An evacuation order was issued this morning for a Salinas flower nursery after a large nitric acid leak was detected. Firefighters and Hazardous materials experts arrived at Old Stage Greenhouses located at Old Stage Road and Herbert Road just after 9 a.m. to shut off the leak, which reportedly involved 500-gallons. no immediate threat to public health was reported. Fire officials say the nitric acid, which is used to make fertilizer, is maintained in a liquid form but vaporizes when it leaks. Containment was expected to take several hours.