Pilot scale injections of nanoiron stabilized with carboxymethyl cellulose (CMC) were performed at an active field site contaminated with a range of chlorinated volatile organic compounds (cVOC). The cVOC concentrations and microbial populations were monitored at the site before and after nZVI injection. The remedial injection successfully reduced parent compound concentrations on site. A period of abiotic degradation was followed by a period of enhanced biotic degradation. Results suggest that the nanoiron/CMC injection created conditions that stimulated the native populations of organohalide-respiring microorganisms. The abundance of Dehalococcoides spp. immediately following the nanoiron/CMC injection increased by an order of magnitude throughout the nanoiron/CMC affected area relative to pre-injection abundance. Distinctly higher cVOC degradation occurred as a result of the nanoiron/CMC injection over a three week evaluation period when compared to control wells. This suggests that both abiotic and biotic degradation occurred following injection.