Risky Practices
The sad event reported below did not happen in the environmental remediation field; but it demonstrates a liability in certain practices that are being conducted in that field.
A 38-year-old arc welder died as a result of an explosion. The victim was working to repair a large garbage truck. The victim was arc welding some brackets on the back of the truck. He used a metal 55-gallon barrel as a worktable. Apparently the heat or sparks from the welding ignited residual vapors and/or material in the barrel, causing it to explode.
The explosion knocked the victim down, and started a fire in the immediate area. An employee found the victim lying on the ground, with exploded portions of the drum falling about him. There were secondary multiple explosions and fires. The fire increased rapidly and involved propane and acetylene tanks in the establishment. When the fire department and county sheriff arrived on the scene, the entire building was in flames. The fire was extinguished and the victim's body was found near the garbage truck.
Source: http://www.cdc.gov/NIOSH/FACE/stateface/ia/98ia045.html
In the cases of leaking petroleum underground storage tanks, we have instances where the petroleum reached groundwater. The illustration below depicts leaking petroleum resting as a pancake on the water table.
(LNAPL = Light Non Aqueous Phase Liquid; a liquid that is not water, lighter than water, and therefore will float; for example, gasoline.)
We insert monitoring wells into the aquifer as means to observe, inspect, and measure the groundwater conditions and thickness of the floating layer of petroleum. Here is an illustration of such a well.
We use bailers to collect groundwater samples from inside the wells. Here is an illustrated principle of how the bailer works.
The bailer is lowered down and through the face of the water. The water and what floats on it enter through the port in the bottom. When the bailer is lifted, the marble blocks the entry port and retains the sampled liquid in the bailer.
In the pictures that follow, you see the engineer lowering a bailer into a well, and when he pulls it out, there is a brown layer of petroleum resting on the water; much like the oil that floats on the water in the glass.
  
In the next picture, we see the engineer decanting the sample into a container.
http://www.etpproducts.com/index.html
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Where leaking petroleum products reach groundwater, California Code of Regulations demands removal of the free product to the maximum extent practicable while continuing to take any actions required for remediation of the site.
The Code warns that flammable products must be handled in a safe manner consistent with state and local requirements. |
The routine of corrective actions is a multi-phase progression. First we complete the definition of the extent of the contamination in the soil and groundwater; next, we study the applicability of various technologies to remediating the site and select the one most suitable. From there we proceed with detailed design, and continue to implementation of the technology and achieving the target cleanup levels.
It is not unusual for the preparatory steps to take a number of years before the brunt of the remediation begins. Therefore, where free petroleum is sitting on the water, regulators demand interim emergency actions for removal of the free product. The interim actions usually skim the petroleum that free-floats inside monitoring wells that were installed in the course of the investigation (the yellow layer in the diagram below):
http://www.great-white-north.com/PhaseII%20CA.htm
In many cases, the free petroleum is gasoline; and we observe that there are instances where risky practices are employed. These practices skim the gasoline with bailers like those described in the preceding sections, and then dump the gasoline in temporary containers. (Other practices skim the gasoline with submersible pumps or adsorbent socks.) The gasoline containers wait at times up to 90 days for collection. The containers are usually 55-gallon drums made of steel or high-density polyethylene; like these:
 
The storage of gasoline in such drums may lead to an internal atmosphere that provides an explosive air/fuel mixture. Given an ignition source, this mixture could result in a drum explosion or fire.
The important point to know is that these drums ARE NOT DESIGNED to withstand the pressure that is instantly building up when the mixture undergoes instantaneous combustion. The drums have no explosion relief vents or other devices that would automatically release the pressure. As the drums cannot endure the high pressure, something must give; either the clamped top will blow away as a burning projectile or the drum will explode.
The photo below captures the effects of a drum exploding inside a storage vault with the door open.
Click here for a movie clip documenting the experiment in picture and sound.
Acknowledgment: http://www.core-es.com/core_building-test.htm
Implementing engineering and administrative controls is a must to mitigate this risk of explosion. Unfortunately, there are cases where the needed controls are not implemented, because of either unawareness or reliance on “luck.”
Here are illustrations of what one might see in sites where storage of skimmed gasoline is practiced:
One may see drums staged in an orderly manner like this,
haphazardly like this,
or even abandoned like this,
Where such gasoline drums get together, we need just one to explode to start a chain reaction of a lightning-speed propagating blast (the illustration below is of a nuclear chain reaction but serves well to demonstrate the point):
Storage of gasoline or any gasoline-like flammable substance in a fashion resembling any of the above examples could present a potential of risk to life and property.
There are strict fire and safety codes pertaining to the storage of flammable substances. If one should store gasoline in drums in a fashion resembling the examples above, they could be in violation of the codes and fire safety ordinances; but even more seriously, they might be putting fellow workers and innocent public in harm’s way.
 
I have no hard statistics on casualties from explosions of gasoline containers; however, from experience of the past 20 years I know of four fatalities. As a reality check, one observes that in cleaning up the environment we work with risk models that aim at the reduction of environmental contamination risk to one death in a million in 70 years. Taking an arbitrary guess of 10,000 workers in the gasoline storage field, we get 4 deaths in 10,000 in 20 years; which translates to 1400 in a million in 70 years (and this ratio results from the only 4 cases that I personally am aware of).
It means, that in environmental corrective actions, when one places skimmed gasoline in non-protected drums, they do it to protect one in a million from the toxicity of gasoline but have just increased the risk 1400 times for others to get killed from explosion of these drums. (My calculations are in orders of magnitude and solely intended to demonstrate the deadly potential of the practice.)
Some of the needed safety features would likely involve:
1.) Visual signage:
  
2.) Containment buildings:
http://www.warehousesupplyonline.com/view_product.cgi?product_id=2072
3.) Installation of and proper training in the use of fire extinguishers:
http://www.utsystem.edu/ohr/neo/safety/safety.htm
4.) Fencing of the storage area:
For me, I would stay away from storing the skimmed gasoline in drums. There are age-tried safer practices. I would employ one or combination of the following:
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Vacuum truck employing a plastic tube as suction “stinger.” The stinger is inserted in the well down to the face of the floating gasoline and “slurps” it much like a child slurping a drink. The gasoline gets into the truck and is hauled away to the recycling facility. On a comparative scale of risk of 1 to 10, with 10 being the highest, I would place this practice at a most benign level of 0.5.
 
Inside the well, the slurping action looks like this:
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My number two contender, and only if the circumstances should force storage of the skimmed gasoline on the premises, would be a temporary, bullet-proof, explosion proof, concrete-vaulted tank rated at 2 to 4 hours of fire resistance, equipped with explosion vent and other integrally mounted safety features. On the above risk scale, I would rate this option at a slightly higher risk of 1.0, only because of the handling of the gasoline between the point of suction at the well and point of discharge to the tank. The tank would be sized at 500-1000 gallons and the contents evacuated into a vacuum truck periodically.
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The last on my list would be a properly designed, permitted and constructed drum storage compound; and even then, I know that I am going to lose some sleep during the project. I would rate this option in the upper 8 to 10 level of comparative risk to be used as the last resort.
This letter is offered as a service to the community with the hope to instill greater awareness in the subject matter.
Note: All links in this letter are provided as grateful acknowledgment to the sources from which they are borrowed. Various products are presented in this letter for illustration only. This letter does not endorse any product and the writer has no business relations with the manufacturers or distributers of the products presented. |
