Valero Refining Co. has agreed to pay nearly a quarter of a million dollars to settle violations of air quality regulations at its Benicia plant, officials said Monday. The Solano County refinery violated emission limits on nine occasions, reported hydrocarbon leaks from storage tanks six times, and had errors in a database that resulted in missed leak inspections for some valves, according to the Bay Area Air Quality Management District, which enforces air quality rules in the region.