The Drawbridges of the Delta


Three-Mile Slough Draw Bridge

By Aleta George from Estuary News Magazine 

The moveable bridges that cross the rivers and sloughs in the Sacramento-San Joaquin Delta were built in the first half of the 20th century, and most are operated by control panels as old as the bridges themselves. A day spent touring these strong-boned grande dames on backwater levee roads or zigzagging across the Sacramento River on scenic State Route 160 is time well spent. But that’s leisure time, and for the tens of thousands of commuters who use the heavily trafficked corridors of the Delta, the four-to-twenty-minute wait for a bridge to open for marine vessels can be frustrating.

Although vehicles far outnumber vessels these days, watercraft has the right of way. “When we open the bridge, we follow United States Coast Guard rules and regulations,” says Rio Vista Bridge operator Phil Pezzaglia, citing federal regulations for navigation and navigable waters that a drawbridge must open “promptly and fully” upon request from a vessel.

When road vehicles proliferated a century ago, bridges were needed to cross the waterways of the 55 constructed islands in the Delta. Today, on Georgiana Slough and the Sacramento, Mokelumne, and San Joaquin rivers alone, there are 22 narrow moveable bridges that represent three types: Bascule bridges that leaf open with the help of concrete counterweights; swing bridges that pivot from a fixed, central point; and vertical lift bridges that raise a segment of the roadway between two towers. On average, the two-lane bridges are 23-feet wide, a tight squeeze for two seven-foot-wide full-size SUVs to pass.

All the bridges in the Delta are controlled by operators or tenders, who are either stationed at the bridge house or on call. Hope Kirch, 77 years old, has been an operator at the Walnut Grove Bridge for 21 years. Built in 1951, this Bascule bridge connects east and west Walnut Grove. 

“The Walnut Grove Bridge is our gem,” says Bill Rowton, bridge operations supervisor for Sacramento County, which manages the bridge along with four others. 

I visited the bridge one spring morning with Kirch on duty in the bridge house. Before opening upon request from a vessel by phone, radio, or a long and short blast of their horn, Kirch sounds a warning bell and goes outside to ensure the bridge is clear. Once the cars have stopped and the bridge is free of pedestrians, she lowers the traffic safety gates and moves inside to open the bridge from the original control panel. 

The two leaves open and rise in the middle with a grinding metallic sound, causing nesting swallows to panic and fly in circles. When Kirch isn’t opening or closing the bridge, she enjoys watching river otters, sea lions, and swallows from the bridge house.

Roughly 6,600 vehicles cross Walnut Grove Bridge daily, but on an early Saturday morning only about 20 vehicles had to wait for the four-minute opening. In 2021, the bridge opened 591 times, less than two times a day. 

Different agencies own, manage, and operate the bridges. Caltrans District 4 is in charge of six, including the Mokelumne River Bridge. Built in 1942, this swing bridge crosses the Mokelumne River on California SR-12 and has the greatest number of openings among all Delta bridges. In 2019, the bridge made way for boats approximately 1,600 times, says Pezzaglia. Nestled into tules on the banks of the river below the bridge, I clocked a seven-minute swing. While seven minutes doesn’t sound like long, traffic can back up fast with up to 21,000 vehicles driving SR-12 daily, with nearly all of those crossing the Mokelumne and Rio Vista bridges.

The Rio Vista Bridge (also called the Helen Madere Memorial Bridge) is one of five vertical lift bridges in California, and you can see its two lift towers from miles away. The original Rio Vista Bridge was a Bascule bridge (like the Walnut Grove Bridge) built in 1918. Construction of a new bridge started in 1943 on the east side, but due to World War II steel shortages didn’t conclude until 1960, when it was named the most beautiful steel bridge in its class by the American Institute of Steel Construction.

The 306-foot-long lift span provides 135 feet of vertical clearance for vessels, a height that is necessary to accommodate cargo ships traveling to the Port of Sacramento in the Sacramento River Deep Water Ship Channel. Last year the bridge opened 974 times, an average of less than three times a day.

The process of lifting and lowering the span for marine traffic requires vehicles to stop for about 20 minutes, a significant wait made longer when cars ignore the amber, then red, lights signaling that the bridge is about to close to traffic. “At an intersection, people stop their cars at a red light. When you have a bridge with a red light, it seems people say, ‘Put your foot on the gas!’” Pezzaglia says. “I have counted as many as 50 cars that blow through the red light.”

Once the cars do stop, Pezzaglia engages the safety gates on the roadway and walkway, and raises the safety barriers. These precautions are warranted. According to a 1944 article in the Sacramento Bee, a tomato farmer travelling across the old bridge didn’t notice that the span was opening. By the time he did, he had to jump out of his truck. His truck smashed into the side of the bridge, the farmer got 36 stitches, and the bridge was left with a ketchup clean-up.

On the modern-day bridge, the operator pushes buttons and levers on the control panel (the original from the 1960s) to lift the span at 50 to 60 feet per minute. A safety feature ensures that both sides are rising equally. If a five-inch skew is surpassed, the process will stop.

But it wasn’t a screwy skew that infamously gummed up the Rio Vista Bridge in 2018; it was a failed gear box. At about 2:30 pm on Thursday, August 9, the operator opened the bridge, but couldn’t get it down and traffic backed up for miles. Specialty crews from Caltrans District 3 (which owns the bridge) and District 4 (which maintains and operates it) were able to lower the lift span by Saturday. Then it was stuck in the down position. To accommodate vessels, a team of electricians and engineers devised a workaround with fuel-powered winches, and crews with radios on both towers coordinated a lift  that would not exceed that five-inch skew. They used the technique to raise and lower the bridge for more than three weeks until the repaired gear box came back from the manufacturer.

To ensure that nothing like this recurred, Caltrans put in place an emergency repair plan to upgrade the bridge’s mechanical and electrical systems. New backup drives for each tower have been installed, and next year Caltrans will put in new drives for the main system. Upgrades to the bridge house include an automated identification system for tracking vessels and a camera system to monitor the bridge. The estimated cost of the emergency upgrade is $32 million, which will include a new lightweight pavement for the lift span. 

The steel bridges in the Delta are old, but safe and sound, says Caltrans project manager Soka Soka. “On the Rio Vista Bridge we’re putting in a new electro-mechanical operating system to catch up with the available, modern technologies. It’s like we’re giving life to an old thing with new blood circulation.”

Yet even with a new circulatory system, the Rio Vista Bridge will take 20 minutes to lift and lower, a wait made more bearable if only commuters would embrace the views of pontists (old-bridge enthusiasts) who travel to the Delta to enjoy the unique history of these grande old dames.

About Kevin

Manager of Mainframe Operations and Optimization – USS-UPI, Co-Founder and Board Member - Friends of Oakley A Community Foundation, Trustee RD 2137, Advisory Board – Opportunity Junction
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