Transcript Cross-Bores: How Big is the Issue? Samuel T. Ariaratnam, Ph.D., P.E. Dan Weaklend

Cross-Bores:
How Big is the Issue?
Samuel T. Ariaratnam, Ph.D., P.E.
Arizona State University
Dan Weaklend
NPL Construction Co.
Las Vegas, NV ● December 9 , 2008
Trenchless Technology for Installing
Distribution Lines
Impact Moles
Horizontal Directional Drilling
Should we gamble?
It’s about Accuracy!
Possible Scenario?
Who’s responsible
for marking?
Sewer
Main
Lateral to
mains
connection
What could
happen?
New
service
Line
City
street
House
Property
line
Cross-Bored Laterals Can Be
Found in Any Neighborhood
Or Any City!!!!
Avoid mechanical cleaning tools
without verification!
MINNESOTA
MAINE
Headline:
February 15, 2002
Officials Seek Answers In Gas Explosion
Headline:
February 16, 2002
Shocked Gas Company Pleads Ignorance
• The natural gas explosion that rocked a
mobile home park on Wednesday shocked
officials who say they never knew their gas
line bisected the clay sewer pipe.
• A plumbing contractor was removing tree
roots from a sanitary sewer line in the 127
unit mobile home park when the gas line
was struck.
• “About the only time we know about sewer
lines is when people call because they get
backed up and have to call someone in to
clean them”, said the Operations Manager
with the local gas company.
3/13/06 Family Escapes as Gas
Explosion Levels Home
Middletown, OH 3/16/2006
• After seeing bubbles in the water and
smelling the natural gas, the plumber told
a grandmother and her three
grandchildren to get out of the home
immediately.
Madill, OK 1/2/2007
OK Natural Gas line
was installed in 1992
Mobile, AL
• Action: HDD contractor for a gas utility hit
a sewer lateral on the pilot bore and then
hit a gas service line on the pullback
• Scenario: Gas escaped into the sewer line
and the house blew up several hours later
• Consequences: One critically injured, one
seriously injured, home was destroyed
Cincinnati, OH (2006)
• Action: HDD contractor installed a gas line
• Scenario: Plumber was roto-rooting a
sewer lateral and pierced a cross-bored
natural gas line
• Consequences: An explosions damaged
the house.
St. Paul, MN (2000)
• Action: Cross-bored sewer lateral
• Scenario: Plumber was cleaning a sewage
blockage and struck a natural gas line. He
ran upstairs to get out but the door was
locked.
• Consequences: The house blew up and
he was severely burned
Rochester, MN
• Action: Cross-bored sewer lateral
• Scenario: Plumber was cleaning a blocked
sewer lateral and cut a natural gas line
• Consequences: Fortunately, the area was
evacuated prior to the explosion. Three
mobile homes were destroyed
Winona, MN (2001)
• Action: HDD crew hit a sewer lateral, while
installing a gas line
• Scenario: Fortunately, the crew had a
microphone in the sewer main and
detected the strike
• Consequences: The line was
subsequently repaired and no incident was
recorded
Bellwood, IL (1997)
• Action: Contractor was drilling using HDD
• Scenario: The crew hit a sewer lateral and
gas line.
• Consequences: The house blew up;
however, no injuries were reported.
What are the Odds?
11,000 Laterals Were Inspected in a City
250 Cross-Bores Identified And Repaired;
2% of Sewer Laterals Were Hit
How Many Might Have Led To
A Major Incident?
Odds of getting a hole-in-one
5,000 to 1
0.02%
Other Odds
Becoming an astronaut
13,200,000 to 1
Royal Flush on first five
cards dealt
649,740 to 1
Becoming a pro athlete
22,000 to 1
Writing a NY Times
best seller
220 to 1 or 0.45%
Struck by lightning
500,000 to 1
In Another City…..
• A Four Block Area Was Inspected;
• 24 Cross-Bores Were Discovered.
The Greatest Concern
CATASTROPHIC
PERSONAL
LOSSES
Because Some
Utility Lines
Are
EXEMPT
FROM
LOCATING LAWS
Interesting Interpretations?
• In Kansas and Vermont:
– Sewer is not designated as
a “facility”;
• In California:
– exempts “non-pressurized”
lines;
• In Missouri:
– exempts “privately owned”
sewer and water lines.
States Exempt from Locating
Sewer Laterals
• CA – non-pressurized sewer lines excluded
• KS - Sewer not included in list of items designated as
facilities
• MO – Except … sewer lines owned solely by the owner
or owners of the real property to which such lines
provide service shall not be considered underground
facilities
• NJ – includes only forced-sewage lines, does not
include gravity sewers
• NM - Sewer not included in list of public utilities
• RI – Sewer not included in list of public utilities.
• TX – Water, Slurry, and Sewage lines excluded
• VT – Only gas, electricity, and telecommunications are
included
Minimize your risk by
conducting an on-site field
investigation prior to boring
Confirm the location of existing
utilities
Marking Laterals
Reducing Risks
• Care must be taken when boring near
sewer service laterals
• Need for assigning responsibility for
locating and marking these laterals
• Boring contractors need to follow good
practices during installation of all utilities
• If a blockage occurs, must investigate
possible causes “prior” to using mechanical
means to unblock the lateral
“The Use of Trenchless Excavation
Equipment in Relation to the
Marking of Underground Facilities”
DCA HDD Committee &
Arizona State University
Survey Questionnaire
Distributed in 2008
Question 1
• How important is the issue of unmarked sewer lines to
your business? (10 = high; 1 = low)
*40 responses were received from trenchless
contractors in the United States
• Average importance: 9.26
Question 2
• Do you believe that there needs to be better
enforcement of violators?
Need for better enforcem ent of violators
0%
Yes
No
100%
Question 3
• In the areas where your company/ division does business,
are all owners of underground facilities required to mark
their plants?
Requirem ent of ow ners to m ark UG utilities Water to building w all
Requirem ent of ow ners to m ark UG utilities Sew er to building w all
13%
20%
Yes
Yes
No
No
80%
87%
Requirem ent of ow ners to m ark UG utilities Electrical to building w all / m eter
20%
Requirem ent of ow ners to m ark UG utilities Gas to building w all / m eter
13%
80%
Yes
Yes
No
No
87%
Question 3 (cont’d)
• In the areas where your company/ division does business,
are all owners of underground facilities required to mark
their utilities?
Requirem ent of ow ners to m ark UG utilities Com m unication to building w all
Requirem ent of ow ners to m ark UG utilities Other lines to building w all
15%
38%
Yes
Yes
No
No
62%
85%
Question 4
• Approximately how many tickets per year does your
company/ division typically request?
Number of tickets requested per year by the
companies/divisions
No. of companies
43.9%
18
16
14
12
10
8
6
4
2
0
26.8%
19.5%
9.8%
<1000
1000-5999
6000-10000
No. of tickets (Categories)
>10000
Question 5
• Has your company/division ever had to pay any claims
as a result of damaging a line that was not required to be
marked by law or regulation?
Claim s on dam aging a line that w as not
required to be m arked by law or regulation
22%
Yes
No
78%
Question 6
• If you answered Yes to Question 5, approximately how
many times per year during the past 5 years have you
had to do so?
Num ber of tim es claim s occured
13%
0%
1-10
3%
11-25
6%
26-50
51-75
76-100
16%
62%
Over 100
Question 7
• If you answered Yes to Question 5, what is your
estimated total cost for the past 5 years for repairing
these hits?
No. of companies
Total cost in the past 5 years for repairing these hits
10
9
8
7
6
5
4
3
2
1
0
Average: $ 130,697
22.6%
High: $ 1,750,000
16.1%
16.1%
12.9%
<$10,000
$10,000$24,999
12.9%
$25,000$49,999
$50,000$74,999
9.7%
9.7%
$75,000$99,999
$100,000$200,000
Total cost in repairs ($)
Over
$200,000
Question 8
• Was there any single claim(s) in excess of $100,000 (or
that resulted in a fatality) that was a result of a facility
owner not being required to mark their lines?
Any single claim >$100,000
(or resulted in fatality)
12%
Yes
No
88%
Question 9
• List any cases of injury or large property damage
caused by a crossbore that you might have heard of that
occurred here in the U.S.
Dam age caused by crossbore
Type of facility
13%
17%
3%
3%
Residence
Phone
Sew er
Gas
10%
Fibre optic
Water
Trailer Park
20%
34%
Question 9 (cont’d)
• List any cases of injury or large property damage
caused by a crossbore that you might have heard of that
occurred here in the U.S.
Dam age caused by crossbore
Location
15%
7%
4%
Northeast
Southeast
7%
Midw est
Southw est
West
67%
Question 10
• If you answered Yes to Question 5, what types of lines
were crossbores?
Types of lines that w ere crossbores
10%
Water
18%
Sew er
16%
Gas
Electrical
Communication
29%
13%
14%
TV Cable
Question 11
• What region(s) of the country does your
company/division typically perform work in?
Profile of the com panies surveyed
Regions
30%
East
37%
Midw est
West
33%
Question 11 (cont’d)
• What region(s) of the country does your
company/division typically perform work in?
Profile of the com panies surveyed
Regions
21%
Northeast
23%
Southeast
Midw est
Southw est
11%
West
21%
24%
Conclusions
• Unmarked utilities is a major issue with
potentially severe consequences
• Better enforcement is required to ensure
that those responsible for marking utilities
do so in the interest of public safety
• Trenchless contractors need to use good
practices in verifying the location of buried
utilities prior to installation
QUESTIONS?????