7.8.1 Final Geotechnical Surveys

Geotechnical investigations are necessary to design for satisfactory long-term performance of structure foundations. For some projects, geotechnical data may have been collected during preliminary engineering. All required data to finish designs must be obtained prior to beginning detailed bridge design.
To make a single data collection effort, coordinate obtaining geotechnical data for designing and planning of the following elements:
  • Bridges;
  • Radio towers;
  • Retaining walls;
  • Sound walls;
  • Illumination structures;
  • Overhead sign and signal structures;
  • Pavement structures;
  • Embankments;
  • Soil in proposed cut;
  • Trench excavation protection (shoring); and
  • Excavation and backfill for structures.
Considerations in obtaining final geotechnical surveys include:
  • Gather and review the existing geotechnical data obtained in preliminary engineering or existing geotechnical data from as-built plans;
  • Evaluate project for changes made after original geotechnical investigations were performed during preliminary engineering (e.g., added structures or changed structure limits); and
  • Identify additional data required to finalize design and prepare a boring layout to provide to the geotechnical firm obtaining data. Review the locations with roadway designers and structural designers to ensure placement of holes that can be accessed without special equipment if possible.