Прошу помочь уточнить фразу из документа PRELIMINARY TECHNOLOGICAL BLOCK IDENTIFICATION (пр-во аммиака)

In this project, only ammonia was considered as combustible material for block category calculation. As an accident scenario, the “pool fire” model was used. The applied model assumes:
- a big rupture in ammonia vessel
- a big leak and spillage of liquid ammonia to the surrounded area
- evaporation of spilled ammonia
- combustion of evaporated ammonia
- the pool fire area is *given by the emergency pit dimension*

Не совсем понятно: given by the emergency pit dimension

Спасибо.