From the City of Oak Ridge Government:

Crews will be checking for any blockages in the sanitary sewer system using the Sewer Line Rapid Assessment Tool (SL-RAT) which operates with an acoustic sound wave. During this time, residents may experience unusual noises coming from sewer lines, which is normal due to the high frequency this tool uses. Public Works employees will have to access all sewer manholes, including those in backyards and fenced-in areas. Vehicles used will include city work trucks and John Deere gators used to carry inspection tools from manhole to manhole.