Bridge Cleaning - Suggestions Welcomed

I have a project that hopefully I can get some help brainstorming a bit. It is a timber truss bridge, PT doug fir with Alaskan cedar (non-treated) railings. I’m going to do some test spots first using house mix, citric, and sodium percarb. to start. I have 8, 10, and 5 gpm machines and a softwash setup. I’d like to just run the 8gpm and downstream if possible. The problem is, reaching the outside of the bridge. Weight restrictions will allow for only a small scissor or a tow-behind art. boom (which I think best bet). I’ve overthought this to death, just wondering if y’all may have ideas I have overlooked? Reaching from below isn’t an option. They want uniformity on the color, and the deck is being replaced.

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Whatever you do, be sure to charge a premium!
No way an articulating boom will work from inside the bridge - just not enough space maneuver it in between everything. If that’s a dirt/gravel road down below (I can’t tell, perhaps it’s a stream) then that would be your best bet.

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I’m gonna say this although you probably already know it if you are undertaking a project of this scope. Different woods take stains differently. As a contractor you already know to set expectations, so talk to them about the sun side vs. the shade side looking different when done. Even the same wood will take the stain differently depending on it’s age, density, and the cut of the wood. If you are taking this on, you have obviously stained things before. You know even a deck of all PT decking boards have a board or two that sometimes look completely different than the rest even though you did everything the same, but the customer might not understand this.

Please post pictures and note your methodology when you tackle this. I look forward to seeing your after pictures.

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Yes, we’ve already had some conversations. There will be no staining, however; cleaning only. I just need to figure out the best way to get to the outside … and if it is even prudent/reasonable.
Thanks for the input!

I admire you for even trying this. First thing I’d do is run by there and try a couple of those posts, timbers or whatever with your hw mix and see if that works. Once you determine what it’s going to take, then get back to us and we’ll figure out how to do safely.
I’m thinking you run a safety rope, attached every so often to the vertical posts all the way along. You, with a safety harness on, stand on that outside beam ( the ones posts sit on) snapped on to your safety rope, and just walk the outside shooting it. With your 8 you can do a pretty good ways in front of you, and just work your way along. If you’re into climbing or rappelling, it’s easy. If not, see if you have a shop that sells that stuff near you, or post locally for someone who does it, to get you the right equipment. You might be able to just lean over railing and get it, even then though you may want a safety rope.


Hmmm, I’ll have to noodle this idea for a bit. Pretty sure my insurance would drop me for even asking about coverage, my wife would for sure. Thanks for the idea, lemme’ see what I can figure out.

The bridge looks plenty sturdy to handle a small man lift. But that’s money you don’t want to spend. Interior side you could probably use a sturdy Baker scaffold. For stability you could clamp or strap off to the upper section of the bridge truss. The suggestion of repelling is very plausible. If you want to use ropes use top quality Equipment and be sure to locate a comfortable Bosun’s chair. West Marine supplies the industry down here. As far as moving laterally, I suggest a two pulley system mounted on a well anchored and drawn taught 3/8 steel cable. One for the lateral movement the other for travel up and. Suggest a good winch with remote control attached to a vehicle bumper. Rigorously examine your rigging or have someone with knowledge inspect. Check the nuts and bolts on the winch if you have to. Help on the ground would be nice but not completely required. You could and should already have a PFAS, Personal Fall Arrest System. Especially if you have been doing roofs and other similar locations. There are plenty on Amazon, but be sure it comes with a really good clevis hook. A short 10-ft length of rope, such as a dockline or lifting strap, can be supported over an upper beam. It’s quickly and easily moved. Small but strong anchors can also accomplish this. The cable supporting the Boson’s chair is impractical to attach the PFAS. Think about it? :thinking:. It only looks to me about a 40’ to 50’ drop. Remember it’s not the fall, but the stopping that hurts. Call the Aflac duck.
You will get good results if you start with your wider tips, lower pressure, on your test areas. If you need to check your test underneath you could use a mirror to view it under sunlight conditions. Be sure to get that is to be accomplished in writing, including technique and or chemicals.
Down here we have a lot of sun exposure as well as saltwater. In most cases Boat Owners will want their teak decking and gunnels cleaned thinking they will get brand new wood. Even though the wood is the same, the where, when and how conditions it was exposed needs to be considered. Areas that have high traffic, direct sunshine, nothing at all, may come out different than other areas. The redecking is questionable based on the pictures, but questions need to be asked and answered.
Be sure to send photos of the completed job. Maybe even a friend with a drone could get you started on your own YouTube channel.
By the time you read this you’ll probably have it done.


That’s a lot to chew on, thank you very much. Did some test spots, going to do some testing with a couple of lifts here soon. Don’t know about insurance coverage on the bosun’s chair, not to mention - that’s a new adventure for me. Not big on experimenting on such a large, high profile project … again, thank you. I’ll keep y’all posted.

Depending on other work, there’s always the viable option of walking away. No matter what you do, going to take some time that maybe could be spent better.

I agree. l’ve done work for this customer before - they will make it worth while, I just need to make sure we can produce. Thanks a lot for all of the input, doing some testing after the holiday with some lifts - I’ll keep y’all posted.