Chula Vista has joined the city of San Diego and a number of other West Coast cities in an attempt to force chemical giant Monsanto to pay tens of millions to clean up waterways polluted with a class of cancer-linked chemicals, known as polychlorinated biphenyls, or PCBs. The city filed a lawsuit against the St. Louis-based corporation on Tuesday alleging it should help pay for costs associated with cleaning up PCB in its municipal stormwater system.