Our in situ experience with PAHs is primarily related to the lower molecular weight PAHs (i.e. 2-4 ring PAHs) like naphthalene, anthracene, acenaphthalene, phenantrene, and pyrene. Our projects have demonstrated that these compounds can be readily biodegraded in situ under the appropriate conditions (both aerobic and anaerobic). Our experience as well as current academic literature, indicate that degradation rates of the 5- and 6-ring PAHs is limited primarily by desorption/dissolution mechanisms. Therefore, sites with extremely weathered PAH constituents, or those w/residual NAPL, are often not appropriate to implement bioremediation as a stand-alone technology. These would require an aggressive chemical-oxidation procress as the initial in situ remedial action. Our Dual-Ox™ technology was specifically designed for these types of recalcitrant contaminants.