Project Overview
NTH was originally retained by The Corradino Group (who was the prime consultant to the Michigan Department of Transportation) to collect relevant geotechnical data and evaluate design and construction concepts for a cable-stayed bridge, suspension bridge, or tunnel to provide a new river crossing from Detroit, Michigan to Windsor, Ontario.
Our original services identified the historic use of solution mining within the proposed crossing alignment and as a result, we were engaged by the Michigan Department of Transportation to conduct a Brine Well Cavity Investigation to identify potential risks. This work included deep rock borings to depths as great as 1,750 feet followed by cross-hole geophysical testing in order to perform a computerized tomographic analysis of the bedrock stratigraphy and identify any anomalies that could potentially be voids associated with the earlier mining activities. Upon approval of the study plan for the new bridge, the Windsor Detroit Bridge Authority (WDBA) issued a request for qualifications for project teams for the new Gordie Howe International Bridge. The WDBA procurement was for teams to design, build, finance, operate and maintain the new bridge spanning the Detroit River. NTH was selected as a geotechnical subconsultant to AECOM, the prime designer for Bridging North America (BNA), for U.S. project elements including the Michigan Interchanges, U.S. Port of Entry and U.S. Approach Span project components.
Project Scope
Brine Well Investigation:
NTH was originally retained by The Corradino Group (who was the prime consultant to the Michigan Department of Transportation) to collect relevant geotechnical data and evaluate design and construction concepts for a cable-stayed bridge, suspension bridge, or tunnel to provide a new river crossing from Detroit, Michigan to Windsor, Ontario.
Cross-well seismic tomographic imaging was used to delineate the size, locations, and shape of potential brine well cavities in two proposed crossing corridors on the U.S. side of the river. The investigation plan included thirteen deep (1,750 feet) rock cores and borings, in combination with cross-well seismic imaging techniques that involved simultaneous and integrated data collection from multiple boreholes spread across the Delray neighborhood in Southwest Detroit. The cross-well seismic imaging was supplemented by an array of down-hole geophysical testing including sonic profiling, circumferential acoustic imaging (side-wall imaging of the boreholes), natural gamma surveys, compensated density, photo-electric logging, borehole gravity, and vertical seismic profiling.
Upon approval of the study plan for the new bridge, the Windsor Detroit Bridge Authority (WDBA) issued a request for qualifications for project teams and NTH was selected as a geotechnical subconsultant to AECOM, the prime designer for Bridging North America (BNA), for U.S. project elements including the Michigan Interchanges, U.S. Port of Entry, and U.S. Approach project components.
Foundation Investigations and Design:
Once the WDBA established the project requirements, NTH assisted the BNA team with evaluation and design of project elements during the pursuit phase. Our services included the evaluation of existing geotechnical data and development of design and construction recommendations associated with U.S. project elements. This included the evaluation of pile foundation resistances, ground improvement requirements, consolidation settlement impacts due to grade changes, time rates of settlement as well as mitigation measures that could be used to meet the project schedule, design of shallow foundations and impacts of embankment construction on the underlying soft clays.
BNA was selected as the preferred provider for the GHIB in July 2018. Immediately following BNA’s selection, NTH mobilized to initiate geotechnical investigations for the project segments. NTH has advanced over 665 test borings totaling more than 35,000 lineal feet. The test borings included piston/Shelby Tube sampling, in-situ vane shear testing, various cone penetration test (CPT), rock coring, and associated laboratory testing.
The subsurface conditions were processed and evaluated by NTH in support of the design of all project elements including bridge foundations and abutments, embankments, walls, signs, signals, ITS structures, roadways, buildings, utilities (including protection of existing structures), and ground improvements. More than 110 investigation, design, and geotechnical instrumentation reports were issued for the various elements.
Construction:
As Engineer of Record for geotechnical aspects, NTH is providing construction phase services to ensure that the project is constructed as designed and meets WDBA’s requirements and expectations. Services include construction observation; review and response to field clarification requests, material acceptance requests, etc.; review of geotechnical instrumentation reporting; ground improvement monitoring and assessment; as well as design changes during construction.
Client Benefit
NTH quickly mobilized up to 50 field and office staff as well as up to 6 drilling rigs operating concurrently to complete the project. NTH staff used state of the art geotechnical software to evaluate numerous technical issues such as slope and global stability, steel and precast concrete pile foundations, and settlement and surcharging requirements to meet very strict long-term performance requirements. NTH also marshaled the staff and support resources to meet the very aggressive schedules for submission of the various project elements and allow the design to remain on schedule.
