30 CFR § 75.336 Sampling and monitoring requirements.
(a) A certified person as defined in § 75.100 shall monitor
atmospheres of sealed areas. Sealed areas shall be monitored, whether
ingassing or outgassing, for methane and oxygen concentrations and the
direction of leakage.
(1) Each sampling pipe and approved sampling location shall be
sampled at least every 24 hours.
(i) Atmospheres with seals of 120 psi or greater shall be sampled
until the design strength is reached for every seal used to seal the
area.
(ii) Atmospheres with seals less than 120 psi constructed before
October 20, 2008 shall be monitored for methane and oxygen
concentrations and maintained inert. The operator may request that the
District Manager approve different sampling locations and frequencies
in the ventilation plan, provided at least one sample is taken at each
set of seals at least every 7 days.
(iii) Atmospheres with seals less than 120 psi constructed after
October 20, 2008 shall be monitored for methane and oxygen
concentrations and maintained inert. The operator may request that the
District Manager approve different sampling locations and frequencies
in the ventilation plan after a minimum of 14 days and after the seal
design strength is reached, provided at least one sample is taken at
each set of seals at least every 7 days.
(2) The mine operator shall evaluate the atmosphere in the sealed
area to determine whether sampling through the sampling pipes in seals
and approved locations provides appropriate sampling locations of the
sealed area. The mine operator shall make the evaluation immediately
after the minimum 14-day required sampling, if the mine ventilation
system is reconfigured, if changes occur that adversely affect the
sealed area, or if the District Manager requests an evaluation. When
the results of the evaluations indicate the need for additional
sampling locations, the mine operator shall provide the additional
locations and have them approved in the ventilation plan. The District
Manager may require additional sampling locations and frequencies in
the ventilation plan.
(3) Mine operators with an approved ventilation plan addressing
spontaneous combustion pursuant to § 75.334(f) shall sample the
sealed atmosphere in accordance with the ventilation plan.
(4) The District Manager may approve in the ventilation plan the
use of a continuous monitoring system in lieu of monitoring provisions
in this section.
(b)(1) Except as provided in § 75.336(d), the atmosphere in the
sealed area is considered inert when the oxygen concentration is less
than 10.0 percent or the methane concentration is less than 3.0 percent
or greater than 20.0 percent.
(2) Immediate action shall be taken by the mine operator to restore
an inert sealed atmosphere behind seals with strengths less than 120
psi. Until the atmosphere in the sealed area is restored to an inert
condition, the sealed atmosphere shall be monitored at each sampling
pipe and approved location at least once every 24 hours.
(c) Except as provided in § 75.336(d), when a sample is taken
from the sealed atmosphere with seals of less than 120 psi and the
sample indicates that the oxygen concentration is 10 percent or greater
and methane is between 4.5 percent and 17 percent, the mine operator
shall immediately take an additional sample and then immediately notify
the District Manager.
When the additional sample indicates that the
oxygen concentration is 10 percent or greater and methane is between
4.5 percent and 17 percent, persons shall be withdrawn from the
affected area which is the entire mine or other affected area
identified by the operator and approved by the District Manager in the
ventilation plan, except those persons referred to in § 104(c) of
the Act. The operator may identify areas in the ventilation plan to be
approved by the District Manager where persons may be exempted from
withdrawal. The operator's request shall address the location of seals
in relation to: Areas where persons work and travel in the mine;
escapeways and potential for damage to the escapeways; and ventilation
systems and controls in areas where persons work or travel and where
ventilation is used for escapeways. The operator's request shall also
address the gas concentration of other sampling locations in the sealed
area and other required information. Before miners reenter the mine,
the mine operator shall have a ventilation plan revision approved by
the District Manager specifying the actions to be taken.
(d) In sealed areas with a demonstrated history of carbon dioxide
or sealed areas where inert gases have been injected, the operator may
request that the District Manager approve in the ventilation plan an
alternative method to determine if the sealed atmosphere is inert and
when miners have to be withdrawn. The mine operator shall address in
the ventilation plan the specific levels of methane, carbon dioxide,
nitrogen and oxygen; the sampling methods and equipment used; and the
methods to evaluate these concentrations underground at the seal.
(e) Recordkeeping. (1) The certified person shall promptly record
each sampling result including the location of the sampling points,
whether ingassing or outgassing, and oxygen and methane concentrations.
The results of oxygen and methane samples shall be recorded as the
percentage of oxygen and methane measured by the certified person and
any hazardous condition found in accordance with § 75.363.
(2) The mine operator shall retain sampling records at the mine for
at least one year from the date of the sampling.
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