Greater utilization of underground construction is growing in popularity as a strategy to increase available commercial and infrastructure space. A few noteworthy site preparation activities and guidelines are summarized and described for tunnels, utilities, and related projects.
Even Mushrooms Require an Education
Underground construction projects present some of the most challenging, difficult, and dangerous working environments. These projects will usually involve structural engineering expertise and include tunnels, chambers, deep trenches, shafts, pipelines, and bunkers. Mines, as one of the oldest forms of construction beneath the earth, are so complex they need to be addressed separately but many of the same issues apply. Along with the usual difficulties and hazards associated with construction such as heavy objects, power tools, and falling, there may also be concerns with air quality and quantity, provision for adequate egress, lack of sufficient lighting, hazardous vapor concentrations, geological stability, and flooding.
Training to Work in Underground Construction
A quick review of the OSHA guidance on suggested training for underground construction workers produces the following list:
○ Air monitoring and ventilation
○ Illumination
○ Communications
○ Flood control
○ Personal protective equipment
○ Emergency procedures, including evacuation plans
○ Check-in/check-out procedures
○ Explosives
○ Fire prevention and protection
○ Mechanical equipment
And this list only covers general training requirements. Site specific project conditions may necessitate additional training topics such as electrical hazards, flammable liquids and gases, shoring, portal supports, and other unique concerns.
It’s Not A Picnic, So Who Invited The Ants?
Communication, Emergency Rescue Equipment, And Supplies
After appropriately trained personnel are onsite, the project is ready to begin. While work is progressing, at least one responsible, on duty person must be designated for purposes of maintaining an accurate below ground head count and to summon help in an emergency. Consequently, voice communication must be maintained between the surface and underground crew. If out of earshot then some form of powered communication must be present and working. One or more five-person rescue teams must be onsite or within a thirty minute response time for every 25 underground personnel. These teams may be trained employees or consist of local rescue service personnel. In either case, rescue teams members must be trained in appropriate underground emergency response procedures such as fire-fighting equipment and self contained breathing apparatus.
Equipment, tools, and supplies allowed underground also create challenges. Gasoline in any form is prohibited, as are internal combustion engines other than diesel. Diesel fuel and other petroleum products such as greases and oils require storage in sealed containers located in designated fire-resistant areas, clear of vertical shafts and steep passageways. Hydraulic fluids must be rated fire resistant, unless the equipment in use is protected by adequate fire suppression systems or extinguishers. Welding gases and oxygen are only permitted in quantities that provide enough supply for a 24 hour period. A portable hand lamp or cap lamp must be provided for every employee, unless adequate lighting is provided for escape during a power outage or other emergency. In areas that may trap personnel by the presence of smoke, gas, or other air quality concerns, NIOSH approved self-rescuers must be provided. And so on. Needless to say, supplying a substantial underground project can create more than a few logistical headaches.
The Future Looks Bright, Even Underground
And all this preparation happens before a single work hour is spent underground. But greater utilization of underground spaces has become an increasingly popular strategy for commercial and infrastructure construction. An estimated 1300 miles of tunnel construction is slated for the Trans European road network by 2030, for example. Earth berm buildings, underground utilities, storage facilities, pipelines, and other projects continue to generate interest in construction below ground. Continued technological innovation in underground engineering and materials will lead to better risk management and reduced costs. All of which will further drive construction growth in this area, so being a mushroom may become a more attractive occupation after all.
