Cities under one roof
The larger and more complex facilities become, the more difficult it is to coordinate all required fire protection aspects and create a structure that provides a holistic approach to fire protection. Are resort hotel/casinos on the Las Vegas strip nothing more than big buildings? These facilities include a substantial list of amenities intended to keep occupants from wandering elsewhere.
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The larger and more complex facilities become, the more difficult it is to coordinate all required fire protection aspects and create a structure that provides a holistic approach to fire protection.
Are resort hotel/casinos on the Las Vegas strip nothing more than big buildings?
These facilities include a substantial list of amenities intended to keep occupants from wandering elsewhere. They provide accommodations for residential, dining, parking, and recreation; convention, meeting, and ballroom areas; showrooms; and, of course, gaming. The dining options range from well-known buffets and coffee shops to signature restaurants; some are ranked world-class. The back-of-house areas include warehouses, woodworking, employee dining, offices, housekeeping, and virtually everything needed to run these mega-structures. Casinos on the Las Vegas strip are much more than big buildings; they are essentially cities under one roof.
The fire protection aspects incorporated into these mega-resorts include the familiar and a substantial amount of unique aspects that many design professionals would never imagine. The familiar aspects include:
Kitchen hood suppression systems
Fire detection and alarm systems
Emergency responder access
Protected exits and other various types of fire-resistive compartmentalization.
Other fire protection aspects that some folks may think of include:
Special suppression systems
Fire and smoke dampers
Emergency communication systems
Secondary water supplies for suppression systems
Secondary power supplies
Protection of elevators for occupants, as well as emergency responders.
Additional protection is provided for spaces that contain regulated materials, such as diesel fuel for generators and fire pumps, water purification chemicals for swimming pools and water features (fountains and manmade lakes), as well as woodworking areas, paint spray booths, and welding areas.
Unusual fire protection aspects also are incorporated into many of these facilities. These include deluge sprinkler systems and water cannons protecting high-bay spaces, along with the sophisticated detection devices that activate them. These detection devices frequently include a combination of beam type or air sampling smoke detectors in conjunction with UV and/or IR signatures. In some cases, linear heat detection and pilot heads also have been used to provide one of the detection signatures.
The required fire protection aspects and level of protection intended for these mega-resorts are fairly well documented in codes and standards. Which fire protection aspects are required and where is not the primary challenge. The primary challenge is properly coordinating the required fire protection aspects to provide a holistic approach for these “cities under one roof.”
How do we do it?
Clark County has jurisdiction over the unincorporated areas of southern Nevada, including the world famous Las Vegas strip. The Clark County Building Division has a number of guidelines, policies, and procedures to help expedite construction and keep it moving in a compliant manner.
The primary tool used in Clark County to coordinate fire protection aspects for these mega-resorts is called a Fire Protection Report (FPR). These reports have been required since the mid-1980s and have proven to be invaluable tools in describing and documenting the fire protection and life safety approach for a facility. Over the years, the format and level of detail in the reports, as well as the type of facilities for which FPRs have been required, have changed.
These documents focus primarily on fire protection aspects that span differing disciplines and trades. These are the most apt to fall between the cracks and create problems during systems testing and building commissioning, causing costly change orders and even delaying opening.
FPRs also give the owners and their insurance company the opportunity to specify additional fire protection aspects that exceed minimum code. The primary advantage is that these documents are an agreement between the jurisdiction and owners/designers. This substantially reduces last-minute debates on how the fire protection systems are intended to function. They also become a living record that provides substantial benefit for future renovations and expansions.
The concept of coordinated fire protection is outlined in the FPR for each specific facility. Some FPRs are as short as 30 pages, while others constitute volumes exceeding 1,000 pages. The level of detail depends entirely on the complexity of the building relative to fire protection.
Simple examples of coordinated fire protection aspects are a horizontal exit and hose valve outlets required at the exit doors. If the design includes a horizontal exit and the sprinkler contractor isn’t informed that additional hose valves are required, that could create a costly change order.
One common example of coordinated fire protection aspects is elevator systems. Although they are not typically thought of this way, elevators constitute highly sophisticated fire protection systems. This is often overlooked because the required protection is so ingrained into codes and standards that there are rarely issues serious enough to hold up building occupancy.
The standard prescriptive fire protection aspects for elevators in major facilities include:
The 2-hour hoistway with 1.5-hour automatic sliding hoistway doors
A maximum of four cars per hoistway
Automatic opening hoistway vents
Smoke detector activated recall with primary and secondary levels
Generators to provide secondary power
Air conditioning systems serving the machine room to protect the sensitive electronics
Emergency responder and public use two-way communication systems
Emergency responder manual overrides
Status panels in the fire command center (FCC).
If sprinklers are installed in the hoistway and/or elevator machine room, heat detector activated shunts are required to de-energize power to all elevators in the respective hoistway(s).
At times, elevator lobbies are required to reduce the potential for smoke migration from floor to floor. This also can be accomplished by pressurizing the hoistway relative to the landings on each floor. Lately, there is a movement to provide additional protection for emergency responders by requiring fire-resistive elevator lobbies at each floor level.
To protect the sensitive electronic equipment in the machine room from smoke, Clark County has historically considered an elevator machine room a separate smoke zone from the associated hoistway(s). Standard practice to reduce smoke migration through cable slots in the floor has been to pressurize the machine room relative to the hoistway.
From the preceding description, it becomes quite clear that elevators constitute holistic fire protection systems. The reason this complexity typically isn’t a problem is due to the specific code requirements and to all parties fulfilling their portion of those requirements.
One of the more complicated fire protection aspects in these “cities under one roof” are the smoke-management systems. Just like elevators, a number of fire protection aspects must be consolidated to ensure a properly functioning smoke-management system. But, different from elevators, the complexity of smoke-management systems isn’t as well codified. This is a good example of where FPRs can be an invaluable tool.
Smoke management can include fans, ducts, and dampers, as well as fire alarm initiating devices and the necessary control logic. Status and control panels also are required for active systems. Automatic sprinklers limit fire size and, as such, are a primary component. One pertinent component that should not be overlooked is passive containment or compartmentalization. Compartmentalization may even be deemed to meet minimum code without any fans or other active aspects necessary.
Now that the concept of coordinating fire protection aspects has been addressed, let’s take a look at one of the facilities presently under construction on the Las Vegas strip.
Project CityCenter is an MGM/Mirage development in which 76 acres are being transformed into 18 million sq ft of occupiable space for a cost of more than $7 billion. Based on code-required occupant load factors, this facility can accommodate more than 200,000 people. This surely is a city under one roof.
The site consists of six high-rise towers (hotel, condo, and time share) with more than 7,000 residential suites. The Central Plant, convention center, 2,000-seat theater, and parking garage also qualify as high-rise buildings. The gaming area is in excess of 100,000 sq ft. The mall area is approximately 500,000 sq ft.
One-half of the site is interconnected with an underground parking garage that includes a bus loading/unloading/parking area and two loading docks, which can each accommodate several 18-wheeled semis. There are swimming pools located on roofs at various locations of the site and even an automated people mover that interconnects CityCenter with the neighboring facilities to the north and south (Bellagio and Monte Carlo, respectively). Back-of-house areas include all support services needed to keep this city fully operational.
The fire protection aspects include the familiar and the unexpected as described in the introductory portion of this article. In addition to those aspects, substantial redundancy is provided for Project City—Center. The fire alarm system includes looped fire alarm control panels.
Not only do the sprinkler systems include the required primary and secondary water supplies and pumping systems, redundancy is provided if these primary and secondary systems cannot fulfill their intended function. In addition, redundant generators are at various locations throughout the site to provide secondary power if needed.
One of the most unusual redundancies is the presence of two FCCs. Although one is used as the primary on-site proprietary monitoring location, both FCCs provide identical functions. All fire protection systems can be monitored and controlled from either location with the primary location taking priority.
The site even includes its own fire station, provided by MGM/Mirage and staffed by Clark County. The fire station is not dedicated only to CityCenter. It also allows reduced response time to the Las Vegas strip and general vicinity.
Neither the owners nor the emergency responders want to alarm the contiguous facility simultaneously. Many of us are familiar with alarming the floor of origin, as well as the adjacent floors above and below. To reduce the need to discharge the entire site simultaneously, horizontal alarm zones have also been incorporated. These consist of minimally 2-hour fire-resistive walls with 1.5-hour opening protection that subdivide portions of the facility similar to the horizontal exit concept addressed in codes. Some of these alarm zones are used as horizontal exits, some are actually constructed as separate buildings (with fire walls/area separation walls/MFL walls), and some have been included only to limit the necessity of alarming substantial portions of the facility simultaneously.
Complex facilities like this cannot meet all prescriptive code requirements, however. Performance-based approaches are invariably necessary. The Alternate Methods Provisions of the codes allow the use of performance approaches provided they are able to demonstrate equivalency. To date, more than 50 alternates are approved for Project CityCenter. These range from mundane exiting issues to others that are substantially complex. They all substantiate mitigating measures that provide the level of protection the code intends.
A facility as large and complicated as this would not come together to provide a holistic approach to fire protection without all pertinent aspects being clearly documented and agreed upon upfront. The FPR fulfills this role.
Such cities under one roof are presently being constructed in other locations throughout the world, such as Macao, Singapore, and Dubai. Some of the largest buildings in the world exist in these locations, or are under construction. This is by no means the end of the complexity and extent of cities under one roof. One may say that this is only the beginning.
Where do we go from here?
We are all familiar with cruise liners that are nothing short of floating cities. Many can accommodate thousands of people and provide all necessary amenities.
What about cities beyond Earth? This is not as absurd an idea as you might think. Occupying the moon as a laboratory and launching pad for further space exploration has been proposed for years. An outpost on Mars also is being considered. In order to travel between these outposts, at some point spaceships that can accommodate any number of occupants will be necessary.
All these cities have several aspects in common. One is that they cannot easily be evacuated. As such, fire protection must be incorporated to allow a defend-in-place strategy and create structures that constitute a holistic fire protection system. The system to help develop a fire protection strategy for these futuristic cities is already in place and need only address the respective challenges for the specific situation.
The future of fire protection engineering is limited only to the vision of those involved.
|Evans, fire protection engineer, has been with Clark County Building Division for more than 16 years. Evans has an understanding of most fire protection aspects, with a specialization in coordinating fire protection aspects for major facilities, smoke-management systems, and unique interiors. He is a member of the NFPA and a Fellow of the SFPE. He serves on several professional committees and is licensed as a Fire Protection Engineer in California and Nevada.