Hawaii Dept. of Labor Says Weak Soil Led to Worker's Zip Line Death

HIOSH said that the zip line company did not use any objective methods to verify that the anchors it installed could support the weight of the towers, cables, and riders or that the guy system could meet the requirements of industry standards.

The Hawaii Department of Labor & Industrial Relations Occupational Safety and Health Division (HIOSH) has completed an investigation of the Sept. 21, 2011, zip line accident that claimed the life of one employee of GoZip LLC (GoZip) and seriously injured another.

The investigation found that the zip line tower collapsed because the ground anchors were installed in weak soil. HIOSH said that GoZip failed to take reasonable precautions to ensure that the anchors could support the load.

At the time of the accident, one employee was test-riding the zip line and another was on the platform of a tower at the upper end of Line 8 when the ground anchors supporting the tower abruptly pulled out of the ground.

The poles that held the platform came out of the ground and the tower collapsed, causing the cables to sag into the stream valley.

The employee riding the zip line fell approximately 200 feet and suffered fatal injuries. The employee on the platform fell approximately 30 feet and suffered serious injuries.

The state has proposed a $13,500 penalty. GoZip is contesting the matter and a hearing will be scheduled before the state Labor Relations Board.

“For zip line installers, this tragic accident demonstrates the importance of basing design and construction decisions on measurable objective information for the safety of workers as well as the general public,” said DLIR Director Dwight Takamine. “Unfortunately, this is another workplace fatality that was preventable, and we share the sorrow of the family, friends, co-workers, and others affected by this incident.”

The owner of GoZip is a member of the Association for Challenge Course Technology (ACCT), an organization that serves the zip line industry, and it served on an ACCT committee that wrote standards for installing zip line courses.

The ACCT standards require that guy systems on zip line towers, including ground anchors, be capable of supporting two times the expected load.

HIOSH said that GoZip did not use any objective methods to verify that the anchors it installed could support the weight of the towers, cables, and riders or that the guy system could meet the requirements of the ACCT standard.

Citations under contest by the employer include:

  • Failure to do everything reasonable and necessary to protect the life, safety, and health of employees by not ensuring that the ground anchors and guy cable system at Line 8 could support the loads imposed by the tower, zip lines, and weight of human riders without failure.
  • Failure to ensure the side rails of an extension ladder used to provide access to the Line 7 landing tower, from which employees crossed a suspended bridge to the Line 8 takeoff tower, extended at least three feet above the edge of the landing surface.
  • Failure to ensure employees riding the zip line used helmets.

A professional engineer hired by GoZip to conduct geotechnical testing following the accident concluded the subsoil in which the anchors were installed was Pahala Ash, a fine particulate mineral that has the appearance of normal soil but loses up to 90 percent of its natural strength when disturbed.

The engineering report stated much of the soil along the Hamakua Coast that appears to be red dirt might in fact be Pahala Ash. This raises serious concerns about the stability of structures that rely on ground anchors for support, including zip line towers at other locations on the island.

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