26 Jan How Do We Know – Part 3
Happy 2020 Everyone! Picking up where we left off with our validation series of posts…
We have discussed validation of our acoustic probes by measuring accessible points (manhole depths) and using existing techniques such as active probes. We also discussed a blind test where we surveyed an area where the client had known data and our data lined up with theirs. Now we want to talk about a combination of indirect methods.
At the north end of our shop area in southwestern Denver, there are several electrical boxes, water valve boxes and storm and sanity sewer lines that all have clear surface indications, but only some of them are useful for determining depths. This is our standard test area for evaluating new waveforms, probe geometries and equipment upgrades. The soil is bentonite-ridden with various layers of fill. We have done many collections in this area and have followed buried structures from their surface manifestations all around the area. The acoustically measured depths are very consistent between survey runs, across different kinds of equipment and match the depths we can access and are consistent with standard designs. Furthermore, we can see when two structures cross and can follow them independently. To be specific, the fire water lines that go to hydrants and riser rooms in the facility are all consistently 4-6 feet down and lie consistently above the deeper sanitary sewer that predates the infill for the currently building. Taken individually, this is a good warm-fuzzy. Taken as whole across the entire area, this becomes definitive. This is the best illustration we have short of pot-holing or excavating, which we discuss in the final installment in this series.