Environmentalists joined labor unions and Washington state officials in celebrating their victory this weekend after thwarting plans to unload and temporarily store 110 tons of toxic waste in Seattle. A ship carrying PCB-tainted waste from U.S. military bases in Japan arrived in the Port of Seattle last week, and the U.S. Defense Department attempted to have the waste unloaded in the city while it figured out what to do with it. Environmentalists threatened to sue if the waste was taken off the ship, and members of the local Longshoremen and Teamsters unions refused to take the cargo ashore. The ship left Seattle on Friday, headed for Vancouver, Canada, but Canadian officials have also refused to allow the waste to be unloaded. The Defense Department said a final destination for the contaminated cargo has not yet been found. It may be sent back to Japan.