Observations/Finding

FIELD OBSERVATIONS

On the above date, an AS Engineering and Consulting, LLC (ASEC) representative visited the site at the contractor’s request to observe excavation and mud mat subgrade preparation along the sheet pile wall located east of Pumpkin Vine Creek and along River Walk Manor Drive, in accordance with the project drawings, specifications, and prior coordination with the design team.

Excavation was performed along the face of the installed sheet piles to expose the underlying material for mud mat placement and interface with previously placed mud mat sections. Based on prior coordination with the bridge designer, the mud mat is intended to bear directly on competent, clean bedrock. This requires removal of all overlying soil and debris and preparation of a clean rock surface, including cleaning of the sides of previously placed mud mat sections to ensure proper contact.

TESTING AND RESULTS

A total of nine (9) excavation sections were observed along the sheet pile alignment. Bedrock was encountered at varying elevations within each section.

In several locations, bedrock was encountered at or above the proposed bottom of footing or mud mat elevation, consistent with prior observations. These conditions indicate that the required 5-foot mud mat thickness may not be achievable in these areas without modification.

The exposed bedrock surface and previously placed mud mat were observed for cleanliness and preparation. The contractor utilized hand tools (shovels and brooms) to remove loose soil and debris and promote direct contact between the mud mat and the rock surface. The prepared surfaces appeared acceptable for concrete placement at the time of observation.

The bedrock was observed to be generally competent based on visual assessment. While vertical continuity of the rock surface could not be verified within the exposed sections, prior subsurface exploration in this area indicates the presence of competent residual bedrock at the observed elevations.

Photographs documenting the excavation conditions and rock profile are included with this report.