During December 2008, the Mine Safety and Health Administration (MSHA) issued a draft program policy letter (PPL) that provided mine operators guidance in implementing alternatives to fully wireless post-accident two-way communication between underground and surface personnel and electronic tracking systems, both of which are required by the MINER Act. The two-way communication alternatives
(or “partially wireless” systems) include infrastructure underground to provide un-tethered communications with miners.
Editor’s note: In accordance with the Good Guidance Bulletin, MSHA made the PPL on “Guidance for Compliance with Post-Accident Two-Way Com-munications and Electronic Tracking Requirements of the MINER Act” publicly available in the Federal Register and on the agency’s Web site for comment. Interested parties were asked to comment by midnight (EST) January 8, 2009. MSHA will consider initiating rulemaking on requirements for wireless post-accident communication systems and electronic tracking systems in the future. In the interim, the agency issued the draft PPL to respond to underground coal mine operators’ requests for guidance to assist them in implementing the requirements of the MINER Act in a timely and effective manner.
The MINER Act requires, by June 15, 2009, a plan be submitted that provides for a post-accident communication system between underground personnel and surface personnel via a wireless two-way medium and an electronic tracking system that permits surface personnel to determine the location of any persons trapped underground. If these provisions cannot be adopted, the MINER Act requires that Emergency Response Plans (ERPs) must set forth an alternative means of compliance that approximates, “as closely as possible, the degree of functional utility and safety protection provided by the wireless two-way medium and tracking system.”
With respect to tracking, because electronic systems currently are available and MSHA approved, new ERPs and revisions to existing ERPs should provide for electronic tracking of persons underground, according to MSHA. However, because fully wireless communications technology is not likely to be technologically feasible by June 15, 2009, this guidance addresses acceptable alternatives to fully wireless communication systems. New ERPs and revisions to existing ERPs, MSHA explained, should provide for alternatives to fully wireless communication systems.
The PPL represents MSHA’s current thinking with respect to two-way communication and electronic tracking for use in mine emergencies. It does not create or confer any rights for any person and it does not operate to bind mine operators or any other members of the public. Mine operators can use an alternative approach or system to provide two-way communication or electronic tracking, if the approach or system satisfies the requirements of applicable statutes and regulations. Interested parties may contact the MSHA district manager for the area in which the mine is located.
Two-Way Communication Systems
According to Section 2 of the MINER Act, until fully wireless systems are available, operators must set forth in their ERPs the reasons that they are proposing alternative systems (e.g., wireless systems are unavailable). The alternative system must approximate, as closely as possible, the degree of functional utility and safety protection provided by a wireless two-way communications system. While mine operators and MSHA district managers will consider mine-specific circumstances in determining appropriate two-way communications systems, the features MSHA believes would best approximate the functional utility and safety protections of a fully wireless system, given the limitations of current technology. As noted, operators and others may propose other approaches or systems. Communications systems that are already in use may need to be updated to comply with the MINER Act requirements to approximate the utility
and safety protections of a fully wireless system.
Alternatives can be systems used for day-to-day operations or a stored system used in the event of an accident. Examples of currently available technologies that may be capable of best approximating a fully wireless communications system, include, but are not limited to, leaky feeder, mesh, and medium frequency systems. Any alternative system generally should:
• Have an un-tethered device that miners can use to communicate with the surface. The un-tethered device should be readily accessible to each group of miners working or traveling together, and to any individual miner working or traveling alone.
• Provide communication in the form of two-way voice and/or two-way text messages. If used, pre-programmed text messages should be capable of providing information to the surface necessary to determine the status of miners and the conditions in the mine, as well as providing the necessary emergency response information to miners.
• Provide an audible, visual, and/or vibrating alarm that is activated by an incoming signal. The alarm should be distinguishable from the surrounding environment.
• Be capable of sending an emergency message to each of the untethered devices.
• Be installed to prevent interference with blasting circuits and other electrical systems.
The system must provide coverage for each working section in a mine including all intersections. The system also generally should provide continuous coverage along the escapeways and a coverage zone both inby and outby strategic areas of the mine, such as belt drives and transfer points, power centers, loading points, refuge alternatives, self-contained, self-rescuer (SCSR) caches, and other areas MSHA designates. While a coverage zone of 200 feet inby and 200 feet outby strategic areas normally should be adequate, MSHA may require longer or shorter distances given circumstances specific to the mine.
MSHA may approve alternative coverage areas, such as adjacent entries, for reasons such as radio frequency interference or other factors that may reduce the coverage area at the identified strategic areas. Miners should follow an established check-in/check-out procedure or an equivalent procedure when assigned to work in bleeders or other remote areas of the mine that are not provided with communications coverage.
As far as permissibility concerns, the communication system must be approved by MSHA to comply with 30 C.F.R. part 23 and applicable policies.
Stationary components (infrastructure) generally should be equipped with a standby power source capable of providing sufficient power to facilitate evacuation and rescue in the event the line power fails or is cut off. In many mining situations, at least 24 hours of standby power based on a 5% transmit time, 5% receive time, and 90% idle time duty cycle (denoted as 5/5/90) generally should be adequate, but mine-specific conditions may warrant more or less standby power capability.
Portable devices, such as hand-held radios, generally should provide sufficient power to facilitate evacuation and rescue following an accident. In many mining situations, at least 4 hours of operation in addition to the normal shift duration (12-hour minimum total duration) based on a 5/5/90 duty cycle generally should be adequate, but mine-specific conditions may warrant more or less capability.
The communication system generally should include a line-powered surface component with a standby power source to ensure continued operation in the event the line power is interrupted. The surface components of the communication system should be located at the communication facility required under 30 C.F.R. § 75.1600-1 where a person who is always on duty when persons are underground can receive incoming messages and respond immediately in the event of an emergency. The person should be trained in the operation of the communication system and knowledgeable of the mine’s ERP.
For survivability purposes, the post-accident communication system generally should provide redundant signal pathways to the surface component. Redundancy can be achieved by multiple systems installed in multiple entries, or one system with multiple pathways to the surface; provided that a failure in one system or pathway does not affect the other system or pathway. Redundancy means that the system can maintain communications with the surface when a single pathway is disrupted. Disruption can include major events in an entry or component failure. If system components must be installed in areas vulnerable to damage (such as in front of seals), protection against forces that could cause damage should be provided.
The equipment manufacturer generally should provide a maintenance schedule and checklist to the mine operator. The mine operator generally should establish and follow a procedure to provide communications during system or component failures in the event that an accident occurs before the failure can be corrected; check the standby power and functionality of the system and the un-tethered devices on a weekly basis as required by 30 C.F.R. § 75.512-2; and follow the manufacturer’s maintenance recommendations.
Electronic Tracking System
Approved electronic tracking systems are available. While operators and MSHA must consider mine-specific circumstances in determining an appropriate electronic tracking system, the PPL outlined features MSHA believes would provide the protection contemplated in the MINER Act in many underground coal mining environments. As noted, operators and others may propose alternative approaches or systems, and MSHA will exercise discretion in evaluating them.
By June 15, 2009, a plan must be submitted that provides for determining the location of persons underground using an electronic tracking system pursuant to 30 U.S.C. § 876(b)(2)(F)(ii).
While the required capabilities of a particular tracking system will depend on mine-specific circumstances, an effective electronic tracking system generally should be capable of determining:
• The location of miners on a working section including all intersections to within 200 feet.
• The location of miners in escapeways at intervals not exceeding 2,000 feet.
• The location of miners within 200 feet of strategic locations such as belt drives and transfer points, power centers, loading points, refuge alternatives, SCSR caches, and other areas deemed appropriate by MSHA (i.e., a reader is placed 200 feet or less from each strategic location); and
• The direction of travel at key junctions in escapeways.
Electronic tracking systems generally should be installed to prevent interference with blasting circuits and other electrical systems.
Similarly, as far as permissibility is concerned, the tracking system must be approved by MSHA under 30 C.F.R. part 23 and applicable policies.
Stationary components (infrastructure) should be capable of tracking persons underground during evacuation and rescue efforts, even upon loss of mine power. In many circumstances, the capacity to provide a minimum of 24 hours of continuous tracking operation after a power loss generally should be sufficient.
An individually-worn/carried tracking device (e.g., a tag) generally should provide a low power warning. To facilitate evacuation and rescue efforts, the individually-worn/carried tracking device generally should provide at least 4 hours of operation in addition to the normal shift duration (12-hour total minimum duration).
Tracking system components (readers) must be capable of tracking the maximum number of persons, including visitors, expected to be in a coverage area. To provide timely and relevant information, the tracking system generally should be capable of updating (refreshing) location data at least every 60 seconds.
The surface component of a tracking system should be located at the communication facility required under 30 C.F.R. § 75.1600-1 where a person is always on duty when miners are underground and should include a line-powered interface that can display the location of all miners underground. The person should be trained in the operation of the tracking system.
Similarly, the surface tracking component should be equipped with standby power to ensure continuous operation in the event the line power is interrupted. The tracking system interface should display the last known location of a miner when the tracking device is not communicating with the system. Each miner should be uniquely identified. Location data should be associated with a time stamp. Location data should be stored for two weeks so that it will be available for evacuation and rescue of persons underground, as well as for accident investigations.
Regarding survivability, if system components must be installed in areas vulnerable to damage (such as in front of seals), protection against forces that could cause damage should be provided. For example, protection could be provided by installing enclosures in recessed areas, around corners, or other areas that reduce potential for damage, or routing and protecting cables such that potential for damage is minimized. Data storage should not be impacted by interruption of the data link between underground and surface components.
The equipment manufacturer generally should provide a maintenance schedule and checklist to the mine operator. The mine operator generally should establish and follow a procedure to provide tracking during system or component failures in the event that an accident occurs before the failure can be corrected; check the standby power and functionality of the system and the devices worn by the miner on a weekly basis as required by 30 C.F.R. § 75.512-2; and follow the manufacturer’s maintenance recommendations.
This article was adapted from the December 2008 MSHA PPL on Communications & Tracking. The entire PPL may be accessed at http://www.msha.gov.