Geotechnical Engineering Services

ENW provides an array of geotechnical engineering services throughout the Pacific Northwest. Our geotechnical field services include preliminary site reconnaissance and feasibility studies; geologic hazard studies, including landslide mapping, instrumenting, and monitoring; infiltration testing for stormwater management, and geotechnical field investigations for subsurface soil and groundwater characterization for site development. Once our field and laboratory data are collected, our geotechnical analyses include, but are not limited to, shallow, intermediate, and deep foundation designs; temporary and permanent shoring for deep excavations; piling sizing for boat docks; various types of retaining walls, including Mechanically Stabilized Earth (MSE) walls, soldier piles with tieback walls, and UltraBlock© walls; and slope stabilization systems, including rock anchors with reinforced wire mesh; shear piles; soldier pile walls with tiebacks and horizontal drains. During the design process, our senior geotechnical engineer works directly with the project design team to assist them in understanding the subsurface conditions and how the conditions will affect the proposed site development. During development activities, we provide special inspections to ensure that the site conditions encountered during our investigation are consistent with what is encountered during construction. If varying site conditions are encountered during construction, we then provide additional recommendations for developing the site. Our clients include individual property and homeowners, architects, developers for multi-family housing, industrial land owners, and local municipalities.

Our geotechnical engineering services include:

  • Preliminary site reconnaissance and feasibility studies

  • Geologic hazard studies

  • Geotechnical field investigations

  • Geotechnical analyses

  • Special inspections during development activities

 

PROMINENT PROJECTS

2006 Street of Dreams Landslide Stabilization, Hidden Lakes Estate, Oregon City, Oregon

In 2006, the Street of Dreams Home Show was in the Hidden Lakes Estates in Oregon City, Oregon. Shortly before Thanksgiving in 2006, a deep-seated landslide started to move on two of the properties. On the property with the most movement, the new house was torn apart, and the driveway sunk about 60 inches. On the second property, the slide was isolated in the side yard and did not affect the house, like on the first property, down into Abernathy Creek. Cynthia Hovind, PE GE, owner of Terra Dolce Consultants, worked with the owners of the second property to evaluate the landslide slide damage and to determine how to stabilize their property. Two slope inclinometers were installed to measure the depth and rate of the landslide movement. Based on the field data, Ms. Hovind designed the slope stabilization system that included 3-foot-diameter, 36-foot-long shear piles along the property line, two horizontal drains, and over excavation, replacement, and reinforcement of the landslide toe. Once stabilized, the area side yard was graded and planted with native plants. The work was completed in 2011.

Thurman Street Landslide Stabilization, Portland, Oregon

In March of 2017, a large landslide occurred on the downhill side of NW Thurman Street in Portland, Oregon. The site had a history of landslide that dated back to 1916. The 2017 landslide was 35 feet deep and damaged three properties, plus the northside of NW Thurman Street. Two of the three lots were developed in 1984 with houses, and one lot was vacant. The house on the west end of the slide suffered the most damage and was eventually torn down. Cynthia Hovind, PE GE, owner of Terra Dolce Consultants, Inc. worked with the three property owners to evaluate the landslide and to design a slope stabilization system. Based on the field data, Cynthia designed a soldier pile wall with tiebacks that ran the width of the three lots, downslope of the existing houses. The piles were drilled and set in concrete and then tiebacks were drilled up to 80 feet and grouted into the hillside. The landslide stabilization was completed in 2019.

12 Street Landslide Stabilization, Oregon City, Oregon

In December 2016, a large landslide occurred on the downhill side of three houses along 12 th Street in Oregon City, Oregon. The landslide occurred after heavy rains and was triggered by a stormwater infiltration trench located in middle of the slope. The slide was 15 feet deep and caused damage to the slope below the houses. Luckily, no damage to the three houses was observed. Cynthia Hovind, PE GE at Terra Dolce Consultants and Lynn Green at EVREN Northwest worked together with the property owners to evaluate the landslide and to design a slope stabilization system. Cynthia stabilized the landslide with shear piles, tiebacks, and horizontal drains. EVREN Northwest determined the environmental zone for the properties, which determined where the system would be installed and what additional native plantings would be required. The landslide was stabilized in November 2017.

Fuller Street Affordable Housing, Happy Valley, Oregon

Cynthia Hovind, PE GE, of Terra Dolce Consultants, Inc. provided geotechnical engineering services for the Fuller Street Affordable Housing Building in Portland, Oregon. The 4-story building is multi-family housing with commercial space at street level and three stories of apartments above. The building was finished in 2020.