Wednesday marks six months since natural gas fires and explosions erupted across Lawrence, Andover and North Andover, wreaking havoc on the communities and leaving thousands of homes without heat or hot water for months. The last six months have been busy as residents and businesses try to recover and lawmakers and the courts look to hold someone accountable for the tragedy.

Here’s an update on what’s happened so far, and what’s still coming:

Temporary Housing

Many residents returned home in the days after the incident, but without their natural gas heat restored, it became more and more difficult to stay there as the weather got colder. More than 2,000 people were placed in temporary housing — including in trailers and hotel rooms. Most were back home by mid-December. But even now, six months later, Columbia Gas says 10 families are still in temporary housing.

Appliance Replacement

Columbia Gas replaced more than 18,000 new appliances, like furnaces and hot water heaters. Environmentalists tried to push for more energy-efficient appliances to replace the damaged ones and raised larger environmental and safety issues surrounding the use of natural gas. In an effort to restore service more quickly as it got colder, the company chose to repair some damaged appliances, rather than fix them. They plan to start replacing that equipment beginning this spring.

Pipeline Restoration

Three months after the disaster, Columbia Gas announced their restoration of gas service to roughly 10,000 homes and businesses was “substantially complete.” Roughly 4 percent of homes remained without service at that point because, the company said, those households chose to "self mitigate."

Columbia Gas replaced about 44 miles of gas main lines and more than 5,000 service lines. The overall effort took more than 5,000 workers.

Financial Claims

The crisis was a financial burden for families and businesses, and the utility says it has now settled almost 2,400 claims, paying out $92 million. There are about 800 active claims left, including about 200 business claims.

But Lawrence Mayor Dan Rivera says the utility’s not doing enough to pay people back for what they lost, including small businesses that were shut down for a while.

“What folks in this time period need to go back and really check out is, 'Have I really been made whole?' And, 'Do I need to go back and make sure my claim is being processed appropriately?' And to keep fighting it," Rivera said. "Don't let them shut your claim down. And understand that this is a long-term process. I think that Columbia Gas ... expects that every day they go without paying a claim, that that person might decide not to pursue the claim anymore.”

Columbia Gas spokesman Scott Ferson said part of the challenge of settling the remaining claims is that some businesses haven’t been able to provide the right kinds of documents to prove how much they lost by being forced to close their doors.

"You know, there are some unique businesses out there," Ferson said. "Record keeping can be spotty, based on how large or small the business is. And so, I think those kind of fall into a little bit of a more difficult of a category to be able to show the documentation, to be able to settle. But we're trying to figure out how to do that."

Ferson pointed out that on top of a $10 million donation for general disaster relief, Columbia Gas donated another $10 million to a community fund dedicated to business recovery efforts in the Merrimack Valley. The community foundation overseeing that fund said they’ve identified 837 impacted businesses, and they’ve provided services like marketing, accounting and staffing to about 220 of them so far.

Lawsuits

About a dozen class action lawsuits were filed against Columbia Gas and its parent company, claiming the company was negligent. Some are on behalf of business owners who lost income, and some are residents whose property was damaged or who say they weren’t able to work or that they were traumatized by the explosions.

In initial responses, the company has basically said it takes responsibility for the damage that was caused — but they also say they’re not liable for indirect damage, which will be a subject of the lawsuits.

There are also two wrongful death suits that have been filed. One is from the family of Leonel Rondon, who died when a chimney from an exploding house fell on the car he was sitting in. The other was filed by the family of North Andover resident Kenneth DeVeau, who was medically frail and went into cardiac arrest in an evacuation center. He went into a coma and died more than a week later.

The Investigation

A preliminary report from the National Transportation Safety Board said a crew of contractors was working on replacing old, cast-iron natural gas pipe, and mistakenly left a gas pressure sensor on a pipe they’d taken out of service. When that sensor read that the pressure had dropped, it caused the system to flood with gas, over-pressurizing the lines and sending gas rushing into people’s homes.

The NTSB said that the utility could have easily prevented the natural gas fires and explosions. The agency said Columbia Gas' use of work plans prepared by a "field engineer" — who is not a licensed professional engineer — is partly to blame for the accident. It urged the state to adopt new safety protocols.

Federal prosecutors also opened a criminal probe into the incident.

Pipeline Regulations

On the state level, natural gas infrastructure safety became a flash point of this fall's gubernatorial election. After his reelection, Gov. Charlie Baker signed a new law, as the NTSB had recommended, requiring a professionally-licensed engineer to be present when gas work is being conducted.

On the federal level, WGBH News discovered Columbia Gas and its parent company have a history of delays and noncompliance with federal reporting requirements.

Members of Congress held a Senate field hearing about pipeline safety in Lawrence in November, where senators criticized the utility's response, as well as the lack of new safety regulations introduced by the Pipeline and Hazardous Materials Safety Administration, or PHMSA. But a member of the advisory committee that recommends new regulations to PHMSA told WGBH News that they're hamstrung by a provision in the federal Natural Gas Pipeline Safety Act that requires them to consider if the costs of new regulations are justified by its benefits. The Pipeline Safety Act is up for renewal this year, and Sen. Edward Markey told WGBH News that he'd like to see that provision changed.

Emergency Response

Looking back, the fire chiefs of all three communities described a chaotic scene unlike anything they'd ever seen.

After complaints from those fire chiefs, Columbia Gas agreed in December to notify local fire departments about potentially dangerous gas leaks in the Merrimack Valley immediately, a change from their previous procedure. Massachusetts state law requires gas utilities to notify the local fire department of gas leaks that are classified as a grade one leak, which means they pose a hazard to persons or property, but doesn't specify when they must do so. Columbia Gas had been sending the local department an email the day after a potentially hazardous leak was fixed, much to fire chiefs' frustration.

Overcoming Anxiety

The fires and explosions rattled nerves in the communities.

“I haven’t been the same,” Katherine Reyes of South Lawrence told WGBH about a week after the disaster. “I haven’t been able to sleep for days. I finally slept, like for a couple of hours yesterday at my mom’s. Going back home feels like — it doesn’t feel safe.”

Six months later, that anxiety is still present for some.

“Obviously when people are hearing sirens or any clicks with the stoves — a lot of people tell me this — they just feel like they're afraid things are going to blow up," Ana Javier, a substance abuse prevention coordinator from Lawrence, said this week. "In our city, I think a lot of people are saying they're just happy that nothing worse happened, and they seem to be satisfied with a lot of that. But at the same time, they're frightened, because we really don’t have all the clear information, just yet.”