Success Story

Reducing Risk from Intentional or Accidental Chlorine Releases

The Department of Homeland Security (DHS) Science & Technology (S&T) Chemical Security Analysis Center's (CSAC) mission is to identify and characterize the chemical threat to the homeland. The CI is a technical trade association of companies that are involved in the production, distribution, and use of chlorine. Chlorine is highly toxic by inhalation. It is the most widely produced and transported toxic inhalation chemical in the US. Shipment is by 90-ton railcars, 20-ton tanker trucks, and truck-loaded palletized cylinders. Out of necessity, transport through densely populated areas often occurs. Chlorine has been recognized to pose a significant terrorism risk. Both CSAC and CI are involved in efforts to understand and minimize the risks posed by either the intentional or accidental release of chlorine.

In 2010 and 2015/2016 CSAC led the interagency/international Project Jack Rabbit field testing programs which saw the highly instrumented release of large quantities of chlorine, as would emanate from a rupture in a railcar or tanker truck. These tests were designed to improve modeling such that emergency response planning could be enhanced. The CI was a key participant in the field trials.

CRADAs (2013 and 2017) between CSAC and CI leverage data from each of the two field programs. CSAC modeling and analyses were utilized to inform industry and improve emergency response. The goal of the 2013 CRADA was the development of planning and response guidance to the chlorine industry via the CI publication “Pamphlet 74”. The goal of the 2017 CRADA is a revision of Pamphlet 74 based on the recently completed field tests.

Under the CRADAs, transportation scenarios were jointly examined by CSAC and CI, then modeled by CSAC to explore a range of release conditions and environments. The modeling was performed with improved fidelity enabled from the testing data, in particular, the mathematical depiction of source terms from large-scale releases. These modeling results were then utilized in CI’s “Pamphlet 74”.

CRADA Outcome

The collaboration between CSAC and CI is life-saving in that it has reduced the risk posed by the intentional or accidental release of chlorine. The CRADA is the mechanism by which DHS sponsored research into chlorine releases has been turned into a practical application and made available to industry and emergency responders.

Based on work under the 2013 CRADA, Pamphlet 74 “Guidance on Estimating the Area Affected by a Chlorine Release” was published by CI. This Pamphlet is now being further updated and revised through the 2017 CRADA, which makes use of the new 2015/2016 field test data. These most recent tests utilized chlorine releases up to 20 tons, which could result from an intentional or accidental breach of a tanker truck or railcar.

Pamphlet 74 is an essential industrial safety and emergency planning tool. It provides chlorine producers/users, local emergency planning committees, fire departments and municipalities the information and methodology necessary to estimate the area affected by a chlorine release and reduce the risk posed to life and health.

The scenarios developed under the CRADA explored areas of highest concern and uncertainty. The variables CSAC modeled included:

  • Release amounts (cylinders, tanker trucks, railcars)
  • Release rates
  • Meteorological conditions (wind, temperature, humidity, atmospheric stability)
  • Release environment (urban, rural). 

These modeling input parameters were derived directly from empirical data obtained from the chlorine release field experiments. Modeling output assessed the effects of chlorine releases on exposed populations and responders, resulting in the life-saving guidance published in Pamphlet 74.

In addition, the CRADAs resulted in direct industry participation and support in field testing and studies. The test vehicles and all of the test program’s chlorine and chemicals were provided by CI. Further, the CRADAs enabled CSAC to directly support numerous nationwide training, awareness, and risk reduction events sponsored by CI for its member companies.