Plot plan

The plot plan is the facility's first and most consequential spatial decision. Drawn early and frozen early, it arranges the units and their separations, routes the main racks and roads, positions the flare, the control room, the substations and the fence — and in doing so it fixes a remarkable share of the project's cost (rack lengths, cable runs, earthworks) and of its risk profile, since inter-unit spacing, hazardous-area separation and emergency access are plot-plan facts before they are anything else. Spacing tables and siting studies from the safety disciplines are its governing inputs.

Its failure mode is its own success at freezing: the plot plan is set when equipment sizes are estimates, and late growth — the vendor's compressor package arriving a metre longer, the added exchanger, the future unit the business now wants — must be absorbed by a layout that has already spent its slack. Good plot plans budget that slack deliberately: space is cheapest on the day it is still paper.