PACIFIC NORTHWEST CLEAN WATER ASSOCIATION 2010 …

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Presented by: Steve Kebbe, P.E., Principal Engineer , Clean Water Services Susan M. Gierga, P.E., Murray, Smith & Associates, Inc.

PACIFIC NORTHWEST CLEAN WATER ASSOCIATION2010 ANNUAL CONFERENCE

October 24-27, 2010

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PRESENTATION OVERVIEW

• Existing Facilities

• Evaluation

• Corrective Measures

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CLEAN WATER SERVICES TREATMENT PLANTS

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TWIN 24-INCH FORCE MAINS

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FORCE MAIN COMPONENTS

Pipelines are plastic with the following exceptions:

• Fittings are ductile iron• Three creek crossings are ductile iron• Air release and vacuum valve assemblies have

metal components

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CORRODED VALVE COMPONENTS

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CORRODED THREADS

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INSPECTION OF THE VAULTS

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A SINGLE AIR RELEASE VALVE

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TWO AIR RELEASE VALVES

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TWO AIR RELEASE, TWO VACUUM BREAKERS

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VENT WITHIN THE VAULT

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VENT TO A NEARBY MANHOLE

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VENT TO ODOR CONTROL CANISTERS

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FINDINGS

• Corrosion within the vaults

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CORROSION WITHIN THE VAULTS

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FINDINGS

• Corrosion impacting the buried (metallic) components of the pipeline

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CORROSION IMPACTING THE BURIED PIPE AND FITTINGS

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CORROSION IMPACTING THE BURIED PIPE AND FITTINGS

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FINDINGS

• Microbiologically Induced Corrosion (MIC)

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MICROBIOLOGICALLY INDUCED CORROSION (MIC)

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MICROBIOLOGICALLY INDUCED CORROSION (MIC)

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CORROSION 101

Corrosion – The deterioration of a substance (usually a metal) because of an electrochemical reaction with its environment. External Corrosion Introduction to Chemistry and Control, Manual M27, AWWA.

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CORROSION 101

ATOM

Ion – an atom that has lost or gained an electron.

Oxidation – the process of stripping electrons from an atom.

Reduction – the process of adding electrons to an atom.

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CORROSION 101

Anion – an ion that has lost an electron (always negative) and therefore has a positive charge.

Cation – an ion that has gained an electron and therefore has a negative charge.

At least two types of IONS:

Positive Ion - Anion

Negative Ion - Cation

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CORROSION 101

Anodic Process –

1.Positively charged ions (anions) leave the solid surface and enter into solution;

2.Anode – the point where the anion leaves the surface. This is the point where evidence of corrosion appears.

Cathodic Process –

1.Positively charged ions (anions) leave the solution and adhere to the metal surface.

2.Cathode - the point where the current returns to the metal from solution and protects it.

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GALVANIC CORROSION

Galvanic corrosion can occurs whenever two or more dissimilar metals are in contact with each other while exposed to an electrically conductive liquid (such as sea water or rain water).

One metal corrodes preferentially when in electrical contact with a different type of metal.

The most reactive of the metals becomes corroded, in preference to the less reactive metal, which remains unaffected.

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CORROSION 101

Four essential elements of any corrosion cell:

• There must be an anode;

• There must be a cathode;

• Both anode and cathode must be immersed in a conducting electrolyte;

• There must be a metallic conductor between the anode and the cathode.

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THREE DISCRETE PROJECTS

1. Vault Replacement Project

2. Impressed Current Project

3. Buried Metallic Fittings Project

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VAULT REPLACEMENT PROJECT

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GALVANIC ANODE CATHODIC PROTECTION

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IMPRESSED CURRENT PROJECT

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IMPRESSED CURRENT CATHODIC PROTECTION

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BURIED METALLIC FITTING PROJECT

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SOIL RESISTIVITY/CORROSIVITY

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Presented by: Steve Kebbe, P.E., Principal Engineer , Clean Water Services Susan M. Gierga, P.E., Murray, Smith & Associates, Inc.

PACIFIC NORTHWEST CLEAN WATER ASSOCIATION2010 ANNUAL CONFERENCE

October 24-27, 2010

Documents

PACIFIC NORTHWEST CLEAN WATER ASSOCIATION 2010 …