CR4® - The Engineer's Place for News and Discussion®


"An expert is a man who has made all the mistakes, which can be made, in a very narrow field." -Niels Bohr

These words frame the OH CR4P! blog, a place which encourages engineers to discuss, reminisce, and learn about mistakes, failures and mishaps made by those who have become "experts" the hard way.

The Submarine That Got Stuck in the Mud

Posted August 20, 2018 12:00 AM by RSBenner

Although I was never in the US Navy, I had the opportunity to climb around quite a few submarines in my younger days. Although this did not make me privy to all the rules surrounding a submarine, I imagine keeping the boat off the river bottom and out of the mud has to be one of them. However, in the case of the USS Guitarro, this rule was broken.

The USS Guitarro (SSN-665) was a nuclear powered, fast attack submarine of the Sturgeon-Class. Built at the Mare Island Naval Ship Yard in Vallejo, California, she was launched on July 27, 1968. After a submarine is launched, however, it does not immediately get commissioned. A series of acceptance tests must first be passed before the boat is admitted into service for the US Navy. However, in the case of the USS Guitarro, this rule was broken.

On May 15, 1969, the Guitarro was moored at Mare Island during its acceptance testing phase. On this day, a group of workers began instrument calibrations in the rear of the ship. This calibration required 5 tons of water be taken into the aft ballast tanks. About 30 minutes later, a different group began working on a project which required the boat be within a half degree of trim. The group reported a two-degree up-bow attitude (a result of the water added by the first group of workers) and added water to the ballast tanks towards the front to achieve their objective. These two groups, each unaware of the other, continued to add water to their respective ballast tanks for 3 ½ hours. Twice during this time, security personnel informed the trim workers that the boat was sitting so low that water was occasionally entering an uncovered manhole in the bow section. There was no response to this warning.

While the trim workers were on lunch, the aft workers finished their calibrations and began emptying the rear ballast tanks. About the time the trim workers returned from their break, both groups noticed that the boat was severely lower at the bow and that water was pouring into the open front hatches. Although the workers attempted to close the hatches and watertight doors within the submarine, lines and hoses running through them prevented it. The Guitarro continued to fill with water until she sat in the mud on the bottom of the Napa River, earning her the nickname “Mare Island Mud Puppy.”

The Guitarro was raised from the mud three days later. The sinking caused a 32-month delay in her commissioning and damages were estimated at $15 to $22 million. She was finally commissioned on September 9, 1972 and remained in service until May 29, 1992.

Investigation into the sinking identified a problem in the construction process – it lacked centralized control and responsibility. As the saying goes, the bow half didn’t know what the aft half was doing.


6 comments; last comment on 08/21/2018
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French Trains Too Fat?

Posted August 06, 2018 12:00 AM by RSBenner
Pathfinder Tags: france French Train

The National Rail Operator in France, the SNCF, states on their official website that nearly one million passengers ride the Regional Express Trains, or TER, every day on one of 9,500 TER or regular coach trains. That is a large operation! With the popularity of rail travel, it was decided that new, higher capacity trains would be ordered to meet the customer’s expectations.

SNCF had contracted with Réseau ferré de France (RFF), the company in charge of the tracks, to work out the measurements for the new trains. However, during this investigation, RFF only measured modern stations and failed to factor in that 1,300 of the 8,700 total stations were built more than 50 years ago – and that these stations had narrower platform openings than the stations measured.


So, by May of 2014, with 341 of the 1,860 trains delivered, work had already begun widening the affected stations. Making the original 15 billion euros ($20.5 billion) price tag of the project possibly increase by 100 million euros.


In July of 2015, it was reported that the trains intended to be used for passage between France and Italy could not be used for that purpose. Why? Because the trains are too tall to fit through the mountain tunnels between the two countries.

Maybe they need a new measuring tape…


24 comments; last comment on 08/08/2018
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The San Fran Skyscraper with a Six-Inch Slant

Posted September 28, 2016 9:05 AM by HUSH

Skyscrapers are a lot more to a city than just real estate. They represent financial prosperity and engineering acumen. They transform the identity of a city, emerging as a new shape that must be depicted in skyline silhouettes. When tourists arrive, they flock to the Empire State Building or Willis Tower for ten-mile views and selfies.

For the city of San Francisco, skyscrapers are being built quickly and steadily, with 14 over the last 14 years and another 10 expected by 2019. San Francisco has a complicated history with skyscraper development, seeing a spurt of buildings over 200 ft. between 1890 and 1930, another era of upward expansion between 1955 and 1972, and yet another that kicked off shortly after the turn of the Millennium.

There are several reasons for this boom-or-bust building cycle in the City by the Bay, ranging from a very low building height limit (areas in yellow on the map have a limit of just 40 ft.); overprotective laws against ‘Manhattanization;’ laws that ensure community areas such as parks and plazas aren’t oppressively shadowed; historical ordinances; and advances in seismic engineering that show tall buildings are safer than smaller buildings, as they are constructed to cope with some lateral deflection anyhow.

Millennium Tower, opened in 2009 in San Fran’s South of Market neighborhood, has been the source of some controversy lately. Millennium Tower has sunk 16 inches and now tilts 6 inches, and the sink could double before the building finally settles. In a city with major earthquake concerns, the poor structural integrity of the building is generating unease for its residents and neighbors.

Now people are trying to figure out who to blame.

Is it the tower developers? Millennium Tower includes a concrete mat-slab foundation and 950 friction piles, each 60 to 91 feet long, that are drilled into the underlying soil composed of mud and fill after the 1906 earthquake ruined much of the neighborhood. For friction-type foundation piles, the load capacity is solely based on the soil’s ability to provide friction against the shaft of the pile. Historically, buildings on friction piles have done quite well in San Francisco beforehand, although there has never been one as heavy on top of such squishy soil.

Is it the tower’s new neighbors? Across the street, four buildings are being erected by Transbay Joint Powers Authority, including what will become the city’s tallest tower. Each is being constructed with end-bearing piles, which are driven 200 ft. into the ground to the Franciscan Assemblage bedrock. Millennium Tower developers and engineers accused the new construction of dewatering the soil beneath the Millennium Tower, resulting in the soil compressing and destabilizing the tower’s foundation. The authority denies the dewatering accusation, and says Millennium is simply a case of poor engineering.

Is it the fault of the city? The city had previously rejected a similar tower in the area in 2004, under grounds that friction piles wouldn’t be enough to support the project. Apparently the same questions weren’t raised this time around, because the city didn’t have the engineering expertise to evaluate the soil integrity of the project, and didn’t have the ability to make Millennium’s builders do the evaluation. Instead the city relied on computer models provided by the developers.

Who is to blame is ultimately up to the courts to decide. Now engineers have some options for ‘fixing’ the tower.

· Remove the top 20 floors

· Reinforce soil underneath building

· Balancing the lean with a heavy building on the other side of Millennium Tower

· Doing nothing, as Millennium Tower promises the building is still structurally sound

· Do nothing, and move residents if/when the tower approaches a tipping point

Fun fact: Millennium Tower received nine awards for excellent design and engineering. Today, the project looks like it will eventually be condemned.

Who do you think is to blame? And how do you think Millennium Tower could be rescued?

21 comments; last comment on 08/07/2018
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World's Most Dangerous Dam Threatens Up to 1.5 Million

Posted March 30, 2016 10:16 AM by HUSH
Pathfinder Tags: civil enginering dam flooding grout

There could be an unprecedented engineering disaster in the weeks or months ahead. Mosul Dam in north Iraq is dangerously close to collapsing, years after being identified as fundamentally flawed and in need of major overhaul.

(Edit: NO, this is the correct dam!)

Saddam Hussein constructed the dam during the Iran-Iraq war. It was needed to limit Tigris River flooding downstream in Mosul and Baghdad, Iraq's second- and first-largest cities, respectively.

Saddam constructed it in the middle of the Iran-Iran War to show how prosperous things remained despite the war, but in actuality the dam was built quickly and cheaply.

Before construction engineers suggested heavy foundation grouting and preparation before building the dam as it sat on soluble gypsum. But political pressure meant the dam would proceed without sufficient grouting. Instead a grouting curtain nearly 500 ft. below the dam would compensate for the limited 82 ft. of grouting in the foundation.

Grouting curtains are regularly used to pump a bentonite, cement, water and air slurry below the dam to prevent upward pressure on the underside of the dam from underground seepage. The heavily gypsum bedrock meant that water seepage under the dam was inevitable and considerable maintenance would be needed to keep the dam safe. Insufficient grouting caused the uplift that toppled the St. Francis Dam in California in 1928, which killed 431 people.

Over the years 50,000 tonnes of grout material have been pumped continuously below the Mosul Dam by 300 workers on 24/7 shifts. When American military reached the dam in 2003, engineers found that the dam was dangerously close to failing from underground seepage. Due to the invasion, resources were routed away from the dam's maintenance and workers began quitting after not getting paid. The dam deteriorated to the point where the U.S. Army Corps of Engineers spent $27 million in 2007 for an emergency short-term solution.

Then in 2014, terrorist group ISIS/ISIL captured the dam for several days, but was pushed back. Had the radicals captured the dam for a longer period, it's entirely likely the dam would have already collapsed. Nonetheless, machinery that ISIS captured and workers it drove away have yet to return, meaning that for more than year and a half the dam has not had the equipment and just a 1/10 of the workforce needed to keep it stable..

Instead, millions of individuals live with the worry that the dam burst is imminent, right as spring runoff begins to occur. Estimates believe Mosul would be submerged in 65 ft. of water within four hours, and Baghdad in 15 ft. of water within 48 hours, if the dam were to break. Death toll estimates range from 500,000 to 1.5 million.

The situation is so dire that the U.S. Government issued a second advisory against traveling in the Tigris valley, on top of the general "you probably don't want to go Iraq" blanket advisory.

This blog might be posted in the Oh CR4p! section, but it doesn't have to be. The Iraqi government recently reached an agreement with an Italian firm to fix the dam, hopefully before it's too late.

12 comments; last comment on 03/31/2016
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Why We Need Others To Catch Our Typos

Posted September 04, 2015 7:00 AM by cheme_wordsmithy

If yvo'ue raed something aoubt how the brian wrkos you may konw why you can raed tihs snetecne whiuott mcuh tbruloe.

I remember the first time I saw something like the mess you see above, and how amazed I was that I could read it so easily. What intrigued me more though was the concept that our brains can make the necessary assumptions to read words in bulk rather than through individual letter order. As long as all the letters are there and the first and last letters are in the right spot, our brains usually have no trouble piecing things together. This is because the brain is allowing itself to take shortcuts in order to complete the more complex goal in reading --> extracting meaning.

The brain actually does a lot of simplifying to help manage all that it does. Consider the fact that even when you are doing a brainless activity that requires no real thinking (e.g. fishing) your brain is busy processing everything you receive from your five senses, and simultaneously managing both passive and active motor functions in your body. When we add thinking to the mix, the brain looks for ways to simplify and generalize easy/component tasks in order to free up brain power. Taking the example above, the mind takes shortcuts on how we read individual words in order to focus on the harder task of pulling meaning out of a sentence or paragraph (aka "reading comprehension").

There is another shortcut our brains take when we read, and it actually inhibits our ability to proofread. When we read, our brains are pulling sensory information from our eyes (the words) and combining that with our prior knowledge to extract meaning and understanding. When we read our own work, we already know the meaning we want to convey, and we expect it to be there. This expectation makes it easy for us to miss things that would be obvious to others, because our brains are filling in the gaps for us. It's typically also this reason why we make typos in the first place. There have been many times where (in a draft) I've completely left out entire words or sentences about certain points, and not seen them during my review. In my head I read them, but I had not written them on the page.

Studies on "change blindness" show another way that our brains make compromises in order to focus. In this experiment at Harvard University, test subjects are asked by a man behind a desk to fill out a consent form for an experiment. When they complete the form, the man behind the desk ducks down to file it, and a completely different person stands up to tell them to go into the next room. About 75% of the people in the test don't notice this change, presumably because the brain is making assumptions for the things that it is not focusing on. Pretty amazing and yet pretty scary - it makes me wonder what kinds of changes I've missed this way in the past.

Even as we continue to push the envelope on human understanding and knowledge, it's important to remember that our minds are limited and that we will sometimes miss things and make obvious mistakes. Most of the time, though we would rather go it alone, there is no substitute for having someone else review and check our work.


19 comments; last comment on 07/18/2016
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