St. Paul's sewer department will begin conducting annual sewer systems safety tests on Tuesday, July 5 and continuing through the end of October. They will be testing north of University Avenue, between Snelling Avenue and Rice Street.

Crews will inject simulated smoke into the sewer system to find leaks and faulty connections that may need repair. The test lasts approximately 30 minutes at each location.

"The sewer safety test produces a simulated smoke, which may be seen coming from manhole covers, storm drains, roof vents and building foundations," said city sewer engineer Aaron Hass. "The simulated smoke is safe, and will not enter your home if it is properly plumbed and fixture traps contain water."

The simulated smoke is not expected to enter residents' homes, but if it does, they should open doors and windows and call the sewer safety testing crew at 651-238-0572. The simulated smoke should clear out rapidly once the building is vented, officials said.

For more information or to find out the testing area, visit stpaul.gov/sewertesting.

The city owns and maintains about 804 miles of sanitary sewer and 450 miles of storm sewer. Most of the sanitary sewer system was built between 1887 and 1958.