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The excavator’s push for damage prevention. DAMAGE PREVENTION CONFERENCE. Mike Kemper , NPL Construction Company December 9, 2008. The Often Forgotten Underground World. Who is NPL?. CORE BUSINESS:. The safe installation & maintenance of reliable energy distribution systems.

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The excavator’s push for damage prevention

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The excavator’s push for damage prevention


Mike Kemper,NPL Construction Company December 9, 2008

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The Often Forgotten Underground World

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Who is NPL?


  • The safe installation & maintenance of reliable energy distribution systems

  • 2500 employees

  • 5.7M work hours

  • 16.5M feet installed/replaced

  • Fleet of over 3000 units ranked in Top 20 in construction industry

  • Heavy One-Call user

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What is trenchless technology?

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How about these?

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Do we have a problem?

Who’s responsible for marking?

Sewer Main

Lateral to mains connection

Installed line


City street

Property line

What could happen?

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Old Gas Service Line

Sewer Lateral

New Gas Main

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Madill, OK 1992

Some hits are a time bomb!

Madill, OK 2007

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How often does this happen?

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Odds of getting a hole in one

1 in 12,000


Montana Gimmie

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CGA ConferenceMarch 2008

•2/3 of attendees raised their hands

  • Result: Best Practices Task Group

Q & A

“How many of you have experienced Crossbores?”

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What we know:

  • Minnesota Public Utilities Commission

    • 27 cross bores reported in a 6 month period

  • Palo Alto, CA

    • 4 blocks inspected. 24 cross bores found

  • City A

    • 2 cross bores per mile in 200 miles of sewer main

    • One cross bore at a school

  • City B

    • 3 cross bores per mile of sewer main

    • One cross bore at a hospital

  • City C

    • 2% cross bores out of 11,000 sewer laterals inspected

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Austell, GA

Bellwood, IL

Burlington, VT

Cincinnati, OH

Clayton County, GA

Fairfax, OK

Gilbert, AZ

McKinney, TX

Madill, OK

Massena, NY

Merriam, KS

Middletown, OH

Mobile, AL

Phoenix, AZ

Rochester, MN

St. Paul, MN

Tucson, AZ

White Bear Lake, MN

How often do explosions happen? Known explosions in past 10 years

*Based on preliminary investigations in 16 states

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“Houston, we have a problem”

- Captain James Lovell,

Spacecraft Commander of Apollo 13, 1970

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The exposure is:

  • Low Frequency - High Severity

  • Short Term vs. Long Term

  • • A “predictable surprise”

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Unmarked sewer lines are risky business

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One bad move…

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Even when it seems as though you were born to do the job, things can go wrong.

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So what should we do?

  • Plumbers

  • Academia

  • Legislators

  • Regulators

  • Contractors

  • Manufacturers

  • Owner/Operators

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Headline: March 13, 2006“ Woman, Granddaughters Barely Escape Explosion ”

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Story: March 16, 2006

After seeing bubbles in the water and smelling the natural gas, the plumber told the grandmother and her three grandchildren to get out of the home immediately.

• Middletown, Ohio building inspector:

"The plumber did absolutely nothing wrong. He had no way of knowing the gas line had been breached.”

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Duke’s Verification Process

  • Plumber or Customer calls re: sewer blockage

  • Duke sends 1st responder to locate

    • No conflict – Plumber cleans sewer line

    • Potential conflict – Dispatch C&M crew to:

      • disconnect gas service and let plumber clean line

      • test and reconnect service

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The Use of Trenchless Excavation Equipment in Relation to the Marking of Underground Facilities


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“How important is the issue of unmarked sewer

lines to your business?”

• 40 responses from major trenchless

contractors in the US

• Average Importance: 9.26 (10= high, 1= low)

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“Are owner / operators you work for required to

mark their facilities?”

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  • 40+ states already require some level of locating by the sewer owner/operator

    • Is that the home/building owner or municipality?

      • Courts have ruled that home/building owner does not have expertise to be responsible for location of sewer laterals.

    • Does the State require them to join the One-Call system?

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Recent progress in AL, AZ, GA, KS, MN, NM, NV, SD, TN, VA, WI …

More can be done in most states

New installations

Replacement installations

Who is responsible for enforcement?

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Does there need to be better enforcement of violators?

Need for better enforcement of violators





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  • 2005: 258 (5 per week) HDD hits in US

  • Potentially affecting HDD use

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9th Annual HDD Survey

Growing Pains

Underground Construction, June 2007

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Industry standards

  • HDD Consortium, Horizontal Directional Drilling - Good Practices Guidelines

  • EMI, Safety Manual: Directional Drilling Tracking Equipment

  • DCCA, Horizontal Drilling: Safe Operations Guidelines

  • NULCA, Excavation Practices & Procedures for Damage Prevention: A Guide For Protection of Underground Facilities

  • CNA, Minimum Damage Prevention Guidelines: Excavation Practices For Underground Facilities

  • Manufacturer’s Manuals

  • State One-Call Manuals

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Sewer Line Conflict?

Yes / No, proceed


No / Yes, proceed

Sewer Main

Sewer Laterals

NPL Policy #22, Process 2

Visually Verify Bore Clearance

No / Yes, proceed

NPL Policy #22, Process 3

Spaced Verification

No / Yes, proceed


Call Area Manager





(Bore Card Required by Each Crew at Each Address)

Conflict is defined as either crossing a sewer line within 4’ or paralleling one within 4’.

Privately-Owned Sewer Systems (trailer park, school, etc.) require 100% daylight.

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  • Reduction of risk can be achieved:

    • Formal program to address?

      • AGA Survey of 60 LDC’s: 26% have

    • Better policies

    • Relatively new technology for both new

    • and legacy installations

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Do you want your contractor gambling?

Unmarked Sewer



Contingency Plan

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One LDC’s standard

  • Verification is required using any or all:

    • Check manholes for depth and direction

    • Fish tape with Sonde transmitter

    • Excavate 1’ > depth of lateral near start and end of bore

    • GPR, if it works

    • Camera before/after bore

  • Pre and post construction door hangers

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Duke Energy’s sewer locate

& inspection process

New installations:

  • All sewer mains and laterals must be pre-located to the sidewalks

  • Curb-to-meter services are completed with open trench

  • Post Camera required before ANY GAS UP

  • All recordings are copied and sent to the local sewer district

  • Sewer Tag is attached to sewer cleanout

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Duke Energy’s sewer locate

& inspection process

Replacement installations:

  • Site visit all projects

  • Determine if sewer is in the front

  • Determine depth of sewers and

  • Document elevation of first floor vs. street grade

  • Pre-locate sewer mains & laterals

  • Post-camera required before ANY GAS UP

    • 8 cross bores found out of 8000 pre-camera’d services

    • .1% vs .01% for a hole-in-one

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  • Less than 5% more

  • How do we justify not spending the $?

  • Is it worth one life?

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Legacy solutions

  • Educate local plumbers, rental stores, mobile home park owners … to look before they root;

  • Find installed problems …before they find us.

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Case study

Case study of an inspection program to inspect sewer mains and laterals for possible cross bores

  • 4 priorities identified:

    • Schools

    • Hospitals

    • Multi-Family

    • Mobile Home Parks

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Susceptibility factors

  • Low depth of cover of the sewer lateral:

    • Privately-owned sewer systems

    • Areas with shallow sewer mains

      • Terraced homes

      • High water tables

      • Shallow or no basements

  • Areas where the gas line is buried deep

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4 Methods used

  • Maps and Recordsfor elimination

    • Wherever evidence of open trench installation

    • Facilities installed after “no blind bore” policy began in March, 2002

  • Electronic separation

    • Electronically locate depth and run of sewer lateral and gas service/main

    • Separation greater than 18” required

  • Video past intersection point

    • Used ProPipe and Orbit to complete pilot

  • Dig and Inspect

    • As needed

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Video inspection technology

  • ProPipe main and lateral camera launcher for 8” and larger lines

    • Range 1600’ (800’ each way) of sewer main and 80’ of sewer service

  • ProPipe hand-operated camera for 6” and smaller lines

    • Range 200 feet

  • Audio and video capable

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Video inspection technology


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Main & lateral camera launcher

for 8” and up


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Locating underway

The Launch

There it goes …


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Hand-operated camera

for 8” and up

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Video recording


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Pilot summary stats – 6/08

  • About 300,000 investigations

  • 103 cross bores found (.03%)

    • 76 found via the Program

    • 27 found by plumbers/Roto Rooter

  • 22,005 single family homes inspected with no cross bores

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What’s next?

  • Proceed company wide:

    • All plastic services installed prior to 1992

    • All replaced/relocated services installed between 1992-2002 when new Policy started

    • Includes single family residences

    • Estimated completion: 5 years

  • Continue Public Education Program

    • Presentations to 132 residential and commercial plumbing contractors so far

    • Information mailed to all underground contractors

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  • Guidelines for locating pre-construction and verification post construction

  • Guidelines for Identification of Legacy Cross Bores

  • Sample Legacy Inspection Contract

  • Equipment manufacturers – notices

  • Sample ordinances

    • Requiring Drain Cleaner training

    • Requiring Accessibility to Sewer Maps

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“Luck is not a strategy”

- Steve Ewing

Past Chairman AGA, Vice Chair, DTE

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Goal: Protect all parties









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