Bridge & Infrastructure Scanning in Mill Valley, CA

Mill Valley's structures divide neatly between a large one and many small ones. The large one is the Richardson Bay Bridge, the roughly 873-foot precast girder structure that carries US-101 across the bay margin east of town, built in the 1950s on steel piles driven through deep mud and widened in 1973. The small ones are the town's own crossings of Arroyo Corte Madera del Presidio, the creek that drains the southeastern slopes of Mount Tamalpais and runs beside Miller Avenue, along with the culverts, box structures, channel walls, and pedestrian bridges that carry streets and paths over the creek network below Mount Tam. Add the low ground at Tam Junction and Manzanita, which floods on king tides, and sea-level-rise planning becomes a standing item on almost every structure here.

What these projects need from a surveyor is elevation you can defend. We set and observe a control network on NGS and CSRC published stations, work in NAD83 State Plane and NAVD88, adjust by least squares, and check against monuments held out of the adjustment, then register every scan to that network. For a highway structure that yields clearance computed across the full lane width, plus deck, soffit, girder, bent, abutment, bearing, and joint geometry for rehabilitation or retrofit. For a creek crossing it yields inverts, soffits, headwalls, wingwalls, and channel cross sections that a hydraulic model can use without the engineer having to guess at the low chord.

Repeat epochs are the other half of the value. Registered to the same control, a later scan measures abutment movement, wall rotation, scour at a footing, or settlement of an approach as a difference surface rather than an impression. Town-owned bridges advancing through the federal Highway Bridge Program and Caltrans Local Assistance need that documented control behind them. Deliverables are E57 or RCP point clouds, DWG/DXF plans, sections, and clearance exhibits, and BIM-ready models. See infrastructure scanning, 3D scanning in Mill Valley, and deformation monitoring.