California's Impossible Bridge Over Pine Valley Creek

What if I told you there was a small mountain town in Southern California that almost got carved in half by the interstate? Now, when old US-80 was being replaced by interstate aid, the answer was simple. Follow the old road and send the freeway straight through the village of Pine Valley. A move that would have changed the town forever. But then a California Highway Department engineer named Nello Erwin Greer looked at the map and saw another way. It was shorter, it could move traffic faster, and it could save millions by carving two miles off the corridor. There was just one problem. That better line ran straight into Pine Valley Creek Canyon. To make it work, the state would have to carry Interstate 8 more than 400 feet above the canyon floor on a hollow concrete box girder bridge built outward into open air without the traditional scaffolding most people would expect. Now, Greer's name would eventually go on the bridge, and for good reason. He helped push the project away from the easy line through the town and toward a route that spared Pine Valley. But by moving that line across the canyon, the story widened, forcing another group of engineers to solve the problem of getting it there. My name is Scott, and today we are looking at the Pine Valley Creek Bridge. It solved a problem that looked impossible, changed the route of interstate aid, and preserved a town in the process. Come along with us as we go Beyond the Exit. On March 11, 1959, the town of Pine Valley, California found itself staring down the barrel of a freeway. On that day, the California Highway Commission approved a 27-mile freeway corridor through the Laguna Mountain foothills between Greenfield Drive east of El Cajon and Laguna Junction. And when that line reached Pine Valley, it followed the road that was already there, Old U.S. Route 80. For decades, U.S. 80 had been the way through this part of the mountains. It was the old southern road out of San Diego, the connection east toward the Imperial Valley, Arizona, and, of course, the rest of the country. Also known by an older auto trail name organized in 1914 as the Dixie Overland Highway, which is a complete other story we're working on about this corridor. We're in the process of developing it due to your request. But in Pine Valley, it was more than a highway. It was the road the town had grown around. Roadside businesses and restaurants, homes, cabins, local traffic, not to mention travelers and visitors, all share that same narrow corridor. For generations of travelers, the town had been a quick high country excursion, less of a tourist playground and more of a rustic mountain refuge, breathing room from the cities over the weekend. But now that was all set to change. With Interstate 8, the state wasn't just updating a road. The plan was to have U.S. 80 meet modern interstate standards. In Pine Valley, that meant converting a local roadway into a divided high-speed freeway, requiring extensive grading, right-of-way, clearance, and a standard 100-foot median. The roadway would be nearly 200 feet wide. The state had studied this as well. Its own review detailed the casualties. Homes, businesses in the specifically the ones the town was named for, and even two Cleveland National Forest recreation areas. They all sat within the path of destruction. Ironically, the road that had connected Pine Valley to the outside world was now set to tear it apart. By the early 1960s, the state wasn't blind to this problem as well. It was getting harder to ignore. Now in response, the state began evaluating a workaround known in public notices as Alternate S or the Red Alternate. Instead of slicing through the town core, Alternate S went south of the area. When the state held a public routing hearing on May 4th, 1965, the argument was no longer just about saving Pine Valley. It appeared that Alternate S also functioned better as a freeway. The southern bypass was almost 1.8 miles shorter and reduced the steep grades and sharp curves of the mountain road. Though it would be a little more expensive to create, it would also save taxpayers almost 8.4 million dollars over 20 years in fuel and travel time. But as we mentioned before, this bypass introduced a massive engineering hurdle. South of town, the new line ran into Pine Valley Creek Canyon, forcing California to build a Now the engineer who had mostly driven this decision was named Nello Irwin Greer. By the time Pine Valley came across his desk, he wasn't a new engineer with a bold sketch and a wild idea. And while he was for progress with the highway system, he was not for destroying natural resources that couldn't be replaced. Not to mention permanently wiping a community from the map. He was the main champion of Alternate S and had driven that option in the face of some pretty stiff opposition. But in the end, he prevailed and so did the town. But the why and how of getting this bridge across the gorge would fall to a set of talented engineers that had to rely on some very unconventional thinking. From the California Highway Department's side was original design engineer Bert Bozzone. Now that first design package was almost shockingly lean for a bridge this ambitious. Roughly 15 drawings. It was enough to establish the concept, which was going to be a high concrete crossing over the Pine Valley Creek Canyon. It would be built to reach out from each side rather than building a literal forest of supports from the canyon floor. To tighten the concept into a workable reality required Dr. Manxiong Tang, a brilliant design engineer working for a joint venture between two firms, expanding the drawings to about 500. Now just looking at the canyon, Pine Valley Creek was roughly 450 feet across and about 440 feet at its deepest. Now a conventional scaffolding or falsework job would have meant building a temporary structure from the bottom of the gorge high enough to hold the bridge forms while the concrete was poured. Because of the height, that wasn't really feasible here. Also, there was no infrastructure or access way back to where they were building the bridge to start with. Bozzone's concept pointed toward a different kind of bridge anyway. In fact, the answer they reached for this area had routes far beyond Pine Valley. After World War II, Europe had bridges to replace and steel was expensive. The entire transportation networks had to be put back together. Engineers there pushed pre-stressed concrete way before it was done here in the states. Instead of depending on heavy steel trusses or massive temporary supports, they learned to make concrete do more work with less material by compressing it with steel tendons and shaping it into hollow box girders. They were able to create long spans outward from piers. The post-war bridge logic is what eventually reached this canyon. A hollow box girder could carry enough heavy traffic without becoming a solid mountain of concrete. The pre-stressing let the structure fight the tension that would normally crack a long concrete span. Now, we've covered this type of construction before in our video on the Overseas Highway in Florida and the Lake Pontchartrain Causeway. At the end, we'll be sure to leave you links to those videos and in the description as well. The other unique part of this design was they were going to build it out from each end in mid-air. It was a balanced cantilever construction and it meant that the bridge could grow from the piers section by section instead of being propped up from the bottom of the What had been developed out of Europe's need to rebuild destroyed crossings now offered California a way to get across Pine Valley Creek. Dr. Tang later said that at the time, no one in the United States had experience with cantilever construction on a project like this. So, the team had to design more than just a bridge. They had to design everything to build it as well. First of all, the forms and form travelers. Now, form travelers were movable steelwork platforms that clamped onto the bridge already built behind them. Once a section of concrete gained enough strength, the traveler advanced to the next position carrying the forms, steel ducts, workers, and equipment needed to pour the next pieces of the box girder out in the open air. And once the concrete was strong enough, it would start again. One of the more interesting inventions that Tang's team used was a movable steel truss. It was a temporary structure that worked almost like a crane and an access bridge combined. It let workers, trucks, material, and equipment move from pier to pier as the bridge was being built. Now, even the piers on this bridge were unusual. Now, each span is supported by four of them, all rising from the canyon floor, split at the top in a Y shape, almost like a wide concrete tuning fork holding up the box girder above it. Even that split shape had a design to it as it allowed the underslung trusses that acted like cranes to move along without interfering with the supports. That way, the job could advance from the structure itself instead of relying on huge lifts from the canyon floor. Construction began from opposite points of the canyon and met in the middle. When the two halves of the bridge met at the center, crews left a small gap and hydraulic jacks were used to fine-tune the fit and the forces in the bridge. Then, the gap was filled with the final concrete pour. That last pour turned the two remaining arms into one continuous span, acting like an unusual concrete keystone right in the middle. On November 24th in 1974, the bridge and the new freeway segment from the Hopitool Valley Road to Pine Valley were dedicated. Two days later, traffic was scheduled to begin using it. For the state, it was another step forward in completing the San Diego to Yuma freeway. For drivers, it meant a faster, smoother mountain crossing. But for Pine Valley and US-80, it meant that the old road and the town itself had not been literally gutted and forgotten. Now to be fair, looking at it from the top side, it probably doesn't seem all that impressive. But when you look at it from the sides and below, it's quite a shocking view. But that's part of the engineering of the structure. It was meant to bypass a town and a forest, not necessarily draw attention to itself. Over time, it became a landmark, not just for drivers, but for engineers. The Pine Valley Creek Bridge showed the cast-in-place segmental balanced cantilever construction, which is a mouthful, could work on a major American highway bridge. For highway and construction crews, it became an object lesson or a great field trip, a classroom in the wild. And it also gave highway routing engineers a new idea, one that would help them span more impossible gorges and canyons, and possibly help preserve something more important in the end. Later, the state of California named the bridge after the original head engineer. Today, it's known as the Nello Irwin Greer Memorial Bridge. Our viewer comments from the Interstate 8 video that we did recently let us know this is a pretty well-known landmark. In the meantime, this great piece of engineering will just keep doing what it's supposed to do, moving travelers, vacationers, and of course heavy freight along the 8. And yet, when it was constructed, it was the first of its kind in the United States, and also the tallest bridge along the entire interstate system. It wasn't superseded until 1988, when the Glade Creek Bridge on I-64 opened 700 feet above the water surface. But back in Pine Valley, that happens, all in a third mile compact stretch that only takes seconds to cross over. It's another great example of what we call history hiding in plain sight. Now, maybe you know a little bit about that history, or you've had some experiences with the bridge yourself. If so, we'd love to hear about them. Our comment section on the channel is one of my favorite places to visit, and obviously yours as well. Reading and answering them is one of my favorite parts of the channel. Well, we hope you enjoyed our video on the bridge that saved a town. If so, if you wouldn't mind reaching over right now and clicking like, or sharing it with a friend that might like it as well, it definitely is greatly appreciated. And if you're enjoying our Beyond the Exit stories, why don't you join the Great Big BTE Caravan? We'd love to have you ride along with us. Sometimes YouTube can be a big winding road, or it can be a bridge over a deep canyon. We're certainly glad you went Beyond the Exit with us to spend a little time. As always, we want to thank you for watching, and say, God bless.