FIELD RISK SCREENING OF WATER MAINSEstablish a program to field screen transmission mains• Identify potential problems• Address proactively

• Targeted rehabilitation• Corrosion protection

ASSET MANAGEMENT PROGRAM 2012 started program to identify

water main replacement using risk-based approaches.

Primarily focused on distribution mains.

Majority of chronic break areas have been addressed.

Transmission mains are more cost effective to perform condition assessment and targeted repair/replacement

Dayton Water

MAJOR SYSTEM OUTAGES

February 2019 – 36” water main failure 2.5 million gallons lost in first 10 minutes, estimated 150

MGD total 400,000 people out of water for more than 40 hours $860,000 to repair (not including loss of revenue, staff

time, etc)

August 2020 – 48” water main failure 27,000 customers affected $1.4M to repair (not including loss of revenue, staff time,

etc)

Dayton Water

CONDITION ASSESSMENT December 2018

Pure Pipe Diver and Smart Ball

48” PCCP water main

3.14 miles

$500,000

No leaks, a few minor wire breaks

Dayton Water

WHAT DO WE DO? Desktop model limited by available

information

There are amazing tools out there -Expensive!

How do we address the risk of transmission mains without spending lots on condition assessment or replacing mains that don’t need replaced?

Dayton Water

DUCTILE/CAST IRONThe most common failure mode for ductile iron pipe is due to corrosion, (AWWA report, “Buried No Longer”)

10-Point soil evaluation for corrosive factors in soil.

10 Points = Corrosive Soil

Resistivity is largest factor and can make soil corrosive by itself.

Dayton Water

PCCP PIPEXylem

AWWA M77CONDITION ASSESSMENT OF WATER MAINS

Chapter 5 – External Corrosion Surveys

Establishes a formal process for evaluating mains for factors that may indicate a failure soon.

M77 EVALUATION PROCESS

Desktop Risk Evaluation – Identify high risk mains

Step 1 – Pre-Assessment Review records and site conditions

Step 2 – Indirect Inspection (typically use 2 methods) Soil resistivity measurements Soil sampling Corrosion potential measurements Electrical continuity testing Close-internal survey Visual field check for other potential issues

(sources of stray current, etc) Step 3 – Direct Examination (dig up pipe for

inspection) Step 4 – Post Assessments

Dayton Water

EM-31Measures conductivity of the soil and maps it (GPS)

Location of metal in the ground

Soil that has corrosive factors (conductivity/resistivity)

Contamination

20-foot depth

6-foot width

Dayton Water

S. GETTYSBURG AVE “X” represents road cuts for main

break repairs.

Soil samples at 2 sites

Soil samples testing for contamination did not return a significant level of contamination. This was primarily corrosive soil.

Site 1

Site 2

SITE EM-31 approximate

(mS/m)

Soil Resistivity (ohm-cm)

SAMPLE DEPTH

1 60-80 1640 52 60-80 1520 3

Dayton Water

S GETTYSBURG AVE No breaks in this area

Dayton Water

MAD RIVER NORTH OF OTTAWA TREATMENT PLANT Values are valid in a 6-foot path

along the instrument path.

Screening would have multiple passes over an area

Soil saturated with river water

Soil saturated with river water

Corrosive soil or contamination

Dayton Water

WATER RECLAMATION Potential use at plants for locating

issues.

Searching for leaks from trickling filters.

Dayton Water

MIAMI WELL FIELD –WELL #9 Native soil not corrosive

“Hot Spots” identified

Dayton Water

CORRELATION BETWEEN EM-31 AND PIPE DIVERPipe Diver located several areas with minor wire breaks (purple triangle)

Wire Break Locations

Wire Break Locations

48” PCCP12” Steel

Dayton Water

VENDOR INFOInvestigation of oil production fields

Capable of detecting a 2-inch diameter copper pipe at a 10-foot depth

Detect elevated chloride levels (factor in corrosion of PCCP pipe)

Dayton Water

LINE LOCATINGMiami Treatment Plant

48” PCCPWater Main

South of electrical substation

Dayton Water

IMPLEMENTATION

Identify high risk mains from risk model Verify all records and update Site investigation

EM Tool Visual inspection during survey for any

potential site conditions that may affect the main (stray current, etc)

Soil samples in areas showing abnormal conditions.

Identify any warranted further investigation.

Target mitigation of high-risk sections of mains

Coordinate with other tools Smart Water System Leak Detection Improved failure data capture and

analysis Corrosion Control

Service contract with vendor to perform survey, with option to buy.

Future staff position focused on specialty engineering tools.

QUESTIONS OR INPUT?