THE MORNING OF 3/6/99 VAC TRUCK OPERATOR WAS REPEATEDLY BENDING AS HE USED AND MOVED HOSES ON THE VAC TRUCK TO CLEAN SPILLED MATERIAL. AT APPROX 10:30 AM HE WAS IN THE SHORT EAST/WEST LIME TUN NEL UNDER #4 KILN WHEN HE BENT ONE MORE TIME TO MOVE AND HIS PREVIOUSLY INJURED SPINE ""WENT OUT"" AGAIN. DR DX LS STRAIN. RX PAIN MEDICATION AND OFF WORK.