Feb. 3 — A Norfolk Southern freight train carrying hazardous materials derails in East Palestine, Ohio.

Feb. 4 — The EPA says it is responding to the derailment site. EPA begins air monitoring for volatile organic compounds (VOCs) including vinyl chloride and butyl acrylate, which were on the train and can be harmful to people, according to the agency.

Contractors with the EPA install booms and underflow dams to restrict the flow of contaminated water as well as contain and collect floating product to mitigate any possible impacts to the Sulphur Run and Leslie Run streams, they say.

Feb. 5 — Gov. Mike DeWine activates the Ohio National Guard to assist local authorities.

Officials issue a shelter-in-place order for the entire town of roughly 5,000 people. An evacuation order is issued for the area within a mile radius of the train crash near James Street, due to the risk of an explosion.

EPA community air monitoring readings do not detect any contaminants of concern, they say. Norfolk Southern’s contractor continues to conduct air monitoring, the agency says.

The National Transportation Safety Board is on scene to gather evidence and asks the community to submit photos or videos of the incident.

NTSB conducts a one-mile walkthrough of track outside the hot zone and identify the point of derailment. Graham says the preliminary report is expected in four to eight weeks.

NTSB conducts a one-mile walkthrough of track outside the hot zone and identify the point of derailment. Graham says the preliminary report is expected in four to eight weeks.

Aeration pumps begin operating at three locations along Sulphur Run and the confluence with Leslie Run. Aeration helps treat contamination by injecting oxygen into the water. The East Palestine water treatment plant confirms there was no adverse effects to the plant, the EPA says. EPA and Norfolk Southern contractors collect surface water samples for analysis.

Feb. 6 — To prevent an explosion, Norfolk Southern launches a controlled burn of rail cars containing vinyl chloride. EPA air monitoring detects particulate matter resulting from the fire, the agency says.

In addition to real-time air monitoring, the EPA says it is collecting air samples in conjunction with the 52nd Civil Support Team — a specialized unit of the Ohio National Guard — for analysis.

The Ohio Environmental Protection Agency leads efforts to investigate and address possible impacts to Sulphur Run and Leslie Run, the agency says.

Feb. 7 — Residents in the area are told they may smell odors coming from the site because the byproducts of the controlled burn have a low odor threshold – meaning people may smell these contaminants at levels much lower than what is considered hazardous, the EPA says.

The EPA continues to perform air monitoring and work with Norfolk Southern, health departments and other responding agencies to develop procedures for safely reoccupying the evacuated areas.

The 52nd Civil Service Team conducts air monitoring in three public administration buildings and collects air samples from each building, according to the EPA.

The EPA says it is investigating a complaint of odors from the Darlington Township, Pennsylvania, fire station. A team with air monitoring equipment goes to the station, where it does not observe any contaminants above detection limits.

Feb. 8 — The evacuation order is lifted, five days after the derailment, after water samples are analyzed overnight. The results lead officials to deem the water is safe, East Palestine Fire Chief Keith Drabick says at a news conference.

The EPA and Ohio EPA find spilled materials in Sulphur Run, the EPA says. Oily product is leaking from a tank car and pooling onto the soil. Norfolk Southern is notified of the spill and begins removing the product using a vacuum truck.

A local couple and business owner file the first-class action lawsuit against Norfolk Southern, CNN reports. The suit accuses the rail company of negligence, stating it failed to exercise reasonable care for residents, with businesses adversely affected by the derailment and chemical spill.

Feb. 9 — EPA continues stationary and roaming air monitoring surrounding the derailment scene.

Despite officials deeming the air and water samples safe, some residents still have concerns. Residents are encouraged to get their homes deep cleaned and seek medical attention, if necessary, officials say at a press conference.

The EPA works with Ohio EPA to investigate remaining soil contamination and any impacts to surface water, the agency says. EPA collects samples of spilled material near the derailment site and in Sulphur Run.

Officials say schools will remain closed until further notice from the superintendent.

Mayor Trent Conaway ensures that the school building will be scrubbed “head to toe” and air tested before any child walks back into the building.

Feb. 10 — Some residents say when they returned to their homes in East Palestine, within a half hour they developed a rash and nausea.

EPA is assisting with voluntary residential air screening appointments offered by Norfolk Southern, the agency says. Crews have screened indoor air at a total of 46 homes. There are over 400 requests for indoor air screening remaining.

To increase the rate of screening, Norfolk Southern – with EPA assistance – brings more teams and equipment to East Palestine, according to the EPA.

Ohio EPA leads efforts to investigate and remediate impacts to water, the agency says. Samples from Sulphur Run and other points of nearby water streams are taken for testing.

Norfolk Southern contractors install a dam and a water bypass at Sulphur Run to prevent further contamination of downstream waters, the EPA says.

Feb. 11 — EPA issues a general notice of potential liability letter to Norfolk Southern to document the release or threat of release of hazardous substances, pollutants or contaminants to the environment. The letter outlines EPA cleanup actions at the site and the potential to hold the railroad accountable for associated costs.

EPA continues to assist Norfolk Southern and Columbiana County Emergency Management Agency with voluntary residential air screening, the EPA says.

Feb. 12 — EPA posts a document from Norfolk Southern listing the cars that were involved in the derailment and the products they were carrying.

Air monitoring throughout East Palestine continues, the EPA says. Monitoring since the fire went out has not detected any levels of concern that can be attributed to the incident.

Local schools and the library are screened, the EPA says.

Feb. 13 — Reentry air screenings are underway. Community air monitoring will continue operating 24 hours a day.

EPA deploys two more Summa air sampling canisters for continuous sampling.

EPA discontinues phosgene and hydrogen chloride community air monitoring. After the fire was extinguished on February 8, the threat of vinyl chloride fire producing phosgene and hydrogen chloride no longer exists. EPA will continue 24-hour community air monitoring for other chemicals of concern.

Feb. 14 — No vinyl chloride is detected in any of the down-gradient waterways near the train derailment, Tiffany Kavalec, Chief of the Division of Surface Water at the Ohio EPA says. Active aeration of the waterways near the derailment continue and even though some waterways remain contaminated, the agency says they are confident the contaminants are contained.

About 3,500 fish across 12 different species have died in Ohio waterways, the Ohio Department of Natural Resources says.

Feb. 15 — Residents pack a high school gym in East Palestine for a meeting with officials to discuss the current state of their community, CNN reports.

The event hosted by East Palestine officials was supposed to include officials from Norfolk Southern. But the company, which said it had hoped to provide updates on cleanup efforts and results from air and water tests, backed out earlier in the day, saying it was concerned about a “growing physical threat to our employees and members of the community around this event,” stemming from its belief that “outside parties” would participate.

Instead, local leaders take questions from emotional residents who expressed distrust of officials’ accounts and anger – including at the transport company’s decision to skip the event.

Norfolk Southern provides bottled water at their family assistance center, the EPA says.

Regional Administrator Debra Shore attends a community meeting alongside EPA on-scene coordinators and state and local officials to hear residents’ concerns.

Gov. DeWine issues a press release stating the municipal water is safe to consume. Test results from the village’s municipal well sampling showed no water quality concerns, the state says.

DeWine encourages those East Palestine residents with private wells who have not had their water tested to continue drinking bottled water “out of an abundance of caution.”

Norfolk Southern has not removed potentially contaminated soil from the site, new documents posted by the EPA show. Norfolk Southern tells CNN it continues to work to clean up the site, including the removal of soil.

“Contaminated soil will continue (to) leech contaminants, both up into the air, and down into the surrounding ground,” Richard Peltier, an environmental health scientist at the University of Massachusetts at Amherst, tells CNN in an email. “Every time it rains, a flood of new contaminants will enter the ecosystem.”

Feb. 16 — EPA Administrator Michael Regan arrives in East Palestine to assess the ongoing response to the Norfolk Southern train derailment. The administrator meets with city, state, and federal leaders involved in the response, hearing directly from residents about the impacts of the crisis and discuss EPA’s work.

DeWine asks the CDC for immediate assistance by sending expert medical assistance including doctors and professionals who can evaluate residents who are experiencing symptoms.

Feb. 17 — Gov. Mike DeWine says no derailment contaminants have been found in homes tested for air quality and that there is a section of Sulfur Run near the crash site that remains severely contaminated.

Requests for medical experts from the federal government have been granted and DeWine says officials should arrive next week to help prop up a clinic for patients.

Feb. 18 — Air monitoring and indoor air screening continue, according to the EPA. Municipal water samples show no water quality concerns, the agency says.

Emphasis is being placed on recovery of all pooled liquids, excavation of heavily contaminated soil, and removal of all remaining rail cars, according to the EPA. In order to capture any contamination leaving the site, Norfolk Southern establishes a containment area in a section of Sulphur Creek to divert all up-stream water around the containment area. The containment area has effectively cut off the introduction of additional contamination into Sulphur Run.

Feb. 19 — The village of East Palestine’s municipal well water sample results show no water quality concerns, the EPA says. The Columbiana County General Health District continues to sample private water wells. To date, 52 wells have been sampled, 49 in Ohio, and three across the border in Pennsylvania, the agency says.

Norfolk Southern continues scrapping and removing rail cars at the derailment location, excavating contaminated areas, removing liquids from affected storm drains and staging recovered waste for transportation to an approved disposal facility, the EPA says. Water continues to be diverted from the upstream wetland area to Sulphur Run.

Feb. 21 — The state opens up a health clinic for residents who worry their symptoms, such as trouble breathing, rashes and nausea, might be linked to the derailment.

CNN reports investigators are reviewing multiple videos of the train prior to it derailing. One video shows “what appears to be a wheel bearing in the final stage of overheat failure moments before the derailment,” the National Transportation Safety Board says in a statement.

The EPA announces its legally binding notice ordering Norfolk Southern to handle and pay for all necessary cleanup involved in the derailment.

As part of EPA’s legally binding order, the agency said, Norfolk Southern will be required to:

• Identify and clean up any contaminated soil and water resources,

• Reimburse the EPA for cleaning services to be offered to residents and businesses to provide an additional layer of reassurance, which will be conducted by EPA staff and contractors,

• Attend and participate in public meetings at the EPA’s request and post information online,

• Pay for the EPA’s costs for work performed under this order.

The order will take effect February 23. If the rail company fails to complete any actions ordered by EPA, the agency says it will immediately step in, conduct the necessary work and then seek to compel Norfolk Southern to pay triple the cost.

After the accusations, Norfolk Southern issued a statement to CNN:

“We recognize that we have a responsibility, and we have committed to doing what’s right for the residents of East Palestine,” the company said Tuesday.

“We have been paying for the clean-up activities to date and will continue to do so. We are committed to thoroughly and safely cleaning the site, and we are reimbursing residents for the disruption this has caused in their lives. We are investing in helping East Palestine thrive for the long-term, and we will continue to be in the community for as long as it takes. We are going to learn from this terrible accident and work with regulators and elected officials to improve railroad safety.”

The Pennsylvania Attorney General’s office says it will investigate the train derailment following a criminal referral it received from the state department of environmental protection, according to a statement from the office.

Gov. Josh Shapiro first mentioned the criminal referral when he was asked what non-financial actions are being taken.

In response to news about the criminal referral, a Norfolk Southern spokesperson said the company had no comment.

Feb. 22 — EPA Administrator Michael Regan threatens to fine Norfolk Southern if it fails to fully clean up after the mess the derailment left behind, he says, citing the agency’s authority under CERCLA – the Comprehensive Environmental Response, Compensation and Liability Act.

Regan summarizes the EPA’s demands to Norfolk Southern:

“Number one: They will clean up every single piece of debris, all of the contamination, to EPA specifications and satisfaction,” he tells CNN.

“Number two: They will pay for it – fully pay for it. At any moment, if we have to step in because they refuse to do anything, we will do the cleaning up ourselves. We can fine them up to $70,000 a day,” the EPA chief said.

“And when we recoup our total costs, we can charge them three times of the amount of the cost of the federal government. That is what the law provides.”