Microbial Remediation Progress Update

If you’ve been following the cleanup efforts at one of our active remediation sites, we have encouraging news to share. During our June groundwater sampling event, we observed a decrease in the number of monitoring wells containing free-phase gasoline, a promising sign that the remediation process is working.

Even more remarkable, we documented clear evidence of biochemical degradation underway. Microbes are actively breaking down petroleum hydrocarbons and releasing gases like carbon dioxide and methane in the process. In fact, the groundwater in our sampling buckets visibly fizzed, a physical indicator of microbial activity! The appearance of gasoline has also transformed—its typical golden hue has shifted to dark brown and even black, due to the formation of organic and mineral precipitates.

One of the challenges in microbial remediation is ensuring that microbes reach the areas where they’re needed most. When a leak occurs, whether from a storage tank or product line, gasoline typically migrates downward through soil under gravity, slows as it encounters the groundwaters’ capillary fringe, and then spreads laterally at the water table, floating and migrating with the groundwater flow.

Unlike a continuous stream, fuel often travels in “slugs” or pulses. These are triggered by the rise and fall of groundwater, pressure gradients, and the permeability of surrounding soils. This means we may see excellent cleanup results immediately near our monitoring wells that have been inoculated with microbes but what about the spaces in between? How do we ensure our microbes contact any fuel in inaccessible areas? 

For Leaking Underground Storage Tank (LUST) sites in Oklahoma, the consultant (i.e. Priority Environmental) recommends future courses of action to the regulatory agency, the Oklahoma Corporation Commission Petroleum Storage Tank Division (OCC PSTD). PSTD reviews these recommendations to ensure clean-up monies from the State’s Indemnity Fund are used responsibly and effectively.

Recommendations from our June gauging-sampling event are currently under review. Stay tuned, we’ll keep you posted as we continue our clean-up efforts!