Just before dawn in the east-central Wisconsin farming community of Weyauwega, the early-morning quiet of March 4, 1996, was interrupted by the sounds of crashing metal and burning propane. Thirty-seven tank cars of a Wisconsin Central Railroad train had derailed near an industrial area at the north...
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Another problem was obtaining the necessary number of telephones to complete the calls to deal with the incident. The local telephone company brought in 40 lines by noon on the first day of the incident.
The"emergency" response phase of the incident only lasted until approximately 10:45 A.M. on the day of the derailment. Evacuation of the city had been completed by this time, along with the relocation of response personnel to a position past the command post, which was now 11/4 miles from the derailment scene. At this point, the focus turned to stabilization, clean-up and restoration of the incident scene, which took the next 17 days to accomplish.
Hazmat Teams Called In
The first hazmat team arrived on the scene within one hour after the derailment occurred. The railroad, which had conducted exercises on this type of incident using the incident command system, brought in hazardous materials clean-up experts from contract companies, along with an operations supervisor to coordinate railroad activities with the incident commander. Hazmat teams also responded from Appleton, Oshkosh and Stevens Point and Brown and Waupaca counties.
Because of the potential dangers of the burning propane and LPG tanks, the hazmat teams were assigned an advisory role until companies hired by the railroad arrived on the scene. These contract companies worked closely with the incident commander, the hazmat teams, the railroad and environmental agencies to determine the best course of action based on the condition and positions of the propane and LPG tank cars.
Temperatures during the incident ranged from daytime highs of 15 degrees to 40 degrees F to nighttime temperatures of -5 to 25 degrees F. As the incident progressed, the weather forecast was for warmer temperatures that would cause the pressure to increase inside the derailed tanks much like the increased pressure that occurred in Waverly that caused the BLEVE of one of the rail tank cars there.
The emergency response personnel assumed a role of support for the contractors during the process of stabilizing the burning and damaged tanks. Unmanned monitors were placed into service on the third day of the incident as the pressure fires subsided and about a half dozen propane and LPG tanks still had minor fires burning. Off loading of the tank cars was not undertaken because it was unknown what the extent of damage was to the cars.
After an evaluation of the derailment site, the decision was made to "hot tap" some of the propane and LPG cars to transfer the remaining fuel to a burn pit where it was allowed to burn off. The outer cars were tapped first and tapping moved inward until the last car was reached which could not be hot tapped due to its position.
Hot tapping has been used successfully for many years in the chemical and petroleum industry but has limited applications in tank car accidents. The process involves the welding or securing of a tapping to a vessel (such as a tank car) while it still contains gases or liquids. The tank is then drilled through a valve attached to the tapping fitting. A special drilling machine is used which threads the valve and reduces leakage. Once the drill bit penetrates the vessel wall, the drilling machine is removed from the valve. (Hot tapping should only be attempted by trained and experienced contract personnel. This is NOT an emergency response function.)
Because of the potential danger to personnel, tanks containing certain commodities should not be tapped. They include: acetylene, ethylene, ethylene oxide, halogens, elemental sulfur, hydrocarbons in stainless steel tanks, cryogenics, hydrogen, acids, oxygen, and tank cars operating at below atmospheric pressure. Once the tank is tapped, nitrogen is injected into the tank forcing the liquid through the tap valve to a flexible hose connected to a pump and then into a burn pit through a hard pipe, where the liquefied compressed gas is then burned in a pool fire. The liquid is burned off until the tank is empty.