Not about Agent Orange, but for awhile I worked at an environmental engineering firm.
We had a project to clean and mitigate solvents that came from jet engine testing, near Rancho Cordova, near Sacramento.
Apparently at another airfield, in El Toro CA the USMC flew jets. The planes were washed down using solvents, which leached through the soil, into the ground water aquifer.
I watching the cleanup of an old petroleum-geneeral industrial waste site. Most of my town is built upon old oil fields. I havee seen building sites dug down 15-20 ft. to replace soil.