Monument Preservation in Rodeo, CA

Rodeo's downtown was laid out as a grid in the 1890s near the San Pablo Bay shoreline, and the monuments that controlled that original grid are the foundation for nearly every lot line in the older part of town. Many of them lie beneath generations of pavement — set at street intersections and block corners, overlaid again and again since. When a paving contractor grinds and repaves a county-maintained street in old Rodeo, or a utility crew trenches through an intersection, there is a real chance the work will strike one of these century-old monuments. Because Rodeo is unincorporated, this work runs through Contra Costa County, and the records that protect its monuments — Corner Records filed before and after disturbance — go to the County Surveyor's office in Martinez.

Business and Professions Code §8771 requires that monuments be referenced by a licensed land surveyor before construction that will disturb them, and reset afterward. Our approach in Rodeo starts with record research: we pull the old maps and prior Corner Records to know where grid monuments should exist, then search for them in the field, including monuments buried under existing asphalt that a contractor would never see until the grinder hits them. We set reference ties outside the work zone, file the pre-construction Corner Records in Martinez, and return after the overlay or trench work to reset each monument and file the closing record. Our Trimble terrestrial laser scanner is particularly useful on these compact downtown blocks: one setup captures the full intersection — monument, curb returns, cottage-era improvements — at survey grade, preserving the context around the monument, not just the point itself.

An 1890s grid monument that gets destroyed without references is not easily replaced. The original field notes are sparse, the block was measured with chain-and-transit methods, and modern retracement of the whole grid segment can cost many times what preservation would have. For contractors and the county alike, referencing first is the inexpensive path.