Cockroaches are very adaptable and cannot be totally eradicated. In fact, they are important ecologically. Roaches consume decaying organic material, which reduces the volume, so they play a vital role in nature. That having been said, we all want to keep roaches in the great outdoors and not in our homes.
The RWRD Conveyance Division operates the Vector (Roach) Control Program, which treats the Pima County sewer system to reduce the number of roaches. (Note that RWRD does not treat buildings or outdoor areas where these roaches sometimes migrate.) RWRD is the only utility in Pima County that treats for cockroaches. Further, most wastewater service providers in the U.S. do not proactively treat their systems as we do. This is a service that RWRD provides to its customers.
The Conveyance Division engages an outside contractor to treat manholes. We endeavor to treat each manhole once every two years (the amount of time the treatment is designed to last).
Manholes are sprayed with an insecticide mixed into a latex paint. This product is spray-painted on the circumference inside the entire manhole. Roaches will have to walk across this to leave a manhole. The product does not kill on contact, so after treatment you may see dead or dying roaches anywhere from around the manhole cover to the curb line, and sometimes beyond. You may notice heightened activity after treatment, as roaches are looking to escape the poison.