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.
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.
Gap Test Cell at TB8
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 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
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.
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
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.
ecological team collecting reference data