Rehab On the Fast Track
With veterans coming home with a more serious array of injuries than ever, the Brooke Army Medical Center has responded with pool therapy, a domed simulator to create virtual environments as part of rehabilitation, and more. See how the project team worked swiftly on-site to bring dehumidification, displacement ventilation, and other HVAC elements into line to support a multifaceted facility that truly supports the troops.
The Intrepid Fallen Heroes Fund and the Fisher Founda-tion have opened a state-of-the-art rehabilitation facility for wounded American soldiers at the Brooke Army Med-ical Center at Fort Sam Houston near San Antonio, TX. The four-story elliptical granite façade building exhibits a stalwart image on the campus, living up to its name, the Center for the Intrepid. Defining and conceptualizing the outpatient amputee and rehabilitative clinic of the future was a chal-lenge for the design team, the architects (Smithgroup) and the MEP engineers (Syska Hennessy Group). The goal was to create exterior and interior spaces suitable for conducting world-class rehabilita-tive treatments while reducing the project delivery time normally required for projects procured for the military.
The result was a 65,000-sq-ft facility with a diverse program inclusive of clinical, research, and administrative programming all designed, planned, constructed, and delivered in an 18-month schedule. The rehabilitation equipment varied greatly, consisting of a gait walking lab, a computer-assisted rehabilitation environment (CAREN), a multi-pool natatorium, an indoor running track, a two-story climbing wall, virtual firearms training room, multiple fitness areas, and an entire floor dedicated to prosthetic fabrication. What makes the Center for the Intrepid different from other rehabilitative outpatient clinics is not only the complexity of the dense program but also the novelty of the features of the spaces that make the center an exemplary case study of the built medical environment.
Central to the rehabilitative program of the facility is the CAREN, a 21-ft-dia. dome with a 300-degree viewing screen used for creating virtual environments for the physical and mental treatment and training of patients. The interactive experience is enhanced by a six degree-of-freedom motion platform with an embedded treadmill on which patients must move, balance, and physically adjust during treatment. The 300-degree simulator, developed by Amsterdam-based MOTEK, is the first of its kind in the U.S. and as such presented the designers the opportunity to establish design precedence for future CAREN facilities in this country.
Acoustic isolation and environmental and lighting controls were all essential to the ambience of the CAREN. The designers found that in addition to acoustic treatment of walls and room penetrations, a dis-placement ventilation design inside the simulator was the optimal means of maintaining continuous background acoustics, while delivering variable cooling and ventilation to the patient and the CAREN equipment. Accordingly, the supply ventilation was introduced beneath the raised floor of the CAREN to cool the six-degree-of-freedom motion platform where patients stand. A 6-in. gap between the edges of the circular motion platform also allows the supply air to leave the floor plenum and creates the displacement effect inside the CAREN simulation dome.
Outside the simulator, designers and contractors met a different set of challenges. They needed to develop task lighting and fixture mounting devices to illuminate the CAREN, as well as support the workspace of its technicians and clinicians without interference to the simulation. The results rendered the CAREN as a sophisticated built environment, transparent to both its users and the controllers of the virtual environment inside.
NATATORIUM REQUIRES DEHUMIDIFICATIONProbably the most noticeable space in the Center for the Intrepid is the multi-pool natatorium. In addition to a six-lane, 50-ft long train-ing pool, an industrialized open structure motif, and a stainless steel ventilation system (that raises eyebrows in this 25-ft tall hall) is an elevated surfing pool called the FlowriderTM. In a sloped 400-sq-ft pool surface, the Flow-rider circulates 18,000 gpm, creating a 3- to 4-in. sheet of water moving at 25 mph. Both pools enable patients to undergo rehabilitative treatment through an assortment of water activities such as swimming and surfing for physical therapy and prosthetics testing and training.
The housing of Flow-rider and the training pool in the same hall without separation added a level of complexity to the natatorium’s mechanical design. In terms of humidity control, the Flow-rider drives the dehumidification load of the building when activated. To achieve proper dehumidification, rooftop direct-expansion dehu-midification units, with hot water reheat and pool water heat recovery coils by Desert Aire, were selected. Ultimately, sizing of the rooftop dehumidification equipment was based on the worst case Flow-rider mode, which assumed simultaneous activity of the Flow-rider equip-ment, training activities in the six-lane pool, a modest group of spec-tators, plus the outdoor ventilation load for pressurization.
Load calculations for natatoriums depend on the rate of evapo-ration and activity factors, with multipliers used to account for the occupant usage of a pool. While activity factors (Fa) for the training pool and wet surface on the Flow-rider were respectively 0.8 and 0.75, the Flow-Rider ride surface activity factor was rated at 7.1. As a result, the dehumidification equipment was selected so that compressor cycling could achieve a turndown ratio of 4:1 in load capacity from Flow-rider mode to non-occupied mode.
Dehumidification of latent loads was also important in other spaces of the Center for the Intrepid. The reality of rehabilitative treatment of military amputees was not isolated to patient and clini-cian, but also, more often than not, fellow officers, servicemen, and family members supporting the patients during treatment. As part of the design criteria, designers were asked to account for these variable occupancies throughout the facility.
HVAC SYSTEMS SUPPORT THE VARIABLE OCCUPANCIESDesigners selected a pretreated outside air design for the central VAV ventilation systems. Outdoor air gets filtered and dehumidified with chilled water-cooling coils prior to mixing with recirculated return air, resulting in lower mixed air temperatures. As a result, the pretreated outdoor air design separates ventilation latent loads from occupancy loads, helping to reduce HVAC equipment size, and improving the control of entering main unit cooling coil conditions. This allowed for better tracking and response time of the internal cooling demanded by the main VAV units, as main cooling coil valves would only react to internal demand without the influence of swings in outdoor air conditions.
While the application of pretreated outside air is not particularly new to a health care facility, the additional design criteria of large variable occupancies for clinical use should be noted, if such criteria proves a future measure of quality in health care treatment. Although AIA health care guidelines and U.S. Army Unified Facilities Criteria (UFC) publish minimum design parameters for occupancies for treatment facilities, laboratories, and offices, the reality of the needs actually generates the variable occupancy criteria for the designers. As such, the Center for the Intrepid may reflect an emerging health care standard.
CAREFUL COORDINATIONAs the design progressed, based on a truly aggressive delivery schedule, the construction was already under way. The Syska team and the contractor communicated daily (and sometimes hourly) on issues of system insets, sleeves, anchors, pour pads, hangers, materials, etc., and all the constructibility details that are traditionally covered in the construction team’s coordination effort.
Review and turn-around of shop drawings and requests for information (RFI) became critical. Approximately three months into the construction schedule, members of the Syska team, rep-resenting each trade, were dispatched to the site weekly to review shop drawings on the spot. Decisionmaking and enforcement of the contract requirements were done at a pace not seen before. The final shop drawings for the ductwork and electrical were literally approved/reviewed on site, and were the same as the “as-builts” after the installation in the field was complete.
Many of the areas above the third-floor running track were exposed architectural concrete where air devices, light fixtures, and sprinkler head locations were actually spotted on concrete forms as the pours were under way. As soon as an above-ceiling inspection area was complete, the ceilings went in and the crews moved ahead - no callbacks allowed.
Even though the pace of the construction effort was intense, the design and construction team insisted on a contract provision for coordinated ductwork, piping, and electrical drawings. The subcontractors accepted these requirements as directed as part of their overall risk adverse approach to the construction process. The sheet metal subcontractor took the lead in providing shop fabrication drawings for the ductwork and delivered them to the other major trades for their review.
The benefits were that the design engineer had positive proof that the DIDs could/would be implemented, and the subcontractors gained the confidence that what was included on the fabrication drawings would really work in the field without expensive and time-consuming fit and location issues. This valuable step is one that should not be over-looked on any project. In fact, the shorter the customer’s schedule, the more important the coordination drawings become.
PACKAGING THE PRIME MOVERSIn order to expedite the construction process, the chiller plant with pumps, boiler plant with heat recovery from the natatorium dehumidification system, and heat reclaim/pool heating system were specified as pre-packaged and shipped to the site. This meant that equipment within the individual prime mover array was manufactured off-site, pre-piped, pre-wired for power and control, factory tested, and shipped to the site for installation as a unit. Pre-purchasing and packaging for chiller and boiler plants reduced the time required to gather and install the necessary components and put each system into action. Field-testing was virtually eliminated, as each package was pre-tested in the factory for certified performance.
The pre-packaging of major elements of the HVAC system and the close on-site coordination with the design and construction teams were keys to the on-time completion of the work. Experienced engineers with the responsibility and authority to make critical buildability decisions on-site were also important to the design/construction/turnover process.
It is on this note that the statement by Arnold Fisher, honorary chairman of the Intrepid Fallen Heroes Fund, resonated on the opening day of the Center for the Intrepid. His statement, which recalled that the center was entirely funded by private donations, emphasized that if motivated, the needs of America’s wounded could be met better and faster by the people than from its government. The Center for the Intrepid is a reflection of what can be done in health care architecture, engineering, and construction if society simply chooses to push forward and do things a little differently. ES