Existing Subsurface Utilities in 3D

Joseph Romano, Principal, Surveying and Mapping, Langan Engineering

From a surveyor’s point of view, utility information is critical for many types of surveys that we prepare, from design level base mapping to as-builts, to boundaries to ALTA surveys, and much more. The need to provide accurate and complete subsurface utility information is vital to designers, landowners, and others. Getting that information onto plans requires surveyors to utilize different techniques including; field locations of surface features, field locations of test holes/exposed utilities, or tone-out markings and existing/built plans. Barring water and debris, subsurface storm and sanitary are often the easiest to map due to the accessibility of their piping structures. Mapping other types of subsurface utilities including water, gas, communications, and electrical, many surveyors rely specialized on utility location firms while some provide this service in-house.

In my 40-plus years of surveying and engineering experience, many users find subsurface utility mapping has always been a topic that seems to be surrounded by mystery. I am sure the readers are aware of the numerous means that can be deployed to help solve that mystery, but far too often the end users are not, and they only see the lines on the ground and then the lines and numbers on plans.

When attributed information such as invert, material type, and maintenance information are embedded into the 3D model, the clarity of the information is enhanced and the additional downstream uses are endless

Now, enter the world of 3D site modeling for design and existing conditions. Our firm has been utilizing existing condition BIM (building information modeling) in the above-ground architectural market since 1999 for some time. Recently Langan and other firms have leveraged that technology and its workflows to begin using 3D modeling to delicit existing and proposed site conditions for our surveys and design plans. This provides an ability to visualize both existing and design subsurface utility (as well as other) information, allowing our clients, the general public, reviewing agencies, and other nonprofessional users to visualize subsurface utility (and other) information in 3D. When attributed information such as invert, material type, and maintenance information are embedded into the 3D model, the clarity of the information is enhanced and the additional downstream uses are endless.

These are some issues that you will always need to contend with, from unknown depths to concerns with horizontal inaccuracies, to name a few. We also have to work with the various options and means of deliverables. However, as shown in the examples below the ability to provide this information in 3D is a game changer and is the path of future workflows.