Editor's Points: Trust, But Verify
It wasn’t necessarily a theme of the MAPPS Winter Conference, but there were definitely a number of presentations that could have used the subhead, “Trust, but verify.”
George Southard of Trimble Navigation Limited offered one view of what happens if you simply trust. A CAD model of a highway bridge project using existing data looked pretty much like the bridge in question... until you looked closer and saw the road surface didn’t meet up with the bridge. A vehicle may have made the gap, but it certainly would have swallowed a pedestrian if the model was correct.
With a mix of technologies and the skills and knowledge of a professional surveyor, a different picture of reality emerged.
By the time Jim Anspach of Cardno took the podium to talk about “Effective Utility Investigations,” the stage was set, and “verify” was pretty nearly the watchword of the two days of presentations.
I sat there recalling my own small-scale scavenger hunt of a few years ago. My thought balloon at the time was, “Who moved my sewer line?” OK, it was a little bluer than that, but I found myself trying to locate a 6-inch cleanout that had mysteriously disappeared from the conventional location a foot or two from the public sidewalk. The city engineer couldn’t find it. My plumber couldn’t find it. Even my dog couldn’t find it.
The previous owners of my house had replaced the sewer line before putting the house on the market – I know because there was a huge swale running the length of the yard and I had to hire a landscaper to dress it up when spring arrived. It was a pretty good indication of where the line was, but that did nothing to help find the cleanout I needed to deal with tree roots blocking my sewer line.
Using the video the plumber took of the line, I was able to see a T where the cleanout had to be. I sat down with the video and some paper and started plotting out the distances and turns. In the basement, I measured off the distance to the first turn, placed a tape mark, measured to the outside wall, took a measurement from the north side of the house, and went outside to find that same spot. I staked it and attached a line. I stretched the line to the one point where we had some confidence and measured from the outside wall. I peeled back the sod from an unlikely spot, raised my pick to start digging for the missing cleanout. On the first swing, I heard a loud crack as I pierced the cover of the cleanout. I was 10 feet from the public sidewalk – over 8 feet in and 4 feet north of where it should have been. That effort saved me $18,000, the lowest bid to dig up the line in the absence of an accessible cleanout.
Score one for technology and a little effort. Anspach’s closing example was far more dramatic. He showed an example where a test hole was about to be drilled in a clear spot near a 6-inch water main. The problem was, that water main was a 6-inch gas line and it was right under the point indicated for the test hole. The consequences would have been catastrophic. So, as Anspach said, “Document reality, not a mistake.”