Go to Robert S. Kerry Lock and Dam (#15), Oklahoma, this
week and you might see Maj. Doug Droesch and David Jarvis, both of U.S. Army
Corps of Engineers – Tulsa District, dangling from ropes on the dam’s gates.
Droesch, a structural engineer in the civil design section,
and Jarvis, hydraulic steel structures engineer for maintenance and operations
and the bridge program manager, are in the process of inspecting the dam’s
tainter gates for a periodic inspection.
The technique they are using, called rope access, is quite
different from the old way of doing things, called fall arrest, they said.
With the fall arrest system inspectors climb onto the
structure, relying on their ability to scale the gates with their hands and
feet. If they fall the self-retracting
lifeline of the fall arrest system will catch them, but it also may allow them
to swing into the structure.
The rope access system is different because the inspectors
are actually suspended from the top of the structure, allowing them to get into
positions they couldn’t get to if they were just climbing, said Droesch,
allowing them to more thoroughly and more efficiently inspect the dam.
At some point in the 1980s, said Jarvis, inspectors on large
structures realized they could reach difficult areas using techniques from
ascending and descending cliffs. That
has translated into industrial rope access and three levels of training for
rope access technicians. Level one rope
access technicians are the people who perform the rope access work. Level two technicians do rope access work and
safety evaluations, and level three technicians are responsible for the work
While rope access requires a level three technician on site
to ensure the rigging and practices are safe, it still requires less people and
equipment than using a crane or cherry picker, said Jarvis.
“For us to do our inspection really requires only one other
person to be our safety lead and level 3 rope access technician,” said Jarvis. “He sets up all the rigging, the anchors,
ties all the knots on the ropes.”
The periodic inspection occurs every 5 years and determines
cost, repair methods and repair techniques for the future, said Jarvis.
“As Major Droesch and I are down on the gates we’re
identifying areas that may have to be replaced, areas that will have to be
painted and areas that we may have to reweld things,” said Jarvis. “We also report to management and say ‘these
are the things we could do to better maintain the gates and give them longer
Droesch said they look at critical areas of the gates where
there are higher forces and higher stresses on the steel structure.
“We’re looking at welds, looking for cracks in the welds,
looking for corrosion, any rust that will start to deteriorate the metal,”
Droesch said. With less metal because of
corrosion the ability to resist the water behind the gate is lessoned as well,
he said. “So we’re checking all of that to see what the condition of the gate