This cute dimple in the pavement is a sign of a future maintenance problem so be sure to keep an eye out and forit to worsen. Experience tells us that a cavity has formed under the pavement surface layer, likely because subsurface water is carrying fine soil and rock particles through seams or cracks in the adjacent storm or sanitary sewer structure. Over time, water will continue to run under the surface and will now accelerate the cavity size. If the problem isn’t addressed, daily traffic will cause a much larger problem, a deep pothole.
For a short-term fix, the “dimple” can be filled with a cold patch material. But, for the long term, the pavement around the structure must be sawcut and execavated; the structure and/or pipe replaced or patched as required; the aggregate replaced and compacted; and the asphalt concrete pavement patched and joints sealed.
Photograph from Zimmer Consultants