Fatality in Water Valve Manhole 7

[hairman]

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.

 

[saxon]

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

 

[CB2]

Hairman, KRS Services comments are very accurate and save lives. I will add that the &quot;confined space&quot; 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.

 

[fvincent]

hairman,

Can you please report any further results of your investigation?

thanks

fvincent

 

[hairman]

A sample of the 2&quot; 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, &quot;it is quite obvious that none of you have ever had confined space training&quot; or &quot;The company either did not educate it's workers or was not educated itself.&quot;

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 &quot;accidents&quot; 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.

 

[fvincent]

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

 

[KRSServices]

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

http://www.krs-services.com

 

[mmenarry]

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 &quot;hot works&quot; are involved, confined spaces can be more prevalent than at first glance.
Just my $.02
Michael

 

[fitz]

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 &quot;bags&quot; and see if they inflated.

 

[Pulpboy]

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?

 

[smile1]

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,

 

[vreng]

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.

 

[PUMPDESIGNER]

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

 

[KRSServices]

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

http://www.krs-services.com

 

[fvincent]

vreng

CO2 IS indicated in the gas readings...

&quot;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
&quot;

regards

fvincent

 

[saxon]

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

 

[fvincent]

saxon

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

regards

fvincent

 

[hairman]

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

 

[dicksewerrat]

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.

 

[labster]

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.

 

[hairman]

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