Refuge stations

Mine refuge stations have been around since the 1930s. After the Hollinger mine fire claimed 39 lives, recommendations were made to include them in the Mining Act. Over the years there have been changes to the requirements of refuge stations, but the underlying idea has stayed the same. The purpose of a refuge station is to keep employees safe while unforeseeable hazards exist in the mine . Over the years the regulations for the stations have been changed in order to make sure all workers can be kept safe for a pre-determined amount of time. A refuge station is normally a small room cut into the rock with a solid man-made wall with a door in it. Refuge stations are also often used as lunch rooms or meeting rooms. . Figure 1 shows a typical refuge station found in an underground mine in Ontario.

Figure 1

Types of Refuge Stations

Refuge stations are built in a variety of different ways within mines. Because each mine is different, so is the refuge station. Permanent stations are created by making rooms out of the host rock. Portable stations are made to move throughout the mine to where they are required. Both have different safety requirements in Canada and different pros and cons.

Permanent Stations

A permanent station can house more people for a longer time but may be more difficult to access as there are normally not refuge stations on every level. Permanent Stations may cost more to build than a portable stations because a portable station does not need cement barriers or rock support .

Portable Stations

A portable station can be moved to areas with higher activity to provide a safe haven for the workers there. In general, if the production level of a mine has a long life, a permanent station is usually put in. This is why there are a large number of portable stations used in coal mining . Figure 2 shows a portable refuge station made by Strata Safety.  
. According to North Fringe Resources Inc. a portable refuge station is more reliable and safer. They require less room or area for placement as well.

Equipment and Required Supplies

Human Support Systems

An air supply must be present in order to keep the CO₂ and other poisonous gas levels in the air down and keep the oxygen content at the required level. One of the primary concerns with the air supply during a mine disaster is the oxygen content present in the air. Oxygen depletion can lead to the mine personel rapidly sucombing if levels are not high enough.  Figure 3 shows how fast oxygen is depleted through various activities.

Figure 3

Typically a man in a confined space requires one cubic metre of air an hour to survive .

Air can be provided or conditioned in a variety of ways, including: permanent compressed airlines, Rimer Alco North America System, or portable stations with cascade air cylinders. The choice of what air supply to use depends on a variety of factors. These include: number of occupants, duration of stay, size of the station, permeability of the walls, temperature, and humidity. Figure 4 shows a typical air supply system. 

In the costing example below, sizing for an air cylinder air supply is shown. 

Water lines must be installed to supply potable water to the inside of the station. If no line is avilable, potable water containers can be used to store the water inside the station.The stored water should be inspected and changed regularly. There should be drainage for waste water as well. The drain should be designed to make sure water can leave but no gases can enter the station.

Figure 4

There must be a communication system installed to have contact with the surface for those in the refuge station. A list of emergency phone numbers must also be readily available and should be posted at each phone.

There must be lighting within the refuge station. This lighting must be able to run without the normal electrical system.

There must be seating for all those in the refuge station. Sitting reduces energy expendature by at least 20 percent

Emergency equipment and first aid equipment

• first aid kit (stocked with legislated requirements) 
• a basket stretcher and backboard
• blankets (2)
• fire extinguisher mounted on inside wall (at least 10 lb)
• one, 12 inch crescent wrench
• hand soap
• toilet facilities and toilet paper
• writting material 
• smoke tubes for checking airflow/leaks
• A 10lb Dry chemical fire extinguisher
• fire proofing putty to seal off the doors to the station. Enough material should be available to seal the door and other openings in the walls.

Regulations

Design Requirements

Both the construction and location of a refuge station is of the upmost importance. Construction regulations have to be met 100 percent of the time in order to provide a safe location in the case of an emergency in the mine. The refuge stations have to be located at various locations around the mine, so that no worker is ever more than 500 meters from either a refuge station or a mine exit . Air supply and air containment is critical in the refuge station construction. The station must be able to be sealed to prevent the entry of gases as well as keep the oxygen level in the station high. This means that the station must be large enough to contain the required air supply or be equipped with a means of supplying the required air to sustain the lives of the maximum number of mine workers intended to be sheltered there. It must also have at least two doors that can function as an airlock. If the station is a portable one, it must contain air for all sheltered workers for up to 8 hours . A permanent station must contain air for all sheltered workers for up to 24 hours . The refuge station must be constructed in competent, non- combustible rock. In a coal mine, it must be constructed of competent, combustible rock that may be coal, if there is a non-combustible sealed barrier between the coal and occupied space. The air lines or water lines must also be made of non-combustible material.. All explosives must be at least 60m meters from a refuge station .

When the refuge station is constructed it must be made from material that is fire resistant for at least one hour. 

Procedure Regulations

The mine manager must ensure that procedures are prepared for using a refuge station during an emergency that include all of the following:
(a) instructions for the conduct of people in the refuge station
(b) instructions for entering the refuge station in a manner that protects the health and safety of persons sheltered inside the refuge station.
The mine manager must also designate a person to inspect and re-supply the refuge stations. These inspections are to be completed at least once per month.

Documentation Requirements

If a refuge station is not fully equipped or if documents are not kept up to date lives are put at risk. This is why there have been steps taken and regulations put in place for the documentation of what the station contains and who has inspected it. These regulations ensure that the mine will know if the station is fit or not fit for use. The documentation requirements for a refuge station are given below:

• A proper emergency procedure for the refuge station must be posted inside the station as well as the mine's regular emergency procedures
• Level drawings/maps should be available inside the refuge stations showing ventilation flows, escape-ways and other pertinent information about the area
• An inventory list of emergency equipment and supplies should be posed inside the refuge station for reference
• A checklist for inspections should be developed with people designated responsible for completing the checklist to ensure supplies and conditions are maintained 

 Costing Example- Kidd Mine, Timmins ON 

The following costing information was found using the Mining Cost Services handbook (reference:  )

For this costing example, assume there are at most 50 workers on the production and surrounding levels that will require the use of the refuge station at any time. For reference, the production level at Kidd Mine in Ontario is relatively small at around 400-800 m from one end to the other. This means that placing the refuge station in the middle of the level will fulfill the need to have the station within 500 m of any worker.

In order to provide the highest safety for the workers in case of seismic activity and other failure causing events the roof and walls must have shot-crete, high cable bolt density, rock bolts, and meshing. Each provides a unique form of support to the rock. The costs of each type of support is given below:
Shot-crete cost: $64.58/m²
Meshing cost: $3.01/m²
Rock bolts: $9.22/m rock bolt
Cable bolts: $12/cable bolts + $0.5/m = $13.5/cable bolt (1.5 m)

For a 50 person refuge station, by law it must be minimum of 390 m³, but a size of 400 m³ will be assumed to be appropriate for this example. This will yield 320 m² of surface to cover with bolts, mesh, and shotcrete. Using Figure 5, the cable density will have to be 0.34 bolts/m² if the excavation is going to stay in the "Safe" zone of the graph. This means the refuge station needs 109 bolts. So the mine will use cable bolts and rock bolts. This is because rock bolts and cable bolts yield in different ways and provide different support to the rock surface.

Figure 5.jpg

The mine will buy 109 rock bolts and 109 cable bolts. The cost of these supplies is given below:
• Rock bolts: 109 at $9.22/bolt = $1004.98
• Mesh: 320 m² at $3.01/m² = $963.20
• Cable bolts: 109 at $13.50/bolt = $1471.50
• Shotcrete: 320m² at $64.58 m² = $20 665.60
The total cost of support is $24 105.28

Using the same scenario, the sizing for pressurized air tanks can also be found. Air tanks would normally not be used in a permanent station unless the air lines could not be relied on. So for this example assume there is a need for air tanks within a permanent station. The total air supply needed is 218 ft³ per person. Jumbo cylinders contain 300 ft³ of free air. This means the required amount is 218*50 = 10900 ft³ of free air, this will require 37 jumbo air cylinders in the refuge station. In a real mining situation there would be air supply from other sources than from the cylinders. Supplying a refuge station with 37 jumbo cylinders is not a viable solution to air supply and would be both extremely expensive and would take up too much space.  

The cost of the excavation can be calculated as follows:

The size of the excavation for the refuge station is 4m x 10m x 10m. The face is 40m². The cost of the face and the advance of such a face is $1177/15.4m²*m. 

'Cost of excavation = $1177/15.4m³ * 40m² * 10m = $30 571.43