As part of the requirements set forth by the 1998 Cleanup or Abatement Order (CAO) issued by the Regional Water Quality Control Board (RWQCB), Unocal conducted pilot studies of innovative remedial technologies that may provide an alternative to excavating petroleum hydrocarbon-affected soils at the Guadalupe Restoration Project. These technologies were recommended by the Pilot Test Panel (PRP), comprised of three scientific experts with experience in the remediation of subsurface petroleum hydrocarbon-affected soils.

The purpose of conducting pilot studies is to evaluate the applicability and feasibilty of potential remedial technologies under actual field conditions. Pilot studies are intended to provide information for final design.


Land Treatment:
Bioremediation, or land farming, of hydrocarbon affected soils focuses on understanding and enhancing the breakdown of hydrocarbons by bacteria. The bacteria use the hydrocarbons as a food source, which are digested to produce carbon dioxide and water.

Land Treatment Unit:
Bench-scale and field studies were conducted to evaluate the use of a Land Treatment Unit (LTU) for the on-site treatment of hydrocarbon-affected material excavated at the Guadalupe Restoration Project. To enhance the bioremediation of hydrocarbons in affected soil, factors such as aeration, soil moisture content, nutrient availability and carbon substrate addition are adjusted as necessary to accelerate the microbial degradation of the hydrocarbons contained in the affected material.

Data Gap Test Cell at TB8

In-situ Bioremediation:
Bioremedation is the process by which living organisms act to degrade or transform organic contaminants. Most organic compounds found in crude and refined petroleum hydrocarbon mixtures are known to degrade under aerobic and anaerobic conditions.

Biosparging uses air blowers to introduce air (in a continuous or pulsed fashion) into vertical or horizontal wells below the water table. Introducing oxygen below the water table promotes the growth of aerobic microorganisms that can degrade dissolved-phase diluent. Biosparging can be effective as an in-situ remediation technology that has a minimal adverse impact on the environment.

Natural Attenuation:
Natural attenuation is a process in which bacteria digest the hydrocarbons in groundwater and soil at a rate that exceeds the rate at which the hydrocarbons are moving in either soil or groundwater. Although hydrocarbon movement at Guadalupe is believed to be negligible, the mechanisms of natural attenuation need to be studied thoroughly so that plumes in the interior of the Field can be better understood.

Copies of the Natural Attenuation brochure are available by contacting the Guadalupe Field Office

Hot Water Flooding and Steam Injection Pilot Test:

The PTP recommended constructing a field pilot test of hot water flooding and extraction followed by steam injection and extraction. Thermal mechanisms involved in this technology could provide a method for removing subsurface petroleum hydrocarbons within a reasonable time frame. The goal is to find a technology that removes hydrocarbon impacted soils with minimal impact to the site ecosystems.

The hot water and steam flood field pilot test was conducted under the oversight of the PTP and the RWQCB and supervised by Unocal. Initial field construction began the fall of 2002. The test cell was a 70-foot by 70-foot area bound by four injection wells that penetrated the groundwater table 70 feet below the ground surface, with an extraction well in the center. The test cell was sited within the larger Pilot Test area that was bound by eight outer extraction wells in an area 140 feet by 140 feet (approximately 0.5 acres). The outer extraction wells served to maintain the integrity of the pilot test cell. Steam was injected into the wells at a rate of 20,000 lb/hr. The extracted vapors and liquid were processed to remove the hydrocarbons, which were then sent to an off-site recycler. Upon completion of the pilot test, data and results were submitted to the PTP for review and recommendations.

Ultimately the RWQCB will incorporate the recommendations of the PTP in their decision-making processes in determining the next phases of remediation at the site. Other studies that the RWQCB will incorporate are the Site-Wide Screening-Level Ecological Risk Assessment, completed and ratified in 2005, and current research that addresses the sustainability of Natural Attenuation.

Hot water/steam pilot test site

As part of the pilot study a Pilot Ecological Team (PET) was formed to evaluate the ecological impacts of the pilot test. The study area included the areas of the pilot study and two nearby reference areas. Ecological data collected included physical (temperature and moisture), botanical (type, quantity and condition of plants), wildlife (type and quantity of small mammals) and arthropods (type and quantity). Data collected prior, during and after the pilot study operation was evaluated to determine what impact the hot water flooding and steam injection pilot test had on the ecological habitat, and is discussed in the Project Impact Analysis Report. Copies of the brochure containing an overview of the pilot test are available by contacting the Guadalupe Field Office.

Pilot ecological team collecting reference data