Rodent Control for Large Urban Structures Such as Museums and More

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The former head of the General Services Administration’s pest management operation recalls the challenges associated with implementing one of the most complex rodent-proofing projects of his career.

September 14, 2022

Large, monumental structures in urban settings pose a host of challenging rodent control problems, requiring a significant amount of time, energy and resources to resolve.
AgnosticPreachersKid at English Wikipedia

In the spring of 1992, I had the privilege of initiating one of the most ambitious and concentrated applications of integrated rat management ever applied to a single, major edifice. A monumental federal building designed in the Beaux Arts style and completed in 1914, this six-story structure presently has 1.2 million square feet of floor space that is mostly devoted to offices, but also includes retail services and even a museum.

Its first large-scale renovation took place from 1929 to 1935. A second, even more sweeping renovation took place from 1990 to 1993. “Reconstruction” would be a more accurate word, since a substantial portion of the building’s interior was totally gutted prior to a spatial reconfiguration, installation of a new mechanical system and restoration of historically significant features. When the colossal structure was re-opened for business following completion of the first phase of this work in 1992, the General Services Administration (GSA) assumed responsibility for its operation and maintenance.

As with so many other neighborhoods in Washington, D.C., or, for that matter, any large city, the building’s immediate location has supported a dense population of Norway rats for as long as anyone can remember, so it was a foregone conclusion that they would make at least a moderate nuisance of themselves during the project.

Construction activities severely disrupt the lives of virtually all types of on-site fauna, but also present considerable opportunities in the form of unsecured food waste that tends to accumulate nearly everywhere. Harvesting this bounty inevitably leads to further investigation of the innumerable open passages that lead deep into the promising new harborage. Application of rodenticide to these protean habitats is generally as little as the construction company’s subcontractor can get away with, if there is any at all, so repeated nocturnal explorations of the building’s interior by growing numbers of inquisitive rodents is typically a low-risk endeavor.

Eventually, however, the unrestricted lawlessness comes to an end. The increasing human activity devoted to room-by-room installation of utilities, other support systems and business equipment — as well as the increasing sterility of the indoor environment as the work draws to a close — begins to drive out all but the most resourceful (or desperate) rats, at the same time that the structure’s outer shell steadily becomes less permeable. Those holdouts that are inevitably built into the finished product are slowly eliminated with traps and rodenticides as the pest control responsibility shifts to a different vendor (hired by the building operator) with a long-term, contractual stake in keeping things under control.

That’s what normally happens, anyway. In this particular case, schedules developed in meeting rooms far from the front line dictated that much of the building would be occupied by the summer of 1992, more than a year before construction of the 100,000-square-foot museum was concluded.

MONUMENTAL CHALLENGE. Populating new space prior to completion of work in closely adjacent areas is not unusual for large construction projects, but doing so with such a conspicuous expanse of the structure still open to the world was extreme. It led to a correspondingly extreme indoor rat crisis throughout the entire building, which was considered by all stakeholders to be entirely my problem to solve.

Since the property first appeared on my radar in late 1991, when a perceptive facility manager thought it might be a good idea to share the timetables for occupancy with me (intel through irregular and unofficial channels is essential for the effective functioning of any large organization), I actually had plenty of time to prepare for the consequences. But I also had only been on the job for slightly more than three years at that point, so the initial campaign that I organized was very much limited to a rote exercise in textbook IPM procedures.

There were lots of meetings and on-site walkthroughs to bring both contractors and government personnel representing multiple departments within several agencies up to speed on specific challenges, roles and responsibilities; an aggressive and ongoing outreach to both tenants and hard hats to make them aware of the situation (not that they weren’t already) and their vital role in practicing proper food storage and food waste disposal procedures (typically a monumentally futile message); and a massive deployment of rodenticide and snap traps by GSA’s regional pest management contractor, guided by intensive monitoring to identify where these measures were most needed. Physical sealing operations were underway to some extent in 1992, but were not really at the forefront of the overall effort — too many unavoidable, gaping holes still remained in the building’s shell.

However, as the year drew to a close, the last finishing touches were applied to the non-museum part of the structure, and the move of employees into this space was completed, it became depressingly evident that our campaign was being totally outmatched by the enemy’s vastly superior abilities. Rats, both adults and juveniles, were still running rampant through brand new occupied space that was decidedly remote from the remaining construction zones. The impressive body counts that inevitably accompany undertakings of this nature (about 25 dead rats tallied per week, on average) were offset by nightly observations of reinforcements scurrying across the streets to enter the building.

We were pretty much maxed out with the bait and trap installations (neither of which I’m particularly fond of using anywhere near an office environment), and, like so many other bumps in the road that arise within the hypersensitive world of federal bureaucracy, the issue had gained the concern of the highest executive levels. Clearly, it was time to take the rat-proofing component to a whole new level as well.

CHANGE IN PLANS. In collaboration with the GSA, NCR Alterations Branch, a plan was developed to methodically locate, record and secure every unsealed penetration throughout the building that could potentially serve as a rat access between rooms or floors, thus theoretically compartmentalizing the habitat to the point where it was no longer sustainable for rats to survive there.

To my knowledge, nothing like this had ever been attempted on such a grand scale. However, I was aided in selling the idea to upper management by a broad coalition of agency architects, engineers and facility managers who were not at all pleased by the abundance of holes they were finding in every part of the freshly completed structure that violated both code (e.g. fire-stopping) and good construction practice, and which, were it not for the rats, would be nonchalantly ignored for the sake of getting the renovations done on time.

The great sealing program, immediately dubbed the “hole patrol,” took much of 1993 to accomplish. Using one half-inch as a rough minimum, an employee of the construction company and a GSA field engineer systematically inspected the building’s anatomy for rat-vulnerable penetrations, documenting them on a punch list that indicated size, location, type, responsibility for repair and status of each opening.

As handheld computers did not yet exist, each penetration was laboriously marked on two centralized sets of floor plans. Probably the most numerous category of hole — and most popular with the rats, based on their droppings — was associated with the infamous (for pest managers) cabinet-enclosed, fin tube baseboard convectors, the ubiquitous method for economically heating large commercial or institutional buildings that requires an integrated hot-water piping system to run both horizontally and vertically along the perimeter walls.

Particularly, the risers of these systems are prone to pass through grossly oversized penetrations that — because they are almost always out of sight — remain unsealed for the life of the building. Other extremely common apertures were uncapped openings in the floor boxes of raised access floor panels. In addition, however, the rogue’s gallery contained every conceivable type of architectural gap, such as holes associated with fiber and telephone line riser closets, ductwork, conduits, cable trays, empty core drillings, expansion joints, misaligned ceiling tiles, doors, cafeteria booths, etc.

SUCCESS WITH A FEW CAVEATS. The project was both exhaustive and exhausting, and the last sentence of the Alteration Branch Chief’s final report in December 1993 had a certain goodbye and good riddance tone: “With the completion of this inspection and repair program, rat control has now moved from the realm of construction into an operations and maintenance effort.”

Indeed, at that point, concurrent with the museum’s completion and the building envelope’s closing, the indoor rat problem had ceased to exist. Almost 30 years later, despite the fact that legions of the rodents are still an overwhelming presence outside, a rat sighting inside the structure (other than around its internal loading dock) is almost unheard of. Nevertheless, any celebration of this achievement must be tempered with several caveats:

  • By significantly constraining their movements (and undoubtedly elevating their stress), the extreme sealing campaign — in concert with the baiting and trapping — undoubtedly contributed to the demise of the structure’s extensive interior rat population. It also was an invaluable public relations bonanza with GSA’s client agencies. However, as a fundamentally anecdotal event, it is impossible to tell how much longer the problem would have persisted after construction ended had the patching project never taken place. In general, Norway rats are rarely long-term denizens throughout the average public or commercial building, beyond certain vulnerable ground-floor facilities.
  • As a premier example of big pest control, it goes without saying that this exceptional exercise in rat prevention would be far out of the reach of most property-managing organizations. In fact, as a portrait of a young, ascending IPM program flexing its muscles during the twilight of a golden era in the federal government when such bold frontline efforts were possible to propose and even execute, it should be emphasized that support for funding of such a large “hole patrol” would be unthinkable in GSA nowadays.
  • The rats may be gone, but house mice are abundant throughout this building as in any other comparable structure in D.C., and probably will be for the foreseeable future. They fall below the threshold where feasible preventive measures involving access and food can effectively suppress them in large structures over the long run. Mouse IPM in the public and commercial sectors is typically dependent on old-fashioned harvesting (ideally by trapping) as its bread-and-butter core activity, rather than sealing operations or sustainable occupant cooperation with food storage and sanitation.