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Fatality in Water Valve Manhole
7

Fatality in Water Valve Manhole

Fatality in Water Valve Manhole

(OP)
Thursday August 14 at 12:00 a laborer entered a 17'6" deep by 6'diameter water valve manhole to operate the valve.  He entered without checking the atmosphere and died despite heroic efforts of his coworkers.  

Background:

The manhole had been installed three weeks ago as part of a new watermain installation.  The manhole had rubber boots sealing the water main pentration and mastic sealing each joint of the manhole.  The manhole was adjacent to a creek with the invert approximately 9 feet below the creek bed.

Approximately 2" of water had accumulated in the bottom of the manhole at the time of the accident.  The relatively small amount of water may have entered from the surface or possibly by condensation, however, I think that inflitration from outside is unlikely since the manhole was installed in wet conditions and a leak would have probably resulted in much more water.

The accident:

Two workers were excercising valves on a new water system primarily with keys via stop boxes.  One worker entered the manhole unbeknownst to the other worker.  The second worker realized his partner had entered the manhole and went to investigate.  The amount of time elapsed between the last time the workers had seen each other was approximately one minute.  As the second worker looked into the manhole, he heard the victum say that he had to get out.  The victum climbed to the third from the top step and fell back to the bottom of the manhole.

The top man called 911, and then called his coworkers.  Coworkers arrived within a couple minutes with a compressor and began blowing air into the manhole.  They also began monitoring the air with a four gas meter.  Oxygen initially registered 13% about 8 feet below the manhole cover.  By the time the emergency rescue personnel arrived (approximately 15 minutes) the air was reading around 20% oxygen.  Flammables registered 0% LEL, CO registered 0 ppm, H2S registered 0 ppm.

The rescue personnel donned breating apparatus and entered the manhole to recover the victum.  The victum was extricated from the manhole.  CPR was administered, however, they were unable to revive the victum.

Follow-up investigation:

Four hours after the incident, the manhole was reopened and the air was monitored.  8 feet below the cover, the oxygen registered 15%, 15 feet below the cover the oxygen registered 5%.  Flammables - 0 LEL.  CO - 0 ppm.  H2S - 0 ppm.

Questions:

1)What was the mechanism causing the oxygen deficiency?

2)How could the air become so deficient in oxygen so quickly after the manhole had been ventillated?

3)I intend to sample the water at the bottom of the manhole, what should I look for?

4)What other gasses should I try to get a meter to test for?

5)Any other ideas?

Thank-you for your time and input.
Harry G. Butler, P.E.

RE: Fatality in Water Valve Manhole

A tragic accident, and I want to express my sincere sympathy to the victim's family, his friends and his co-workers.

I'd say good training was the reason the other men didn't try to go into the manhole and rescue the first man.

My thoughts below are probably only some that have already occurred to you and people involved with the utility.

Perhaps the air blown into the manhole with the compressor didn't really displace the foul air completely and so later readings after getting the victim out of the manhole still represented what was in there to begin with.

I found an Internet page with a lengthy discussion of another death in a manhole, and the conclusion seems to be that it may have been the the man's own breathing that used-up the available oxygen and replaced it with CO2 at the bottom of that manhole.  The site is at:
http://www.jacpe.com/consult/case7710.html

Or, perhaps there is some kind of "air" flow entering the manhole from below--probably not likely, but I suppose a possibility, say from some biological process producing CO2.  Thinking of some gas entering the manhole makes me refer back to the Internet site which mentions the possibliity of CO2 from engine exhausts flowing into the manhole, displacing the air and remaining in the bottom of the manhole.  If that is the case, it could have been in there for days.

Corrosion of iron can use-up oxygen pretty rapidly, but there was probably not much exposed iron in the manhole.  

RE: Fatality in Water Valve Manhole

I forgot one other possiblity.  Perhaps the victim collapsed not because of the atmosphere in the manhole, but because he was ill.  He may have had undiagnosed heart trouble, or could have suffered a stroke.

RE: Fatality in Water Valve Manhole

I knew an incidence some 30 years ago when 2 members of a sewerage gang died after entering a sewer.  The first collapsed after entry and the second one died by trying to rescue the first.  Poisonous gas from the sewerage was responsible for their deaths.  The two apparently did not use the gas detector lamps provided as part of their equipment.  I fully agree with fitz that others did the right thing by not entering the manhole to save the victim.  

Recently I have to arrange inspection/maintenance work for a system of seawater culverts (total length 20km and not used for 16 years).  I had to specify the removal of covers 2 manholes upstream and 2 manholes downstream at the point of entry for ventilation at least for 24 hours before any work was permitted.  The work has been completed satisfactorily.

I couldn’t help with your detection work but let us learn from mistakes.  

I suppose there could be other denser gas displacing the oxygen in the manhole.  Natural ventilation does do much in your case unless the denser gases are forcibly expelled, as the water main manhole is a close environment.

RE: Fatality in Water Valve Manhole

I would agree with fitz. Generally a person requires 16 cfm fresh air (i.e 0.2 x 16 = 3.2cfm of oxygen) to keep exhaled CO2in control.

I agree with corrosion point also.

Check disolved oxygen in water.

Check for BOD.

I was told of similar incidence during start of my career and that is why I always check oxygen content before going inside tanks and reactors. Infact we have a confined entry work permit system which has some check points to fulfill before starting work.

RE: Fatality in Water Valve Manhole

(OP)
Regarding the Dissolved Oxygen in the standing water:  Today I took samples of the water at the bottom of the manhole.  What should I test for with respect to disolved oxygen, and what other characteristics should I test for to find clues to the mechanisms for depletion of the oxygen.

Incidently, the manhole is currently registering 2.3% oxygen at the bottom of the manhole and 18.1% oxygen 4 feet below the top of the manhole.

Thanks to everyone for their input.
Harry G. Butler

RE: Fatality in Water Valve Manhole

Is this manhole located near vehicle traffic? If so, the gases from the exhaust are heavier than the surrounding air and will seek a low spot, such as a manhole. If vehicles or any kind of combustible engine is nearby, test the air in the manhole for CO2 and CO.

RE: Fatality in Water Valve Manhole

First, you should check for CO2. Checking Biological Oxygen Demand (BOD) will give you an idea about the bio growth in the water. Generally, the DO in water is about 4 ppm but it can be maximum 14 ppm. Check for increase in DO.

I mainly suspect bacteria and the accuracy of your meter.

If the volume is 170 cu.ft (3.142x6x6x6/4, consider 6' height of the person), the oxygen content will be 170 x 0.023= 3.91 cu.ft and it is quite sufficient for one minute.

But CO2is heavier than O2 and this will not help much in diffusion.

I hope these vague thoughts will help you in someway or the other.

Regards,


RE: Fatality in Water Valve Manhole

There should be available a gas testing device to determine the actual gas which is displacing the oxygen. Try contacting a testing lab, one which is normally testing the output from a chemical refinery or power plant stack.

RE: Fatality in Water Valve Manhole


Should it be possible that a certain amount of de-gased CO2 (dissolved in water) could be leaking through valve sealing?

fvincent

RE: Fatality in Water Valve Manhole

I suspect CO2 or CO - probably from either a surface (vehicle exhaust) or subsurface source (biological or chemical activity in surrounding soil).  An autopsy should identify the mechanism and agent.  Once the mechanism and agent is identified, the source should be fairly straight forward.

RE: Fatality in Water Valve Manhole

3
I'm going to be blunt and to the point.  From your description this was a needless and totally preventable tragedy.  Car exhaust, CO, were not the cause of death, and I do not need to see the results of an autopsy for this.  The worker passed out due to oxygen deprivation and lack of training with respect to confined space entry.

While the previous threads are commendable, it is quite obvious that none of you have ever had confined space training, nor have ever had to purge a chamber, or enter one.  Having spent the early part of my career working in valve chambers and manholes, I hope I can strike a nerve and be able to prevent ever hearing of another accident in this fashion.

The oxygen near the surface was 15% - that is way too low, and a detector will alarm at about 19%.  5% is lethal.  The probable cause for the lack of oxygen is rust and corrosion.  The lack of a competant safety program, enforcement and training killed this employee.

Please people, there are many documented cases where oxygen deprivation killed people so institute a confined space training.  Ensure employees know how to properly purge the space.  Purchase the monitors for the employees to wear or carry with them into the confined space.  Most important....enforce the rules!  If you want information, or advice as to some of the municipal and public works safety programs I have set up, please do not hesitate to contact me.  I absolutely detest hearing about preventable accidents!

P.S.  The same holds true for lock out procedures when working around machinery (pumps, belts, etc).

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

Considering the following excerpt:
"
Coworkers ...began blowing air into the manhole...Oxygen initially registered 13% about 8 feet below the manhole cover.  By the time the emergency rescue personnel arrived (approximately 15 minutes) the air was reading around 20% oxygen.  
...
Four hours after the incident, the manhole was reopened and the air was monitored.  8 feet below the cover, the oxygen registered 15%, 15 feet below the cover the oxygen registered 5%.  Flammables - 0 LEL.  CO - 0 ppm.  H2S - 0 ppm.
"
I would guess a relatively high rate source of other gases was present...and not O2 depletion...

fvincent

RE: Fatality in Water Valve Manhole

The monitor should be detecting the presence of CO and  oxygen, among other things.  The importance is the fact that after four hours, the level of oxygen at the upper level was near lethal.  It does not matter that the O2 is reacting with another gas or being converted or used, the fact remains that the O2 levels were lethal.  It is a confined space, and that means the individual should have been harnessed, monitored and the chamber continuously purged with fresh air, period!  It does not matter whether this is a manhole, valve chamber, empty tank, cargo hold, lift station wet well, or large diameter pipe.  If the space is defined as confined, the employer and employees should have followed the rules.  If this employee was properly harnessed, it is possible that a rescue could have eliminated the fatality.

According to the thread, O2 was rapidly being depleted.  there could be any number or combination of biological processes that contributed to that depletion within the chamber.  Everybody, please use this as a wakeup call.  I've lost employees to stupid safety mistakes or oversights, you know, the "only if" or the "it would only have taken two extra seconds" mistakes, so I personally know what that organization is going through.

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

Are all chambers on potable water installations classified as confined spaces?

Before entering any chamber a risk assessment should be undertaken but the fact that it is a below ground chamber will not automatically classify the space as a confined space requiring gas monitoring before entry. (or will it?).

As a general safety requirement, regardless of whether the chamber is classified as a confined space, any person descending into a chamber should wear a safety harness and have a safety line.



RE: Fatality in Water Valve Manhole

Confined Space is defined as:

"An enclosed or partially enclosed space having restricted access and which, due to its design, construction, location, atmosphere, the materials or substances in it or other conditions, is or may become hazardous to a worker entering it or does not have an easy means of escape for or rescue of a worker entering it."

Confined spaces include, but are not limited to, manholes, chambers, new manholes, lift stations where a worker must access or egress via a ladder or steps and fresh air is not blown or circulated, wet wells, dry wells, tanks and vessels and large diameter water pipes.  A 2,000,000 litre underground reservoir can be classified as a confined space if the access and egress (through a hatch) is the method employed by the worker and will require constant atmospheric monitoring and a harness.

To accurately answer BRIS's question.  Pretty much all municipal water and sewer infrastructure can be classified as confined spaces because of their very nature of being buried, thence requiring manholes, chambers or deep pumping facilities.

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

(OP)
I have further factual information regarding the atmosphere in the water valve manhole.  On August 21, 2003, several safety experts returned to the scene of the accident with gas monitors including a CO2 monitor that had been factory calibrated.  Readings were as follows:  

2' below the cover  O2 - 16.5% CO2 - 6.7%  LEL - 0%
                    CO - 0 ppm  H2S - 0 ppm

8' below the cover  O2 - 1%  CO2 - 8.8%  LEL - 4%
                    CO - 0 ppm  H2S - 0 ppm

12' below the cover O2 - 1.5% CO2 - 8.7%  LEL - 5%
                    CO = 0 ppm  H2S - 0 ppm

Please refer to the original post of this string.

Questions:

1) What mechanisms are there that could have depleted the oxygen?  

2) Could processes that occurred outside the manhole (oxidation of iron in the soil or decomposition of organic material) have affected the atmosphere in the manhole?

Finally, regarding KRS Services comments, KRS has made some huge leaps to conclusions without knowing anything about the victum's company's training program, entry procedures, or enforcement program.  I am searching for some answers that may help companies understand the hazard and hopefully prevent this type of incident in the future.  So, KRS, if you have some information that could contribute to the questions at hand, please let me hear from you.  Otherwise, please start another string for your editorial comments.

RE: Fatality in Water Valve Manhole

hairman,

If I have offended you, I'm not sorry!  Regarding your thread, I leap to no conclusions nor was I being editorial.  You want specific reasons, the followup inquiry to the fatality will provide those.  You are making a very serious mistake if by learning that some specific process was responsible for the oxygen deficiency.  Every confined space is a hazard.  Did you know that a vault near a treatment plant can contain lethal amounts of chlorine gas, which is heavier than air?  If a worker had a monitor, it would be identified as a lethal environment without ever entering the space.

You want answers so that the accident can be prevented in the future, then begin by educating yourself and others about workplace hazards, in this case confined space.

It does not really matter that the oxygen levels in the vault were fatal.  The company either did not educate it's workers or was not educated itself and I'm not preaching here!

I do not have to be in the City or reviewing the company policy to know that a vault, any vault, is confined space and therefore a hazard.  That means a monitor is required at the very least.  If the worker was trained properly, it NEVER would have happened.  Now, you can either be proactive or continue to chastise me, but either way if you intend on ignoring the actual significant contribution to the fatality and seek out another explanation that would explain the science behind the lethal atmosphere, then you are setting yourself up for another disaster.

I have my certification in confined space entry, as did ALL my employees.  It only takes two hours and will save thier lives, regardless of industry.  Please insist or at least recommend that this training be instituted firstly, then worry about the actual whys later.

Finally, did you know that three employees were killed by oxygen depletion in a cargo hold of a ship in Vancouver, did you know that two employees were killed due to oxygene depletion in a live sanitary manhole, one was a rescuing firefighter, did you know that a worker was overcome in a cleaned water reservior due to the oxygen reacting with the cleaning agent?  I'm not trying to chastise anyone here but properly recognizing the hazard (vault - confined space) would have saved the employee his life!  

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

hairman,

As I have asked before:
"Should it be possible that a certain amount of de-gased CO2 (dissolved in water) could be leaking through valve sealing?"






fvincent

RE: Fatality in Water Valve Manhole

To All, An O2 level of <19.5% can result in will result in oxygen depletion in the bady resulting in fainting and possible death unless the victim is moved to an acceptable level of O2 in Air (>19.5% or <23.5%). As for the mechanisms of depletion there are many.

 In this instance, I would think that the depleted O2 level, the exertion required to climb the ladder resulted in an oxygen starved brain that resulted in passing out, the fall compounding the injuries and the time spent lying in the O2 deficient atmosphere resulted in brain deatH.

Hope this helps.
saxon

RE: Fatality in Water Valve Manhole

Hairman, KRS Services comments are very accurate and save lives.  I will add that the "confined space" need not be so confined to be deadly.  Know of a case where two workers were killed when working at the exit of a large strom drain culvert.  A low area and a very calm day, H2S at very low levels took them out.

be careful, be SAFE.

RE: Fatality in Water Valve Manhole

hairman,

Can you please report any further results of your investigation?

thanks

fvincent

RE: Fatality in Water Valve Manhole

(OP)
A sample of the 2" of standing water at the bottom of the manhole will be tested on 8/28/03 for organics and CO2.  I will post results as soon as possible.  

Question:  Is it possible for gasses to pass through the walls of a precast concrete manhole?

Thank-you all for your input regarding this issue.  I want to clear up one angle of this thread.  I agree 100% with most of KRS's points regarding the dangers of confined spaces and the need to test the atmospheres of confined spaces prior to entry, however, I take issue with his statements such as, "it is quite obvious that none of you have ever had confined space training" or "The company either did not educate it's workers or was not educated itself."  

I am a safety consultant and have trained thousands of construction workers in confined space entry including employees of the company that suffered the loss.  As  a trainer, one of the greatest frustrations is investigating  preventable "accidents" that have resulted from people who have been trained and choose to ignore their training.  

I am searching for the mechanisms for the oxygen depletion in this manhole so that I can communicate reasons to people in the field.  Too many trainers treat construction workers like dumb sheep, laying out simple rules without trying to connect with their intellect.  I believe that I can reach additional people through more in depth discussions of the reasons why it is essential to test the atmosphere in confined spaces instead of making the blanket statement that you have to test.  

So anyway, thanks again for all the posts, especially the ones that attempt to shed light on the specific causes of oxygen depletion or displacement in this manhole.

RE: Fatality in Water Valve Manhole


I still bet in gases leakage through the valve sealing...

If you could wrap the valve with a non permeable plastic and effectively my theory is valid, you would notice the plastic inflated.

The rate at which CO2 went into the confined space makes me think that the infiltration through the concrete walls is quite unlikely

regards

fvincent

RE: Fatality in Water Valve Manhole

hairman,

I completely understand your viewpoint now, and also understand why you took exception to some of my comments.  Had I known that it was yourself whom had provided the training, my education and training comments would have been specific to corporate enforcement and liability.  I cannot be certain as to whether you trained the worker who died, but it appears as though some of the training was not either understood or ignored by some of the senior staff or workers.  I had a supervisor killed on the job for no other reason than he chose to ignore the rules of lockout.  I won't go into details, but suffice it to say, the scene was not a pretty site and his death was witnessed by several school children.  Although the corporation was cleared of any wrongdoing or omissions due to our safety program and enforcement, it did not relieve the frustration and anger of his senseless accident.  Some of those emotions came through in my comments regarding your accident query.

I too, was a safety trainer but more importantly it was my responsibility as the Director, to ensure not only proper training but also enforcement.  I have used several audio visual tapes and videos to assist me.  It seems that trenching, confined spaces, lockout and shoring are the most difficult to train workers in because they do not buy into the premise that a danger exists.  The BC WCB has perhaps one of the best videos in confined space entry that I have ever seen.  It is shocking, informative and straight to the point.

Some staff buy in very quickly, others require additional training and experience, still others require the assistance of strict corporate rules and serious violation repricussions.  I have had a few where they actually require a near death experience.  I recall one employee whom when forced to wear the monitor in a sewage wet well, was shocked to hear it go off when the warning alarms went crazy once their cleaning work had commenced.  He never really thought about all his past headaches and diziness before.

In terms of the water valve chamber, I have found that oxygen depletion is usually the result of biological reactions with metal, water and other compounds in the chamber, including moulds.  In many chambers I have purged, oxidation with the metals was the prime cause because the air in the chamber is so stagnent and still.  Sewer manholes tend to have a small draft due to venting, unless the flows are extremely low.

One technique for training you may want to use is to put a monitor on one of those 25' or 30' (retractable) leashes for small dogs.  Turn it on, and let it go down to the bottom of a manhole or chamber of the trainee's choosing.  When it alarms...allow them to observe the depth, then having explained the dangers enquire about headaches, dizziness and nausea.  Our legislation requires that confined space be identified by a workplace hazard assessment.  Once identified, it is automatically monitored.  Some corporations follow the minimal guidelines, others go to the opposite extreme.    

Lastly, one of the hardest things is to get buy in from the corporate management in the form of acceptance of a safety program and more importantly enforcement and penalties for violation.  My policy was always strict....serious violations (trenching, confined space, shoring) always resulted in a three day suspension without pay.  5 days for supervisors and foremen.  These were always adopted by the managers and Councils once our solicitors presented a short seminar on liability and risk management specific to safety programs and Provincial regulations.

I would welcome the opportunity to swap notes and training techniques.  I have over 18 years of working in, supervising and directing public works operations, including safety, and could possibly provide you with some proactive pointers that have worked for me.

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

As a further point, confined spaces can also include any areas where ingress or exit is restricted- many plant room areas can be difficult to get in and out of due to pipework & ducting in the way. While atmosphere is a major confined space hazard, it is not the only one. Especially where "hot works" are involved, confined spaces can be more prevalent than at first glance.
Just my $.02
Michael

RE: Fatality in Water Valve Manhole

I don't think I have any sure-fire ideas about what is causing the oxygen depletion, but perhaps you could do a field experiment using some of what has been already suggested.  Maybe, based on location of the site, security, instrument availability and so-on, the suggestions are impractical, but I thought I'd throw my ideas in anyway.

First, blow displacing air on a long-term basis into the manhole to make sure its atmosphere is fresh.  Then try cleaning the manhole thoroughly to remove any water, mud or debris and leave it dry.  Then do what fvincent suggested, seal any penetrations with some kind of plastic wrap so you can detect inflow of gas by expansion of the wrap.

Then hang a gas probe in the manhole toward the bottom, climb out with it still there, and seal the manhole (more plastic sheet?) but leave the probe inside and watch the meter to see what happens to the various gases in the hole.  It would be nice to have a data recorder of some kind to do monitoring over hours or a day or so.

Then, after you have had a chance to review the data, put fresh air into the manhole again, see if there is any water in the bottom, and climb down to look at the leakage "bags" and see if they inflated.

RE: Fatality in Water Valve Manhole

Just a thought.  Maybe the aggregate or sand making up the concrete has iron in it and provided enough reaction to deplete the air.  Or possibly the manhole cover?  

RE: Fatality in Water Valve Manhole

It seems clear that KRSServices has provided the correct, if not concise, cause of the incident.  Certainly we all agree that a manhole meets the requirement of a confined space entry.  Certainly we all agree that oxidation occuring within the manhole consumed oxygen such that the space was rendered dangerous.  As for the oxidation reaction, it could be, and often is, as simple as vegitation or other carbon, iron, or a myriad of other elements.  

Can CO2 dissolve through the concrete walls?  Perhaps, though in this situation, the CO2 would have to be formed from oxygen, presumably supplied from the manhole, indicating a flux of both gasses through the concrete.....

I will stick with the original assessment.  

Best to all,

RE: Fatality in Water Valve Manhole

I agree that KSR et all miss the point of the original post.

No-one disputes that it is a confined space and that proper procedures may not have been followed.

The issue is what happens to the oxygen. The manholes and materials are new so corrosion using up axygen should not be an issue. Corrosion of metals does not occur fast enough to use up O2 in such short time frames as is being experienced.

CO or CO2 is not indicated in the gas readings. So O2 is being consumed.

I would check out the fact that the concrete is new and the calcification (or whatever the proper name is for the concrete setting up is) of the concrete is using up O2. This would occur at a decreasing rate for a long time, even beyond the 28 days normally allowed for concrete strength.

I would check with a cement/concrete chemical expert.

RE: Fatality in Water Valve Manhole

I have stayed out of this because I know nothing and can add nothing.  But gee, this stuff is scary.  I suspect you guys might have more of an audience than you know.

In 20 plus years of visiting people in the field I may have entered a confined space what 1 or 2 times, and if my memory is faulty maybe 4 or 5 times.  I am probably in more danger than anyone because of the infrequency and our customers have never warned us at all.

PUMPDESIGNER

RE: Fatality in Water Valve Manhole

Pumpdesigner,

I guess I write with a passion on subject because I spent most of my early career in confined spaces; manholes, valve chambers and tanks.  In the municipalities i worked for and in the oilpatch the rules are enforced.  If you were caught not following the rules, you were forced to look for another job, but that was really no big deal, we learned about the dangers and at least one foreman or supervisor had a sad story of an unfortunate friend or co-worker that did not heed the rules and was not alive as a result.  I must confess that I knew someone too, and I am very passionate about safety as a result.  I hope through this forum that others will take notice too.

Stay safe all!

Gene S.

KRS Services
www.krs-services.com

RE: Fatality in Water Valve Manhole

vreng

CO2 IS indicated in the gas readings...

"Readings were as follows:  

2' below the cover  O2 - 16.5% CO2 - 6.7%  LEL - 0%
                    CO - 0 ppm  H2S - 0 ppm

8' below the cover  O2 - 1%  CO2 - 8.8%  LEL - 4%
                    CO - 0 ppm  H2S - 0 ppm

12' below the cover O2 - 1.5% CO2 - 8.7%  LEL - 5%
                    CO = 0 ppm  H2S - 0 ppm
"

regards

fvincent

RE: Fatality in Water Valve Manhole

fvincent, According to your readings, at 2' below the rim edge you're already well be the O2 level needed to sustain life (>19.5%). Enter, and your dead. Have a nice day, if you live that long.

saxon

RE: Fatality in Water Valve Manhole


saxon

not my readings at all... Just participating of the forum

regards

fvincent

RE: Fatality in Water Valve Manhole

(OP)
Thanks to all who have participated in this forum.  Sadly, I am no closer than before to a satisfactory explanation for the depletion of the oxygen in the manhole.  I will post any further factual developments as they become available.
Regards,
Hairman

RE: Fatality in Water Valve Manhole

Ok we had a similar situation in Mpls. some years ago. Luckily the person was rescued.  This is what happened. The O2 was used up by the rotting organic matter around the manhole. Your manhole was placed in the soils below the water table. This exposed the material in the soil to O2. The organics in the soil began to decompose. The manhole is effectively allowing air to wick into the soils that surround this structure. As the organics break down in the presence of the O2CO and CO2 are released. the Manhole acts as an easier route for the gases than passing through the soils.
This is a terrible thing to happen. But it is a good training tool for the rest of the world.

RE: Fatality in Water Valve Manhole

We have this exact situation.  As a municpality, we have a valve manhole that is dry as a bone.  You could eat off the floor in the manhole.  We consistantly have an oxygen level that is below 10 percent.  I have researched this and found the following:

1. The primary reason for the low oxygen has to do with oxidation of the piping system reducing the free oxygen available in the atmosphere.  No I am not talking about pipes that are severly rusted, we have a new piping system that is in place.  A confined space training officer informed the that they often run into this situation in boiler rooms!  Simple oxidation of the piping system robs the atmosphere of free O2.

In your situation described, it is also very probable that the new vault installation has much to contribute to the situation.  Concrete that is curing takes a temendous amount of O2 from the atmosphere.

RE: Fatality in Water Valve Manhole

(OP)
The last post by dicksewerrat fits with the facts of the case if it is in fact possible for CO2 and O2 to be transferred through the concrete manhole.

The initial installation was in an area of organic soils and did require dewatering during construction.  It is also very possible that backfilling did place organics above the water table thus allowing movement of gasses through the soil (this has also been a very dry summer - lowering the water table.)

That brings us back to the question...Is it in fact possible for CO2 and O2 to pass through a concrete manhole that has been sealed at the joints with mastic?

Regarding labster's theory of oxidation of the piping system, I am doubtful of the possibility of enough oxidation occuring on new pipe in a three week period.  If that was possible, I would think that this situation would be much more common.  Also, I had understood that hydration of concrete did not utilize O2.  Please correct me if I am misinformed.

regards,
hairman

RE: Fatality in Water Valve Manhole

2
Words can't express the sorrow we all feel whenever we hear of such events.  I could not add to any of the sound advice about understanding the dangers and doing the training to eliminate the consequences of these hazards.  But I can remind you of a few items from recent engineering history.

Yes, gases do suffuse through apparently solid containments.  

We had an accident here in UK about 20 years ago caused by methane escaping from coal measures very deep below a river water transfer project.  Apologies to those who know better if I have miss-remembered some details. As I recall, the pipeline passed hundreds (?) of feet above the coal but it still captured the gas and transferred it to the terminal structure where it accumulated, despite measures to ventilate the chamber, until it got the chance to ignite.  The explosion demolished the structure and killed several people, injuring many more.  

I believe this was one of those seminal incidents that started to focus us on the subject of confined spaces and  reverse the general assumption that all would be ok. As a result of these tragedies we have very strong Health and Safety legislation in UK, but we still have a dreadful number of accidents every year.

In a completely different vein, we have problems in some parts of UK with radon gas being emitted from deep granite bedrock at sufficient rate to cause problems in housing sited above these strata.  One wonders why, if it will rise through huge depths of granite, it doesn't go straight through a few bricks and mortar? But it doesn't and special measures have to be implemented.

And on the subject of CO2, it is a very small molecule which can pass through membranes that will retain other gases.  When you blow up a party balloon, you will see that it deflates over the following period.  This is the CO2 component that is escaping, whereas the residual oxygen and nitrogen that have been puffed in are both retained.  If you use a pump and atmospheric air, the ballon stays up much longer.

I can recall press coverage of a number of fatal accidents that resembled the original tagedy described in this string. One was in the toe drain of a relatively new earthfill dam - no metals and not particularly deep as I recall.  I am pretty sure ambient CO2 was the culprit, but in some respects that is beside the point, as KRS has commented.  I do recall that at least one of the dead was the true freind who went into danger to help his co-worker.

I apologise again - to anyone feels these are trivial comments and out of context here - but I feel as strongly as KRS that we must learn all the lessons, and not let our thinking be confined by any one set of circumstances.  Explosive and toxic atmospheres can be as dangerous as asphyxiating atmospheres and Pumpdesigner's contribution shows how important it is to spread understanding of these very serious risks.

RE: Fatality in Water Valve Manhole

First let me say that this is a great discussion to be having.

In our municpality, we train in confined areas, that from the lay persons view would never suspect that there were atmosphere issues.  

Two months ago, we placed a manikin in our favorite valve manhole and called 911 for a moch training emergency.  Fire personnel responded, and started down the confined space without a permit testing of the atmosphere or SCBA.  They never suspected that there was anything wrong with the atmosphere.  They were shocked when we stopped the drill and monitored the atmosphere.

As a supervisor for confined space entry, I must state that KRS Services has stated the issues correctly. While not trying to rub salt in the wound I am concerned about a potential safety problem in the making...

We too try to identify what is causing a specific atmosphere to be dangerous.  Often times we are able to lay our hands on the problem and correct what may be causing the issues.  However, please note that I see the tendency in the work place to ignore the variables that may affect an atmosphere after a specific cause has been identified and corrected.  

The best example is sanitary sewer manholes.  For the first 10 minutes a crew is performing work the atmosphere is acceptable.  They tned to relax and go about there work with a little less concern.  Only to find out that the house up the street has just poured carpet cleaner down the drain.  Low an behold the atmosphere heads south.

While I applaud your efforts to identify the source, there is ALWAYS the need to monitor; and ventilate if the atmosphere is not acceptable. Ventilation should include a powered blower to insure that the worker(s) are receiving a fresh flow of air.  

Bottom line..it really is not the answer to know what caused the atmosphere issue, since what caused the problem 10 minutes ago may not be the same issue that kills you 10 minutes after the atmosphere re-checked okay.    

Regards

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