Underground Tank - Risk Mitigation

Underground tanks containing chemicals and other hazardous solutions can be a serious source of groundwater pollution. The following mitigation measures could be implemented as risk control steps with regard to these underground tanks to effectively reduce the risk of pollution.

The use of double wall tanks and the construction of tanks with spill containment systems is a primary consideration when designing and constructing underground tanks containing chemicals and other hazardous solutions.

This is a suitable risk reduction technique for the identified risk of pollution. In order for a risk reduction programme to be effectively implemented the implementation of engineering risk control measures plays an important and significant role. Where double wall tanks can be utilised this will reduce the possibility of an undetected leak. As soon as liquid are detected in the space between the tank wall and the outer wall immediate action can be instituted to repair the leak before the chemical in the tank can contaminate groundwater. The spill containment system of double wall tanks is normally controlled with the installation of detection alarms and emergency pumping systems in this outer space around the tank.

Another risk reduction technique is to designs of tanks and piping in such a manner that they can be a visually inspected on a regular basis.

In order to ensure that leaks and potential leaks and cracks in tanks and pipes are detected when it is still possible to prevent major spills the tanks and pipes are normally designed that it can be a visually inspected on a regular basis. These inspections will include the inspection of the critical points by a competent person who will record the findings of the inspection in an appropriate record system. Tanks which cannot be visually inspected regularly would require the construction of a leak proof secondary containment and alarm system that is capable of containing the spill and activating the alarm rapidly when a leak occurs in order to prevent the chemical to contaminate the ground water.

In some cases the introduction of a ground water monitoring program for all underground storage tanks are used to reduce the risk of contamination. In order to ensure that even small leaks are detected in time a comprehensive ground water monitoring program should be instituted for all underground storage tanks if this option is considered. These programs should be so designed as to ensure that the ground water is monitored for the appropriate substances that may appear in the ground water as a result of leaks. Substances to be monitored for would include dissolved and un-dissolved liquids and solids that are stored in the underground tanks or may be chemically forms as a result of the products stored. The monitoring should be done at predetermined points around the underground tanks at least taking into consideration the variability of the water table as well as the soil type and structure.

The use of corrosive protection materials in the construction of underground tanks and pipes is another risk reduction methodology that is used form time to time. Where this control technique is utilized it is important to make use of chemical specific protection materials in the construction of underground tanks and pipes in all areas where the chemical to be stored will come into contact with the tank or pipes. In addition to the application of protection materials for the chemical being controlled additional protection should be applied to surfaces that could be exposed to soil and sunlight in an attempt to slow down oxidation of the construction material. Should corrosion be discovered, despite the application of corrosive protection materials, it should be repaired immediately by an appropriately qualified person. Care should be taken to then conduct a complete inspection of the tanks in an attempt to discover hidden corrosion in time.

A detailed tank management plan which addresses training of emergency personnel in inspection procedures in not a risk control technique that is used during design and construction but does for an integral part of the risk management plan.

It would be a good practice to develop a detailed tank management plan that includes material inspection plans as well as other tank management practices. The training of emergency personnel in inspection procedures is not necessarily risk mitigation but is an absolute necessity for the management of the tank farm. It is the role of the operational personnel to conduct critical point inspections on the tank and piping installation. The emergency response team will have the role of emergency clean up and response after a spill gets out of hand and should primarily be trained for this function. The conducting of post spill clean up is a highly specialised job and any person involved in that should be specifically trained in the use of the specialised personal protective equipment as well as the specific hazards associated with the particular chemical involved in the spill.

© 2009 Carl Marx