Three decayed chemical drums and soil soaked with toxic chemicals were dug up at an Anaheim paint manufacturing plant by investigators acting on an anonymous report. The firm, W. C. Richards Co., located in an industrial area, was charged two years ago with violations that county officials called one of the most serious illegal dumping cases in the county's history. Its former vice president is scheduled to stand trial March 16 on felony charges. Officials said they were investigating buried drums of chlorinated hydrocarbons, which are carcinogenic, to determine whether to press new criminal charges against the company. Ground water will also be tested for contamination, they said.