Update: Oroville Dam ‘green spot’ no cause for alarm, DWR says in new report
AGENDA 21 RADIO
BY PAUL PRESTON
First Published August 8, 2017
Updated September 4, 2017
“dam experts universally express doubt about the finding including Dr. Robert Bea and dam expert Scott Cahill. DWR after months of not telling the truth to the public cannot be trusted with the lives of the over 1 million people who were minutes from being killed on February 12, 2017 by their gross negligence”.
2017 REPORT ON GREEN SPOT AT OROVILLE DAM
After months and months of telling different stories to the public about the ‘green spot’ on the Oroville Dam the California Department of Water Resources has released a long awaited report on the spot. Ever since the February 12, 2017 incident where DWR officials mismanaged water flows at Oroville Dam and made the fateful decision to allow slow the rate of water flowing over the damaged main spillway and overtop a never before used emergency spillway which forced the evacuation of over 188,000 people down stream of the Oroville and endangered the lives of over 1 million people in the inundation zone the ‘green spot’ has been a source of concern. Now a report issued by the DWR’s ‘independent’ Board of Consultants says there are no worries!
In the report below filed by Risa Johnson keep in mind the report is suspect because dam experts universally express doubt about the finding including Dr. Robert Bea and dam expert Scott Cahill. DWR after months of not telling the truth to the public cannot be trusted with the lives of the over 1 million people who were minutes from being killed on February 12, 2017 by their gross negligence.
Oroville >> The state Department of Water Resources maintains in a report issued Wednesday that the “green spot” on the face of the Oroville Dam is caused by rain and poses no threat to the integrity of the structure.
DWR shared its findings on Friday with the Board of Consultants, the independent group analyzing the damaged spillway’s current operations and design plans. The board agreed with DWR’s analysis, said Erin Mellon, DWR assistant director of public affairs, in an email Wednesday.
The spot is not a cause for worry because, in part, it is dry in the summer and green in wet months, every year, the 28-page report states. It also says seepage measurements at the base of the dam have stayed low since original construction.
“If any water did make its way through the dam’s core, it would be intercepted by a vertical drain, preventing it from flowing to the downstream area of the dam where the vegetation is located,” Mellon wrote in an email.
The release of this report comes as a UC Berkeley group headed by risk management expert and professor Bob Bea called into question whether the spot may be a sign of differential settlement, which could cause the dam to spring a leak, in a 124-page report the group published in July. Bea said he was dissatisfied with DWR’s previous explanations that the green area was caused by rain or was a natural spring, because it is concentrated in one place, visible in wet as well as dry months and seemed to be expanding in a horizontal direction and running uphill. DWR officials maintain the green spot is there during wet months and goes away every year during dry periods.
Mellon previously said DWR’s report would be out the first week of August. She said it took longer that expected to release the report because the department wanted to get some more opinions on it, including those of Board of Consultants members last week.
EXPLANATION FROM DWR CONSULTANT
Mellon set up an interview Wednesday afternoon with Leslie Harder, former chief of engineering for DWR, to help explain the report. After working for DWR for 30 years, Harder has now been a consultant for the department for 10 years.
He said the vegetation area is visible in wet months because rain settles there, and as to why it sits in this one spot, splayed horizontally — it has to do with the way materials were placed when the dam was built. “Dirtier” material was put there unintentionally by a contractor, he said.
“The rainfall hits stratified layers, so it can’t go down,” Harder said. “There is no safety problem that exists.”
He said DWR is not considering trying to remove the “green spot,” as though it may pose a PR problem, it is not a safety issue. In response to Bea’s concerns differential settlement could be occurring, Harder said several measures were put in place when the dam was originally built to keep that from happening.
Harder said if differential settlement were to occur, the original designers planned for a separation of five feet and in the last 50 years, there has been a shift of 10 inches.
He also added that the “green spot” has been there since the dam’s original construction, before the reservoir was filled, something that DWR officials have previously stated.
One of Bea’s calls to action for the department was to reinstate piezometers, which measure the pressure of water, that have been out of commission for decades. Harder said measuring the amount of water in the seepage collection pool, as opposed to using piezometers, is the best way to know if there were a leakage issue. He said there is an alarm system in case the pool gets unusually high.
“There is hardly any water seeping through,” he said. “(DWR has) been taking manual readings over the last 50 years.”
Seepage through the weir has been measured at 10 gallons per minute during the dry season, which the report notes is “extremely low for a dam this size” and at 100 gallons per minute during wet periods, which has been consistent since original construction, according to the report.
Assemblyman James Gallagher, R-Yuba City, said Wednesday he had not yet reviewed the report but was glad it was finally out.
“This ‘green spot’ assessment is long overdue,” said Gallagher. “North state residents asked for a detailed explanation months ago. I’m not a dam safety engineer, but I do look forward to reviewing the assessment and hearing what other outside experts have to say in response.”
The UC Berkeley team was not available for an interview before the deadline for this story.
Reach reporter Risa Johnson at 896-7763.
