Topographic Surveys in Antioch, CA

Antioch is one of Contra Costa County's oldest cities, and its terrain tells the story of each growth era in order: a historic downtown on the San Joaquin riverfront, broad postwar tracts across the flats, newer subdivisions climbing the hills to the south, and large-lot rural edges beyond them. Since the BART extension opened at the Antioch station, infill pressure on the older tracts has grown, and with it the demand for accurate site topography. Additions and ADUs on postwar lots need precise existing-grade mapping so drainage from new roof area and hardscape resolves legally on-site; on the flats, where lots were mass-graded decades ago and have settled and been re-landscaped since, the as-built surface rarely matches any record grading plan. Our Trimble terrestrial laser scanner captures the real surface — millions of survey-grade points in one visit — rather than an idealized sketch of it.

The hillside subdivisions of southern Antioch present a different problem set: engineered slopes between pads, drainage terraces and v-ditches, and retaining walls that any new pool, accessory structure, or slope repair must respect. The scanner records those engineered features continuously, so your civil or geotechnical engineer receives true slope geometry instead of interpolation between sparse shots. Along the Delta shoreline and marina, low-lying parcels fall within areas mapped for liquefaction under the Seismic Hazards Mapping Act, and waterfront work typically needs site elevations tied to a recognized vertical datum for flood and geotechnical review — control we establish as part of the survey. Deliverables across all of these settings include one-foot contours, spot elevations, a vegetation-filtered DTM, DWG/DXF base maps, and the point cloud itself.

Where a project involves dividing land — not uncommon on Antioch's large-lot southern edges — the Subdivision Map Act governs the process, and our topographic mapping feeds directly into tentative map preparation alongside our parcel map work. Records research runs through the Contra Costa County Recorder and County Surveyor offices in Martinez.