Document LdxXxxokm7ybONyawd8Vdg75
AR226-2550
DuPont Washington Works
RCRA Facility Investigation Results Review
Oct.28,1999
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IID156232
Proposed Agenda
Introductions Site Background Site Hydrogeology
RFI Scope of Work RFI Results
Conclusions and Recommendations
Wrap-Up
EID156233
Desited Meeting Outcomes
To familiarize the EPA project team with the Washington Works site physical setting
To share the results obtained from the recently completed RCRA Facility Investigation
To provide perspective on the RFI results To propose a path forward that will ensure continued
protection of human health and the environment
SID156234
Main Messages for Today:
The DuPont Washington Works site is well characterised and well understood, as a result of over 10 years of investigation and monitoring,
The combination of TRMs and the active site hydraulic control program ensure protection of human health and the environment from site SWMUs.
DuPont intends to continue to actively operate the site hydraulic control program and monitor its effectiveness going forward.
EID156235
WasMn^ Works Background
1,200 acres on Ohio River in western WV
' Manufacturing began in 1948
Engineering Polymers, Pluoroproducts, and P&IP - Engineering plasdcs (Delrin) - Nylon pellets and filaments (Zytel) - Acrylic resins and molding compounds - Polyvinyl butyral (Butactte) - Teflon &Tefzel
Approx. 2,400 employees (DuPont's 2nd largest)
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Regulatory Histofy
1989 - HSWA permit issued by EPA Region III
designating 12 SWMUs 1991 and 1992 - Conducted Verification
Investigation (VI) on six SWMUs
" March 1997 - EPA commented on VI and required
RJPI work plan for four remaining SWMUs 1998 and 1999 - Conducted RFI
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RFISWMXJs
Riverbank Landfill Anaerobic Digestion Ponds Burning Grounds Polyacetal Waste Incinerator
EID156238
SWMU LOCATIONS
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Rivefbank Landfill
Operated from 1948 to mid-1960s Measured 4,500 feet long by 150 feet wide Filled steep slope separating main plant terrace from
river floodplain
Filled with general plant solid waste Closed by covering with soil, vegetation, and rip-rap Today the RBL is densely vegetated Methylene chloride seep was the main area of
concern - now controlled by collection and
treatment system
EID156241
Anaerobic Digestion Ponds
Operated from the mid-1950s to 1988 (three ponds) Used for wastewater treatment
Constructed with bentonite clay liners (i.e., ponds #2 & #3) and polyethylene sheet walls
Closed by removing liquid, sludge, clay, and some underlying soils (5,400 cubic yards) and covering with
soil and vegetation.
EID156242
Polyacetal Waste Incineratoi:
Operated from 1959 to 1990 Consisted to two, ten-foot deep concrete and fire
brick-lined pits Used for the burning of off-spec polyacetal polymer
Area -was closed by excavating and backfillingwith
clean soil and gcavel
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Burning Ground
Operated from 1948 to 1965
Used for the open burning of miscellaneous wastes (e.g. plant trash, off-spec plastic, and organic liquids)
Soils were excavated in 1974,1989, and 1990 (approximately 250 cubic yards)
In 1990, the BG was leveled with clean fill to allow for plant expansion, and a perimeter drainage ditch
was installed.
Mostly covered with buildings, concrete, and asphalt
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EID156244
Washington Works - Geology
Simple stratigraphy - Ohio River Terrace Deposits Fine grained soils near surface and along riverbank Thick sand and gravel unit:
- Primary geologic unit - Overlies Permian age shale/sandstone bedrock - Contains site aquifef
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Site Hydrogeology
Site aquifer in sand and gravel unit Depth co groundwater is approximately 60 feet Ground-water flow direction is controlled by on-site production well system - East WeU Field (seven weUs-2000 gpm)
- RanneyWell (800-1000 gpm) - Lubcck Well Field (five wclls-700 gpm) Pumping induces river recharge to aquifer, results in high well yields
EID156247
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EID156248
EID156249
RFI Technical Approach
Screened VI data against Region III residential RBCs
to define applicable analyte list Constructed ground-water flow model to provide an
initial characterization of the site hydrogeologic syatem and to identify additional data needs Refined site conceptual model to develop a comprehensive list of data needs Implemented a thorough investigation and monitoring of site SWMU soils and site groundwater conditions
EID156250
: RFI Report Contents
Describes the comprehensive field program Presents and discusses all site data Presents groundwater flow modeling results Presents screening-level human health risk evaluation
by comparing maximum constituent concentrations in
exposure media to RBCs for industrial soils and drinking water
Presents screening-level ecological risk evaluation by characterizing site habitat within the RFI study area
Provides conclusions and recommendations for further action
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EID156251
T REI Field Pfogram Overview
Installed 24 new monitoring wells Sampled 40 monitoring wells and 5 production wells
(two rounds) Drilled 35 soil borings, and collected 15 hand auger
samples Collected approximately 150 soil samples to a
maximum depth of 70 ft Compiled all results in a manner that enabled
interpretation in the context of the site conceptual
model
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RFI Results
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DUFII?indmgs
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Analyte
PWI BG
RBL/ADP Potable Process
WelL . Wells
Carbon Tet
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ND
NO
MeCl
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ND
PCE
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ND
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TCE
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ND
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Freon 113
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ND
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FC-143
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**
Arsenic Barium
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Cadmium
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ND
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Lead
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ND
ND
Nickel
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ND
ND
Chromium *
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EID156255
Site Land Use Characterization
" Land Use:
- Onsice land use is industrial (current and future) - Offsite land use is mixed industrial, commercial, open
space, residential
Groundwater Use:
- Onsite process and potable water - Off-site Well Survey:
Public water supply 2 miles downriver
GE Plastics' wells west of Washington Works - Site under hydraulic control; groundwater does not
migrate off-site
EID156256
Exposure Pathway Evaluation
Receptors
tngcstion Dennal
Inhalation
Sue Worker Trespasser Constr Wkr
Offsite Migration: Controlled by Pumping
Site Woricer
EID156257
Ecological Evaluation
Study area included terrestrial and riverbank habitat
along the RBL/ADP No significant ecological resources were present
-- No critical or sensitive habitats -- No habitat reflective of public concerns (e.g., game
habitat)
-- No listed threatened or endangered species The absence of significant ecological resources leads
to a lack of ecological exposures, and hence no
significant ecological risks
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Preliminary Risk Evaluation- Soil
'"Observed Arsenic values were comparable to site backgrouiri levels.
EID156259
Fteliminary Risk Evaluation "Pfoductioti "Wells
PSL is the preuminaly screening level for FC-143; AL is the action level for lead. The groundwater screening value was exceed in process wells only.
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Risk Results Stmamary
Soil concentrations of all constituents are well below
their respective RBCs for industrial soils
Potable well water concentrations are below screening
levels for drinking water
Process well water concentrations of two constituents (TCE, PC-143) somewhat exceed drinking-water based screening levels, but this water is not used for drinking
No unacceptable human health risks occur as a result of site SWMUs
No significant ecological receptors or pathways occur at any SWMU
EID156261
Recommendations for Future Acdon
Continue production well pumping to maintain site hydraulic containment
Conduct long-term groundwater level monitoring to ensure continued capture of site groundwater
Conduct long-term groundwater quality monitoring ofon-sitc potable well to ensure protection of human health
Continue operation ofMeCl seep collection and
treatment system
EID156262
Overall Summary
With the completion of the KFT, the DuPont
Washington Works site SWMUs are well characterised and well understood. Existing containment and treatment programs provide protection of human health and the environment from site SWMUs. DuPont intends to continue to actively manage the site in a way that ensures the protection of human health and the environment into the future.
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