What signs suggest foundation scour or undermining?

• A. Visible cracks in pavement and potholes
• B. Ponding water on the deck surface
• C. Rust on exposed steel elements
• D. Uneven settlements, bearing movement or misalignment, exposed foundation material, or scour holes near piers.

Answer: (D)

Foundation scour happens when fast-moving water erodes the sediments around a bridge footing, weakening the support the structure relies on. The most telling signs are when the foundation itself shows evidence of movement and exposure. Uneven settlements or bearing movement indicate the footing is no longer supporting the superstructure evenly, which is a classic consequence of undermining. Exposed foundation material means erosion has traveled down to the footing or abutment, revealing the base that normally sits beneath protective cover. Scour holes near piers are a direct, observable sign that water is actively removing material around the pier foundations. Together, these indicators point to undermining of the foundation and potential loss of support.

Other issues like visible cracks in pavement and potholes reflect surface distress or deck problems, not the condition of the foundation itself. Ponding on the deck surface signals drainage or surface problems, not scour at the footing. Rust on exposed steel elements shows corrosion risk in metal components, which may accompany deterioration but does not by itself prove foundation scour.