The 1974 Wenatchee Appleyard Explosion: What Happened, and Why?

Tuesday, August 6th, 1974 was a warm, summer day. The Wenatchee morning DJs on that day read:  “Lots of sunshine - clear skies with a HIGH in the low 90s.”

The old Farmers Almanac says the high that day at Pangborn Memorial Airport reached 91. Wenatchee, thankfully, didn't have any low-lying clouds on that day. (We'll explain later why that matters.)

The Noon hour on that Tuesday was routine. Many people in the Wenatchee Valley were on their lunch hour.

Then at 12:35 pm - a Burlington Northern Railway tank car exploded.

Eyewitnesses say the ensuing shockwave created a mushroom cloud. Debris of metal shot out in all directions from the Wenatchee Appleyard. Some of the shrapnel made the jump over the Columbia River - into East Wenatchee.

Its contents?

'10,000 gallons of PR-M (monomethylamine nitrate), the company’s designation for a sensitizing agent used to make Tovex, a new type of explosive gel used by the mining industry.' - Historylink.org

And where was it? The Wenatchee Appleyard - located just underneath the Vue-Dale Drive-in and Mission View Elementary (called South Wenatchee School until its name change in 1970.)

Thankful school wasn’t in session - but the powerful explosion took the lives of two Burlington Northern employees.

Six others went to the hospital and 60 others reported various kinds of injuries from the force and debris of the explosion. Reports of shattered glass in shops, storefronts, and homes were reported as far away as 3 ½ miles away. 

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Bret Marshall, a lifelong East Wenatchee resident, still remembers the historic blast. He was a 7-year-old boy - at home enjoying the remainder of his summer break. The Marshalls lived on Aurora Avenue and 17th Street, not far from the Wenatchee Golf & Country Club.

Connor: Did you hear the blast?

Bret Marshall: “Oh Yeah. I was in the house. The explosion cracked one of our windows. Wow. I remember it. That was something.”

C: Was your mom home with you and your siblings?

BM: “No, she was at work. She was a surgical nurse, working at either Deaconess Hospital (on Okanogan Avenue in Wenatchee) or Rosewood Hospital (Central Washington Hospital.)”

Whichever location Bret’s mom worked at that day, her shift was about to pick up.

It was fortunate for the Wenatchee Valley that the Appleyard explosion happened on a clear day. Had it been overcast - the shockwave would have caused even more severe damage.

NOTE: The popular TV show Mythbusters had to postpone an experiment of blowing up a cement truck because of low cloud cover on one of their planned filming days. Cloud cover reflects the compression wave and causes even more damage to the surrounding area. 

1,700 insurance repair claims were made in the following weeks.

What Caused the Explosion 

In September of 1974, the NTSB (National Transportation and Safety Board) conducted hearings at the Thunderbird Hotel on North Wenatchee Avenue.

Railway employees testified that the tank car (demolished by the blast) was standing idle on a sidetrack. Nothing abnormal took place before the event. 

‘The report concluded that the board of inquiry was unable to determine the probable cause of the disaster and assigned no liability.  The board issued five recommendations, however, urging the Department of Transportation to tighten shipping regulations for hazardous chemicals.  The disaster left investigators and experts alike completely baffled and at a loss about preventing similar incidents.’ -Historylink.org

INFO SOURCES: Historylink.org, Bret Marshall (East Wenatchee resident), Wenatchee School District, Old Farmer's Almanac