This Week’s Subject: Tolerance Zone

Question: Can you explain “tolerance zone” when an excavation is performed near a pipeline?

Answer: The tolerance zone represents the approximate location of a marked underground utility facility (e.g., gas pipe), which contains the pipe width plus 18 inches on each side of the markings. A qualified locator marks the facility with yellow paint and/or flags. The locator also marks the type, diameter size, and any other marking requirements.

Excavation within the tolerance zone requires extra care and precaution (hand digging or vacuum excavation methods). Never use powered equipment, such as a backhoe, in the tolerance zone until you verify that locate marks are accurate! Dig safely by visually inspecting the excavation in progress until it’s clear of the existing marked facility. The image below illustrates the tolerance zone.

Tip: Tolerance zone requirements vary from state to state. Refer to the applicable state code regulation. This practice is not intended to preempt any existing state/provincial requirements that currently specify more than 18 inches.

This Week’s Subject: Natural Gas Odorant

Question: Joe, how do utility companies add odorant to natural gas?

Answer: Natural gas is odorless in its natural state, but it’s artificially odorized by an organic sulfur compound called mercaptan. Gas companies add mercaptan to the natural gas to give it a distinct, identifiable odor for customer recognition. This minimizes risks to public safety and complies with federal regulatory requirements.

A distribution line must be odorized so that at a concentration in air of 1/5 of the lower explosive limit (LEL), the gas is readily detectable by a person with a normal sense of smell. This is the equivalent of 1% gas in air or 20% LEL. Each operator must conduct periodic sampling with an air dilution instrument that can determine the percentage of gas in air at which the odor becomes readily detectable.

Tip: Odorant is the customer’s leak detector. It provides the public with an effective warning device about a possible gas leak problem. When you smell gas in or around your home, call the gas company to come out and investigate. Safety must never be overlooked!

This Week’s Subject: Gas Appliances and Carbon Monoxide

Question: Joe, if natural gas is safe and clean, how do gas appliances cause carbon monoxide?

Answer: When a gas appliance (e.g., furnace, water heater, range) is producing yellow flames, it’s not operating efficiently or not vented properly. When something obstructs the flame or there’s a lack of sufficient oxygen supplied, the result is incomplete combustion. This can produce carbon monoxide.

Examples: In a furnace, when a rust patch has fallen onto a burner head, this causes the flame to impinge on the heat exchanger and burn yellow. All appliance burners should produce blue flames, which indicate adequate combustion air and make-up air for safe, efficient operation.

Sometimes poor venting, not the appliance itself, is the problem. Examples are improper installation, cracked or rusted-through vent pipes, loose bricks blocking a chimney, or a blocked flue pipe due to a bird’s nest. When combustion byproducts cannot vent properly, carbon monoxide spills back into the living space and creates a dangerous situation.

Tip: Ensure that a qualified professional checks all natural gas appliances for proper operation and venting. This includes a thorough visual inspection of the condition of vent piping. A good cleaning and proper burner air adjustment can correct some deficiencies. A carbon monoxide (CO) detector should be installed on every floor of your home for safety. Remember, carbon monoxide is odorless and colorless, but at high levels it can kill a person in minutes.


This Week’s Subject: Third-Party Damage

Question: Joe, I’ve heard damage to underground gas pipes referred to as “third-party” damage. What is third-party damage?

Answer: With respect to underground damage to gas-related facilities, the facility owner/operator is the first party. Any contractor working for the facility owner or operator is considered the second party. All other excavators (e.g., city water and sewer contractor, residential fence installer, other utilities and contractors) are referred to as third parties. So when an underground facility is hit and results in damage, this is referred to as “third-party” damage.

Tip: It’s important to ensure that damage prevention awareness programs are in place to educate company personnel, contractors, and the public about safety. This includes using the One-Call Center initiative and industry best practices to prevent any hits on all utility facilities. A written damage prevention program is a U.S. DOT regulatory requirement!

Calling 811 (the One-Call number) before digging is an essential first step in preventing damage to underground facilities, service interruptions, and potential hazards to the community. One-call centers are dedicated to protecting the public and construction personnel who work around utilities, as well as safeguarding the underground infrastructure of pipe mains and service lines.


This Week’s Subject: Yellow Warning Tape

Dear Joe: Is the yellow warning tape a regulatory requirement for plastic pipe installation? I’ve seen jobs where it’s not installed.

That’s right. While locate wire for direct buried polyethylene (PE) pipeline is required by regulatory code, yellow warning tape is not. But most companies install the warning tape approximately 12 inches above the PE facility for open trench installations. Yellow warning tape displays a message (for example, “Caution: Gas Line Buried Below”). The warning tape serves as a first alert to an excavator to proceed with caution while digging to prevent third-party pipe damage.

Tip: And those jobs where you’ve seen no warning tape installed? You may be referring to horizontal directional drilling (HDD) installations. It’s not possible to install the tape 12 inches above the PE pipe because HDD involves installation through a single bore hole. Also, warning tape would not be needed for PE pipe installed inside steel or cast iron casing pipe-but it could be installed at any exposed PE tie-in points.

Dear Joe – You’re from Chicago –  Do you think the Cubs have what it takes to win the pennant this year?

Tom Wivinis
WEC Energy Group

Dear Tom – Of course they do! Their 100 year (or more) development plan is right on track!