inject the microorganisms and any supporting biomass or growth supplements into one or more of the injection wells 10 alternatively a mixing pump 40 may be placed within one or more wells 10 to facilitate mixing of the various reagents as illustrated various reagent s may be present in the form of a stock solution held within a holding tank 32 a variety of growth supporting biomaterials may be injected into the subsurface along with the consortium of microorganisms preferably the amount of an injected electron donor such as lactate should be at least 50 times greater in terms of electron equivalents compared to the electron equivalents needed for stoichiometric dechlorination when maintained at such levels it has been found that reduction of pce tce dce and vc to an inert gas such as ethene or ethane can be accomplished in situ in the reactive zones 50 the bacterium consortium described herein as pta 8259 was enriched from a subsurface material collected from a chloroethene plume the mixed culture consortium can be cultured in a defined synthetic medium under anaerobic conditions a novel consortium of microbes was subjected to various tests and procedures for the determination of identifying characteristics the bacteria mixed culture was deposited under the budapest treaty with the american type culture collection atcc p o box 1549 manassas va 20108 usa on mar 7 2007 and has been assigned accession no pta 8259 strain pta 8259 upon grant of this patent will be released to the public without restrictions or conditions for the purpose of this invention the deposited mixed culture having identifying characteristics of pta 8259 or reflecting an ability for reducing chlorinated ethenes and chlorinated ethanes to ethene ethane and inorganic chloride under anaerobic conditions would be.