Courtesy of Tom Garrett.
Here are his comments regarding his photos:
"At about 12:35 p.m. on Tuesday, August 6, 1974, a tremendous explosion
ripped through Appleyard in South Wenatchee, followed by a huge ball of
fire and a large mushroom cloud. The blast left a crater in the middle
of the rail yard 80 feet long, 60 feet wide, and 35 feet deep, and all
but leveled an area a half-mile-wide. I happened by a couple weeks later
with an Instamatic camera."
Many more explosion photos can be seen here by using the Wenatchee label of this website.