Natural Gas System Rebuild
Why are we Rebuilding the Gas System?
Hurricane Damages Drive Rebuild
• Widespread flooding after Hurricane Katrina inundated Entergy New Orleans’
gas system with corrosive saltwater. After the flooding, more than four
million gallons of saltwater was drained from the system.
• Last winter, about 2 percent of our customers experienced reliability issues
related to a small amount of water remaining in the system. But over time the
corrosive effects of the saltwater will degrade the system’s piping and cause
service problems and interruptions.
• The phased-in approach comes as the company recognizes that flood-induced
corrosion could impact various areas of the gas system differently over time
and that the repopulation of the city could require the company to target new
areas not evident today.
Less Vulnerable to Flood Damage
• A high-pressure gas system is less vulnerable to future flooding events
because the water is unable to enter the system. A gas system’s ability to
withstand flooding is measured by “water columns.” A low pressure system (like
that in New Orleans now) would require a column of water 7 inches to inundate
a break in the pipe. A high pressure gas system, like the system being
installed in the city, would require a water column of 215 feet to infiltrate
the system.
• If the high-pressure system experiences a Hurricane Katrina-type inundation,
it would take only weeks to dewater the system instead of months and would
eliminate reliability problems caused by residual amounts of water in the
system.
• The new high-pressure system will be rebuilt with high-density polyethylene
gas pipe (HDPE), which is virtually impervious to saltwater corrosion compared
to cast iron or steel traditionally used for gas systems.
Reliability and Safety Benefits
• The new system configuration introduces additional redundancies to ensure
reliable delivery of gas to customers, thereby reducing the scope of outages.
• Disruptions to the flow of gas can be isolated and confined more easily,
keeping the flow of gas available to more customers in an affected area.
• In the event of a leak, HDPE repairs are performed quicker than a steel/cast
iron system that requires welding and cathodic protection performed under the
street.
• A new safety feature is the “excess valve” included in each customer service
line. This new feature will automatically shut off gas flow if the customer’s
service develops a leak or some other disruption.
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