Construction, renovation and maintenance of building water systems in complex facilities is inevitable, and each event may pose an infection risk from waterborne pathogens, particularly in healthcare or long-term care settings.

Outbreaks of Legionnaires’ disease following construction have been well documented in the peer-reviewed literature, news and anecdotally. Proactive planning and consideration for legionella and other waterborne pathogens can manage the growth and spread of these organisms during facility occupancy and beyond.

Legionella is a waterborne pathogen that can be found within biofilms and bulk water in warm building water systems, such as potable hot water and nonpotable systems such as cooling towers, decorative water features, spas and other water-based equipment. Present in natural water sources, legionella can travel through the public water treatment and distribution systems and enter the building water system at low and often undetectable quantities. Conditions within the building water systems exist which allow for the amplification of legionella, including warm temperatures, nutrients and the presence of other microorganisms. Legionella is not ubiquitous; however, studies have found legionella in about 50% of surveyed building water systems.

Many cases of construction-associated Legionnaires’ disease have been reported for healthcare facilities, including renovations of occupied buildings and in newly constructed facilities. Often a common factor in these cases is that environmental testing for legionella was not performed prior to occupancy, conditions during construction allowed legionella to grow in the water system and disinfection prior to occupancy was not performed or inadequate.

Legionnaires’ disease has also been reported in non-healthcare facilities. One of these cases was reported at a newly opened aquarium facility, where 125 cases of Legionnaires’ disease were confirmed, and the cooling towers were found to be the most likely cause of the outbreak. Another example was reported in a hotel shortly after opening. Legionella was found in the hot-water system and 10 cases of Legionnaire’s disease were confirmed. The water system was treated with both a chlorine solution and flushing of the system. A third example was reported in a newly built apartment complex. In this example, two cases of Legionnaires’ disease were confirmed. Legionella was found in the hot-water system after occupancy and additional water treatment was required.

ASHRAE Standard 188 is the first U.S. legionella standard and requires building owners to address legionella risk in their existing buildings. ASHRAE 188 also includes Section 8 entitled “Requirements for Designing Building Water Systems.” This section includes guidance to minimize legionella risk during construction and specific responsibilities for those implementing new construction, renovation, refurbishment, replacement or repurposing of a facility. The four components of Section 8 are as follows: 

  1. Design compliance includes specific items that need to be considered in the design to address potentially hazardous conditions. These include items such as flow diagrams, which become part of the facility’s water safety plan, and documenting design elements to prevent conditions which could reduce water quality, impact the ability to maintain and monitor the water systems or increase the risk for legionella.

  2. Final installation documents include a list of deliverables that should be provided to the building owner to document the design. These documents are commonly provided as part of the turnover deliverables; however, there are some specific items which in the past may not have been included in project documents. These final installation documents need to be appropriately specified to ensure they are included in the drawings and documents provided to the owner at the conclusion of construction.

  3. Balancing provides a single requirement that all water systems shall be balanced, and the owner should provide a report documenting the balancing needs. Balancing of water systems is important to ensure water systems operate as designed and efficiently deliver water to end uses without impacting water quality.

  4. Commissioning requires both post-construction flushing and disinfection are specified and completed prior to occupancy of the project. While ASHRAE 188 provides reference to common disinfection practices (i.e., AWWA C651), it does not discuss appropriate testing to demonstrate efficacy of the disinfection process prior to occupancy. This is a gap in the standard that is left up to the program team to identify and specify proper environmental testing for legionella to demonstrate risk has been minimized prior to building occupancy. The commissioning component also requires that the building water system performance is documented to meet the design parameters.

As part of the program team responsible for implementing the standard, ASHRAE 188 states that team members “…shall have knowledge of the building water system design and water management as it relates to legionellosis…” Architects, engineers and consultants involved in building construction projects certainly have knowledge of building water system design but may be less knowledgeable about water management programs and specific interactions of the design decisions as they relate to legionella.

A project team may want to consider these questions when evaluating a construction or renovation project with respect to ASHRAE 188 and managing legionella:

Is the project covered under ASHRAE Standard 188? If yes, has the owner made provisions for the requirements of the standard to be addressed?

Is this part of an existing building? If yes, is there a water safety plan already in place that requires coordination? Has previous environmental testing been performed to understand what baseline conditions are before design/construction begins?

Has a risk assessment of proposed building water systems, building use, and occupants been completed to understand the potential for legionella growth and susceptibility of the occupants?

Was design coordinated with the water safety program for the building to ensure operability, considering things such as system layout/isolation, locations of monitoring points, environmental sampling taps, and materials and equipment compatibility with proposed shock or supplemental disinfectants?

Has the design addressed hazardous conditions which could lead to legionella growth? Were any of these design components value-engineered out or lost by change-order or alternate bid items?

Was proper commissioning prior to occupancy specified with adequate documentation? Have provisions for delayed occupancy been made to prevent growth of legionella after commissioning but before occupancy?

As part of commissioning, was environmental testing for legionella specified with adequate requirements for sample collection methods, sampling locations and laboratory qualifications?

To answer some of these questions, the project team needs to reflect on its level of knowledge as it relates to legionellosis. The team must determine if evidenced-based answers can be documented by reference to existing guidelines and peer-reviewed literature, or if additional consultation with an expert in legionella microbiology, engineering or infection prevention is needed to support the team. To further the legionella and waterborne pathogen knowledge of the project team, future articles in this series will provide additional information on legionella and other waterborne pathogens in building water and specific discussion on risk management and design features in potable and nonpotable water systems.

Relative to the overall scope of a construction project, implementing the requirements of ASHRAE 188 should not be a burdensome or costly proposition for building designers. But it is an important step in demonstrating compliance and managing risk associated with building water system projects. By doing so, building designers will confirm their commitment to public safety and building health. Those responsible for the design of projects relevant to ASHRAE 188 need to include implementation of the requirements on their building projects. A way to demonstrate compliance is to develop a project design compliance checklist, creation or revision of specifications, and drawing details to address legionella management and incorporated requirements of ASHRAE 188. The team can also develop a confirmation statement of design compliance for projects which have been developed under ASHRAE Standard 188.

Failures in implementation of risk management programs such as ASHRAE 188 during design and occupancy is where danger lurks. While having a plan in place is a step forward in managing legionella in a building, it is not enough to manage infection risk for building occupants. The only certain way to manage that risk is by performing environmental testing for legionella prior to and after building occupancy. This testing demonstrates that upon building turnover, building occupants are not being placed at risk for legionella, and your next project doesn’t become another example of Legionnaires’ disease associated with a construction activity.