Conceptual Work Plan
for Winston-Thomas
May 15, 1997
Dan Hopkins - U.S. EPA
Mayor John Fernandez - Bloomington, In.
Utility Service Board - City of Bloomington
Monroe County Commissioners
Resa Ramsey - IDEM
Re: Conceptual Work Plan for Remediation of Drying Beds and Digesters
at the Winston Thomas Wastewater Treatment Facility in Bloomington, Indiana.
Prepared for Westinghouse Bloomington Project by Blasland, Bouck & Lee,
Inc. April 1997.
Our comments on the April 1997 Conceptual Work Plan for Remediation of
the Drying Beds and Digesters at the Winston Thomas Treatment Plant (WTTP)
are presented below. Remediation of the digesters, drying beds and piping
is relatively straightforward and should proceed as soon as possible, but
only with some modifications to the plan as suggested below.
1. Concrete Surfaces
1a. PCB Action Level/Cleanup Goal for concrete surfaces is too high.
"Effective polychlorinated biphenyl decontamination of buildings
and equipment is a difficult challenge. Required cleanup levels are typically
very low, with the PCB spill policy cleanup criteria of 10 micrograms per
100 square centimeters (40 CFR 761 Subpart G) applied most often."
(Bonem and Borah 1995).
Westinghouse is proposing to clean concrete surfaces in the digesters
to 100 micrograms PCB per 100 sq. cm., much less protective than the PCB
spill policy criteria. This elevated cleanup goal may have been chosen based
on restricted human exposure to the interior surfaces of the digesters.
However, the digesters will be partially dismantled and may remain exposed
to the environment. Any surface with more than 10 micrograms PCB per 100
sq. cm should be sealed or isolated.
1b. Method for removing PCBs beyond the surface must be specified
"Over the years, PCBs and other contaminants will migrate deeper
into the substrate (concrete) through the pores in any material. Migration
occurs naturally due to gravity and specific gravity differentials, with
water from routine cleaning or with pressure. The depth to which this migration
will occur depends on many factors, including the porosity of the material,
the mobility and solubility of the contaminants, the presence of coatings
and the existence of other drivers. Migration of 0.5 inches or more is common,
and can exceed 4 inches in some cases. Since many current decontamination
projects are addressing incidents that occurred 20 or more years ago, deep
penetration of PCBs is a widespread concern." (Bonem and Borah, 1995).
The Conceptual Work Plan proposed to use "spray washing" to
remediate concrete surfaces, but not all spray washing processes are adequate.
Spray washing with plain water is not effective for PCB removal. Physical
(abrasive) cleaning methods are effective only at the surface. If PCBs have
penetrated beyond the surface, which is likely to be the case at the WTTP,
the PCBs leach back to the surface over time.
It is important to specify a chemical process that extracts PCBs as far
into the concrete as possible. Chemical processes such as the EET, Inc.
TechXTract process achieve better results and should be specified in the
work plan. Product literature from EET is attached. If core sampling shows
that PCBs have penetrated several inches or more into the concrete, surface
treatment may not be adequate unless the surfaces are sealed following cleaning.
1c. Address concrete berms and walls in Drying Beds
The four drying beds are surrounded by concrete berms 18 inches high,
and additional concrete walls divide the beds into separate sections. The
Conceptual Work Plan proposes to leave these structures in place, exposed
to the environment, but no sampling or remediation is proposed. Wipe samples
should be obtained from each drying bed. Concrete walls with more than 10
micrograms PCB per sq. cm. should either be removed for disposal, or cleaned
with a chemical process such as EET's TechXTract. If a less protective PCB
action level is adopted, any surface with more than 10 ug/100 sq. cm should
be sealed.
2. Sludge Drying Beds
2a. Sand and Gravel Layers in the Drying Beds should be removed, washed,
then replaced
As a general rule, PCBs adhere to clay and organic matter, not to sand
and gravel. The fact that PCBs were detected within the sand and gravel
layers under the dried sludge indicates that some sludge, clay, or other
organic matter contaminated with PCBs is trapped there.
The Conceptual Work Plan proposes to remove some of the sand if it contains
more than 50 ppm PCBs. Sand and gravel with less than 50 ppm PCBs would
be left in place, then covered with 18 inches of soil and grass. This is
not an acceptable approach. A gravel sample with 50 ppm PCBs is probably
composed of mostly clean rock with some highly concentrated pieces of sludge
or clay. PCBs in the sand and gravel would still be exposed to groundwater
and available for transport.
The buried sand and gravel layers would have much higher effective porosity
than the clay and soil surrounding them, and would act as sumps for subsurface
flow. During rainfalls or floods, groundwater would flush the sand and gravel
layers. Since the PCBs are not adsorbed to the sand and gravel, but merely
trapped there, PCBs will gradually be discharged as the water drains, in
dissolved form and attached to suspended sediment or organic matter.
It is important to prevent water from coming in contact with any residual
PCBs left in the ground, regardless of the concentration, and it would be
difficult, or impossible to do this at the drying beds. Capping the sand
and gravel left in the drying beds would prevent rainwater or surface runoff
from flowing directly down into the sand and gravel, but a surface cap would
not prevent groundwater from entering the sand and gravel layers from the
sides or beneath.
It would be reasonable and relatively inexpensive to excavate the sand
and gravel, wash it using any of the commercial soil washing/physical separation
processes, and replace the clean sand and gravel back in the excavation.
The wash water and PCB-contaminated sediment or sludge would be treated
and disposed of along with the other contaminated materials.
If the work plan is modified to remove the sand and gravel for cleaning
or disposal, there will be no need to perform the costly post-excavation
sampling currently proposed for the sand and gravel.
Finally, post-excavation PCB sampling should be performed on the clay
beneath the sand and gravel, and any clay that exceeds the PCB action level
for soil should be excavated and disposed of off-site.
2b. A PCB Action Level of 50 ppm in soil is not protective of human health
or the environment
The proposed PCB action level of 50 ppm appears arbitrary, and is not
adequately protective of human health or the ecosystem. This site must be
remediated to the point at which it no longer present a danger to human
health and the ecosystem. A cleanup goal of 50 ppm represents a substantial
improvement over the current condition, but does not constitute complete
remediation. Once a PCB cleanup goal is agreed upon by the Consent Decree
parties, Westinghouse must agree to revisit the areas of the sludge drying
beds and digesters to ensure that it satisfies the overall cleanup criteria
at this site.
3. Drainlines
The Conceptual Work Plan for drainline remediation should not be accepted
in its present form. It is essential that sediment samples from the drainlines
or wipe samples from the interior of each drainline be analyzed for PCBs
prior to selecting a remedial approach. It is also essential that the integrity
of all drainlines be assessed by video camera.
Assuming that sediment or wipe sampling confirms that PCB contamination
exists in all the drainlines, the remedial approaches outlined in the Conceptual
Work Plan are not adequate.
High pressure washing should not be used under any circumstances because
it may induce cracks in fragile sections or joints, forcing PCB contaminated
wash water and sediment into soil and bedrock.
Grouting is not a suitable permanent remedy for the drainlines at WTTP
for several reasons. The first drawback of grouting is similar to problems
with solidification of PCB waste: the grout immobilizes the material to
which the PCBs are attached, but it does not prevent the PCBs from leaching
out of the solid matrix in the presence of oils or solvents. Therefore,
PCBs may leach from the solidified matrix if exposed to a suitable carrier
. The second drawback is that it is impossible to confirm that the entire
drainline is filled with grout. Even small gaps between the grout and the
drainline could permit PCBs to be released to groundwater. Another practical
consideration is that future use of the site would be restricted.
The best long-term solution is to excavate drainlines with PCBs above
the PCB action levels for sediment or surfaces. This is a permanent remedy
and there would be no requirements regarding long-term monitoring or restrictions
on site use.
In conclusion, several important changes are required before this Conceptual
Work should be adopted. However, I am very supportive of the Consent Decree
parties' willingness to move forward with remediation of part of the Winston
Thomas facility. I hope this initiative results in prompt action at the
site and many other sites that pose immediate risks to the community and
the ecosystem: contaminated soil on the west side of Clear Creek, contaminated
water, sludge and sediment in the 17-acre lagoon at WTTP, and the Illinois
Central / Quarry Spring.
Sincerely,
Mike Baker
COPA
Prepared by: Melissa Valentin, P.E., MVA Consulting, Inc.
encl: Surface washing literature and TechXTract product descriptions
from EET, Inc. |
