LOCATION: Benton County, Oregon
MARKET: Transportation
SUBMARKET: Pavement, Retaining Walls, Signs and Signals

DESCRIPTION: The purpose of the project is to improve the safety performance of US20 between the north Corvallis city limits and Springhill Road in Albany, with an emphasis on low‑cost, high-benefit improvements.

The project was initially broken up into five segments, Segment A through Segment E, which extended from North Albany Rd. to NE Conifer Blvd. in north Corvallis (US20 MP 9.70 to MP 2.92). However, the project was subsequently split up to accommodate available funding. Phase 1 consists of work in Segments B, C, and D from MP 4.73 to MP 7.01.

The main project elements focused on the US20 intersection with NE Granger Ave. and Independence Highway. The project elements include new pavement and roadway widening along the corridor, a sign structure, lighting at each intersection, and a 1,070‐foot long MSE retaining wall.

SERVICE:  Foundation Engineering, Inc. was retained to provide pavement analysis and design services, and geotechnical analysis and design services for the cantilevered sign, MSE retaining wall, and the new luminaires. Geotechnical exploration consisting of 17 geotechnical borings, eleven shallow core holes and ten test holes were required to collect the necessary soil samples and subsurface information for the project.


US20 between Corvallis and North Albany sees more than 18,000 vehicles per day!

An extensive laboratory testing program was completed to evaluate the settlement beneath the proposed 23‑foot high MSE retaining wall that would be constructed over soft ground. A retaining wall alternatives analysis was completed to evaluate and recommend the most feasible and flexible wall type and facing that could withstand up to 6 inches of total and differential settlement. An MSE wall constructed with wire mesh facing was ultimately selected. The wall was constructed with settlement hubs to monitor the settlement for up to 12 months to verify the results of the settlement analysis prior to paving. Additional analysis and design included a spread footing for the cantilever sign support, drilled shafts for the luminaire supports, and pavement analysis and design.

Project deliverables to the Agency included a Pavement Design Memorandum and a Pavement Design Summary addressing pavement overlay requirements and new construction for shoulder widening, a retaining wall report, a luminaire foundation report, and a cantilever foundation design report. All work was completed in accordance with the most recent versions of the ODOT Geotechnical Design Manual and the ODOT Pavement Design Guide. Foundation Engineering also prepared the required ODOT Special Provisions for various project elements. The project began construction in 2021.

Phase 2: This phase involves the widening of the west side of the highway, between NE Asbahr Avenue and Conifer Boulevard. The east side of the highway will follow from Conifer Blvd to Merloy Avenue. The work is expected to happen during the daytime hours. Construction is estimated to be completed in 2023.

Highlight: This project was logistically challenging due to the high traffic volume (16,000 ADT). However, Foundation Engineering’s highly qualified field personnel coordinated with the Agency and sub-contractors to complete the field work during the night when traffic volumes were lowest. Miles of ground penetrating radar (GPR) traces was required to identify the limits of the original 1924 roadway that consisted of 7-inch thick, Jointed Concrete Pavement (JCP) slabs. ODOT mandated the pavement slabs could not be disturbed by saw cuts or other operations that are required for roadway widening. This information was used by the design team to delineate the saw cut lines on the project plans.

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