THe trinity subsurface blog

Red, yellow, blue, orange, green: what each utility flag and paint color marks under the APWA Uniform Color Code, and how much clearance to give them.

811 does not mark every utility. Common myths about utility locating, including what public one-call services cover and what they leave in the ground.

Before you saw cut or core, you need to know what is in the slab. What GPR concrete scanning finds: rebar, post-tension cable, conduit and voids.

Decades of construction stack utilities on top of one another, active beside abandoned. How congested and overlapping infrastructure is sorted out.

Pipe runs from 3 inches to several feet, and camera choice follows diameter. How push cameras and crawlers differ, and what each size of line needs.

Surface features, line scans, grid scans and sweeps. The scanning patterns a locator uses to cover a site, and what each technique is good at finding.

Locating, vacuum excavation, pipe inspection and mapping are one workflow, not four. How each Trinity service feeds and verifies the next on a site.

Grease, roots, scale and debris all narrow a sewer until it backs up. What causes buildup in storm and sanitary lines, and how jetting clears it.

Utility knowledge from a past project is Quality Level D data at best. Why existing information goes stale, and when to re-verify what is underground.