Restrictions applicable to fugitive emissions

No person may discharge into the ambient air from any source of fugitive emissions, as determined or identified by the department, any air contaminant which exhibits an opacity greater than forty percent for more than one six-minute period per hour. Such visible emissions shall have been visibly transported off the property of emission origination and remains visible to an observer positioned off said property when sighting along a line which does not cross the property of emission origination.