Geologic Hazard Investigations

ENW performs a wide range of geotechnical analyses including settlement, slope stability, and seepage. We have a large selection of computer software and maintain access to several on-line databases, enabling ENW to efficiently analyze alternatives to optimize designs and provide our clients with cost-effective geotechnical analysis. 

Slope Stability:  The stability of natural and man-made slopes is dependent on a number of factors, including site geology, slope inclination, strength of soils, construction activities, and ground shaking. ENW utilizes state-of-the-art computer programs to perform slope stability analyses for both planned and existing slopes, as well as to provide repair recommendations for slope failures. Typically, these analyses are conducted based on laboratory tests performed on samples obtained from exploratory excavations, such as borings or test pits.

Geologic hazard evaluations are incorporated into geologic studies and may also be performed as a site-specific objective. Geologic hazard evaluations range from preliminary assessments to detailed analysis of hazards and design of mitigation measures.

Geologic hazard evaluations address:

  • Faulting and seismic hazards, including ground shaking, ground rupture and liquefaction potential

  • Landslide, mudflow and rockfall potential

  • Groundwater conditions and potential for flooding

  • Erosion potential

  • Compressible peat and organic soil deposits

  • Expansive soils

  • Geologic hazard assessments for school, hospital or other critical facilities projects



Bonneville Dam Navigation Lock, Oregon

Construction of a new lock required the stabilization of 3 landslide masses, relocation of a railroad mainline, and construction of an extensive diaphragm wall system to permit construction of the lock below the river level. The project, which incorporated all of the above-described activities, was a $40 million dollar federal project. Neil Woller was the Principal Technical Reviewer for the project.  He wrote the Foundation Report, which documented design assumptions, public bid process, subsurface investigation, and construction as-builts.

Pumped Storage Hydroelectric Project, Southern Oregon

The proposed pumped storage hydroelectric project involved pumping water to a dammed basin at an upper elevation on a mountain, followed by release of the water during periods of high electrical demand. Released water would be re-collected at a dammed impoundment at a lower elevation in the adjacent basin. Neil Woller evaluated soil and geologic conditions in the proposed impoundment areas on the mountain and in the basin below. He also evaluated the geology of the mountain between the two impoundments that would be tunneled to permit hydroelectric power generation.

Landslide Mitigation, Oregon

Lynn Green, working with Portland State University, was the principal surveyor for this project, which included both a topographic and subsurface survey. He wrote the Landslide Mitigation Report, which documented the anatomy of the landslide. The report included the results of the subsurface investigation and landslide mechanics.