• Conducting subsurface explorations (soil borings and/or test pits) with a minimum of three borings advanced to at least 15 ft below existing grade—or two feet into competent material, whichever is deeper—to characterize existing conditions. • Evaluating the drainage system adjacent to and underlying the abutment, including CCTV inspection, in-place hydraulic conductivity testing of the crushed-rock backfill, and assessment of its influence on subgrade stability. • Performing laboratory testing of soil and material samples to determine engineering properties and suitability. • Analyzing collected data to clearly identify the cause(s) and full extent of the subgrade failure, including consolidation, immediate elastic settlement, global slope stability, and long-term differential movement between the pavement, curb, and bridge abutment. • Providing feasible engineering recommendations for stabilization and mitigation measures to correct existing settlement issues and prevent future subgrade failure, including any necessary modifications to existing drainage infrastructure. • Offering construction methodology recommendations and specifications for recommended remediation measures.
