News Wire had a story about our Santa Margarita Bridge project on the old Santa Fe line north of Oceanside, with the bad news that much of the deck will have to be replaced because of failed wooden forms, due, they say, to "marine worms" infesting the wood and causing it to fail before setting./curing was complete.
LA Times story pretty much duplicates the News Wire story. I don't think any of the reports caught the irony of blaming things on "marine worms" considering that the bridge is right next to Camp Pendleton.
My final thought is that somewhere in this project, someone was not paying attention. Just a thought.
Was the timber untreated? Curious (and I know the line too well. Laid steel over that rascal's predecessor with the Navajos. Santa Fe had no problems there.)
Look up TEREDO WORMS, sometimes called "termites of the sea" you do NOT want these things anywhere near a piece of wood and water.
Well guess the contractor will use steel pilings and forms this time ?
http://en.wikipedia.org/wiki/Shipworm#Engineering_concerns
Ouch ! they are nasty little buggers. No mention they are repulsed by treated lumber ?
mudchickenWas the timber untreated?
Very few treatments (that are politically acceptable nowadays!) work on teredo spp. The worm does not actually 'eat' the wood, he just abrades it and passes it through, and so even creosote or copper salts won't really stop the problem.
Depriving the adjacent water of oxygen, or otherwise changing its character, can work -- these things die nearly as easily as termites do. Problem is that when you 'protect' the water quality, it's like putting up the free-lunch signs.
I'd break out the Nereis fucata (or a similar known-effective predator). Or, as mentioned, go directly to metallic or composite formwork. It would be interesting to see whether some flavor of fiberglass with embedded abrasive particles would work as a resistant facing -- the problem is that the least little tiny hole in the covering is relatively quickly found and exploited... and if this causes the coating to dislodge or spall... well...
ATSF had started to use steel piling coated with 2" of composite plastic from 5' above the water line down.
(piling material made in San Bernardino and wound onto the piling)....They were also experimenting with polymer coated timber piles.
I've been passing by that bridge almost daily for the last five months, usually on 599/565 & 582, and had wondered why construction appeared to be stalled. Th crews have pretty much demo'ed the decking and now working on the upper part of the piers.
The new concrete bridge is in place and one track over the bridge is mostly in place.
Up here, the Pacific Northwest Traction Co had a 4 mile trestle over Chuckanut Bay. This was repeatedly attacked by these shipworms. Their solution was to encase the piers in concrete, which slowed the problem but did not eliminate it.
The moral of the story is if you're building in a harsh marine environment don't cheap out, spend the money, do it right the first time.
Look at Henry Morton Flagler's bridges on the old Florida East Coast Key West extension. 100 years old, and they're still there. The hurricane of 1935 wiped out the railroad on the islands, the bridges held fast.
From 3,000+miles away, I'm skeptical that the worms caused the concrete's forms and their supports - "shoring" is the technical term - to deteriorate faster than the concrete attained the required strength; usually, 28 days after pouring is specified. More likely, IMHO, is that either the shoring design was inadequate (happens occasionally for temporary structures like that), and/ or the base of the shoring settled/ subsided into the muck a little bit more than anticipated because of the tremendous added weight of the concrete or scouring from eaves, tides, other water movements, etc.
- Paul North.
Perhaps the forms and shoring was put up significantly before they started the pour?
Paul_D_North_Jr From 3,000+miles away, I'm skeptical that the worms caused the concrete's forms and their supports - "shoring" is the technical term - to deteriorate faster than the concrete attained the required strength; usually, 28 days after pouring is specified.
From 3,000+miles away, I'm skeptical that the worms caused the concrete's forms and their supports - "shoring" is the technical term - to deteriorate faster than the concrete attained the required strength; usually, 28 days after pouring is specified.
Paul,
Today's San Diego Union-Tribune had an article on Flatiron Construction Co, the outfit working on the bridge. The article mentioned that the collapse of the shoring was investigated and found to the satisfaction of teh customer to be due to marine worms. Based on a comment about construction being slowed down by flooding a couple of year earlier, it may have been that the wood used for shoring spent was exposed to the elements for way too long of a time before being used.
The article said that the bridge should be open on the 18th, so I may one more week of riding through the ~100 year old steel truss bridge.
- Erik
Already on Wednesday's News Wire, but for those non-subscribers, the NCTD release on the bridge work coming up this weekend and halting of all rail traffic at the bridge.
And a follow-up to Chuck's post is that the track on the new bridge has been put into service this morning, replacing the nearly century old steel truss. Rode across the old bridge for the last time on Thursday, and rode across the new bridge this morning.
Next step appears to be adding the second track.
Interesting that on Saturday the 16th, I was within earshot of the Washington Street grade crossing at lunch time and distinctly heard a locomotive horn at about the time a train usually comes through, which was somewhat unexpected, given the announced annulments of all traffic..
Not at all sure what that was all about because I did not have a visual on the crossing or track. I guess it will remain a puzzle.
Oddly enough, I was just reading an old magazine online-possibly Railway Engineering but don't quote me-(Google your searches under the "Books" option and you find all sorts of interesting stuff!) and there was an article about FEC's experience with marine worms damaging piling and various experiments to mitigate the problem. Among the ideas tried were creosote treatment (generally accepted as the best) with sufficient napthalene, tarred burlap wound around the pile (kept coming loose as it was forced into the river bed), metallic sheathing (easily damaged) and tile or concrete casings tight around the pile (easily damaged when driving if applied beforehand or undermined by scour if applied afterward).An interesting idea suggested was to surround each pile with a metal, tile or concrete tube, generally made up of a series of rings, that fit loosely enough to settle into the river bed if there was scouring around the base of the pile. There was allowed a sufficient gap on the inside that would be filled with loose sand. Apparently that would discourage infestation through any hole or gap in the casing and would, by simply examining the level of sand from the top, warn of any heavy scour beneath, or major damage to, the protective casing.
Kevin, I think Mr. Flagler's Florida East Coast probably forgot more about building in a harsh marine tropical environment than the rest of the world will ever know.
As of this morning, several hundred feet of track south of the old trestle and truss bridge have been taken up with further track removal still going on. I suspect the old truss bridge will not be here much longer, a bit sad as the "Ship and travel Santa Fe" is still barely visible.
The rack over the new bridge appears to be very roughly 5 feet higher than the old track. The berm south of the new bridge is not wide enough to support two tracks, mainly because widening would encroach on the old track. I suspect work will start soon to widen the berm to allow for double tracking as part of the program of double tracking the line through Camp Pendelton.
erikem ...I suspect the old truss bridge will not be here much longer, a bit sad as the "Ship and travel Santa Fe" is still barely visible.
...I suspect the old truss bridge will not be here much longer, a bit sad as the "Ship and travel Santa Fe" is still barely visible.
This afternoon I drove by there on southbound I-5 and see that about half of the truss of the old bridge has been removed so far. Oh, well, I guess 98 good years were enough. Still, it's kind of sad to see an interesting structure I have been viewing for nearly sixty years finally become only a memory.
It's only a bit over 45 years for me and a bit sad for me. The saddest bit is the loss of the reference to the Santa Fe passenger service.
Concrete ties are in place for the second track on the north side of the new bridge. Grading work on the south side appears to be nearing completion. Saw a bunch of stacks of concrete ties on the south side as well. Also saw more preparations for the second track near the wye for the Pendleton branch.
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