When you’re working on a highway design project, you receive information from multiple sources, throughout the life of the project. It’s important to verify the information you receive so that you are not subject to GIGO1. An example of this is the survey data that you get before you can start any of your design work. The survey crews will go out and locate where the roadway is, the edges of pavement, the location of each utility pole and fence and bush and drainage pipe. All the above-ground features will be found and located to (hopefully) a very tight tolerance. It is usual to take the survey data, put it on the plan sheets, and then walk the project to confirm that A) everything on the survey is located correctly and B) everything in the field is on the survey. Typical problems that arise and have to be corrected are drainage pipes that aren’t found or manholes that aren’t marked. That is one example of field verifying information.
Another is utility information. Utilities include water lines and gas lines and electrical power cables etc. These are fairly easy when they’re strung on overhead utility poles: while I might not know who’s lines are strung on the poles precisely2 I at least can see them, and I know where the poles are. I will know if I have to move one of those poles and that some Generic Utility Company will have to come out and restring their lines.
It gets more complicated with underground utilities. Sure, there are manholes that can be found that identify point-to-point where some things are, but generally we’re dependent on Utility Companies to tell us where the various water lines and gas lines and underground power lines are. There are methods3 for verifying the information received from the Utility Companies but it’s much more difficult.
However, there are times when it’s easy. For example, if a utility crosses a bridge, it has to do so by hanging from the deck or a beam. These are easily found and verified by walking under the bridge and looking up.
Just yesterday I discovered that some utilities that we’d been working on feverishly did not actually exist.
They may be somewhere, but they’re definitely not where we thought they were, i.e. they’re not hanging off the bridge we are working on. This makes life much easier, but it also means we did a lot of work for nothing.
So, once again, always verify your information in the field, to the extent possible. I hate learning lessons I already know.
- Computer Science term: Garbage In, Garbage Out [↩]
- could be power, or cable tv, or telephone, or fiber optic [↩]
- in Georgia this is called Subsurface Utility Engineering and has four different “levels” of quality. Qual D is just a records search. Qual C is a site survey as I’ve described above. Qual B is when an underground utility is located via a magnetic cable finder or other method and then the location of that pipe or cable is surveyed on the surface. This is what you see when you see yellow or red or blue paint on the ground marking utilities. Qual A, the best level, is when a hole is vacuumed in the ground and the actual cable, pipe or whatever is physically surveyed for exact X, Y, Z coordinates [↩]