I have had a TXPIA request for the report, with no results.

Now there is a posting on the official METRO blog, but still no release of the full report of the minimal testing being reported.

METRO has not held a Corrosion Committee meeting in six months, and a few days of testing, under conditions likely staged for ideal results, may not be truly representative of the stray current leakage conditions the bridge foundations were subjected to for over 3.5 years of electrified tram operation.

The test dates for stray current leakage were March 5-10, 2007

There was no rain in Houston from February 24th through March 12th, so it seems suspicious that they choose a period of dry weather to test, likely after doing everything imaginable to minimize stray current prior to the tests. The test points were installed in late January, and they could have tested sooner, and over more than one "dry" period.  A few days of testing, under conditions likely staged for ideal results, may not be truly representative of the stray current leakage conditions the bridge foundations were subjected to for over 3.5 years of electrified tram operation.

Tom Bazan

Below are the NOAA Weather Statistics for Houston, TX

*********************

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6)

                                         STATION:   HOUSTON

                                         MONTH:     MARCH

                                         YEAR:      2007

                                         LATITUDE:   29 58 N

                                         LONGITUDE:  95 21 W

 TEMPERATURE IN F:       :PCPN:    SNOW:  WIND      :SUNSHINE: SKY     :PK WND

================================================================================

1   2   3   4   5  6A  6B    7    8   9   10  11  12  13   14  15   16   17  18

                                         AVG MX 2MIN

DY MAX MIN AVG DEP HDD CDD  WTR  SNW DPTH SPD SPD DIR MIN PSBL S-S WX    SPD DR

================================================================================

1  77  51  64   5   1   0 0.01  0.0    0 11.2 28 320   M    M   8 18     32 320

2  74  42  58  -1   7   0 0.00  0.0    0  4.7 15 310   M    M   6        17 310

3  67  43  55  -4  10   0 0.00  0.0    0  8.5 18  10   M    M   5        24 350

4  62  39  51  -9  14   0 0.00  0.0    0  9.9 22  10   M    M   2        25  10

5  69  33  51  -9  14   0 0.00  0.0    0  2.1 12 180   M    M   1 8      14 170

6  71  37  54  -6  11   0 0.00  0.0    0  5.8 18 130   M    M   4        22 130

7  76  42  59  -1   6   0 0.00  0.0    0  5.1 14 120   M    M   4        18 120

8  76  48  62   1   3   0 0.00  0.0    0  3.8 14 130   M    M   4 18     15 130

9  80  51  66   5   0   1 0.00  0.0    0  5.8 15 120   M    M   6 18     17 120

10  83  53  68   7   0   3 0.00  0.0    0  5.4 16 120   M    M   6 128    17 130

11  77  54  66   5   0   1    T  0.0    0 10.0 20 120   M    M   7 12     25 120

12  75  61  68   6   0   3 0.99  0.0    0  8.4 26 150   M    M  10 13     31 120

13  75  59  67   5   0   2 1.96  0.0    0  6.8 29 300   M    M   9 1238   38 280

14  66  57  62   0   3   0 1.41  0.0    0  7.7 31 130   M    M   8 138    33 130

15  80  54  67   5   0   2 0.00  0.0    0  3.5 14 360   M    M   4 128    16  30

16  72  55  64   2   1   0 0.00  0.0    0  9.4 21  10   M    M   3 8      25  10

17  72  47  60  -3   5   0 0.00  0.0    0  7.8 18 120   M    M   3        22 110

18  76  54  65   2   0   0 0.00  0.0    0  7.2 17 140   M    M   8        18 170

19  79  64  72   9   0   7 0.00  0.0    0 12.0 22 140   M    M   8        26 130

20  78  66  72   9   0   7    T  0.0    0 14.1 23 130   M    M   8 8      26 130

21  79  65  72   9   0   7    T  0.0    0 14.2 23 140   M    M   6        26 150

22  79  60  70   6   0   5 0.00  0.0    0 11.4 22 120   M    M   7 1      26 120

23  79  65  72   8   0   7 0.00  0.0    0 11.9 22 130   M    M   8        26 140

24  79  66  73   9   0   8    T  0.0    0 12.6 21 120   M    M   8 18     24 130

25  78  65  72   8   0   7 0.00  0.0    0 10.4 18 130   M    M   9 1      22 120

26  78  64  71   7   0   6 0.53  0.0    0 12.7 25 130   M    M   9 13     29 130

27  83  65  74   9   0   9 0.06  0.0    0  9.7 20 170   M    M   7 13     23 180

28  82  67  75  10   0  10 0.00  0.0    0 12.0 23 130   M    M   7 1      28 140

29  81  71  76  11   0  11 0.00  0.0    0 14.4 24 130   M    M   8        28 150

30  79  68  74   9   0   9    T  0.0    0 13.0 21 130   M    M   8 1      27 130

31  73  63  68   3   0   3 1.44  0.0    M  3.2 22 250   M    M   9 13     43 250

================================================================================

SM 2355 1729        75 108  6.40     0.0 274.7          M      200

================================================================================

AV 76.0 55.8                               8.9 FASTST  PSBL  %   6    MAX(MPH)

                                MISC ---->  # 31 130                 43    M

================================================================================

NOTES:

# LAST OF SEVERAL OCCURRENCES

COLUMN 17 PEAK WIND IN M.P.H.

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6) , PAGE 2

                                         STATION:  HOUSTON

                                         MONTH:    MARCH

                                         YEAR:     2007

                                         LATITUDE:   29 58 N

                                         LONGITUDE:  95 21 W

[TEMPERATURE DATA]      [PRECIPITATION DATA]       SYMBOLS USED IN COLUMN 16

AVERAGE MONTHLY: 65.9   TOTAL FOR MONTH:   6.40    1 = FOG OR MIST

DPTR FM NORMAL:   3.6   DPTR FM NORMAL:    3.04    2 = FOG REDUCING VISIBILITY

HIGHEST:    83 ON 27,10 GRTST 24HR  1.96 ON 13-13      TO 1/4 MILE OR LESS

LOWEST:     33 ON  5                               3 = THUNDER

                       SNOW, ICE PELLETS, HAIL    4 = ICE PELLETS

                       TOTAL MONTH:   0.0 INCH    5 = HAIL

                       GRTST 24HR     0.0         6 = FREEZING RAIN OR DRIZZLE

                       GRTST DEPTH:   0           7 = DUSTSTORM OR SANDSTORM:

                                                      VSBY 1/2 MILE OR LESS

                                                  8 = SMOKE OR HAZE

[NO. OF DAYS WITH]      [WEATHER - DAYS WITH]      9 = BLOWING SNOW

                                                  X = TORNADO

MAX 32 OR BELOW:   0    0.01 INCH OR MORE:   7

MAX 90 OR ABOVE:   0    0.10 INCH OR MORE:   5

MIN 32 OR BELOW:   0    0.50 INCH OR MORE:   5

MIN  0 OR BELOW:   0    1.00 INCH OR MORE:   3

[HDD (BASE 65) ]

TOTAL THIS MO.    75    CLEAR  (SCALE 0-3)   3

DPTR FM NORMAL   -81    PTCLDY (SCALE 4-7)  18

TOTAL FM JUL 1  1276    CLOUDY (SCALE 8-10) 10

DPTR FM NORMAL  -199

[CDD (BASE 65) ]

TOTAL THIS MO.   108

DPTR FM NORMAL    45    [PRESSURE DATA]

TOTAL FM JAN 1   136    HIGHEST SLP M ON M

DPTR FM NORMAL    37    LOWEST  SLP 29.54 ON  1

[REMARKS]

#FINAL-03-07#

*********************

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6)

                                         STATION:   HOUSTON

                                         MONTH:     FEBRUARY

                                         YEAR:      2007

                                         LATITUDE:   29 58 N

                                         LONGITUDE:  95 21 W

 TEMPERATURE IN F:       :PCPN:    SNOW:  WIND      :SUNSHINE: SKY     :PK WND

================================================================================

1   2   3   4   5  6A  6B    7    8   9   10  11  12  13   14  15   16   17  18

                                         AVG MX 2MIN

DY MAX MIN AVG DEP HDD CDD  WTR  SNW DPTH SPD SPD DIR MIN PSBL S-S WX    SPD DR

================================================================================

1  57  44  51  -2  14   0 0.12    M    0  4.7 15  10   M    M   9 12     16 360

2  52  37  45  -8  20   0    T    M    0  8.8 17 360   M    M   8 1      22 360

3  53  33  43 -10  22   0 0.00  0.0    0  4.5 10 200   M    M   7 18     13 210

4  65  37  51  -2  14   0 0.00  0.0    0  3.5 10 130   M    M   7 1      13 120

5  67  37  52  -2  13   0 0.00  0.0    0  2.4 12 100   M    M   5 1      14 100

6  71  38  55   1  10   0 0.00  0.0    0  5.5 16 160   M    M   5 1      20 160

7  76  45  61   7   4   0 0.00  0.0    0  5.3 16 170   M    M   5 18     18 180

8  77  58  68  14   0   3 0.03  0.0    0  5.3 13 330   M    M   8 18     15 330

9  58  46  52  -2  13   0 0.02    M    0 10.0 17 360   M    M  10 128    22  40

10  48  42  45  -9  20   0 0.00  0.0    0  8.3 17  20   M    M  10        20  10

11  56  45  51  -4  14   0    T    M    0  7.9 14 110   M    M  10 8      17 110

12  67  55  61   6   4   0 0.63  0.0    0  8.6 18 140   M    M   9 13     22 130

13  63  39  51  -4  14   0 0.00  0.0    0 14.2 25 310   M    M   5 1      30 330

14  48  37  43 -12  22   0 0.00  0.0    0 12.8 20 360   M    M   8        25  10

15  47  32  40 -15  25   0 0.00  0.0    0 10.8 20 330   M    M   6        25 320

16  50  26  38 -18  27   0 0.00  0.0    0  5.5 14 140   M    M   0        16 170

17  67  33  50  -6  15   0 0.00  0.0    0  9.9 29 330   M    M   1 1      37 310

18  64  34  49  -7  16   0 0.00  0.0    0  5.2 16 140   M    M   2        18 140

19  69  38  54  -2  11   0 0.00  0.0    0  8.6 21 170   M    M   6        28 170

20  73  57  65   9   0   0    T  0.0    0  4.5 13 160   M    M   9 1      16 160

21  81  58  70  13   0   5 0.13  0.0    0  6.0 16 170   M    M   4 1      18 170

22  82  53  68  11   0   3 0.00  0.0    0  5.9 17 130   M    M   8 128    21 140

23  71  59  65   8   0   0    T  0.0    0 12.2 30 140   M    M  10 18     33 140

24  80  55  68  11   0   3 0.22  0.0    0 11.3 22 210   M    M   8 18     29 210

25  72  45  59   1   6   0 0.00  0.0    0  5.4 18 340   M    M   4        21 330

26  80  41  61   3   4   0 0.00  0.0    0  5.6 17 210   M    M   4 18     23 240

27  80  50  65   7   0   0 0.00  0.0    0  7.3 17 120   M    M   6 128    22 150

28  76  63  70  12   0   5    T  0.0    0 10.4 18 160   M    M  10 18     23 160

================================================================================

SM 1850 1237       288  19  1.15     0.0 210.4          M      184

================================================================================

AV 66.1 44.2                               7.5 FASTST  PSBL  %   7    MAX(MPH)

                                MISC ---->  # 30 140               # 37  310

================================================================================

NOTES:

# LAST OF SEVERAL OCCURRENCES

COLUMN 17 PEAK WIND IN M.P.H.

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6) , PAGE 2

                                         STATION:  HOUSTON

                                         MONTH:    FEBRUARY

                                         YEAR:     2007

                                         LATITUDE:   29 58 N

                                         LONGITUDE:  95 21 W

[TEMPERATURE DATA]      [PRECIPITATION DATA]       SYMBOLS USED IN COLUMN 16

AVERAGE MONTHLY: 55.1   TOTAL FOR MONTH:   1.15    1 = FOG OR MIST

DPTR FM NORMAL:  -0.3   DPTR FM NORMAL:   -1.83    2 = FOG REDUCING VISIBILITY

HIGHEST:    82 ON 22    GRTST 24HR  0.63 ON 11-12      TO 1/4 MILE OR LESS

LOWEST:     26 ON 16                               3 = THUNDER

                       SNOW, ICE PELLETS, HAIL    4 = ICE PELLETS

                       TOTAL MONTH:   0.0 INCH    5 = HAIL

                       GRTST 24HR     0.0         6 = FREEZING RAIN OR DRIZZLE

                       GRTST DEPTH:   0           7 = DUSTSTORM OR SANDSTORM:

                                                      VSBY 1/2 MILE OR LESS

                                                  8 = SMOKE OR HAZE

[NO. OF DAYS WITH]      [WEATHER - DAYS WITH]      9 = BLOWING SNOW

                                                  X = TORNADO

MAX 32 OR BELOW:   0    0.01 INCH OR MORE:   6

MAX 90 OR ABOVE:   0    0.10 INCH OR MORE:   4

MIN 32 OR BELOW:   2    0.50 INCH OR MORE:   1

MIN  0 OR BELOW:   0    1.00 INCH OR MORE:   0

[HDD (BASE 65) ]

TOTAL THIS MO.   288    CLEAR  (SCALE 0-3)   3

DPTR FM NORMAL   -10    PTCLDY (SCALE 4-7)  16

TOTAL FM JUL 1  1201    CLOUDY (SCALE 8-10)  9

DPTR FM NORMAL  -118

[CDD (BASE 65) ]

TOTAL THIS MO.    19

DPTR FM NORMAL    -2    [PRESSURE DATA]

TOTAL FM JAN 1    28    HIGHEST SLP 30.50 ON 18

DPTR FM NORMAL    -8    LOWEST  SLP 29.60 ON 28

[REMARKS]

#FINAL-02-07#

Their is a couple of questions I would like to ask.  METRO's LRT uses 750 volts DC.  But there are other places in Houston which I believe, use hight voltage DC.  Medical equipment in the TMC is one item I have in mind.  I presume these items could have stray currents.  Are these affecting buildings?  Or could METRO be blamed for these.

Also, there is a transformer substation SW of the Wheeler Sta., near the Southwest Freeway.  This is high voltage AC, but is there leakage?

DominicMazoch,

There could be stray current associated with A/C power, and several explanations are available if you search the internet.

The larger propbles are associated with DC-powered urban rail systems.

There is a comprehensive book published by NACE (Houston-based national association of corrosion engineers), STRAY CURRENT CORROSION

The Past, Present, and Future of Rail Transit Systems

Michael J. Szeliga, Editor (copyright 1994), and costs about $110+

Ms. Sit,

This is a follow-up to a prior post above.

I am waiting for a response to an inquiry I made with another corrosion expert as to the protocol and results of this test report.  There is an ASTM standard (C876) which I am going to get a copy of to review.

Scanning the internet, there are several abstracts concerning this type of testing protocol.

Below is a snip of a portion of one article which indicates the test protocol for the TxDOT Expressway bridges may not have been as "aggressive" as it could have been.

The test dates for stray current leakage were March 5-10, 2007.  Results reported for each test location were made over a single 24-hour period.

There was no rain in Houston from February 24th through March 12th, so it seems suspicious that they choose a period of dry weather to test, likely after doing everything imaginable to minimize stray current prior to the tests.

The test points were installed in late January, and they could have tested sooner, and over more than one "dry" period.

A few days of testing, under conditions likely staged for ideal results, may not be truly representative of the uncontained stray current leakage conditions the 40-year-old steel-reinforced concrete bridge foundations (TxDOT reports 250,000 vehicles traverse daily) were subjected to for over 3.5 years of electrified tram operation.

The report METRO asked to to announce may not be sufficient, and, prudence requires regular re-testing, therefore, the announcement they gave you to post may be misleading to the public.

Further, METRO did not hold the December 2006 Corrosion Committee meeting, and has not yet scheduled one for 2007, and has refused to explain why.

==========

http://www.sescocp.com/tutorial.php

++++++++++

"If the soil is dry, it will be necessary to spill just a little water onto the ground (1/2 cupful) in order to ensure good contact between the soil and the electrode."

"It is desirable to practice the re-observation of pipe-to-soil potentials at regular, say, six-month intervals to have assurance that no physical changes had previously been made that would upset the balance of the cathodic protection circuit. This is for confirmation purposes, and to discover any changed condition which could result in corrosion damage to the structure. The period of retesting pipe-to-soil potentials should never exceed one year."

===========

Structure-to-soil potentials should be observed using a potentiometer, which draws no current, or a high resistance voltmeter, which draws only a very small current. A copper-copper sulphate electrode is used for the reference contact with the electrolyte (soil), and there must be direct contact with the structure (pipe).

To make a pipe-to-soil test observation, the lead wire attached to the copper sulphate electrode is attached to the positive (+) post of the meter. A wire attached to the negative (-) post of the meter is attached solidly to the pipe at any convenient point. This contact can be made by clipping directly to an above-ground valve, fitting, riser, or even by attaching to a probe bar pushed into the ground to contact the pipe.

The plug end of the copper sulphate electrode is then placed firmly against the moist soil at a position relative to the top of the buried pipe. If the soil is dry, it will be necessary to spill just a little water onto the ground (1/2 cupful) in order to ensure good contact between the soil and the electrode. The pointer on the voltmeter will then indicate the pipe-to-soil potential at that particular point on the pipeline.

Continuing and using the same direct contact to the pipe, but then using a very long wire between the meter and the copper sulphate electrode, it will be possible to move the electrode about and take many pipe-to-soil test observations at any number of intervals for hundreds of feet along the length of a pipeline.

If all test observations over the entire structure are found to be -0.85 volt or greater, it can be concluded that the entire structure is cathodic with respect to the sacrificial anodes (or with respect to the rectifier groundbed) and that there is no active corrosion taking place. This value of -0.85 volt considers a "built-in" constant of -0.52 volt as the solution potential between copper and copper sulphate in the reference electrode.

Pipe-to-soil observations should be made whenever there is any question or any doubt that the structure may not be under full cathodic protection. It is desirable to practice the re-observation of pipe-to-soil potentials at regular, say, six-month intervals to have assurance that no physical changes had previously been made that would upset the balance of the cathodic protection circuit. This is for confirmation purposes, and to discover any changed condition which could result in corrosion damage to the structure. The period of retesting pipe-to-soil potentials should never exceed one