Abstract: AT APPROXIMATELY 12 NOON ON APRIL 28, 1987 EMPLOYEE #1 WAS SANDBLASTING INSIDE A WATER STORAGE TANK ABOUT 30 FEET ABOVE THE BOTTOM OF THE TANK. HE WAS SITING ON A METAL BOATSWAIN CHAIR ATTACHED TO A "WHIRLEY GIG" BOOM WHICH EXTENDED 47 1/2 FEET FROM THE TANK CENTER. THE BOOM CONSISTED OF 10 FOOT ALUMINUM SECTIONS WELDED TO CONNECTION PLATES. A WELD BROKE ABOUT 30 FEET FROM THE CENTER POINT, CAUSING THE BOOM TO COLLAPSE. EMPLOYEE #1 FELL ABOUT 30 FEET TO THE BOTTOM OF THE TANK. A LIFELINE, SAFETY BELT AND LANYARD WERE USED. HOWEVER, THE EMPLOYEE FORGOT TO TAKE UP THE SLACK WHEN HE REACHED THE WORKING ELEVATION. A BUTTERFLY CLAMP WAS USED ON THE LIFELINE. ALSO, ABOUT 350 POUNDS OF HOSES WAS DRAPED OVER THE BOOM AT THE BREAK POINT, CAUSING ADDITIONAL STRESS ON THE WELD. EMPLOYEE #1 SUFFERED A CRACKED PELVIS BONE.