We Built a Bridge

Bridge building
Bridge building

I am a civil engineer. You all know this. I fell into civil engineering because I wasn’t smart enough to fly rocket ships. Moving stuff was too hard for me to calculate. Civil engineering keeps things stationary. I could get my head around those equations. Once in CE I realized I really liked learning about how things were built, where water ran, and how CEs did a lot of public works from roads and drinking water, to stadiums and landfills. It’s a wide ranging field of study. I worked my way through college on construction sites but I chose to spend my career in environmental remediation and enforcement. I wanted to clean up the world and it was heartfelt work but my love of building never went away. I even won the balsa wood bridge contest in my senior structures class. I had a partner but I made the design. A structural engineering friend said two things to help me: keep it simple and remember the moment of inertia. A light bulb went off and I realized a triangle with a skin (sort of like a covered bridge) was the way to go. Balsa wood bridge fail at their glued joints. We eliminated all but three joints. The bridge came in at less than 100 grams and it held an astonishing weight. The most in our entire class by at least 2. I can’t quite remember the details. None of the elaborately constructed truss bridges my classmate produced came close.

This week Burt and I built our first actual, rather than metaphysical, bridge. It’s lightweight, and ready to breakaway in a flood. It’s also darn scary. Our client is thrilled. She wanted it up above the flash floods that roar in from the fire damaged land above. Climate change has made the creek more prone to catastrophic flooding. Heavier rains and less vegetation to slow the runoff makes for higher peaks of flood waters in Cave Creek Canyon. I spent a lot of time researching the hows and materials for this and then I consulted with Burt. I couldn’t quite figure out how to attach the bridge to the trees n either side of the creek. Burt solved this critical problem. We wrapped the trees in a big circle of cable and tightened it up. I found away to attach the cinch without girdling the trees and it all came out great. See pictures. If you ever want to build a cable bridge check out YouTube. Lots of ideas there. I melded together a bunch of things to make something inexpensive and strong. The client bought the cable and the hardware. The wood was found onsite. Our labor was in trade for her providing accommodations to our staff during Portal Irish Music Week.

What a rewarding bit of work.

It's lightweight and strong.
It’s lightweight and strong.
Blocks of juniper log keep the cable from digging into the live tree.
Blocks of juniper log keep the cable from digging into the live tree.
It's scary, too
It’s scary, too
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2 thoughts on “We Built a Bridge”

  1. Must be sober when negotiating this. It reminds me of the floodgates we had growing up in flashflood prone canyon.

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