4.4.6.6   Implementability -- Alternative 6

Implementation considerations for bioremediation systems include
technical feasibility, administrative feasibility, and
availability of services and materials.  Additional information
is also needed to implement bioremediation systems.  These
considerations are discussed below.

Technical Feasibility

Several technical difficulties may be encountered during
implementation of this alternative.  Under both Scenarios 1 and
2, the proposed location for the CTF does not provide adequate
area for the required number of CSPB cells and support equipment. 
Depending on the required size of the CSPB cells and the
permeability of the materials being treated, the air distribution
system may require extensive piping to provide adequate aeration
to all of the material in the cells.  If tilling or other
mechanical mixing equipment is used to aerate the soils, the
piping system would not be needed, but soil cannot be placed in
lifts deeper than the mixing equipment can reach.  During
anaerobic treatment, application of amendment solutions may
require either temporary removal of the synthetic liner, or, if
the cover is to remain in place, installation of the distribution
system at or below the surface of the contaminated materials in
the CSPB cells.

Administrative Feasibility

For this alternative, federal, state, and local approval would be
required.  Monitoring considerations include the need to develop
a sampling scheme to collect representative samples that
accurately characterize the PCB levels remaining in contaminated
materials during treatment.  During the anaerobic phase of
treatment, the levels of individual congeners should be analyzed
to determine the extent of dechlorination and when to begin
aerobic treatment.  During aerobic treatment, total PCB
concentrations should be analyzed to determine if the cleanup
standard has been achieved.  

This alternative poses a low risk of exposure to releases to the
environment from system failure.  The CSPB cells should be
provided with adequate controls, including an impermeable bottom
liner and leachate collection system, to prevent releases of
contaminated leachate.  During in situ biological treatment,
contaminants could potentially leach from lagoon sludges into
groundwater. 

Availability of Services and Materials

Most equipment necessary to implement this alternative is readily
available, particularly for CSPB.  At some PCB-contaminated
sites, in situ biological treatment field studies involved more
specialized equipment, including steel caisson reactors used as
testing cells at the Hudson River site (Harkness 1993), and
dredge-mounted pumps to shear lagoon sludges and pressurized
pipeline contractors to inject oxygen gas used at the French
Limited Superfund site (DEVO 1992).  Because of the amount of
research that has been conducted on bioremediation at the General
Electric Company Hudson River sites, the French Limited Superfund
Site, and other sites, specialists in PCB bioremediation are
available; however, few specialists have experience beyond the
laboratory scale.   

Some vendors of biological treatment technologies offer
proprietary mixtures of amendments, nutrients, and bacterial
strains.  However, the widespread occurrence of anaerobic
dechlorination suggests that either dechlorinating organisms are
ubiquitous or that the dechlorination process is part of a
biochemical pathway common to many different anaerobic organisms
(Abramowicz and others 1993).  Treatability studies should
therefore be conducted to determine how to stimulate growth in
indigenous microorganisms using common limiting nutrients and
known PCB-analog amendment stimulants before testing
nonindigenous strains or unknown proprietary mixtures.

Although vendors with demonstrated experience in biological
treatment of PCBs beyond the laboratory and pilot scale are not
available, some vendors have demonstrated experience in treating
other contaminants through biological treatment.  After optimal
conditions for biological treatment of wastes from the CD sites
are determined during laboratory- and pilot-scale studies,
experienced vendors are available to design full-scale systems.

Additional Information Needed to Implement Bioremediation

Additional information is needed before this alternative can be
implemented.  First, an updated characterization of the
contaminated materials at the Bennett Stone Quarry, Lemon Lane
Landfill, Neal's Dump, and Neal's Landfill sites and at the ISF
is needed to determine the degree of chlorination of the PCB
congeners present at these sites and the presence and
concentration of other RCRA Appendix IX contaminants.  

Analytical information indicates that the PCBs originally
disposed of at the sites primarily consisted of Aroclors 1016,
1242, and 1248 (ISDH 1994).  Westinghouse did not use Aroclor
1248.  However, degraded Aroclor 1242 can look like 1248.  These
Aroclors are partially comprised of more highly chlorinated PCBs,
including several tri-, tetra-, and pentachlorobiphenyl
congeners; however, most of the contaminated materials at the CD
sites have most likely been under anaerobic conditions for
several years, and anaerobic dechlorination of the PCBs in these
materials may have occurred intrinsically.  Between 1983 and
1987, clay caps have covered the contaminated materials at the
Bennett Stone Quarry, Neal's Dump, and Neal's Landfill sites, and
contaminated soils removed from the Anderson Road Landfill site
are stored in the ISF in large piles.  The cap-covered wastes and
piled wastes are likely to be mostly anaerobic environments. 
Although the Lemon Lane Landfill site has been covered by a
synthetic liner since 1987, several large conduits have been
discovered beneath the landfill that may be providing oxygen to
the landfill materials,  resulting in localized aerobic
conditions.  Because the PCB-contaminated materials have not been
characterized since 1984, an updated analysis identifying
individual PCB congeners is needed to determine the degree of
anaerobic dechlorination that has occurred intrinsically and the
amount of further biological treatment needed.

The tertiary lagoon sludge at the Winston-Thomas Sewage Treatment
Plant site has been characterized more recently.  However, the
results of two separate evaluations do not completely agree.  One
of the evaluations was performed in 1992 by the City of
Bloomington's contractor, Environmental Audits, Inc. (EAI). 
Based on analytical results of nine lagoon sludge samples and two
drying bed sludge samples, EAI made the following observations
and conclusions (EAI 1993): 

          The average concentration of total PCBs and the total
          mass of PCBs in lagoon sludge samples decreased
          significantly compared to 1982 data because of aerobic
          biological destruction of the PCBs in the lagoon water
          and upper layers of sludge.

          The congener patterns in lagoon sludge samples were
          primarily Aroclor 1016, along with Aroclor 1242 and
          trace levels of highly chlorinated congeners present in
          Aroclor 1268.  This situation most likely resulted from
          dechlorination of initial releases of high
          concentrations of Aroclor 1242 and low concentrations
          of Aroclor 1268.

          PCBs were virtually absent from drying bed sludges,
          which most likely resulted from complete PCB
          destruction during sequential exposure of the sludges
          to anaerobic conditions in the lagoons followed by
          aerobic conditions in the drying beds.

In 1994, another evaluation of lagoon sludge analytical data was
performed by Dr. John F. Brown Jr., of General Electric Company,
an expert in the comparison of detected PCB congener patterns
with normal PCB congener patterns.  Based on congener-specific
analyses of samples from the drying beds and lagoon, Dr. Brown
concluded that only one drying bed sample had undergone
appreciable biodegradation and that only select di- and
trichlorobiphenyl congeners had been biodegraded in this sample. 
Dr. Brown also concluded that the lagoon samples contained almost
pure Aroclor 1242, which was almost completely unaltered (Brown
1994).  Although Dr. Brown's conclusions are believed to be more
valid than the EAI results based on his expertise, both
evaluations are based on the analysis of a limited number of
samples; therefore, the amount of biodegradation that has
occurred in the Winston-Thomas Sewage Treatment Plant site
sludges requires a more thorough evaluation.

Other information needed to implement this alternative includes
the following:  the types and quantities of amendments needed,
the effectiveness of using indigenous bacterial strains, the use
of amendments to stimulate biodegradation, the effectiveness of
using inoculations with isolated strains, the rate of oxygen
delivery during aerobic treatment, and the kinetics of anaerobic
dechlorination and aerobic degradation.  Treatability studies
should be performed to test these conditions to determine the
conditions that optimize biological treatment.  The treatability
studies should be conducted using representative samples of
actual waste to be treated.  In this way, it can be determined
whether any contaminants in the wastes to be treated are toxic to
the bacteria.  The treatability studies should also evaluate
whether sequential anaerobic-aerobic treatment is required at the
sites or if enough intrinsic dechlorination has occurred so that
only aerobic treatment is needed.

Pilot-scale and laboratory-scale treatability studies should be
conducted to determine how well laboratory conditions and results
can be reproduced in the field.  For CSPB, a pilot-scale study
could involve constructing a single biotreatment cell and
conducting tests on a smaller volume of soil than would be
treated during full scale in multiple cells.  During the
preparation of this report, only one site could be identified at
which pilot-scale sequential anaerobic-aerobic treatment in a
biotreatment cell has been conducted, but these tests were
inconclusive as of early 1994 (EPA 1994g).

Pilot-scale testing could be conducted in situ at the tertiary
lagoon using self-contained steel caisson reactors with
mechanical mixers and injection systems, which were used during
field studies at the Hudson River site (Harkness and others
1993).  Another possible in situ pilot-scale design could involve
partitioning off a small area of the tertiary lagoon and using
mechanical mixers and pumps to mix, aerate, and inject amendments
into lagoon sludges, which was performed at the French Limited
Superfund site (DEVO 1992).