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Sewer Smoke Testing Begins This Month
An employee of National Plant Services displays a lime colored vest their workers will be wearing during smoke tests of the city sewer lines. They will be in neighborhoods, in front and back yards this summer, looking for signs of the smoke escaping from sewer lines that would indicate a leak. Ric McGinnis/The News

Notices in both English and Spanish have been sent out to Riverbank residents about Sewer Smoke Testing that will happen throughout the city from July 8 through Sept.30 during the day from 7 a.m. to 5 p.m. This week there are door hangers also in English and Spanish that are giving people advance warning about the Public Works project.

The City of Riverbank Public Works Superintendent Michael Riddell explained that National Plant Services, Inc. (NPS) has been contracted to do the work. The contract has previously been approved by the City Council and funding has been secured through the Capital Improvement Project with funds that were set aside over several years.

The purpose of smoke testing is to locate defects in sewer mains and service laterals that allow rainfall runoff or ground water to enter the sanitary sewer collection system. They will produce smoke and with a fan set on the manhole it will be blown down the main sewer lines and travel up the laterals to the homes.

“Let’s say for instance a homeowner’s clean out cap is missing from behind the sidewalk then smoke will come out,” said Riddell. “We will know that. The purpose being that if smoke can get out water can get in and this is what we are trying to prevent. We are trying to make sure our system is sealed so nothing can escape but also so that we don’t get anything coming in that causes us to have to treat more water at that treatment plant than necessary.”

The smoke is nontoxic, non-staining, however does have a little bit of an odor. The public may see smoke around manhole lids and from the ground above the defects in sewer mains and sewer service laterals.

The smoke can get into a residence if there is a defect in the plumbing like a break in the line to the house or if the P-trap has dried up. There is a P-trap underneath the sink; toilet, shower and bathtub that are S shaped and hold water at the bottom that makes a seal. The water seal prevents gas from coming up from the sewer out of the drain. Riddell suggests that if the drain has not been used for a couple weeks then push water through it for a couple minutes.

“If you have a shower that maybe you don’t use very often or a bathroom that you don’t use the tub in at all if that P-trap gets the ability to dry out then that smoke can get in,” he noted. “So what we are telling people is to make sure if they have a drain that hasn’t been used for a while then run some water through it for a couple minutes. That will put the water seal in there and stop smoke from coming in.”

This project also includes surveying every manhole and checking for deficiencies, pipe size and pipe directions as well as a current map of the sewer lines. The cost of the project is approximately $695,000.

“Generally smoke testing shouldn’t run you over half a million dollars but this is not just smoke testing; that is one component, the manholes is another and the mapping is another,” stated Riddell. “So when they are all said and done we will have a very good idea of what shape our manholes are in. Then we can set and prioritize work. So we will have a very good plan and a very good map of all of our pipes and all of our manholes.”

With 37 years of experience in his field and doing a similar project for another city Riddell wants people to be aware of the smoke testing and coordinates with the fire department and law enforcement. There will also be smoke coming out of the plumbing vent roof stacks which is normal and not cause for alarm. As long as there are no defects in the plumbing and all drain traps are full of water there should not be any smoke indoors, he added.

“Inevitably somewhere along the lines we will probably put smoke in somebody’s house but it will be either because they didn’t bother to do what we are requesting to do with the P traps or they have a defect within their plumbing of their home which is a good thing for us to find because if they are getting smoke in their house they are also getting gases off the sewer,” expressed Riddell. “One of the byproducts of a sewer line or waste water line is hydrogen sulfide … if we find it we will let them know. The residence plumbing that is in their home and the lateral to their home is their responsibility. So if we find something we will let them know but they will need to get it repaired. We certainly will be there along the way if they need guidance.”

Crews with NPS will be in the area administering the Sewer Smoke Testing and the public should reach out to them if they see smoke in their house so that they can find where the problem is coming from. NPS will be readily identifiable with yellow safety vests that have National Plant logo on them as well as their vehicles.

For questions regarding the tests or health issues, call NPS at 562-755-3305.