For overfill scenario above, your evaluation team has identified the following possible risk reduction measures. Which one would you recommend as most effective? Explain basis for your recommendation.

a$.$ SIL$-1$ interlock with an analyzer to detect material in air inlet to building with automatic shutdown of ventilation system

b$.$ SIL$-2$ interlock involving redundant high$-$level detection with automated shut$-$off of transfer pump

c$.$ Operator sees material spilling into diked area and manually closes a fill valve according to a simple well documented procedure

Explain ALARP concept.