Technologies for Assessing the Condition of Water Mains NC AWWA Spring Conference 2014 Matt Shultz, PE - HDR

Condition Assessment

•  Determining and documenting the physical state of infrastructure at a point in time

•  Identify improvements to extend asset life •  Prioritizing improvements

Aging Infrastructure is the driver for Condition Assessment and Renewal

Reference: AWWA, Buried No Longer: Confronting America’s Water Infrastructure Challenge, 2012

Water Main Failures Can Cause Problems

Photo: Bill O’Leary, Washington Post

….and have Consequences

Photo: Al Seib, LA Times

Three Components of Condition Assessment Determine Success and Usefulness

Assessment Technologies…there are a lot of them

Source: EPA, 2012 Condition Assessment Technologies for Water Transmission and Distribution Systems

Ductile and Cast Iron Pipe…aging is a problem

Aging can occur from: •  Internal corrosion •  External corrosion •  Fatigue Failure Methods: •  Pits or rust holes •  Bursts (longitudinal) •  Breaks (circumferential) •  Leaks at joints or service taps

Pitting Corrosion

General Corrosion

Aging is a problem…but not always the answer

The Evolution of Iron Pipe is Dominated by Reduction in Wall Thickness

1928 Class D CI

1.58” 1952

Class 150 CI 1.22” 1957

Class 27 CI 0.94”

1957 Class 22 CI

0.87” 1965 Class 3 DI

0.58” 1976

Class 50 DI 0.43”

1991 Class 150 DI

0.38”

EXAMPLE FOR MINIMUM WALL 36-INCH IRON PIPE

External Corrosion…corrosive soils

Soil and Water Analysis •  Resistivity, pH, Sulfate, Chloride, Redox Potential, Etc.

–  DIPRA 10-Point (AWWA C105) •  Linear Polarisation Resistance

External Corrosion… stray currents

ANODEGROUND BED

+

CATHODICALLY PROTECTEDSECTION OF PIPELINE A

-

POSITIVE DC CURRENT FLOW PIPELINE A

PIPELINE B

RECTIFIER

ACCELERATED CORROSIONON PIPELINE A

Overhead Power Transit Systems

Other Utilities

Ductile and Cast Iron – Assessment Technologies

Electromagnetic: Remote Field Eddy Current •  PICA’s See Snake •  Provides end to end 360-deg evaluation •  Accurate determines pit size, depth, and location •  Provides general corrosion loss •  2” to 36” pipes, tools match pipe size •  Free swimming or tethered •  Waterline can remain in service •  Can navigate through bends

Design - PCCP Standards Changed Over Time …and not always for the better

Assessment Technology - PCCP Water Mains

Acoustic Events/Wire Breaks Leading up to SDCWA Failure

Asbestos Cement Pipe

Deterioration can occur from: •  Soft Water Corrosion •  Acidic Corrosion (low pH water) •  Sulfate Corrosion •  H2S Corrosion Failure Methods: •  Bursts (longitudinal) •  Breaks (circumferential)

AC Pipe: Acoustic Velocity Thickness

A comparison by Sweetwater Water Authority (CA) was promising

Technologies for Assessing the Condition of Water Mains NC AWWA Spring Conference 2014 Matt Shultz, PE - HDR