The U.S. Environmental Protection Agency has approved permits for two waste incinerators in the East Bay, despite objections from nearby residents who want the 1960s-era facilities closed. The permits, which go into effect June 30, were granted to Chevron Chemical Co., which operates a chemical plant in Richmond, and Shell Oil Co., which has an oil refinery in Martinez. Under the permits, tighter controls were imposed that limit burning to wastes generated on site, according to EPA spokesman Al Zemsky. "We can't say there is no risk" to nearby residents, Zemsky said. "But the risk involved is minimal." Henry Clark, spokesman for the West County Toxics Coalition, which wanted the burning to stop, said residents do not believe incinerators can be safe and fear their health problems have been caused by the burning operation.