Site remediation methods usually include physical, chemical, and biological means. The remediation method type can be classified as active and passive. Active methods are methods that actively perform to remediate the pollution situation. Physical remedial methods include excavation, soil vapor extraction, groundwater pump and treat, dual-phase extraction, multi-phase extraction, high vacuum pump, air sparging, thermal, and granular activated carbon sorption. Soil excavation is good for a quick solution, particularly for sites soon to be re-developed. Groundwater pump and treat is one method to treat contaminated groundwater by pumping the water from the aquifer and treating the water using physical, mechanical, or other means such as chemical or biological methods on the surface. Soil vapor extraction uses vacuum pressure to extract volatile compounds from porous soil. The fundamental concept of a biological method for site remediation is to encourage bacteria and other microbes to destroy pollutants, or to let the living things "consume" the organic pollutant, which they use as their "food".