Theme: 06. Petroleum and Heavy Hydrocarbon Site Strategies

Topic Area: 6b. In Situ Remediation of Petroleum Hydrocarbons

Formatted Title:

Utilizing Steam Enhanced Extraction to Remove More than 2.6 Million Pounds of Jet Fuel

Background/Objectives:

Steam enhanced extraction (SEE) has a long-standing history of application within the petroleum industry to enhance oil recovery. Consequently, it was a natural choice for in situ source remediation at the former Liquid Fuels Storage Facility (ST012) on the premises of the former Williams Air Force Base (AFB) in Mesa, Arizona. Historic releases of jet propellant grade four (JP-4) and aviation gasoline resulted in an estimated 1.0 to as many as 11.1 million gallons (3,800 to 42,000 m³) of light non-aqueous phase liquid (LNAPL) in the subsurface. Thermal remediation using SEE was selected to replace an ineffective pump and treat remedy at ST012.

Approach/Activities:

A significant shift in regional groundwater extraction practices led to more than an 80-foot (24.4 m) rise in groundwater levels since the 1970s at the site, forming a large submerged light non-aqueous phase liquid (LNAPL) smear zone to depths of 240 feet (73.2 m) below ground surface (bgs) that was amenable to treatment with SEE. The SEE remedy was implemented over approximately 199,000 ft² (18,500 m²) and to depths ranging between 145 ft (44.2 m) and 240 ft (73.2 m) bgs, resulting in a total SEE treatment volume of 410,000 cubic yards (314,000 m³). Steam was injected into the subsurface from more than 30 locations at three separate depth intervals at rates above 40,000 pounds/hour (18,160 kg/hour). Hydraulic containment was provided by water extraction from more than 50 multi-phase extraction wells and treated in a system designed to handle up to 550 gallons per minute (125 m³/hour) of water and LNAPL. Recovered LNAPL was separated and conditioned by an onsite LNAPL conditioning system to allow the sustainable reuse of the recovered product as an auxiliary fuel source for the thermal accelerators used for vapor treatment.

Results/Lessons Learned:

The project team encountered various challenges throughout the design, execution, and operation of the SEE remediation, including the selection of a liquid pumping system capable of extracting wellfield fluids under demanding conditions at a depth of 240 ft (73.2 m) bgs. Additionally, the team had to choose suitable treatment system components equipped to manage contaminant mass loadings surpassing 30,000 pounds per day (13,620 kg/day). Issues related to LNAPL emulsions and biological factors in the liquid stream also needed to be addressed. Redundant treatment system components, both for liquids and vapors, were required to ensure a consistently high system uptime. Lastly, substantial efforts were put into conditioning and onsite storage of recovered LNAPL, and subsequent use of the conditioned LNAPL as fuel for the thermal accelerators. The steam system operated for a total of 578 days, during which 95 million gallons (360,000 m³) of water were extracted from the source area. A total of 302 million pounds (137 million kg) of steam were injected and at shutdown, more than 2.6 million pounds (1,180,400 kg) of JP-4 LNAPL had been removed from the subsurface.

This presentation will focus on the solutions implemented to overcome the challenges encountered during design and operation of SEE at ST012.

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Stuart Pearson