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S2 E4 Blog: Warehouse Containment & Drainage for Hazardous Materials
In today’s "safety by design" landscape, the storage and handling of hazardous materials requires specialized attention. Today, in Epsiode 4 of the "Warehouse Safety By Design" series we are covering "Warehouse Containment & Drainage for Hazardous Materials." Read on ...
Whether you're building a new warehouse or retrofitting an existing facility to store chemicals, creating a safe environment involves much more than just setting up shelves and organizing the space. The design of containment systems and drainage features plays a critical role in preventing catastrophic accidents, minimizing environmental damage, and ensuring compliance with industry standards.
In this blog, we’ll walk you through the key considerations for designing a warehouse for hazardous materials storage, focusing on containment and drainage. We'll also touch on related passive building design and automatic sprinkler system waterflow demand considerations, to ensure your warehouse not only meets regulatory requirements, but also safeguards your operations, employees, and surrounding community.
Why Warehouse Containment & Drainage for Hazardous Materials Matters
When a warehouse is designated for the storage of hazardous chemicals, there exist the risk spills, leaks, and, as with all warehousing, fire. Over the past decade, multiple large-scale losses involving hazardous materials have highlighted the need for rigorous design features that control these risks. Moreover, heightened public and regulatory attention, driven by significant environmental and cleanup costs, has placed more scrutiny on how these facilities are built and maintained.
Two critical elements of warehouse design for hazardous materials are containment and drainage. These features are essential for confining potential spills, leaks, and other hazardous situations, ensuring that materials do not spread uncontrollably and cause more harm to the environment or public health.
When designing a containment system, it's vital to focus on several areas, including the floor design, wall construction, and the type of drainage systems used to channel any hazardous materials safely.
1. Containment Floor Design
One of the first design choices you'll face is whether or not to use geotechnical membranes, or Visqueen-style plastic (with sealed seams), beneath the concrete slab. This is often determined by the soil conditions, the chemical properties of the materials stored, concrete design, and regulatory requirements. While geotechnical membranes can provide an added layer of protection, their design comes with a high cost as well as potential technical challenges, especially in regions with unstable or variable soil conditions. Such membranes can also impact the future state of the concrete floor slab.
Another key question is how "liquid-tight" the floor needs to be. For example, expansion joints and control joints in concrete slabs should be sealed to prevent leaks. A common question is whether you're designing for a practical, industry-standard “waterflow containment” solution using “waterstop construction” at floor joints (and where walls meet floor), or going beyond with an complex, high-level environmental design.
The balance between practicality and cost is notable. For most warehouses, a reasonable containment system should suffice, provided the building is equipped with effective fire detection and protection systems, as well as other passive and active controls, that can mitigate worst-case scenarios.
2. Containment and Fire Wall Design
The wall design of a hazardous materials warehouse should account not just for the containment of materials, but also, fire water as well as inherent building and wall structural concerns.
Firewalls, for example, are essential in preventing the spread of flames in case of a fire, and they need to be carefully integrated into the building’s overall design. These walls should be fire-rated and able to withstand both chemical spills and potential fires involving hazardous materials. Minimum wall fire ratings (and allowable areas”) are specified by the building and fire codes, and may be further influenced by the Authority Having Jurisdiction (“AHJ”), insurer, or property owner. There is also the issue as to whether a “maximum foreseeable loss” (“MFL”) type design should be considered. Such walls are designed to be free-standing in the event of roof collapse on either side of the MFL wall. Their design and use may also be a function of determining the acceptable area of loss (a risk management decision) in the event of a worst-case fire or exposure. FMGlobal (and their related standard) is an excellent resource in the area of MFL wall design.
Similarly, the roof construction plays a pivotal role in supporting a safe environment. It must be durable enough to support ventilation systems, snow loads, lighting equipment, and automatic sprinkler systems, in addition to withstanding the effects of fire (to allow ceiling and in-rack sprinklers to do their job). Where MFL walls are considered, special “noncombustible roof” considerations are applied to circumvent the transfer of fire over and beyond the MFL wall.
The Importance of Drainage Systems
"Warehouse Containment & Drainage for Hazardous Materials" is critical. But tell me more about "drainage systems!?"
Just as critical as “containment” is how fire protection water and hazardous materials are “drained” from the primary warehouse in the event of a large spill and fire condition. A well-designed drainage system ensures that exposures are safely re-directed to areas where they can be dealt with effectively.
1. Drainage Pathways and Secondary Containment
"Warehouse Containment & Drainage for Hazardous Materials" also means designing drainage systems that consider how water used in automatic sprinkler systems and how it will interact with the upstream (or downstream) containment area(s). Often, the volume of water that could be released during a fire is far more substantial than the amount of hazardous materials stored in the building or fire area. If containment is not properly designed to manage the anticipated waterflow volumes, the potential for widespread contamination increases.
Consider this example: In a 100,000-square-foot warehouse, a 1-inch containment height can hold approximately 62,000 gallons of water. If the containment height were increased to 3 inches, it could hold 186,000 gallons. These numbers become even more significant when accounting for the total waterflow anticipated during a worst-case fire, which could easily exceed the quantities anticipated by initial containment calculations.
Oftentimes, containment systems must therefore also be designed with the possibility of a secondary containment area in mind. In cases where water from fire suppression systems needs to be diverted to such secondary areas, a detailed engineering study must assess and determine how runoff can be safely channeled. This also means accounting for the gradients involved, pipe sizes, pipe and fittings design, and anticipated flow rates and pressures.
2. Stormwater Valve Closure Systems
In certain facilities, especially those storing chemicals that are sensitive to environmental exposure, an automatic stormwater valve closure feature may be necessary. Such features help prevent contaminated water from entering external stormwater systems, or seeping into the surrounding environment. The system automatically closes off stormwater drains when hazardous materials are released into the containment area, minimizing the risk of environmental damage. Closure of these valves/systems are often triggered automatically, such as upon a fire alarm or other emergency alarm system. They also may be set in a normally-closed position, depending upon the risks and materials involved.
Waterflow Duration and Containment Capacities
One crucial aspect of "Warehouse Containment & Drainage for Hazardous Materials" is understanding how long the containment system must hold hazardous materials or firefighting water. This is determined by waterflow duration, which refers to how long the firefighting system can pump water into the building.
For example, the required containment volume can be calculated based on the area involved and the gallons per minute (GPM) of water used in the fire suppression system. Let’s look at some typical scenarios for a 20,000-square-foot containment area:
As these calculations show, the volume of water involved during a fire can far exceed the hazardous materials themselves, which highlights the importance of considering these factors during the initial design phase.
The Role of Experts in Warehouse Design
Designing warehouse containment & drainage for hazardous materials means it’s crucial to involve specialized experts at every stage of the project. Structural engineers, fire protection consultants, environmental engineers, and other professionals will help ensure that the building meets all safety standards, is efficient, and complies with local and national regulations.
Besides engineers, it's also critical to stay updated with relevant building codes and fire safety standards such as the NFPA 30, Flammable and Combustible Liquids Code. and other recognized standards such as FMGlobal Data Sheet 7-83 and those put forwaqrd by governmental agencies, insurance carriers, and loss control professionals. One valuable resource for those designing chemical storage warehouses is the Guidelines for Safe Warehousing of Chemicals, published by the Center for Chemical Process Safety. While it’s a bit dated, the book remains an excellent starting point for understanding the nuances of safe chemical storage and the unique requirements for containment and drainage systems in hazardous materials warehouses.
Conclusion: Prioritize Safety, Containment, and Expert Involvement
Designing warehouse containment & drainage for hazardous materials is no small feat! It requires careful planning and collaboration with professionals who understand the intricacies of chemical storage, containment, fire protection, and drainage systems. From ensuring liquid-tight flooring or water-stop construction, to calculating the necessary containment heights/volumes based up anticipated waterflows or large-scale releases, every aspect of the design should be meticulously planned.
Remember, the safety of employees, the viability of future operation, and the well-being of employees, the public, and the environment are at stake. Be sure to pay attention to every detail, and take time to consult with experts to create a warehouse that not only meets regulatory standards, but also provides a safe and efficient working environment that will stand the test of time.
So, stay safe, stay informed, and make sure designing warehouse containment & drainage for hazardous materials is as robust as it can be for the hazards and risks involved!
