Bridges & Highways

Group Delta, an NV5 Company, provided geotechnical services for the PA/ED revalidation stage of the project. The project proposes to widen SR-91 by about 20 feet on the eastbound (south) side, which includes widening two bridges and making large cuts with soil nail walls into the steep southerly slopes containing the Mindeman Landslide Complex and other suspected landslides.

Our team summarized and analyzed extensive existing geotechnical data in the corridor, assisted RCTC in evaluating the project risk of landslides and obtaining Caltrans approval of the design approach for the soil nail walls, developed a preliminary workplan and environmental coordination for geotechnical investigation of the slopes, and performed preliminary slope stability and soil nail wall design calculations to evaluate cost and feasibility of the soil nail walls.

Our team prepared a Mindeman Landslide Risk Memorandum, Geotechnical Investigation Workplan, Preliminary Materials Report, Preliminary Geotechnical Design Report, two (2) Structure Preliminary Geotechnical Reports (SPGRs) for bridge widenings, and eight (8) SPGRs for soil nail and other cut retaining walls.

Added Value 

• Geotechnical Expertise: Our team delivered post-advanced planning studies and comprehensive geotechnical data reports for bridge structures, supporting foundational design decisions.
• Quality Oversight: Our team provided daily review of design-build contractor submittals, ensuring compliance and consistency throughout the project lifecycle.
• Materials Assurance: Our team conducted quality assurance materials testing and special inspections across multiple parcels within the expanded Caltrans right-of-way, reinforcing construction integrity.