Construction workers remove part of the road along Shady Oaks Drive near the intersection with Woodrow Lane in March. Atmos Energy was overseeing the construction because of a high-pressure main pipeline located underneath the road.

A map recently released by Atmos Energy shows miles of steel pipe remain in service as Denton’s natural gas utility mains, concentrated mostly in the city’s older neighborhoods and on both university campuses.

Atmos voluntarily released the map to the Denton Record-Chronicle after the newspaper made an open records request to the city government for its copy of the system map. Earlier this year, Atmos released a similar map of the Dallas system after pressure from news media and the public. In February, an Atmos steel pipe leaked, triggering a natural gas explosion in northwest Dallas that killed a 12-year-old girl.

In Denton, the natural gas utility system is no stranger to leaks. A previous Record-Chronicle investigation found that in the past few years, crews had repaired leaks in natural gas mains around the city once a month or more.

When the utility system was built, steel and cast-iron pipe was considered state-of-the-art. But the metal pipe has not aged well, with some corroding and leaking. North Texans have learned the hard way that when it rains, prairie clay soils can create new paths for leaking gas to migrate and collect, rather than disperse in the air.

Sometimes the mercaptan odorant added by the utility stays behind in the soil, too, leaving the methane in its odorless, colorless state, which makes it harder to detect.

The map shows that Denton’s system has no cast-iron pipe, the type Atmos plans to completely replace in the Dallas area by 2023. The company began replacing steel and cast-iron pipe in North Texas seven years ago. Several explosions around the region between 2006 and 2009 killed four people in their homes and injured several others, triggering the replacement plan.

However, there is no specific requirement by any state or local officials for the company to replace the aging pipe before a certain deadline.

Atmos spokeswoman Jan Rugg said a report detailing the nature of steel lines in Denton and when some of them would be replaced was due next week.

She declined to comment further or answer additional questions.

Steel pipes are most often found in those Denton neighborhoods that were built from the 1940s to the 1970s. Steel gas mains remain predominant in central Denton neighborhoods, along and within the University of North Texas and Texas Woman’s University campuses, and in some older neighborhoods, including Southeast Denton, Denia, Southridge, Northridge and the northeastern neighborhood affectionately known as Idiot’s Hill.

In newer, outlying neighborhoods, particularly in far southern Denton, gas mains are made of polyethylene. Polyethylene is thought to be more durable, and able to better expand and contract than metal pipe depending on the weather.

Atmos officials have said the company’s Mid-Tex division has spent $3 billion replacing pipe so far and expects to spend another $3 billion over the next five years. Mid-Tex serves 1.6 million customers in 514 cities from the Red River south to San Angelo, Kerrville and Bryan.

PEGGY HEINKEL-WOLFE can be reached at 940-566-6881 and via Twitter at @phwolfeDRC.

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