EMPLOYEE PLACED A 5 GALLON BUCKET FILLED WITH MATRIX SAMPLE, WEIGHING APP 65 LBS ONTO THE SIDE OF THE MIXING TANK IN PREPARATION OF POURING THE SAMPLE INTO THE TANK. WHEN EMPLOYEE REACHED TO T URN ON WATER VALVE, BUCKET SLID OFF MIXER. EMPLOYEE GRABBED THE BUCKET AS IT WAS FALLING, RESULTING IN AN ACUTE SPRAIN OF RT PECTORALIS MUSCLE IN HIS CHEST.