4/17/25
In the matter of PETITION FOR MODIFICATION
South 32 Hermosa Inc.
Hermosa Mine
I.D. No. 02-03398 Docket No. M-2024-003-M
PROPOSED DECISION AND ORDER
On August 1, 2024, South 32 Hermosa Inc filed a petition seeking modification of the application of 30 Code of Federal Regulations (30 C.F.R.) § 57.11052(d) at its Hermosa Mine, Mine I.D. No. 02-003398, in Santa Cruz County, Arizona. Specifically, the Petitioner requests a modification to allow the use of refuge chambers designed to sustain miners for up to 72 hours, using breathable air provided via compressed oxygen or compressed air cylinders and water bottles physically contained within each refuge chamber as an alternative to providing compressed air lines and water lines directly to the refuge areas from the surface as required by the standard. Petitioner alleges that the proposed alternative method in the petition will, at all times, guarantee no less than the same measure of protection afforded to the miners by the standard. Petitioner also alleges that installing air lines and water lines from the surface would result in a diminution of safety to the miners.
30 Code of Federal Regulations (C.F.R.) § 57.11052(d) states, in relevant part:
Refuge areas shall be –
(d) provided with compressed air lines, waterlines, suitable handtools, and stopping materials.
The Mine Safety and Health Administration (MSHA) investigated the merits of the petition and filed a written report of their findings with the Administrator for Mine Safety and Health Enforcement. After a careful review of the entire record, including the petition and MSHA's investigative report, the Administrator for Mine Safety and Health Enforcement issues this Proposed Decision and Order.
FINDINGS OF FACT AND CONCLUSIONS OF LAW
On January 28 through 29, 2025, MSHA investigators traveled to the Hermosa Mine to investigate the Petitioner’s claims. The Investigation team determined the following:
• The Hermosa Mine is currently being developed and is not in production status. The mine is a green field project and will be an underground open stope mine producing lead, zinc, and Manganese. The ore zones will be accessed through both a direct decline and a 25’ diameter vertical shaft. The mine plans to operate 24 hours per day, 7 days per week, and employ between 400 and 500 miners.
• Currently, all exploration activities in the decline and shafts are executed by contractors. There are two contract mining companies currently on site, Redpath USA Corporation (Contractor ID No. R83) and DMC Mining Services (Contractor ID No. WJ6).
• At the time of investigation, the decline was mined in approximately 630 feet from the Clark Portal Entry. The shaft is sunk to an approximate depth of 190 feet.
• All potable water is currently transported into the facility. No connection to the mainline exists. The existing water lines used during development are not part of the future mine’s design.
• The Hermosa mine site has a functioning water treatment facility that treats their water before it is released from the mine property.
• Compressed air lines were not observed in use at the time of the investigation. The operator states that compressed air lines used during the development will not be part of the mine design, as all haul truck and LHD equipment will be electric.
• There were no 72-hour MineARC Refuge Chambers on site at the time of the investigation. A twelve person MineARC (Model #MS-SD2-12-SIV-36) was observed at the Clark Portal, with a 36-hour duration rating. This unit is expected to be retrofitted into a 72-hour unit by the manufacturer once the Petition is approved. This unit would be placed in the decline when development has proceeded to the point it will be required.
• The operator will also utilize built in place refuge chambers in the future development of the mine. These built in place refuge chambers will be provided with the same life support features such as breathable air and bottled water as the portable MineARC units but will be built utilizing bulkhead walls as a seal.
South 32 Hermosa Inc’s Hermosa Mine is currently in non-producing status, but MSHA understands that the operator plans to begin partial or full production in the future.
Petitioner is requesting a modification of § 57.11052(d) to not use compressed air lines and water lines from the surface as the means of providing air and water for the underground refuge chambers. Petitioner requests approval to use various MineARC Refuge Chambers with occupancies of 4, 8, 12, 16, and 20 miners. The specific model and capacity will be selected dependent on the number of mine workers in each area of the underground mine. Refuge chambers will be strategically located underground based on the amount of personnel underground at any one time, including additional capacity for visitors, geologists, engineers, and management, and a maximum travel distance of 2,500 feet to the nearest refuge chamber. The requested MineARC Refuge Chamber models will all be equipped with a minimum of 72-hours of onboard breathable air supply and 2.25 quarts of water per person per day.
Petitioner asserts that the proposed alternative method will guarantee at all times no less than the same measure of protection as that afforded by the existing standard.
In addition, Petitioner states that waterlines in the mine would not be potable and therefore not drinkable. Petitioner further states that the compressor feeding the compressed air lines would need to be located on the surface, which is more than 2,500 vertical feet from the refuge chamber. Petitioner claims “over this distance there is substantial pressure loss, making it difficult to provide 12.5 cubic feet per minute of breathable air as required by 30 C.F.R. § 7.506(c).”
The existing water lines used during development of the Hermosa Mine are not part of the future mine’s design and all potable water is currently transported into the facility. Additionally, compressed air lines were not observed in use at the time of the investigation and will not be part of the Hermosa Mine’s development or final mine design. Therefore, petitioner’s requested modification of § 57.11052(d) to not use compressed air lines and water lines from the surface as the means of providing air and water for the underground refuge chambers is found to guarantee no less than the same measure of protection afforded to the miners by the standard.
ORDER
Wherefore, pursuant to the authority delegated by the Secretary of Labor to the Administrator for Mine Safety and Health Enforcement and pursuant to Section 101(c) of the Federal Mine Safety and Health Act of 1977, 30 U.S.C. § 811(c), it is ordered that South 32 Hermosa Inc’s Petition for Modification of 30 C.F.R. § 57.11052(d) at the Hermosa Mine is hereby:
GRANTED, conditioned upon compliance with the following requirements.
1. Each Refuge Chamber shall include all systems and provisions necessary to support the maximum designated occupancy of miners safely for at least 72 hours. This includes the backup battery, air conditioning system, interior lighting sufficient to complete tasks, and provisions necessary for the maintenance of miners.
2. The Refuge Chambers available in each area shall accommodate the maximum number of persons expected to be working in that area at any time.
3. Written instructions for the use and maintenance/repair of each Refuge Chamber, including all associated support systems, shall be provided in each unit and at the mine office.
4. Provisions (food and water) sufficient for the maximum designated occupancy. Components and provisions must be stored in containers that are airtight, waterproof, and rodent proof.
a. Water = 2.25 quarts per person per day; shelf life determined by manufacturer of the bottled water.
b. Food = 2,000 calories of food per person per day; shelf life determined by manufacturer of the food.
5. The exterior of each Refuge Chamber must be conspicuously labeled with the maximum-designated occupancy, and expiration dates of the food, water, CO2 gas scrubbing chemicals, and other necessary perishable provisions to minimize the need for entry into the refuge when conducting examinations.
6. The exterior of each Refuge Chamber must be made of flame-resistant material. Any inflatable portion of the unit, if applicable, must also be flame resistant and housed in a sealed metallic structure prior to deployment in order to protect against damage that could be incurred during storage or transport.
7. Repair materials shall be provided per manufacturer recommendations within each Refuge Chamber in case the unit (which provides occupants a controlled and isolated atmosphere) is damaged during use.
8. Each Refuge Chamber shall be examined immediately after every move to a new location to ensure the unit has not been damaged. Any identified damage shall be repaired immediately.
9. The communication system normally used by the mine (or other means of emergency communication that can be used from within an occupied Refuge Chamber) shall be provided and maintained at each unit. If batteries are necessary to power communication equipment in the unit, a quantity of batteries sufficient to power the communication equipment for the rated duration of the refuge at a 5-5-90 duty cycle shall be stored and maintained with the refuge. (The 5-5-90 duty cycle means that the batteries will support 5 percent of the rated duration in transmit mode, 5 percent of the rated duration in receive mode, and 90 percent of the rated duration in idle mode.)
10. Each Refuge Chamber must be provided with a multipurpose dry chemical type fire extinguisher containing a nominal weight of 5 pounds of dry powder and enough expellant to apply the powder, or a foam-producing type containing at least 2 1⁄2 gallons of foam-producing liquids and enough expellant to supply the foam. Only fire extinguishers approved by the Underwriters Laboratories, Inc., or Factory Mutual Research Corp., carrying appropriate labels as to type and purpose shall be used. The extinguisher shall have a 2A 10 BC or higher rating.
11. Each Refuge Chamber shall be equipped with a means to indicate unauthorized entry or tampering (i.e., a tamper-evident seal). Tamper-evident seals may be broken for the purpose of examining or inspecting the refuge, but a method of tracking tamper-evident seals, such as recording the current unique seal number, must be implemented.
12. Each Refuge Chamber must provide a means to contain and dispose of human waste. The method provided must be sufficient to accommodate the maximum designated occupancy for the rated duration of the chamber.
13. Each Refuge Chamber shall be able to maintain an apparent temperature not to exceed 95 degrees Fahrenheit for the maximum designated occupancy and rated duration of such unit.
14. Each Refuge Chamber shall be conspicuously identified with a sign or marker as follows:
a. A sign or marker made of a reflective material with the word “REFUGE'' shall be posted conspicuously at each ERCP.
b. Directional signs made of a reflective material shall be posted leading to each refuge chamber’s location.
15. Breathable Air and Removal of Harmful Gases:
a. Equipment designed to supply and control the flow of oxygen, remove carbon dioxide, and monitor the oxygen and carbon dioxide level of the ambient air in the refuge chamber must be provided with each unit. Instructions for use of these systems and equipment to maintain oxygen levels between 18.5 percent and 23 percent and carbon dioxide levels below 1.0 percent, with excursions not to exceed 2.5 percent, over the rated duration inside the unit when occupied also must be provided.
b. A supply of no less than 1.32 cubic feet of oxygen per hour per person for the rated duration of the refuge chamber at full occupancy shall be provided in/for each unit. Breathable air supplied by compressed air from blowers, fans, or compressors may be provided (in addition to the oxygen cylinders), but must demonstrate a minimum flow rate of 12.5 cubic feet per minute of breathable air per person.
c. One-way pressure relief valves must be provided to each unit to limit the interior internal atmosphere pressure, as recommended by the manufacturer.
d. Any breathable air supplied by blowers, fans, or compressors shall be supplied through protected, metallic piping to guard against damage from mobile equipment or fire.
e. Any breathable air supplied by blowers, fans, or compressors must be at least the quality of grade D breathable air as described in American National Standards Institute/Compressed Gas Association (ANSI/CGA) specification G-7.1.
f. If oxygen candles are provided as a redundant source of oxygen, a rigid fixture to safely contain the candle and guard miners from burns must also be provided.
g. Oxygen cylinders shall be stored in a safe manner and in compliance with MSHA standards 30 C.F.R. § 57.16005 and § 57.16006, away from flammable and combustible materials.
h. The condition of the oxygen cylinders shall be inspected, and pressures recorded, at least semi-annually. Maintenance of these oxygen cylinders will be conducted per the manufacturer’s recommendations.
i. A manifold system for regulating the flow of oxygen and monitoring the available reserve shall be provided with the supplies for each unit.
j. An extra oxygen regulator and flow control device shall be provided with each unit.
k. Tools and any repair parts recommended by the manufacturer for the compressed oxygen system, along with any accompanying instructions, shall be kept within each unit. This includes extra flow valves, wrenches, emergency sealing tape or adhesive patches, and duct tape.
l. Sufficient scrubbing chemicals shall be provided to remove carbon dioxide at the rate of 1.08 cubic feet per person per hour for the rated duration and maximum rated occupancy of each unit.
m. The chemical(s) used to remove carbon dioxide must be provided, along with all materials and parts needed for deployment. Scrubbing chemicals shall be contained such that when stored or used, they cannot come in contact with persons and cannot release airborne particles inside the refuge chamber. The manufacturer’s instructions on the deployment and use of the chemicals and the curtains or cartridges shall be provided and kept within the unit.
n. An airlock and on-board purge air system shall be provided in each refuge chamber. The airlock must be purged with breathable air before miners enter the main living area of the unit, per manufacturer’s instructions.
16. Air Monitoring
a. Each unit must be equipped with an air monitoring device capable of measuring the concentration of oxygen, carbon dioxide, and carbon monoxide. The detection equipment needs to be functional for the rated duration of each unit.
b. The gas detection equipment for each refuge chamber shall be examined and maintained as recommended by the gas detection equipment manufacturer. Consideration should be given to sensor and battery maintenance and calibration frequency.
c. Each refuge chamber, and associated air monitoring devices, will be equipped with a means to measure both interior and exterior gas concentrations.
d. The measurement of carbon dioxide must be done with an infra-red type sensor.
17. Examinations
a. Workplace Examinations performed in the area where the refuge chamber is located shall include a visual examination of the unit’s exterior for damage and tampering.
b. The mine operator shall examine each refuge chamber at least once every six months to ensure that the unit is in working order, ensure batteries are charged and are not expired, confirm the condition and quantity of stored water and food, ensure the effective operation of the air-monitor, and confirm condition and pressure readings of the compressed gas cylinders.
18. Training
a. Applicable revisions or appropriate changes to the MSHA 30 C.F.R. Part 48 training plan regarding the conditions set forth in this petition shall be submitted to the MSHA District Manager for revision and approval prior to implementation of the training plan by the Petitioner.
b. Training on the proper use of the refuge chamber will be provided, at least once every six months, to those miners who might possibly transport or use them. Training must include all aspects of the use of the specific units employed at the mine, including the hazards associated with compressed oxygen cylinders, the carbon dioxide scrubbing process, the communications systems, and use of the gas detector(s) to monitor concentrations of carbon dioxide, carbon monoxide, oxygen, and other harmful gases specific to the mine.
Any party to this action desiring a hearing on this matter must file in accordance with 30 C.F.R. § 44.14 within 30 days. The request for hearing must be filed with the Administrator for Mine Safety and Health Enforcement, 200 Constitution Ave NW, Suite 3522, Washington, DC 20210.
If a hearing is requested, the request shall contain a concise summary of position on the issues of fact or law desired to be raised by the party requesting the hearing, including specific objections to the proposed decision. A party other than the Petitioner who has requested a hearing may also comment upon all issues of fact or law presented in the petition and any party to this action requesting a hearing may indicate a desired hearing site.
If no request for a hearing is filed within 30 days after service thereof, the Decision and Order will become final and must be posted by the operator on the bulletin board at the mine.
Dustan W. Crelly
Acting Administrator for
Mine Safety and Health Enforcement
Certificate of Service
I hereby certify that a copy of this proposed decision was served personally or mailed, postage paid, or provided by other electronic means this 17th day of April, 2025 to
Al Wardle
Hermosa Project
Health, Safety, & Security Manager
Al.Wardle@South32.net
1860 E River Road, Suite 200
Tucson, Arizona 85718
Alexander Bullinger
General Engineer, MSHA Enforcement