EE PICKED UP A BASE LIFT JACK, WEIGHING APPROX 150 LBS. AT THE #73 SHIELD TO PUT BACK ON THE SHIELD PONTOON, EE FELT PAIN IN LOWER BACK BUT CONTINUED TO WORK THE REST OF SHIFT. EE WENT TO LOGAN REGIONAL MEDICAL CENTER ON 1/5/05, WENT TO FAMILY PHYSICIAN 1/10/05, WHOM HAS EE AWAY FROM WORK UNTIL AN MRI IS PERFORMED.