Our Underground or Above Ground Bunkers are individually designed to our client’s protection program and long-term survivability requirements. Although the designs and systems are principally determined for nuclear weapons, it can be stated that a well built nuclear bunker also offers good protection against CBRE (Chemical, Biological, Radiological and Explosive) weapons and natural disasters. A Hardened Structures Underground Bunker can be designed and constructed in most locations be it rural, suburban or inner city.
Underground bunkers are advantageous for several reasons; they provide the added protection of being below the surface thus escaping a major portion of the effects from blasts and radiation, they can be pre-stocked with provisions to sustain their occupants for several months and, most important, they can be located connected to, or adjacent to, a client’s primary residence, thus allowing for quick evacuation.
The bunkers can be designed for either Single Use or Multi Use. A Single Use bunker is used only in case of an emergency and is a stand-alone design. The advantage with the Single Use is that it is not required to provide normal every day accommodations for people it may be readily accepted by the local building authority having jurisdiction because it is a special use.
A Multi Use bunker can be used for other purposes (i.e.; store rooms, wine cellars, etc.,) and this ability is sometimes more appealing to our clients. However, it must then be designed to accommodate everyday ingress/egress and building code requirements.
Perhaps the most important element in designing an underground bunker is its location or siting. Although the threat of damage from CBRE (chemical, biological, radiological and explosive) events may be the predominant focus of the evaluation for the bunker location, additional threats may exist from forced entry, tornado, hurricane, flood and seismic events, therefore the evaluation should assess the entire range of threats to the site. It is for this reason that Hardened Structures employs a Multi-Hazard Engineering methodology.
The position of the underground bunker must satisfy the structural requirements from the shelter standpoint along with the evacuation criteria of the client and the protection programming of the mechanical systems. The immediate location and easy accessibility of a bunker has a significant bearing on its life saving ability during a crisis. Therefore, we recommend that all potential users should be able to reach the bunker within 5 minutes, and the bunker door should be secured within 10 minutes.
Occupancy duration (also known as the button-up time) is the length of time that people will be in the bunker with the doors closed ensconced in a protective environment. This time period can last from a few hours to several days. If the occupancy duration of a bunker is less than 24 hours then sleeping areas are typically not required and the occupant load will generally be 20 square feet/person. If the occupancy duration is greater than 24 hours sleeping areas should be incorporated at the rate of 60 square feet/person utilizing single beds or 30 square feet/person using bunk beds.
The total square footage of an underground bunker is determined based on the following:
- Number of persons
- Occupancy duration
- Class of protection
- Storage requirements
- The Client’s particular life sustaining/quality requirements
The duration of occupancy of an underground bunker will vary depending on the intended event for which the bunker has been designed. Protection levels, occupancy duration and specific Client storage/survivability criteria are the most important factors that influence the design process.