Evaluating what lies beneath the pavement
NGS performed pavement evaluation for selected street segments in Whittier. The assignment included 23 original exploration locations and 25 locations in the Janine Drive area, for a total of 48 coring locations throughout the city.
The purpose was to establish existing pavement sections, characterize the supporting subgrade and develop recommendations for new pavement sections and rehabilitation. The investigation focused on the roadway segments identified in the project exploration plans.
Field exploration and sampling
Field investigation included site reconnaissance, pavement coring and subsurface exploration to approximately five feet below the road surface. NGS documented existing asphalt concrete and aggregate-base thicknesses and obtained representative bulk samples of the subgrade soils.
A truck-mounted drill rig and hand-augering tools were used, with hand tools employed where potential utility conflicts were more probable. Exploration locations were backfilled and the surface openings were patched after sampling. The field information was recorded in exploration logs and location maps.
From subgrade testing to pavement alternatives
Selected subgrade samples underwent laboratory R-value testing to evaluate their support characteristics. NGS combined those results with measured pavement thicknesses and project traffic inputs to develop pavement recommendations using Caltrans design methodology.
The evaluation distinguished between sections with sufficient structural thickness for rehabilitation and sections requiring reconstruction. Where appropriate, rehabilitation considerations included localized repairs, milling and asphalt overlay. The Janine-area evaluation also accounted for the presence of macadam in the existing pavement materials.
Recommendations tied to individual roadway conditions
The deliverables brought together field logs, pavement-thickness information, subgrade test results and recommended structural pavement sections. These allowed the design team to compare the existing section with the requirements of each evaluated roadway segment.
NGS’s completed work provided the investigation findings and pavement recommendations for the design team. The investigation identified confirmation of actual exposed subgrade conditions during construction as a later step.
Engineering by Noorzay Geotechnical Services, Inc. Meet Maihan Noorzay, M.S., P.E., G.E.