1. The PHA team did not validate the assumptions in the PHA including accuracy of the SOP, conformance to the SOP, and control of process safeguards.
2. The residue treater layers of protection to prevent a runaway reaction were inadequate.
3. Previous PHA action items were not closed in a timely manner, including operator training and control of process safeguards.
4. The methomyl unit SOP was overly complex and not reviewed and approved prior to the methomyl unit startup. 5. The SOP did not include flasher tails methomyl concentration testing as required by the original construction process safety information package