Your decommissioning cost is largely fixed before the plant stops running

Owners typically engage a decommissioning contractor after final shutdown, treating the plant's condition at that point as a given. It is not a given. It is the result of choices made in the preceding weeks, and those choices have a larger influence on total decommissioning cost than the competitive tender that follows them.

What the final operating weeks determine

• Whether vessels and lines were drained and purged while process heat and pressure were still available to assist — or must now be cleaned cold, which is slower and generates more waste
• Whether residual inventory was consumed down or left in situ, which converts product into hazardous waste at a stroke
• Whether isolation points were left accessible and identified, or buried behind insulation nobody will remove until a contractor is paying people to find them
• Whether the as-built record was updated at final shutdown, when people who know the plant are still employed there
• Whether spares, catalyst and reusable equipment were separated while their provenance was still known

The catalyst example

On a chemical facility we assessed, a reactor was shut down with catalyst in place because removal was scheduled to the decommissioning contractor. By the time that contractor mobilised eleven months later, the catalyst had degraded past the point where the supplier would accept it for reprocessing. It became hazardous waste requiring licensed disposal.

The difference between reprocessing credit and disposal cost on that single item exceeded the entire cost of the mobilisation that would have removed it during shutdown.

The recommendation

Engage decommissioning engineering before the shutdown decision is finalised, even if the execution contract will be tendered later and elsewhere. A short advisory engagement that shapes how the plant is left will typically pay for itself many times over — and the window closes permanently the day the plant stops.

The cheapest decommissioning work is the work you do while the plant can still help you do it.