Bert Bezzone at the Pine Valley Creek Bridge. We have not met before, but I’ve heard plenty about Bezzone from other bridge engineers and acquaintances who admit they stop to look at bridges.
Bridges tell me their life stories. They groan and bitch like aging weightlifters with bad backs and sore knees, then press thousands of tons into the air anyway. Earthquakes make them nervous, tense. Authors write bad books about them. Transients camp underneath, blackening their concrete bellies. Rivers bite some bridges’ ankles, and rust creeps into their joints.
Bert Bezzone hoists himself into the interior of the Pine Valley Creek Bridge. Pine Valley is famous among bridge engineers as the first prestressed concrete bridge in the U.S. built using cantilever technology.
Just when I think they’re the crankiest, goddamnedest things — and vow it’s the last time I’ll stop to look at their ugly beat-up bodies again—a beauty comes along and I fall in love.
I drive the roads of San Diego County with an agenda: You don’t know when you might spot another canyon dancer, a concrete Nureyev. I hike gorges and find them in places called Goat Canyon and Pine Valley Creek, their sweet lines out of sight from all but the worshipful. We bridge-lovers are lascivious Victorians, craving a glimpse of a well-turned, well-engineered ankle of concrete or steel. Don’t show us too much. We like mystery. We want to wonder how it was built, how it balances the forces of compression and tension deep inside its bones.
Bridges groan and bitch like aging weightlifters with bad backs and sore knees.
As a child, I interpreted the nursery rhyme “London Bridge is falling down, my fair lady” literally. Forget that little game in the school yard, I thought, what does London Bridge look like, and why is it falling down? Did someone build it wrong? Is the lady going to get hurt? Later I would find out that the original London Bridge, completed in 1209, took 33 years to build and killed more than 200 construction workers. Most drowned in the fast-flowing Thames.
Interstate 8 and 805 interchange in Mission Valley, looking northward
A little too prone to adventure in my teens, I created my own version of the bridge scene in the film Stand By Me. Those boys — caught mid-trestle — ran for their lives in front of an angry train. I was out there with friends on purpose. In Stockton, California, where I attended college, the delta is as complex as capillaries. Train bridges crisscrossed water north of town, saying, “Walk on me if you dare. Feel how light you are. I carry much more than you.” On Calaveras Slough one night in the early ’70s, friends and I wedged ourselves into the small railing bump-outs located mid-span in the event that workers were caught on the tracks. A long freight train passed within an arm’s length at 60 miles per hour. Soggy, diesel-smelling winds tore at our clothes. Creosote-soaked timbers screamed with what sounded like pleasure and pain. It was unimaginable ferocity, and we craved it.
Cabrillo Bridge spans State Highway 163 like a Roman viaduct.
We didn’t think of dying. That would steal the pleasure of reaching the other side. Bridges are to cross, the strongest everyday allegory most of us know for vaulting something impassable, flying above it, linking a place with another. We also pass under bridges, and in California some of that enjoyment has been stolen forever. Moving slowly in stop-and-go traffic on Interstate 405 near Santa Monica after the Northridge earthquake, I was about to cross under a massive slab supporting a six-lane surface street. The urge to stop and wait in my lane until traffic cleared ahead of me was overpowering. I ignored the questioning horn of the driver behind me, then drove quickly through the bridge’s shadow.
A small clone of Cabrillo Bridge exists in La Jolla on Al Bahr Drive, not far up the hill from Torrey Pines Road, via Exchange Place and Soledad Avenue.
Each year the more obscure bridges of San Diego County pass their completion anniversaries with no fanfare, no bleary-eyed looks from returning sailors on a carrier’s flight deck, no motorcade. Unlike “Big Blue” now celebrating its 25th, these bridges do silent duty, anonymous in an over-55 mile per hour world (except for Lilac Road’s graceful span over Interstate 15 near Fallbrook and Old Miramar Road’s similar jump over Interstate 805). Most of them are highway bridges, as flashy as blocking linemen guarding against the pass rush, unnoticed until they fail. But to a bridge engineer, they are all different, even lovable if you were the one who designed some of them.
Another grande dame of concrete bridges, the San Luis Rey River bridge on State Highway 76 near Bonsall, now carries bicyclists and walkers.
Bert Bezzone stands on the shadowed sidewalk outside Lindbergh Field’s East Terminal, briefcase in hand, wearing casual blue pants and a blue windbreaker. He is thin but not gaunt, in his mid-60s, and carries himself like most tall men, head bent forward as if in deference to someone shorter. His eyes sweep traffic and meet mine through the windshield. Dodging a few idling cars, he slides into the passenger seat.
We slide down a bank, duck under a huge concrete wall stretching into space, and crawl to a place where the ground is a few feet below the bridge.
We have not met before, but I’ve heard plenty about Bezzone from other bridge engineers and acquaintances who admit they stop to look at bridges, even if they live in an area that doesn’t have a single nostalgic chestnut like the classic covered bridges of Oregon. Retired this year from California’s Department of Transportation, Bezzone lives in Sacramento. He headed a bridge design section at a time when the state built a bridge a day. One of them — Pine Valley Creek Bridge on Interstate 8 near Descanso— was his favorite. His name is on the plans.
A small concrete bridge on Los Terrinitos, barely wide enough for two trucks, languishes near the much longer steel-girder bridge to the north on Wildwood Glen Lane.
Pine Valley is famous among bridge engineers. The first prestressed concrete bridge in the U.S., built using a particular kind of cantilever technology, it appeared to defy gravity during construction. Located near two earthquake faults, it also is the first bridge in the world designed with the aid of a modern mainframe computer simulating the effects of a major quake.
Columns rise above the creek bed (September '73). “When we first started looking at this site, we considered four configurations."
I stopped there once, long before I knew of any notoriety, while towing a trailer full of canoes to the Colorado River. The high winds that often close this stretch of interstate were wagging the trailer’s tongue, threatening to pull my ball hitch like a rotten tooth. I waited a few minutes on the west end and checked all tie-down ropes. What the hell, I thought, and edged across the bridge at 25 miles per hour, hoping not to watch ten canoes spill over a railing like airborne aluminum salmon. The canoes held. I knew then that the bridge was high — you could look up and down the canyon to figure that out — but from the road it looked plain, conventional, two generic Caltrans spans separated by a slot of open space.
Tower cranes ready columns for spans (December '73). “Everyone said the shape wasn’t going to fly.”
For a while, still on the drawing board in 1970 and ’71, it was a standard design. Long and high, yes — but complex enough to make a computer labor all night on its equations? Wild enough in its construction to have every bridge engineer in the country watching its progress?
Hundred of threaded steel rods pre-stress the bridge (February '74).
As we drive east on Interstate 8, in preparation for our stroll inside one of Pine Valley’s box beams, Bezzone is talkative: technical but clear, understandable. I’d envisioned him as the kind of fellow who has a garage full of tools, tinkers with anything mechanical whether it’s broken or not. Probably played with rockets and explosives when he was a kid. There’s an old saying about engineers: Ask them the time and they’ll tell you how to build a watch.
Spans are constructed from column to column (February '74). “If it wasn’t for a base of solid granite, we’d have had to dig up half the canyon to get a footing in there.”
He confirms all this. Even says he set the neighbor’s yard on fire with a model rocket that “didn’t go quite as far as I hoped.” He became a bridge engineer because “the more I looked around the Department of Transportation, it was the most challenging field. You build each bridge with similar components, but none of them are the same. They’re very personal things. When you get through, they stand out, not like 500 miles of pavement. A bridge is your child.”
Prestressed cantilever construction: concrete is poured on both ends span atop a column (1974).
Bezzone warms up to his old haunts. He drove this stretch of interstate east of El Cajon every few weeks as the highway pushed through East County mountains in the ’60s and early ’70s. As chief of the Office of Structure Construction, his responsibilities included all bridge construction in California, plus buildings such as rest stops, pumping stations, CHP facilities, and walls — in engineer parlance, “earth-retaining systems.”
“Our bread and butter, though, was bridges,” he says. “And up until 1972 we never worried about money. We were grinding stuff out. I had about 500 people spread around California, and we were doing about half a billion dollars’ worth of work a year.”
Spruce Street bridge. It’s not the Golden Gate, but the principle is the same.
Bezzone refers to his former department as “the bridge people.” It functioned as a central design and engineering service organization to individual Caltrans districts. Bezzone’s engineers put together packages of plans and specifications detailing a job and solicited competitive bids. Caltrans District 11 headquartered in San Diego was one of his favorites to work with because “they gave us a lot of latitude and were interested in getting good stuff.” Some highway bridges in San Diego are steel, especially in areas where it was important not to disrupt traffic (steel girders could be quickly dropped into place at night). Most are concrete.
Scripps Institution pedestrian bridge, a favorite destination of bridge lovers (and other lovers) who enjoy the effect of walking off a 135-feet-long diving board into a setting sun.
“Concrete allows you to use almost any imaginable form or shape,” says Bezzone. “It’s moldable. Second, it tends to behave as the designer envisioned it...concrete is a plastic material. It creeps. It deforms under its own load, redistributing the force within the system, whether it’s a building or a bridge, to the areas that you’ve reinforced. It’s a designer’s friend.
“Cost also mandated concrete structures in California. We cannot put up a steel bridge that isn’t going to cost 15 to 20 percent more than a concrete structure. The basic materials for steel require a lot more processing than ingredients for concrete. As long as we have aggregate supplies that are plentiful and usable, it will remain that way. Concrete also requires less skilled labor, and you don’t have to worry about getting it to the site. Trucking enormous pieces of steel around the state is very difficult. It forces you to cut your girders into smaller sections, then join them at the work site.
“[Steel’s] long-term maintenance is always a consideration. In most environments you have to protect it with some kind of coating, and in the coating business you have environmental problems. The material sandblasted off a steel bridge costs about $600 a cubic yard to dispose of. Older paints are toxic. We’re now putting on water-based paints, but you still have to collect that dust, get it confined, and take it away. Water-borne systems [paints] don’t have the life cycle of environmentally hazardous materials. They break down in a matter of a year or two. Along the coast it’s hard to hold paint on.
“So concrete prevailed.”
San Diego has many sources of aggregate (gravel), but, Bezzone recalls, “The better aggregates came from the other side of the hill clear on out into the El Centro area. Sands here are generally poor and tend to break down. You have some problems getting concrete out of them. Companies often hauled material in and blended it with local aggregates.
“A bridge builder has to be cognizant of aggregates’ properties. First, obviously, you’re worried about strength. But they also have durability characteristics. Talk about bridges that have been here since the turn of the century — you need durability. Another important factor is this business of creep, the ability to deflect or not to deflect. I said it was a friendly property, but it can also work against you. Concrete tends to slowly deform. We want to minimize that. It happens vertically and longitudinally in bridges that are post-tension. It will cause you some problems. Creep goes on infinitely; however, when you look at the deflection relative to time, 90 percent of it is out in the first ten years. It’s very time dependent...we really worry about it over the first five years.”
We drive under the Willows Road overcrossing in Alpine. It appears to be ruler-straight. Bezzone’s index finger scribes a horizontal line near the windshield.
“Take this span. That thing had three to four inches of deflection built into it on purpose. Initially it had a pretty good arch, but it settled down to the grade we want. We have classic examples where our estimate of deflection — we took in all the considerations—didn’t turn out at all. You can see that northbound on I-15 in a couple of bridges before you turn off into Poway. The girders are still cambered up a huge amount. God, we all thought we were going to be crucified by the newspapers when we got that thing up! It was so obvious that those girders were not where they were supposed to be. The San Diego Union came out with an article commending Caltrans for their attempt to put the historic mission arch into the bridge, and we all just gave a huge sigh of relief.
“That concrete was out of control.”
Look at the guardrails on a lot of bridges in San Diego County. You’ll see ups and downs. The short spans are not big problems. It’s when you get spans over a hundred feet that, Bezzone says, “you have to start worrying.”
Keeping concrete in control dates back to the early 1900s on a number of landmark San Diego County bridges. Several are massive icons of an age before prestressed concrete made bridges look lighter, more graceful. Many others were lost, unceremoniously torn down after their replacements opened.
Walking across Cabrillo Bridge toward an Emerald City of Exposition-era buildings is one of San Diego’s peak bridge experiences.
Built in 1914 for the Panama-California Exposition, Cabrillo Bridge spans State Highway 163 like a Roman viaduct. Construction of this bridge was not that different from today’s methods. Workers built forms, put in reinforcing bars and rods (“rebar” in today’s construction parlance), and poured concrete to the brim. It was decades before going to El Centro for better aggregate was an option. Concrete’s consolidation was also a big factor. Today, high-intensity-vibration probes are plunged into fresh concrete to help it settle firm, airless. On Cabrillo Bridge, workers used shovels and forks, packing and punching the soupy mixture as best they could. Because of all these factors, older concrete is more porous, allowing moisture in. Corroding rebar can pop off its concrete cloak because of the tremendous expansive force of rust. Similar problems developed on the Cabrillo Bridge’s deck by the late 1980s, but a rehabilitation program rebuilt the roadway.
A small clone of Cabrillo Bridge exists in La Jolla on Al Bahr Drive, not far up the hill from Torrey Pines Road, via Exchange Place and Soledad Avenue. With a Disneyesque flair, the roadway loops around and crosses over itself. Local legend among neighborhood children in the 1960s had trolls living in the dark recesses high up in one end.
Another grande dame of concrete bridges, the San Luis Rey River bridge on State Highway 76 near Bonsall, now carries bicyclists and walkers. High-speed traffic uses a new bridge’s swooping, banked curve a few hundred yards east. The old bridge’s graceful concrete arches held a heavy traffic load for decades. Concrete railings and other braces are also arch-shaped. The effect is a confection of arches, a mirror of Mission San Luis Rey’s architecture.
I stop to walk the old bridge and notice what must be the county’s most curious graffiti medium. A rust-colored lichen thrives on rough concrete, and passersby have covered rails with initials and messages scratched into the encrustation.
Elsewhere in the county, at least two other older bridges still stand beside their replacements. And there’s the oddity of a bridge built atop another.
One side-by-side pair spans the headwaters of Sweetwater River beside Japatul Valley Road (79). A small concrete bridge on Los Terrinitos, barely wide enough for two trucks, languishes near the much longer steel-girder bridge that replaced it a few hundred yards to the north on Wildwood Glen Lane. Both spans, once busy with Old Highway 80 traffic, are little used today. A triple-hinge arch supports the older concrete crossing, and aficionados like Fred Bast, a civil engineer working at the county’s Public Works Materials Laboratory, love this little bridge. At one time Bast traveled the county assisting another bridge inspector on county roads.
“In the first half of the century, it was very hard to calculate forces in bridge members,” says Bast, as he slides down the steep trail and sidles past some poison oak to a point where one of the bridge’s concrete legs angles into an abutment, “especially if you had to design for fixed connections. So they put hinges in to create a ‘zero moment’ at the ends of each leg and where they meet at the top. They were concerned about weight here. Seismic forces weren’t taken into account on most of these old bridges.”
Not knowing what to expect, I look for standard hinges, the type you might see on a door or cabinet. Bast points out that these hinges are the rocker-shaped ends of concrete arches resting against slanted concrete abutment walls. In the event of an overweight truck (a real possibility in the days when this was the only major route between El Centro and San Diego) or a truck slamming on its brakes, the concrete legs of this bridge rotate in place to relieve strain. To picture the forces, place your elbows on a table, make two fists, and put fists together under your chin. If you push down hard with your head, your elbows rock out a bit, and knuckles rock together. If your arms didn’t collapse, the “bridge” survived a sudden heavy load.
We examine a connection closely and see that high water levels have chocked the gap with pebbles. In a way it looks reassuring not to see daylight through the joint, but Bast says, “You want it to move freely, as unsettling as that seems.” The rocker would crush the offending debris instantly, Bast imagines.
Later, Bast and I visit an unnamed bridge (most bridges are given a number only) on Old Highway 80 between the Cuyamaca Rancho State Park exit and Buckman Springs. The road dips into a canyon and bends to cross a creek. We park by the roadside near two cars and hop from rock to rock down a trail on the south side. Two gold prospectors are working the shallow creek near the bridge with pans and shovels, hoping to find a little “color” in the deep pockets of sediment and sand left at this sharp bend.
Once again, the view from below is most interesting. Far from poetic, this bridge and its “underthings” are nothing more than two ponderous concrete plugs in the riverbank. Engineers brutally chopped the rails off an old bridge, left it in place, built up the abutments, and plunked another bridge five feet over it.
San Diego County’s best-known twin bridges — another case of old replaced by new — are on State Highway 94 over the Sweetwater River. A modern prestressed concrete roadbed looks like it can withstand any 100-year flood. Its precursor’s black steel rods and beams join into three separate truss systems, each with a slight hump in its back. The concrete roadbed, 20 feet wide, plunges through a willow-clogged area of the river, and double yellow lines fade in the sun, never to be repainted.
Walking here in late winter, the sky low and brooding with moisture. I’m apprehensive, an unusual emotion for someone who feels weightless — in flight — on most bridges. Rival gangs have tagged the historic bridge with looping, multicolored scrawls. White concrete entry boulders at the north end remind me of warning gates, a modern version of “Abandon hope all ye who enter here,” and dense vegetation blurs each side. The sort of place a body might get dumped.
Tension of another sort, along with compression, hold a bridge like this together. Under vertical loads, a triangle (the basic component of a truss) experiences compression of its two vertical members and tension in the horizontal bar. Again, your arms are a useful analogy. Lock fingers together, place elbows on the table spread a forearm’s length apart, and ask someone to push down on your hands. Arms are compressed, and elbows tend to move apart. If something rigid joined your elbows, this base of the triangle would be under tension.
Put a number of triangles together in varying configurations, join them with a roadbed, add transverse and diagonal bars across the top, and you have a typical highway or railroad bridge that spans hundreds of feet and carries significant loads, despite its light weight. Sweetwater’s arrangement is unusual and looks to be a combination of what’s called a camelback truss and a Pratt truss. This basic design (along with wooden trestles) built the West, from levee-channeled rivers in the San Joaquin Delta to narrow passes in the Rockies. Steel truss bridges became so common, so powerful an image of progress that Ayn Rand linked past and future technology on rails and trusses of Rearden Metal in Atlas Shrugged:
He showed her his notebook. She saw disjointed notations he had made, a great many figures, a few rough sketches. She understood his scheme before he had finished explaining it. She did not notice that they had sat down, that they were sitting on a pile of frozen lumber, that her legs were pressed to the rough planks and she could feel the cold through her thin stockings. They were bent together over a few scraps of paper which could make it possible for thousands of tons of freight to cross a cut of empty space. His voice sounded sharp and clear, while he explained thrusts, pulls, loads, wind pressures. The bridge was to be a single twelve-hundred-foot truss span. He had devised a new type of truss. It had never been made before and could not be made except with members that had the strength and the lightness of Rearden Metal.
The naysayers said Rearden’s and Dagny Taggart’s bridge on the John Galt Line would collapse. It didn’t.
There was a moment, during Pine Valley’s construction, when Bert Bezzone heard that his bridge had fallen.
“I was driving home from work one night in Sacramento and heard a newscaster say, ‘One hundred fifty feet of bridge at Pine Valley collapsed.’ I thought, ‘Do I go for the border, or what?’ Oh my. We were right at the critical stage of a 150-foot cantilever. No one had built anything in the United States like this before, and I hear this.
“Finally I got home and called maintenance in District 11 and asked if they knew anything about the collapse. No. So I asked them to check it out. About an hour later he calls me back and says, ‘That wasn’t Pine Valley. They were stripping [wood] falsework on the Japatul Valley bridge, lowering it on cables, and it tipped and slid out.’ It wasn’t even a bridge collapse. Just forms. God! Relief, I tell you!”
We reach Pine Valley and drive across in about 25 seconds. At the next exit, I turn around, drive back, and park the car on the shoulder near the east abutment. Another car pulls alongside within minutes, driven by Ed Bankston, a construction engineer with District 11 and an old friend of Bezzone’s. Bankston has the key to a hidden access manhole under this eastern end. We slide down a bank, duck under a huge concrete wall stretching into space, and crawl to a place where the ground is a few feet below the bridge.
The round hatch, free of its padlock, swings up, then falls over into darkness with a steel handclap — a 100-pound poker chip dead-dropped to a concrete floor. Noise ricochets up and down a one-third-mile-long box. Sound-effects specialists crave such an echo; grand and hollow, filled with technology frightening the timid. Think of an oil tanker’s empty hold slapping a 40-foot wave.
Lifting myself up, I also imagine that I am a virus. Flashlight-eyed contagions enter a 12-foot-high tomb sealed by calculus-worshiping cults. Above, traffic whumps across roadway joints. I stand next to a cone of light streaming up from the manhole. It paints an eerie funnel across a wall and part of the ceiling. Bezzone looks at wall joints with his flashlight near a crude, open doorway at the abutment. Bankston rises from securing the padlock on the open cover. He laughs easily, tells a fair number of tall tales, and enjoys reminiscing. He soon spots a scrap of carpet imprisoned in concrete near a joint (wet carpeting controls how fast concrete “cures”) and says, “Some of us used to come out and get that stuff after we were done. On the pay we got, it was better than the carpet we had at home. But Bert’s heard that one before....”
“Nobody’s heard that one, Ed,” says Bezzone with a smile, starting to walk deeper into the box-shaped tunnel.
“When we first started looking at this site,” he continues, his tennis shoes making no sound, “we considered four configurations: a box similar to what we have here, only made of steel; a truss; segmental construction; and filling the canyon up with spoils from cuts along Interstate 8. We would have buried half of San Diego County by the time we got through with the last option, so that went down the tube quickly. The park people [Cleveland National Forest administrators] would never buy that.
“Segmental was about 15 to 20 percent cheaper, and it allowed us to do something [the cantilever method] we really wanted to try. A German firm, Dykerhoff & Widmann, had come up with a prestress system called DYWIDAG for building bridges [without falsework, wooden forms that contain the just-poured concrete]. We’d been in the prestress and post-tension business for quite a while at that point, but there weren’t any American contractors who’d done anything like DYWIDAG.”
In Graeme Outerbridge’s landmark book Bridges, featuring 45 great bridges of Europe and the United States shown in over 300 astonishing photographs, he offers this description of a process that allowed the creation of many of the world’s most graceful bridges, including Christian Menn’s famous Ganter and Reichenau Bridges in Switzerland and Robert Maillart’s Salginatobei Bridge over the Schrau River, Schiers, Switzerland:
Concrete, like stone, is strong in compression and weak in tension. That is to say, it is able to resist pressure against it but has little ability to withstand pressures exerted to pull it apart. Reinforced concrete, developed.in the late nineteenth century, is a material in which the ability of metal to withstand tension was added to concrete’s ability to withstand compression. Iron or steel rods or beams were encased in concrete to combine the two strengths. Anyone walking by a construction site will have observed this combination — rods sticking out of concrete. It is, however, a static strength, whereas prestressed concrete possesses a dynamic one, the metal within acting like a spring. Prestressed concrete is made by casting a concrete beam with longitudinal holes. Steel cable is threaded into these spaces and then tightened into a stretched mode. The ends of the taut cables are then anchored in the ends of the concrete. This creates a force that is constantly trying to pull the beam together. This contained energy can be used to counterbalance the opposing forces in an arch that are pressing down and out. The strength of this material has allowed engineers to create bridges using a small volume of material, which in turn creates an appearance of considerable grace.
In stills taken by Caltrans photographers during Pine Valley’s construction, thickets of threaded rods continually project out of the bridge’s cantilevered ends. Tightened (“post-tensioned”) and locked in place, they controlled the camber of each roadbed as it hung in space. Not only did the great weight of each section pull the horizontal, plank-like structure downward, the column itself nodded its head slightly toward the heavier side with each pour. At times the ends “wanted to move down as much as four feet,” according to Bezzone.
To create another simple model of the forces at work, hold both arms straight out from the shoulders (the body representing one bridge column). This horizontal structure is limber, and tendons, sinews, bone, and tensed muscles (prestressed rods) hold it in place — to a point. Even leg muscles come into play. Add too much weight to one hand and stress is felt the length of the arm as well as at the shoulder. One side eventually dips.
Whatever the inspiration, Romans had the principle figured out. Archaeologists once found bronze rods reinforcing a concrete beam in the doorway of a 100 B.C. tomb.
Walking west inside the box, the sounds of traffic overhead grow louder. The bridge reverberates each time a truck or car hits an expansion joint. Our flashlights play across a sloping concrete floor littered at the edges with some kind of crumbled organic matter. Bending over for a closer look, I discover we’re walking beside drifts of mouse scat, undisturbed by water or wind, drying into a museum of fecal dust.
“Jesus Christ,” I say to myself. “It’s a hantavirus plantation!” By the time of our bridge walk, hantavirus disease had killed at least 32 people in 14 states, according to reports in the San Diego Union. Humans are infected by airborne dust containing.. .well, you know. Bezzone and Bankston are unconcerned; there haven’t been any problems they’ve heard of among bridge workers. And I know that, despite the presence of a diseased rodent found in the Cuyamaca area, the health department had reported no human infections in the county. Yet. I walk on, careful not to shuffle my feet, staying on the clean concrete near the middle. At times we see permanent prints left when the concrete was wet Homo sapiens footprints, typical steel-toed boot variety.
The Pine Valley roadbed, built of “segmentally prestressed boxes,” is a straightforward style with tapered sides now popular throughout the state. It wasn’t always so. Bezzone first developed the tapered-side look on a bridge built three decades ago in Sacramento, and he might be considered “The Father of the Tapered Bridge.”
“Everyone said the shape wasn’t going to fly,” says Bezzone. “ They aren’t going to look good,’ and so forth. Now we’ve got them all over the state. It seemed like such a basic thing at the time. It looks good and it allows the forms to drop right off.”
For the piers, design section supervisor Bezzone along with project engineer Ostap Bender brainstormed a look that “definitely evolved.”
“We considered half a dozen basic shapes and elevations, tinkered here, tinkered there,” Bezzone recalls. “We kept the general shape of an earlier design with its parabolic flare, but the need to possibly add a center roadway section altered it for the better.” Concrete bow ties now join each twin-column pier, with the largest bow ties on top where they might, if ever needed, support a third roadway box.
Anyone who’s erected a flagpole or mailbox in a hole filled with concrete knows that even a simple project can assume a decided tilt. In this case, take a 350-foot-tall pier. Plug it into solid rock on a canyon wall. Anchor it sufficiently to support part of a 70,000-ton bridge (total weight) against a few external forces like high wind and a potentially massive earthquake. Designers call the results of such events, in a classic case of understatement, “overturning moments.”
“If it wasn’t for a base of solid granite, we’d have had to dig up half the canyon to get a footing in there,” says Bezzone, staring down the length of one pier through a narrow gap created by a mid-span hinge. Using similar prestressing techniques as those used in the cantilevered boxes, the contractor anchored a “transfer block,” a slab of concrete about a foot larger than the bridge’s footprint. Cables reach deep into rock, stretched taut with jacks.
“We prestressed the footing to the ground. In essence we engaged a big mass of granite to hold the bridge in place. It’s become a common method since then.” Another benefit was minimal damage to the site. After 20 years the entire bridge appears to have been airlifted to a pristine canyon, lowered into waiting holes, and cemented in place: there are no heaps of rubble, permanent access roads, or other disturbances to canyon walls and bottom.
Flood levels are another consideration in a bridge’s construction over any water feature, but not in the case of this high structure. Still, engineers must file a report detailing the possible effects of stream fluctuations. On page 36 of the Department of Public Works — Division of Highways “Report of Completion — Structures for the Pine Valley project” by R.P. Sommariva and R.J. Zelinski, dated March 28,1975, one finds this tongue-in-cheek letter amidst 103 pages of technical grouting records, joint seal and stressing reports, and costs (final cost was $10,048,987.08):
Hydraulic Report, Pine Valley Creek
We regret the fact that we cannot supply the daily record of stream surface elevations as required in the Construction Records and Procedures.
The reason we are not able, is that the torrential rains and turbulent stream conditions in March 1973 washed out our measuring gauge. Though stream flow conditions did not rival those predicted for the 100-year storm (20' deep, 10 fps, and 18,000 cfs), they were the most severe that had been seen in over a decade by the resident meteorologist of Pine Valley, Jeremiah Sagebrush.
During that dreaded month, the once-meek Pine Valley Creek gained the respect of all who formerly scoffed at her. In this period, the creek, which is normally a trickle even at full moon, reached the magnanimous proportions of eight feet wide and 3Vi (three and a half) feet deep.
In spite of the ferocity displayed by the creek, we construction engineers unanimously put our reputations on the line in stating that there is nothing to fear. We feel that the Pine Valley Creek Bridge will withstand the turbulence and will refuse to be intimidated by Pine Valley Creek throughout its life.
We recommend no future stream flow studies. The 431-6” of freeboard should be a satisfactory clearance except possibly for low-flying aircraft.
When bridges fall down, engineers lie awake at night. They lie awake much of the time anyway. Bezzone, during the design phase of Pine Valley Creek Bridge, kept a pad of paper by his bedside. Most nights, by the third or fourth time he’d snapped on the light to take notes, his wife felt like yelling at him to either turn it off or get out of the room. She did, on occasion, but his marriage survived several hundred bridges that weren’t standard Drawer A knockoff designs.
According to Bezzone, after the Loma Prieta quake in the Bay Area, Caltrans looked at every bridge in California and put them in three categories: those that needed work right away, those that were in between and required further study, and those that didn’t need anything. The really vulnerable bridges were single-column connector types and bridges that had some sort of intermediate hinge.
“We had those pretty well done [upgraded],” says Bezzone. The notable exception was the I-5 and I-210 interchange, where a section’s collapse in the recent Northridge quake was the second failure at this locale, this time while a bridge was in the midst of being upgraded.
“I had some really bad nights over the first failure in 71,” he recalls. ‘Two people were killed. I anguished over what we could have done or should have done…Was I professionally lax? We ended up in court. By that time I had satisfied myself. The judge ruled in our favor. He was convinced we were working state of the art.
“Most of the worst faults in California are located where all of the bridges are. L.A., San Diego, and San Francisco are the most seismic areas, and that’s where all the population is, so that’s where the bridges are. And the buildings.”
On the western half of the Pine Valley Creek span, we stop to examine one of the bridge’s two seismic joints, the first of their size and complexity in an American bridge. The ’71 Sylmar quake instantly changed the way Caltrans engineers approached bridge design.
Interlocking like timbers in a Shaker bam, each segment of box-beam roadway in Pine Valley is free to move back and forth or up and down, bouncing or sliding on thick neoprene pads. Two faults sleep close by, one seven miles away, and both have a maximum „ credible rating over 7.5. Push high winds against the bridge’s huge surface area, and the sail effect might also be enough to cause problems.
In order to check the system’s effectiveness, engineers did a computerized analysis of seismic forces, a “time history” of what happens to the bridge under load. Until the 70s, Caltrans didn’t have the capacity to do such calculations on their computers, so Bezzone feels that this is probably the first bridge in the world to get this treatment on the drawing board. The digitized, graphed behavior of two actual California earthquakes (one was El Centro, 1940) “attacked” the Pine Valley design inside Caltrans’s mainframe computer. Eight hours later Bezzone had a few answers. The joint’s design was viable, but anchor cables were added to restrain it from opening too far in an extreme earthquake. And another set of neoprene bumpers is now ready to absorb any rebound if the cables do come into play.
Early bridges had the resiliency of natural materials. The simplest were felled or fallen logs spanning a stream. I remember walking a mile through scrub willow along the edge of a High Sierra torrent above King’s Canyon, searching for a place to cross Bubb’s Creek. I found a dead giant cradled in the boulders, its limbs peeled off by a few seasons of spring melt water, the barkless trunk wet with mist. Crossing it with a heavy pack was as primordial as carrying a deer carcass across an Ice Age river. I slipped, fell into waist-deep water, caught myself on an amputated branch’s stump, and ended up shimmying across on my butt. Five minutes later, drying my socks on a rock, I watched a bear trot over as if it were a highway.
American settlers soon customized the fallen log into a more stable slat-and-log combination: several logs side by side joined by planks to walk on. If there were horses or oxen on the trail (which was probably becoming a road); the bridge needed to be wider, stronger. A king post bridge became popular, the forerunner of a basic truss bridge. Two stringer beams, each cut and fitted with a king post and two angled compression braces, spanned the distance between the stream or river banks. Split or pit-sawn planks provided the roadbed. Dry masonry abutments were a sturdy connection to solid ground.
The first covered bridge in America was built in 1805 over the Schuylkill River in Pennsylvania. According to artist/historian Eric Sloane in Diary of an Early American Boy, no covered bridges predated this. The idea caught on so fast that soon all wooden bridges in the East were covered. Word spread that the protected bridges lasted twice as long as their exposed counterparts.
Covered bridge design probably migrated West with the 1849 Gold Rush. It’s not known if San Diego had a covered bridge, but it would have been very possible up in the Laguna Mountains. My favorite covered bridge in California is at Knight’s Ferry on the Stanislaus River, about a 45-minute drive east of Stockton. In summer between college semesters, we’d flee valley heat to swim in the slower, deep stretches of river either beneath the bridge or a few hundred yards upstream out of sight of houses. Sometimes bikers rode their Harley-Davidsons back and forth over the bridge’s sun-and shadow-ribbed planks, thrilled with die way their engines sounded inside a wooden box that amplified—but also mellowed — a chopper’s growl, like a fine stereo speaker. Another great California covered bridge is Honey Run Bridge on the road to Paradise, outside of Chico.
San Diego has a few bridges that seem primitive but homey, convenient (when built in the early 1900s) for pedestrians going home from a streetcar line and needing to cross a canyon or two. Of them all, the Spruce Street suspension bridge is a spectacular jounce, its twin cables bounding at mid-span if you dare walk or run. Like most suspension bridges, strong cables rise to towers at each end, go over the top, and grab the earth with massive, underground concrete anchorages. It’s not the Golden Gate, but the principle is the same.
Bridges like Spruce are “dead load” bridges, a grim-sounding term that has nothing to do with mortality. Engineers use it to describe bridges that are designed to carry their own weight and little more. (The Spruce bridge, however, was dramatically overengineered and could probably hold hundreds of people safely. “Probably” is the operative word here, if anyone is thinking of having a bridge-in.)
A pedestrian bridge now under construction will soon span Washington Street in Hillcrest east of State Highway 163. It is one of a new generation of pedestrian bridges being built amid San Diego’s streets and canyons after a lapse of at least 50 years.
Another pedestrian bridge — touted by the publicists at Scripps as the first cable-stayed bridge in California — links the east and west sides of Scripps campus. It is now a favorite destination of bridge lovers (and other lovers) who enjoy the effect of walking off a 135-feet-long diving board into a setting sun. The futuristic-looking suspension system, in which cables angle down like harp strings from a tall post, has been popular in Europe (especially Germany) for some time. Several Rhine River crossings are cable-stayed, including one at Flehe and another at Speyer. Both were built in the 1970s.
Designed by Frieder Seible, professor of structural engineering at the University of California, San Diego, Scripps Crossing rests one end on the stair and elevator tower of a new building designed by architect Frederick Liebhardt. Nine stainless steel cables hold an 18-inch-deep arching deck over La Jolla Shores Drive near Scripps Pier. Seible hopes to build a similar, but much larger bridge of lightweight carbon fiber materials across Interstate 5. After a blush of publicity in late 1993, the project seems to have stalled. Seible has been unavailable for interviews (like most bridge experts caught up in studying the effects of recent quakes in Los Angeles). Bert Bezzone, when asked about the bridge, pragmatically called it “more of a toy for the professors. It’s a very expensive bridge for the site.” The claim that this is the first cable-stayed bridge in California is also somewhat incorrect, according to Bezzone.
“If you’re talking the first pedestrian cable-stayed bridge, then yes,” he says. “But I know of a small cable-stayed bridge on State Highway 32 from Chico west to Interstate 5 that was built 15 or 20 years ago. It’s a movable bridge and is cable-stayed in the open position.”
Definitions aside, Scripps Crossing is a bridge that will be treasured by San Diegans for a century, a modem Spruce Street bridge, a bridge with the vision to interact aesthetically with its site.
The City of Poway has four new pedestrian bridges, and Poway Director of Engineering Mark Weston says, “I’ve become a fan. The kids were finding their way across the creek anyway via stepping stones and through the bushes. Now they have a shorter distance to school. We’ve provided links between neighbors, between a community park and surrounding homes....”
Many other modem pedestrian bridges exist in San Diego, hidden in office parks, apartment complexes, hotel lobbies, golf courses, and on university campuses. The San Diego Zoo, Wild Animal Park, and Princess Resort’s Vacation Village have a plenitude of bridges, most of them built like a Swiss Family Robinson fantasy. One wooden trestle bridge on the Ml Woodson Golf Course in Ramona plunges several hundred yards down into an oak-tree cloaked canyon with all the banked, rattling energy of a serpentine roller coaster track. Another bridge on the course is a fine replica of a stone arch bridge.
I grow tired of Pine Valley’s darkness, the constant traffic overhead, the sense that I am in the marrow of a cool, concrete bone. I’ve been down at the bottom of the canyon before, and I long to be there now. Horseback riders and hikers see Pine Valley’s simple, alien beauty from best vantage. Secret Canyon trail (completed in 1992) passes under the bridge 1.8 miles downstream from Old Highway 80. Hiking there in early spring this year, I found a bizarre auto-part junkyard — scraps of Fresnel taillights, entire headlights and plastic bumper parts, pickup trucks’ bed liners, even a Taurus grill — strewn over wilderness. High winds, not collisions, stripped these parts loose. A Santa Ana is a mad, eye-gouging wrestler, ready to pluck out what is loose, unsound, temporary.
But we push on to the far end and a narrow, light-filled gap between bridge and abutment. There I see the remains of a campfire and a charred newspaper dated November 17, 1991. An empty Keystone beer can lies on its side. Someone has bent a quarter-inch steel baffle and forced their way in to find shelter. It must have been a cold, sleepless night. This foot-thick concrete never warms up. The mice arrive with darkness. Doves huddle in quake joints, flapping wings, crying, flapping, never settling down, turning all night in their nests like feathered tops on a stone table.