The Oroville Dam Situation Explained

There has been a lot in the news lately about California’s Oroville Dam.  As someone who happens to live downstream of said dam, let me do my best to explain exactly what has been happening here.

The Oroville Dam made national news last weekend when nearly 200,000 downstream residents were ordered to evacuate their homes and seek refuge on higher ground.  The fear at the time was that erosion on Oroville’s emergency spillway could cause the dam to fail and send a “30-foot wall of water” into surrounding communities.

This erosion occurred as a result of Lake Oroville reaching maximum capacity and overflowing its so-called “emergency spillway” which is little more than a concrete lip perched precariously above a wooded hillside.  Next to this ensemble is the main spillway, a set of gates and a long concrete chute leading down to the Feather River below.  At the time of the lake’s overflowing, this main spillway had already been severely damaged and the Department of Water Recourses (DWR) had reduced the flow of water down the chute in order to prevent further damage.  However, the combination of this reduced outflow and continuous heavy rain swelled the lake level to over 100% of capacity.  Water began flowing over the top of the emergency spillway and proceeded to eat away at the hill next to the dam.  This prompted the evacuations of the downstream communities.

Fortunately the dam did not collapse as feared.  The DWR increased the flow out of the main spillway (despite the damage there) and the water level in Lake Oroville was eventually lowered enough to stop the erosion of the emergency spillway.  Local residents were allowed to return to their homes days later.

As with many of California’s problems, this potential disaster was completely predictable.

In 2005, a coalition of environmental groups submitted a report to the DWR concerning potential damage to the emergency spillway should it ever have to be used.  The report explains that the Oroville dam was designed to be operated in conjunction with a second dam downstream to regulate floodwaters.  Oroville’s main spillway and its earthen emergency spillway were deemed sufficient for flood control as long as the second dam could absorb the impact of increased flows out of Lake Oroville during times of extreme flooding.  The second dam would act in effect as a giant safety valve for water flowing out of Lake Oroville.  This second dam, however, was never built.

Lake Oroville has been operating since the 1970s as though it were part of the two-dam system that was initially designed but never completed.  This means that the main spillway alone has always been insufficient to control extreme floodwaters as was witnessed in 1997 when the lake nearly overflowed.  Water was released at a rate higher than intended, and many downstream levees broke as a result of the increased pressure.  This event is cited as the primary reason the 2005 report was compiled.

The report goes on to describe that should excessive floodwaters force Oroville to overflow, the “discharge area below the emergency spillway” would experience “extensive erosion,” and that since the “area downstream from the emergency spillway crest is an unlined hillside, significant erosion of the hillside would occur.”  As we all saw last weekend, this is exactly what happened.

The report suggested that lining the spillway area in concrete (“armoring” the hillside) or modifying Oroville’s operating manual to account for the lack of the planned-but-never-built second dam would significantly reduce the risk of erosion and damage to the dam’s infrastructure.  The DWR and the Federal Energy Regulatory Commission completely ignored this report.

In fact, the California state government so completely ignored the warnings about Oroville, that they made sure to divert to it exactly $0.00 worth of the $34.5 billion received from the 2009 Obama stimulus money.  Instead, super important projects like sidewalks, high-speed rail, and the not-crumbling, perfectly safe Folsom Dam received that federal funding.

To make up for that oversight, California Governor Jerry Brown, as part of President Trump’s proposed new stimulus package, made sure to again ask for $0.00 for Oroville.  Credit where credit is due though, Governor Brown was quick to beg ask the President for federal funds to help cleanup last weekend’s mess at the Oroville spillway (right after declaring that California, as the world’s sixth-largest economy, was doing just fine without federal help).

At least that high-speed rail project is on-schedule and under budget.

So there’s the dam truth.  The simplest explanation of these events is that liberals care far more about trains than public safety and essential infrastructure.

#Priorities.

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Russell Patten

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