[Note that this article is a transcript of the video embedded above.]

I’m standing in front of a pair of water towers near my house in San Antonio. If you’ve seen my video on water towers, or you just know about how they work, they might look a little odd to you. It’s not only unusual that there are two tanks right next to each other, but that they’re completely different heights. This difference is a little hint that there’s something more interesting below the surface here. Some engineering achievements are visibly remarkable. It’s easy to celebrate the massive projects across the world: the Hoover Dams and the Golden Gate Bridges. But it’s just as easy to overlook the less notable infrastructure all around us that makes modern life possible. If you’ve seen any of my videos, you know that I think structures hidden in plain sight are just as worthy of celebration. In fact, I think infrastructure is so remarkable, I wrote a book about it that you can preorder starting today. I can’t tell you how excited I am to announce this project, but first let me tell you a little bit about these water towers and a few other things in San Antonio too. I’m Grady and this is Practical Engineering. In today’s episode, I misguidedly chose the coldest day of the year to film my first on location video here in my home city to talk about a few of my favorite parts of the constructed environment.

Luckily the drone footage was taken on a sunnier day. You may have guessed already that these two towers aren’t connected to the same water distribution system. If they were, water would just drain out of the upper tank and overflow the lower one. San Antonio actually has a second system that takes recycled water from sewage treatment plants and delivers it to golf courses, parks, and commercial and industrial customers throughout the city. Treated wastewater isn’t clean enough to drink, but it’s more than clean enough to water the grass or use in a wide variety of industrial processes. So, instead of discarding it, we treat it as an asset, delivering it to customers that can use it. That reduces the demand on the potable water supply (which is scarce in this part of Texas). Some people call this the purple pipe system, because recycled water pipes have a nice lavender shade to differentiate them and prevent cross connections. San Antonio actually has one of the largest recycled water delivery systems in the country, and this water tower is one of the many tanks they use to buffer the supply and demand of recycled water around town.

Not too far from the two towers is this unofficial historic landmark of San Antonio. It may just look like a simple concrete wall, but Olmos Dam is one of the most important flood control structures in the city. This structure was originally built in 1927 after a massive flood demolished much of downtown. A roadway along the top of the dam had electric lights and was a popular driving destination with nice views. The roadway has since been replaced by a more hydraulically-efficient curved crest. I have a special connection to this dam because I worked as an intern on a rehabilitation project at the engineering firm hired to design the repairs. The project involved the installation of about 70 post-tensioned anchors to stabilize the dam against extreme loads from flooding. Each anchor was drilled through the structure and grouted into the rock below. Then a massive hydraulic jack was used to tension the strands and lock each anchor off at the top to stitch the dam to its foundation like gigantic steel rubber bands. The contractor even had to use a special drill rig to fit under this highway bridge. San Antonio is in the heart of flash flood alley in Texas, named because of the steep, impermeable terrain and intense storms we get. Olmos Dam helped protect downtown from many serious floods in its hundred year lifetime. But, it’s not the only interesting flood control structure in town.

I’m here at the Flood Control Tunnel Inlet Park, one of the best-named parks in the City if you ask me. And below my feet is one of the most interesting infrastructure projects in all of San Antonio. These gates might not look too interesting at first glance, but during a flood, water in the San Antonio River flows into ports of this inlet structure instead of continuing downstream toward downtown. From this inlet, the floodwaters pass down a vertical shaft more than a hundred feet (or 35 meters) below the ground. The tunnel at the bottom of the shaft runs for about 3 miles (or 5 kilometers) below downtown to the south, allowing floodwaters to bypass the most vulnerable developed areas and saving hundreds of millions of dollars in property damages from flooding.

When in use, the floodwaters from the tunnel flow back up a vertical shaft and come out here at the Flood Control Tunnel Outlet on the Mission Reach of the San Antonio River. Under normal conditions, there are pumps that can recirculate river water through the tunnel, keeping things from getting stagnant and providing a fresh supply of water to flow through the downtown riverwalk. This part of the San Antonio River south of downtown is one of my favorite places because it’s a perfect example of how urban and natural areas can coexist.

When you consider infrastructure and construction, you might think about concrete, steel, and hard surfaces. But this part of the San Antonio River was included in one of the largest ecosystem restoration projects in the US. Before the project, this was your typical ugly, channelized, urban river, but now it’s been converted back to a much more natural state with native vegetation and its original meandering path. But, the project didn’t only improve the habitat along the river. It also included recreational improvements to make this stretch a destination for residents and tourists. For example, these grade control structures help keep the river from eroding downward, but they also feature canoe chutes so you can paddle the river without interruptions. There are several new parks along the river, including Confluence Park, home to this beautiful pavilion made of concrete petals. Most importantly, there is a continuous dedicated hike-and-bike trail along the entire stretch.

Everyone knows about the Alamo because of the famous battle, but there are actually 5 Spanish missions established in the early 1700s along the San Antonio River. The sites together are now a historic National Park and a UNESCO World Heritage site. You can tour the missions to learn about the history of Spanish colonialism and interwoven cultures of Spain and the Indigenous people of Texas and Mexico. The Mission Reach trail provides a connection to all the missions and a bunch of other interesting destinations along the river, including parks, public art, and my favorite spots: the historic and modern water control infrastructure projects.

So far all the structures I’ve shown you have been water-related. That’s my professional background, but we could do similar deep dives just here in San Antonio about the power grid, highways, bridges, telecommunications, and even construction projects. And, preferably on warmer days, we could do similar field guides in every urban area around the world. In fact, that’s the premise of my new book, Engineering in Plain Sight: An Illustrated Field Guide to the Constructed Environment. I’ve been working so hard on this project for the past two years, and I’m thrilled to finally tell you about it.

Just like there are written guides to birds, rocks, and plants, Engineering in Plain Sight is a field guide to infrastructure that provides colorful illustrations and accessible explanations of nearly every part of the constructed world around us. It’s essentially 50 new Practical Engineering episodes crammed between two covers. Imagine if you could look at the world through the eyes of the engineers who designed the infrastructure you might not even be noticing in your everyday life. I wrote this book with the goal of transforming your perspective of the built environment, and I think once you read it, you’ll never look at your city the same again. You can explore it like an encyclopedia - picking pages in no order. Or treat the sights of your city’s infrastructure like a treasure hunt and try to collect them all.

The book comes out in August, but I would love if you preorder your copy right now because, in the world of books, presales are the best way to get the attention of bookstores and libraries. If you preorder directly from the publisher, you’ll get a discount off the regular price, and you can preorder signed copies directly from my website that come with an exclusive enamel pin as a gift. Preordering is the only way to get your hands on this custom pin that was designed by the book’s illustrator.

Use the link in the description to find all the preorder locations. And one more thing: between now and when the book publishes, I’m going to be posting some short explainers about interesting infrastructure on all my social media channels, and I want to encourage you to do the same. I’ll be sending 5 signed copies of my new book to my favorite social media posts about infrastructure that use the hashtag #EngineeringInPlainSight. Check out the link below for more information. And from the bottom of my heart, thank you for watching and let me know what you think!