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Use a cleaning method such as "butter Worthing" with hot water, pump out the liquids and then ventilate as above. Inert the Tank Carbon dioxide from dry ice will be used to inert the atmosphere in the tank to below the oxygen concentration necessary for combustion. Note that flammable vapors will still be present; and once the tank is cut or opened, the inert gas can be lost. The atmosphere must be diluted to less than 8 percent 02 by volume to be completely safe for normal petroleum products. 02/LEL meter must be used to monitor the 02 concentration. Measurements must be made continuously. The quantity of inert gas that must be used depends on how the gas is presented to the tank. In practice, about 6 to 8 and perhaps as many as 10 tank volumes must be administered. Approximately 30 pounds of dry ice per 100 cubic feet (30lbs per 1,000 gallons) of tank volume is required to reduce the oxygen to 8 percent. There are several precautions that must be observed when using dry ice. The material is extremely cold (-109.3 ❑F). Also, the CO2 produced will be absorbed into any water present, thus effectively increasing the oxygen concentration. Foam the Tank If the product cannot be completely removed, a method, which has been proven successful, is to "foam" the surface of the remaining liquid with fire fighting or vapor suppression foam. This foam blend should be 3 or 4 inches thick and will have the effect of suppressing vaporization of the volatile material. The foam must be applied through a tank opening and thus the tank must be opened. After laying the foam blanket, the tank may have to be ventilated so that the flammable vapor concentration is reduced to less than 10 percent of the LEL on the combustible gas indicator. In extreme cases, high expansion foam can be used to completely fill the tank. Obviously, no ventilation will be necessary in this case. The general rule of thumb for cutting tanks with a cutting torch is that cutting slag should never be allowed to fall into free product. Naturally when cutting tanks by any method, appropriate fire protection should be available. Physical Hazards: Heat exhaustion is a possibility due to the climate, high temperature is a possibility inside the tanks therefore United will set up rotating teams to ensure that employees maintain cool and rotate personnel as necessary. Heat Stress: Due to the California climate, heat stress could be some concern. Drinking water will be available in the Support Zone. Decontaminate garments prior to consuming water. Heat stress can result when protective clothing decreases natural body ventilation. If temperatures on-site exceed 75°F while protective coveralls are being worn, then heat stress monitoring should be employed. Monitoring would include watching the workers for visible signs of heat stress.