[Federal Register: April 18, 2008 (Volume 73, Number 76)] [Rules and Regulations] [Page 21181-21209] From the Federal Register Online via GPO Access [wais.access.gpo.gov] [DOCID:fr18ap08-12] [[Page 21181]] ----------------------------------------------------------------------- Part III Department of Labor ----------------------------------------------------------------------- Mine Safety and Health Administration ----------------------------------------------------------------------- 30 CFR Part 75 Sealing of Abandoned Areas; Final Rule [[Page 21182]] ----------------------------------------------------------------------- DEPARTMENT OF LABOR Mine Safety and Health Administration 30 CFR Part 75 RIN 1219-AB52 Sealing of Abandoned Areas AGENCY: Mine Safety and Health Administration (MSHA), Labor. ACTION: Final rule. ----------------------------------------------------------------------- SUMMARY: This final rule revises MSHA's Emergency Temporary Standard (ETS) and addresses sealing abandoned areas in underground coal mines. The final rule includes requirements for seal strength, design, construction, maintenance and repair of seals and monitoring and control of atmospheres behind seals in order to reduce the risk of seal failure and the risk of explosions in abandoned areas of underground coal mines. It also addresses the level of overpressure for new seals. EFFECTIVE DATE: This final rule is effective April 18, 2008. FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Blvd., Room 2350, Arlington, Virginia 22209-3939, silvey.patricia@dol.gov (e-mail), (202) 693-9440 (voice), or (202) 693-9441 (telefax). SUPPLEMENTARY INFORMATION: The outline of the final rule is as follows: I. Background II. Discussion of the Final Rule III. Section-by-Section Analysis IV. Executive Order 12866 A. Mine Sector Affected B. Benefits C. Compliance Costs V. Feasibility A. Technological Feasibility B. Economic Feasibility VI. Regulatory Flexibility Act and Small Business Regulatory Enforcement Fairness Act A. Definition of Small Mine B. Factual Basis for Certification VII. Paperwork Reduction Act of 1995 A. Summary B. Details VIII. Other Regulatory Considerations A. The Unfunded Mandates Reform Act of 1995 B. The Treasury and General Government Appropriations Act of 1999: Assessment of Federal Regulations and Policies on Families C. Executive Order 12630: Government Actions and Interference With Constitutionally Protected Property Rights D. Executive Order 12988: Civil Justice Reform E. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks F. Executive Order 13132: Federalism G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use I. Executive Order 13272: Proper Consideration of Small Entities in Agency Rulemaking IX. References I. Background In the Federal Coal Mine Health and Safety Act of 1969 (Coal Act), the predecessor to the existing Mine Act, Congress first recognized that mine operators must isolate abandoned areas of underground coal mines from active workings for the protection of miners' safety: In the case of mines opened on or after the operative date of this title, or in the case of areas developed on or after such date in mines opened prior to such date, the mining system shall be designed, in accordance with a plan and revisions thereof approved by the Secretary and adopted by the operator, so that, as each set of cross entries, room entries, or panel entries of the mine are abandoned, they can be isolated from active workings of the mine with explosion-proof bulkheads. Pub. Law 91-173 (Dec. 1969) Section 303(2)(3). In the conference report filed in the House, the statement of the managers on the part of the House stated, regarding the requirement that an abandoned area of a mine either be ventilated or sealed, that: [t]he determination of which method [(ventilated or sealed)] is appropriate and the safest at any mine is up to the Secretary or [her] inspector to make, after taking into consideration the conditions of the mine, particularly its history of methane and other explosive gases. The objective is that [s]he require the means that will provide the greatest degree of safety in each case. * * * When sealing is required, such sealing shall be made in an approved manner so as to isolate with explosion-proof bulkheads such areas from the active working of the mine. Under the conference substitute, paragraph (3) of section 303(z) provides that, in the case of mines opened on or after the operative date of this title, or in the case of areas developed on or after such date in mines opened prior to such date, the mining system shall be designed, in accordance with a plan and revisions thereof approved by the Secretary and adopted by the operator, so that, as each set of cross entries, room entries, or panel entries of the mine are abandoned, they can be isolated from active workings of the mine with explosion-proof bulkheads approved by the Secretary or his inspector. The managers expect the Secretary to take the lead in improving technology in this area of controlling methane accumulations in gob areas and to improve upon this important section 303(z). Conf. Rep. No. 91-761, 91st Cong. 1st Sess., 82 (Dec. 16, 1969) (statement of the managers on part of the House) (emphasis added). The Mine Act interim mandatory standards required seals to be ``made in an approved manner so as to isolate with explosion-proof bulkheads such areas from the active workings of the mine.'' 30 U.S.C.863(z)(2). On May 15, 1992, as part of a comprehensive revision of its standards for ventilation of underground coal mines, MSHA published standards for construction of seals in Sec. 75.335 of the ventilation standards (57 FR 20868). The standard required seals to be constructed of solid concrete blocks at least six inches by eight inches by sixteen inches, but allowed seals to be constructed using alternative methods and materials, provided, among other things, that the seal was capable of withstanding a horizontal static pressure of 20 psi. MSHA based this threshold on a U.S. Bureau of Mines 1971 report entitled ``Explosion-- Proof Bulkheads--Present Practices.'' A number of manufacturers developed materials, such as cementitious foams and glass-fiber material, which were tested and subsequently deemed suitable for use in alternative seals and marketed under various trade names. MSHA required the manufacturers to have full-scale seals be subjected to explosion testing at the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Experimental Mine (Lake Lynn). MSHA then intended for mine operators to construct seals as constructed and tested at Lake Lynn. On January 2, 2006, an explosion at the Sago Mine in Upshur County, West Virginia caused the death of twelve miners. Later that year, on May 20, 2006, an explosion at the Darby Mine No. 1 in Harlan County, Kentucky, caused the death of five miners. Common to both of these accidents was the failure of the seals in the mine. The failed seals in both mines were constructed with the same approved alternative material for a 20-psi seal. None of the failed seals were constructed in the same manner as they were constructed at Lake Lynn. Therefore, MSHA issued a moratorium on alternative methods and materials for construction of new seals (Program Information Bulletin (PIB) No. P06- 11, June 1, 2006, reissued on June 12, 2006 as PIB No. P06-12, reissued on June 21, 2006 as PIB No. PO6-14). [[Page 21183]] Following these underground coal mine disasters in 2006, Congress passed and the President signed the MINER Act. Section 10 of the MINER Act requires the Secretary of Labor to finalize mandatory health and safety standards relating to the sealing of abandoned areas in underground coal mines, and to increase the 20 psi standard. MSHA increased the strength of alternative seals to 50 psi and addressed a number of other issues related to the construction and the effectiveness of existing alternative and solid concrete block seals in Program Information Bulletin No. P06-16, ``Use of Alternative Seal Methods and Materials Pursuant to 30 CFR 75.335(a)(2),'' issued on July 19, 2006 (July 2006 PIB). On February 8, 2007, NIOSH issued a draft report, ``Explosion Pressure Design Criteria for New Seals in U.S. Coal Mines'' (2007 NIOSH Draft Report). The draft report states that ``mine seals and their related systems such as the monitoring, inertization and ventilation systems require the highest level of engineering and quality assurance. Successful implementation of the seal design criteria and recommendations in this report should reduce the risk of seal failure due to explosions in abandoned areas of underground coal mines.'' (2007 NIOSH Draft Report at 40). In the executive summary of the draft report, NIOSH made recommendations for formulating seal design criteria. On May 22, 2007, MSHA published an Emergency Temporary Standard; notice of public hearings; and notice of close of comment period (72 FR 28796). The comment period, scheduled to close on July 6, 2007, was extended to August 17, 2007 (72 FR 34609) and four public hearings were held. The hearings were held on July 10, 2007, in Morgantown, West Virginia; on July 12, 2007, in Lexington, Kentucky; on July 17, 2007, in Denver, Colorado; and on July 19, 2007, in Birmingham, Alabama. On August 14, 2007, MSHA extended the comment period to September 17, 2007, (72 FR 45358) to allow commenters additional time to review recently posted documents on MSHA's Web site and a recently published report from NIOSH entitled ``Explosion Pressure Design Criteria for New Seals in U.S. Coal Mines,'' NIOSH Publication No. 2007-144, July 2007, IC-9500 (2007 NIOSH Final Report). With one exception, the final version of this report was little changed from the draft version of this report that was referenced in the ETS. The final report includes a new section 3.3, Homogeneous Methane-Air Mixtures in Sealed-Area Atmospheres. This new section discusses methane layering in sealed areas and asserts that gaseous diffusion will result in a relatively homogeneous mixture within a matter of days after sealing. Other minor changes are related to rounding to metric units (sample pipes should extend 16 feet (5 meters) into the sealed area) and the inclusion of recent NIOSH research on methane flammability that lists the flammability range of methane-air mixtures at sea level as 5.0 percent to 16.0 percent methane. On December 7, 2007, MSHA posted on the Agency's Web site the U.S. Army Corps of Engineer's Draft Report ``CFD [Computational Fluid Dynamics] Study and Structural Analysis of the Sago Mine Accident'' (USACE's Draft Report). The Agency placed the Report in the rulemaking record for the ETS on Sealing of Abandoned Areas. The Report summarizes the preliminary results of a study performed by the USACE under contract (MSHA NO IA-AR 600012) for MSHA's Technical Support Directorate (Technical Support). The USACE conducted research from August 2006 to April 2007. The USACE provided a draft of the Report of their findings to Technical Support in May of 2007. The Report details the USACE's efforts to mathematically model the methane explosion at the Sago Mine and potentially establish the seal overpressures. On December 19, 2007, MSHA published a notice (72 FR 71791) to reopen the comment period; announce availability of the USACE's Draft Report; schedule a public hearing; and announce the close of the comment period. A public hearing was held in Arlington, Virginia on January 15, 2008 and the comment period closed on January 18, 2008. In developing this final rule, MSHA considered the investigation reports of the Sago and Darby mine explosions, implementation and enforcement experience under the ETS, MSHA's in-mine seal evaluations and review of technical literature, the 2007 NIOSH Draft and Final Reports on explosion testing and modeling, the USACE's Draft Report, accident reports, research studies, public comments, hearing transcripts and supporting documentation from all segments of the mining community. II. Discussion of the Final Rule This final rule assures that miners can rely on seals to protect them from the hazardous and sometimes explosive environments within sealed areas. This final rule includes requirements for seal strengths; design applications and installation; sampling and monitoring of sealed atmospheres; construction and repair of seals, training for persons conducting sampling and persons constructing or repairing seals, and recordkeeping to protect miners from hazards of sealed areas. Underground coal mines are dynamic work environments in which the working conditions can change rapidly. Caved, mined-out areas may contain coal dust and accumulated gas which can be ignited by rock falls, lightning, and in some instances, fires started by spontaneous combustion. Seals are used to isolate this environment from the active workings of the mine. Seals are also installed to withstand overpressures resulting from explosions in abandoned areas and to prevent the potentially explosive methane/air mixtures from migrating to the working areas. Overpressure is the pressure above the background atmospheric pressure. For example, air pressure in a car tire is measured with a pressure gauge as 30 psi, which is an overpressure. The absolute pressure of the air inside the tire is 44.7 psi which is 14.7 psi or one atmosphere higher. Explosion pressures are normally expressed as an overpressure beyond standard atmospheric pressure. A methane/air mixture becomes explosive when 5 percent to 15 percent methane is present with at least a 12 percent oxygen concentration. If an ignition source is available, then an explosion can occur and create overpressures. The homogeneity of the methane/air mixture contributes to the magnitude of the explosion. The homogeneity of the methane/air mixture can vary depending on the elevation and the methane liberation of the sealed area and outside factors such as the temperature and barometric pressure. The speed of an explosion and the physical characteristics of a sealed area can increase the force of the explosion such that detonations and significant pressure piling may be possible. Pressure piling is the development of pressure in excess of normal atmospheric pressures as a result of the velocity-related compression of the gases in front of the flame. Pressure piling results from the rapid acceleration of the front of the flame. This acceleration process may be increased by cross-sectional restrictions, obstructions and other irregularities in the path of the flame. If the air flow ahead of the front of the flame is sufficiently turbulent, the flame speed may increase and transition from deflagration to detonation. A detonation occurs when the flame of an explosion propagates through the unburned fuel at [[Page 21184]] a velocity exceeding the speed of sound. A deflagration occurs when the flame of an explosion propagates through unburned fuel at a velocity below the speed of sound. This final rule addresses seal strength design, construction, maintenance and repair of seals and monitoring and control of atmospheres behind seals in order to reduce the risk of seal failure and the risk of explosions in abandoned areas of underground coal mines. It also addresses the level of overpressure for new seals. This final rule will protect miners from hazards of sealed areas. III. Section-by-Section Analysis A. Section 75.335 Seal Strengths, Design Applications, and Installation The final rule addresses the requirements for seal strengths, design applications, and seal installation. 1. Section 75.335(a) Seal Strengths Final Sec. 75.335(a) requires that seals constructed in underground coal mines after October 20, 2008 be designed, constructed and maintained in accordance with the provisions of this final rule. Final Sec. 75.335(a)(1)(i), like the ETS, requires that seals withstand at least 50-psi overpressure when the atmosphere in the sealed area is monitored and maintained inert. Final Sec. 75.335(a)(1)(i) adds new requirements that these seals be designed using a pressure-time curve with an instantaneous overpressure of at least 50 psi, and that the minimum overpressure must be maintained for at least four seconds and then released instantaneously. Final Sec. 75.335(a)(1)(ii) addresses new requirements that seals constructed to separate the active longwall panel from the longwall panel previously mined be designed using a pressure-time curve with a rate of pressure rise of at least 50 psi in 0.1 second, and that a minimum overpressure of at least 50 psi be maintained. Final Sec. 75.335(a)(2)(i) revises the ETS and requires that seals withstand overpressures of at least 120 psi if the atmosphere in the sealed area is not monitored, is not maintained inert, and the conditions in final Sec. 75.335(a)(3)(i) through (iii) of this section are not present. Final Sec. 75.335(a)(2)(i) also adds new requirements that these seals be designed using a pressure-time curve with an instantaneous overpressure of at least 120 psi, and that a minimum overpressure of 120 psi be maintained for at least four seconds and then released instantaneously. Final Sec. 75.335(a)(2)(ii) adds new requirements that seals constructed to separate the active longwall panel from the longwall panel previously mined be designed using a pressure-time curve with a rate of pressure rise of 120 psi in 0.25 second, and that a minimum overpressure of 120 psi be maintained. Final Sec. 75.335(a)(3) is essentially unchanged from the ETS. It requires seals to withstand overpressures greater than 120 psi if the atmosphere in the sealed area is not monitored and is not maintained inert, and either (i) the atmosphere in the sealed area is likely to contain homogeneous mixtures of methane between 4.5 percent and 17.0 percent and oxygen exceeding 17.0 percent throughout the entire area; or (ii) pressure piling could result in overpressures greater than 120 psi in the area to be sealed; or (iii) other conditions are encountered, such as the likelihood of a detonation in the area to be sealed. Final Sec. 75.335(a)(3)(iv) retains the ETS requirement that when homogenous explosive atmospheres, pressure piling or the likelihood of a detonation exists, the mine operator must revise the ventilation plan to address the potential hazards. In addition, the operator must conduct an analysis of the mining conditions and revise the plan to include seal strengths sufficient to address these conditions. MSHA received many comments in response to its request on the appropriateness of the three-tiered approach to seal strength in the ETS. One commenter stated that the strength requirements in the first and second tier are arbitrary. Other commenters objected to the fixed seal strengths and requested that either a case-by-case determination or a risk analysis be made to determine which seal strength is needed. One commenter suggested that a two-tiered approach is adequate and that a third tier is not needed. A commenter stated that the 120-psi value proposed in the ETS is sufficient for design purposes and that the 120- psi load prescribed by the ETS is the highest design criterion for seals among all the coal producing countries. Another commenter stated that an explosion with a force greater than 120 psi could not occur in an underground coal mine. Other commenters, however, stated that greater than 120-psi explosion pressures can occur in sealed areas. Some commenters suggested that a 640-psi seal, as recommended by NIOSH, should be included in the standard. One commenter on the USACE's Draft Report stated that MSHA should consider a provision in the final rule that would assure that seals are explosion-proof. The Agency believes that a risk based analysis to determine seal strengths on a case-by-case basis rather than the tiered approach is not appropriate for several reasons. In the ETS, the Agency requested comments on alternatives to the seal strength requirements in the ETS, including supporting data, feasibility, and costs. MSHA did not receive any specific information, relative to alternatives requested, that would support a risk-based analysis on a case-by-case basis in this final rule. The rulemaking record contains little information supporting a case for risk analysis or costs and feasibility of such an approach. Commenters did not address how risk analysis on a case-by- case basis would impact the final rule and miner safety. Since the rulemaking record does not support this alternative approach to determine seal strengths, MSHA has not included it in this final rule. The strength requirements for final Sec. 75.335(a) are based on MSHA's investigation of the explosion at the Sago mine and the 2007 NIOSH Final Report. NIOSH discovered through research testing and modeling that a 50-psi peak overpressure could occur in a limited- volume, unconfined situation. Small, unconfined pockets of gases in an explosive concentration could always exist in a sealed area. If any of these pockets were ignited, a 50-psi pressure pulse could be generated. In addition, NIOSH stated that a 120-psi peak pressure could occur in a limited, confined-volume situation. According to NIOSH, in such a situation, even if the overall concentration of explosive gases in the gob is well above the explosive concentration, explosive concentrations could be present in some areas. NIOSH further stated that if an explosive mix of methane and oxygen is ignited in this situation, an explosion could generate a peak explosion pressure of 120-psi. Based on the 2007 NIOSH Final Report and the Agency's data and experience, this final rule retains the second tier of the ETS. Unlike NIOSH's design curves for 50-psi and 120-psi overpressures, NIOSH did not recommend a static approximation to the 640-psi pressure- time curve because ``Additional studies are required * * *.'' (2007 NIOSH Final Report at pg. 61). Although the NIOSH 640-psi pressure-time curve could be used to design seals, in this case a dynamic analysis would have to be conducted by the professional engineer. MSHA considered NIOSH's 640-psi seal design. However, a prescriptive specific dynamic load factor based on the 640-psi design was not determined and [[Page 21185]] requires further studies as stated in the 2007 NIOSH Final Report. As stated in the ETS, ``Although the recommended maximum seal strength in the 2007 NIOSH Draft Report is 640 psi, MSHA has no empirical or other data at this time, demonstrating that mine conditions exist that will necessitate seals stronger than 120 psi.'' One commenter on the USACE's draft report questioned this statement. MSHA stated in a Memorandum from its Office of Technical Support that ``these comparisons [between the USACE Report and known conditions after the Sago Mine explosion] again brought the practical applicability of results of the study into question.'' The Memorandum further states that: ``Technical Support decided not to publish the study because the critical information necessary to develop an accurate simulation was not available, and therefore, any results could not be relied upon for decision-making. Much of the data provided to the USACE for the three simulations described in the draft report was speculative * * *'' Based on the Agency's available information and data, MSHA could not specifically recommend a 640-psi strength requirement. The final rule retains the third tier of the ETS and requires a seal stronger than 120 psi if certain conditions are encountered. Under the final rule, mine operators must perform a risk analysis and evaluate the atmosphere of the area to be sealed and determine when higher pressure seals should be used and at what strength. The seal design must be approved at the appropriate strength for the specific conditions to be encountered. Most commenters expressed concern that under the ETS, it is virtually impossible to determine when the conditions requiring a seal greater than 120 psi are present. MSHA has structured the final rule to accommodate pressures greater than 120 psi in recognition of the fact that explosion pressures may exceed this limit under certain conditions. These conditions would be a concern only in sealed areas that are not monitored and not maintained inert. The final rule requires seal strengths greater than 120 psi if seals are constructed around areas that are not monitored and are not inert, and one of the following three conditions occurs: (1) A homogeneous explosive atmosphere exists, (2) pressure piling could result in pressures exceeding 120 psi, or (3) detonation is likely. MSHA expects that mine operators will sample an appropriate number of locations within the sealed area during the period when seals are reaching their design strength to address whether a homogeneous explosive atmosphere exists. These samples could be taken at various locations, including through seals constructed around the sealed area and possibly through boreholes or shafts within the sealed area. When these seals reach design strength of 120 psi, sampling is no longer required. If the methane concentration stabilizes between 4.5 percent and 17 percent and the oxygen concentration remains above 17 percent in all samples, then the atmosphere is considered homogeneous throughout the sealed area, and seal strengths must be designed to an adequate level above 120 psi, as determined by the professional engineer, which will provide adequate protection for miners underground. MSHA realizes that the seals surrounding the sealed area must be in place prior to sampling. MSHA expects that mine operators will evaluate the physical characteristics of the underground workings near all seals surrounding the sealed area to address whether pressure piling can occur to a degree that causes explosion overpressures to exceed 120 psi. Overpressures that occurred during the 2006 explosion at the Sago Mine increased in magnitude due to a severe change in the physical characteristics of the underground workings near the seals. The seals at the Sago Mine were constructed to a height of approximately 7 feet. The workings in the sealed area had been previously second mined to a height of nearly 20 feet in some locations near the seals. As the explosion propagated toward the seals, pressure piling occurred and caused excessive pressure at the location of the seals. These factors must be considered by the mine operator to determine if a situation exists that will cause pressure piling, resulting in pressures above 120 psi. If this situation exists, then seal strengths must be designed to an adequate level above 120 psi, as determined by the professional engineer. MSHA expects that mine operators will fully evaluate potential ignition sources, potential methane concentrations, and potential oxygen concentrations in the sealed areas to determine if detonation could occur. Mine operators should consider whether a high energy ignition source exists in the sealed area, whether extensive volumes of homogeneous mixtures of explosive methane concentrations may exist, and whether sufficient oxygen may be present in the sealed area. MSHA received several comments on the USACE's Draft Report. The report details the USACE's efforts to mathematically model the methane explosion at the Sago Mine and potentially establish the seal overpressures. The report recommended that additional research was needed to refine the models in order to better predict an explosion pattern. Commenters stated that computational fluid dynamics modeling could be used effectively to compare the effect of different variables on explosions, but that this type of modeling cannot accurately predict conditions. According to one commenter, their data collection and analysis of an actual gob composition is highly non-homogeneous, and the chance of methane gas detonation in a coal mine is almost zero. Therefore, this commenter stated that the 120-psi criterion in the ETS is adequate. Final Sec. Sec. 75.335(a)(1)(i) and (a)(2)(i) include requirements that seal designs must resist explosions of specific duration and intensity. The duration and intensity is characterized in pressure-time curves. A pressure-time curve gives engineers a mechanism to perform a dynamic analysis or to derive a dynamic load factor that they can use in a static analysis of a design. The pressure-time curves in Figures 1 and 2 yield a dynamic load factor (DLF) of 2.0, which is the theoretical maximum (Structures to Resist the Effects of Accidental Explosions, Department of the Army, Report TM 5-1300, November 1990) (1990 Department of the Army Report). Holding the applied pressure for at least four seconds assures that a seal could be loaded elastically at a DLF of 2.0 (1990 Department of the Army Report). The instantaneous release of the overpressure load after at least four seconds gives engineers a criterion to address the rebound effect that would occur in the seal after the explosive force was removed. Under this final rule, a professional engineer could submit, for MSHA approval, a unique design that is able to withstand the prescribed design criteria. Figures 1 and 2 are the 50-psi and 120-psi pressure-time curves to be used for seal design. [[Page 21186]] [GRAPHIC] [TIFF OMITTED] TR18AP08.009 [GRAPHIC] [TIFF OMITTED] TR18AP08.010 Several commenters requested a more prescriptive design standard identifying minimum overpressures. MSHA believes that a more prescriptive standard would eliminate ambiguity and result in greater protection of miners. In response to these comments and for clarity, final Sec. Sec. 75.335(a)(1)(i) and (a)(2)(i) provide specific pressure-time curves for certain seal designs. Some commenters requested that they be allowed to use seals constructed to separate the active longwall panel from the longwall panel previously mined. These commenters stated that such seals protect miners from explosions and help control spontaneous combustion, which has historically been a problem in the western U.S. mines. MSHA's enforcement policy under the ETS is consistent with the prescriptive design requirements in final Sec. Sec. 75.335(a)(1)(ii) and (a)(2)(ii) for these types of seals. These provisions allow seals to be designed using pressure-time curves that characterize an explosion having pressure venting and slower pressure rise times. Such pressure-time curves are published in the 2007 NIOSH Final Report. Both NIOSH 50-psi and 120-psi pressure-time curves for these seals yield a dynamic load factor of 1.0. The caved roof gob adjacent to seals used to separate the active longwall panel from the longwall panel previously mined minimizes run-up distances, which may otherwise be long enough to generate steeper rise times on either pressure pulse. Thus, both pressure-time curves enable engineers to analyze these seal designs based upon a dynamic analysis or a static, uniform pressure, which is equal to the peak overpressure in the applicable pressure-time curve. Figures 3 and 4 are the 50-psi and 120-psi pressure-time curves that can be used for the design of seals that separate the active longwall panel from the longwall panel previously mined. [[Page 21187]] [GRAPHIC] [TIFF OMITTED] TR18AP08.011 [GRAPHIC] [TIFF OMITTED] TR18AP08.012 Several commenters asked that explosion wave mitigation procedures be allowed in lieu of seal designs to withstand overpressures greater than 120-psi. Based on MSHA's knowledge and experience, if a seal is to withstand overpressures at the design seal strength, then wave mitigation methods may not provide effective protection. Most wave mitigation techniques are designed for a one-time use, after which they do not offer any quantifiable resistance to explosion overpressure. While wave mitigation methods are not discouraged by MSHA, wave mitigation alone cannot be used to meet the requirements of the standard. Several commenters inquired about a safety factor in the seal designs. Some commenters believed that the seal design requirement in the ETS included a safety factor of two. Like the ETS, this final rule does not require a safety factor in any seal designs. As mentioned above, for static-equivalent seal designs using either of the two prescribed pressure-time curves having an instantaneous rise, a Dynamic Load Factor (DLF) of 2 would be applied to the peak overpressure. The DLF is multiplied by the peak overpressure for a static-equivalent overpressure for which the seal should be designed to resist. For example, a 120-psi seal designed with a static-equivalent procedure would have to withstand a design static overpressure of 240 psi. The two prescribed pressure-time curves that are permitted for use with seals constructed to separate the active longwall panel from the longwall panel previously mined have a DLF of 1. A DLF is not a factor of safety. It is a ratio used to equate a dynamic load with a static load for design purposes. Professional engineers are expected to incorporate load factors in their designs, in addition to the DLF, in accordance with current prudent structural engineering practices. Many commenters questioned why Mitchell-Barrett seal designs were not permitted under the ETS. Some commenters stated that Mitchell- Barrett seals were tested by NIOSH and that they are capable of holding a static load over 95 psi. This maximum 95 psi overpressure was generated in a small-volume chamber behind the tested seal and was not generated by an explosion pressure wave traveling down a mine opening at the Lake Lynn Experimental Mine, as seals had been tested previously. NIOSH attempted to establish equivalency of a small-volume chamber to the full-scale explosion tests. NIOSH did not establish equivalency between the two types of tests. Also, the pressure-time curve in this final rule for 50-psi seals incorporates a DLF of 2 and results in a static equivalent load of 100 psi. This static equivalent load is greater than the 95 psi static load that NIOSH measured. Mitchell-Barrett seals that were tested [[Page 21188]] by NIOSH would not be permitted under this final rule for 50-psi seals requiring a DLF of 2.0. One commenter stated that the ETS would cause existing seals in three mines operated by the mine operator to be replaced with 50-psi rated seals and that replacement of the existing seals would be costly. The final rule does not require replacement of existing seals; rather, for existing seals, it requires operators to monitor methane and oxygen concentration levels and to maintain an inert atmosphere in the sealed area. Another commenter stated that the turnkey costs for seals used in the company's mines ranged from $12,000 to $25,000 and stated that MSHA had severely understated costs. However, the Agency's cost estimates are weighted averages of the costs for various types of seals. MSHA's estimated turnkey costs range from approximately $7,370 to $25,000 for 50 psi seals and $11,330 to $38,550 for 120 psi seals. The commenter's costs come within the range of seal costs MSHA used to develop its cost estimates. 2. Section 75.335(b) Seal Design Applications Final Sec. 75.335(b) renumbers and revises ETS Sec. 75.336(a). It requires that seal design applications be based on either engineering design applications or full-scale explosion tests. The final rule permits the applicant to use other equivalent means of physical testing in lieu of full-scale explosion tests. The final rule also requires that seal design applications from seal manufacturers or mine operators be submitted for approval to MSHA's Office of Technical Support, Pittsburgh Safety and Health Technology Center, P.O. Box 18233, Cochrans Mill Road, Pittsburgh, PA 15236. Final Sec. 75.335(b)(1), like the ETS, sets forth specific requirements for an engineering design application. Under final Sec. 75.335(b)(1)(i), an engineering design application must address the following: Gas sampling pipes, water drainage systems, methods to reduce air leakage, pressure-time curve, fire resistance characteristics, flame spread index, entry size, engineering design and analysis, elasticity of design, material properties, construction specifications, quality control, design references, and other information related to seal construction. Section 75.335(b)(1)(i) has been revised to include elasticity of design in the engineering design application. MSHA has included this requirement in the final rule for clarity. It is based on the 2007 NIOSH Final Report and on MSHA's experience with seal design approvals under the ETS. NIOSH notes in the 2007 NIOSH Final Report that repeated pressure waves will likely impact the seal structure. Applications for seals designed for overpressures of 120 psi or greater must address elasticity in their design in order to withstand repeated, independent overpressures. This is consistent with current prudent engineering practices and with MSHA's seal approval process under the ETS. Addressing elasticity in seal design does not require a higher seal strength than that under the ETS. The final rule is consistent with MSHA's approved seal designs under the ETS. This final rule retains the other requirements of the ETS. Final Sec. 75.335(b)(1)(ii), like the ETS, requires that an engineering design application be certified by a professional engineer that the design of the seal is in accordance with current, prudent engineering practices. In addition, it clarifies the ETS requirement and specifies that the professional engineer certify that the seal design is applicable to conditions in an underground coal mine. In the ETS, MSHA discussed the engineering decisions and actions that must be made by and must be the responsibility of the professional engineer. Those included (1) the selection or development of design standards or methods, and materials to be used in seal construction; (2) the development and preparation of the structural analyses and design computations, drawings, and specifications; (3) the selection or development of techniques or methods of testing to be used in evaluating materials used either during seal construction or following completion of seal construction; and (4) the development of construction procedures. This final rule clarifies MSHA's intent that a seal design must reliably function given a set of specific conditions in an underground coal mine, and that a professional engineer must certify that the seal design is applicable to conditions in an underground coal mine. Several commenters stated that professional engineers who are required to comply with the engineering design application requirements in the ETS could lose complete dominion and control over the design of a seal. A commenter stated that West Virginia state law requires a professional engineer to maintain complete direction and control over all specifications, reports, drawings, plans, design information, and calculations to be certified. Commenters raised an issue concerning a seal designed by MSHA but requiring certification by a professional engineer. Under the ETS, this particular seal approval required a separate review and certification by a professional engineer before it could be used. However, the professional engineer may also use that particular design as basis for a new seal design and submit it to MSHA for approval. A commenter stated that the design of mine seals for use in West Virginia is engineering work and requires that it be done by a registered West Virginia professional engineer. MSHA accepts the certification of a professional engineer from any state and allows that certification to be used in other states. Each state is responsible for enforcing its rules and regulations. Another commenter stated that because field conditions change the professional engineer must be allowed to make the necessary field changes to meet those conditions in order to protect the public safety. MSHA acknowledges that some field conditions may change but because of the importance and complexity of the seal designs, the final rule does not permit field changes. Like the ETS, the final rule allows the mine operator to make revisions to the original approved design by submitting those changes that are certified by a professional engineer to MSHA's office of Technical Support for approval. Final Sec. 75.335(b)(1)(iii) revises ETS Sec. 75.336(a)(1)(iii) and requires that an engineering design application include a summary of the installation procedures related to seal construction. Based on MSHA's field experience under the ETS, the requirement for a summary of installation procedures is more appropriate than that in the ETS for specific information to be included in a Seal Design Table. Under the final rule, the summary should include all of the information necessary to construct a seal including quality control and other necessary information. The application must list provisions that specify quality control procedures for construction and include requirements for material sampling and testing. Material testing should be conducted by a certified laboratory and by qualified personnel. The certification for the laboratory must be from a professional organization such as the International Organization for Standardization (ISO) and the personnel must be able to demonstrate qualifications to ensure proper quality control testing. MSHA's experiences under the ETS reveal that some information included in the seal design application is proprietary. Although this information is required to be submitted to Technical Support for evaluation of [[Page 21189]] the design, it is not necessary to include it in the ventilation plan for approval by the District Manager. The requirement for the summary information will eliminate the need to disseminate any proprietary information. It will provide the District Manager with information needed to approve the seal design in the ventilation plan. Final Sec. 75.335(b)(2) requires that seal design applications can be based on full-scale explosion tests or equivalent means of physical testing. During discussions with MSHA on alternatives to full-scale testing, NIOSH indicated that equivalent testing conditions can be represented in suitable hydrostatic test chambers similar to those at the NIOSH Lake Lynn Experimental mine. MSHA believes that an equivalent means of physical testing, that has at least the same level of confidence as full-scale explosion testing, is an acceptable means of compliance and the Agency has included it in the final rule. Final Sec. 75.335(b)(2)(i), like ETS Sec. 75.336(a)(2)(i), requires certification by a professional engineer that the testing was done in accordance with current, prudent engineering practices for construction in a coal mine. This final rule deletes the requirement in the ETS that the professional engineer be knowledgable in structural engineering. MSHA deleted this requirement because there is no certification available to assure that a professional engineer is knowledgable in structural engineering. MSHA's experience with seal design approvals under the ETS reveals that the Professional Engineers who successfully submit seal designs are knowledgable in structural engineering. MSHA received one comment on this provision which recommended the words ``knowledgable in structural engineering'' be removed. Final Sec. 75.335(b)(2)(ii), like ETS Sec. 75.336(a)(2)(ii), requires the applicant to provide technical information related to the methods and material used to construct and test the seals. MSHA received no comments on this provision. Final Sec. 75.335(b)(2)(iii) requires that the application include supporting documentation. This clarifies ETS Sec. 75.336(a)(2)(iii) that required proper documentation. The term ``supporting'' more accurately describes the type of documentation required. This documentation includes: Engineering analyses, construction drawings and specifications, and data that address seal material, fire resistance and flame-spread index. The applicant must establish the materials and material properties required for adequate seal construction. Construction documentation is required to assure that the seals are properly built and reliable to address air leakage, and to verify that the material properties of the seal will meet the specified strength criteria. MSHA received no comments on this provision. Final Sec. 75.335(b)(2)(iv), like ETS Sec. 75.336(a)(2)(iv), requires the application to include an engineering analysis addressing differences between the seal support during test conditions and the range of test conditions in a coal mine. MSHA received no comments on this provision. Final Sec. 75.335(b)(2)(v) revises ETS Sec. 75.336(a)(2)(v) and requires that a summary of the installation procedures be included in the application. This requires that applicants submit more appropriate information in the form of a summary of installation procedures rather than specific information included in a Seal Design Table as required by the ETS. This summary should include the installation procedures related to mine specific seal construction. For example, it would include the maximum entry width and height for which the specific design is applicable, the specified strength of the seal material, the thickness of the seal, and the reinforcement and anchorage requirements for the seal. Additional information may be provided at the discretion of the Professional Engineer. MSHA received no comments on this provision. Final Sec. 75.335(b)(3), like ETS Sec. 75.336(a)(3), provides that MSHA will notify the applicant if additional information or testing is required. It also requires the applicant to provide this information, arrange any additional or repeat tests, and provide prior notification to MSHA of the location, date, and time of such tests. MSHA received no comments on this provision. Final Sec. 75.335(b)(4), like ETS Sec. 75.336(a)(4), provides that MSHA will notify the applicant, in writing, whether the design is approved or denied. It also provides that if the design is denied, MSHA will specify, in writing, the deficiencies of the application, or necessary revisions. MSHA received no comments on this provision. Final Sec. 75.335(b)(5), like ETS Sec. 75.336(a)(5), requires that once the seal design is approved, the approval holder must promptly notify MSHA, in writing, of all deficiencies of which they become aware. MSHA received no comments on this provision. 3. Section 75.335(c) Seal installation approval Final Sec. 75.335(c), like ETS Sec. 75.336(b), requires that the installation of the approved seal design be approved in the ventilation plan. Final Sec. 75.335(c)(1), like the ETS, requires the mine operator to retain the seal design approval and installation information for as long as the seal is needed to serve the purpose for which it was built. One commenter stated the requirement to retain approval and installation information for an indefinite period places an onerous burden on both the professional engineer and the mine operator, and suggested that the final rule include a definite duration for retaining this information. Based on MSHA's experience under the ETS, the requirement for approval and installation information provides a reliable reference should any problems occur during the service life of the seal. This provides valuable information as to how the seal was constructed and identifies the person responsible for certifying that the provisions in the approved seal design were addressed. In some instances, this information may enable persons to question individuals responsible for designing and constructing the seal to gain an insight as to the circumstances surrounding the construction and identify any problems that may have been encountered during the construction. Accordingly, this provision remains unchanged from the ETS. Final Sec. 75.335(c)(2), like the ETS, requires that the mine operator designate a professional engineer to conduct or have oversight of seal installation and certify that the provisions in the approved seal design specified in this section have been addressed and are applicable to the conditions in the mine. This final rule also requires that a copy of the certification be submitted to the District Manager with the information provided in final Sec. 75.335(c)(3) and that a copy of the certification be retained for as long as the seal is needed to serve the purpose for which it was built. One commenter supported this provision and stated that creating accountability in the construction process is a critical component if MSHA is to assure that coal operators take very seriously their obligation to provide a safe workplace with properly designed and constructed seals. Several commenters opposed this provision. They stated that the requirement to conduct or have oversight of seal installation should be deleted because it would be expensive, difficult because there are many variables in the construction process, and unnecessary because a mine operator must also certify construction. Some commenters stated that a [[Page 21190]] professional engineer's function is the design of a seal, not oversight of the construction. Several commenters stated that the provision would require a professional engineer to be on site prior to, during, and following construction of every seal to insure that all parameters are met and that would be unnecessary. Under the final rule, MSHA does not intend that the professional engineer take part in the construction process or be at the seal installation site during the entire construction process. MSHA stated its intent with respect to this requirement at the public hearings. MSHA's existing enforcement policy states that the professional engineer must inspect the set of seals during construction as part of the oversight and certification required by ETS Sec. 75.336(b)(2). To accomplish this oversight, MSHA would expect the professional engineer to: (1) Verify that the seal application is suitable for the specific conditions, (2) confirm that the site preparation is adequate, (3) confirm that the workforce is adequately trained to properly build the seals, (4) verify that the correct materials and procedures are being used to construct the seal, and (5) confirm that adequate quality controls are in place and are being followed. The professional engineer however, does not have to be onsite the entire time that seals are being built. Based on the Agency's knowledge and experience, MSHA has determined that the oversight by the professional engineer, who would be most familiar with the seal design, will help assure that appropriate seal design implementation and related analyses are performed properly. In addition, it will assure that seals are constructed according to the drawings and specifications of a professional engineer. Final Sec. 75.335(c)(3), like the ETS, lists specific information that a mine operator must address in the ventilation plan. The information will be used by the District Manager to evaluate a seal installation and determine whether the seal design is appropriate for a particular site. Final Sec. 75.335(c)(3)(i), like the ETS, requires that mine operators include the MSHA Technical Support Approval Number of the seal design in the ventilation plan. MSHA did not receive any comments on this section. This final rule is unchanged from the ETS. Final Sec. 75.335(c)(3)(ii) revises ETS Sec. 75.336(b)(3)(iii)(D). It requires a summary of the installation procedures for approval to be included in the ventilation plan. This final rule is derived from the ETS requirement that the mine operator specify construction techniques for each type of seal. It revises the ETS requirement to be consistent with the language in final Sec. 75.335(b)(1)(iii). The information required in this final rule, however, is essentially the same as that required in the ETS. Examples of information required by this provision include: Maximum entry width and height for which the design is applicable; specified strength of the seal; construction steps; and reinforcement and foundation anchorage requirements. In addition, when frame work is used, information should specify frame work size, spacing and materials used, a description of how the frame work is erected, size of other material used, such as concrete block size, wood products used and spacing, and, if needed, an anchorage table for rebar showing lengths, hole size, and other material used with the rebar. If hitching is required, information should specify hitching location, width and depth, calibration of equipment where required, sequence of pouring materials and thickness, sequence and type of roof support used, surface preparation, a description of the material pouring techniques and how cold joints may or may not be permitted, set back distances, a diagram of the water drainage system and air sampling installation, methods for preventing water retention during the curing process, rockdust removal from rib at the seal site, thickness of the seal, and other additional information in the seal design application. Final Sec. 75.335(c)(3)(iii) revises the ETS. It requires that mine operators provide, in the ventilation plan, a mine map of the area to be sealed and proposed seal locations that include the deepest points of penetration prior to sealing. This final rule revises the ETS by requiring that locations include the deepest points of penetration prior to sealing. This provision will help assure that the area was surveyed, a map of the area to be sealed was completed and the map was submitted by the mine operator. In addition, this final rule requires that the mine map be certified by a professional engineer or a professional land surveyor. It revises the ETS by including a professional land surveyor to certify the mine map to be consistent with existing Sec. 75.1201 which permits a professional land surveyor to certify the mine map. Final Sec. 75.335(c)(3)(iv), like the ETS, requires that mine operators submit specific mine site information in the ventilation plan. Final Sec. 75.335(c)(3)(iv)(A) requires that the type of seal be included in the ventilation plan. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(B), like the ETS, requires mine operators to include information in the ventilation plan on the safety precautions taken prior to seals achieving design strength. Some commenters stated that this provision should require withdrawal of miners. According to commenters, this would be consistent with NIOSH's recommendation that miners be withdrawn from the affected area until seals reach design strength and the atmosphere in the sealed areas reaches an inert status. Other comments stated that withdrawal is not necessary because the sealed areas contain no likely ignition source, and if an inert atmosphere is present, uncured seals do not present an imminent danger as there is no explosion potential. In addition, some of these commenters stated that withdrawal of miners during seal curing time, which could be up to 28 days, would be too costly. Based on MSHA's knowledge and experience under the ETS, miners could be exposed to the dangers of an explosion prior to seals achieving their design strength. Accordingly, MSHA believes that safety precautions need to be taken prior to seals achieving design strength. Safety precautions could include withdrawing miners from the entire mine or other area approved by the District Manager. They could also include the use of seals that reach their design strength in considerably less time than 28 days. In addition, the mine operator could inert the atmosphere prior to or during seal installation. If an inert atmosphere is present behind seals that have not reached their design strength, miners would not need to be withdrawn from the affected area. This provision remains unchanged from the ETS. Final Sec. 75.335(c)(3)(iv)(C) revises the ETS. It requires that the mine operator provide information in the ventilation plan on methods used to address site-specific conditions that may affect the strength and applicability of the seal, including set-back distances. The set-back distance, which is the distance from the corner of a pillar block to a seal, is critical to the long term stability and protection of a seal. Although the ETS did not specifically address set-back distances, many professional engineers included this concept in their design applications. Based on MSHA's experience under the ETS, professional engineers designing seals have listed a minimum set-back distance of 10 feet when applying for a seal design approval in most instances. MSHA believes, [[Page 21191]] however, that set-back distances need to be addressed on a mine-by-mine basis. Some coal is softer or harder than others; and the overburden varies, which has an effect on the stability of the coal seam pillar. This means that some coal pillars will remain more or less stable than others over a long period of time. It is also possible to artificially reinforce the stability of less stable coal pillars, for example, by injecting materials into the pillars. Therefore, MSHA is including a requirement that the set-back distance of a seal be addressed in the mine ventilation plan during the seal plan approval process. Final Sec. 75.335(c)(3)(iv)(D), like the ETS, requires the mine operator to submit information in the ventilation plan on site preparation. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(E), like the ETS, requires the mine operator to include information on the sequence of seal installations in the ventilation plan. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(F), like the ETS, requires that the mine operator provide information in the ventilation plan on the projected date of completion of each set of seals. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(G), like the ETS, requires the mine operator to provide information in the ventilation plan on the supplemental roof support inby and outby each seal. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(H), like the ETS, requires the mine operator to provide information in the ventilation plan on the water flow estimation and dimensions of the water drainage system through the seals. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(I), like the ETS, requires that the mine operator provide information in the ventilation plan on the methods used to ventilate the outby face of seals once completed. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(J), like the ETS, requires the mine operator to provide information in the ventilation plan on the methods and materials used to maintain each type of seal. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(K), like the ETS, requires the mine operator to provide information in the ventilation plan on methods used to address shafts and boreholes in the sealed area. MSHA did not receive any comments on this provision. Final Sec. 75.335(c)(3)(iv)(L) is derived from ETS Sec. 75.335(a)(3)(iv). This final rule requires the mine operator to provide information in the ventilation plan on an assessment of potential for overpressures greater than 120 psi in the sealed area. ETS Sec. 75.335(a)(3)(iv) required the mine operator to revise the ventilation plan when conditions that would necessitate a seal greater than 120 psi are encountered. This final rule is consistent with the ETS. It includes this provision to assure that the mine operator evaluates the area to be sealed and addresses the need for seals greater than 120 psi. Final Sec. 75.335(c)(3)(iv)(M) renumbers and clarifies ETS Sec. 75.335(b)(5)(ii). It requires mine operators to provide information in the ventilation plan on additional sampling locations. This final rule is consistent with ETS Sec. 75.335(b)(5)(ii), which required the location of sampling points to be included in the mine operator's action plan. Under this final rule, additional sampling locations could include sampling through boreholes and capped shafts with vent pipes. Final Sec. 75.335(c)(3)(iv)(N), like the ETS, requires the mine operator to provide, in the ventilation plan, any additional information required by the District Manager. This final rule will help assure that any new developments in technology or any problems related to site-specific conditions in sealing may be addressed by the mine operator through the ventilation plan. MSHA did not receive any comments on this provision. B. Section 75.336 Sampling and Monitoring Requirements Final Sec. 75.336, derived from ETS Sec. 75.335(b), revises and renumbers sampling and monitoring requirements for sealed atmospheres. In the final rule, the terms ``sampling'' and ``monitoring'' are used interchangeably. The final rule deletes the requirement in the ETS for mine operators using seals designed to withstand less than 120 psi to develop and follow a protocol to monitor methane and oxygen concentrations in sealed atmospheres. The ETS required that the protocol be approved by the District Manager in the ventilation plan. Requirements to maintain and restore an inert atmosphere in the sealed area are discussed in final Sec. 75.336(b); requirements for sampling pipes are discussed in final Sec. 75.337(g). Requirements for welding, cutting and soldering are discussed in final Sec. 75.337(f); requirements for water drainage systems are discussed in final Sec. 75.337(h); and requirements for training of certified persons conducting sampling are discussed in final Sec. 75.338(a). Section 75.336(a) of the final rule retains the requirement in ETS Sec. 75.335(b) for a certified person, as defined under existing Sec. 75.100, to monitor sealed atmospheres for methane and oxygen concentrations. Unlike the ETS, the final rule requires sealed atmospheres to be monitored through each sampling pipe and approved sampling location whether seals are ingassing or outgassing. Training requirements for certified persons are addressed in final Sec. 75.338(a) and are unchanged from the ETS. Final Sec. Sec. 75.336(a)(1)(i) through (iii) address ETS requirements for sampling frequencies, including initial sampling periods and sampling on a continuing basis. Atmospheres with seals less than 120 psi constructed prior to October 20, 2008, and atmospheres with seals of less than 120 psi constructed after October 20, 2008 must be sampled through each sampling pipe and approved location at least every 24 hours. Under the final rule, the operator may request that the District Manager approve different frequencies and locations in the ventilation plan. Under the final rule, seals of 120 psi or greater must be monitored until they reach their design strength. After they reach their design strength, the final rule does not require the atmosphere in these sealed areas to be monitored and maintained inert. Final Sec. 75.336(a)(2) is derived from ETS Sec. Sec. 75.335(b)(1) and (b)(5) and requires the mine operator to evaluate the atmosphere in the sealed area to determine whether sampling through required sampling pipes under final Sec. 75.337(g) provides appropriate sampling locations. The final rule specifies the conditions under which the evaluation must be conducted. When the evaluation results indicate the need for additional sampling locations, the mine operator must establish additional sampling locations and include them in the ventilation plan for approval by the District Manager. Final Sec. 75.336(a)(3) requires mine operators with an approved ventilation plan addressing spontaneous combustion under existing Sec. 75.334(f) to monitor sealed atmospheres in accordance with the plan. Final Sec. 75.336(a)(4) is derived from ETS Sec. 75.335(b)(5)(vi) and allows the District Manager to approve the use of a continuous monitoring system in lieu of monitoring provisions in the final rule. Final Sec. 75.336(b)(1), like ETS Sec. 75.335(b)(3), defines an inert atmosphere as one in which the oxygen concentration is less than 10 percent, or [[Page 21192]] the methane concentration is less than 3.0 percent or greater than 20.0 percent. Final Sec. 75.336(b)(2) addresses corrective action necessary if the atmosphere is not inert. It requires that when a sealed atmosphere with less than 120-psi seals is not inert, the mine operator must take immediate action to reestablish an inert atmosphere and monitor the sealed atmosphere every 24 hours until it is restored to an inert status. Final Sec. 75.336(c) revises and clarifies ETS Sec. 75.335(b)(4) and specifies when persons must be withdrawn from the mine due to a hazardous atmosphere in the sealed area. Final Sec. 75.336(d) clarifies existing MSHA policy that allows the operator to request that the District Manager approve in the ventilation plan a different oxygen concentration if the atmosphere in the sealed area contains carbon dioxide. It also addresses sealed areas where inert gas has been injected, and sampling methods and equipment. Final Sec. Sec. 75.336(e)(1) and (e)(2) are the same as ETS Sec. Sec. 75.335(b)(6) and (b)(7) and include requirements for recording sampling results and any hazardous condition found in accordance with existing Sec. 75.363. 1. Section 75.336(a) Section 75.336(a) retains the requirement in ETS Sec. 75.335(b) for a certified person, pursuant to Sec. 75.100, to monitor sealed atmospheres. The final rule continues to require the certified person to monitor the sealed area for methane and oxygen concentrations. Under the final rule, unlike the ETS, sealed atmospheres must be monitored whether seals are ingassing or outgassing. Mine operators must also determine the direction of air leakage during monitoring which will indicate whether seals are ingassing or outgassing. Seals outgas when the pressure in the sealed area exceeds the pressure on the outby side of the sealed area. Seals ingas when the pressure outby the sealed area exceeds the pressure in the sealed area. ETS Sec. 75.335(b)(1) required mine operators to sample sealed atmospheres only when seals were outgassing. MSHA requested comments regarding: its sampling approach; sampling frequency; sampling only when a seal is outgassing; whether a different sampling approach would be more appropriate for the final rule, such as when seals are ingassing; and information and experiences of the mining community concerning sampling sealed areas. Commenters' views were divided regarding appropriate conditions for monitoring seals, especially on the issue of outgassing and/or inga