Orica has begun producing ammonia at its Kooragang Island plant.
The plant’s restart was put on hold twice, due to a compressor issue and a minor nitric acid spill on site.
According to the explosives manufacturer the ammonia and ammonium nitrate plant closures "are estimated to have impacted earning before interest and tax by approximately $90 million this financial year".
The closures also negatively affected the Hunter Valley’s mining operations, as it caused a shortage of explosives.
Orica came under fire form the EPA and community groups over the initial and subsequent spills from its Kooragang Island, Port Botany, and Port Kembla plants.
Following these spills the EPA introduced more stringent environmental reporting laws.
Despite concerns over the initial 8 August spill, the EPA has since revised the results of its earlier sample.
The revised swab results and resulting estimates of the chromium six emissions at the Kooragang Island site were reportedly significantly less than those originally published after the initial leak.
Original estimates put the spill at between ten kilograms and 20 kilograms, however the new test have corrected this to only one kilogram, or approximately 35 grams to 60 grams of chromium six spread across the Stockton area.
These new results have not changed the focus of the company.
Graeme Liebelt, Orica’s chief, said "these revised figures do not change the fact that we had an incident at Kooragang Island that we deeply regret.
"We have acknowledged that our response at the time was not what the community expected and we are working hard to regain trust and improve our communications."