Sewer News – Sewer Gas – Sewer Repairs

by Vince Bushell Our sewer system is under ground, out of sight, and usually out of mind. Until something bad happens or something is different that we notice or when we find out how much this infrastructure costs. Some Riverwesters have been noticing a “smell” along the river and possibly in some homes.  If you smell sewer gas or a plasticy smell in your home be sure to read the advice at the end of this column. Sewers create sewer gas, as part of normal operation, although you should not smell it in your home. It is not a pleasant smell.

In November the Michels Construction was hired by the City of Milwaukee to repair a large sewer main that follows the Milwaukee River along Riverboat Road and continuing upstream beyond Locust Street.  The municipalities own most of the sewer pipes. MMSD, the Metropolitan Milwaukee Sewerage District is in charge of the larger collection tunnels and overseas the sewerage treatment plants.

Michels uses a method developed in the mid 1970’s called Cured In Place Piping or CIPP. This method was used along Humboldt Boulevard a few years back and Alderman Kovac said it was used recently along Newberry Boulevard. Kovac said some residents complained about an odor coming into their homes. This odor was not the regular sewer gas but a result of the CIPP process. A reinforced felt liner is pulled through the damaged sewer pipe after it has been cleaned. A resin, styrene, is sprayed on the felt and activated with heat (steam or hot water). The off gassing occurs during this activation process and it disperses quickly.  I did smell it strongly on the day the styrene was activated and was able to notice it along the lower river trail near sewer manholes, a day later.

As Kovac noted, the reason we are using this method is because of the cost benefit of the process. CIPP does not require digging up the streets, which would have many issues related to cost and pollution. CIPP is fast, less disruptive and much   less expensive than digging up streets. 

This process is not only used for larger collector sewer lines. It   is being used in Milwaukee on sewer laterals between homes and businesses and the city pipes on the west side of the city. You may see this in-place repair of sewer pipes to homes happening in additional areas of Milwaukee soon.

The sewer laterals are a source of infiltration of rain and ground water in the   sanitary and combined sewer system.  This adds to the amount of water that is handled by the sewerage treatments process and is one of the causes of sewer over flows and basement back ups.  This infiltration and inflow of water into the system makes efforts to control flooding and protect our waterways from pollution more difficult.

Below is an article about sewer gas from the Wisconsin Division of Public Health. If you smell sewer gas, or during these repairs, styrene odor, this is an indication that you may have problems with your sewer lines, traps and/or vents in your home. 

What is sewer gas?

Sewer gas is a complex mixture of toxic and non-toxic gases that can be present at varying levels depending upon the source.  It is formed during the decay of household and industrial waste. Highly toxic components of sewer gas include hydrogen sulfide and ammonia.

Sewer gas also contains methane, carbon dioxide, sulfur dioxide, and nitrous oxides. In addition, chlorine bleaches, industrial solvents, and gasoline are frequently present in municipal and privately owned-sewage treatment systems.

How are people exposed to sewer gas?

Sewer gas can enter a home through a floor drain, from a leaking or blocked plumbing roof vent, or (if the gases are in soil adjacent to the house) through cracks in foundations.  Sanitary and farm workers can be exposed to sewer gas during the cleaning and maintenance of municipal sewers, manure storage tanks, and home septic tanks.

What are the effects of exposure to sewer gas?

The principal risks and effects associated with exposure are:

Hydrogen sulfide poisoning. Exposure to low levels of hydrogen sulfide causes irritation of the eyes and respiratory tract. Other symptoms include nervousness, dizziness, nausea, headache, and drowsiness. This gas smells like rotten eggs, even at extremely low concentrations.  Exposure to high concentrations can interfere with the sense of smell, making this warning signal unreliable. At extremely high levels, hydrogen sulfide can cause immediate loss of consciousness and death.

Asphyxiation. High concentrations of methane in enclosed areas can lead to suffocation as large amounts of methane will decrease the amount of oxygen in the air. The effects of oxygen deficiency include headache, nausea, dizziness and unconsciousness. At very low oxygen concentrations (<12%), unconsciousness and death may occur very quickly and without warning.  Sewer gas diffuses and mixes with indoor air, and will be most concentrated where it is entering the home. It can accumulate in basements.

Explosion and fire. Methane and hydrogen sulfide are flammable and highly explosive.

How can I avoid being exposed to sewer gas?

Flush floor and sink drains with water to prevent the traps in pipes to the sewer from drying out. (If you have an unused toilet in the basement add a bucket  of water to fill the trap in the fixture).

Occasionally check the roof plumbing vent for blockage from debris such as leaves or bird nests.

Never enter a municipal sewer line, manure-storage tank or any other large storage tank without proper training and equipment.

What should I do if I suspect a problem?

First, following the odor, try to locate the point of entry, such as a basement floor drain.  Check for a blocked rooftop plumbing gas vent.  By adding water to the floor drain or removing debris from a roof plumbing stack vent you may be able to prevent sewer gas from entering your home.  In the unlikely event that a leak in gas vent plumbing is behind walls, a plumber may be needed to find and fix it.  Some local public health departments may be able to offer home inspections.

Symptoms of headache, nausea, dizziness, or drowsiness may indicate exposure to an odorless gas like methane or carbon monoxide, or to hydrogen sulfide, which smells of rotten eggs.  Persons experiencing severe symptoms should seek immediate medical care.

If you suspect that high concentrations of sewer gas have accumulated in an enclosed space, you should evacuate the area and contact the fire department for assistance.  Avoid creating an ignition source such a spark from an electrical appliance, match, or cigarette lighter.