Hazardous Materials Accident Report

Adopted: September 4, 1991
FEBRUARY 13, 1991

NTSB Number: HZM-91/01
NTIS Number: PB91-917004
PDF Document (4.57 MB)


About 3 a.m. Pacific standard time on February 13, 1991, a tractor-semitrailer (cargo tank) overturned as the vehicle was traveling on a main urban roadway in Carmichael, California. The tractor and semitrailer were owned and operated by Calzona Tankways, Inc., of Phoenix, Arizona. At the time of the accident, the truck was being used for the intrastate delivery of gasoline to service stations; the cargo tank contained about 8,800 gallons of automotive gasoline.

The driver lost control of the vehicle in a curve. The vehicle overturned onto its side and struck the embankment of the drainage ditch located in a dirt field beside the road. The cargo tank bounced and came to rest in the dirt field and adjacent to the drainage ditch. The rear end of the cargo tank landed on an unoccupied car parked in the field.

Gasoline from the cargo tank spilled into the drainage ditch, which extended under the roadway and behind private residences nearby. About 15 minutes after the overturn, the gasoline ignited behind a residence. The fire flashed back and engulfed the overturned cargo tank, and the car under the cargo tank. A second unoccupied car parked near the overturned tank truck also caught fire. Gasoline runoff in the drainage ditch entered the underground drainage system and was also ignited.

In addition to the total loss of the tank truck, its cargo, and the two parked cars, four homes and their contents were destroyed or heavily damaged by fire, and the residents from a 2-mile-square area were evacuated. Total property damage and cleanup costs were estimated at nearly $1 million. There were three minor injuries.

The National Transportation Safety Board determines that the probable cause of the accident was the inattention of the driver, for undetermined reasons, which resulted in his operation of the tank truck at excessive speeds leading to its overturn. Contributing to the severity of the accident was the failure of one of the liquid-level sensors mounted on the manhole cover for the forward compartment of the cargo tank to remain secured.

The following safety issues are discussed in this report:

  1. The lack of U.S. Department of Transportation performance standards for components mounted on manhole covers on motor vehicle tanks transporting bulk hazardous liquids;
  2. The adequacy of California standards for highway bulk liquid cargo tanks;
  3. The effectiveness of the carrier’s evaluation of the drier training and performance; and
  4. The lack of requirements for postaccident toxicological testing of drivers involved in the intrastate transportation of hazardous materials.

Safety recommendations concerning these issues were made to the Research and Special Programs Administration (RSPA), the Federal Highway Administration, and the National Highway Traffic Safety Administration of the U.S. Department of Transportation; to the State of California; to the other States and U.S. Territories; and to the motor vehicle carrier.