4.4.6.5   Short-Term Effectiveness -- Alternative 6

The potential short-term effectiveness of bioremediation
technology application involves worker safety considerations,
potential community exposure, and time to complete treatment. 
The technology's impact in each area is discussed below.

Worker Safety

Other than the potential exposure to fugitive dust emissions
during excavation common to all alternatives involving
excavation, the risk to worker safety that would result from
implementation of this alternative is potential fugitive vapor
and dust emissions from the CSPB cells.  If the CSPB unit at the
CTF is not enclosed, fugitive dust emissions could potentially be
released when the impermeable cover is removed during the aerobic
phase of treatment.  The potential for these fugitive dust
emissions would be lessened by the application of amendment
solutions to the surface of the contaminated materials.  Workers
should be monitored for heat and cold stress.

Potential Community Exposure

The risks to the community that would result from implementation
of this alternative are potential fugitive dust emissions from
the CSPB cells and leachate migration to groundwater from the
tertiary lagoon.  Adequate controls on the CSPB unit, including
an impermeable bottom liner, leachate collection system, and a
runoff collection system, would minimize the potential for
community exposure from contaminated groundwater and surface
water, respectively.

Groundwater monitoring data from 1988 indicate that PCBs have
already leached into groundwater at low concentrations from the
tertiary lagoon.  Four rounds of groundwater sampling were
performed on 11 monitoring wells located around the perimeter of
the lagoon (eight wells hydraulically downgradient and three
wells upgradient).  During different rounds of sampling, PCBs
were detected in four of the downgradient wells at concentrations
ranging from 0.3 to 7 ppb (ISDH 1994).  Although in situ
biological treatment would not immediately remove the source of
contamination, the potential for leachate migration would not be
increased by implementing this alternative and would be reduced
as the contaminants are biodegraded after implementation of this
alternative.  However, if the entire clay layer underlying the
lagoon must be treated as specified in the CD, then the potential
for further migration to groundwater would increase
significantly.  The 21-inch thick clay layer underlying the
lagoon provides a partial protective barrier to leachate
migration, as evidenced by core sampling of lagoon sludge and
underlying clay conducted in 1983.  PCB contamination was
detected in the sludge of all eight core samples at
concentrations ranging from 220 to 4,400 ppm, but PCBs were
detected in the clay of only three of the eight core samples at
concentrations of 3, 9, and 15 ppm (ISDH 1994).  Treatment of the
entire clay layer would involve shearing the clay to increase the
bioavailability of the PCBs and mixing the sheared clay with the
sludge.  This procedure would eliminate the protectiveness to
leachate migration provided by the clay layer.  However, if only
the areas exceeding the applied cleanup standard require
treatment, these areas alone can be scraped up and treated, and
the integrity and protectiveness of the clay layer would be
maintained.  If the proposed TSCA Cleanup Spill Policy industrial
standard of between 10 and 25 ppm PCBs is applied, only small
areas of the clay layer may require treatment.  Regardless of the
applied standard, an updated characterization of the PCB
contamination in the clay layer is needed before implementing
this alternative.