An investigation into last winter’s near catastrophe at Oroville Dam uncovered a litany of problems with how the dam was built and maintained, but one of them stands out: Even as workers built the dam, they were raising alarms about the eroded, crumbling rock on which they were directed to lay concrete for the 3,000-foot-long main flood control spillway.
The Sacramento Bee reports that construction reports from the fall of 1966 showed an abundance of loose clay, “shot rock” and “very little solid rock.” The surface was so crumbly, according to a state engineer overseeing the work, that a laborer at one point refused to do any more prep work until he got clearance from his boss. The contractor told the California Department of Water Resources it needed to dig deeper to find stronger rock.
But DWR limited the additional excavation work proposed by the contractor, a decision that investigators now say might have been motivated by money.
In the end, state officials didn’t care about those people living downstream. The deal back then was all about the money.
Nearly four decades later, in 2005, DWR officials took a similar stance when a coalition of environmental groups urged it to reinforce the weathered earthen hillside below another crucial component of the dam: its emergency spillway. This spillway – never tested – was intended to allow water to escape if the main spillway couldn’t release water quickly enough in a megastorm.
In 2005, DWR dismissed out of hand the notion that the emergency spillway needed strengthening. Critics said that decision also was driven by costs. Just as in the 1960’s, state officials didn’t care about those people living downstream. The deal back then was all about the money.
The warnings proved prophetic.
In addition to the erosion issues, the forensic team hired by DWR to investigate the Oroville emergency found that the main spillway was designed by an inexperienced engineer, plagued by a woefully inadequate drainage system and poorly maintained in the years that followed its 1968 completion.
The team also revealed that DWR had studies in its files, from well before the dam was built, that showed both spillways rested atop a foundation of wildly varying quality, some of it dangerously weak.
The investigators concluded the eroded rock and a poor drainage system below the main spillway allowed water to gather beneath its concrete chute. The voids made the spillway vulnerable to “uplift forces” that eventually caused it to crack open.
So why should anyone believe now that the deal it repair the dam has anything to do with safety? With California’s leaders, it’s always about the money.