A day before the first anniversary of the Merrimack Valley gas disaster, Columbia Gas announced plans to inspect 700 abandoned gas lines in the area most affected.

The lines were taken offline when the utility replaced its gas network in the Merrimack Valley last fall. Currently they have no gas running through them.

"These compliance checks are being conducted out of an abundance of caution and in order to verify that the work on these lines was done consistent with Massachusetts requirements," the company said in a statement released at 9 a.m. Thursday.

The abandoned gas lines are located in Andover, North Andover and Lawrence. The largest amount of abandoned gas lines, 411 lines, are located in Lawrence, according to officials.

Lawrence Mayor Daniel Rivera was not pleased to hear about the abandoned gas lines.

"I am super concerned. If they forgot to do this, what else did they forget to do?" Rivera said.

"Columbia Gas of Massachusetts announced today it will begin compliance checks on service lines abandoned last fall as part of the recovery work in the Merrimack Valley. Columbia Gas recently identified some instances of noncompliance with Massachusetts requirements related to the process of abandoning service lines, the inactive gas piping that connected a customer’s facilities to the old gas system."

"As a result, Columbia Gas is planning to verify the processes by which certain service lines were abandoned from the old gas system," according to the statement.

"The compliance checks will be conducted either inside or outside the customer’s home or business, depending upon the customer’s preference," according to Columbia Gas.

The company, in the statement, said the decision to check these lines came from "ongoing reviews of the gas system as part of Columbia Gas’ commitment to the Merrimack Valley."

"These compliance checks will not affect the new service lines that were installed in the fall, and therefore there will be no disruption to gas service for customers," according to the statement.

A year ago, on Sept. 13, 2018, thousands of businesses and residents were effected when the overpressurization of gas lines caused explosions and fires throughout the Andover, North Andover and Lawrence. Residents were forced to temporarily evacuate their homes and walk away from businesses.

A recovery process that spanned the past year cost roughly a billion dollars.

“We recognize that our customers have been through a difficult year as we conducted the recovery and restoration work in these communities. We understand that additional work may frustrate them, and we apologize,” said Mark Kempic, president and COO of Columbia Gas of Massachusetts, in the statement.

Kempic added, “We are conducting these compliance checks out of an abundance of caution. Our commitment to providing customers with safe and reliable gas service is at the forefront of the decision to conduct this review.”

This is a developing story. Check back to eagletribune.com for updates. A complete report will appear online and in print editions of The Eagle-Tribune.

Follow staff reporter Jill Harmacinski on Twitter @EagleTribJill.

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