Methylene Chloride Leak: Stoughton, WI

Major emergencies require response agencies work together. Hazardous material incidents are no different. This was evident in Stoughton, WI, on Dec. 2, 1993. While this incident was not major and no injuries were reported, it shows how well an emergency can be mitigated when all response groups work effectively with each other.

Photo by David F. Peterson
Entry team 2 (the author and Chuck Schwierske) overpack the second drum in the back of the van trailer.

At about 4 P.M., the Stoughton Fire Department was called to a large truck stop at the intersection of Interstate 90 and Dane County Highway N for a reported chemical leak in a parked van trailer. The chemical involved in the leak was reported to be methylene chloride, a toxic, combustible liquid that is used as an industrial solvent. As a precaution, the Madison, WI, Fire Depart-ment's Hazardous Incident Team (HIT) was also notified of the incident for research capabilities but remained in quarters. The weather was cold and clear with a slight breeze blowing from the southwest. The temperature was dropping slowly from 32 degrees Fahrenheit.

Upon arrival, Stoughton firefighters learned from the truck's driver that two 55-gallon drums of methylene chloride had been damaged when pallets of heavy machined parts shifted and fell on them. Fortunately, the two drums were the last to be loaded in the rear of the 40 foot van trailer. The driver identified a leak in the area of the drums when he noticed a liquid leaking out of the back of the trailer but he did not open the doors. The trailer bore a new U.S. Department of Transportation (DOT) placard that was white with lettering that said, "Do Not Store Near Foodstuff." He immediately notified the truck stop management of the emergency. The Stoughton Fire Department effected immediate site control by moving the parked vehicles from around the van trailer. After the paved area was cleared, members stretched plastic hazard tape upwind and downwind of the trailer to secure the "hot zone," the area of possible danger or contamination.

The Stoughton incident commander (IC) requested the assistance of the Madison HIT and the Dane County Sheriff's Department. The Wisconsin State Patrol also assisted.

In Dane County, a fire department can request the Madison HIT unit for help in handling hazmat incidents through a pre-arranged contract. It operates similar to mutual aid agreements and is renewed annually. When summoned, the Madison HIT responds to the scene and manages all hot zone functions under the local IC's system. The HIT leader advises the IC of the HIT's needs and tactics. A Madison chief officer responds with the HIT to serve as a liaison between the team and the IC.

Specially Trained Team

The HIT is a specialized unit formed in 1987 in response to the hazardous material threat within the community. The team is made up of personnel trained to the technician level as specified by the Occupational Safety and Health Administration (OSHA) and the National Fire Protection Association (NFPA) regulations and standards. Many members have attained specialist ratings (OSHA) through additional training.

Photo by David F. Peterson
The Stoughton Fire Department light truck illuminates the scene for workers in the trailer.

Technicians are trained to safely enter contaminated or hot zones with monitoring instruments and perform control operations to handle product releases. Hazardous material operations are highly complex and inherently dangerous, so they require a system where work groups of two are monitored by back-up work groups, in case of an emergency, and a sector officer. On the Madison team, the sector officer is referred to as the HIT leader.

The HIT leader also appoints a safety officer to monitor site safety conditions, a research officer to conduct chemical research, and a decontamination officer to make sure the decontamination corridor is properly set up and ready before anyone enters the hot zone. Paramedics are also assigned to check the health status of emergency personnel before they enter a hot zone.

In this incident, the decision was made to send in entry personnel to size-up the spill. The product, methylene chloride, was positively identified from the DOT required shipping papers. The leaking container(s) would be identified, the leak(s) secured and the drum(s) would be placed in overpack containers. To further help control the scene, the IC also decided to temporarily shut down the truck stop.

The HIT leader briefed the team personnel on what needed to be accomplished and they moved vehicles appropriately. Entry personnel were checked by on-scene paramedics while support personnel prepared a dressing area. An area inside the truck stop store was offered by the manager for this purpose. The indoor dressing area proved useful because of the chilly weather. Support personnel helped both the entry team and backup team get dressed. Because additional personnel and supplies would be needed, the HIT leader called for a paramedic ambulance and a supply truck with an equipment trailer from Madison's Fire Station 5.

The research officer used the computer and its data bases on Squad 6 to conduct the research of the chemical and make recommendations as to response procedures and appropriate protective clothing. Through this research, it was determined that Level A fully encapsulating suits were needed.

The research officer further summarized methylene chloride this way:

Photo by David F. Peterson
Entry team 2 continue to overpack the leaking drums.

Name: Methylene chloride
Synonym: Dichloromethane
Formula: CH2CI2
UN Number: 1593
CAS Number: 75-09-2
Molecular Weight: 84.9
DOT Class: ORM-A
Ignition temperature: 1,033ยบ F
Flammable limits: 12% to 19%
Flash point: none given/combustible
Properties: Colorless liquid with sweet odor like chloroform. Toxic and harmful if inhaled or absorbed through skin. Carcinogenic. TLV-100 ppm.

Into The Hot Zone

With the entry personnel ready to go on air and zip up their vapor-tight suits, the HIT leader provided them with a briefing detailing tactics and strategies within the hot zone. He also informed them of where the decontamination corridor would be.

The members of entry team 1 entered the hot zone to secure the leak and overpack the damaged containers. They overpacked the leaking drum, then were forced to exit due to low air. After decontamination, they became the backup team while their original backup personnel entered the scene as entry team 2. The second entry team overpacked the other damaged drum as a precaution and started to clean the floor when low air also forced their exit.

This team had a difficult task with trying to overpack the damaged drum which did not have a leak. Being a fully filled drum and very heavy, this team could not safely overpack this drum until supplied with a long board to use for leverage. To also complicate matters, both entry teams worked in a limited space and near the edge of the trailer. Safety of the entry teams was a big consideration for the HIT leader while these activities took place. As the second team exited, members were also decontaminated and became the backup team as the first entry team re-entered for more control activities.

Entry team 1 secured a lid on one overpack and began cleanup activities. They again exited and became backup while entry team 2 did the final cleanup and secured the site until the environmental contractor could arrive. At the completion of the incident all entry personnel were again checked over by on-scene paramedics as a precaution.

Photo by David F. Peterson
Entry team 1 member Bill Olson takes a break after doffing his Level A suit.

Photo by David F. Peterson
Entry team 2 finishes up the work in the trailer.

At 8:30 P.M., the scene was declared secured and response personnel began to pick up equipment. A critique took place at Madison Fire Station 6. The information is offered here to assist other hazmat responders:

Actions Reinforced

  • Good incident command procedures were followed and increased the efficiency of the incident.
  • Good initial site control eliminated ignition sources and kept others out of the hot zone. Also, property was moved away to decrease exposures.
  • Good support of the HIT unit by the Stoughton Fire Depart-ment. Lighting was provided to aid in site safety and speed up operations in the back of the van trailer.
  • Hot zone needs were also met by the fire department.
  • Quick assistance by area law enforcement also added to effective sit control.
  • The HIT leader provided good briefings to entry personnel by covering all aspects of safety and answering questions. The HIT leader had good information from research officer to aid in tactical development.
  • The HIT leader offered time updates periodically to entry team while in the hot zone.
  • Resources were brought to the scene promptly and support personnel performed superbly.
  • Decontamination corridor was set up promptly, eliminating entry delay.
  • All personnel were checked by paramedics before and after entry for medical monitoring purposes.
  • The safety officer kept a time log and checked for proper dressing procedures and protective equipment. Also, the safety officer closely monitored site safety aspects and kept the HIT leader informed.

Photo by David F. Peterson
The decontamination corridor was promptly set-up to decontaminate entry team members systematically.

Actions To Improve Upon

  • Cold weather concerns were highlighted. Response personnel should dress in winter coveralls to provide more comfort when suits are doffed and avoid hypothermia. Cotton under-gloves may also be considered to provide warmth to hands.
  • Cold weather decontamination practices should be employed when temperatures are below freezing. Dry contamination should be an option. Also, be careful of wind currents entraining chemical odors, especially near buildings.
  • Do not let responders remain in decontamination area. While in the decontamination corridor all personnel should consciously remember not to cross-contaminate. That is keep dirty or contaminated hands on the outside of response suits.
  • Firefighter turnouts should not be worn by decontamination workers. Turnouts should only be used for creature comfort when working at hazardous material incidents. Because they are made with leather and Nomex/PBI, which absorbs chemicals, they should not be used, or at a minimum covered with disposable garments.
  • Need to find better disposable booties in terms of safe footing. The entry teams at this incident found the spilled liquid to be very slippery.
  • Need to assure proper fitting facepieces to avoid rapid air loss while in suit.
  • Consider providing back belts for entry personnel to prevent injury for heavy lifting operations. Provide comprehensive training on proper back belt use for all personnel.
  • Need to consider protecting monitoring instruments better at hazmat incidents. One instrument at this incident had its surface paint dissolved at its base when it was set in the liquid on the trailer floor.
  • Need more support people to assist with the many tasks at a hazmat incident. While support was excellent, these personnel were overworked.
  • Need to carry more equipment on response vehicles that may be needed at hazmat incidents. Some ideas are to carry a small supply of lumber, disposable tools, more overpacks and ladders.
  • Need to consider a device to help prevent response personnel from falling off the back of the trailer.
  • Need to secure all energy sources. In this incident the wheels of the trailer could have been chocked as a precaution.

The efficient operations were due in part to strong leadership, practice and teamwork. It is also important to realize that perfect responses never happen but they should always be strived for.

David F. Peterson is a career fire/medic with the city of Madison, WI, Fire Department. He also responds on the Hazardous Incident Team (HIT), a Level A regional team that serves 11 counties in Wisconsin. Peterson conducts hazmat training for his department as well as area industry. He is also the founder and president of the Wisconsin Association of Hazardous Materials Responders Inc.