The infant-formula company is selling the site and related assets for 307-million dollars, and will use the proceeds to pay down debt.
Synlait says the sale is a "defining moment", which comes as the company reports an annual loss of almost 40-million dollars.
Meanwhile, Fonterra's confirmed farmer-shareholders will vote on the proposed sale of its consumer business on October 30.
The Fonterra Co-Operative Council is now formally backing the sale.