From its founding in 1909, The Walter Reed Army Medical Center has served more than 150,000 military personnel. Many improvements and renovations later, it was ultimately determined that a major addition was needed to maintain quality patient care. Today, a new era has begun for the newly completed Walter Reed National Military Medical Center, located in Bethesda, MD, on the grounds of the National Naval Medical Center.
For this giant health care site, a mechanical systems giant — the Southland Industries branch in Dulles, VA — was chosen to provide Design/Build mechanical, plumbing and medical gas services. The project, procured through a Design/Build competition, included the construction of a 345-bed medical center. It provides the full range of intensive and complex specialty and subspecialty medical services, including specialized facilities for the most seriously injured.
The new facility, located at the current site of the National Naval Medical Center in Bethesda, MD, is expected to become the U.S. military’s premier tertiary referral center for casualty and beneficiary care. It will offer postgraduate education and other training, and will serve as a critical medical research center. The Naval Facilities Engineering Command (NAVFAC) oversaw the planning and construction of the project.
The project consisted of both new construction and renovation of existing buildings. Southland’s scope of work for the new construction included the design and construction of the mechanical, plumbing and medical gas systems for a:
- 533,000 sq.ft. medical office building
- 157,000 sq.ft. addition to the existing hospital
- 340,000 sq.ft. patient parking garage
- 400,000 sq.ft. multi-use parking garage and upgrades to the campus central utility plant, along with utility infrastructure upgrades and expansion to serve the added spaces.
100% Outside Air
Health care facilities present a design challenge to ensure a safe and healing environment. There’s risk of the transmission of infectious disease through the HVAC systems. Emerging issues such as drug-resistant tuberculosis and severe acute respiratory syndrome (SARS) have elevated these concerns. An HVAC system that doesn’t re-circulate the indoor air, but instead uses 100% outside air at all times will enhance the indoor air quality by ensuring that any infectious organisms in the air aren’t moved to other areas of the facility, but are instead exhausted to the outside.
The premise of the selected HVAC system allows for improved indoor air quality compared to traditional systems. Using 100% outside air means that there’s a constant influx of fresh air throughout the buildings. The project achieved a Leadership in Energy& Environmental Design (LEED) Innovation in Design credit for the 100% outside air approach as it applies to air quality. Southland implemented numerous innovative mechanical and plumbing features into the design of the project. The design consists of a constant volume HVAC system that uses 100% outside air, which helps with infection prevention, as well as pressure control within the hospital. Most traditional systems are designed with a recirculating return air system. (Additionally, one of the mandates of the request for proposal was to deliver, at minimum, a LEED Silver project. At the project’s completion, it won LEED® Gold.)
Taking this into account, an energy efficient HVAC system was designed. Large, Thermotech enthalpy heat recovery wheels recover energy from the buildings exhaust air before it’s exhausted from the building.
"A significant feature for a healthcare mechanical system is the ability to deliver and maintain the required amount of outdoor air, while meeting the project's RFP energy reduction goals," says Lead Engineer Chris Skoug. "Conventional recirculating (mixed air) systems typically fail to provide or maintain the required amount of outdoor air (ventilation) to the occupied space. This issue is compounded when using variable air volume systems to reduce energy consumption. The fundamental challenge of providing and maintaining U.S. Department of Defense Unified Facilities Criteria (UFC) required outside air to the occupied space, while reducing energy still remains difficult to accomplish in a lifecycle cost-effective manner," he says.
Multi-Stack heat recovery chillers pre-heat the building's water heating system. A copper/silver ionization system provides for Legionella control in the hospital's domestic hot water supply. Large, custom air handling units by Buffalo Air Handling, are manifolded together for redundancy and enhanced control of the indoor environment.
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Special Mandate for All Teams
Since the construction of the new buildings was performed adjacent to, and in some cases, "on the other side of the wall" from an active hospital facility that couldn’t be shut down, the workers were instructed to “do no harm” to the patients, visitors, and employees of the existing National Naval Medical Center complex. Each day, tradesmen were briefed on the potential hazards of their activity to the adjacent facilities. Infection Control Risk Assessment (ICRA) plans were developed and discussed daily to ensure the construction related activities would not have any adverse affects on the active departments within the existing facility.
"In a hospital, each room is unique. During the Design/Build process you begin to understand the function of each room. The end user's needs must be met —for HVAC, medical gas, lighting, or any of the other unique security and communications systems in the rooms," Skoug says. "The team needs to partner with the end user and other team members, to understand the function of the rooms. We would meet to discuss the design needs of those "atypical" rooms, such as operating rooms, or those that contain major medical equipment. We had to understand their purpose and function, in order to properly design and build that space to meet their needs."
Energy Efficiency for Heat Transfer at 83%
For this massive Design/Build project, Southland and the project team were able to work together to select energy efficient options best suited for the facility. For example, the building envelope was upgraded to include features that would support the energy efficiency of the mechanical design. Highly-efficient space lighting systems and controls were used, which are all considerations for the HVAC system.
"It wasn't uncommon for health care spaces to have a conflict between lighting illumination levels, as prescribed by UFC and the lighting power consumption levels as prescribed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1," Skoug explains. "We'd meet regularly with electrical engineers to ensure that the design was meeting both goals In some specific spaces, the lighting power reduction couldn’t be met; yet, we still achieved 30% lighting power reduction for the entire building."
The HVAC system incorporates the use of enthalpy heat recovery wheels, to transfer energy between exhaust and incoming outside air and energy-efficient water-cooled centrifugal chillers. The enthalpy wheels use a molecular sieve desiccant to allow both sensible and total energy to be exchanged between the incoming outside air and the exhaust air.
The total effectiveness of the wheels exceeds 83% by minimizing the face velocity across the wheels, which minimizes air pressure drops and maximizes heat transfer. The 100% outside air system with heat recovery wheels also results in a significant reduction in installed system capacities compared to a traditional re-circulating air system that’s ASHRAE 90.1-2004 compliant. The chillers, cooling towers, and circulating pumps are all reduced by approximately 10%. An entire duct system is deleted and only one main exhaust system is needed. The new central chilled water plant will produce chilled water for building cooling and process needs. This plant consists of three 1,000-ton capacity water-cooled centrifugal electric chillers. Three evaporative cooling towers provide heat rejection for the chillers. Variable flow primary chilled water pumps distribute the chilled water to coils in air handling units and fan coil units in the new buildings.
Rather than using these central chillers for heat recovery, separate, dedicated heat recovery chillers were installed in each of the two new buildings for that purpose.
Commissioning & Communication
Southland worked closely with the owner from day one. The commissioning agent, Chinook Systems, Inc. delivered a project that was fully commissioned and operating according to design intent.
"We held weekly commissioning meetings with Southland employees, the general contractor, the commissioning agent and the owner, to resolve any questions," Skoug says. "As part of the commissioning process, some issues are inevitable. You seldom start it up and walk away."
This commissioning effort started during the design phase and continued through earliest consultations with the commissioning team. Ongoing discussions ensured that certain components — such as valves, dampers, control components, etc. — were designed to allow a phased commissioning approach. During the design phase, each piece of equipment on the project was given a "smart tag" that automatically generated and populated start-up forms, TAB forms, pre-functional, and functional performance test forms with information to facilitate and streamline commissioning.
'Priceless' Care Continues
Each project partner worked at risk for approximately one year, developing concepts, schedules and constructability reviews, and budgets. In the end, it was through this coordinated effort that the team won the project. The project’s cost — more than $117 million — gives some idea of the scope of expertise and vast area needed for one of the world’s leading medical facilities. However, what price is too dear, when providing for the health and well-being of the U.S. military personnel who have fought and sacrificed to keep us free?
Congratulations to Southland Industries, and the entire Design/Build team, for earning this Contracting Business.com Design/Build Award for the Walter Reed National Military Medical Center.