NEW Key Bridge Sonar Shows True Collapse Damage

[@jeffostroff]

🎥 Watch Next: 🎥 FIU Bridge Collapse: WORST Engineering Blunders Ever: kzbin.info/www/bejne/iISYiautgK6rY7c 🎥 SCARY Crane Collapse Fell Off Tower, Fort Lauderdale, FL kzbin.info/www/bejne/d16xZJl7htydrdE 🎥 Titan Sub NEW Air Force Audio: An SOS For Help? kzbin.info/www/bejne/Z3qtioSmi7yMZqMsi=dOwyBsYNhW3MjR_w 🎥 LEAKED Titan Sub Transcript Shows Crew In Battle For Lives: kzbin.info/www/bejne/anXNaXyAl7VnZ8U

[@JosephOlson-ld2td]

NOAA Navigation Charts for Baltimore show soundings (depth) for the whole bay....

[@JosephOlson-ld2td]

Dali draft is 49 feet...hit 30 foot deep channel wall,

[@bungalowbill3409]

The reason they're removing all that cargo from the front of that ship is so it gets ass heavy and they can just tug it out...

[@debcarpenter8519]

Jeff, your new video just popped up on my feed. I'm glad it did! Your coverage of the bridge collapse is excellent! Living in Colorado, I haven't seen any more extended coverage of the work they are doing. Thank you for keeping all of us informed!!

[@tomlong736]

Two things. They can’t dredge too close to the pier footing as it could cause the footing to scour. Also, she was probably light boat to safely clear the bottom. Once she was clear and in open water, they would add ballast water making her more stable in more rough sea conditions.

[@GordonStevens72]

Thank YOU, Jeff! You always put in a tremendous amount of effort with research, parsing through vast amounts of data points and somehow make the time to present it in a clear, concise and transparent manner. Keep up the excellent work.

[@zackjay71]

Unloading the cargo should raise the draft considerably. Probably reduce it about 30-40% putting that draft in the 30 ft realm.

[@tomlong736]

I’m an almost 81 year old retired guy that as part of what I did involved inspecting both highway and railroad bridge sub structures. I’ve also been involved in cleaning up some messes so am fascinated by this incident.

[@stevejette2329]

tom - YES !! As a once journeyman ironworker who worked on many bridges and a former coxswain for the US Coast Guard, this tragedy is astounding. And Jeff's presentation is so very good !!

[@fridaycaliforniaa236]

You're my « go to » *channel* (pun intended) when it comes to engineering disasters. I love this =)

[@munzy5865]

Just a pleasure to get your opinion & diagnosis on what's happening, makes more sense and much more informative than what were getting from any MSM outlets on this recovery and salvage operation in Baltimore. Exceptional work Jeff. Thanks

[@colleenkearns1479]

I just want to say that this is one incredibly awesome video. You really show the points that I've been wondering about with this shop listing and the depths of water and the ship. Very awesome video. Thank you for making and sharing with us 😊😊😊

[@johntankson]

Thanks Jeff, your work and information on this tragedy is greatly appreciated sir. No smoke and mirrors, just straight and truthful reporting.

[@uther10]

Dayum, great catch Jeff. Thank you for the great explanation and the graphics helped a ton!

[@mrmysterious]

Yours have been the most informative videos on the Tube.

[@scottperine8027]

You have a excellent channel and tell it like it is,I really appreciate your knowledge and insight covering this disaster,I’m a Maryland native and my heart continues to bleed for the loss of lives and our so very loved and beautiful bridge.

[@catalinawoody6954]

You give the best updates. Thank you Jeff!

[@sharonmansfield3053]

Thank you Jeff, this is very interesting to see the sonar. They are working fast.

[@molie7712]

Sonar, not solar, it's in the title and the thumbnail.

[@sharonmansfield3053]

@@molie7712Oops, I guess at 89, still make mistakes!

[@Wynken_Blynken_and_Nod]

Excellent coverage of this catastrophic event. Thank you.

[@edl653]

I have been watching you for 2 years now. For an engineer on YT, 467k subs is a very good number. 🤓

[@jeffostroff]

Thanks Ed!

[@coryarmstrong1025]

Yeah and that was two days ago He's up to 469k now. Which is awesome.

[@martincraven3835]

Good morning Jeff, your analytical videos are superb, unbiased and well presented facts, they certainly are progressing well with the bridge clear up, I am also deeply respectful that you recognise that somebodies love ones are still trapped in the debris. I need to add that I am so fascinated by how logical and expedient the the whole of the Baltimore team are performing, having worked alongside the American Civilian and Military in my working career, I am not at all amazed by the great progress made by the salvage effort. I can definitely say that the manner in which the work is progressing is down to great people on the ground. Your countries response to this sad event has overwhelmed me. IMHO my guess is they will use Air bags to re-float the front end of the Dali, once they have removed the majority of the debris and made some buoyancy calculations, the Airbags could be used for lifting the bow and Tugs could be utilised at high tide to remove the Dali to a safe area where she can be unloaded without hindrance to other shipping traffic. Airbags are a very controllable way of lifting Thousands of tons of material in water. Of course for all of this to happen the ship has to be structurally sound to move, but from the video footage you have screened it all looks very much under control.

[@jsmcguireIII]

Slackening the lashing rods on those leaning containers has to be nerve-racking. Those Longshoremen are studs. I pray they stay safe!

[@Jim-tn3vq]

Love your great content and analyses. I look every day for new photos. Thank you

[@jeffostroff]

Glad you like them!

[@hornesbee]

I found your channel when that small sub imploded just above the Titanic. Really learned a lot from that coverage you did there, and now this... Excellent work showing us "Laymen" just what's going on and what "Might" be in terms and Excellent CAD pictorial displays. Thank you ! Subbed to your channel. James

[@basilfoster5245]

I suggest that the slight deviation to the left just prior to impact was the result of the Dali grounding outside of the channel and being deflected to port. However, the momentum of that behemoth partially overcame the drag and kept it moving ahead, even after impact.

[@Random_Routine_]

Clear, Reasoned, Rational, Evidence based - solid work. The best piece of public facing material I have seen relating to this disaster so far. Thankyou for producing this.

[@charlesreediii5083]

Hi Jeff, Locally we are aware that the Dali is indeed beached. There are plans inplace to dredge around the ship, which wont occur until most of the debri is removed. The plan for Dali, is to move her to either Seagirt, or DMT for a complete inspection. We are aware the bow of the ship has been breached and flooded. This contingency is also being planned for on sight.

[@irmadupr]

Will it sink if they move it.

[@kimmacdonald1678]

@@irmadupr if it didn't sink yet then no it wont later

[@pamhodges5662]

Have they figured out why the ship lost power? Will it have to be towed? Thanks!

[@chucksmalfus9623]

@@kimmacdonald1678. She can’t sink while most of her is sitting on the bottom.

[@timothylegg]

Take a moment to think of the crew on board that have to live there because they don't have VISAs to enter the US. If that boat rolls over, they are legally forced to ride that ride.

[@wyomingadventures]

Thank you Jeff. Your videos are very helpful and informative.

[@Sig_P229]

It’s wild to think that sonar image has bodies hidden in it somewhere. Sad stuff

[@nigelh3253]

It is sad stuff. Innocent workers killed in this tragedy. It's good that the NTSB are doing a thorough investigation. Because of the deaths of the road crew, there needs to be some criminal cases launched. All this 'act of god' stuff from the companies and insurers is just hocus pocus. Maybe the crew will be found not guilty, but the loss of life is quite terrible.

[@jeffostroff]

It is indeed a sobering thought to consider what lies beneath the surface of those sonar images.

[@Sig_P229]

@@nigelh3253 the word is it’s an ongoing problem with bad fuel. It really is no one’s fault. Think of it like condensation building up in your fuel tank if you don’t drive your car for a few days.

[@carmisti]

​@@jeffostroffany way you can start doing uploads in 4k? It would be great for your content, specifically. I'm a big fan! Thank you!

[@fazzmohd9388]

it is a common problem in the shipping industries nowdays​@@Sig_P229

[@heartobefelt]

You will find there will be 2 difficult areas in this salvage. When the center portion of the bridge collapsed the concrete decking broke up and slid down the slope each side and collected in the ~20' deep mess in the center of the Federal Channel as shown in the Sonar images , The missing vehicle will be under the hundreds of tonnes of concrete chunks. Removal of the bridge structure above water will be the easiest part of the whole operation. Once the missing victims are found and removed , The very difficult job remaining is to untangle the steelwork and concrete decking sitting on the seabed in the middle of the channel , this job will be painstakingly slow , possibly 20 times or 30 times longer than the removal of the structure visible above waterline. The other difficult part will be cutting and removing the structures sitting on the bow of the ship. When they schedule the cutting sequence of that piece of bridge , If they get it wrong the remnant sitting partially submerged could swing down and perforate the ships hull below waterline , so they have to cut in just the right spot so the cranes can support the weight of whats on the bow while still creating a safe zone to protect the hull from damage. Notice they didnt do any work yet on the bow area ? They are probably waiting for two bigger cranes to arrive , ideally they need two cranes of 8000 tonne or better so one crane can sit each side of the cut zone to support both halves .

[@terry94131]

As always, a fine report! Thank you Jeff.

[@melissaosborne3437]

Prayers to the families of these construction workers..May God Bless you all.

[@GlennSelan]

Excellent detail about what is going on with the clean up operations . thank you

[@Ruthhql320]

Thank Jeff! Always informative!

[@jeffostroff]

Thanks for watching!

[@timtmt522]

FYI there is a high-pressure gas main directly under the Dali, in the first four days the gas utility's depressurized and drained the line to make it safer. They already stated then CANNOT drag it our it would possibly destroy this line sitting very close buried in the muck directly under the Dali. All this was stated in a previous news brief.

[@countrytxrose]

I'm so glad I found your videos today they are VERY INTERESTING. I like the way you explain things in simple words with out saying all the tech words. THANK YOU SIR JOB WELL DONE, KEEP UP THE GREAT WORK.

[@gtaelement137]

Hello 👋 Jeff thank you so much information the pictures are very helpful nice work 💯👍👍👍

[@wirelesmike73]

12:59 The red container you put your cursor on is actually 10' high, the grey ones to the right of that marked "MAERSK" are 8-footers. They have 8' and 10' containers stacked all over each other up and down that ship.

[@rickymeadows5176]

If you ever watched the 3-part doc. here on youtube of the Pearl Harbor selvedge & channel clearing operation. Those Navy engineers are awesome at their jobs and that was back in the days before they had the use of the modern technologies & simulators they have at their disposal today.

[@coryarmstrong1025]

I have learned more about this incident from watching you than I've learned anywhere else. Thanks for explaining things for us non-engineers 🤣 no but really I do appreciate you.

[@DavidShook-p9h]

Excellent job explaining this disaster

[@Sig_P229]

Appreciate all your efforts 👍🏻

[@jeffostroff]

It's my pleasure

[@TnGaRealtor]

Great video! Very visually informative!

[@tomchastain1754]

Great insightful videos! I get my news updates from you.

[@1954diverdave]

My question /comment has to do with Dali. If you notice., indicated by the water line painted on ship, I don't think the ship is at it's maximum draft. Usually a ship would have empty balast tanks in shallow water , so it's draft would be far less. It looks like only the bow, being pushed down by the bridge structure resting on the Dali, would be at the depth of 49 ft. It's my understanding that the balast tanks are usually not filled until a vessel reaches the ocean. Then the tanks are filled to increase the vessels stability.

[@yankeexpress]

You are correct that Dali is Not at it’s maximum draft but your other speculation is incorrect. As a containership stability officer (Chief Mate and Master - retired) vessel load plans and cargo weights are generated ahead of loading by shoreside cargo planners and suggested ballast plans are emailed to the ship while still at sea prior to entering port so that sea water ballast and fuel can be pre-planned so that no harbor water is loaded or discharged in port (against the law). Ballast water can be pumped around the ship internally up/down, port/starboard, fore/aft to keep a slight aft draft and even list . Too much stability is nearly as bad as not enough stability because the vessel roll period can be to quick which can create snap rolling at sea which can cause cargo to break loose. The Dali was ballasted for sea before the mishap. After the mishap, ballast may have been shifted internally. The red/blue paint interface line is not a reliable measure. Instead read the forward draft, aft draft and midship draft to get a true state of Dali situation.

[@uncleelias]

I think you are correct in that the ship did run aground as well as it is being weighed down. There is supposed to be some flooding in two compartments, but Sal from What is Going on With Shipping didn't have more information when I heard him mention it and he didn' think it was serious. When Ever Forward ran aground in that channel they had to remove 500 containers. I'm guessing they will probably do the same with Dali too. Even if it isn't stuck, like you pointed out, they have to be careful with the balance of the ship since it's canted to the left. Removing weight off the top will lower the center of gravity. Especially if they need to dump ballast for the assumed re-float.

[@YvonnePhillips-zn4pw]

The EVERGREEN ran aground in the SUEZ CANAL.

[@davebollmann5292]

Great video and analysis, tnx jeff

[@lia-liz2012]

Fascinating Jeff!!!❤😊

[@The.Real.Timmii]

amazing insight , thank you!

[@Shortstuff841]

Awesome video, loved the details 👍

[@suzylarry1]

I agree after watching the bridge and the lights of construction vehicles moving towards the failure of the sections . God rest their soles .

[@molie7712]

Keeping us educated like no other! Thank you, Jeff!

[@ibbylancaster8981]

Jeff, isn’t there supposed to be a gas line that crosses somewhere along in there as well? You’ve done a pretty great job of keeping fresh information out there. I keep an eye on a couple of other channels as well as yours to see what’s up day to day. I have a feeling that they’re probably going to unload a bunch of containers off that ship before they get it to move.

[@jeffostroff]

They said they were capped off and an inert gas was pumped in so they are on top of the gas situation

[@allangibson8494]

The gas line is just to the south east of the bridge under the Dali’s bow.

[@melissatwitchell9796]

You said, "moving like gang busters!" I haven't heard that exclamation in a long time! As always...SO impressed by your thoughts!

[@egorman2979]

One of the complications of locating the remaining construction crew and vehicles is that the containers that dumped may have also contained vehicles. Baltimore is the busiest port for automotive impots and exports.

[@vintagelady1]

Awesome graphics that really illustrate the issues here. Respect to the workers who died & condolences to their families---they were everyday heroes, just doing their job to keep things moving, until this disaster.

[@glenwest6079]

Great information Jeff

[@chris_hisss]

Yeah I agree, it has to at least be in part run aground. The front sides are angled though to a point, it has that round appendage at the bottom of the v, and then slowly tapers back and then widens into the V that you show at the midships cross section at the deepest point, which that is the 50 feet and it goes up from there, and is still angled so while it is beached, it shouldn't be too hard for tugs to pull it off that shelf, especially once all the weight is off her. The may pull all the weight off considering they may not be sure if the hull was punctured, which could be hidden under it on the shelf mud and would start filling potentially after they pull it off. That may not be the case if they can see everything under the floors but that remains to be seen. Nice picks and updates here Jeff! Thanks!

[@gunsnbutter410]

great work very detailed

[@sixstring007]

Your graphics provide a very plausible explanation for what the early video shows of the Dali striking the pier; that is, why did the Dali appear to turn further to starboard in the direction of the pier? This has prompted conspiracy theories. But, as the Dali contacted the channel on its starboard side, the drag on that side would have caused it to pivot even more to starboard, giving the above-water appearance of actually turning in that direction. Of course, the final NTSB report will ultimately provide the info we’ve all wanted to know, but this video provides some nice, level-headed analysis.

[@abbylynn8872]

Hey Jeff, would you consider doing a video on how to reseach our local ports and how they operate. Like where and what to research. On the Washington coastline we have lots of ports. This accident has really got me thinking about how tig service works for the posts. Are our non floating bridges do they have bumpers around the pillars. We've had a few ferry and dock accidents and groundings. I'd like to learn more about the shipping lanes and the depth of the channels here in the Puget Sound. Thanks for considering. Love your channel🌸🌸🌸💕

[@jackperson3626]

Thanks!

[@lloydprunier4415]

Hoping that when they get the bridge off the bow the ship will rise up if they pump out the flooded compartments. Compared to some of the other ship groundings this one is not too far into shallower water because the bridge pylon stopped it. It is rather frustrating to see the protective fender systems around the power line towers. Maybe if the bridge pylons had something like that on a larger scale this wouldn't have been as bad as it is. Thanks for the great pics of the wreckage.

[@artistjoh]

Another reason they are removing containers from the front of the ship is because it is standard practice to load toxic and hazardous materials in this area, and if some containers do fall into the sea, toxicity problems in the water will potentially hamper diver operations. Hence removal of front-most containers. The dangerous cargo is always placed in this location for good reason. If fire breaks out in the containers you do not want it at the rear of the ship because it is above engtines and other criitical plant. If midships the fire is double the problem as it has to be fought from two sides. The front is the safest place to be fighting fires in hazardous materials. It is also part od the ship that gets maximum viewing from the bridge, so smoke etc are likely to be seen sooner in this area. However, this dangerous goods practice is also dangerous for workers clearing the bridge sections, especially using cutting torches close to hazzardous cargo. This is why they are going to the effort of unloading cargo the most difficult way - across the bridge sections to reach the front-most and most unstable containers.

[@lindap.p.1337]

Very clear Jeff, thank you! The guys on the containers make me really nervous. As they remove containers from the Dali, won't the ship come up somewhat?

[@ypaulbrown]

thank you , outstanding information.....

[@clay-tw5gc]

One thing to consider is that the wet mucky sand at the bottom creates a suction on the ship. This happened to a very large ship grounded in the Suez canal a few years ago. They were not able to pull the ship out due to the suction. If I remember correctly, they had to pump out a lot of sandy muck from around the bow of that ship before it could be moved. I apologize for not remembering the ship's name nor the exact year.

[@cedrictrounson8978]

thank you for your explanations, however the Dali had a draught of 12.2m (40feet) the 50 ft dredged depth allows for the all important u k c (under keel Clearance) the Dali does not draw 50 feet

[@rickkraemer5780]

We have sonar images that show the bow of the Dali is definitely resting in the mud (aground). I think we have to assume that the Dali must be either partially or fully unloaded to float it again, so the real question is, what's the draught of the Dali when it is empty?

[@MattBilliot]

I have read from different sources the MV Dali was not fully loaded and was also likely carrying a number of empty containers. The draft reported is the maximum draft and she is probably much less due to the actual load being less than capacity. I think the red paint corresponds with the maximum draft.

[@Paul_Wetor]

The visible bridge parts look deceptively easy to remove. Seeing all that mess under the water makes the task ahead more difficult, especially in murky water.

[@michaelt151]

As one commenter alluded to there is a gas line buried across the channel which has been purged with nitrogen. Of course when moving the Dali they want to avoid damaging that pipe. That could open up another whole can of worms. Though through the network of other pipes, they have been able to successfully bypass it.

[@tonymarks841]

Great presentation. Waves and splashing occurred just prior to pillar contact. Was that the result of the Dali beaching itself?

[@jsmcguireIII]

Most intermodal shipping containers come in two ISO standard sizes: 20'X8'x8.5' (~2 tons empty); 40'X8'X8.5' (~4 tons empty).

[@thomaslongshore1295]

Good informative video, thanks.

[@nathanaustin6988]

you're reading the chart wrong, the little squiggly line is a contour line at the thirty foot mark. the bow and most of the starboard side is probably in 30-35 feet of water.

[@kimberlyjohnson6352]

Tfs. What a great number if photos and the way you explain it ixx Acc excellent.

[@SpeedysWoodshop]

Awesome video...Thanks

[@peterpumkineater6872]

When the bridge is removed from bow, the ship might rise up after that weight is removed.

[@jimmyjames2022]

Really interesting summary of "DALI" channel issues. At Sal's channel he says the containers in the front (ahead of the bridge) are largely empty or with hazardous material drums (drums you can see on the NTSB GOV inspection videos). So your dishwasher is farther back.

[@V100-e5q]

I think the Dali cut into the mud aka beached. When the truss came down it was pushed further into the mud and the part in the channel was pushed further into the water creating the list. In order to get the ship out again I think they will remove many of the continers to make the bow section lighter. That way it will rise from the muck by its buoyancy. The remaining containers more aft of the ship will help to seesaw the stern further down and give lift to the bow. This is a delecate operation because there must not be too much of heavy load on the aft section and no load on the bow section. Otherwise the ship might break or get bent. So they have to remove containers in a way that all are taken away at the very front and gradually less when getting more to the stern. How the ship sits right now there will be strong suction forces from the mud. Just try to lift your feet at the beach if you have set them a few inches into mud (not just sand). That will take some effort. So the seeswa action will help to overcome the suction.

[@numbr6]

I wonder what kind of weird stresses that wreckage undergoes every 12 hour with incoming/outgoing tides? This is the ultimate in "un-Jenga": taking it apart without having anything falling had killing anyone or making the situation worse, if that were possible.

[@richardwoods143]

Great video!

[@pjford1118]

If it is just muck they will likely jet the mud. I worked on a large barge recovery. We broke several cables trying to tug it out of the sand, what we eventually did was tie the 2 tugs very close to the barge. Then we had them just run at 1/2 throttle. The prop wash jetted the sand out of our way

[@waynebrearley2288]

In some of the reports, the majority of the containers in the front of the ship are empty. This is why they look so crushed.

[@markknister6272]

Another great video - just the facts (and a little speculation 😄).

[@JStryker7]

It’s kinda interesting that the power line poles have better protection than the bridge did

[@adidas20zero]

I believe your 100% correct. I wondered what stopped the Dali from moving it is stuck in shallow water.

[@robertsanders6463]

Great Explanation!

[@exeterline1930]

Do you have a section drawing of the federal channel between the two piers? Did they designate a staging area on the shore to dismantle the pieces of the truss the cranes have moved, or are they transporting those large pieces likevthey cut them?

[@Antony..24]

Hey you do pretty good explaining what we cant see!!! Let us give OUR opinion!! You show us from your view!! We'll show you from OURS

[@AC_SLANGA]

7:03 This over head view makes it seem like they could almost fit 2 ships that size to the right of the impacted pillar that it struck. This was a very unique view but I just find it interesting the way it crashed was almost intentional? Also what did the crew say or speculate on what happened in those 28 mins from dock to bridge? Operating error or mechanical failure or any news on why?

[@brucehain]

Re. 12:50 - 13:08 How is it the anchors appear to be grounded (bottomed?) in front of the place where the ship stopped?!

[@vailewalders1395]

I'm wondering would they need to or is there a way to support the ship before they finish removing the truss and the rodway cause if they don't it would seem by the removal it would displace the ship redistributing its weight and position maybe pushing it down further into the muck and as you mentioned maybe roll over

[@rupe53]

A rollover is unlikely. The ship looks top heavy, but those stacks go many levels below the deck.

[@BIGV710]

it looks like the containers on the bow are empty as i have seen this in my home port in southampton england

[@SeanBZA]

They need to remove all the containers to reduce draft, then they can start to dewater the front compartments that are flooded, likely not going to get all the water out with likely popped hull plates, but at least half way with lots of big pumps will make it more amenable to being pulled out backwards, possibly even with the ship engine in reverse as well to apply power, as it likely is still out of the mud. Not going to be able to run main engine long, likely all the coolant ports are clogged with mud, but even a minute of full power might be enough to pull it out. Otherwise they have to bring a dredger in with suction and pull mud from the other side of the channel, and wait for a high tide, or a spring high, to do the refloat.

[@tonithomas393]

Non engineer here. Really enjoying your channel. You do a great job explaining things so that this non engineer can understand. Is the plan to completely unload the ship thus allowing it to float higher?

[@PaulSteMarie]

If they continue to offload containers, the ship should lift itself, either completely or removing a lot of weight holding it to the bottom. Plus, by strategically removing weight they can adjust the CG location and thus tilt it about somewhat delicately.

[@CarolMains-dy7zh]

Thanks

[@chucksmalfus9623]

Jeff any idea what the un loaded draft would be if they were able to unload it completely or even mostly.

[@mickeyfixsen7579]

Remember that max draft is with ship fully loaded, etc. Also remember that the propeller and rudder are lower than the keel. The ship is partially beached, but might not be that difficult to re-float and pull out when the time comes. Thanks for your information.

[@syx3s]

it's showing the depths at different points over the debris. the federal channel is 750 feet wide and 50 feet deep. it should be 50 feet deep almost the entire width of the span between the pillars. those depths are indicating the depth of the water above the debris.

[@tvcompany22]

Jeff, are any of the cranes (or a combination of their extraction properties) able to yank out the Dali from the mud without dredging??

[@donnadornbusch6738]

Great explanation

[@EngineerLewis]

Air bags are a good way to lift a body in water - have a look at how they removed the Evergreen vessel stuck in the Suez canal.

[@annbraden6628]

Great analysis Jeff, thank you! Might they remove more containers to unweight it a bit?

[@G6JPG]

Yes, the question (or at least one of many) is whether the Dali ran aground anyway, or only when 3-4000 tons of bridge fell on it. If the latter, there is presumably concern that once they remove a certain proportion of the bridge debris, it will pop up. (Though one of the posts here says the bow was breached and flooded, but that's not evident from the pictures.) If the former (or in general anyway), then presumably some experience can be used from the refloating of that ship which ran into the side of the Suez canal (blocking it!); that happened under power, but presumably there are sufficient parallels that some experience can be used.