Movable Bridges - I Street Bridge

I'm standing in downtown Sacramento looking across the river at the I Street Bridge, the CalSTRS Building, and the Sacramento Pyramid (or Ziggurat).

This double-deck swing bridge carries two sets of railroad tracks on the bottom deck and motor vehicles (and pedestrians) on the top deck. The swing mechanism is still very active. The bridge was built by the American Bridge Company in 1912 and its currently owned by Union Pacific.

Movable Bridges - I Street Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Movable Bridges - Jibboom Street Bridge (2)

The American River empties into the Sacramento River just west of the Jibboom Street Bridge. There are many other rivers in Northern California that flow out of the Sierra Nevada Mountains into the Sacramento River. However, since much of the American River is whitewater rapids it's hard to understand why a movable bridge crosses it. Perhaps that's why the swing mechanism hasn't worked in many years. The bridge sits on a huge, cylindrical pivot pier and the two ends rest on piers that also support Parker truss spans. As I mentioned before, swing bridges are hardly ever built and are slowly being removed from waterways. The big exception is the previously studied Spokane Street Bridge in Seattle (shown on the April 29th and 30th blogs), which is huge, with the piers built outside the channel, and has won several design awards.

Movable Bridges - Jibboom Street Bridge (2)by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Jibboom Street (Richard's Blvd) Bridge

Over the last few weeks we've looked at every bridge crossing the American River between it's confluence with the North and Middle Forks (in the Sierra Foothills) to its confluence with the Sacramento River (at the Jibboom Street Bridge). You can see the Sacramento River just beyond the bridge (in the photo) where all the speedboats congregate.

Many of the rivers coming out of the northern Sierra Mountain Range empty into the Sacramento as it flows south from Mt Shasta (for 450 miles) to Suisun Bay. Perhaps I can provide photos of all the bridges crossing the Sacramento River after I photograph a few of the bridges I'm still missing.

According to Historic Highway Bridges of California (published by Caltrans in 1990), the Jibboom Street Bridge is a cantilever swing bridge. The main span is a 351 ft long swing through span (on the left). The side spans are through Parker trusses. The bridge was built in 1931.

The swing span hasn't worked in many years, which is just as well since large vessels shouldn't be going up or down the American River. Its far too shallow and there are too many rapids. I wonder where the name Jibboom came from? It sounds like somebody's last name. Maybe a business person from the days of the Gold Rush.

I mentioned a few days ago that cyclists are encouraged to take the SNRR Bridge across the American River during the winter because the Jibboom Street Bridge can be under water due to flooding. Perhaps the swing span no longer works because the bridge is periodically under water? I remember flooding damaged the swing and lift mechanisms on most of the movable bridges along the Gulf Coast after Hurricane Katrina.

American River Bridges: Jibboom Street (Richard's Blvd) Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: I-5 Expressway Bridges

It's a mile and a half downstream from 12th Street to the next two bridges across the American River. The I-5 Expressway Bridges are a pair of 28-span, continuous concrete box girder superstructures supported on pier walls. Each bridge carries five vehicle lanes. They were built in 1968, which seems to be when most of the highway construction was going on in Sacramento.

Note the architectural treatment at the ends of the piers, the vertical exterior girder, and the rather monolithic appearance of these bridges. That must be the modern, streamlined appearance of late 1960s bridge design in California.

Besides the occasional kayak, you don't see a lot of boats on the American River. Just downstream (near the confluence with the Sacramento River) the speed limit restriction is lifted, the water is much deeper, and the river is filled with jet-skis, motorboats, and big yachts.

American River Bridges: I-5 Expressway Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: 12th Street Bridge (2)

Another view of the 12th Street Bridge. There was a guy under the bridge working on a bike (on the closest pier foundation). Light rail trains roll by every 20 minutes along the east side of the bridge. The nearby Sacramento Northern Railroad Bridge used to carry electric trains many years ago, but now it carries cyclists.

It's hard to take a bad photo of this bridge. Standing on the north embankment provides a nice view of the four-banded barrier rail and the pedestals supporting electric power for the train.

Like the nearby 16th Street Bridge, this structure is a city street on the south side and becomes an expressway (State Route 160) on the north side of the bridge. It touches ground briefly north of the American River before becoming a 14 span viaduct over streets, Union Pacific tracks, bike trails, parkland, etc.

American River Bridges: 12th Street Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: 12th Street Bridge

I like this bridge so much, that I'm going to provide another view of it (at deck-level) tomorrow. When I showed it to the head of Caltrans' Office of Aesthetics, he expressed surprise that it was in Sacramento. It has a timeless quality, like some architectural detail that has been repeated with subtle changes throughout time.

I like how the piers look like they are splitting by a mitosis-like process (the bridge was widened from two to four lanes in 1934) and I like the rounded cutwaters that become concave on top to support power poles.

The 12th Street Bridge is a five-span, closed spandrel reinforced concrete deck arch bridge.  It was built in 1915 but it has a modern look, as if some far-sighted architect or engineer had seen something by Frank Lloyd Wright and intuited the works of Corbusier. All of the shapes have moved beyond the purely geometric to something organic or anthropomorphic.

American River Bridges: 12th Street Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: 16th Street Bridge

I spent some time trying to decide what to call this bridge. Caltrans named it the American River Bridge, but that's what they call every bridge over the American River. Its just where 16th Street becomes the right side of State Route 160 near downtown Sacramento and so I felt the 16th Street Bridge would be most descriptive. I also thought about providing the latitude and longitude for this bridge. Perhaps I can provide some header information about each bridge including the latitude and longitude?

You can see the two truss bridges we recently studied about 200 meters upstream. The 16th Street Bridge is a six-span, continuous reinforced concrete box girder bridge on very thin, wide pier walls. It was built in 1968 and carries three lanes of traffic northeast over the American River.

You can see the variation of water levels by the water stains on the pier walls. We are approaching where the American River ends at the Sacramento River. It is the confluence of these two rivers that is so often a source of flooding in downtown Sacramento. The last big flood was in 1986 and a lot of time, money and energy since then has been spent on strengthening the levees along these two rivers.

American River Bridges: 16th Street Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Sacramento Northern Railroad Bridge

Just 150 meters downstream from the Western Pacific Railroad Bridge is the Sacramento Northern Railroad (SNRR) Bridge. This iron truss bridge was built at the turn of the last century. It was used by both the SNRR and by the Northern Electric Railroad.

About ten years ago, the track and ballast were removed and this railroad bridge was converted for bicycle use. In fact, the SNRR right-of-way north of the bridge was converted to a bike trail.

The area downstream can become flooded during the winter and cyclists are encouraged to take this bridge into downtown Sacramento rather than Jibboom Street Bridge which may be under water.

Note that the pier foundations are exposed and surrounded with cobbles due the gradual scouring of the river bottom.

American River Bridges: Sacramento Northern Railroad Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Western Pacific Railroad Bridge

Although it's hard to tell from this photo, we are approaching downtown Sacramento on our trip down the American River. I took many of these photos from my kayak, which was difficult as the boat tended to rotate whenever I put down my paddle.

The Western Pacific Railroad Bridge is a three span, steel through truss structure supported on pier walls and seat-type abutments. Although the bridge crosses the river at a high skew, the piers were built perpendicular to the bridge (rather than parallel to the river) and so the designer didn't have to adjust the ends of the truss spans to match the skew. On the north end of the bridge is a short, timber trestle section that allows bicyclists to go under the two sets of railway tracks carried on the bridge. The pier foundations are clearly visible, even at high tide above the river's surface. When the bridge was built (at the beginning of the 20th century) the riverbed was much higher then it is now and the resulting lower river leaves the pier foundations exposed.

The Western Pacific Railroad was formed in 1903 to build a standard gauge track connection to the Pacific. The company was acquired by the Union Pacific Corporation in 1983.

American River Bridges: Western Pacific Railroad Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Union Pacific Bridge (3)

In just eleven days, Union Pacific managed to replace the 1440 ft long, fire damaged timber trestle structure with a precast concrete superstructure supported on two steel H pile bents with concrete bent caps.
The trestle carries two sets of railroad tracks on ballast.

Eleven days has to be a world's record for building a quarter-mile-long bridge. Union Pacific must have had all the material in a nearby yard. Even so, they must have had three or four pile driving units working at the same time to have driven 200 piles in a week. Then there was less than a week to install the bent caps, place the precast superstructure, put down the ballast, and lay down a quarter mile of track. There must have been so many workers, that its amazing they didn't get in each others' way!

American River Bridges: Union Pacific Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Union Pacific Bridge (2)

This timber trestle acted as an approach structure for the steel truss railroad bridge over the American River we saw yesterday. I have often wondered whether an embankment or a bridge makes a less expensive approach for a river crossing. At this location however, a bike trail had to pass under the railroad tracks.

This timber trestle structure must be as cheap a bridge as it's possible to build. Lateral (and longitudinal) stability is provided by a pair of diagonal braces. The axial members are slightly battered to provide a little more stability. The axial members are anchored to the top and bottom beams by metal plates with narrow rims. Still, it must have been a remarkably strong structure to carry the dozens of freight and passenger trains that rumbled over it every day.

I wasn't aware of the difference between timber preserved with resin from the creosote bush and timber preserved with resin made from petroleum products, until I did some research for this article. It must have petroleum-based creosote that made this timber structure so combustible. Someone set fire to the bridge and it made a tremendous blaze with a dense cloud of smoke that could be seen from 50 miles away. In hindsight, an embankment supported by retaining walls seems like a cheaper investment, but Union Pacific replaced this structure with a steel trestle bridge in less than two weeks. We'll look at this new structure tomorrow.

American River Bridges: Union Pacific Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Business 80 Expressway Bridge

About two miles further downstream is the Business 80 Bridge. It's an eight-span steel plate girder bridge on oddly-shaped two column bents. The tops of the columns have pedestals that support the girders. The bridge was built in 1954 and renovated (and seismically retrofitted) in 1996.

This is a very busy bridge and expressway, and it's usually stop and go during rush hour. Its also quite noisy and you can hear the traffic from a mile away. I think steel plate girders must be noisier than concrete box girders.

American River Bridges: Business 80 Expressway Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Fair Oaks Blvd. Bridge

Half a mile downstream from the Guy West Bridge is the three camelback truss spans of the Fair Oaks Boulevard Bridge. It is a three-span steel, through truss bridge supported on pier walls and seat-type abutments.

On the east end of the bridge is Fair Oaks Blvd. and on the west end of the bridge the road splits into residential 'H' Street and commercial 'J' Street and the entrance to California State University.

There's no room for bikes along the shoulders of this bridge and the sidewalks are so narrow that there's not enough room for cyclists to pass each other.

The bridge got a major renovation and repainting a few years ago. The entire bridge was wrapped up tight to prevent any of the lead-based paint from falling into the river. It must have been very unpleasant to work inside that cage of steel trusses and plastic tarp.

American River Bridges: Fair Oaks Blvd. Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Guy West Pedestrian Bridge

Less than a mile downstream from the Howe Avenue Bridges is the Guy West Pedestrian Bridge across the American River. This is the main pedestrian entrance into California State University in Sacramento. The bridge was named after Guy West, who was the founding president (in 1947) of what was then Sacramento State College.

The bridge is said to have been designed to have the same relative dimensions as the Golden Gate Bridge, which has a span of 6500 ft. That makes this bridge about 1/10 the size of the Golden Gate Bridge.

the Guy West Bridge was built in 1966 at a cost of $636,000. It's owned by the University who has been trying to give it to the city or the state since it doesn't have the resources to maintain it and it needs to be repainted, which will cost millions of dollars.

American River Bridges: Guy West Pedestrian Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Howe Avenue Bridges

Just a couple miles further downstream are the Howe Avenue Bridges. Each bridge is an eleven span, reinforced concrete box girder bridge carrying two traffic lanes and a sidewalk. This is the most popular kind of bridge built in California and the industry is very competitive for cast-in-place construction. The bridges are supported on tall, thin pier walls and they were built in 1969 and never widened or seismically retrofitted.

American River Bridges: Howe Avenue Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

American River Bridges: Watt Avenue Bridge

When I do kayak through the rapids downstream of the Harold M Richey Memorial Bridge, it takes over an hour to get to the next bridge which is about four miles further down the American River.

The Watt Avenue Bridge is a thirteen span, continuous, reinforced concrete T-beam structure supported on pier walls. It was built in 1961 and widened to eight lanes in 2002. The widening included better accommodations for bicyclists and large balconies for people to congregate and look down at the river. It even has a water motif that was embossed and painted on the bridge.

It seems to me that the current is quite strong, and I have to slow down the kayak and aim for the bank or get swept downstream. You may also notice that there are no boats on the river. There is a speed limit of only a few knots and the river gets shallow and so most of the boats are further downstream.

American River Bridges: Watt Avenue Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.