Geotechnical Engineering/Special Inspection/Materials Testing
TriMet, in partnership with several agencies and municipalities, is currently constructing a 1,720-foot long four-pier five-span cable-stayed bridge over the Willamette River. The bridge will be supported by two main towers (each over 180 feet high), four landside abutments, and over 3.5 miles of cable. In addition to the light-rail line and bus route, the bridge will include two 14-foot wide bicycle and pedestrian paths. NTI’s parent company, Northwest Geotech, Inc., and Earth Mechanics, Inc. were selected to perform the geotechnical investigations and engineering for final design and construction as part of the winning D/B team. NGI scoped, estimated, and performed the final geotechnical explorations and the seismic and static laboratory testing program, and is the geotechnical engineer of record for the explorations and subsurface interpretation, bridge approach embankments, shaft foundation load testing program, various retaining walls, and verification of shaft foundation construction conditions. NGI interpreted all subsurface conditions and developed the foundation data sheet along with authoring the Geotechnical Data Report and the Supplemental Geotechnical Design Report. Geotechnical engineering responsibility included surcharging and preloading of the approach embankments to mitigate settlement, developing the highly successful O-Cell testing program for the 10-foot diameter shaft foundation elements, and construction monitoring of all geotechnical related elements of the project. NTI is currently providing materials testing and inspection in support of the contractor’s quality control program, including visual welding inspection of temporary and permanent bridge elements, ultrasonic weld evaluation of over one hundred pile splices, inspection and testing of thousands of cubic yards of reinforced concrete, in-place nuclear density testing of structural fills and asphaltic concrete, ultrasonic inspection of rail connections, inspection of proprietary anchors, and inspection and testing of the post-tensioned concrete bridge spans.