Wednesday, June 14, 2017

SEWER GAS (METHANE AND HYDROGEN SULFIDE) KILLS TWO LIFT STATION MAINTENANCE WORKERS IN PETAL, MS: the victims were Terry West, 45, and his son, Gage West, 20, both of Brandon

PETAL, MS - Two men killed Tuesday afternoon at a lift station in Petal have been identified.

Forrest County Deputy Coroner Lisa Klem said the victims were Terry West, 45, and his son, Gage West, 20, both of Brandon.

The two men are believed to have been overcome by methane gas while working at the lift station. Their actual cause of death is pending autopsy results, Klem said.

Mayor Hal Marx said the men were working for a company that had contracted with the city to do some work at the lift station on Short South Street.

"Our crew was on the scene with them most of the day," he said. "They told our crew they could leave and they were finishing up."

Marx said two of the three men working for the contractor were found unconscious in the lift station.

Emergency personnel were called. First responders were able to reach the men, who were about 15 feet down, and pulled them out.

Efforts to revive the men were unsuccessful.

Marx declined to give the name of the company the men worked for.

Carolyn McAfee, who lives next to the lift station, said she could not get to her home for about an hour while emergency personnel worked to get the men above ground.

"It was sad, just sad," she said. "My heart goes out to their families.

"Their husband, their son, their father left home this morning, and they aren't coming back."

She said once she learned it was gas that killed the men she became concerned about her health and safety.

"I was told it was odorless gas," she said. "I am concerned about my health and my neighbors' health.

"And is it safe for me to stay in my house tonight?"

Marx said he wanted to reassure residents they are in no danger.

"The problem was with the workers being in a confined space with the sewer water," he said. "It was not a gas leak."



Two people are dead in Petal after an incident on West 7th Avenue.

Two contractors working for the city were working on a lift station when officials believe they were overcome by methane gas, according to Petal Mayor Hal Marx.

Marx said the workers were 15 feet deep in the lift station at the time of the incident.

The fire department tried to save the men, but did all that they could do, according to Marx.

Marx said officials believe because the gas was odorless the workers were unable to react quickly enough.


PETAL, Miss. (WHLT) — A Brandon father and son were killed by methane gas while working at a lift station in Petal, according to officials.

Forrest County Deputy Coroner Lisa Klem said 45-year-old Terry West and 20-year-old Gage West were the two men who died.

We’re told the two men were working at a wastewater pump on Tuesday when the incident happened.

Petal Mayor Hal Marx said the men were working for a company that contracted with the city.

Marx said the two of the three men working for the contractor were found unconscious in the lift station. Attempts by emergency first responders to revive Terry and Gage West were unsuccessful. They were pulled out from about 15 feet down, according to authorities.

Marx said the problem wasn’t a gas leak but that the workers had been in a confined space with the sewer water.


What is a Lift Station?

DPW, Water, Sewerage

Pumping stations in sewage collection systems, also called lift stations, are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are sloped so that a liquid can flow in one direction under gravity).  Sewage is fed into and stored in an underground pit, commonly known as a wet well.  The well is equipped with electrical instrumentation to detect the level of sewage present.  When the sewage level rises to a predetermined point, a pump will be started to lift the sewage upward through a pressurized pipe system called a sewer force main or rising main from where the sewage is discharged into a gravity manhole.  From here the cycle starts all over again until the sewage reaches its point of destination—usually a treatment plant.  By this method, pumping stations are used to move waste to higher elevations.  In the case of high sewage flows into the well (for example during peak flow periods and wet weather) additional pumps will be used.  If this is insufficient, or in the case of failure of the pumping station, a backup in the sewer system can occur, leading to a sanitary sewer overflow—the discharge of raw sewage into the environment.

Sewage pumping stations are typically designed so that one pump or one set of pumps will handle normal peak flow conditions.  Redundancy is built into the system so that in the event that any one pump is out of service, the remaining pump or pumps will handle the designed flow.  In these days there are a lot of electronic controllers in the market designed specially for this application.  The storage volume of the wet well between the "pump on" and "pump off" settings is designed to minimize pump starts and stops, but is not so long a retention time as to allow the sewage in the wet well to go septic.

Sewage pumps are almost always end-suction centrifugal pumps with open impellers and are specially designed with a large open passage so as to avoid clogging with debris or winding stringy debris onto the impeller.  A four pole or six pole AC induction motor normally drives the pump.  Rather than provide large open passages, some pumps, typically smaller sewage pumps, also macerate any solids within the sewage breaking them down into smaller parts which can more easily pass through the impeller.

The interior of a sewage pump station is a very dangerous place.  Poisonous gases, such as methane and hydrogen sulfide, can accumulate in the wet well; an ill-equipped person entering the well would be overcome by fumes very quickly.  Any entry into the wet well requires the correct confined space entry method for a hazardous environment.  To minimize the need for entry, the facility is normally designed to allow pumps and other equipment to be removed from outside the wet well.

Traditional sewage pumping stations incorporate both a wet well and a "dry well".  Often these are the same structure separated by an internal divide.  In this configuration pumps are installed below ground level on the base of the dry well so that their inlets are below water level on pump start, priming the pump and also maximizing the available NPSH.  Although nominally isolated from the sewage in the wet well, dry wells are underground, confined spaces and require appropriate precautions for entry.  Further, any failure or leakage of the pumps or pipework can discharge sewage directly into the dry well with complete flooding not an uncommon occurrence.  As a result, the electric motors are normally mounted above the overflow, top water level of the wet well, usually above ground level, and drive the sewage pumps through an extended vertical shaft.  To protect the above ground motors from weather, small pump houses are normally built, which also incorporate the electrical switchgear and control electronics.  These are the visible parts of a traditional sewage pumping station although they are typically smaller than the underground wet and dry wells.

More modern sewage pumping stations do not require a dry well or pump house and usually comprise only a wet well.  In this configuration, submersible sewage pumps with closely coupled electric motor are mounted within the wet well itself, submerged within the sewage.  Submersible pumps are mounted on two vertical guide rails and seal onto a permanently fixed "duckfoot", which forms both a mount and also a vertical bend for the discharge pipe.  For maintenance or replacement, submersible pumps are raised by a chain off of the duckfoot and up the two guide rails to the maintenance (normally ground) level.  Reinstalling the pumps simply reverses this process with the pump being remounted on the guide rails and lowered onto the duckfoot where the weight of the pump reseals it.  As the motors are sealed and weather is not a concern, no above ground structures are required, excepting a small kiosk to contain the electrical switchgear and control systems.

Due to the much reduced health and safety concerns, and smaller footprint and visibility, submersible pump sewage pumping stations have almost completely superseded traditional sewage pumping stations.  Further, a refit of a traditional pumping station usually involves converting it into a modern pumping station by installing submersibles in the wet well, demolishing the pump house and retiring the dry well by either stripping it, or knocking down the internal partition and merging it with the wet well.

Everything You Always Wanted to Know About Sewer Gas...But Were Afraid to Ask

Question:    What is sewer gas?
Answer:    Sewer gas, at least that which causes an odor problem to the occupants of a house, is a mixture of inorganic gases created by the action of anaerobic (needing no oxygen) bacteria on sewage and sludge.  This gas can contain hydrogen sulfide, ammonia, carbon dioxide, methane, nitrogen, and hydrogen.

Question:    What makes it smell so bad?
Answer:    Almost always, hydrogen sulfide is the odor culprit, although ammonia may be formed in rare cases.  The rest of the gases listed above are odorless.  The odor threshold, the lowest concentration that can be detected with the nose, for hydrogen sulfide is somewhere between .001 and .01 parts per million (ppm), an extremely low concentration.  As an illustration, 1 ppm on a linear scale is one inch in 15.8 miles.

Question:    Can these gases harm the people who come into contact with them?
Answer:    Only under extremely unusual circumstances.  Although hydrogen sulfide is a toxic gas, it will not harm people at the concentrations that exist in a house with sewer gas odor problems.  Studies have shown that hydrogen sulfide has a depressant effect on the central nervous system in concentrations above 150 ppm.  This is 15,000 to 150,000 times the amount detectable by most people.  Not enough gas is generated in the sewers for concentrations to approach the dangerous level in the dwelling.
However, if a person were to enter a tunnel or deep hole that contained sewage undergoing anaerobic breakdown, there is a chance he could become poisoned.

Question:    How does it get into the house?
Answer:    The only way sewer gas can get into a home is if there is something wrong with your plumbing.  The most common fault in the plumbing system is untrapped drains, especially floor drains in the basement or utility room.  Since 1970, the City of Marion has had a plumbing inspection program and any houses built after that year should have no problem with a lack of traps.  If your house is older than that, your floor drains may or may not be trapped.
Other ways sewer gas can get into your home include:
  1. A dry trap.  If there is a trap in a drain line that is not often used, the water in the trap may evaporate, breaking the trap seal.
  2. A damaged trap.  Obviously, if the trap is cracked and allows the water to run out, the trap seal is again lost.
  3. A damaged drain line.  If the drain line is cracked or broken between the main sewer and the trap, there is nothing to impede the flow of gases through the crack or break in the line.  Also, a damaged drain line may allow sewage to drain into the basement or crawlspace under your house, and you may get a sewer odor from that accumulation of sewer.
  4. A damaged or plugged vent.  The vent system in your plumbing is designed to equalize the atmospheric pressure differences caused by wastewater flowing through the plumbing, and also to allow sewer gases to escape the plumbing system by venting them into the atmosphere above the house.  If this system has an untrapped opening inside your house, gases may escape through that opening.
If the vent is plugged or absent, those unequal pressures it was designed to eliminate may siphon the water out of the trap to such an extent as to ruin the trap seal.

Question:    How is it produced in the sewer?
Answer:    Hydrogen sulfide (H2S) is produced when the sulfate radical (SO4) is reduced to H2S and H2O (water).  This reaction can take place only when there is no oxygen or other oxidants in the microbial environment.  Studies have shown that H2S is not produced in fresh wastewater for two or three days, by which time it is normally to or through the wastewater treatment plant.
There are, however, some environments where hydrogen sulfide is produced in the sewers:
  1. The slime layer that coats the sewer pipe below the water line.  Although this layer can be only .040 of an inch thick, the three-quarters of the layer closest to the sewer pipe is so oxygen-poor that H2S is commonly formed.
  2. If any sludge has been deposited at the bottom of the pipe, H2S will also be formed in that sludge.
  3. If there is a problem in the sewer with flow (if it is plugged or partially plugged) so that the sewage cannot keep moving, the oxygen content gets to low that H2S can be produced in the sewage itself.
An important point to remember is hat all sewage systems, at one time or another, produce sewer gas.

Question:    What can be done to keep it from being formed in the sewers?
Answer:    If the hydrogen sulfide is becoming a problem in a very localized area (for example at the treatment plant or at a lift station), oxidizers can be added to the sewage to increase the oxidation-reduction potential.  These oxidizers can be oxygen, hydrogen peroxide, chlorine, permanganates, and others.
If the problem is in part of the sewage collection system, about all that can be practically done is to flush the sewers in order to increase the flow rate and remove any sediments or obstructions.  However, this can only be done to alleviate acute problems, and is not practical on a continuous basis.

Question:    What can I do to keep odors out of the house?
Answers:    The best answer is to find the problem with the plumbing system and have it repaired.  If the floor drains are untrapped, have traps installed.  It is probably not wise to simply plug the drain, because any water that enters the basement or utility room will have no place to go and possibly flood the room.  In any case, an experienced plumber will be able to find the shortcomings of the system and offer suggestions on how to correct them on an individual basis.

Question:    What, exactly, is a trap?
Answer:    A trap is a device made from a U-shaped section of pipe, tubing or tile which traps wastewater.  This wastewater then acts as a seal to prevent sewer gases from coming out through the drain opening.

Question:    How can I tell if my floor drains are trapped?
Answer:    Pour water into the opening (at least 2 gallons) and visually inspect by looking down the opening.  If there is considerable water standing (so that it fills the pipe), then the drain is trapped.  Check it again a couple of hours later to be sure the water hasn’t drained out.

If there is no standing water, then either there is no trap or it is located somewhere else in the line.  If there are odors present, pour some water into the opening and check for odors about an hour later.  If the odors are still present, there is probably no trap.