EMPLOYEE STATED THAT HE WAS CLEANING ON THE BOTTOM FLOOR OF THE PLANT AT THE B SIDE 1/2 BY 0 PUMP. THERE IS A SIDE DITCH BESIDE THE B SIDE 1/2 BY 0 SUMP, AND THE GRATING WAS REMOVED FOR CLEAN ING PURPOSES. HE FORGOT THAT THE GRATING HAD BEEN REMOVED AND STEPPED INTO THE DITCH, HURTING HIS LOWER BACK WHEN HE FELL.