A federal judge ruled that Occidental Chemical Corp. is liable for the multimillion-dollar cost of cleaning up the Love Canal landfill at Niagara Falls, N.Y. After nine years of deliberations, U.S. District Judge John Curtin said Occidental produced the wastes that created the environmental problem and stored them in a way that would eventually result in toxic leakage. He said Occidental's liability would be determined in court proceedings involving claims against Occidental by other parties, including the state of New York and some residents. Previous estimates have ranged above $250 million. Occidental, formerly Hooker Chemical & Plastic Co., contended that it was not responsible for the site after 1953, when it sold the property. Frank Ashley, a spokesman for Occidental Petroleum Corp., the parent of Occidental Chemical, said the company would appeal.