Sewer smoke test

George Hawthorn, right, places a smoke bomb in a blower placed over a manhole on East Woodlawn Street as his supervisor, Joseph Colley, looks on. The men, who work for RJN Group, were conducting smoke tests Wednesday on Harker Heights sewer lines.

Crews working for the city of Harker Heights began smoke testing sewer lines Wednesday in neighborhoods north of U.S. Highway 190.

Smoke testing helps locate defects, or cracks, in sewer pipes and shows the city where repairs need to be made. Defects allow rainwater to get into pipes and contaminate an otherwise sanitary sewer system, City Manager Steve Carpenter said at the Aug. 14 council meeting. So keeping pipes defect-free is essential to the longevity of the city’s system.

“A new sewer plant costs between $8 (million and) $10 million dollars, so if you can extend the life of your system it’s more cost effective,” he said.

RJN Group of Dallas was hired by the city to conduct the tests. On Wednesday, a crew of four RJN technicians combed a pie-shaped area of a neighborhood bordered by Roy Reynolds Drive, Pin Oak Drive and Farm-to-Market 2410.

The crew introduced smoke into the sewer system by setting off non-toxic smoke bombs at the mouth of manholes on either end of a pipeline segment. The smoke was then forced into the system with blowers powered by lawnmower engines.

“We’re isolating (the smoke), so we can introduce the most pressure we can without blowing toilets,” said Jonathan Kerr, RJN safety coordinator. “When we introduce smoke into the system, the smoke travels in the main pipe … goes up the service lines of each home and out the vent stacks of each home.”

As a result, smoke poured out from vent stacks of houses in the testing area, but the smoke was harmless and created no fire hazard, according to Kerr.

As smoke blew through the sewer system, the crew walked the neighborhood looking for breaks in the lines. Smoke pouring out a clean-out pipe in a yard and seeping through cracks in street asphalt indicated breaks, so the crew marked them with red flags.

Each defect area is photographed and mapped with a GPS unit, and then each defect is evaluated, according to Kerr.

“We’re trying to find where rainwater is going to get to the sanitary (system),” he said. “All this excess rainwater goes in and gets to the treatment plant and they can’t treat it, and they end up with overflowing manholes. That’s what we’re trying to find.”

The last time Harker Heights smoked tested its system was in 2006-2007, according to Public Works Director Mark Hyde. He said the testing is commonly done by municipalities.

“It’s pretty standard,” he said.

RJN Group will continue tests in northern parts of Harker Heights through Sept. 7. For more information, contact RJN Project Engineer Randy Brodner at (972) 437-4300 or the city of Harker Heights at (254) 953-5600.

Contact Kristi Johnson at or (254) 501-7548

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