Reigning in the Looming Landslide in Kitsap County

As the Washington Boulevard landslide continues to move, it threatens to cut numerous Kingston residents off from the town and emergency responders.

Since a significant slide in 2006, Aspect has provided geotechnical services at Washington Boulevard, including gathering data and monitoring and studying movement along the slope. Recently, Kitsap County Public Works decided to implement a slope dewatering system to remove groundwater from the landslide mass and increase the stability of the hillside and roadway.

Aspect’s Andy Holmson provides some insight to the solution in this Kitsap Daily News article.

How Will We Hold Up to The Cascadia Megaquake?

Two recent articles in The Seattle Times explore how the Pacific Northwest's infrastructure will be affected by the next major earthquake.

New Cascadia quake analysis shows building retrofits could save many lives

How to survive the Cascadia Earthquake? Tips from seismologist Lucy Jones, ‘the Beyoncé of earthquakes’

Back in 2015, our very own Dave McCormack chimed in with his thoughts in response to the now infamous New Yorker story, The Really Big One

A Geologist's Thoughts on the Pacific Northwest Mega-Quake Story

Source: USGS

Source: USGS

The Geology of Central Washington's Rattlesnake Ridge Landslide

Geology is on everyone’s mind in Yakima County as officials grapple with the ongoing Rattlesnake Ridge slide and how to help the community below it. This drone footage captures the surface features of the slide in detail. 

Given the geology of the area, Aspect’s Principal Engineering Geologist Dave McCormack summarizes the likely forces behind the slide: “Geologic studies have shown that slides of this nature are fairly common on the flanks of the numerous anticlinal ridges in central Washington. While most are ancient and have not moved during recent history, there are examples, including the Nile Valley landslide of 2009, where old slides have reactivated, or new slides began. These slides occur where basalt flows are interbedded with sedimentary strata. While the basalt strata may be relatively strong, the sedimentary interbeds are often weathered and weak.

When the gravitational driving forces acting on these dipping strata exceed the resisting strength of the weathered sedimentary strata, they begin to slide. There are multiple factors in the delicate balance of gravitational forces versus resisting strength, including the properties of the rock, degree of weathering, groundwater levels, the geometry of the slope, etc. 

Triggers for activation of landslides can include increases in groundwater level, strong earthquake shaking, or changes in slope geometry from natural causes like river migration, or human-caused grading. Because of the multiple factors involved, teasing out the exact triggers of a slope failure can be challenging, and the expected type of failure (fast debris runout, slow creeping failure, rockfalls, etc.) difficult to predict.” 

Geologic insight will continue to be relied on as the slide keeps moving.
 

Worldwide Great Shakeout: Are You Earthquake Prepared?

Stocked up? Emergency plan written and communicated? Even if you feel behind, just starting the process is a great first step.

shakeout.jpg

Today is the Great Shakeout in the Pacific Northwest and worldwide.

See the resources below to get prepared in our “seismically rich” part of our world, including thoughts by Aspect’s very own geologic expert Dave McCormack on the science and potential of the Cascadia Subduction Zone i.e., the “Big One” occurring:

Great Shakeout Earthquake Drill

A Geologist’s Thoughtson the Pacific Northwest Mega Quake Story

Get Ready to Rumble: A Guide to Earthquake Preparedness by the Seattle Times

What Can I Do? Emergency Guide: From the City of Seattle's Emergency Management Guide

'Drunk Trees' and a Deluge of Rain Increase Landslide Risk

The Puget Sound area has been deluged with rain over the last few days, all within an already almost-record-breaking month of precipitation. With increased rain comes increased risk for landslides, and Aspect staff have responded to multiple ones over the last few days. This MyNorthwest article gives an explanation of landslide risks in our region with tips how to spot warning signs.

Aspect's Andrew Holmson Presenting at APWA's Fall Conference

Aspect’s Andrew Holmson will be presenting at the American Public Works Association’s (APWA) fall conference in Spokane on Thursday, October 6. He and City of Port Angeles Engineering Manager Kathryn Neal will present Protect and Innovate: Port Angeles Landfill Stabilization – the story of how the City and a large, multidisciplinary team relocated 400,000 cubic yards of refuse away from a 140-foot bluff overlooking the Strait of Juan de Fuca while building Washington’s tallest reinforced soil slope.

Aspect has provided geotechnical engineering, hydrogeology, and environmental support to the City’s closed landfill facility since 2007. We led the engineering geology team in determining long-term and short-term shoreline and bluff retreat rates, evaluating options for removal of existing shoreline protection structures, extending or modifying the structures, evaluating bluff slope failure mechanisms and slope stabilization options, landfill cell relocation, and fill slope stabilization and design. Work on the slope was completed ealier this year. Aspect continues to support the City with operation and maintenance of the landfill gas system and have provided environmental monitoring and support to meet regulatory reporting requirements.

Learn more about the APWA’s fall conference here and read more on Aspect’s efforts on the landfill here.