Right under our noses is a stinky and challenging situation that can provide opportunities for pest management professionals (PMPs) — rat populations in sewers. Urban sewers and storm drain systems are a perfect infrastructural environment for rats because they perpetuate a monoculture through consistent temperature, abundant food and a lack of predators.
Sanitary sewers are an underground transport system for sewage from residential and commercial structures to facilitate treatment and/or disposal. Ones servicing industrial areas transport industrial wastewater. They’re operated separately and independently of storm drain systems that transport rainfall runoff and other water from city surface streets. Combined sewers transport sewage and storm water, and because of this, sewers can become potent reservoirs for rats. System defects or delayed maintenance problems support surface and subsurface rat populations.
Urban rodents are presenting a risk to public health because they’re associated with a number of zoonoses, according to the 2008 World Health Organization publication “Public Health Significance of Urban Pests.” Additionally, a rat’s strong instinct to burrow and gnaw damages the sewer and drainage infrastructure, particularly where defects exist.
Knowing the do’s and don’ts of a comprehensive sewer-baiting program provides an essential public-heath service and a recurring revenue opportunity. A successful program mandates comprehensive training, a detailed standard operating procedure (SOP), ongoing monitoring, appropriate equipment, and personal protective equipment (PPE):
- Do remember sewers are hazardous confined spaces, and all U.S. Occupational Safety & Health Agency (OSHA) training and safe work practices are required, including receiving required vaccinations against hepatitis, polio, tetanus and ongoing medical supervision.
- Don’t forget to always read and understand the product label directions when using rodenticides.
- Do check for the presence of flammable and/or toxic gases with a meter.
- Don’t forget sewer baiting is undertaken only when the manhole has been ventilated properly and gas meter readings record a clear atmosphere.
- Do place rodenticides per product label directions onto chamber benching using appropriate baiting equipment. If benching is absent, wires secured to a ladder and close to the access should suspend them.
- Don’t forget the quantity of bait placed, the specific location of the baited chamber, and all required regulatory information must be recorded accurately.
- Do recover, remove, reuse or dispose of any accidental rodenticide spillage, per the product label directions.
- Don’t forget that while conducting sewer baiting, the service vehicle rodenticide storage compartments must be securely locked.
Dr. Mitchell, D.O., Ph.D., M.P.H., B.C.E., a board-certified physician and entomologist, is principal technical specialist for PestWest Environmental, as well as PMP’s Technical Editor. He can be reached at firstname.lastname@example.org or 515-333-8923.
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