The Pentagon’s Hvac Attack
Without a major renovation, it was determined that the building infrastructure would soon be unreliable and unable to effectively support the headquarters of our nation’s military. It has finally reached a point where major building systems have deteriorated to such an extent that repairs are no longer effective and entire systems need replacing.
While it goes without saying that a major overhaul of the Pentagon is not your average, everyday undertaking, there are other factors that have made this project unique. We’ll cover some of those aspects in this first half of the two-part series. For example, how do you take an old system offline and bring a new system on without disrupting the 23,000 people who work there?
The second part will cover two other unique aspects of the project; that is, much of the project will be design-build rather than the usually government-favored design-bid-build. For another, the project will undergo continuing, and possibly retro, commissioning.
Background InformationAlmost 10 years ago, a plan was approved to renovate the Pentagon in 1 million-sq-ft “wedges,” with renovation of the basement considered as a separate project. The plan called for the complete removal of all support systems (mechanical, electrical, plumbing) down to the base structural system and then construction of all new systems. This full-scale removal was deemed necessary due to the presence of asbestos in the plaster ceilings, floor tile, air conditioning ductwork, and pipe insulation. Removal of plumbing systems is based on the high probability of catastrophic failure.
According to the Pentagon, the renovation program will provide all new mechanical, electrical, and plumbing systems; sprinkler systems; toilets; vertical transportation; cable management systems; improvements in fire and life safety systems; and flexible ceiling, lighting, and partition systems.
The renovation will also provide disabled accessibility features throughout, preserve historic elements, upgrade food service facilities, construct collocated service operation centers, install modern telecommunications support features, comply with energy conservation and environmental requirements, reorganize materials handling and provide safety improvements in vehicular and pedestrian traffic.
The first phase of the renovation involved the construction of a new heating and refrigeration plant, which was completed in 1997. At the same time, a center courtyard utilities tunnel was constructed. The tunnel houses piping and conduit to distribute building utilities provided by the new plant, including new steam, chilled water, natural gas, domestic water, and fire protection lines.
The second phase of the program involved the renovation of the basement and mezzanine. The third through seventh phases of the program are the five wedges of the building from the first floor to the fifth floor. These areas have been determined to be the optimum divisions for renovation while continuing operations.
The renovation of the 1 million-sq-ft Wedge 1 began in January 1998 as a design-bid-build project and is scheduled to be completed in the summer of 2001. However, personnel are expected to begin moving into renovated portions of the wedge as early as February 2001. Wedge 1 will serve as a model for Wedges 2 through 5, which are currently being planned as a single design-build acquisition, with construction phased by wedges.
It’s important to keep in mind that this is not your normal renovation, where people move out and then everybody moves back in when it’s finished. Wedge 1 housed 5,000 people, who needed to have new office space while their old space was being renovated. Tom Fontana, public affairs specialist at the Pentagon, says that accommodating the need for new space involved leasing office buildings nearby, including almost 45 floors of building space, which then had to be renovated before the tenants could move in.
“When personnel moved into their new offices outside the Pentagon, they had to feel like they were still in the building in terms of security, connectivity, and functionality. Clearing the wedge was a two-year effort that involved several teams working real estate, furniture, communications, and move issues. Then, instead of moving the people outside back into Wedge 1, it makes more sense for us to move the personnel from Wedge 2 into Wedge 1, Wedge 3 into Wedge 2, and so forth. When we get to Wedge 5, we’ll move the people outside back in the building,” says Fontana.
New Plant And UtilitiesBefore the Pentagon proper could be renovated, it was first necessary to upgrade its heating and air conditioning systems, which had become obsolete. In fact, at one point, boilers and chillers were brought in on the back of flatbed trucks and connected to the existing utility distribution system in order to keep tenants comfortable. This went on for several years, at a cost of about $200,000 a month.
Brian Dziekonski, construction IPT (integrated product team) leader at the Pentagon says that the old system was based on steam and chilled water, so for continuity, it was necessary that the new system be the same. “We have to keep the old systems operating in the unrenovated building until all of the new systems are installed. The courtyard utility system serves all new equipment and maintains the loop continuity of the old distribution, so we can demolish old sections in each wedge while maintaining system reliability."
The new plant was built about 10 feet away from the old plant. When the new plant came on-line, it was possible to demolish the old facility entirely. The main emphasis for the new system was energy efficiency. An executive order actually required that the Pentagon reduce its energy costs 35% by 2010, and most of that savings has already been achieved just by upgrading the heating and refrigeration plant. It’s hoped that the same amount of energy savings can also be achieved by changes being made to the building envelope, including over 7,700 new, double-paned, thermal-insulated windows.
The Pentagon’s heating and refrigeration plant relies on a single 72-in. diameter concrete condenser water intake pipe for its supply of chiller condenser cooling water. It also relies on a single 54-in. diameter pipe for return of condenser water to the Potomac River. The system is configured as a “once-through” system, with the supply originating in the nearby Boundary Channel Lagoon and the return piped to Roaches Run Waterfowl Sanctuary.
The new plant includes various electrical and mechanical redundancy features to maximize its reliability. Additional chilled water supply and return and steam/condensate systems were added to connect the plant to the Pentagon. Fontana notes that six boilers and 10 chillers in the new plant provide redundancy to ensure reliability.
“There are more chillers than are absolutely necessary to keep the Pentagon cool,” he notes, “so that even during the peak of summer, they can repair or maintain the chillers that are down while the others are running.”
The ongoing condenser intake-outfall design will provide an additional condenser water intake route from a new intake structure located on the shore of the Boundary Channel Lagoon. This structure is designed to draw water off the bottom of the lagoon, which is cooler than the surface water. A new, 96-in. intake line will transport cooling water from the new intake structure to a new traveling water screen structure.
Two existing 60-in. intake lines will interface between the new traveling water screen structure and the previously designed condenser water system at the plant.
The design also provides a second condenser water outfall route. A 72-in. in diameter pipe will convey condenser water from the plant to Roaches Run Waterfowl Sanctuary. The routing of the new outfall pipe will follow the right-of-way of a railroad spur east of the plant.
Challenges AboundAs stated earlier, Wedge 1 has been entirely gutted. But the demolition process itself was difficult, because there were many unforeseen site conditions. The original drawings of the Pentagon are almost useless, because they haven’t been upgraded over the years. When workers would break into a wall, they’d often find a mesh of conduits and wires, and they wouldn’t know where things were going or where they were coming from.
“It’s a very painstaking, meticulous process to trace every pipe, every conduit, every phone line, lest we cut a computer around the other side of the building or terminate a water supply line,” says Fontana. “In 1943 when the Pentagon was completed, there were no computers or fax machines or printers. You had a telephone on every third or fourth desk at best, and that’s it. Over the years as technology changed, no one ever bothered to update the drawings. When we do excavation, we often hit lines that aren’t supposed to be there or are supposed to be 10 feet over according to the drawings.”
The remaining 20,000 tenants also pose a challenge to the project, as those bordering Wedge 1 are sometimes disrupted by problems such as water migration. “There’s only a construction barrier wall separating us from the tenants on the other side. It’s supposed to be water sealed, but water always seems to migrate. We have to open up the roof to install equipment and provide elevator mechanical rooms, and water’s going to migrate through the floor and walls,” says Dziekonski.
Sometimes that water migration is to a general’s office, jokes Fontana. He adds that noise has been a problem as well. “Sometimes we have to drill and use jackhammers during the daytime. That’s one of the biggest challenges of the whole program Ð working around people, keeping the rest of the building operational and minimizing the disturbance.”
Ceiling space is also a major issue. The building previously relied on old fancoil units underneath the windows, and outside air was brought in from an air handler on the fifth floor. The ductwork itself contained asbestos and had to be removed. (An interesting side note, when Wedge 1 was gutted, about 4 million pounds of asbestos contaminated material was removed, as well as about 20 million pounds of debris. Fontana notes that they were able to recycle about 70% of the material.)
While it seems that it would be easy to put in new systems once everything was removed, it’s been a challenge, primarily because of space constraints. “There not a heck of a lot of overhead room,” says Dziekonski. “We’ve got to get the new electrical in there, and the building wasn’t originally designed for having full electrical and computer interconnectivity. A lot of room in that ceiling space is used up just for conduits and ladder trays for carrying the fiberoptic cable and so forth. The difficulty is you have very little space.”
Due to space constraints, they’ve had to use spiral-round, flat-oval duct throughout. “The biggest challenge has been because we’re using a ceiling plenum, the ductwork itself is in most cases no deeper than 6 inches. Even then you have trouble making sure you can get return air past your ductwork in locations. So it is a very tight situation. The building was never intended to have ductwork, but we’re adding it to bring the facility up to code,” says Dziekonski. A distributed vav system has air-handling units placed in the light wells in Wedge 1. Structural additions had to be made in the light wells themselves to carry the air-handling equipment.
While Wedge 1 will serve as a guide to the ventilation systems being placed in Wedges 2 through 5, they will not be identical. As Dziekonski notes, “What are my chances of finding the same set of controls three years from now, let alone ten? It’s essentially zero. Basically, we’re working with a million square feet at a time, and that’s a pretty uniform space.”
He notes that they are trying to maintain uniformity in piping and valve locations for ease of maintenance, but they hope to take advantage of any additional technology or savings in materials they can find as they go along. For example, there’s a basement under portions of Wedges 3 and 4, so the renovation team is considering whether or not it would be possible to place some large air-handling units in the basement, rather than copying Wedge 1, which has more than 90 distributed air-handling units.
“We’re always considering better and smarter ways of doing business, and that’s one of the reasons why we’ve moved to the design-build approach rather than trying to go with the design-bid-build. The old way diminishes the incentive to improve the design as we go along. We’ve got 13 more years of work ahead, so we’d like to be in a position to take advantage of any technological advances we can find during the course of renovation,” says Dziekonski.
Stay tuned for a further discussion of the design-build process in next month’s issue. ES
A Briefing On Pentagon HistoryThe Pentagon, headquarters of the national defense establishment and the nerve center for command and control, is virtually a city within itself. The Pentagon presently houses approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel dedicated to protecting our national interests.
The Pentagon building, institution, and symbol was conceived at the request of Brigadier General Brehon B. Sommervell, Chief of the Construction Division of the Office of the Quarter Master General, on a weekend in mid-July 1941. The purpose was to provide a temporary solution to the War Department’s critical shortage of space and to consolidate 30,000 War Department personnel who were scattered among 17 different buildings in Washington, DC. The rapidly expanding War Department envisioned a single structure in which to house all its components, as opposed to constructing multiple temporary structures as was then the practice.
Congress, cautious about the considerable cost and magnitude of the project, but anxious about events in Europe and the Far East that could require U.S. military intervention, appropriated the funds necessary to construct the War Department’s new home (approximately $83 million) on August 14, 1941. The ground-breaking ceremony took place on September 11, 1941.
The building was constructed out of reinforced concrete made from 680,000 tons of sand dredged from the Potomac River; it is supported by 41,492 concrete piles. The designers’ ingenuity not only created a building that reflected the architectural style of the nation’s Capitol but also saved enough steel to build an entire battleship. At the height of construction, over 400 architects worked in an adjacent hanger producing enough prints to supply the 15,000 construction workers and tradesmen.
Three shifts worked 24 hours a day, every day, constructing the Pentagon wedge by wedge. These wedges were occupied as they came on-line, with the first personnel moving into the Pentagon in April 1942, just eight months after construction began. The building was dedicated on January 15, 1943, nearly 16 months to the day after the groundbreaking.