Chemical company Orica has pleaded guilty to an ammonium nitrate leak at its Kooragang Island plant in March, 2011.
Today, in the Land and Environment Court, Orica admitted it failed to operate appropriately after a blocked valve caused the chemical spill into the Hunter River.
Orica previously pleaded guilty to three other environmental breaches, including a hexavalent chromium spill in August.
The matters were adjourned until next month
