Thousands of motorists were trapped in a massive morning rush hour traffic jam on July 23, 2007 after a tank truck carrying 40 tonnes of hot tar (asphalt cement) rolled over in the westbound transfer lanes of Highway 401 in Toronto. As a result, the entire load of tar escaped from the heavily damaged tanker. The hot heavy tar spread across six lanes of the highway and entered several storm sewer catch basins in the transfer and collector lanes. The hot tar quickly traveled through the storm sewer system under the highway and then entered a nearby 72 inch main storm sewer pipe, traveled through it, and migrated into the surface waters of Black Creek.

  

 

 
 

Initial emergency response operations on the highway included spreading sand on the spilled tar and recovering the contaminated materials with front-end loaders. High-pressure hot water tank trucks broke up the tar in the highway catch basins and vacuum trucks sucked up the heavy tar. A series of containment booms were also deployed in Black Creek and underflow dams were constructed at the main storm sewer outfall to minimize the downstream environmental impacts.

The damage to the asphalt on the highway was so severe that all six lanes of the highway had to be repaved.

  
 

After completing the initial tar recovery operations on the highway and stabilizing the tar at the outfall, an assessment of the site conditions confirmed most of the 40 tonnes of tar that escaped from the overturned tank truck had migrated into the storm sewer system between Keele Street and Highway 400. The tar had also severely impacted the 72 inch main storm sewer pipe north of the highway. The storm sewer system also contained laterals (measuring 8 to 14 inches in diameter) directly under the highway. The laterals that were visible were also impacted with tar.

 
 

 

This particular section of the highway had previously been identified by the Ontario Provincial Police as being a hot spot for traffic accidents. The potential was high for further collision-related spills to enter the storm sewer system the clean-up operation. In addition to developing a site-

  

specific confined space entry and rescue training program, further safety precautions were implemented to protect the emergency response team members

 

 
 

The recovery operations along highway catch basins included the use of 10,000 PSI water jet cutters and a Supervac(c) recovery unit. In the deeper catch basins (where the tar was up to 28 inches thick), hot water was injected into the bottom to reduce the viscosity of the cold tar. This combination of equipment and recovery techniques worked very well.

High pressure water jet flushing of the residual tar on the catch basin walls worked well; however, the potential to damage the concrete walls led to discontinuation of this approach. Field tests using ice blasting (ice pellets pumped with compressed air at supersonic speeds) were very successful and didn't damage the concrete. The successful application of this relatively new technology for cleaning up oil spills will likely be copied in other cleanups, especially for spills in environmentally sensitivity areas where chemical degradation is undesirable.

  

Due to the limited access to the tar inside the laterals under the highway, a number of flushing/recovery techniques were implemented. Hot water flushing (with a high pressure "reverse pipeline" flushing nozzle) was used to move the tar inside the laterals into the upstream and downstream catch basins. This use of this unique recovery technique worked well and will continue until the tar in the small diameter laterals is removed (to the extent practicable). In order not to damage the aging storm sewer infrastructure or undermine the highway (as a result of high pressure flushing), any remaining tar deposits in the laterals could be stabilized or encapsulated to prevent the release of residual deposits into the main storm sewer pipe.
 

 

Dec Doran (above center photo) is Oil Spill and Firefighting Coordinator for Oil Spill Control Services in Richmond Hill, Ontario, Canada. Dec and his team were retained by the trucking company that owned the tank truck that was involved in the tar spill. Contact Dec at oilspill@sympatico.ca

 

 

NOTE; Extreme caution has to be instilled into the HAZ-MAT truckers as well as any surrounding vehicles. The pressures and responsibilities laid upon their shoulders is tremendous. It is not only the mechanical/physical damage to the vehicles and personnel involved, but to the precious environment as well, where recovery can not always be guaranteed.

 

 

RETURN TO HAZ-MAT MENU