OSHA Hazard Information Bulletins
June 12, 1991
| MEMORANDUM FOR: |
REGIONAL ADMINISTRATORS |
| THRU: |
LEO CAREY
Director
Office of Field Programs |
| FROM: |
THOMAS J. SHEPICH
Director
Directorate of Technical Support |
| SUBJECT: |
Hazard Information Bulletin on Communication Tower Guy Anchor Corrosion |
The Directorate of Technical Support issues Hazard Information Bulletins
(HIBs) in accordance with OSHA Instruction CPL 2.65 to provide relevant
information regarding unrecognized or misunderstood safety and health
hazards, inadequacies of materials, devices, techniques and engineering
controls. HIBs are initiated based on information provided by the field
staff, studies, reports and concerns expressed by safety and health
professionals, employers and the public. Information is compiled based on
thorough evaluation of available facts, literature and in coordination with
appropriate parties. HIBs do not necessarily reflect OSHA policy.
The Denver Regional Office has brought to our attention that communication
towers may collapse due to the corrosion and failure of the guy anchors
resulting in serious injuries.
A 20 year old communication tower in North Dakota collapsed due to failure
of the anchor system. The tower is described as a three-leg, triangular
shape with each face measuring approximately 36 inches in width and 350 feet
in height. It was anchored at the base with all three legs embedded in a
concrete slab. In addition, it was guyed to three anchor points with 5 guy
lines attached to each anchor point (Attachment I).
The accident occurred when three workers from a tower servicing company were
conducting routine inspection and maintenance on the tower structure. The
crew checked the tower plumbness and added tension to guy wires. Two workers
ascended the tower to perform structural and antenna inspection. The tower
fell while the workers were ascending the tower. Both workers suffered
serious injuries.
The investigation revealed that the anchor shaft at one location had
separated at the point where it entered the concrete block (3' underground).
The separation occurred as a result of extensive corrosion activity on the
galvanized channel iron used as an anchor shaft.
There are thousands of towers with this type of anchoring system that are
susceptible to corrosion. Since corrosion can be caused by a number of
mechanisms, it is essential that the type of corrosion mechanism at a given
location be identified. An overview of the variables affecting corrosion is
provided in attachment II (courtesy of the Bismarck Area Office). It is
recommended that the inspection of a tower anchoring system includes regular
checking for corrosion of the steel anchor rods.
Please distribute this bulletin to all Area Offices, State Plan States and
Consultation Projects.
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