Page 22 - Tennessee 811 Magazine 2021 Issue 3

by John Jacobi
L Gaps in Damage Prevention
ast issue, I talked about using around for years (at least since the 80’s), GIS to collect, archive, access membership did not become mandatory and manage data regarding until the late 90’s and, in some states, existing underground even more recently. Let’s just say
utilities - things like buried pipelines, there is a lot of “stuff” that was buried
The instruments used to detect underground utilities each have their own unique capabilities. Soil type, moisture content, depth of burial, the presence of other underground utilities (abandoned or otherwise), and the composition of the object of concern (e.g., metallic v. non-metallic) all affect the accuracy of the marks. In urban settings, there are lots of things buried that could affect the accuracy of the marking.
In urban areas, steam may be used
to heat buildings. Live steam can be extremely dangerous. I am not aware of any requirements regarding call center membership for steam utilities.
Some water utility companies are
not members of 811 and as a result,
will not be notified by the call center. Rupturing even a relatively small water main can cause significant service interruption. I remember watching an HDD job in an urban setting. There was a geyser at literally every corner. That had to add a great deal of expense to the job. Fortunately, no gas lines were hit.
A big problem, in my experience, has been providing the call center faulty information about where the new construction is to occur. This may have improved since I retired but “white lining” (look it up) is almost never a bad idea.
I could go on, but you should get
the idea by now. One last caveat
- occasionally the line locators get overwhelmed with the number of tickets called in and can’t meet the regulatory deadline. My advice is to make the call as early as you can and still get the job done before the ticket expires. Use a design ticket when appropriate and use an emergency ticket only if there is an immediate threat to humans, the environment or the integrity of an underground utility.
When it comes time to start digging for whatever reason, there is no substitute for calling 811 and getting a physical locate. Even with a physical locate, it is IMPORTANT to make sure that the line of concern is the line that was located.
You cannot be too safe when dealing with buried utilities.
John Jacobi retired from PHMSA. For questions or comments, email: jjacobi@sbcglobal.net
buried electrical cable, and buried communications cable.
Why bother? Two big reasons: underground utilities require maintenance and underground
utilities MUST be dealt with if there
is any digging nearby. The need for maintenance should be obvious. How can something be maintained if you do not know where it is? Digging near existing underground utilities can be (is almost always) dangerous because interruption of electrical power or communications can delay emergency response or shut down essential services to schools, hospitals, police departments, etc., not to mention that damaging underground electrical lines and natural gas or hazardous liquid pipelines can be fatal to anyone nearby when the damage occurs.
Natural gas or hazardous liquid pipeline operators are required to participate in one-call systems. Most,
if not all, operators of underground electrical systems and underground communications systems (copper or fiber optic) also participate in one-call systems. Dial 811, answer the questions, wait the required time (usually at least 2 days unless its an emergency), obey the marks, and get on with the job. Easy. Right? Not so fast. Every state and even some cities have their own statutes and regulations. It is important that the applicable rules be followed closely. Things like wait time, depth
of burial, and tolerance zones are all very important. Nobody wants to have an accident but if one occurs and the “I”s have not been dotted and the “T”s not crossed, things could get far more complicated than they otherwise would be.
What is missing? Lots of things.
First, while one-call centers have been
(pun intended) before call-before-you- dig became the law of the land. The accuracy of the old maps may leave a great deal to be desired.
In my experience, depth of burial is a real concern. State and local building codes have requirements for depth of burial. Would you bet your life that the wire you are worried about is actually 24” below the surface? The federal Pipeline Safety Regulations (PSRs - 49 CFR Parts 190 - 199) burial requirements are in the construction sections. With a few exceptions, PSR pipelines do not have to be buried at all and, even if they are buried, the depth of burial does not have to be maintained.
Different types of instruments are used to locate underground utilities. Some are more accurate than others. All must be maintained and calibrated as well as operated by someone trained for that particular instrument.
Sewers are a particular problem.
Many natural gas distribution lines
are installed by horizontal directional drilling (HDD). Many sewers are clay tile or PVC (i.e., non-metallic) and difficult to locate. HDD will go right through a clay tile or PVC. This is called a cross-bore and has happened with both replacement lines and
new construction. The gas will be connected, and everything will be fine
- until the sewer gets clogged and a plumber runs a roto rooter through the sewer and severs the gas line. Natural gas is lighter than air and rises through the sewer line (sewer lines slope downward from the house or business) to the house or business. The gas
will accumulate in the building until
a spark sets off an explosion. This is still happening - not often, but still too often.
20 • Tennessee811 2021, Issue 3