United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
Office of Solid Waste and
Emergency Response
Washington, DC 20460
xvEPA
SITE FACTS
Location: Salt Lake City, Utah
Laboratories/Agencies: U.S.
, lAir Force, U.S. EPANational
T Risk ManagemenkResearcrT
* % Laboratory (NRMRL), U.S. EPA
iRegibnS ( „. fr. „ ,, „
Media and Contaminants: >
JB4 jet fuel in unsaturated soil
JV* r " t V
* Treatment: Bioventing -T
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1 J u >!-f
1 Date of Initiative Selection:
Spring 1991
1 Objective: To evaluate the
- effectiveness of bioventing jet- ..
( _ fuel in deep vadose zone soil
Bioremediation Field Initiative
Contact: Gregory Sayles,U.S.
EPA JNRMRL, 26 West Martin
Luther King Drive, Cincinnati,
OH 45268
Regional Contact: Robert
Stites, U.S. EPA Region 8,'
999 18th Street, Denver, CO
80202-2466
EPA/540/F-95/506C
September-1995
Bioremediation Field
Initiative Site Profile:
Hill Air Force Base
Superfund Site
Background
In 1988, the U.S. Air Force initiated a study at Hill Air Force Base (AFB) to examine
the potential of bioventing to remediate JP-4 jet fuel-contaminated soils. Bioventing
is the process of supplying oxygen in situ to oxygen-deprived soil microbes by
forcing air through contaminated soil at low airflow rates. Because bioventing
equipment is relatively noninvasive, this technology is especially valuable for treat-
ing contaminated soils at military bases, industrial complexes, and gas stations,
where structures and utilities cannot be disturbed.
Promising results from the Air Force's initial study prompted the U.S. EPA National
Risk Management Research Laboratory (NRMRL) and the Air Force to conduct a
field evaluation of bioventing at Hill AFB and at Eielson AFB (see separate fact sheet,
EPA/540/F-95/506B). The main objective of the Hill AFB evaluation was to deter-
mine the effect of air injection flow rate on the effectiveness of bioventing in
stimulating biodegradation while minimizing volatilization. The evaluation also
provided an opportunity to gain experience in bioventing large volumes of soil with
plumes of fuel that extend deep beneath the surface as well as under roads, under-
ground utilities, and buildings.
Characterization
Prior to bioventing, the Hill AFB site was contaminated with JP-4 jet fuel from a
depth of about 35 ft to the ground water 95 ft below the surface. The contaminated
soil was a mixture of sand, silty sand, and sand interspersed with gravel and clay.
Soil samples taken in September 1991 revealed an average total petroleum hydro-
carbon (TPH) level of 890 mg/kg, with TPH levels at some depths reaching 5,000
mg/kg. At most depths, benzene, toluene, ethylbenzene, and xylene (BTEX) levels
ranged between about 300 mg/kg and about 800 mg/kg. The area of contamination
extended beneath a tool maintenance building, engine storage yard, and fuel
storage yard (see Figure 1).
Field Evaluation
Unlike soil venting or soil vacuum extraction, bioventing uses low airflow rates
to stimulate biodegradation while minimizing volatilization of contaminants in
soil. Higher airflow rates stimulate faster and more widespread biodegradation
but also release more volatile emissions to the surface. To study the tradeoff
between the rate and range of biodegradation and the release of volatile emis-
sions, the Air Force and NRMRL operated a bioventing system at the Hill AFB
site from July 1991 to January 1995, changing the airflow rate about twice a year.
They conducted a total of five airflow rate evaluations: one each at 28, 67, 67,40,
and 117 ft /min. The 67-ft /min evaluation was repeated to include additional
monitoring points added to the site.
Each airflow rate evaluation included:
• An in situ respiration test—measurement of the rate of oxygen uptake by micro-
organisms in the soil to estimate the rate of biodegradation occurring there.
Recycled/Recyclable
Printed on paper that contains at
least 20 percent recycled fiber
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F-16 Engine
TMtC*Ht
Tool
Storage
Yard
SMP4
• SMP s Surface Monitoring Point
O CW = So!! Vapor Cluster Well
Cross-Section Trace
<~ Projection of Cluster Well Onto Cross-Section Trace
Figure 1. Plan visit) of Hill AFB site.
• Surface emissions tests—both dur-
ing air injection and while the,air
injection system was shut off so
that emissions rates could be com-
pared.
• Soil gas sampling—to monitor oxy-
gen, carbon dioxide, TPH, and BTEX
levels.
Status
The Air Force and NRMRL have col-
lected and analyzed bioventing per-
formance data for each of the four
airflow rates. The total rate of biodegra-
dation increased with increasing air-
flow rates, because the radius of
biological activity increased. Surface
emissions rates remained about the
same with increasing airflow rates.
Moreover, surface emissions rates
during air injection were not signifi-
cantly different from those during
bioventing shutdowns. This was an
important finding because it indicates
that bioventing at the airflow rates
evaluated (28 to 117 ft3/min) does not
increase emissions of volatilized con-
taminants.
Final soil sampling conducted in
December 1994 revealed that TPH
and BTEX levels had declined at all
but one soil depth within a 25-ft
radius of the injection well. Only
at a depth of 90 to 100 ft (at the
capillary fringe) did TPH and BTEX
levels fail to decline, suggesting
that the capillary fringe was not ade-
quately aerated. These results help
demonstrate the feasibility and effec-
tiveness of bioventing at the airflow
rates evaluated.
TJte Bioremediation Field Initiative was established in 1990 to expand the nation's field experience in bioremediation
technologies. The Initiative's objectives are to more fully document the performance of full-scale applications of
bioremediation; provide technical assistance to regional and state site managers; and provide information on treata-
bility studies, design, and operation of bioremediation projects. The Initiative currently-is performing field evaluations
of bioremediation at eight other hazardous waste sites: Libby Ground Water Superfund site, Libby, MT; Park'City
Pipeline, Park City, KS; Bendix Corporation/Allied Automotive Superfund site, St. Joseph, MI; West KL Avenue
Landfill Superfund site, Kalamazoo, MI; Eielson Air Force Base Superfund site, Fairbanks, AK; Esrambia *Wood
Preserving Site, Brookhaven, MS; Rettly Tar and Chemical Corporation Superfund site, St. Louis Park, MN;^n3*Pu6lic
Service Company, Denver, CO. To obtain profiles on these additional sites or to be added to the rnitiative^maiUng *"
list, caE513-569-7562. For further information on the Bioremediation Field Initiative, contact Fran Kremer, Coordinator, _
Bioremediation Field Initiative, U.S. EPA, Office of Research and Development, 26 West Martin Luther King Drive,
Cincinnati, OH 45268; or Michael Forlini/ U.S. EPA, Technology Innovation Office, Office of Solid Waste and Emergency
Response, 401M Street, SW, Washington, DC 20460. ' «- ' ' , V
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