Document 5Dq80EN2JXZgb7DmG3Go3y7rN

AR226-2551 6ZZI IOHSV RGRA Facility Investigation Results Review March 14,2001 Introductions Site Background Site Hydrogeology RFI Scope of Work RFI Results Conclusions and Recommendations Wrap-Up 08HIOHSV  To familiarize the EPA/WVDEP project team Washington Works site physicalsetting 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 con protection of human health and the environme isniOHSV  The DuPont Washington Works site is well characterized and we! understood, as a result o over 10 years of investigation and monitoring. The combination of IRMs and the active site hy control program ensure protection of human he and the environment from site SWMUs. DuPont intends to continue to actively operate site hydraulic control program and monitor its effectiveness going forward. Z8ZIIOHSV  1,200 acres on Ohio River in western WV Manufacturing began in 1948 Engineering Polymers, Fluoroproducts, and P& - Engineering plastics (Delrin) - Nylon pellets and filaments (Zytef) - Acrylic resins and molding compounds - Polyvinyl butyral (Butacite) - Teflon^ & Tefzef Approx. 2,400 employees (DuPonfs 2nd large 8UIOHSV EID121907 806Tziaia  1989 - Corrective Action or "HSWA" permit is byEPA Region III requiring Verification Investigation (VI) of 6 S^WMUs 1991 and 1992 - Conducted VI March 1997 - EPA commented on VI and req RR work plan for four SWMUs (Local LF & Injection Wells removed from consideration) 1998 and 1999 - Conducted RFI 98ZHOHSV  Riverbank Landfill Anaerobic Digestion Ponds Burning Grounds Polyacetal Waste Incinerator z,smoHSv -_-'' SWMU LOCATIONS >%,iE. .'iff'-.i )*, 88ZI 10HSV -/ SWMU LOCATIO  Operated from 1948 to mid- 1960s Measured 4,500 feet long by 150 feet wide Filled steep slope separating main plant terrace river floodplain Filled with general plant sold waste Closed by covering with soil, vegetation, and ri Today the RBL is densely vegetated Methylene chloride seep was the main area of concern - now controlled by collection and treatment system 68niOHSV AlaaerobaEc Digestion Operated from the mid-1950s to 1988 (three p Used for wastewater treatment Constructed with bentonite clay liners (i.e., pon & ff 3) and polyethylene sheet walls Closed by removing liquid, sludge, clay, and so underlying soils (5,400 cubic yards) and coveri soil and vegetation. 06ZIIOHSV  Operated from 1959 to 1990 Consisted to two, ten-foot deep concrete and fi brick-lined pits Used for the burning of off-spec polyacetal pol Area was closed by excavating and backfillingw clean soil and gravel I6ZI EOHSV Operated from 1948 to 1965 Used for the open burning of miscellaneous wa (e.g. plant trash, off-spec plastic, and organic liq Soils were excavated in 1974,1989, and 1990 (approximately 250 cubic yards) In 1990, the BG was leveled with clean fill to a for plant expansion, and a perimeter drainage d was installed. Mostly covered with buildings, concrete, and as Z6HIOHSV p i t Vw^-^ K-''"''''-"'^'-^ ^e^y -_-" Simple stratigraphy- Ohio River Terrace Depos Fine grained soils near surface and along riverb Thick sand and gravel unit: - Primary geologic unit - Overlies Permian age shale/sandstone bedrock - Contains site aquifer E6ZIIOHSV 176ZIIOHSV ' -wy '-vsy ^^' Site aquifer in sand and gravel formation Depth to groundwater is approximately 60 feet Groundwater flow direction is controlled by on production well system - East Well Field (seven wells-2000 gpm) - RanneyWell (800-1000 gpm) - LubeckWell Field (five welk-700 gpm) Pumping induces river recharge to aquifer, resu highweff yields S6ZHOHSV 96ZHOHSV (wa Groundwater Flow Model Potentioiiaetric Surface Contour Map 6ZllOHSV Screened VI data against Region III residential to define applicableanalyte list Constructed groundwater flow model to provid initial characterization of the site hydrogeologt system, and to identify additional data needs Refined site conceptual model to develop a comprehensive list of data needs Implemented a thorough investigation and mon of site SWMU soils and site groundwater condi 86ZUOHSV .  Describes the comprehensive field program Presents and discusses all site data Presents groundwater flow modeling results Presents screening-level human health risk eval by comparing maximum constituent concentrat exposure media to RBCs for industrial soils and drinking water Presents screening-level ecological risk evaluati characterizing site habitat within the RFI study Provides conclusions and recommendations fo further action 66ZUOHSV \!&^ InstaHed 24 new momtoring wells Sampled 40 monitoring wells and 5 production (two rounds) Drilled 35 soil borings, and collected 15 hand a 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 concept model OOtlIOHSV TOTO^ ISM ^?:^^ ^?%%-;':;^ ZOU10HSV H A ,-,'^^Sg^^a^lH^^ Analyte Carbon Tet MeCl PCE TCE FreonIB FC-143 Arsenic Barium Cadmium Lead Nickel Chromium EOCUOHSV ivr Tr-1 lI PWI BG fv v L . ^ ^ W ^'IKIUS i - ' f f , ' I E . S - SSSiS^ 1 ^- RBL/ADP * * * * * ^ * * * * * * * * * * * Potable Well ND ND ND ND ND * * * ND ND ND Pro W N N  Land Use: -- Onsite land use is industrial (current and future) -- Qffsite land use is mixed industrial, commercial, ope 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 WEIIOHSV * Exposure Pathway Evaluatio R S T C ;;()*; ElOHSV Offsite Migration: Controlled by Pumping TJrD1t C/^ 1 /U'^ai^jfU^ 1 Ci^SA'^C1/c^^iAI Study area included terrestrial and riveAank ha along the RBL/ADP No significant ecological resources were presen -- No critical or sensitive habitats -- No habitat reflective of public concerns (e.g., game habitat) -- No listed thrcatened or endangered species The absence of significant ecological resources to a lack of ecologicalexposures, and hence no significant ecological risks 90llOHSV '"Observed Arsenic values were comparable to site background level loenoHsv V.. PSL is the preliminary screening level for FC-143; AL is the action level fo The groundwater screening value was exceed in process wells only. 80EHOHSV  Soil concentrations of all constituents are well be their respective RBCs for industrial soils Potable well water concentrations are below scre levels for drinking water Process well water concentrations of two constitu (TCE, FG143) somewhat exceed drinking-water screening levels, but this water is not used for dr No unacceptable human health risks occur as a r site SWMUs No significant ecological receptors or pathways o anySWMU 60SHOHSV rittyre Continue production well pumping to maintai hydraulic containment Conduct long-term groundwater level monitor ensure continued capture of site groundwater Conduct long-temi groundwater quality monit of on-site potable well to ensure protection of human health Continue operation of MeCl seep collection an treatment system OlCllOHSV With the completion of the RFI, the DuPont Washington Works site SWMUs are well chara and wefl. understood. Existing containment and treatment programs protection of human health and the environme site SWMUs. DuPont intends to continue to actively manage site in a way that ensures the protection of hum health and the environment into the future. HEIIOHSV noiOHSv EID121936