Ventura, Calif.-The investigation is still underway into the cause of a tractor-trailer rollover March 17 on Highway 26 that sent 4,500 gallons of UAN 32 spilling on the freeway and into the highway drainage system, according to the Venture City Fire Dept. One person, identified as a passenger, suffered moderate injuries. Firefighters diked the flow into the drainage system while environmental health crews responded to oversee the cleanup operations, with help from transportation and fish and game personnel.