WRGC Pinpointing Underground Gas Leaks
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Ron Six, Instructor Senior Utility Consultant AEGIS Insurance Services, Inc.
201/417-2487
WRGC Pinpointing Underground Gas Leaks
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A E G I SA E G I SAAssociated EElectric GGas IInsurance SServices
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• Utility Mutual Insurance Company(member owned)
• Formed in 1975 by 22 gas utilities
• Electric Utilities began joining in 1977
• 375 members – 95% utilities and related energy
AEGISAEGISBackground InformationBackground Information
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Our main job is not finding & fixing leaks
Our main job ispublic safety
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Is not an exact science.It is a developed skill which is learned and perfected through your mistakes and your successes.
Pinpointing
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Major Causes of Leaks
• Corrosion
• Mechanical failure
• Improper installation
• Improper design
• Faulty materials
• 3rd Party Damage - “Dig-Ins”
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#682 #686
Dead Cast Iron Gas Main
Water Main
4” Plastic Main 45 PSI4” Plastic Main 45 PSI
ASH STASH ST
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The “Find and Fix Syndrome”
The cure for this is to ask yourself a question “Where is the gas”? If you can answer the question that the gas is not affecting people and it is not affecting property you are cured. You must ask yourself this question on every leak before you get into the “repair” mode.
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Our main job is not finding & fixing leaks
Our main job ispublic safety
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Detect
Pinpoint
Repair
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w
h
e
r
e
is the
gas?
Evaluating The Leak
Where is the gas?
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Evaluating The Leak
here is the gas?• W• H• E• R• E
ow much is there?xtent of hazard (migration)elation to other structuresvaluate/evacuate
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Factors Affecting Gas Migration
• Soil type
• Soil moisture
• Surface cover
• Line pressure
• Depth of burial
• Leak size and age
• Change in elevation=slope
• Path of least resistance
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• Centering = Where is the gas?
• Pinpointing = Where is the leak?
• The leak must be centered before it is pinpointed
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Be Careful – “Don’t make a leak, looking for a leak.”
Centering The Leak
• Probe holes must be of sufficient depth
• Test all available openings
• “Zero out” N-S-E-W
• You must have sufficient information to make a good judgement
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Recent Natural Gas Incidents Springfield, MA
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Methods Of Locating The Line
• Maps
• Records
• System experience
• Electronic locators1. Basic principles of operation2. Inductive vs. Conductive3. Overcoming problems
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Consistency = Success
• Exact location of main, services etc.
• Size of test hole (aeration is the key)
• Depth of test hole (must be consistent)
• Location of test holes (same side of main)
• Instrument use (consistency in testing)
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PLACEMENT OF DRILL HOLES
• Where and how many?
• What size test holes?
• How deep?
• How far apart?
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Size of the Test Hole
½” Test Hole 1” Test Hole
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Size of the Test Hole
½” Test Hole 1” Test Hole
4x’s the Aeration4x’s the AerationFrom the 1” Test Hole vs. From the 1” Test Hole vs.
the ½” Test Holethe ½” Test Hole
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The Size of the test hole is critical
Pinpointing with a ½” test hole Pinpointing using a 1” test hole
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Minnich Hornet Drill
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SAVE
ANOTHER
MISSED
EXCAVATION
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30% Gas @ Foundation Wall
90% Gas @ Curb
Concrete Sidewalk
4” Bare Steel 4” Bare Steel 45 PSI45 PSI
OLD MAIN STREETOLD MAIN STREET
#400#402#404
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Use Of Soil Purger (cont’d)
• The soil purger is your best friend or worst enemy, depending on where and how it is used
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Types of Soil Purgers
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30% Gas @ Foundation Wall
90% Gas @ Curb
Concrete Sidewalk
8” CI UP8” CI UP
OLD MAIN STREETOLD MAIN STREET
#400#402#404 Never purge Never purge near foundationnear foundation
Never purge Never purge near foundationnear foundation
Purge Away From Purge Away From FoundationFoundationThis will draw the gas away from This will draw the gas away from the building and block the gas from the building and block the gas from migrating to the foundation wallmigrating to the foundation wall
Purge Away From Purge Away From FoundationFoundationThis will draw the gas away from This will draw the gas away from the building and block the gas from the building and block the gas from migrating to the foundation wallmigrating to the foundation wall
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Grade 1 Leak Repairs (Did you find “a” leak or did you find “the” leak?)
• You must not leave a Grade 1 Leak indication as long as the conditions that got you there are still present. If the readings went from 30% gas to 3% gas at the foundation it is still a technical Grade 1 leak. Purge the soil, get the readings to 0%, wait and make sure that the readings do not return.
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60% Gas
15% Gas
8” Steel UP CWP
Maple Street
Curb
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8” Steel UP CWP
Curb
Service Line
70%
50%
75%
8-10’ 8-10’
Maple Street
60% Gas
15% Gas
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8” Steel UP CWP
Service Line
40%
35%
45%
0%15%
50%50%50%45%10%0%
Maple Street
60% Gas
15% Gas
Curb
Slope
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Using The Soil Purger In The Pinpointing Process
• Purge from a hole where you know that the leak is not
• Plug holes near purge point
• Dense soil or moisture – time the purge/purge each hole
• Use it only when all other methods have failed
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Test Methods
• Combustible gas indicator1. Top & bottom of hole2. Time the readings
• Natural ventilation1. Wait…let holes vent
• Blow pipe – vapors/soap top of hole
• Odor
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Use Of Soil Purger
• Should not be used on every leak
• Operation:1. In the pinpoint process2. As a safety tool –
Never use near foundation of building3. Residual gas
• Choosing a purge point is the key
• Techniques
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10% Gas In Sewer Manhole
6” Steel UP6” Steel UP
ASH STREETASH STREET
CURB LINE
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Manhole
CGI Test
CGI Test
Gas Readings In Manhole
• Is gas in the sewer or just using the manhole as a venting point?
• Test top and bottom
• Percent gas readings will generally not be sewer gas
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Using Test ResultsUsing Test Results Using System DesignUsing System Design
Using Your ExperienceUsing Your Experience
“Make Your Mark”
Remember:Remember: It is much cheaper to drill than to dig.It is much cheaper to drill than to dig.
Do you have Do you have enoughenough holes to give holes to give you you enough information about the enough information about the leak?leak?
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The Dry Hole
• Probe along the pipe
• Expose all of the pipe, not just the top
• Learn from your mistakes
• Use the hole to your advantage…no one “hits” them all
• Is it our gas?
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High SchoolHigh School
6565 6969 7171
K-StreetK-Street
6” Low Pressure Cast Iron6” Low Pressure Cast Iron
4” High Pressure Steel4” High Pressure Steel
6767
25% gas in sewer manhole25% gas in sewer manhole
15% gas @ curb15% gas @ curb
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Checking After The Repair
• Did we find “the” leak?
• Residual gas – when will it go away?
• Cleanup/plugging the test holes
• Importance of proper documentation
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Stray Gas
• Is it lighter or heavier than air?
• Is there ethane in the sample?
• Is it a hazard?
• What is sewer gas/decomposition gas?
• Natural gas vs. stray gas
• Use of charcoal filter
• Use of collection bottles/bags
• Responsibilities regarding stray gas
• “Reasonable person concept”
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Ethane
No Ethane
Natural GasNatural GasNatural GasNatural Gas
Sewer GasSewer GasSewer GasSewer Gas
MethaneNitrogen
CO2
Chromatographic AnalysisComparison
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Remember:The Job Is Not Completed
• Until all paperwork/documentation is completed:
– Neatly– Thoroughly– Accurately
• You may do everything right, but you may be judged by what is or is not documented
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Be Alert
Be Prepared
Be Safe
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