying of the subsidence monuments. Further,
ARCO is directed to submit a proposed subsidence monitoring report format
to the regulatory authority for approval. This report format should
recognize the importance of continual update of subsidence data
interpretation, monitoring of ground water levels and spring flows,
monitoring of mine inflow, and subsurface ground conditions which could
be correlated to subsidence prediction. This report format shall be
approved by the regulatory authority prior to the commencement of
extraction of coal within the panel designed for subsidence monitoring.
~ 40. When the applicant submits a permit application to undermine the Dry Fort:
of tiinnesota Creek, the subsidence protection plan should be based upon
monitoring information collected during the earlier phases of mining.
41. The regulatory authority directs ARCO to complete a detailed analysis of
the potential effects of slope stability upon the stability of the
landslide deposit located about the town of Somerset, referenced on page
30 of Exhibit 3.4. 8A of the revised permit application. ARCO shall
install and monitor an appropriate set of monuments on the landslide
deposit, in order to observe potential displacement of the land form. A
detailed analysis shall be completed, and the results submitted to the
regulatory authority for review. No pillar recovery shall occur within
the affected panels prior to receipt of regulatory authority approval.
If subsidence monitoring experience or the detailed stability analysis
indicate that secondary extraction would adversely affect [he stability
of the landslide deposit above the town of Somerset, then AR CO shall
limit extraction of these panels to 50 percent. The affected panels are
the three northernmost panels to the west of the mains within Section 17.
42. The regulatory authority directs ARCO Coal, as a portion of its
subsequent permit applications for the 11t. Gunnison No. 1 Ptine, to submit
~a revised subsidence evaluation. The subsidence evaluation for the next
permit period shall incorporate the results of subsidence monitoring and
the landslide stability studies stipulated above in designating refined