More than seven years ago, a river valve system designed to release water from the Oroville Dam was damaged while being tested, according to an Occupational Safety and Health Administration report.

On July 22, 2009, several workers were deep below the reservoir operating flow controls to a river valve chamber in the Oroville Dam, according to the OSHA report. When the flow reached 85 percent, suction pulled a breakaway wall downstream into a 35-foot diversion tunnel, cutting lights and nearly sending three workers to their deaths in the roaring current.

One of the workers who was badly injured survived by clinging to a bent rail, where he was struck by tools and equipment being sucked inexorably into the tunnel. He was hospitalized for four days with head trauma, a broken leg, broken arm, cuts and bruises.

Osha sanctioned the Department of Water Resources with six citations, including five classified as serious, and the department was initially fined $141,375. Two of the “serious” citations were overturned on appeal.

This river valve system was one of the first parts of the dam to be built when the dam project started in 1961, because its initial purpose was to divert the river while the dam was under construction. After that, it served various purposes, including as a possible emergency release valve.

But all that ended with the damage from the 2009 incident, according to a 2012 Oroville Mercury Record story. At that time, the department was embarking on a study to determine under what conditions the river valve “and supporting infrastructure” could be used safely in the future. Issues to be explored included whether new river valves would be built and isolation of river valves from the lake.

“The agency also has the option to do nothing,” the 2012 story said. A time frame of two years was given for completion of the study.

This week's crisis, set off when erosion to an emergency spillway threatened to compromise the structure and release a massive amount of water onto the town below, brings into question the viability of relying on the three other water release mechanisms.

Whether a fourth, properly functioning river valve could have drawn off sufficient water to avert this week's crisis is a question that remained unanswered Monday afternoon.

ABC10 reached out to the Department of Water Resources for comment, but no response yet.

It was also undetermined what conclusions the study reached, although a DWR publication dated Winter 2014-15 fleetingly referred to river valves in a profile of Pat Whitlock, upon his appointment as Oroville Field Division Chief.

Listed on Whitlock’s “to-do” list was “modernizing Oroville Dam’s low-water river release valves” among “much more.”