Land surveyors
A topographic survey maps the shape of the ground and what sits on it: spot elevations, contours, finished floors, curbs, walls, trees and visible utilities. On the flat coastal plain that covers most of Long Beach, Lakewood and Bellflower, the elevations that matter are small, and a drainage design depends on getting them right. On Signal Hill and the San Pedro slopes the problem flips to steep grades and retaining walls. Elevations are tied to NAVD88 through published benchmarks - which matters near the harbor, where historic oil-field subsidence means old elevation figures may not match today's ground.
Most of Long Beach, Lakewood and Bellflower sits on a nearly level coastal plain, and that makes a topographic survey more useful, not less. When a lot drops only a few inches from the back fence to the sidewalk, whether rainwater reaches the street depends on differences too small to eyeball. The survey records spot elevations across the site, finished floor heights, curb and gutter flow lines, and neighboring grades at the property line, so a grading or drainage design works with the ground that is actually there.
Signal Hill and the Palos Verdes side of San Pedro are the exceptions - steep lots, stacked retaining walls and slopes where the design depends on every break in grade. Signal Hill is also where the Long Beach oil field was discovered in 1921, and abandoned wells still sit under yards and parking lots across the area. The state's Geologic Energy Management Division (CalGEM) runs a construction site well review, and local building departments can ask where any well sits relative to a proposed building. A topographic survey can pick up visible wellheads, vents and markers; wells with nothing showing at the surface are a question for the well records.
Elevations are tied to a published vertical datum, normally NAVD88, through benchmarks maintained by LA County Public Works. Around the harbor there is a specific reason for care: oil production from the Wilmington field caused the ground to subside - by roughly 29 feet at the deepest point by the late 1950s - until water injection stopped it. Elevations on old plans and old benchmark lists in that area may not describe today's ground, so current published values matter more than numbers carried over from a previous drawing.
A topo is the base sheet for grading plans, drainage fixes and new pads, including warehouse sites in Carson. It supports an ADU site plan, gives construction staking its grade control, and on low-lying waterfront parcels it is often paired with an elevation certificate.
How long does it take? Field time depends on lot size, slope and how much the designer needs located. A typical residential lot is one field visit; larger or hillside sites take longer.
These are usually asked for on the same transaction:
Lot lines, existing buildings, setbacks, easements, utilities and grades - the measured base an ADU site plan is drawn on.
Learn More →Offset, grade and utility stakes set from boundary control and benchmarks, so the building lands where the plans put it.
Learn More →The FEMA form that records how your building sits against the base flood elevation - used for flood insurance and map amendment requests.
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