Environmental Science & Engineering - www.esemag.com - May 2004
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Pre-engineered storage buildings for environmental control of hazardous materials

By Paul Graham, P.E.
Safety Storage Inc.


Options for metal hazmat buildings (from left to right) include noncombustible steel buildings, 2- or 4-hour fire-rated systems, and custom-engineered buildings. Photos: Safety Storage Inc.

Pre-engineered and customized metal buildings designed for the storage, mixing, and processing of hazardous wastes and process materials have been available since the early 1980s. Before that time, hazardous materials were generally housed in “stick-built” structures within existing buildings. As governmental legislation began classifying and regulating these materials, preengineered buildings have allowed for better storage methods in well-defined and monitored areas.

Pre-engineered hazardous materials (hazmat) metal buildings offer good environmental controls. They offer wide flexibility in their deployment and use, and are available in non-flammable, fire-rated and explosion-rated versions. They serve specific location and use purposes.

Non-flammable buildings are fabricated entirely from steel. They offer good storage of hazardous material in remote locations away from other structures. If additional protection of adjacent structures or personnel is necessary, fire-rated hazmat buildings offer excellent environmental, building and employee protection.

Finally, explosion-rated hazmat buildings vent dangerous overpressures by employing explosion relief panels.

Important roles Pre-engineered, customized hazmat buildings come complete with wall, floor and sump, and ceiling systems, and are intended to be installed on a hard, level surface capable of supporting their weight.

Designed for safety Most hazardous material buildings require the use of Nationally Recognized Test Lab-listed Hazardous Location electrical components. Optional equipment includes interior partitions, sump separation, exhaust fans, air vents, heaters, air conditioners, and fire-suppression systems.

These buildings are designed by manufacturers to meet the high-end requirements of the model safety codes. These include the model building codes (NBC, ABC), fire codes (NFC, AFC), energy codes (MNEC), mechanical codes, plumbing codes (NPC), handicapped codes, and electrical codes (CEC). Since manufacturers use standardized designs and construction techniques meeting the most stringent building requirements for many jurisdictions, many customers receive buildings manufactured to exceed their own local codes. Leading hazmat building manufacturers offer warranties ensuring that all local and provincial permitting licenses will be secured prior to building installation.

Most pre-engineered buildings have passed building standards approved by the provinces or their designated thirdparty agencies. Provincial engineers (or their appointed agencies) review the building’s features, audit and review the manufacturer’s quality-control system for manufacturing consistency, and confirm the proper use of listed components tested by nationally recognized testing laboratories.

Material-handling and storage features Most pre-engineered hazmat buildings offer access by forklift or hand truck. Standard buildings generally come with one 1.5-metre (60-inch) width double door, with one active self-closing door for personnel access and exit and one inactive door for bringing pallets or totes into the building. Buildings larger than 18.6 square metres (200 square feet) usually require two exits for safe egress.

Most of these facilities hold single or multiple layers of palletized materials. They also offer custom shelving to hold containers of numerous shapes and sizes.

Construction considerations Like any other building, pre-engineered hazmat facilities must meet all applicable federal, provincial, and/or local building codes. Many codes account for the environmental conditions of the community, such as meeting minimum snow loads (typically 950 kg per square metre or 40 pounds per square foot), wind speeds (typically 177 km per hour or 110 miles per hour), or required seismic forces. Typically, these buildings offer allmetal sumps that easily resist earthquake stresses.

Important placement considerations A building’s construction type (i.e., noncombustible or fire-rated for 2- or 4-hour fire resistance) is based on where the hazmat building is located in relation to other buildings susceptible to fire. The temperature within the building, the materials being contained, and the intended use (storage, mixing, or dispensing) dictate the fire- or explosion-resistant requirements of the facility. Most model building codes (NBC, etc.) require a 50-foot setback of the hazmat building from other buildings in the event of an explosion.

a) Building interiors and finishes - A well-planned building interior can increase the functionality of the storage area. To increase available storage space, hazmat buildings can be designed with shelving systems, racks, or platforms. Versatility can be enhanced with the addition of work-tables, recycling sinks, chemical fume hoods, and related equipment, converting a storage space into an area that can also be used for dispensing and mixing.

b) Security - To provide security from unauthorized access, these facilities use solid construction techniques and are equipped with lockable doors to control entry. Door locks must have interior release mechanisms or panic hardware to avoid accidental entrapment. Security nightlights and door alarms are also good investments.

c) Secondary containment - Some pre-engineered hazmat buildings offer a secondary containment sump that contains any potential leakage or spillage of liquid or solid hazardous material. Many environmental regulations require the secondary containment capacity to equal 10% of the total amount stored and to contain 100% of the largest container stored. Some local jurisdictions may have more stringent requirements and require capacity for 20 minutes of fireprotection water plus contents of the single largest container.

Sump floor and wall construction should be of heavy-gauge impermeable material that is not easily damaged, such as 12-gauge hot-rolled steel, with galvanized metal grating used for the floor. For additional protection, consider the use of sump liners or coatings that prevent damage to the containment area from exposure to corrosive materials. The secondary containment sump should be easily accessible by lifting the floor decking to allow for periodic inspection and clean-up.

d) Heating, ventilation, and cooling - Because many chemicals are temperature- sensitive, heating and cooling systems can extend the shelf life of the hazardous materials inventory and allow economical purchases of materials during off-peak seasons. Therefore, building insulation (either fiberglass batts or rigid foam) is a good investment that will reduce expenditures on annual energy consumption.

Enclosed spaces should be properly ventilated, by natural or mechanical means, to reduce the concentration of hazardous vapours and dust, with a minimum of 0.32 cubic metres of exhaust ventilation provided per square metre of storage space (1 cubic foot per square foot). An adequate number of air intakes should be located within 30.5 cm (12 inches) of the floor (measured from the sump floor surface, not the floor decking above the sump) and the air exhaust vents should be located high on an opposite wall. Where dispensing and mixing operations occur, mechanical ventilation systems are necessary.

e) Fire protection - If storing flammable materials, the storage area should be equipped with an automatic fire extinguishing system. Additional fire protection can be obtained by specifying 2- or 4-hour fire-rated wall construction, depending on local building codes and proximity to other buildings and structures and property lines. Usually designed with a combination of metal studs and panels, plus internal layers of gypsum board, fire-rated buildings significantly reduce the effects of heat conduction and material failure that result from intense fires. They can have either bi-directional ratings (the fire source can be within or outside the building and still protect the opposite side from heat effects) or unidirectional ratings (the construction protects only the outside of the building from the effects of a fire inside).

f) Explosion resistance - If explosive conditions are possible, the building construction method must reduce the devastating side effects of excessive pressures from explosions. All main walls are designed to withstand high pressures, typically 2,375 kg per square metre (100 pounds per square foot). These walls contain specially designed lower-pressure safety panels that physically disconnect from the main building wall during the explosion, typically at 475 kg per square metre (20 pounds per square foot). Thus the force of the explosion is released through the panels in a controlled manner. The panels are made from 18-gauge galvanealed steel and insulated with rigid foam insulation if HVAC is required.

For more information contact: paulg@safetystorage.com.

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