When a freight car filled with sodium chlorate struck an adjacent tank car while moving through a rail yard in Massachusetts, it caused the release of up to 20,000 pounds of the chemical. Because the freight car was moving, it subsequently spread the substance over a span of more than 2,000 feet — through the rail yard and near a neighboring, active Massachusetts Bay Transit Authority (MBTA) commuter rail line. About a dozen homes were evacuated while state and local hazardous material clean-up crews, firefighters and police moved in to contain the spill.

Sodium chlorate is a chemical compound used most commonly as a main component of chlorine dioxide, today’s most predominant bleaching agent. The compound is a strong oxidizer and therefore carries a risk of fire and explosion when mixed with other substances, especially organic materials. Like many similar products, sodium chlorate is transported across the U.S. primarily via rail.

Rail yard workers knew they needed to act fast to report the spill and begin cleanup. Among those notified were local police and fire departments and the Massachusetts Department of Fire Services’ Hazmat Response Team, Massachusetts Department of Environmental Protection (MassDEP), and the U.S. Environmental Protection Agency.

Assessment and Response

The most immediate fire-related concern was the possibility of the compound reacting with materials beneath and adjacent to the railroad tracks — including creosote-treated wood railroad ties, leaves, wind-blown debris and other organic matter — which could have caused a fire. Such an event in the release area could have damaged the railroad tracks, hundreds of staged railcars, adjacent buildings and the MBTA rail line. Upon arriving on scene, the local fire department became cognizant of these risks and contacted additional state and local public-safety and environmental-protection authorities. An action plan then was developed in accordance the Massachusetts Contingency Plan, which regulates the cleanup of oil and hazmat releases.

The first step was to recover the bulk of the visible, crystalline sodium chlorate quickly before it could initiate a strong oxidizing reaction. Personnel attempted to segregate the chemical from organic matter, but in some instances this was impossible, as the sodium chlorate was mixed with oil-impacted soil, or embedded in cracks and fissures in oil- and creosote-impacted railroad ties.

The sodium chlorate recovered from the railroad tracks was staged in waste packs — triple-lined with polyethylene — that were ready for shipment pending determination of a suitable disposal facility. Because of concerns regarding the presence of organic matter that could not be separated from the sodium chlorate, the containerized waste was staged in a remote area at the rail yard. Within 48 hours of the initial release, the staged-waste sodium chlorate reacted and caught fire; local fire departments quickly responded to the site to extinguish the fire.

Because the relatively small quantity of sodium chlorate remaining on the railroad tracks could not be physically removed — due to its location beneath the tracks, within the stone ballast and within cracks in railroad ties — approval was sought from MassDEP for on-site neutralization of the residual sodium chlorate. In the meantime, small fires occurred along the tracks as residual sodium chlorate reacted with organic matter. Therefore, the local fire department required that a fire watch be maintained around the clock. The fire watch was established and initially was manned by the local fire department, and then by personnel from the rail company. Flare-ups were extinguished quickly with water.

After the initial fires, water routinely was used to saturate the release area during periods of hot weather, and no further substantial incidents occurred. The fire watch was terminated at the completion of the sodium chlorate neutralization.

A team of consultants, working with MassDEP, determined that the application of a 5% sodium thiosulfate solution was the best approach for neutralizing the impacted soil and other materials in the rail yard. After application, remediation crews monitored the neutralization process by measuring the change in temperature as well as oxygen, chlorine and sulfate levels. Multiple applications of the solution were necessary to ensure full neutralization, as confirmed by analysis of field samples by a certified laboratory.

Conclusion

Due to the spill’s potential impact on the rail yard, hundreds of rail car, and the adjacent commuter rail line, this high-profile release required rapid initial response from local fire responders and subsequent thorough remediation by qualified environmental specialists working with local, state and federal authorities.

Because of this well-coordinated response, the gross contamination was removed swiftly enough to prevent any strong oxidizing reaction and any associated damage to the track and hundreds of staged railcars. As a result, regulatory closure was obtained from MassDEP in short order, and the commuter rail and freight lines quickly were re-opened.

Geoffrey A. Brown has been a vice president with ENPRO Services since 1998, and specializes in the assessment and remediation of complex oil and hazmat release sites. He holds a Ph.D. in soil science from Cornell University, an master’s degree in environmental pollution control from Penn State University, and a bachelor’s degree in environmental science from the University of New Hampshire.

Related Stories:

• TRANSCAER Teaches First Responders Abou Hazmat Transport
• Mutual Aid: Ride the Rails