6.2.4 Subsurface injection systems
Subsurface injection involves cooling and smothering a hot spot with a fluid suppressant
material. The suppressant smothers the hot spot by replacing or driving out the oxygen
source and/or cools the material by removing heat.
Injection methods should be used in conjunction with other control activities, such as sealing any potential sources of air ingress and managing the gas extraction system. The key issue for the success of this method, as with others, is the accuracy with which the hot spot depth and extent are known. The discussion below is based on limited data received from Fire Stop, a US landfill fires remediation company.
6.2.4.1 Shallow hot spots
The control of shallow hot spots with suppressant materials is best conducted at ground level after excavating the hot spot material. Suppression of the hot spot material can be achieved by using Compressed Air Foam Systems or Air Aspirated Foam Systems. When carried out in a properly bunded and controlled area, this method can prevent any run-off or unwanted leachate. The local fire brigade should be consulted prior to the use of these systems.