INSPEC12735

• Permit No: C1981033
• IBM Index Class Name: Inspection
• Doc Name: Inspection Report
• Inspection Date: 7/20/2004
• Media Type: D
• Archive: No

exhaust fan portal site.
During the inspection, a Suunto optical reading clinometer was used to measure slope gradients in two
locations. The first measurement location was on the backfilled slope at the easternmost Bear No. 3
Mine portal, the exhaust fan portal. The slope gradient was 26 degrees down, or 2.OSH:1 V. The second
measurement was taken in the middle of the backfilled upper bench azea. The slope gradient there
measured 24 degrees down, or 2.25H:1 V. The measured slope gradients compared favorably with the
approved post mining cross section slope gradients depicted on Map 12 of the permit application.
Rule 4.14.2(1)(b) requires that backfilled and graded slopes achieve a minimum factor of safety of 1.3.
Please provide a demonstration that this performance requirement has been met for the reclaimed
slopes at the Bear No. 3 Mine. This matter is important due to the ongoing slides throughout the
adjacent areas, and given the history of slides within the disturbed azeas.
The operator constructed a riprapped drainage channel down the middle of the backfilled portal area
slope in order to route runoff water from the undisturbed azea above the mine site through the
reclaimed hill slope area. The riprapped channel appeazed to be functional. No erosional features were
observed in the channel or at the channel outlet.
Downgradient from the reclaimed exhaust fan site was a gully that was an erosional remnant from an
earlier slide. In April 1993, a section of the portal access road, centered at the exhaust fan site, slid
down about 7 feet. The repair of the road section and the slope below the road, as well as the
installation of French drains, was completed in 1993 and monitored for several years thereafter. The
stability monitoring demonstrated that the area was stable at that time. The erosional gully observed
during the inspection was well vegetated and appeazed to be stable. The French drain plastic pipe was
evident.
The inspection then proceeded to the portal sealing and backfilling work. As reported by the operator,
the portals were sealed with foam and further supported by timbers. The seals were installed where the
rock was most secure. A four inch diameter drainage pipe was installed through each of the seals and,
then, backfilled with noncombustible material. The outlet ends of the portal seal drainage pipes were
placed in river rock and covered with filter fabric. According to the operator, the portal sealing and
backfilling operations were approved by the Mine Safety and Health Administration. The portal seals
were not visible during the bond release inspection due to the backfilling work. However, the sealing
of the portals and installation of the drainage pipes were noted in the Division's inspection reports of
February 19, 1997 and March 18, 1997.
There was an exposed vertical section of concrete headwall at the easternmost backfilled Bear No. 3
Mine portal, the exhaust fan portal. The exposed headwall section was about 1 foot in height and about
3 feet in width. Another loose section of concrete headwall was lying on the ground within 5 feet and
uphill of the vertical headwall section. The headwall appears to have been part of the buttress wall for
the exhaust fan site. As stated in the April 16, 1982 report "Stability Analysis of Portal and Access
Road Areas - Beaz Mine No. 3" in the Beaz No. 3 Mine permit application, retaining walls were to
remain in place after reclamation in order to improve slope stability conditions. With the limited
amount of available material for backfill, it appears to the Division that this exposed headwall is not a
problem. However, there was a small hole in the exhaust fan portal backfilled material, on the down
gradient side of some rocks. There were no signs of the hole being an animal burrow. The hole may be
a sign of backfill instability and may indicate communication with the underlying workings. This hole
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