METRO has a problem with transparancy, now that problem appears to be contagious. Tom Bazan, that intrepid Anti-METRO warrior, filed a TXPIA records request of all TxDOT records of inspections of the Pierce Elevated support structure where it goes over the Dangertrain Tracks in regard to galvanic corrosion of the rebar in the concrete pilings due to stray current coming from the trolley.
This is, as some of you may know, a very dangerous issue. Stray Current can cause massive corrosion damage in surrounding steel structures quite quickly. It essentially sets up an electroplating cell in reverse and blasts metal ions off unprotected metal out into the surrounding soil. Moisture and chlorides (salt) in the soil also contribute by making the soil more conductive.
Reinforced concrete is especially susceptible because steel corrosion products take up more space than the original steel, therefore those corrosion products act like a wedge and cause cracks to form in the concrete. Once cracks form and more moisture can get to the steel, the process accelerates. Once concrete is damaged this way, its repair is difficult or impossible.
Concrete is not waterproof, anyone who has ever lived up north and found water leaking into the basement knows this to be true. Concrete is porous. METRO and TxDOT claim that it is not.
TxDOT, instead of complying with the request, filed an appeal to the Attorney General’s office seeking to prevent disclosure based on what I feel is a mis-application of Federal Law. The law was intended to shield local and state agencies from lawsuits based on traffic safety studies that are mandated by Federal Law. Here they are using the law to hide their lack of interest in looking for Stray Current damage. You can read the OAG opinion here.
Ignoring Stray current problems among transit agencies is not a new problem. This site for instance pointed up the general feeling that if you don’t look for a problem, there must not be one. You’ll note that it is a little bit dated. There is a reason for that, the FTA stopped funding them when they became too critical of the lackadaisical attitude among transit agencies to the problem.
Remember a while back when Seimens refused to fix the automated track switches that were damaged and had to be operated manually because METRO installed them incorrectly? Here is an interesting quote from the article:
In a separate problem, Metro engineers say a small amount of "stray current" from the overhead wire that powers the trains is leaking into the ground at each switch location instead of flowing back through a rail to a power station. Metro says there is no danger, but a spokeswoman for CenterPoint Energy, which called the problem to Metro’s attention, said the current could eventually corrode the company’s underground gas and electric conduits. Current was also detected at "anchors" on each end of the MetroRail bridges over Buffalo Bayou and Brays Bayou. These are crossbars that keep the tracks from moving as the bridges expand and contract with temperature changes. The Stray Current problem also will have to be fixed, Wilson said, mainly by ensuring that the trouble spots are covered with nonconducting materials. No cost estimate has been made.
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More TOMBSTONE thinking….looks like METRO’s pre-construction studies might have some “shocking” omittions in its findings…
Does that really supprise anyone? I mean this is the same organization that had drivers in busses for 75 hrs a week and earning over $125,000 in a single year… Cannot manage staff levels, cannot manage to design something that really moves people, cannot manage finances, likes to build things that are neat to look at and fun to watch.
Add in no real accountability to the residents they are supposed to server and this is what you get.
Hmmm no purchase necassary. Considering how many people ride for "free" was that statement really necessary?
A quote from the American Ostrich Association that proves ostriches are more aware than METRO.
“Ostriches do NOT bury their heads in the sand. They NEVER hide because they are frightened.
This tale originates from the fact that the male ostrich will dig a large hole (up to 6 - 8 feet wide and 2 - 3 feet deep) in the sand for the nest / eggs. Predators cannot see the eggs across the countryside which gives the nest a bit of protection. The hen as well as the rooster take turns setting on the eggs and because of the indention in the ground, usually just blend into the horizon. All birds turn their eggs (with their beak) several times a day during the incubation period. From a distance it appears as though the bird has his/her head in the sand.
An ostrich’s first response to fear is to run. Not only do they not stay to protect the eggs, they attempt to detract a predator to follow them. Due to the fact that they can run sustained speeds of about forty miles per hour, most predators are quickly lost and the eggs are safe.”
The first Stray Current Consultant report cited the fact that METRO did not perform any initial baseline testing for “Stray Current!”
There is an update letter from last November which states the Consultants are stiemied by the “stray current” and must continue testing.
TXDOT returned all the stray current data delivered to their bridge engineer who is responsible for safety inspections, stating that since they did not generate the documents, they could not evaluate them.
Another example of the unelected and unaccountable bureaucrats wanting to ignore and avoid dealing with safety hazards when it concerns a “Sacret Cow.”
Squawk,
#3,
Wouldn’t it be amusing if METRO had originally projected the 20-millionth “Forced” rider was to have boarded at the Noth-bound tram platform during the morning commute?
I’m just disappointed that Metro feels like they have to mis-apply the law to avoid accountability. Don’t they realize that people are on to them?
But you see this is just an estimate since there are no fare boxes on the trains and it is all on the honor system.
I would be really funny if the 20millionth rider was someone who jumped on and had not paid. I can see it now.. the interview with one of the talking head tv reporters
Reporter: how does it feel to be the 20 millionth rider on Metro Rail?
Rider: Well great, but I have had to ride this because Metro stopped serving my neighborhood and I cannot afford a car.
Reporter: Well doesn’t the rail line provide you with a faster trip.
Rider: No I now have to walk 10 blocks to get a bus to get to the rail and that and the rail cost me more than my original bus route did.
Reporter: Oh, so how do you deal with this extra expense?
Rider: Oh’ I just never pay for the rail when ever I can get away with it. ( at this time 10 metro cops tackle the rider and haul him/her off for failing to pay)
Reporter: well there you have it folks, Metro is cracking down on the free rides again… reporting from the 20millionth rider ceremony, this is bubble headed reporter to blind to see what is really happening….
Note All characters are fiction, except the metro cops.
No, they are fiction too….=D
Hey Rorschach, did you see my soapbox moment with regards to your Legislative agenda, and what I would add?
Stray currents are dangerous. The real problem occurs when one potential has a path to ground through one path, and another potential has a different path to the same point.
The result is called “short circuit.” While this current increases, the heat increases until eventually, something catches fire. If things are as bad as this article presents, I would start expecting junction box and switch fires in the near future.
Didn’t we have one just the other week, when almost the entire toy train was shut down?
Wino, in this instance the problem is that some current is leaking to ground all along the tracks instead of staying in the rail and travelling all the way back to the power station’s ground. The rails are not properly insulated from the surrounding soil to prevent current leakage into the surrounding soil. I don’t think fires or shorts are the problem.
Another structure that is in danger are the twin St. Lukes Towers. When in the design phase, they were going to be 30 story buldings, but pre-leasing was so successful that the owner requested the architect add 5 more floors to each tower. This was after the foundation was already laid and construction was in progress. The architect recomputed the loads and found that although the safty margin was less, he could add the 5 additional floors. The owners asked if two additional floors (for a total of 37) could be added and was told no, the safty margin in the foundation for two more floors was insufficient. So 35 floors were at the safety limits of the foundation, but that was before they were corroded out from under the buildings. How much safety margin do we have now? Nobody knows. I suspect the next time a big hurricane blows through we will find out.
Let’s not forget the taxpayer-funded 14-story METRO Lee. P. Brown administration building. They failed to install any cathodic protection for this building’s foundation, yet it sits adjacent to the traks, and stray current from the Northbound platform must pass along, under and through the foundation so as to complete the circuit with the 8,000 amprer power supply which is situated under the Pierce Elevated, an expressway bridge that carries about 250K vehicles per day.
No problem Man, party on! It’s just taxpayer money and innocent lives at risk.
where’s spell-check when you need it?
Rorschach,
Those currents are called ground fault currents. Ground faults are currents going through the safety path to ground, rather than the intended return path to source.
The first ground fault is “free.” It causes no current to flow, just messes with your insulation. Once you get ground currents, then you have multiple paths from multiple sources. This causes ground loops, which cause increased heating and the corrosion problems that are mentioned.
I work with this stuff. Trust me, if you’re getting ground currents, for whatever reason, you have problems that need to be addressed.
Rorschah
Did you see their graphic on the front page announcing the “contest”?
http://www.ridemetro.org/index.asp
Metro’s server must be getting a DoD attack or something, the browser is timing out.
#18,
See? Wino told you about the dangers of ground loops.
Really though, that is a problem for us too. Particularly in communication cables where both ends of the shield are connected. If both ends of the shield are at exactly the same potential no problem. If they’re not, then current will naturally flow from the higher to the lower potential.
Once you get current flowing through your cable shield, it’s no longer effectively doing the job it’s designed to do: shunting electrical “noise” to ground. For this reason, cable shields should generally only be connected to ground at one end, unless it can be guaranteed that there is no possibility of the two ends being at different potentials.
#19 Dude
That is exactly the same concept, at much lower levels. Now, multiply the potential by factors of 1000 or more, and you see the problem. Not noise, but heat and dangerous potentials. Eventually, if things go badly enough, the ground conductor is going to corrode enough that no current will flow, and now you’ve got no ground (safety ground), and potential now collects where it isn’t supposed to.
Now, when someone touches the case, they get shocked. Perhaps enough current will flow through the person to kill them.
Metro has problems that MUST be addressed if they’ve got ground currents.
Wino, each tram platform is grounded, so no one should get a shock. The problem is that there is 750 VDC comming down from the catenary wire, through the equipment, and needs to return to the 8,000 ampere powere supply.
The track is supposed to have a maximum resistance of 250 ohms per 1,000 feet. All well and good in text book theory. The problem we have in Houston is lots of rain, generally often, high water table, some of the route in a 100-yr flood zone, and the soils contain a high percentage of total disolved solids (TDS) which is an electrolyte.
We all know things corrode real fast naturally, but when you kick it up several notches (Emeril), you have accellerated corrosion problems.
That includes concrete. The problem today was a concrete pipe had failed, that only makes my concern for the bridge foundations even greater.
Generally, one ampere, over one year, will dissolve 20 pounds of iron, 75 pounds of lead, 22 pounds of copper, or 6.5 pounds of aluminum. Each of the tram system substations provides about 8,000 amperes. Annually, electric current loss to ground of only 5% (400 amps) of the available substation power would dissolve up to 4 tons of steel, be it pipe, cable, or the foundation rebar from a building’s or expressway bridge overpass drilled footings! Corrosion resulting from stray currents during the tram’s normal operation can not be stopped!
“Corrosion resulting from stray currents during the tram’s normal operation can not be stopped!”
Yes, they can be stopped, but it would take insulation that doesn’t currently exist and that wouldn’t be easily retrofitted.
The five P’s of projects:
Proper
Planning
Prevents
Poor
Performance
Wino,
22,
I have to get my copy back of the 450+ page book, by NACE (located in Houston) from a local reporter, which covered 13 electrified tram (a/k/a light rail to the lemmings) systems operating in North America.
According to the corrosion engineeres, as well as some long-time industry folks I have corresponded with, stray current can not be stopped, only mitigated.
Remarkably, the best system implemented was under the World Trade Center, but the Islamofascists destroyed that section of the system on 9-11-01.
Wino, not in concrete, once the cracks start to open up, you can’t keep the water out which would corrode the rebar anyway. Also since most of the concrete is pre-stressed, the concrete starts to fail due to it’s internal stresses.
Gawd, I love engineers. You can fart through a screen door and they will tell you which hole it went through!
Seriously, you guys are way, way over my head!
Rorschach,
As you said in your original post and since then, it is the conductivity of the supporting concrete blocks under the conductive rails that is the problem. Insulate between the rails and ground and you’ve got a pretty good, low leakage system. Of course, that needs to be done before you turn it on.
Whatever the case, foresight would have saved a lot of money.
We can agree on the fact that the situation is bad, and needs action to improve or correct it. I’ve not disagreed with anything you’ve said, actually. I just think that the excessive ground current can be mitigated… whether that cost is too great can be decided once the exact cause is known.
For ONCE, I think a study is needed. The possibility of fire and shock is real if the electrical system corrodes. I do not doubt that the likelihood of mechanical failure is also increased by such corrosion and that other structures can be affected.