Rodent Control At Construction Sites

Control of commensal rodents as part of construction/demolition projects is rarely planned and implemented comprehensively and there is no standard reference guide. Biologists involved with rodent control typically are not trained or experienced in engineering and construction trades; this is also the case with PCOs who are asked to bid on these projects. Thus, inadequate focus has been given to this subject historically and much greater focus will be needed in the future given construction trends nationally.

When rodent control is part of a construction project, limited or superficial requirements and understanding are common. As a result, abutting neighborhoods and construction workers can be impacted from displaced or colonizing rodents. Also, new structures are sometimes completed with rodents built into them because rodent control and sanitation were inadequate during construction. This leaves the owner with a rodent problem right from the start of building occupation.

There are many specialized aspects of rodent control for construction/demolition projects. They include understanding the infrastructure of cities, construction methods and scheduling, local or state construction regulations, contract specifications and the neighborhoods adjacent to the work site. An IPM approach should be implemented for PCOs involved in this work. However, it must be dynamic because by their nature, these projects create an ideal habitat for rodents.

Our Aging Cities. The aging of urban infrastructure is a growing phenomenon in the United States. As a result, older cities are increasingly struggling with the need for rehabilitation or replacement of municipal infrastructure, ranging from sewer systems to roadways and sidewalks. Abandoned properties, both residential and commercial, symbolize the aging of cities and decay that can precipitate even greater neglect and sanitation problems. Structures built above ground may be prioritized for repair, in part because of aesthetic reasons, while underground (out-of-sight) structures may be left to decay until a crisis occurs (such as a broken water or sewer pipe).

In addition to aging infrastructure, many portions of the U.S. are experiencing unprecedented urban sprawl and economic growth. This can include revitalization of downtown districts, construction of hotels and convention centers, highway and subway construction, development of office towers and the spread of residential housing. With this economic growth, there comes a need for shopping centers, commercial districts, restaurants and utilities to support local economies and populations.

Ideally, rodent control measures would be included during land-use planning and urban design, thereby limiting the potential resources (i.e., harborages) for rats and mice. Although this is the most proactive form of rodent control, it rarely is used when structures and cities are designed. As cities are rehabilitated, rats and mice may be inherent to the existing infrastructure when demolition and new construction begins.

The Need for Mitigation. The term "mitigation" is used in construction planning to describe actions that will limit impacts to abutters and communities. Noise, traffic and dust control are examples of mitigation topics. At times, rodent control may be included for a particular project, but most often it is not (although it should be).

Local municipalities should be requiring rodent control for many construction and demolition projects. Keeping construction sites free of "vermin" is an enforceable Occupational Safety and Health Administration (OSHA) requirement and it has been identified as part of management practices during remediation at hazardous waste sites.

There are three time periods when rodent problems can occur during construction/demolition projects: 1) when a project mobilizes, rodents can be dispersed with initial excavation, clearing/grubbing or demolition; 2) during the project, rodents can quickly colonize the work site because of exposed soil, debris, fencelines, trailers and food from workers. As rodent numbers increase and construction activities shift within the site, rodents may be dispersed to abutting properties; and 3) during de-mobilization, when debris and fencelines are removed, dispersal of rodents to adjoining areas can occur with loss of cover and on-site food sources.

Specifications. Well-written specifications by the project designer, defined regulatory requirements and contract compliance are key for effective rodent control. If a construction contract contains reference to rodent control, commonly the specification has been written by an engineer or has been copied from text written decades earlier. It is not unusual to find specifications so out of date that they require the application of unregistered rodenticides. Some municipalities may require rodent control, but oddly some only require it for demolition and not for construction.

Municipalities should define the regulatory requirements for a rodent control program. This should include all major construction projects and demolition projects (and any other project located where the potential for impact is anticipated). Rodent control must be implemented with adequate time to ensure that rodents are eliminated by a pest control operator before construction mobilization and site disruption begins.

Although PCOs can’t control all of the activities at a construction site, they should recommend that municipalities require construction contractors to acquire permits and show written proof of a pest control contract. Also, rodent control should be maintained throughout the work duration and until all equipment and materials are removed. Sanitation measures should be required as well.

Contract specifications should identify several tasks to be performed by a PCO, tailored to the particular situation. Basic tasks include: 1) a documented baseline (pre-construction) survey of rodent activity and sanitation on the proposed work site and observable areas nearby (within 300 feet of the site; up to 1,000 feet for a major project); 2) poison baiting or trapping so the site and nearby public areas are rodent-free prior to construction/demolition; and 3) installation of monitoring (bait/trap) stations at the site perimeter and trailer/storage locations. Subsurface (manhole) baiting may be necessary if utility systems will be impacted. Catch basins in bordering streets should be inspected and baited if necessary.

Once construction begins, the PCO should be on site weekly to inspect for sanitation conditions and rodent activity — more often if activity is found. Inspection and baiting records should be maintained for the site and adjacent areas and the program adjusted to match construction sequencing.

In addition to the tasks specified for a PCO, there should be a specification for site sanitation. It should require that contractors (and subcontractors) provide and use rodent-proof refuse containers, conduct site cleanup for litter daily, properly contain refuse, remove unnecessary debris piles and control weeds and other undesirable vegetation.

Strategy. The goal is to resolve sanitation and rodent problems on and around the work site prior to the start of construction/demolition. This prevents displacement and reduces the likelihood of subsequent colonization. The distance that the program should stretch must be tailored to the type of construction environment and the likelihood for rodent movement to and from the work site. Locations near food establishments and residential housing will need a wider ranging program.

It is critical to document the level of rodent activity, sanitation problems and actions taken at all stages of program implementation. It may be necessary during construction to defend against false claims of impacts as expressed by residents and businesses; such claims can be common and expensive to resolve when the control practices, outreach efforts or documentation have been inadequate. Conflicts can be avoided by talking with abutters about problems before construction begins.

The construction contractor, through his or her subcontracted PCO, should be responsible for rodent problems within the work area limits and public accessible areas adjacent to them. Responsibility for rodent control on private properties should remain with those owners, except in the situation where construction activities have actually caused an impact. In some cases, however, it may be necessary to assist an abutter in solving a problem because the rodents could become a source to infest the work site.

The PCO should establish communication with the local housing or health authorities and share observations on sanitary code violations on private properties. Ideally those agencies would address private property issues and facilitate public participation through outreach and code enforcement concurrent with the construction program.

A minor construction project may require a 10-day initial effort, while a major project can require four to six weeks of rodent control before construction should begin. Pay items can be defined as a lump sum to establish the rodent control program and a monthly unit price thereafter for maintenance. Complaint calls and other pest control problems (e.g., insect) can be handled on an hourly rate basis.

Work Site Sanitation. Several sanitation actions should be incorporated into the construction contract. Heavy-duty refuse containers (e.g., 44-gal.) with domed lids that have an entrance flap are ideal (lined with a plastic bag) for locations where construction workers will congregate and eat. These should be emptied daily into a secure dumpster unit (e.g., 4 to 6 yard) with a tight-fitting lid (and a drain plug if a drain exists). Construction debris should be stored separate from food and food-related litter and discarded into a roll-off container (e.g., 30 yard). Storage and pickup of refuse must be adequate for the amount of material generated. Lunch and break areas should be consolidated.

Erosion control is a common aspect of construction and described by contract specifications and permit conditions. Hay/straw bales may be specified along the limits of disturbance and they can be attractive to rodents as harborage. Bales may be stockpiled on the site or thrown in a heap following the end of their usefulness. Contractors should be required to promptly discard old and unnecessary bales.

Catch basins covered with debris and soil can provide burrowing and protected habitats for rats. This can occur in adjacent streets and along truck routes and loading areas. Catch basins should be kept clean and functional and be adequately protected from soil spillage and turbid runoff. Street sweeping should be maintained to help keep soil out of catch basins.

Work site perimeters typically are fenced or barricaded and trash can accumulate on both sides. The construction contract should specify cleanup of perimeters daily. Large debris should not be allowed to pile up along site perimeters and provide harborage.

Problems and Solutions. Closely inspect and monitor work site perimeters. Fenceline or edge environments are most likely to be colonized. Jersey barriers (concrete barriers) around work sites can provide harborage and protected runways underneath, but also can be used as protected locations for baiting. Jersey barriers and fencelines adjacent to dumpster areas, residences and restaurants will be at greatest risk of infestation. Monitoring can include use of non-toxic bait suspended by wire at the end of jersey barriers, flagged for easy identification. Landscaped areas next to work sites should be closely monitored as well.

Place and secure bait stations strategically such as in corners of work sites, near trailers and lunch break areas, in storage areas and near sensitive abutters. It is inappropriate to place numerous bait stations at systematic intervals along site perimeters. Bait stations on an active work site are often destroyed by equipment and thus construction personnel should be informed to avoid them. The PCO should track changes in site fencing so that bait stations are not lost or left unsecured.

Be predictive of potential movement routes. For example, sites abutting waterfront edges need sentinel monitoring stations to intercept rats moving along waterfront edges. Use engineering drawings to evaluate the subsurface environments and the need for control measures there. Closely track and know the construction schedule and sequencing.

Temporary (metal) street decking over a cut-and-cover excavation can provide harborage when the decking is not well secured and a gap exists between it and the street. This allows access to soil in the underneath trench. Any decking placed for an extended period must be properly secured. Exposed soil can be a limiting factor for rats in urban areas and thus if left undisturbed, it may be colonized.

Shift control measures and monitoring seasonally. The skirt underneath a construction trailer and storage trailers can be particularly attractive to rodents during cooler months of the year. Anticipate more rodent activity during late spring and fall months as a result of seasonal breeding. Intensive trapping colonization, breeding and dispersal events that can occur.

For demolition projects, rid the building of rats and mice prior to demolition and any remediation work (e.g., asbestos); this may take one to three weeks depending on the structure. Shift control efforts to the site perimeter once demolition is about to begin. Major demolition projects can result in dispersal of rodents through utility systems to other buildings if subsurface control is not comprehensive.

Also know the work site’s safety requirements. This can include a hard hat, work boots, safety glasses, safety vest and ear plugs. Work sites can change quickly, so it’s important to check in before entering the site and follow all safety procedures.

Communication. Health and safety plans are written for construction and demolition projects. Rodent control and sanitation should be identified in them, including communication about rodent problems. The project safety representative can use a "tool box" talk at the beginning of a work shift to highlight the importance of site sanitation. Construction workers should be asked to report any observation of rodent activity so the PCO can target control measures promptly.

Communication and positive public relations should be maintained with abutting residents and businesses during the project. An effective rodent control program can be a positive point — or a major disaster — with neighborhoods and the news media when poorly implemented and ineffectively explained. A good PCO for construction is skilled at public relations.

Public complaints should be handled as soon as possible, always within 24 hours. For large projects, there must be an established communication network for receiving complaints and notifying those who can take action.

Projects will have a construction superintendent and field engineers. There also will be a contract administrator identified for managing the pest control subcontract. The PCO must coordinate effectively in the field and build a team relationship with the field engineers.

Summary. Rodent control for construction and demolition is a challenging process that can require adjustment and flexibility with each change in construction operations. It is not about managing a static environment. Success is predicated on anticipating how that environment will change during the course of the project and strategically implementing a well-designed plan.