AUBURN — Smoke does not necessarily mean fire for the next three weeks but it could mean sewer leaks, according to Auburn officials.

Crews from Weston and  Sampson environmental consultants will begin testing Auburn’s sewer lines July 17, pumping thick, white smoke into the street manholes.

They expect the smoke will come out through subsequent manholes and individual sewer vents on top of homes and buildings.

They’re looking for smoke where it doesn’t belong — from yards and driveways, storm sewer grates and roof gutters. Smoke there could signal unknown sewer connections or broken lines.

“People can get some smoke in their house,” said Paul Greco, engineer with Weston and Sampson. “If that happens, we’re out on the street and we can investigate it.”

It’s the next phase of the city’s work to build a separate storm sewer system that runs parallel to the city’s sanitary sewer. Sid Hazelton, district engineer for the Auburn Sewer District, said the city sewer district finished its last separation project last summer.

“We’ve spent millions of dollars in the last several years, physically separating the storm sewer,” Hazelton said. “We have that done, and now we’re trying to pick up any leaks and drains that might be left over.”

Auburn sewer officials met Wednesday with team leaders from Weston & Samson, Auburn Public Works representatives, Deputy Police Chief Jason Moen and Acting Fire Chief Geoff Low to discuss the project.

John Storer, district superintendent, said his staff would begin notifying residents this week. The company plans to distribute yellow notes to residents the day before testing begins in their area. The notes describe what’s going on and what number to call with questions.

Some smoke could seep into homes from dry traps in forgotten basement drains or unused showers. Homeowners who find smoke in their homes during testing should contact the company, at 207 795-7641, extension 2112.

“We’ll be there looking for anything smoking out of the ordinary,” Greco said. “People need to be aware they will see us doing testing, they will see smoke in the streets. But they don’t need to be alarmed.”

The company is targeting three neighborhoods through Aug. 10. They’ll start on Center Street working north from Bradman Street on July 17.

Work moves to streets between Gamage Avenue and Court Street the following week and northern parts of New Auburn after that.

If time permits, they’ll test streets along Taylor Pond, neighborhoods north of Gamage Avenue and southern parts of New Auburn. The smoke testing is scheduled to be done by Aug. 10.

“The locations we chose were based on institutional suspicion of where we might have problems,” said John Storer, sewer district superintendent. Those are areas of the city where the district sewer meters record unexpected runoff during heavy rainstorms.

“We didn’t have the budget to test the whole city, so we decided to focus on the areas where we suspect the worst problems,” Storer said.

Engineer Adam Wilding said crews close off a manhole for the test, lighting a specially formulated zinc chloride candle. Each candle lasts about three minutes, creating enough smoke to fill up to 800 feet of sewer line.

Wilding said he walks along the street while the candle is going, looking for telltale puffs.

The white zinc chloride smoke is endorsed by the Environmental Protection Agency for this kind of testing and is designed to be safe and not leave stains or discolorations.

“Right now priority is letting people know where we are and what to expect,” Greco said. “If it does get into the house, it dissipates very quickly when the windows are open.”

[email protected]

Auburn Sewer Smoke TestingAuburn Sewer District will be forcing smoke into sewer lines in the yellow areas between July 17 and Aug. 10, 2012. Blue areas will be tested if the time permits.