Document 6BEb8pkEvZX4VJ8kDQVX105Ed

AR226-2550 D uP ont W ashington W orks RCRA Facility Investigation Results Review Oct. 28,1999 IIDX56232 1 Proposed Agenda Introductions Site Background Site Hydrogeology RFI Scope of Work RFI Results Conclusions and Recommendations Wrap-Up EID156233 Desired 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 ...._______ ______ IID 156234 Main Messages for Today: The DuPont Washington Works site is well characterized 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 o f human health and the environment from site SWMUs. D uPont intends to continue to actively operate the site hydraulic control program and monitor its effectiveness going forward. E ID 156235 4 Washington Works Background 1,200 acres on Ohio River in western WV Manufacturing began in 1948 Engineering Polymers, Fluoroproducts, and P&IP - Engineering plastics (Delrin) - Nylon pellets and filaments (Zytel) - Acrylic resins and molding compounds - Polyvinyl butyral (Butacite) - Teflon & Tefzel Approx. 2,400 employees (DuPont's 2nd largest) E ID 156236 E ID 156237 6 Regulatory History 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 RFI work plan for four remaining SWMUs 1998 and 1999 - Conducted RFI E ID X 56238 7 Riverbank Landfill Anaerobic Digestion Ponds Burning Grounds Polyacetal Waste Incinerator IID 156230 SWMU LOCATIONS E ID 156240 9 Rivetbank 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 E ID 156241 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. E ID 156242 Polyacetal Waste Incinerator 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 backfilling with clean soil and gravel E ID 156243 Burning Ground Operated from 1948 to 1965 Used for the open burning o f miscellaneous wastes (c.g, plant trash, off-spcc 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 E ID 156244 W ashington 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 aquifer E ID 156245 14 BL BttT l IJH crtM SL ji E ID 156246 15 Site Hydrogeology Site aquifer in sand and gravel unit D epth to groundwater is approximately 60 feet Groundwater flow direction is controlled by on-site production well system - East Well Field (seven wells-2000 gpm) Rarmey Well (800-1000 gpm) - T,ubcck Well Field (five wclls-700 gpm) Pumping induces river recharge to aquifer, results in high well yields E ID 156247 ) IX D 156248 17 r 18 E ID 156249 RFI Technical Approach Screened VI data against Region III residential RBCs to define applicable analyte list * Constructed groundwater flow model to provide an initial characterization of the site hydrogeologic system, and to identify additional data needs * Refined site conceptual model to develop a comprehensive list o f data needs Implemented a thorough investigation and monitoring o f site SWMU soils and site groundwater conditions j E ID 156250 19 EFI 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 E ID 156251 20 /T'SH Field Program 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 o f 70 ft * Compiled all results in a manner that enabled interpretation in the context of the site conceptual model E ID 156252 21 y . 22 E ID 156253 RFI Results E ID 1562S 4 .... RFI Findings Analyte PWI Carbon Tet MeCl PCE TCE Freon 113 FC-143 Arsenic Barium Cadmium Lead Nickel Chromium * BG * * * * * * RBL/ADP * * * * * * * * Potable Well ND ND ND ND ND * * # ND ND ND Process Wells ND * ** * ** * * * ND ND * E ID 156255 Site Land Use Chamcterization Land Use: - Onsite land use is industrial (current and future) - O ffsite land use is mixed industrial, commercial, open space, residential * Groundwater Use: - Onsite process and potable water - O ff-site Well Survey: * Public water supply 2 miles downriver * G E Plastics' wells west o f Washington Works - Site under hydraulic control; groundwater does not migrate off-site E ID 156256 Exposure Pathway Evaluation Receptors Site Worker Trespasser Constr Wkr Controlled by Pumping Site Worker E ID 156257 26 Ecological Evaluation Study area included terrestrial and riverbank habitat along the RBL/ADP N o significant ecological resources were present -- N o critical or sensitive habitats -- N o habitat reflective o f public concerns (e.g., game habitat) -- N o listed threatened or endangered species The absence of significant ecological resources leads to a lack o f ecological exposures, and hence no significant ecological risks EIDi56258 PreMmiiiary Risk Evaliiaton - So Observed Arsenic values were comparable to site background levels. ______ # E ID 156259 28 Preliminary Risk Evaluation -ProductionWells PSL is the preliminary screening level for FC-143; AL is the action level for iead. The groundwater screening value was exceed in process wells only. E X D 156260 T Risk Results Sutnmafy Soil concentrations o f 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, FC-143) somewhat exceed drinking-water based screening levels, but this water is not used for drinking N o unacceptable human health risks occur as a result of site SWMUs No significant ecological receptors or pathways occur at any SWMU E ID 156261 30 Recommendations for Future Action * 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 o f on-site potable well to ensure protection of human health * Continue operation of MeCl seep collection and treatment system E ID 156262 31 Overall Summary * With the completion o f the RFT, the DuPont Washington Works site SWMUs are well characterized and well understood. * Existing containment and treatment programs provide protection of human health and the environment from site SWMUs. * D uPont intends to continue to actively manage the site in a way that ensures the protection of human health and the environment into the future. E ID 156263 i E D 156264 33