Contamination Control at the Decon Line
Workers are removing drums and visibly contaminated soil at a former plating shop. Contaminants of concern include hexavalent chromium and cadmium. The decon line is set up as: dirty side at the exclusion-zone boundary → boot wash → outer-glove rinse → suit spray-down → clean side. Two workers are sharing one boot-wash tub and one rinse bucket. At the end of the shift, a worker walks from the boot wash directly to the clean side in the same boots, then sits on the clean-side bench to remove them. The health and safety officer notices that the rinse water has not been changed since morning and that the clean-side bench has visible mud on the seat.
1. Identify the contamination-control failures in this decon line and explain why each matters for a chromium/cadmium site.
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Failures:
- Shared, unchanged wash and rinse water. Once loaded with soil and metals, the "rinse" becomes a contamination source - workers are re-contaminating gloves and boots. Chromium and cadmium are not destroyed by water; the rinse must be changed based on use and visibly dirty water is not a rinse.
- No step between boot wash and the clean side. The worker crossed the boundary in the same boots, carrying contamination onto the clean side. Boots should be removed at the boundary (or dedicated clean-side footwear used), not worn across.
- Sitting on the clean-side bench in contaminated boots. The bench is now a contaminated surface, and the worker's contaminated boots are in contact with it - the clean side is no longer clean.
- No separation of the two workers' decon. Sequential, controlled decon prevents cross-contamination; two people at one station at once defeats that.
Why it matters here: hexavalent chromium and cadmium are both associated with serious health effects, and the whole point of decon is to keep contamination from leaving the exclusion zone and from being carried home. A decon line that re-contaminates workers provides false assurance.
2. Redesign the decon sequence and the boundary so contamination cannot cross it.
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A workable sequence (dirty → clean):
- Tool/drum drop at the exclusion-zone boundary.
- Gross decon: boot wash (fresh water, changed as needed) → outer-glove wash → suit spray-down, done one worker at a time.
- Boot removal at the boundary - boots stay on the dirty side or go into a designated container; worker steps across in clean footwear or on a disposable barrier.
- Suit removal (roll inside-out) on the dirty side of the boundary.
- Glove removal last, then hand wash.
- Clean side: only clean footwear and clean clothing; bench wiped and covered, and no contaminated boots on it.
Controls: a physical boundary (curb, tape, or step) that is visibly dirty/clean; separate containers for wash and rinse water; a schedule for changing water; a decon attendant to enforce the sequence; and periodic wipe sampling of the clean side to verify the boundary is holding.