Monument Preservation in San Leandro, CA

San Leandro has a boundary-evidence problem most cities do not: the Hayward fault runs directly through it, and the fault creeps aseismically — the slow, continuous movement is famously visible in offset curbs and sidewalks along its trace. That means monuments near the trace are not fixed objects; they migrate with the ground, a fraction of an inch per year, decade after decade. For monument preservation this changes the calculus. A Corner Record is not just a formality before paving — it is a dated, measured record of where a monument was at a known time, which is precisely the evidence needed to interpret positions along a creeping fault years later. Business & Professions Code §8771 requires that referencing and a Corner Record filing with the Alameda County Surveyor happen before construction disturbs any monument, with a reset and second filing after. In San Leandro, complying with the statute also happens to build the time-stamped position history the fault makes necessary.

Away from the trace, the work looks like classic flatland preservation: postwar tract streets and industrial-to-residential conversion sites west of I-880 where paving programs and utility trenching cross original subdivision monuments, plus liquefaction-zone ground where monuments can be disturbed by more than excavators. We run the full sequence for agencies, districts, and contractors — records research, corridor search, pre-construction referencing and Alameda County filings, post-construction resets — and we flag which monuments sit close enough to the fault trace for creep to matter in the record.

Our Trimble terrestrial laser scanner is especially well suited to San Leandro’s situation: in the same mobilization that references the monuments, it captures the surrounding curbs, sidewalks, and pavement — including any visible creep offsets — at millimeter density. That point cloud pins each monument in its surface context at a known date, evidence that gets more valuable every year the fault keeps moving.