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Accident Report Detail

Denver and Rio Grande Western Railroad Company Train Yard Accident Involving Punctured Tank Car, Nitric Acid and Vapor Cloud

Executive Summary

About 4:00 a.m. mountain standard time on April 3, 1983, a Denver and Rio Grande Western Railroad Company (D&RGW) switch crew was switching 17 cars in the D&RGW's North Yard at Denver, Colorado, when a coupler broke on the 4th car, leading to an undetected separation of 150 feet between the 3rd and 4th cars. The engineer, responding to a hand lamp signal from the foreman, accelerated the locomotive, with a caboose, an empty freight car, and a loaded tank car coupled ahead. The loaded tank car impacted a fourth car at a speed of about 10-12 mph. Upon impact, the end sill of the fourth car (empty boxcar) rode over the coupler of the (loaded tank car) and punctured the tank head. Nitric acid spilled from the car and formed a vapor cloud which dispersed over the area. As a result, 9,000 persons were evacuated from the area; 34 were injured. Damage to railroad property was estimated to be about $341,000.

Probable Cause

The National Transportation Safety Board determines that the probable cause of the accident was the complete failure of a coupler of a box car leading to an undetected separation of cars being switched and the puncturing of a tank car by the end sill of the box car when the coupled cars overtook those which had separated. Contributing to the accident was the lack of a federal regulatory inspection or an industry practice for a periodic inspection to detect defects in hidden car components. Contributing to the severity of the accident was the nature of the released product, insufficient guidelines and absence of preplanning which led to the evacuation of about 9,000 residents and injury to 34 persons.

Accident Location: Denver , CO    
Accident Date: 4/3/1983
Accident ID: DCA83AR004

Date Adopted: 5/14/1985
NTSB Number: RAR-85-10
NTIS Number: PB85-916310

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