Top Grade for USDA
January 01, 2007
Appeared in Consulting-Specifying Engineer
Charged with the mission of supporting the nation's agricultural production, food safety and nutrition, as well as protecting the environment and advocating for rural communities, the U.S. Dept. of Agriculture (USDA) had outgrown its headquarters complex in Washington, D.C. Consequently, a major upgrade was necessary and is well underway, involving a $250 million phased renovation of the complex's 2.25 million-sq.-ft. South Building, to be completed over a 10-year period.
The ultimate goal? A class-A office building with upgraded and replaced mechanical, electrical, plumbing, life safety—fire suppression and fire alarm—telecommunications and security systems.
The new fire suppression system is a good place to start. The system is an ideal example of how extensive the renovation will be. It includes fire service connections to municipal mains from two separate municipal grids, new fire pumps, a combined fire standpipe and sprinkler main in the sub-basement, and a new automatic sprinkler system throughout the building. Each wing, including a part of the head house and tail house, will be supplied from a sprinkler floor control valve assembly.
The new fire alarm is an addressable multiplex system providing voice-activated, selective evacuation of the floor of occurrence, as well as one floor above and below within each of three new horizontal fire zones. According to Michael Sazonov, project manager for the USDA Modernization Program, one of the project's key goals is to provide horizontal fire zones and a state-of-the-art fire alarm system that allows selective evacuation of the building.
Syska Hennessy Group, in a joint venture with architects Shalom Baranes Assocs., Washington, D.C., prepared the master plan for the phased renovation of the building, while Syska was responsible for master planning and design of the mechanical, electrical, plumbing, life safety, telecommunications and security systems.
Renovation of the building began in 1998, with each of the project's five phases comprising approximately 200,000 sq. ft. of space. The general scope of work for each phase is an upgrade of the M/E/P and life safety systems, along with architectural upgrades to create new offices. After renovation of the base building and core area in each phase, USDA determines which agencies will move into the renovated space. The project team then works with individual tenants to design the fit-out.Even more reliable
The South Building's existing fire suppression system—an automatic sprinkler system—originally was installed only in the sub-basement, basement and mechanical equipment penthouses in the attic, while standpipe risers with hose cabinets were installed throughout the building. The existing hard-wired fire alarm system, installed in the mid-80s, is a general alarm that sounds throughout the facility, requiring general evacuation of the entire building.
During the building inventory performed in preparation for development of the master plan for the fire suppression system, the project team determined that there were separate piping systems for the standpipe system with two pumps and for the limited automatic sprinkler system with one pump, supplied by one main from the municipal water supply.
To update this inefficient system, a key project goal was to provide a combined standpipe-sprinkler system, with one UL-listed fire pump and two separate fire service connections from independent grids on the District of Columbia municipal system. The fire pump was sized for the most remote hydraulic zone of the entire building. As each phase of modernization occurs, hydraulic calculations are provided for the applicable phased area. The project team then coordinates with the District of Columbia Water and Sewer Authority to determine the ideal location of the pump to support increased reliability for the two independent fire services.
A key technical challenge was phasing construction to maintain occupancy, considering the separate standpipe main and sprinkler main in the sub-basement. The solution was to install a combined 8-in. standpipe and sprinkler main in the sub-basement and, from that point, renovate each wing with the new piping infrastructure in place. The design and phasing of the project provided for Phase 1 installation of the new combined standpipe-sprinkler system loop main in the sub-basement attached to the new fire pump. This allows for the new fire suppression system piping to connect with the new 8-in. combined main as each phase proceeds and existing pipes are removed where renovations have been completed. Eventually, all of the existing piping will be disconnected and removed. In every area that is protected with the original sprinkler system, the design provides for replacement of all piping and sprinkler heads with quick-response heads wherever they don't exist as a result of previous upgrades.Selective fire evacuation
To a large degree, the project phasing scheme was determined based upon factors beyond the fire suppression issue, including those related to the electrical power and emergency power systems. However, the fact that the existing building was on a general fire alarm was a significant issue in the phasing scheme. Given the fact that the building's occupancy exceeds 5,000 people, USDA wanted to avoid the logistic and traffic problems associated with a general evacuation to C Street and/or Independence Avenue.
Consequently, the project team suggested a provision of a selective evacuation plan based on horizontal fire zones. First, the team explored the creation of two horizontal fire zones by constructing a fire wall down the approximate center of the building. However, this proved impractical due to various spatial issues in the building. As an alternative, the team identified three horizontal fire zones with locations for the construction of two fire walls.
To provide the optimum selective evacuation scheme, the team suggested the implementation of a selective evacuation plan as if this were a high-rise building, even though the South Building is not defined by code as a high-rise, which involves the floor of occurrence, floor above and floor below within one horizontal fire zone. In the end, the result will be a dramatic reduction in the number of evacuees in the event of an alarm, from a total population of 5,000-plus to approximately 250 occupants.
Because the first horizontal fire zone will be implemented with the completion of Phase 4, this created a technical challenge for installation of the control panel and devices for the new fire alarm system while maintaining the existing general fire alarm system. The solution, of course, was to replicate systems. During each phase of the project, contractors are installing the new visual and audible notification devices, tying these back to a new fire control panel and interconnecting the panel to the existing system. Thus, the new devices in a renovated area operate as part of the existing system until such time as the first horizontal fire zone is completed. At that time, the software operation of the completed horizontal fire zone area will be converted to the selective evacuation plan, and the operation of the fire alarm system for the remaining two thirds of the building will remain on the general evacuation plan.Working in historic areas
In selection and installation of fire alarm devices, the designers were sensitive to historic preservation issues. Consequently, the designers specified low-profile or concealed sidewall heads for the project. Ingenuity was required to route and install new M/E/P and life safety infrastructure while maintaining the historic appearance of the building on the first floor and throughout the head house and tail house, where, for example, the existing corridors have transom doors at each office.
Working with its architecture joint venture partner, Syska Hennessy's designers created a bulkhead running the length of these corridors behind the transom, inside of which ductwork for the HVAC system and sprinkler piping was installed, and transoms are back-lit to maintain their original appearance. Where infrastructure crossed corridors, smaller pathways are designed in a pattern suggesting architectural moldings.
A number of measures are also in place to reduce the impact of construction on building occupants. For example, the project team included in the bid documents the requirement for temporary construction barriers to be made of drywall in order to reduce the noise. As construction proceeds, each wing is blocked off at the north and south ends, or within the head house, while allowing movement within the stairwells and floors.A living program
In sum, the USDA Modernization Program is a living program that must respond to timely events and code or program upgrades as the design and construction of each phase progresses. One example of this is the fire alarm system requirement for operation of visual and audible notification devices to be synchronized. Although this requirement did not exist at the onset of the project, it is now a requirement and has been included in the Phase 4A bid documents. Discussions have begun regarding how this requirement can be implemented in the phases that have already been completed.