Sacramento Branch Meeting-The Oroville Spillway Incident, Geology and Why It Matters

The Sacramento Branch is pleased to present:

The Oroville Spillway Incident, Geology and Why it Matters

Holly J. Nichols, CEG
Senior Engineering Geologist
California Department of Water Resources


The Oroville Dam is located in northern California just outside the town of Oroville. The dam and appurtenant structures were constructed in the mid-1960s. There are two spillways:  a gated, concrete-lined chute and a concrete monolith weir with an unlined spill area. The dam site is located in the foothills of the western Sierra Nevada within the Smartville Complex, which has a roughly north-south regional structural trend. The Oroville Dam and spillways were constructed in an unnamed unit of the Smartville Complex, composed of Jurassic meta-volcanic rocks consisting primarily of amphibolite. The amphibolite has a strong structural fabric in roughly the north-south direction and is cross-cut by shears oriented about N50E (roughly parallel with the gated spillway) and lower angle shears dipping towards and away from the reservoir. On February 7, 2017, a hole formed in a portion of the concrete-lined spillway at Oroville Dam. Continued operation of the gated spillway caused additional erosion and damage to the concrete structure. The areas of deepest erosion occurred in portions of the spillway that were mapped during original construction as strongly weathered to decomposed amphibolite rock. On February 12, 2017, during operation of the emergency spillway, rapid, deep headward erosion was observed in the northern portion of the unlined emergency spillway. This presentation will discuss the geologic conditions that were understood at the site prior to construction, the geologic conditions that were documented during construction, and what we have learned about the geologic and groundwater conditions since the spillway failure.


Holly Nichols has been with the California Department of Water Resources since 2008, after working in the private sector for several years in Southern California. She is currently a Senior Engineering Geologist in DWR’s Division of Engineering. She has worked on a variety of water infrastructure design and construction projects including pipelines, canals, and dams throughout California’s State Water Project. She received her B.S. in Geology from the University of Texas in Austin, and her M.S. in Geology from Washington State University, and is a licensed Engineering Geologist in California. She has been AEG’s Sacramento Chapter Vice Chair for several years and has spent most of 2017 as the lead geologist for the Oroville Spillway Recovery efforts.


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About California Laboratory Services:

CALIFORNIA LABORATORY SERVICES (C.L.S. Laboratories, Inc.) is a well-established, State certified small environmental laboratory committed to provide the environmental industry with the highest quality testing service. Our laboratory is located in Rancho Cordova, CA. Our laboratory performs work under State certification programs. We are certified in the State of California Environmental Laboratory Accreditation Program (#1233). Our laboratory performs organic, inorganic & bacteriological analyses of:

  • Drinking Water
  • Solid waste
  • Petroleum fuels
  • Waste water
  • Soil
  • Sludge & Hazardous Waste

Founded in 1982, with facilities encompassing over 16,000 square feet of lab space, housing high-resolution instrumentation and highly trained chemists, we are positioned to offer your company a wide range of first class environmental analytical chemistry that satisfies State and Federal regulations such as:

  • CCR Title 22 Drinking Water
  • CERCLA (Superfund)
  • NPDES Permits
  • UST Sites
  • RCRA
  • EPA


All Proceeds to Benefit Science Students

The GRA Sacramento Branch has a history of supporting university-level science students. Our Scholastic Sponsorship Program is an opportunity to publicize your business while contributing toward a good cause. The cost is minimal; if interested, please contact Linda Bond at (530) 757-1500 or


Social Hour - 5:30-6:30 p.m.
Announcements & Dinner - 6:30-7:30 p.m.
Presentation - 7:30-8:30 p.m.
Usual great food, including two meat entrées, salad, rice, potatoes, vegetable and Iced Tea. A No-host beer and wine bar will be available.


Members: $27.00
Non-Members: $32.00
Students: $10.00

  • If you register after Noon on Monday, April 9th, or walk-in, a $3.00 surcharge will be added to the meeting cost.
  • Cancellations must be made by Noon on Monday, April 9th.

If you have questions about the meeting, please telephone Rodney Fricke at 916-407-8539 or email him at  For questions about Sacramento Branch in general, including submittal of your ideas and/or desires for future presentations, please telephone Linda Bond at (530) 757-1500 or email her at


May 9th: Rob. M. Gailey, PG, CHG, UC Davis and R.M. Gailey Consulting Hydrogeologist, Domestic Well Supply Reliability During Drought: Stress Testing for Groundwater Overdraft and Economic Costs

June 6th, Kirby Brill, Former General Manager of the Mojave Water Agency, Southern California David Keith Todd Lecturer (invited) in conjunction with the GRA first annual Groundwater Sustainability Agency Summit

July 11th: Chris Bonds, Senior Engineering Geologist, California Department of Water Resources, State May Atom-Blast for Water: The Plowshare Program and DWR’s Connection

August 8th: NGWA 2018 McEllhiney lecturer Todd Halihan, Ph.D, Professor of Geology, Oklahoma State University, Chief Technical Officer for Aestus LLC, The Future of Water: Data or Instincts?

September 12th: Glenn Meek, CA State Water Resources Control Board, Update on the Central Valley Salts Program


Event Files


Wed, April 11, 2018
5:30 p.m. - 8:30 p.m.

Event has ended


Aviators Restaurant
6151 Freeport Blvd
Sacramento, California 95822

Aviator's Restaurant at the Sacramento Executive Airport
6151 Freeport Blvd., Sacramento, CA
Aviator's Restaurant is located within the aircraft Terminal Building.
Plenty of free parking.