This is the second in a short series of posts about what
probably should have happened in Charleston, WV a little over a week ago now
when a spill of Crude MCHM shutdown the water supply of well over 100,000
people for most of a week. The earlier post (listed below) I described how the
water company could have kept the water out of its system in a perfect world.
Of course, in a perfect world, the material never would have
gotten into the Elk River in the first place. Let’s take a quick at what a
perfect chemical company would have done to ensure that the product never would
have made it into the river.
Materials of
Construction
The first thing that anyone should look at when deciding to
do bulk storage of any chemical is to determine what the proper materials of
construction are to be used for the tank walls, the piping, the gaskets and various
seals; all wetted surfaces. You don’t want materials that will react with the
chemical or will be corroded by the chemical (actually the same thing, just
with a slightly different focus). If the chemical acts as a corrosive to the
material that is used to construct the tank then sooner or later there will be
a hole in the tank.
The easiest way to determine the proper materials of
construction would be to look it up in one of the standard industry references.
Many common chemicals have listings of compatible materials on-line. For less
common materials it may be as easy as contacting the manufacturer, particularly
the larger ones with good engineering departments. The tried and true method,
however, is coupon testing. You take a sample of the chemical and a sample (a
coupon) of the material you want to use to make your storage tank. You put the
coupon in the sample for a lengthy period of time. When the time is up you pull
the coupon out and closely (with a microscope) examine the coupon for signs of
pitting or corrosion. If you don’t find any such signs, you are good to go. If
you do, try something else.
Freedom Industries bought their Elk River terminal with the
tanks already in place. I don’t expect that you can find Crude MCHM in any of
the on-line sources and their supplier (I’m not sure who their supplier is) may
not have been able to tell them. With already existing tanks on site, I would
suspect that there was no coupon testing done. Someone made their best educated
guess and said that the Crude MCHM doesn’t look like it would be too corrosive,
or maybe they didn’t even think about materials of construction. That will be
one of the things that the CSB will be looking for in their investigation.
Preventive
Maintenance Program
Even if you have done your job well in selecting your
materials of construction, you still have to have a preventive maintenance (PM)
program in place for any storage tank system. You have to have a routine set of
inspections done to make sure that the tank and all of its attached piping are
working the way they were designed.
One critical part of that PM program is the visual
inspection of the interior walls of the tank for signs of corrosion or
weakening. This means that the tank gets cleaned on a regular schedule (every 3
to 5 years, depending on what you are storing) and a trained inspector goes
into the tank with a big flashlight and looks for signs of damage to the metal
and the welds or other joints. Any signs of metal fatigue or corrosion call for
a serious re-examination of the use of that tank for the storage of that
chemical. Serious or significant signs of corrosion could cause the tank to be
taken out of chemical service until it is repaired or replaced.
Another part of the PM program is less rigorous but just as
important. Every time that employees work around a storage tank they should be
trained to look at it and report anything out of the ordinary. In every leaking
tank that I have ever observed, the leak always started out small. If a tank
has to leak, you want to catch the leak before there is a puddle of the
chemical on the ground; every pound on the ground is a pound that you can’t
sell to your customers.
I have no idea when the last time that the Crude MCHM tank
was tested. You can bet that the CSB will ask and ask for documentation. From
the news reports and the size of the Crude MCHM spill I would be very surprised
if anyone was reporting small leaks at Freedom Industries. The CSB inspectors
doing their initial walk around of the site will certainly have been looking
for signs of leaks on other tanks at the facility.
Containment
Maintenance
As I have mentioned on a number of occasions any time you
have an above ground tank farm, you have to have some way to keep potential
spills from those tanks confined. Typically this means that an impermeable wall
of some sort is constructed around the tank farm. The construction of this
containment is not as simple as just putting up a brick or concrete wall. Where
the walls come together with the floor of the tank farm (which should be an
impermeable barrier in its own right to keep nasty stuff out of the ground
water) provisions have to be made to seal the joint so that nothing leaks out.
Materials of construction are not nearly so important in a
containment wall. You don’t expect the material to be left in contact with the
wall for any long period of time. All spills should be promptly cleaned up so
there shouldn’t be long enough contact with the wall/floor to cause a breach.
Preventive maintenance checks of containment dikes and walls
are usually pretty simple and do not require extensive training. Most tank
farms are open to the weather and fill up with water every time that it rains.
The water should remain in the containment area until specific action is taken
to remove it. If the maintenance folks are not complaining about having to
drain the containment area after a heavy rain, you have a leaky containment
area. The leaks are easy to find; just look for the small river running away
from the wall. Even after the rain you’ll be able to find the dried creek bed.
Spill Control
Most spills should never make it to the containment wall
much less into the nearby river. Again the vast majority of spills start out
small. Facilities are required to have a spill control plan in place to prevent
those small spills from becoming a big deal. Once the source of the spill and
the hazards associated with it are identified employees should begin
controlling the spill with a variety of tools and devices. The idea is to keep
the spill confined to the smallest area possible so that cleanup is easier.
The other thing that is done quickly is to take steps to
stop the flow of the material out of the storage tank. Again there are a
variety of tools available to do this including patches and plugs that can even
deal with relatively sizeable holes in the walls of tanks. I have personally
seen a six inch hole in a tank plugged well before 5,000 gallons of product
leaked from the tank.
The news reports that I have seen seem to indicate that
there were no significant spill control efforts taken inside or outside of the
containment wall until after the West Virginia Department of Environmental
Protection (WVDEP) inspectors had actually gotten on site. At that point a
Crude MCHM slick could already be seen on the Elk River.
Spill Detection
There are lots of ways to detect spills. For really
dangerous toxic chemicals there are gas detectors that can detect the airborne
component of the spill down to the parts per billion detection limit. For
flammable chemicals there are detectors that can determine when there is a
concentration of the chemical in the air that could be expected to explosively
ignite. All of these detection schemes are expensive and only justifiable if
there is some special risk for relatively small leaks.
Again, the most common way that leaks are detected in tank
farms is individual employees seeing the evidence of the leak in the normal
course of their duties. In this case, however, it seems that the odor of the
product allowed WVDEP inspectors to find the leak based upon public odor
complaints. It would seem unreasonable to assume that the folks that worked at
the facility were not able to determine that there was a leak based upon the
odor in the plant area.
A possible reason that the odor did not raise flags at the
facility a week ago yesterday may have been that they had been living with the
odor of a leak for some time. The human nervous system does a real good job of
ignoring odors after a certain amount of time being exposed to the odor. This
will be another item that the CSB will address in their investigation.
Next Installment
In the next installment in this series I will look at the
communications issues associated with this spill and look at how they would
have gone in a perfect world.
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