An old adage, often encountered by students of ecology, states that “everything is connected to everything else,” the key word being “everything.” What is true in the realm of ecology also applies to religion, politics, hazardous materials, and of course, to our world of emergency response. The transportation of petroleum offers an excellent example.
In the earliest days of the “Age of Petroleum,” crude oil and refined products were transported in barrels or drums carried as general freight on railcars. All that was required to handle these shipments was a ramp down which to roll the containers and, perhaps, a two-wheeled hand truck to move them about the receiving facility; a strong back attached to the handles was also an asset. The amount of product was relatively small and any spill could be contained with a scoop and a supply of some absorbent material such as straw, wood ash or sawdust.
Fires, when they did occur, usually devolved into conventional structure conflagrations by the time the local fire department responded, and these could usually be handled by the conventional fire suppression techniques in use at the time.
As the demand for petroleum products grew, the drums were supplanted by tanks permanently affixed to railroad flat cars, hence the first “tank cars.” These tanks were far too large and too heavy to be moved by hand truck and muscle power. Since, as a practical matter, they could not be moved from the track site, how to unload/load these containers and subsequently transport their lading around the facility for use or delivery to customers assumed paramount importance. The answer to the problem was, of course, the advent and deployment of pump systems connected by an array of rigid pipes and flexible hoses controlled by valves.
Because manufacturers and distributors had to purchase petroleum related commodities, i.e. hazardous materials, in tank-sized lots, on-site storage tanks with their larger product inventory became part of the industrial/commercial landscape. The first petroleum product to see wide spread consumer use was kerosene which was used to light the lamps that illuminated life in 19th century America.
This changed around the turn of the 20th century when the automobile came chugging down the lane of history. This innovative contrivance, with its voracious appetite for gasoline, greatly increased the number and size of on-site storage tanks within local communities. In the 1930’s, in response to the introduction of Walter P. Chrysler’s high compression engine “hi test” or “Ethyl” (from the tetraethyl lead used as an “anti knock” agent) gasoline added another set of tanks to those present in the local environment. Tanks for diesel fuel, intermediate grades of gasoline and “E85 (85 percent ethanol) followed.
The risks inherent in the use and storage of these fuels are not confined to the industrial plant site. The wide spread utilization of tools and maintenance equipment powered by small internal combustion engines has transformed virtually every garage and workshop or storage shed into a potential hazmat incident.
The expanding demand for gasoline and its use within the domestic environment engenders the development of new transportation methodology along two lines. First, tanks used for the rail transportation of hazardous materials are re-designed. The tank, which had previously been carried on a flatcar was itself equipped with trucks (wheels) to become the body of a dedicated, purpose-built vehicle, i.e. the “tank car.” The weight saved by eliminating the flat-car appurtenances allowed more lading to be carried with the same GVW (Gross Vehicle Weight) than the previously utilized tank on flat car configuration.
The “purpose built” tank car not only circumvents the weight limitations inherent in the use of conventional flatcars, but the size of the tank also undergoes a prodigious growth spurt, culminating in the gargantuan “super tankers” which presently traverse the nation’s railways on a daily basis to satisfy the demands of American commerce.
The advent of the automobile (and to a lesser extent the chainsaw and the lawnmower) with its appetite for fuel introduced hazardous materials into the neighborhoods of suburbia. The need to deliver materials to and pick up product from these locations, far removed from rail spurs or sidings, engenders the advent of the motor truck; itself an adaptation of the automobile.
The motor truck, with its flexible scheduling and utilization of the public roadway system, unleashes industry from the need to locate near rail lines. Instead of confinement to a congested industrial zone, a facility can be sited almost anywhere. While this may have a somewhat beneficial effect on traffic flows and allowed development of more remote areas it also brings about conditions not entirely beneficial to the immediate neighborhood.
As industry migrated away from the rail lines the risks inherent in industrial operations spread with it and as we have seen all too recently these are not always insignificant.
The way that the motor truck carries liquid commodities underwent an evolution similar to that of the railroads. First came barrels carried in box trailers as general freight, followed by tanks mounted on flatbed trailers, followed by purpose-built tank trailers. In an effort to maximize the amount of lading carried within the weight limits imposed on motor trucks, tank manufacturers switch to aluminum and adopt the “stub sill” design. These trailers, while highly efficient in terms of the amount of lading they can move as compared to the GVW allowed, do have a great disadvantage; the tank itself is the supporting structure of the trailer. The principle involved is the same as that found in the case of a beverage can, so long as it is upright and full, it supports the load, but if it is distorted and/or punctured its structural integrity is likely compromised. As a result, a loaded trailer involved in a rollover cannot be safely up-righted without first being emptied of the lading. This is sometimes easier said than done if the valve gear and/or loading hatches are on the underside of the overturned tank or otherwise inaccessible. This being the case and necessity being the mother of invention, Shell in cooperation with the Texas Engineering Extension Service developed a methodology and protocol for safely voiding an overturned tank trailer.
Shell’s method involves cutting a small (three to three and a half inches in diameter) access port in the upper side of the tank; which has, of course, been grounded (as have all tools and equipment in contact with it) by means of a hole saw. This port allows the insertion of a pipe or “stinger” attached to an air operated pump to facilitate the removal of the lading to a second tank for recovery. The process is repeated for each compartment in the overturned trailer.
Once a compartment has been voided it may be filled with flammable vapors. The possibility of fire and/or explosion cannot be ignored; again, necessity is the mother of invention.
The only practical way of rendering an emptied tank or tank compartment vapor-free is to fill the vacant space with an inert substance. Such as nitrogen (N2 ) or carbon dioxide (CO2 ). Of the two, the easiest to use is CO2 , which can be obtained as “dry ice” from any of the larger retail stores. All that is necessary is to toss several pieces of this material into the empty space where it sublimes into gaseous carbon dioxide. The cold, heavy gas will then rise to fill the void space and displace the oxygen containing atmosphere.
The same idea is employed in the use of nitrogen (either liquid or gaseous). The gas is introduced through a hose and allowed to flow until the atmosphere is displaced.
Both of these gasses have drawbacks in regards their use in the field as inerting agents. In the first place they are odorless and colorless and therefore invisible. This makes it impossible to determine visually whether or not a given space is totally inert. Repeated monitoring is necessary to assure that the space remains inert. Secondly, since they are gasses, N2 or CO2 can escape through cracks or damaged areas of the tank wall thus necessitating repeated replacement to maintain an inert condition in the confined space.
The use of compressed air foam (CAF) helps to overcome these shortcomings. If the controls of the machine are adjusted to produce a light dry foam, this material will bridge over a crack or other small opening in the tank wall. The foam provides a means of visually verifying that the evacuated space is filled with the inerting agent and reduces the need for repeated sampling with test instruments. In the event that the lading of the overturned vehicle is pyrophoric or hypergolic and therefore oxygen reactive (as in the case of ethylene oxide) some CAF units can be adapted to generate foam with an inert gas instead of air.
Once an overturned tank has been voided and secured it still needs to be uprighted. This is not as easy as it would seem at first glance. Most highway tank trailers, especially those employed for the transportation of gasoline and diesel fuel, are constructed of aluminum and, due to the stub sill design usually have no separate frame. The tank itself serves as the body of the vehicle. These tanks operate on the same principle that works for a beverage can. When the tank (or the can) is full of liquid it is rigid and structurally strong. In some instances, the can is strong enough to support the load imposed by the weight of a human body. However, if the vessel is empty or deformed as the result of an accident, it looses its structural integrity and the can may be crushed or deformed by hand or a relatively small force.
Because of the foregoing, the uprighting of an overturned tank vehicle is a task that must be undertaken only after extensive evaluation of the vehicle and consideration of the resources on site. One thing is certain: it cannot be accomplished by simply throwing a cable around the tank and engaging the biggest winch on the wrecker (the term “wrecker” is apropos). There is one case reported in which a wrecker operator attempting to upright an overturned tanker did exactly that. He is said to have thrown a cable around the tank and re-attached the hook to the line, forming a noose around the tank. When he activated the winch, the noose tightened around the tank and the wire cut it in two like a hot knife in warm butter; spilling the better part of ten thousand gallons of gasoline in the process. Hopefully he learned from the experience.
The best and safest method of uprighting a tank vehicle is by means of air bags. This innovative technology, developed by the Germans for the recovery of downed aircraft in World War II, allows for precise control of the load during the lifting operation while spreading the pressure of the applied force over a wide area instead of a narrow band as with using an unassisted cable. The tank should be stabilized during uprighting by at least one arresting cable to prevent momentum from carrying the tank beyond vertical “break point” resulting in a secondary rollover. If possible, a second cable, opposite the first, should be attached to help pull the tank upright when it gets near the “break point.”
Innovations in emergency transportation response techniques appropriate to rail transportation have also kept pace with developments in industry. The introduction of the shelf couplers and head shields during the 1980s drastically reduced the number of hazmat releases due to head punctures caused by the standard “E” coupler. This was particularly true in the case of the “Jumbo” tank cars with their greatly increased mass (weight) and lowered center of gravity, introduced during the post WWII era.
Head punctures result when the train comes to an abrupt halt during the course of the incident. When this happens, the momentum of the tank car causes it to rotate about its center of gravity, detaching the coupler and elevating it to the level of the head of the preceding car. All of the force generated by the momentum of the tank car and the following coupler is now concentrated in the coupling and puncture of the head or end wall of the leading car is all but assured.
The shelf coupler, which needs to be installed only on tank cars, serves to prevent the disengagement of the couplings and the resulting rotational elevation of the coupling to a position from which it can affect a head, or end-wall, puncture on the car ahead.
As freight trains became longer it became impossible for a brakeman in the caboose to monitor the entire consist which now may exceed 100 cars. The result was the supplanting of the caboose and its crew by the Flashing Rear End Device (known in polite society as “FRED.”) In addition, there is a rapid increase in the number and distribution of trackside monitors to alert the operating crew to such things as “hotboxes,” dragging equipment or leaking containers before they can cause an incident.
No system is perfect. In spite of the numerous innovations in operating methodology and equipment introduced over the past decades, hazmat incidents, both in rail and motor truck transportation, continue to happen. As the size and number of shipments increases, the magnitude of any untoward incident and the damage it engenders also increases. A fire involving a 55-gallon drum of gasoline is one thing, one impacting a ten thousand gallon trailer loaded with the same commodity is another. The same can be said regarding the “collateral” damage caused by an incident. A few pounds of a mixture of ammonium nitrate (NH4 NO3 ) and fuel oil, known as “ANFO,” makes short work of a stump in a field or a rock blocking the route of a freeway, but a storage facility or shipment containing the same material can, if detonated or involved in a fire, cause a disaster on the magnitude of Texas City or West, Texas. While “bigger” is very often “better,” it is also true that “bigger” is more dangerous.
To cope with the risks posed by the innovations in the transportation of hazardous materials in general and petroleum products in particular, those involved with emergency response have introduced a number of innovations to enable these incidents to be mitigated. Some of these are self-contained breathing apparatus (SCBA), compressed air foam systems (CAF), high expansion foam and foam specifically designed to work with 85 percent ethanol gasoline mixtures such as E85.
Within the last several decades, new products have entered the market place, such as lead free gasoline, “gasohol” and liquefied natural gas, to name a few. Each of these has changed haz mat response protocols and in some cases engendered the development of new hazards. Lead free gasoline is a case in point.
There are, presently, two practical processes for the manufacture of “lead free” gasoline: one requires the use of oleum or pyrosulfuric acid (H2 S2 O7 ) produced by dissolving sulfur trioxide (SO3 ) in sulfuric acid (H2 SO4). The second, and presently the most common, requires hydrofluoric acid, an aqueous solution of hydrogen fluoride (HF). Until the advent of lead free gasoline, this toxic and highly corrosive material was little more than a laboratory curiosity stored in wax lined bottles (since it can dissolve, or etch, glass) which were seldom, if ever, opened.
Now, hydrofluoric acid is a fairly common article of commerce being shipped in tank cars over the rail system. The introduction of hydrofluoric acid into the market place brings a whole new regimen of hazards and these required numerous innovative protocols and equipment to remediate them. One of the most noticeable is the brown paint that is used on the “spill zone” under and around the dome on HF tank cars and on pipe joints and fittings associated with the material. This paint changes color from dark brown to a brilliant orange when in contact with HF from a leak or spill. Other innovations include new materials for the fabrication of tanks, pipes and plant equipment, and protective clothing and breathing apparatus to withstand exposure to HF. Instrumentation to detect leaks and releases have been developed as well as protocols for medical treatment of individuals exposed to HF. Emergency response protocols had to be developed and personnel trained in its implementation.