NORTHAMPTON — The Coca-Cola Co. is shutting down its Northampton plant and subsequently laying off over 170 workers later this year, according to a notice to state officials reviewed by the Business Journal. The Atlanta-based beverage giant is planning to permanently close its production facility located at 45 Industrial Drive in Northampton on Dec. 15 this year, the company said in a June 15 notice filed in accordance with the federal Worker Adjustment and Retraining Notification Act.