vvEPA
SITE FACTS
United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
Office of Solid Waste and
Emergency Response
Washington, DG 20460
ERA/540/F-93/510D
September 1993
Bioremediation Field
Initiative Site Profile:
Public Service Company
of Colorado
1 V
Location: Denver, Colorado- , •>"
j:: Laboratories/Agencies: U.S.
' --JEfiA Robert S. Kerr,
v Environmental Researcn <
fflaboratory (RSKERL), U.&. EPA" ,'
•» J^egion 8 > ' ]' ^>
Media and Contaminants: : •
_, BTEX in ground water ,
' 'Treatment? in situ
s.l'jbioiemediationofgroundjwater ]
I ?"^tjx nutrient arid hydrogen'; ,> j
^..iperoxide addition
^if Date of Initiative Selection:
'!' Spring 1991, '*',<•
^ ",- *? > > ! - ', , , , i -
^< Objective: To evaluate the ,/,--,
;^;e£fectivenessojfinsihi ">Mv !, "
\ ^bioreinediationpf used btt and, \
£ s,the potential for future
r^fenviranmental impact from ,- \,
^jesidual contaminants > , "• -.
\r:, , ... >-#, ' '•<• "."••
Bioremediation,Field Initiative
*>. ^Contact: John Wlson, U.S. EPA ",
i -RSKERL; P,O. tiox.J.198, Ada, ,.
Regional Contact: Suzanne
' > "Stevenson, U.^.' EPA Region 8,
2^99,918th Street Denver, CO '
" '
Background
In 1987, Public Service Company of Colorado (PSC), an electric utility,
determined that used oil had leaked from a 75-gallon tank at the
company's facility at 2701 West 7th Avenue in Denver, Colorado. The
tank served as a temporary catch basin for used automotive oil in the
facility's garage. A discrepancy between the volume of oil deposited
in the tank and the volume pumped out for disposal lead PSC to
suspect the leak. Though it is unclear when the leak first occurred, the
tank had been in service for 29 years before the leak was discovered.
The Bioremediatipn Field Initiative has conducted a retrospective
evaluation of the performance of in situ bioremediation of oil leaked
from the tank.
Characterization
PSC found soil concentrations of oil and grease beneath the tank
ranging up to 9,600 mg/kg. Soil samples also showed BTEX com-
pounds in the following concentrations: toluene, 3,200 ug/kg; ethyl
benzene, 820 M-g/kg; and xylenes, 29,600 Mg/kg. Ground water sam-
pling detected low levels of BTEX compounds, though levels of
xylenes exceeded EPA's proposed drinking water standards.
Field Evaluation
In July 1989, PSC installed an in situ bioremediation system to reme-
diate the contaminated ground water and promote biodegradatibn of
contaminants in the soil above and below the water table and in the
aquifer. The treatment took place in several stages. First, ground water
was pumped from a recovery well downgradient of the leaking tank
at the rate of 11 gallons per minute to ensure the capture and content
of contaminants. The recovered water then was treated by carbon
adsorption to remove dissolved hydrocarbons before being pumped
to a nutrient gallery. In. the nutrient gallery, the ground water was
amended twice: first with ammonium and phosphate compounds to
provide inorganic nutrients; then with hydrogen peroxide to increase
the water's level of dissolved oxygen. The amended ground water
T^X Printed on paper that contains at least
\±i£r 50 percent recycled fiber.
-------
was then reinjected upgradient of the leaking tank,
thereby delivering the nutrients and oxygen
needed to sustain aerobic biodegradation in the
saturated zone. Figure 1 is a computer-generated
model of ground water flow from the injection
wells to the recovery well. Figure 2 shows the actual
flow of nutrients beneath the leaking oil tank.
To speed remediation of the contaminated soil in
the vadose zone, PSC also added batches of nutri-
ents directly to the soil and installed a bioventing
system to induce a dynamic flow of ambient air
above the water table to highly contaminated areas
in the subsurface.
Status
By 1991, concentrations of BTEX in the monitoring
wells were approaching the cleanup goals. In
EWG
PSC Simulated Streamline*
-100
-100
100
Recovery Well
Nutrient
Recharge
.Gallery
Ground Water
Recharge
Gallery
-100
100
'WWG
Legend
A Recovery Well
• Nutrient Addition Point
- —Contour Intervalln Feet
Figure 1. Computer-generated model of ground water flow from
injection wells to recovery well.
Figure 2. Schematic of site showing flow of nutrients in ground
water under leaking tank.
March of 1992, PSC submitted an application for
closure to the State of Colorado. The site currently
is in the monitoring phase. In July of 1992, the U.S.
EPA Robert S. Kerr Environmental Research Labo-
ratory (RSKERL) conducted an evaluation of the
site, including soil coring to determine the quantity
and distribution of residual oil do wngradient of the
leaking tank, chemodynamic modeling to predict
the maximum concentration of BTEX that could
partition from residual oil to ground water, and
hydrogeologic monitoring to predict the concentra-
tion of BTEX in a hypothetical well at the site
boundary downgradient of the leaking tank. The
results of this evaluation still are being analyzed,
but RSKERL's interim conclusion is that, while
some hydrocarbons remain at the site, they are not
contributing at this time to substantial contamina-
tion of ground water in the aquifer.
The Bioremediation Field Initiative was established in 1990 to expand'the nation's field experience in bioremediationtechnologies.,
The Initiative's objectives are to more fully document the performance of full-scale applications of bioremediatipn; provide -
technical assistance to regional and state site managers; and provide information on treatability studies,' design, and operation. 9f
bioremediation projects. The Initiative currently is performing field evaluations of bioremediatiorji at eighf other hazardous waste* t
sites: Libby Ground Water Superfund site, Libby, MT; Park-City'Pipeline, Park City, KS;'Bendix Corporatipri/Allied Automotive'",
Superfund site, St. Joseph, MI; West KL Avenue Landfill Superfund* site, Kalamazoo, MI; Eielson Air Force Base Superfund site/ ,ss
Fairbanks, AK; Hill Air Force Base Superfund site. Salt Lake City, TJT; Escamhia Wood,Preserving Siter-Brookhaven, Brookhaven, \
MS; and Reilly Tar and Chemical Corporation Superfund site, St. Louis Park, MN[. To obtain'profiles on these additional sites or ~
to be added to the Initiative's mailing list, call 513-569-7562.IFor furttier information on the Bjoremediation 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,401MStreet,SW.,Washington,DC20460. ~" > '•;.„ -% «" ><• -\ */''''/* '",/ V >V' V ^r '•' '-"
------- |