The process of inspecting Bryan's city sewer lines began Thursday morning.
For the next three weeks contractors will be looking for cracked lines, missing manhole lids, and aged joints.
In order to detect problem areas, they will be sending harmless smoke through the city's sewer.
Places where the smoke raises will signal crews to locations they may need to work on.
Repairs made will help keep rainwater and groundwater from entering the wastewater system.