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Terminology For All Sizes

When I was maybe six months into my first job as an engineer, I had a conversation with a project manager that got me thinking about engineering language. He said “We have a very emotional building. It’s got depressed slabs and upset beams.” Those two phrases mean, broadly, the same thing: some of the concrete floor slabs were lower than the beams supporting them. In context, perfectly clear, but to an outsider it would be gibberish. Familiar words were being used in a manner that seemingly makes no sense. Ever since then, I’ve looked for oddball terms in engineering (my favorite, by a wide margin, is riprap) and for combinations of ordinary words that can confuse people.

The HAER picture above shows the water intake for the electric generators at the Post Falls Dam in Post Falls, Idaho. It is, frankly, boring. But I want to point out the sloped structure in front of the intake house. Here’s a blurry close-up:

That’s a “trash screen.” Its a steel grill with one purpose: to prevent large pieces of flotsam from getting to the intake, where they could conceivably clog the pipes or, in the worst case scenario, shatter a turbine. I love that name. It sounds like a piece of a domestic appliance, like part of the disposal in your kitchen sink. Here’s a better picture of a very small trash screen, at the Slater Mill in Pawtucket, Rhode Island:

The mill, and its wooden water wheel, have not been operable for a very long time, and the raceway is mostly dry, but you can see the way a trash screen was retrofitted in front of the stone mill building and the arched entrance to the wheel pit.