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Friday
May272011

TFE-9

Run-off and Drainage Challenges

     While the firefighters and Hazardous Materials Technicians are handling the tank fire, it may be up to the FLBSS {Flammable Liquid Bulk Storage Specialist} to keep them advancing forward towards a positive conclusion. He does this by concerning himself with all run-offs from the firefight. All discharged water, product mix, Foam, and any other contaminate or liquid resource involved in your incident has to flow somewhere. Run-off challenges at a bulk storage tank fire are major in size, constantly increasing and frequently overwhelming. This generally occurs because the idea of overflowing these huge confinement ditches is hard to imagine. Per the API {American Petroleum Institute} standard 650, we know that these areas “shall be able to hold 100% of the volume of all tanks inside their dike area”. Run-off water and Foam is not calculated into this volume. During a major event, dikes become the “back-up” failsafe to prevent “product” release into the surrounding neighborhood, Increasing Foam and water levels often go unnoticed far too late in the incident. If this level of fuel, water, and Foam is evaluated too late, a major tank failure will easily overflow the dike and become an uncontrolled release. Think of diking maintenance first, the dike volume exists for “flammable hazard” confinement, not necessarily including the run-off added to this volume. This is not intentional, merely regulatory due to the complexities of such a large volume calculation. Since major failures rarely happen on tank farms, diking berms become useful for all types of needs. The storage and closeness of its boundaries are relatively secure for equipment, vehicle, and tool storage.

     Whether the dikes are poly-lined or not, they should always be kept free of normal rain run-off. If allowed to accumulate, these waters will reduce the carrying capacity should a bulk storage tank fail. Since they are isolated, this requires constant monitoring by tank farm personnel. If rainfall accumulates they should be immediately drained to the nearest storm sewer or alternate confinement area. In winter areas, snow must be plowed from inside the dikes, as this will reduce volume and contribute to an uncontrollable overflow during a tank farm fire. Any equipment should be removed from the dike confines. Do not allow employees to become used to storing equipment or tools inside diking areas. In some areas winter tank fires have used snow-blowing as a technique to cool production piping when multiple tanks have failed. If this is a tank farm strategy in your area, is all snow-blowing equipment maintained and ready to deploy?

     Since most flammables float on water, this may work to your advantage. Drainage could be taken from the base of the run-off pool, while fuel recovery efforts should concentrate from the surface of the pool. Foam operations “1/4 drain time” into solution may simplify your efforts, “IF” you can afford the space and time for this action to occur. In most cases this “time” option is unavailable due to the large volume of Foam and fuel being collected from the leak, spill, or overflow from the storage tank. In this case, the Foam/solution/fuel mixture can be “Vactored” or pumped from the dike area and separated later.

     Because of the close proximity between firefighters and large volumes of “free” liquid, safety gear is essential. Many constituents of modern fuels have asphyxiate, carcinogenic, and hallucinogenic properties when exposure is concentrated. Given the respiratory problems with fuel vapor in high volume, and the potential flammability, firefighting operations in drainage and diking fields should consist of turn-out gear with SCBA {Self Contained Breathing Apparatus} at a minimal. Many plant employees are skilled in the use of APR’s {Air Purifying Respirators} but at a major spill, these filters may become overwhelmed by increased levels of vapors rendering them ineffective.

     Tactical operations for the control of diking run-off water should consist of; 1] Early data collection of current levels, 2] on-line pumping capabilities, 3] available empty storage tanks, or burn pits, 4] Common connections needed for Fire Department Engines if supplemental pumping is needed. By following these procedures, even if a storage tank “lets go” your dike maintenance is more likely to confine the release, preventing it from overflowing and migrating off-site. In the event of a major tank failure, these efforts save lives, property, and infrastructure from destruction.

 

                                          Haz Mat Mike

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