Distance between sewage tank and factory building

I have a question: what is the required distance between a sewage tank (containing Class B flammable liquids, located 4 meters below the ground surface and covered) and a Class B factory building? Is there any specification addressing this? There’s another question: if a pump room is built on top of this sewage tank, and the location where the sewage pumps are placed does not allow them to be exposed to the elements, are there any requirements regarding spacing? The table in Article 3.2.11 of the \"Code for Fire Protection Design of Petrochemical Enterprises\" stipulates that the distance between wastewater treatment plants (uncovered oil separation tanks) and Class B factory buildings shall be 25 meters. The distance from the pump room is 20 meters. The fire separation distance for the oily waste tanks () in the wastewater treatment plant can be reduced by 25%. The fire separation distance for oil pumps within the wastewater treatment plant or in the pump room can be reduced by 50%. By a covered sewage tank, do you mean something specific? I’m not sure what you’re referring to Logically, sewage contains Class B flammable liquids; if the sewage tank is covered and properly sealed, it should be fine ； If the seal is not proper, vapors of flammable substances can easily form explosive mixtures with air, leading to fires and explosions when exposed to an open flame. If the sewage tank is not covered, the vapors of flammable substances can easily disperse, making it difficult for an explosive mixture to form.