City of San Leandro Ground Stabilization Design
Terraphase led the planning, design, and field implementation of a pilot-scale sludge-soil-cement stabilization project at the City of San Leandro, California, wastewater treatment plant. The project focused on stabilizing over 30,000 cubic yards of sludge stored in a former polishing pond to create a structurally sound surface for the future construction of a treatment wetland.
Scope of Services
Terraphase conducted bench-scale testing of multiple sludge-soil-cement mixes to identify viable stabilization formulations. Terraphase also designed and implemented a pilot-scale test, which included developing test mix designs and shallow soil mixing methodologies, prequalifying specialty contractors to implement the test, preparing bid documents, and providing construction oversight and quality assurance during implementation test implementation.
Data from the pilot test allowed the project to refine the cement mix design and construction quality assurance requirements, estimate full-scale production rates, evaluate and recommend methodology, and develop the full-scale implementation schedule.
Notable Accomplishments
- Designed and executed successful bench- and pilot-scale testing
- Developed refined mix designs and implementation methodologies based on pilot data
- Delivered construction drawings and technical specifications for full-scale implementation
- Supporting the city with bid document preparation for full-scale rollout
Bryant Manor Residential Development Geotechnical Support
First AME Housing Corporation is redeveloping a site located in central Seattle, Washington. The project involves the demolition of the existing buildings on site and the construction of two new multi-family residential structures. Terraphase provided geotechnical engineering support for Phases I and II of the construction, which consists of seven- and six-story residential buildings with associated basement parking levels, respectively.
Scope of Services
Terraphase provided geotechnical engineering evaluations for each phase of the project. Our recommendations were instrumental in the design of the building foundations, temporary shoring, stormwater management systems, and other site development. After submitting the initial geotechnical reports for each phase, we continued to support the design process by reviewing temporary soldier pile shoring systems, preparing required plan review letters, and assisting with the design of modular block retaining walls.
During construction, Terraphase remained actively involved by performing observation and testing services. This included monitoring the installation of soldier piles, evaluating subgrade conditions for bearing capacity, testing backfill around foundations, and delivering Certified Erosion & Sediment Control Lead (CESCL) services for both phases of the project.
Notable Accomplishments
- Provided geotechnical evaluations for foundation, shoring, and stormwater system design
- Supplied required geotechnical plan review letters
- Performed construction-phase monitoring and subgrade evaluation
- Conducted backfill testing and CESCL services across both project phases
Skagit County Road Repair
Following a major landslide triggered by heavy rainfall, Skagit County closed a section of Prevedal Road and established a temporary bypass in Washington state. Terraphase was retained on an emergency basis and mobilized to the site the morning after the initial phone call. The project required immediate geotechnical evaluation and stabilization design to restore access before the next wet season. The repair effort was jointly funded by the City of Lyman and Washington State Department of Transportation.
Scope of Services
Terraphase provided geotechnical consulting throughout the 30-, 90-, and 100-percent design phases to characterize the landslide and site conditions, identified factors that likely contributed to the slide, and presented potential stabilization and road repair solutions. Our team mapped the slide area and identified the root causes of the slope failure, which were the steep native slope, prior placement of uncontrolled fill to build the roadway, and poor existing surface drainage.
Notable Accomplishments
- Rapid emergency response with next-day on-site mobilization
- Full geotechnical support through all design phases
- Designed a reinforced soil wall solution tailored to site constraints
- Delivered a cost-effective, constructible design that enabled timely road restoration
