Wind-Powered Bioventing System for Remote Cleanup

Joey Hickey and Sean Ragain
GeoEngineers, Portland, OR

The FWS and GeoEngineers conducted a site investigation in the vicinity of the drain lines associated with former DoD generators at the Farallon National Wildlife Refuge in an area of suspected petroleum contamination. Soil samples indicated the presence of diesel-range petroleum hydrocarbons and lube oil-range hydrocarbons at concentrations of up to 35,000 milligrams per kilogram (mg/kg).

The remoteness of the site presented difficulties in implementing more common-place remediation approaches such as excavation. In response, two soil samples were collected to assess the biodegradation capabilities of the native microorganisms. The samples were analyzed for heterotrophic plate count, designed to identify and quantify existing petroleum degrading organisms. In addition, a bio-respiration and micronutrient analysis was completed on the soils. The results indicated that the soils were well suited for the aerobic degradation of petroleum hydrocarbons.

In consideration for the lack of electrical power at the site, a wind-driven passive bio-venting system was installed in the area of the contamination. A series of shallow, interconnected, slotted PVC pipes were installed in the area of impact. The bio-venting system is open to the atmosphere through vertical vent pipes. Vertical risers were fitted with rotary vent caps with wind-driven blades to induce a vacuum and promote air flow in the piping system and surrounding soils. The vents were fitted with a soft mesh net to protect from wildlife injury.

The poster for this project will provide an overview of the site history, an explanation of the chosen innovative remedial alternative, design criteria and its potential for application at other remote or inaccessible locations, a gallery of site photographs and a summary of the results of the project study.