Step 2 of the THIRA process involves the further development of risks previously

Step 2 of the THIRA process involves the further development of risks previously identified (in Step 1) by providing context descriptions (Part A) and estimating impacts (Part B) using the Graniteville, SC train derailment/chlorine release scenario as the basis. You must do both parts to successfully complete Step 2 of the THIRA class project.  
https://www.transportation.gov/highlights/disaster-recovery/train-wreck-and-chlorine-spill-graniteville-south-carolina
https://www.fema.gov/sites/default/files/2020-04/CPG201Final20180525.pdf