March Meeting

Tuesday • March 20th 2018 • 6 – 9 PM

Old Market Pub • 6959 SW Multnomah Blvd, Portland, OR

6 PM — Social

6:45 PM — Dinner

(Salad & Pizza)

7:30 PM — Presentation

Reservations by 4 PM Friday, March 16th. Dinner $25*, Students FREE with RSVP ($5 if no RSVP). *There is a $2 surcharge for those who do not reserve by the deadline

Reservations can be made here: RSVP by 4pm Friday, March 16th

Rattlesnake Hills Landslide: Overview and

Guest Speaker: Charlie Hammond

The Rattlesnake Hills Slide is located less than 3 miles south of Yakima, WA, on the southeast side of Union Gap, where the Yakima River cuts through an east-west-trending
ridge. The ridge is a tectonic anticline known as Rattlesnake Hills (to the east of the gap)  and Ahtanum Ridge (to the west) that rises 2,000 feet above Yakima Valley. The slide is on the south flank of the asymmetric anticline, which dips 10 to 20 degrees at Azimuth 190 degrees. Rock formations in a quarry at the site are Saddle Mountains Basalt and Wanapum Basalt of the Columbia River Basalt, with an interbed of the Ellensburg Formation.

The Saddle Mountains Basalt overlies a 5-foot thick sedimentary interbed of clay, silt, sand and fine gravel, including coal and lahar seams. The basalt has tight to open joints and fractures and is rippable at the quarry. The Ellensburg interbed also exhibits shear textures, interpreted to be associated with bedding-parallel slip and the tectonic folding. The basalt formation is essentially dry. Surface water readily infiltrates the ground, even within the floor of the quarry.
The Rattlesnake Hills Slide is a translating block landslide approximately 4 million cubic
yards in volume, 1,700 feet long (north-south), 850 feet wide (east-west) and 200 feet thick. The slide block is in tension and is moving downdip at relatively constant rates that vary across the slide from approximately 0.17 to 0.25 feet per day (2 to 3 inches per day).

Groups that are monitoring the landslide include: Columbia Asphalt & Ready-Mix, Cornforth Consultants/Landslide Technology, Washington Geologic Survey, Washington Department of Transportation, Yakima County, and Yakama Nation. In addition, other monitoring assistance and research is provided by: Pacific Northwest Seismic Network, University of Washington, University of Oregon, and representatives from the Embankments Dams and Slopes Committee of the American Society of Civil Engineers. Regional experts from UW and WSU have also volunteered their experience.



Mr. Hammond has 30 years of experience as an Engineer Geologist investigating landslide and rockfall hazards and risks, seismic hazards, soil and rock material sources, groundwater and dewatering, soil and rock tunneling, and other complex geologic hazard considerations.

Mr. Hammond is a registered professional engineering geologist in Oregon and Washington and has a Bachelor of Arts degree in Geology from Whitman College in Walla Walla, Washington, and a Master of Science degree in Geology from New Mexico Institute of Mining and Technology in Socorro, New Mexico.