Replies to This Discussion

Permalink Reply by FireGuru on September 11, 2008 at 5:02am

I have an infamous risk in my patch - Cromwell Weir, Newark, Nottinghamshire, UK.

Due to it's design (fault) it is a huge keeper with a boil line some 3 - 4 metres from the drop.

It's fame comes from taking the lives of 10 paratroopers of a team of 11 in 1975. It also took the lives of two adult cruise boaters when their cruiser went over it and got stuck in '79. Nasty!

We would attempt a rescue but from well behind the boil line. It is probably body recovery by the time we arrive as it is 9 miles from the station and we would be calling in the Royal Airforce Helo in.

Any other ideas on how to tackle a rescue here? Is there a craft that could get to the drop?

Permalink Reply by Frederik Munnik on November 27, 2008 at 3:40am

Yip, that's a nasty one. We have something simular, though not quite that size. Our drop is higher, about 3m thus a very deep outwash. We use either tethered swimmers or a 2 man inflatible boat, river rafting style, that we run off a pulley system. The later is connected to a highline that is rigged above the wall. Don't know how it will work in your scenario as the distance between the river banks appears to be substancial.

Permalink Reply by walter augustine on February 8, 2009 at 1:40pm

you may want to check out a comany called creature craft, they make a rescue boat that would be good for your situation or a rescue bobber that I made with a company called Demaree Inflatible boats in Maryland USA

Permalink Reply by FireGuru on February 9, 2009 at 5:44pm

Thanks for the suggestion, I have seen these in operation on 'youtube'. The question with this one is because the weir has such a large airated distance to the boil line (upto 4mtrs in places) would this type of craft still be bouyant enough? (not that the brigade would contemplate letting us test it anyway). One thing I have found out since is that the weir disappears when in flood or after heavy rainfall against an incomming tide. Also further up stream is a major sluice which can be opened, maybe the answer is bigger than trying to attempt a rescue against the keeper but rather to raise the level of water over the height of the weir and then treat as a conventional swift water rescue? Maybe a structure that can be put over the shallows on the tidal side to create effectively a large mill pond? Major work involved probably .............! Hmmmmm.

Permalink Reply by FireGuru on February 9, 2009 at 5:49pm

In the past things similar have been tried.. At one point we had a cartridge gun type harpoon that would fire a guide rope across to the other shore so that we could set up ropework / tyralene. Most times this wasn't powerful enough to be accurate so was given up upon.

Permalink Reply by Ben Waller on February 9, 2009 at 6:00pm

If you're going to apply an engineering solution to the weir, the best option might to fill the downstream side with a boulder field and change the weir into a rapid.

Another option is to breach the dam in the center, creating a mid-river escape point for anyone caught in the boil.

The best way to rescue people from low-head dams is to eliminate the hydraulic prior to the next victim getting recirculated.

Permalink Reply by FireGuru on February 10, 2009 at 7:44am

Another option is to breach the dam in the center, creating a mid-river escape point for anyone caught in the boil.

Could this be done by floating an iron /steel v-shaped device (like a bow of a ship - see pic) downstream to the head of the weir changing the hydaulic to eject the casualty mid river? And do you think that this would need to be mechanically adjusted or would the forces involved be managable manually with a team of blokes?

Attachments:

• weir.jpg, 21 KB

Permalink Reply by walter augustine on February 12, 2009 at 1:20pm

I am the rescue school coordinator and I have a mam made river that I teach swr on I can change my features and create low heads and I had the owner of creature craft on the course and he just played and played on the low head. i guess the only way ot find out is testing ( good luck with your higher ups letting this happen) but I think it would work. This is why I made the Bobber to keep people out

Permalink Reply by Ben Waller on April 22, 2009 at 10:37pm

That is a creative idea, but I'm not sure that it might not create more problems than the ones it would potentially solve.

The problem with a the weir hydraulic is the boil below the dam, not the water's entrance route above it. The device you show would likely have minimal effect above the dam - it would probably just be lodged above the dam. The water would flow around it and re-create the boil. If the device wasn't really tall compared to the upstream dam height, it could submerge and the water might just flow over it.

It is unlikely that breaching the dam during a rescue would be effective. It would take either explosives or a very massive force to breach the weir, particularly the ferroconcrete weirs found in many parts of the U.S. The explosion would likely kill the victim(s). A massive non-explosive force could injure or kill the victim with projectiles or create an entrapment hazard that could pin the victim underwater prior to flushing out of the hydraulic.

Another potential problem is that some weirs are so wide that the victim might not be able to reach the breach.

The best way to take care of weirs is prevention, not response.

Permalink Reply by Ben Waller on April 22, 2009 at 10:38pm

Walter, how big is the low head at your artificial river? How wide, how deep, and what is the depth and pitch of the dam feature?

Permalink Reply by Bull on June 25, 2009 at 2:37pm

That is a bad situation, The thing is you want to rescue without having to be rescued yourself. If you cant do it safely sometimes nothing is the answer. It sounds cold but losing more especially your own could be the alternative. So remember to evaluate the whole picture.

Permalink Reply by Ben Waller on January 20, 2010 at 9:21pm

Photos of the bobber?