AEG Monthly Meeting—Thursday, November 7

Chad W. Carlson, Ph.D.

Oroville Dam Emergency Response: Geologic Considerations for Spillway Repairs and the Engineering Geologists’ Contributions during Construction

Abstract: At 770 feet (235 m) high, Oroville Dam is the tallest dam in the U.S. An earthfill-embankment dam on the Feather River just east of the city of Oroville, California, Oroville Dam serves mainly for water supply, hydroelectricity generation, and flood control. The catastrophic failure of the Oroville Dam main spillway during use forced dam operations to stop release of reservoir waters to minimize damage. The subsequent rise in reservoir levels brought into use the emergency (auxiliary) spillway for the first time since dam completion in 1968. The rapid headward erosion across the native landscape toward the crest of the emergency spillway, and its potential for an uncontrolled release of flood waters, was the deciding factor to the downstream evacuation of nearly 200,000 residents on February 12th, 2017. Two and a half years later, with temporary and permanent repairs in place during the runoff seasons of 2018 and 2019, respectively, the majority of work at Oroville Dam is now complete and public access across the dam and spillways to the boat ramp has been restored.

Construction on or into competent rock was a primary consideration during repairs and new construction of Oroville Dam spillways. While the high strength (~50,000 psi) of metamorphic rock (amphibolite) provided sound foundation, localized zones of deeply-weathered bedrock were present across the site. The original construction of main spillway infrastructure on severely weathered bedrock in some places was determined to be the principal contributing factor to its failure. These weathered zones are commonly associated to regional deformation (e.g., foliation and periods of subsequent faulting/shearing). Detailed geologic mapping, exploratory drilling, and geophysical methods were used to assess rock characteristics prior to construction.

During construction, engineering geologists monitored drilling of Main Spillway anchors into bedrock, Secant Pile Wall installation at the downstream end of the Emergency Spillway, slope stability, and numerous other tasks onsite. The in-field engineering geologists’ real-time observations during construction verified spillway design specification were met and aided in the rapid completion of Oroville Dam repairs.

Biography: After 13 years working in Naval and commercial aviation, I found myself with an opportunity to change the direction of my professional life. Being a Fresno native, I returned home in 2005 and registered for courses at Fresno City College. Not long after, I chose to enter studies focused in the Geological Sciences. Having completed much of my lower division requirements, I transferred into the Earth and Environmental Sciences Department at Fresno State the fall of 2007. Working with Dr. John Wakabayashi, I completed a senior thesis interpreting the late Cenozoic uplift history of the central Sierra Nevada and graduated in 2009 with my undergraduate degree in Geology. My earlier goals of going into industry and applied geology were thwarted with my new found passion for geologic research. The fall of the same year I re-entered Fresno State to begin a Master of Science degree working with Dr. Christopher Pluhar. Using paleomagnetics of volcanic rocks I studied the vertical-axis rotations of crust east of the Sierra Nevada in the west-central Walker Lane. As my master’s work was drawing to an end, I considered my options and decided to try applying to a doctorate program. After acceptance to the University of Nevada, Reno, and while still writing my Master’s thesis, I began working with Dr. James Faulds in fall of 2011 to further the understanding of dextral shear accommodation and strain transfer at the transition between the northern and central Walker Lane. While juggling a teaching assistantship and coursework the first year in Reno, I managed to complete my Master’s in Geology the spring of 2012 at Fresno State. Combining detailed geologic mapping and paleomagnetic research, I finished my Ph.D. in Geology the summer of 2017. With little time to relish my accomplishment, I soon found myself full circle back to applied geology working on the spillway repairs of the Oroville Dam as an independent geologic consultant for InfraTerra, Inc. With my experiences from Oroville, and a new position with Lettis Consultants International, Inc., I look forward to becoming a licensed Professional Geologist while continuing my research endeavors to expand my knowledge base in all aspects of geology.

Chad W. Carlson, Lettis Consultants International, Inc. (InfraTerra, Inc.) carlson@nevada.unr .edu

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Job Announcements from BLM

A message from BLM: We are pleased to announce new, exciting positions available at BLM – BUREAU OF LAND MANAGEMENT.   It is our hope that qualified, career oriented individuals at your organization or other professionals known to you will actively consider this position and apply accordingly.  Efforts on your part to disseminate this information are greatly appreciated.

Job Description:  Civil Engineer;
Announcement Number:  NM-DEU-2019-0097;
Location(s) of position:  Roswell, NM, US;
Salary:  (USD) $42,053 – (USD) $80,912;
Applications will be accepted until:  08/27/2019.
For additional information on this job posting, please visit the vacancy details page at Monster Worldwide Inc. 

Job Description:  Financial Specialist;
Announcement Number:  CA-DEU-2019-0045;
Location(s) of position:  Sacramento, CA, US;
Salary:  (USD) $55,851 – (USD) $72,602;
Applications will be accepted until:  09/03/2019.
For additional information on this job posting, please visit the vacancy details page at Monster Worldwide Inc.

Indy Environment: Earthquakes, Yucca Mountain and Why Everyone is Talking about Walker Lane

By Daniel Rothberg, July 25th, 2019 – 2:00amIndy Environment:  Water & Land
Read the full article here: Earthquakes, Yucca Mountain, and Why Everyone is Talking about the Walker Lane

The Indy Environment newsletter breaks down reporting on water, public land and development. Sign-up here to receive it in your inbox. For suggestions or tips, email daniel@thenvindy.com.

Nevada is turning into California. The latest: Earthquakes.

“Without scaring people, we should be quite concerned that we could have a fairly sizable earthquake,” said Jim Faulds, the director of the Nevada Bureau of Mines and Geology.

Two recent Southern California earthquakes shook furniture as far as Las Vegas and have raised questions about the risk of tremors in Nevada. Geologically speaking, the Great Basin is a maze of fault lines, and much of it is still unexplored. Although most associate California with deadly quakes, Nevada is the third most seismically active state (after California and Alaska).

As state geologist, Faulds has spent a lot of time thinking about this issue and was recently featured in a WIRED story that looked at a fault system that extends through Western Nevada.

It is known as Walker Lane.

Walker Lane, Faulds said, accounts for about 20 percent plate motion between the Pacific and North American plates — and it could one day become the main boundary between the plates. But compared to the well-known San Andreas Fault, Walker Lane is disorganized, with smaller faults that make it difficult to assess earthquake risk. What if more than one fault ruptures at once? According to Faulds, there are more questions like that and more research needs to be done.

And there is a Yucca Mountain angle.

The proposed nuclear waste repository sits on the eastern part of the fault system. Last week, Faulds and the director of the Nevada Seismological Lab, wrote to Gov. Steve Sisolak urging more surveying of the area with new technology like LiDAR and new geophysical tools.

“The Walker Lane needs more thorough analysis and Yucca Mountain does as well,” he said.

In general, Faulds said the greatest earthquake risk is in Western Nevada along this fault, but the geological survey is working on a risk assessment for Southern Nevada as well. There have also been tremors across the Great Basin, including the 2008 Wells quake. I’ll be writing more about earthquakes, the science behind them, and the unknowns. I’ll also look at what it means for Western Nevada.”

It’s a Smart Time for Fellow Nevadans to Get Earthquake Ready

By Craig M. dePolo (Nevada Bureau of Mines and Geology)

Earthquakes are all about consequences, as the chance of a damaging one occurring is fortunately low (although upwards of 14,000 small earthquakes occur in Nevada every year). But the consequences, especially those that could have been prevented, are commonly unacceptable. The low chance of an event makes it easy to delay getting prepared with all the other pressing issues in life. But Nevada is earthquake country and damaging earthquakes will occur in the future. With the magnitude 6.4 and 7.1 earthquakes occurring not far from the Nevada border, it is a great time to finally get earthquake ready. Here is what we recommend:

1) Personal safety: Know what to do when strong shaking occurs.  DROP, COVER, and HOLD.  Can things fall on you when you’re in bed? If so remove these items or secure them. Identify a safe spot in each room where you can take cover to protect yourself from falling objects. Don’t forget to check your office as well.

2) Protect valuable items: The contents in our homes and offices can be tossed around during an earthquake and heavy or sharp objects are a common cause of injuries. Shaking hazards can be moved to a safer location, secured in place, replaced with a lighter item, or removed altogether. Some special consideration should also be given to items that are of value to you, such as family heirlooms, to protect them.

3) Prepare a disaster kit: This includes water, food, safety supplies, medications, pet food and other supplies to sustain you and your family for at least five days.

4) Prepare a disaster plan: Taking the time to put together a short plan helps a family reunite following a damaging earthquake and focuses attention on possible hazards around your house (such as telling children to stay away from a tall chimney). Discuss this plan with your family. Businesses should have disaster plans too.  

5) Check your house for earthquake weaknesses and begin to fix them: This step is the hardest and you may need some assistance, but protecting the investment of your home and having a place to shelter following an earthquake makes it worthwhile. Is your house bolted to the foundation?

These and other recommendations and further earthquake discussions can be found in Living with Earthquakes in Nevada at this link (open the link below and then click on the PDF link under Free Downloads):

http://pubs.nbmg.unr.edu/Living-with-earthquakes-in-NV-p/sp027.htm Future damaging earthquakes will occur in Nevada, and we want Nevadans to survive them well.