FEMA recently announced that they would not pay the full amount of dam repairs to the Oroville Dam in California. In fact, they’re paying about half the amount request—only $333 million. In February 2017, 188,000 residents were evacuated who lived downstream from the dam.
100 Year Storms Now More Frequent
That year, California had one of the wettest winters in history, causing massive flooding all over the area. The spillway was opened to release pressure, but the dam was still weakened by the massive amounts of water trying to push its way through. Then on February 11th, the emergency spillway was opened for the first time since it had been built in 1968. It did not do well under the pressure of so much water forcing its way through the dam.
Engineers discovered a large hole in the concrete near one section of the foundation. This caused alarm as many experts thought the dam might not be strong enough and could give way. Due to heavy rainfalls, the engineers were forced to continue using the spillway even though the hole was growing bigger. Rainwater along with debris kept pushing its way through the hole making it even larger. Then on February 12th, officials announced a mandatory evacuation.
Later, once the danger had passed, engineers inspected the dam to see what damage had been done. In addition, they worked to extend a cutoff spillway under the damaged area of the emergency spillway in order to stop further damage from occurring.
DWR director Grant Davis tried to reassure the area residents, saying, “Lake Oroville’s main spillway is indeed ready to safely handle winter flows if needed.”
Dam Repairs to be Done in Phases
Repairs to the dam have already been started and will be completed in phases. During phase 1, construction teams worked to rebuild the top section of the spillway, fortifying it in various ways. But in October of 2017, hairline cracks were discovered in the newer areas where crews had worked to fortify and rebuild the dam. At this point, engineers had to reassess their approach to rebuilding and repairing Oroville Dam.
One of the major reasons for the high cost of repairing the dam has been cited as the relocation of surrounding power lines. Engineers also found that the bedrock under the spillway was weak. This made it necessary for crews to excavate deeper, adding more concrete.
Many climate experts believe that natural disasters will increase as time goes by. That means more 100-year storms, heavy rainfalls, tornadoes, hurricanes and earthquakes. The Oroville Dam and others like it must be ready. They must be strong enough.
An Interesting Side Note
The U.S. Army Corps of Engineers recently released its update to the National Inventory of Dams. According to this report, the average age of America’s 91,468 dams is 57 years. It is estimated that dam repairs for all of them adequately will cost about $64 billion. The report claims that $22 billion is needed immediately to repair the most critical dams that have the highest potential to fail and cause massive damage and loss of life.