Document 85KwzY7MvOKqoBQaX612KDd8d

AR226-2573 COMPILATION OF HISTORICAL C-8 DATA DUPONT WASHINGTON WORKS MAIN PLANT AND LANDFILLS Date; January 2002 Project No: D6WW7423 h ^ CORPORATE REMEOIAT10N GROUP An Alliance between DuPOnt and URS Diamond Bailey MM SHOta, Building 27 Wilmingtwi, Dtttwait 196G5 JS0015042 EID620777 TABLE OF CONTENTS 1.0 Introduction............,....,.......................,...............--.......................................... 1-1 1.1 Document Organization.......................................................................... 1-1 1.2 C-8 Historical Laboratory Analysis........................................................... 1-1 1.3 Physicochemical Data for Animonium Perfluorooctanoate (C-8)................ 1-2 1.4 References................................................................................................. 1-2 2,0 Washington Worta Main Plant ...........................,...........................................,.,.....2-1 2.1 Introduction..,..,.....,............................-..--......,..........................................2-2 2.2 Environmental Setting...,....................................,...,.,.,.,....,,...........,...............2-3 2.2.1 Geology............,..,.,.,.,...................................,..,,..,............................2-3 2.2.2 Hydrology, Hydrogeology and Groundwater Flow..........,..,............2-3 2.3 Water Quality ..................................,..............................................................2-6 2.3.1 Surface Water Quality .....,..,.,.,................................................,,.......2-6 2.3.2 Groundwater Quality .......,,..,.........,.............................................,..,,2-6 2.3.3 Drinldng/Tap Water Quality .................,.,...,..,.,-.,....,.......................2-7 2.4 Site Conceptual Model ..,................................................................................2-7 2.5 DataGaps........-,.,...,....,...........................................,..-,...........,..................2-8 2.6 References..................................................--..................,..,...-,,,....,...............2-8 3.0 Local ]LandfiU....................................-.....,,,...,...........................:.................,..........3-l 3.1 Introduction ,......,...........................................-,......,........................................3-2 3.2 Eilvir&mnentalSetting.......,..,............,.................................,..........................3-2 3.2.1 3.2.2 Geology.................,,....................................,...,.,....,......,,......,........,..3-2 Hydrology, Hydrogeology and Groundwater Flow..........................3-3 3.3 Water Qualiy....,.................................................,..,.,.......,.............................3-4 3.3.1 Surface Water Quality ......................................................................3-4 3.3.2 Groundwater Quality .....................................,......,....,......,...............3-4 3.4 Site Conceptual Model...................,..,...,,..,....................................................3-5 3.5 DataGaps..........................................,........,.................................................-.3-6 3.6 References ....,..,..........,...,........1......................,..,.,.,,..,..........,.........................3-6 4.0 Letart Landfill........................... ,.................,......,.....................................,.............,4-1 4.1 Introduction ......-...............-..............,,.......,,.........................;..................,,,,,,,, 4-2 4.2 Environmental Settmg.........................................,..,......................................,4-2 4.2.1 Geology.........................................,,..................................................4-2 4.2.2 Hydrology, Hydrogeology and Grovndwater Flow..........................4-3 4.3 Water Quality ...,.........................................,...................................................4-4 4.3.1 Surface Water Quality ..............................,..........,............................4-4 4.3.2 Groundwater Quality.......................................,.,..............,...............4-5 4.4 Site Conceptual Model........................ ,..........................................................4-6 4.5 DataGaps.....,-................-.........-...,,,..................................-.....................,.4-7 4.6 References.............................;.......,.....,.,.................................................,......4-8 JS0015043 EID620778 Main Plant and Landfills Table of Contents 5.0 Dry Run Landfill .......................................................................................... ..5-1 5.1 Introduction........-....,...........--................................,...,............."......--....-- ..5-2 5.2 Environmental Setting........................................................,,,,..,,,,,,,,.,,........ ..5-2 5.2.1 5-2.2 Geology.......................................................................................... ..5-2 Hydrology, Hydrogeology and Groundwater Flow,.,....,....,,......... ..5,3 5.3 Water Quality................................................................................ ..5-4 5.3.1 Surface Water Quality ............................................................. ..5-4 5.3.2 Groundwater Quality ................................................................ ..5-4 5.4 Site Conceptual Model................................................................................ ..5-5 5.5 Data Gaps.................................................................................................. ,.5-6 5.6 References.......... ...........................,,...,,...,,.,,...--........................................ ,.5*6 TABLES Table 2.0 Table 2.1 A Table 2.1 B Table 2.1 C Table 3.0 Table 3.1A Table 3,1 B Table 4.0 Table 4.1 A Table 4.1 B Table 5.0 Table 5.1 A Table 5.1B Washington Works Main Plant Monitoring Wells Construction Data Washington Works Main Plant Analytical Data Table - Surface Water Washington Works Main Plant Analytical Data Table - Groundwater Washington Works Main Plant Analytical Data Table - Drinking Water Local Landfill Monitoring Wells Construction Data Local Landfill Analytical Data Tables - Surface Water Local Landfill Analytical Data Tables - Groundwater Letart Landfill Monitoring Wells Construction Data Letart LaodFdl Analytical Data Tables - Surface Water Letart Landfill Analytical Data Tables - Groundwater Dry Run Landfill Monitoring Wells Construction Data Dry Run Landfill Analytical Data Tables - Surface Water Dry Run Landfill Analytical Data Tables - Groundwater Figure 1.0 Figure 2.0 Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4A Figure 2.4B Figure 2.4C Figure 2.4D FIGURES Solubilities of CyF^ COOM in Water as a Function of Temperature Washington Works Main Plant Location and SWMU Map Washington Works Main Plant and Local Landfill 1-mile Radius Map Washington Works Main Plant Monitoring Well and Surface Water Sample Location Map Washington Works Main Plant Cross Section Location Map Washington Works Main Plant Cross Section A-A' Washington Works Main Plant Cross Section B-B' Washington Works Main Plant Cross Section C-C' Washington Works Main Plant Cross Section D-D' Compilation of hittBiy dale Draft 2rev.doc Mar. 11,02 Wilmtngton. DE JS0015044 EID620779 Main Plant and Landfills Table of Contents Figure 2.4E Figure 2.4F Figure 2.5A Washington Works Main Plant Cross Section E-E' Washington Works Main Plant Cross Section F-F' Washington Works Main Plant Groundwater Elevation Map - November 2000 Figure 2.5B Washington Works Main Plant Groundwater Elevation Map February 1999 Figure 2.5C Washington Works Main Plant Groundwater Elevation Map - November 1998 Figure 2.6A Washington Works Main Plant C-8 Concentration Map - February 1999 Figure 2.6B Washington Works Main Plant C-8 Concentration Map - November 1998 Figure 3.0 Local Figure 3.1 Local Figure 3.2 Local Figure 3.3 Local Figure 3.4A Local Landfill Location Map Landfill andWashington Works Main Plant 1-mile Radius Map Landfill MonitoringWell andSurface Water Sample LocationMap Landfill Cross Section Location Map Landfill CrossSection A-A' Figure 3.4B Local Landfill Cross Section B-B' Figure 3.5A Local Landfill Groundwater Elevation Map - November 2001 Figure 3.5B Local LandfillGroundwater Elevation Map - December 2000 Figure 3.5C Local Landfill Groundwater Elevation Map - November 1999 Figure 3.5D Local Landfill Groundwater Elevation Map - November 1998 Figure 3.5E Local Landfill Groundwater Elevation Map - November 1997 Figure 3.5F Local LandfillGrouadwater Elevation Map - December 1996 Figure 3.5G Local Landfill Groundwater Elevation Map - December 1994 Figure 3.6A Local Landfill C-8 Concentration- May 2001 Figure 3.6B Local Landfill C-8 Concentration- May 2000 Figure 3,6C Local Landfill C-8 Concentration - May 1999 Figure 3,6D Local LandfillC-8 Concentration - May 1998 Figure 4.0 Letart Figure 4.1 Letart Figure 4.2 Letart Figure 4,3 Letart Figure 4.4A Letart Landfill Location Map Landfill1 -mile Radius Map LandfillMonitoringWell andSurface Water Sample Landfill Cross SectionLocation Map LandfillCross Section A-A' Location Map Figure 4.4B Letart Landfill CrossSectionB-B' Compilation of histolydata Draft DE iii 2rev,doc Mar. 11.02 Wllmlngton. JS0015 EID620780 Main PI ant and Landfills Table of Contents Figure 4.5A Figure 4.5B Figure 4.5C Figure 4.5D Figure 4.5E Figure 4.5F Figure 4.6A Figure 4.6B Figure 4.6C Figure 4.6D Figure 5.0 Figure 5.1 Figure 5.2 Letart Landfiil F-Zone Groundwater Elevation Map - November 2001 Letart Landfill F-Zone Gnnindwater Elevation Map - January 2001 Letart Landfill F-Zone Groundwater Elevation Map - October 1999 Letart Landfill F-Zone Groundwater Elevation Map - October 1998 Letart Landfill F-Zone Groundwater Elevation Map - December 1994 Letart Landfill F-Zone Groundwater Elevation Map - December 1992 Letart C-8 Concentration Map - July 2001 Letart C-8 Concentration Map - January 2000 Letart C-8 Concentration Map - July 1999 Letart C-8 Concentration Map - November 1991 Dry Run Landfill Location Map Dry Run Landfill 1-mile Radius Map Dry Run Landfill Monitoring Well and Surface Water Sample Location Map Figure 5.3 Dry Run Landfill Cross Section Location Map Figure 5.4A Figure 5.4B Dry Run Landfill Cross Section A-A' Dry Run Landfill Cross Section B-B' Figure 5.5A Figure S.SB Figure 5.5C Figure 5.5D Figure 5.5E Figure 5.6A Dry Run Landfill Groundwater Elevation Map October 2001 Dry Run Landfill Groundwater Elevation Map October 1999 Dry Run Landfill Groundwater Elevation Map October 1998 Dry Run Landfill Groimdwater Elevation Map October 1993 Dry Run Landfill Groundwater Elevation Map April 1992 Dry Run C-8 Concentration Map Bedrock Wells July 2000 Figure 5.6B Dry Run C-8 Concentration Map Bedrock Wells July 1999 Figure 5.6C Dry Run C-8 Concentration Map Bedrock Wells July 1997 Figure 5.6D Figure 5.6E Dry Run C-8 Concentration Map Overburden Wells Dry Run C-8 Concentration Map Overburden Wells July 2000 July 1999 Figure 5.6F Dry Run C-S Concentration Map Overburden Wells May 1998 Appendix Consent Order APPENDIX Compilation of history data Orall Zrev.dgc Wilmlnston, DE Mar, 11,02 iv 7S0015046 EID620781 MrinptoiandLmdfite ..____ . Introduction 1.0 INTRODUCTION A multi-media Consent Order was entered into between the West Virginia Department of Environmental Protection (WVDEP), the West Virginia Department of Health and Human Resources-Bureau for Public Health (WVDHHR-BPH) and DuPont on November 14,2001. A copy of the Consent Order (Order No. GWR-2001-019) is contained in Appendix 1. The Consent Order identified a series of requirements to be performed by the Parties (WVDEP, WVDHHR-BPH, and DuPont) in order to determine whether there has been any impact on human health and the environment as a result of releases of ammonium periluorooctanoate (C-8), CAS Number 3825-26-1, to the environment from DuPont operations at the Washington Works main plant and the associated landfills (Local, Letart and Dry Run). The C-8 Oroundwater Investigation Steering Team (GIST) was established in the Consent Order to oversee investigations and activities that will be conducted to assess the presence and extent of C-8 in drinking water, groundwater, and surface water at and around the main plant, and the Local, Letart and Dry Run Landfills. Pursuant to Attachcnent A of the Consent Order, three tasks will be performed by DuPont and evaluated by the GIST, Tasks A, B, and C. This report addressed Task B. The primary objective of Task B is to develop and implement a monitoring plan that detennhes the presence and extent of C-8 in drinldng water, groundwater and surface water in and around the main plant, and toe Local, Letart and Dry Run Landfills, and to provide a compilation of available groundwater/surface water monitoring results and hydrogeotogic characterization data for each location. This document was prepared to meet the data compilation objective. 1.1 Document Organization Sections 2.0,3.0,4.0, and 5.0 present the historical data available for the main plant and the Local, me Letart and the Dry Run Landfills, respectively. Each section includes text, tables, and figures specificto the site being discussed in that section. At the end of each sectioni data gaps are identified. The same outline is used for each section. Data presented in each section includes information (to the extent that information was available) as requested in Table A-1 of the Consent Order, hi addition, supplemental information is provided as needed to develop and present a site conceptual model for the four locations discussed. 1.2 C-8 Historical Laboratory Analysis of C-8 The analytical method, method detection limit, and laboratory utilized for C-8 analysis has changed over time. Prior to 1991, DuPont performed C-8 analysis at the DuPont Experimental Station in Wilmmgton, Delaware. In 1991, when the S.CRA Verification Investigation was conducted, the analysis was contracted to the CHzMHill Laboratory in Montgomery, Alabama. Both labs used a. Gas Chromatography/ElectrODCapture Compilation of history data Draft Zrav-doc Mar. 11,02 1-1 Wllniltiglon. 06 JS0015047 EID620782 Main Plant and Landfills__________________________________________Introduction Dectector (GC-ECD) based analytical method with detection limits for C-8 that ranged froiaO.ltol.Oug/1. CKkMHill conducted C-8 analysis for DuPont into the fall of 1998 when the laboratory ceased operation. At that time, DuPont had completed one round of analysis for the RCRA Facility Investigation (RFI). The analytical work was transferred to Lancaster Laboratories, Lancaster, PA, for the RFI second round analysis in February 1999. Lancaster Laboratories continued to conduct C-8 analysisusing GC-ECD for DuPont until October 2001, when development and testing was initiated on a new analytical method developed by Exygen Research, Inc. (located in State College, PA) that utilizes Liquid Chromatograpfly/Tandem Mass Spectrometry (LC/MS/MS). DuPont adopted the use of LC/MS/MS for C-8 analysis in November 2001. 1.3 Physicochemical Data for Ammonium Perfluorooctanoate (C-8) C-8, also identified as PC-143, is a fluorinated surfactant used in the fluropolyoier manufacturing at the main plant. Figure 1.0 shows the solubilities of C7Fi5 COOM in water as a function of temperature (Figure 6.9 in Kissa, 1994). The following summary lists the physicochemicaldata available for C-8 (Kissa, 1994); 0 Molecular Formula = CF3(CF;.)6COO"NH4+ Q Molecular weight = 431.098 g/mole 0 LDsa acute oral rat = 680 ing/kg a BCF=1.8 Q pH - 5 (0.5% aqueous) Q pKa'=2.8(-COOH) Q Melting Point = 56-58C (-COOH) Q COD = 700 mg/kg Q Koc25 0 Water Solubility > 1000 mg C-8/L Q Vaporpressure (at 22C) = 7.1 x lO"05mm Hg 0 Kraft Point = 2.5 C Q Critical Micelle Concentration = 33 mmol/L LD>! Lethal Dote SB- D9t (Wing 50% ptobablHlyBfeiustog daitti BODs; Biochcniic.ii Oxygen Dnaitid - Standard niciBlinmcnt is made for S daysat 20 (iegrets C BCF: Bioconcentration Factor pKa; NcgBtiw log of the i(iBBtiin tensialU ~ Measure oftridity or Kid slienglh COO: ChemlctI Olygcn Demand KM: Organic Curbon PiBtitioBing CaEffidaii 1.4 References KJSsa.E. 1994. Fluorinated Surfactants. New York: Marcel Dekker, Inc. Cofnptellon of Mtoiy data Draft 2w.doc Mar. 11, Q2 1.2 Wilmlngton, DE JS0015048 EID620783 35 25 T (0 o^c T 0 s. 0 > 0 V) 0 81 0 -J .. 5.2 3.4 3.6 1/Tx 10s Figure 1.0 Solubilities of C^s COOM in water as a function of temperature (Kissa, 1994). JS001504& EID620784 a,tifiii\a}\ ^'^;;.>;i;;:;:;;:i,y 9 ^;;!;;;;^'!'i.r 'f Main Plant and Landfills Washington Works Main Plant 2.0 WASHINGTON WORKS MAIN PLANT Environnienta.i S Site Conceptual; Rderencts,..,..., Table 2.0 Table 2.IA Tablt2.1B Table 2.1 C Flgme2,0 Pigme 2.1 nEuie 2.2 Figure 2J PifwelAA. Figuie2,4B Fil 2.4C Rguis 2.4D Figun! 2.4E nguie UP riffles 2jA FipBC Z.SB Piguie 2JC Figure 2.6A Figure 2,6B Tables Wgihjngton Worics Man Plant Monitoring Wells CoiistnietiBi Datt Wtehinglon Works Main Plant Aaalyiteal Dai Table- Surf{(i Waiw Wiuhfagton Woria Main Plant Analyticiil Data Table Gnsandwiitcr Waslitogion Works Mah Plant Analytical Data Table - DmiUng/Tap Water Figures Wa^glDBWMka tern PtotLoiaiioil and SWMU Map Washington Works Main Plant and LOCBI Landfill 1-mite Radius Map Wiuhlngtoa Wotks Main Plant Monitoring Well and Surface Wale Sample Location Map Wathington Wwls Main Plant Cross Sestio!! Location Map Waihinpon Works Miiin Plani Cinis Seciion A-A' WtshingtTOWorlts Main Plant Crosi SwtiMi B-B' Washington WcrltB Main Plant Cross SecUon C-C' WashlngtOBWwka Main Plant Class Seclim D-D' Washington Worts Main Plant Cross SectitB! E-E" Washington Worta Main Plant Cross SecnoB F-F' Washington Weiks Main Plant Gioiindwater Elevation Map - November 2000 Washington Waiks Mani PlaBi OnnBdwatct Elltation Map. FeBnai? 1999 WMhington Winks MB Plant Oroundwai?r Elerotion Map. Nmwbvt 1998 Washington Works Main Plant C-8 Concentration Map - February 199 Washington Worlcs Min Plant C-8 Coneentratiini Miip NovembBr 1998 -.-.-.-2-3 ........2.6 ...,,. 2-7 ,,.,,,,.. 2-8 .........2.8 Compilatbn of historydata Draft Zrev.dae Mar. 11,02 Wtliiilngton.DE 2.1 JS0015050 EID620785 Main plant and Landfills________.____ Washington Works Main Plant 2.1 Introduction The Washington Works Main Plant (main plant) is located along the Ohio River in Washington, West Virginia, approximately seven miles southwest ofParkersburg, West Virginia (Figure 2.0). A water use and well survey is currently being conducted for the area within a 1-mile radius of the main plant and Local Landfill property boundaries (Figure 2.1). Significant historical bydrogeologic and groundwater quality data for C-8 at the main plant i$ available from previous investigations that have been conducted. The most significant studywas a Resource Conservation and Recovery Act (RCRA) Facility Investigation (Ml) conducted in the fall of 1998 on four Solid Waste Management Unite (SWMUs) at the main plant to satisfy requirements of the RCRA Hazardous and Solid Waste Amendments (HSWA) Permit Number WVD 04-587-2591 (DuPont, 1999). A brief description of each of the SWMUs investigated is presented below. SWMU locations are shown on Figure 2.0. Q SWMU A-3, Riverbank Landfill: The Riverbank Landfill is about 4,500-feet long and lies along the northern edge of the site near the Ohio River. It was operated between 1948 and the late 1960s and received powerhouse ash, incineration ash, plastics, rubble, and plant trash. After closure, it was covered with 6 to 35 inches of soil. Currently, me Riverbank Landfill is covered with dense vegetation (on the sloped area) or by buildings and pavement in the manufacturing area. Q SWMU B-4, Anaerobic Digestion Ponds (Digestion Ponds): Three former digestion ponds are co-located within a portion of the Riverbank Landfill. One pond dates from the 1950s and two others from the 1970s. The ponds received waste from the fluorocarbon manufacturing process (including C-8) until 1988, when the pond contents and upper few feet ofc!ay liner and pondbenn material were removed and disposedof off-site. The pond area was backfilled and capped with topsoil, and the area is currently vegetated with grass. Q SWMU C-6, Polyacetal Waste Incinerators (Waste Incinerators): The former Waste Incinerators consisted of two brick-lined pits in the western portion of the manufacturing area. The Waste Incinerators operated between 1959 and 1990. The Waste Incinerators have been excavated and backfilled with clean soil. Q SWMU H-14, Burning Ground: The Burning Ground is located in the central portion of the manufacturing area and was operated between 1948 and 1965. Since 1990, the Burning Ground has been leveled, backfilled with clean fill and gravel, and covered by buildingsand asphalt A previous Verification Investigation (VI) found evidence of releases of C-8 to soil and groundwater at the Riverbank Landfill, Digestion Ponds, and Burning Ground (DuPont 1992). Little evidence of releases were found in soil at the site of the fonner Waste Incinerators, Further investigationsand evaluations were performed during the RFI to dctennine the extent of releases in groundwater. Compilation of histoly data Diaa Ziw.floc Mar. 11,02 2-2 Wllffilnston. DE JS0015051 EID620786 Main plantand landfills______________Washington Works Main Plant Plant-wide groundwater sampling was also conducted during two separate monitoring events, the first in November 1998 and the second in February 1999, during the RJFI. The sampling events focused on evaluating groundwater quality at existing and newly installed wells associated with the Burning Ground and Riverbank Landfill/ Digestion Ponds SWMUs. All plant wells sampled during the KFI were analyzed for C-8. C-8 was detected m all groundwater samples. C-8 concentrations and the extent m groundwater is discussed in Section 2,3 Water Quality. 2.2 Environmental Setting 2.2.1 Geology The geology of the main plant is shown on six geologic cross-sections developed during the VI (DuPont, 1992) and revised based on additional findings from the RFL The locations of the geologic cross-sections are shown in Figure 2.3. Two east-west crosssections, A-A' and F-F', are shown on Figures 2.4A and 2.4P. Four north-south crosssections, B-B', C-C', D-D', and E-E' are shown on Figures 2.4B, 2.4C, 2.4D and 2.4E, respectively. The cross-sections were developed from detailed geologic logs recorded during the VI and RFI, and from less detailed historic geologic logs from test and production wells and geotechnical borings drilled in the late 1950s through the early 1980s, Some monitoring wells shown in Figure 2-3 were later abandoned. The current site map (Figure 2.2) shows the monitoring wells that currently exist at the site. The main plant rests on Quaternary alluvial terrace deposits in the Ohio River Valley. The alluvial ten-ace is topographically flat and lies approximately 50 feet above the Ohio River, which flows east to west past the main plant (see Figure 2.0). The alluvial terrace is underlain by a flat, river-scoured bedrock surface oftfae Dunkard Series Aat rises Steeply and outcrops in the southern edge of the site to form the valley wall. The Quaternary alluvium ranges from 60 to 100 feet in depth and consists of coarsening downward unconsolidated river deposits of poorly to well-sorted, brown and gray sand, silts, clay and gravel. The Dunkard Series bedrock consists primarily of red and varicolored sandy shale; gray, green and brown sandstone; and minor beds of coal, claystone, black carbonaceous shale, and limestone. The average river water elevation is about 580 feet above Mean Sea Level (MSL) and the elevation of the Ohio River terrace deposits under the main plant are about 630 feet above MSL. Due to riverbank undercutting, some slumping of clay and silt exists along the northern boundary of the main plant along Ae river's edge. Figure 2.4C shows an example of the relationship of fill and clay layers along the riverbank. 2.2.2 Hydrology, Hydrogeology and Groundwater Flaw Hydrology Regional water needs are primarily satisfied by the Ohio River and Little Kanawha River near Parkersburg. These sources provide water to the cities of Parkersburg, Complatton of history data Draft aw/.doe Mar. 11.02 3>-3 Wllmlrgton,DE iJS0015052 EID620787 Main plant and landfills______Washington Works Main Plant West Virginia and Belpre, Ohio. In less populated areas (i.e., near the mate plant), the local communities receive water from small local water companies that obtain their water from production wells screened in the Quaternary river alluvium. Surface water at the mate plant discharges through drains and storm sewers, and drainage swales. Seeps located along the riverbank may originate from precipitation that has infiltrated topsoil or fill and that flows along the top of the underlying shallow clay and dischargesalong the riverbank. Two drainage swales, one located in the facility's southwest comer, and the other located on the extreme eastern end of the facility, convey surface nmoff during rainy weather to the Ohio River. During dry weather, the drainage swales are dry. Hydrogeology Regional groundwater suppliesare obtained from the Dunkard Group bedrock and Ohio River alluvial terrace deposits. The saturated portion of the Ohio River alluvial terrace depositscomprise the principal regional aquifer used for water supply purposes. Production wells completed in this aquifer have been known to yield up to 500 gallons per minute (gpm) (Schute. 1984). Based on these high yields, numerous industrial and commercial water supply companies obtain water from the alluvial aquifer. The yield from alluvial aquifer wells is related to the well's position with respect to the river, as well as formation grain size and thickness. The Ohio River alluvial terrace deposits contain a single key aquifer underlying the maim plant. The water table occurs at a depth of about 60 to 70 feet below ground surface in the main plant area. The saturated zone is approximately 30 to 40 feet thick, extending to the surface of the underlying Dunkard Group, The on-site production water wells completed in the site aquifer yield 200 to 450 gpm. The underlying Dunkard Group is not a major aquifer. The upper zone of the Dunkard Group (Washington Formation), which consists primarily of shale and silt, likely bounds the lower extent of the site aquifer, hi addition, regional groundwaler communication between the Ohio River and bedrock will likely result m upward gradients to the alluvial aquifer, Gioundwater quality in the alluvium in this region tends to be naturally poor, having the highest median chloride, sulfate, hardness (as calcium carbonate), iron, and manganese concentrations of all hydrogeologic units in the region (Schultz 1984). Water from the alluvium generally is a calcium bicarbonate type, with near neutral pH and high dissolved solids content, Natural recharge to the alluvial aquifer comes from various sources, including: U Infiltration of precipitation falling directly on the alluvium Q Lateral movement of the river water through the alluvium via permeable sand and gravel zones 0 Seepage from stream tributaries that discharge to the Ohio River The maximimi amount of water available to the alluvium depends on the degree of hydraulic connection to the river. The degree of hydraulic connection is a function of the permeability and thickness of the riverbed, permeability and thickness of the alluvium, and hydraulic gradient between the groundwater and the river. Pumping of on-site active CoroplaltonofhtetoiydataOraBZrev.doc Mar. 11,02 2-4 Wllmington, DE JS0015053 EID620788 Main plant ana Lanams___________________Washington WorksiJMain Plant well fields near and parallel to the river (i.e., the Ranney Well, the DuPont-Lubeck Well Field, and the East Well Field shown in Figure 2.2) towers the groundwater level in the alluvial aquifer to below river stage. This induces water from the river to flow into the alluvium toward the wells, which replaces water pumped from storage in the aquifer, and . helps sustain high-yield pumping wells. Oroundwater Flow Groundwater generally flows to the south-southwest in the alluvial aquifer. However, groundwater elevations, flow directions, and flow rates on-site are strongly influenced by the Ohio River and by pumping of on-site production welts. The on-sile production wells include the Ranney Well, a radial collector well. which pumps 800 to 1,000 gpm; the seven, wells in the East Well Field, which pump a combined average rate of 2,000 gpm; and the five DuPoart-Lubeck wells, which pump about 700 gpm combined. Groundwater elevation contour maps for the alluvial aquifer developed from data measured in November 2000, February 1999, and November 1998 are presented as Figures 2.5A, B, and C, respectively. The direction of groundwater flow is indicated by the flow arrows. As shown on Ac groTOidwaterelevation contour maps, groundwater flow in die northeast part of the site is toward the East Well Field wells. In the norfhcentoal portion of the site, groundwater flow is toward the Ranaey Well. In the central and western portion ofthfi site, groundwater flow is south-southwest towards the DuPontLubeck Well Field. Pumping of the production wells (Ranney Well, East Well Field, and the DuPont-Lubeck Well Field) eliminates off-site migration of impacted groundwater that may originate from the SWMU areas. Additional groundwater elevation data was obtained from the General Electric (GE) property located to the west of the main plant. Data from the main plant and GE were used in calibrating the Washington Works groundwater model (DuPont, 1999). The groundwater model conclusions indicated that groundwater from the main plant area is contained to the DuPont property by operation of the site production wells. In a 1990 hydrogeologic assessment, production well specific capacity testing of me DuPont-Lubeck Well Field and the East Well Field was conducted. The results were used to calculate fee transmissivity and the hydraulic conductivity of the alluvial aquifer (DuPont 1990). In the vicinity of the DuPont-Lubeck Well Field, transmissivity values tanged between 114,900 and 127,500 gallons per day per square foot (gpd/ft2).In the vicinity of the East Well Field, the transmissivity values ranged between 16,050 and 50,000 gpd/ft2.Hydraulic conductivity values ware calculated from the transmissivity values for the East Well Field. For Wells AX13-PW01 and AZ13-PW01, the hydraulic conductivity values ranged from 0.013 to 0.055 centimeters/second (cm/sec) and from 0.01 to 0.049 cm/sec, respectively. 'Using the hydraulicconductivity values from the 1990 study and the hydraulic gradient values determined from groundwater elevations measured in 199D and assuming an effective porosity value for sand and gravel of 35 %, the groundwater flow velocity for several well pairs was calculated. The groundwater flow velocity was estimated at 5 feet/day (fl/d) between monitoring wells T13-MW01 and L18-MW01 in the southwest portion of the site. A groundwater flow velocity of 3 fVd was estimated between monitoring wells P06-?vfW01 and K14-MW01 in the western central portion of the site. Compilation of hwtay data Drall 2rev.doe Mar. 11,02 2.5 Wllmlngton, DE JS0015054 EID620789 Main plant and LantHiiis ________________Washington Works Main Plant In the eastern portion of the site, a groundwater flow velocity of 2.5 ft/d was estimated for the site aquifer between monitoring wells AL10-MW01 and A009-MW01. Groundwater seeps at the Rjverbank Landfill were identified and sampled during the VI (DuPont 1992). An active French-Drain groundwater collection has been in operation at the Riverbank Landfill since 1991. The RFI verified that the collection system effectively captures water at the seep area. 2.3 Water Quality 2.3.1 Surface Water Quality Historical surface water C-8 concenfrations are presented in Table 2.1A. Surface water sample locations are shown on Figure 2.2. Surface water C-8 concentrations were measured in 2000 and 2001 at two outfalls, 002 and 005 and at two river locations. The outfalls have been sampled monthly since February 2001, Outfall 005 C-8 concentrations have ranged from 1,43 ug/I to 199 ug/1. while Outfall 002 C-8 concentrations overall have been much lower, ranging from 0.436 ug/1to 8.54 ug/1. In general. Outfall C-8 concentrations have significantly declined in 2001. This is the result of installation of a carbon adsorption treatment system in the fluropolymers process. The system is designed to remove a major percentage of C-8 from the process wastewater. 2.3.2 Oroundwater Quality Concentrations of C-8 in groundwater sampled at the main plant have been evaluated since 1$91 (Table 2.1 B), however, the wells sampled and the sampling frequency has been variable. Some wells have been monitored annually since 1996 and others have been monitored quarterly starting in January 2001. Two plant-wide gtoundwatcrsampling events were conducted as part of the RFI (November 1998 and February 1999) and are discussed below. The sampling events focused on evaluating groundwater quality from existing and newly installed wells associated with the Burning Ground and Riverbank LandfilVDigestion Ponds SWMUs. All plant wells sampled during the RFI were analyzed for C-8, At the Riverbank Landfill/Digestion Ponds area (in the western portion of the Riverbank Landfill), C-8 was detected m groundwater and previous seep samples. Figures 2.6C and 2.6D depict the well locations and results for C-8. Measured concentrations ranged from O.I to 13,600 ug/L. Concentrations were below 40 ug/L in 28 of the 37 wells sampled; in the other 9 wells, maximum concentrations ranged from 380 to 13,600 pg/L, The highest concentrations were measured in monitoring wells P04-MW02 and R04-MW02, near the Digestion Ponds area, The RFI C-S concentration values were utilized for contouring. Isoconcentration maps were prepared and are presented m Figures 2.6A and 2.6B. Compilation of hittoy data Draft Zrev.doc Mar. 11.02 Wilnnington, DE 2.6 JS0015055 EID620730 Main plant d Landniis___________________Washington Works Main Plant 2.3.3 Drinking/Tap Water Quality Production Well AM07-PW01 (historically known as well 336) supplies potable water to the main plant. C-8 concentrations in drinking/tap water have been measured at four distribution points on the plant periodically since May 1999 (Table 2.1C). Concentrations ranged from 0.213 ug/1to 0.589 ug/1. C-8 concentrations detected at three samplingpoints in the distribution system on October 11,2001 were 0.507,0.45, and 0.423 ug/l, respectively. No obvious trends are seen in the data. 2.4 Site Conceptual Model The main plant site conceptual model describes the potential exposure routes for cuirent and future human and ecological receptors. Potential exposure routes were evaluated and classified as complete or incomplete. Direct exposure to C-8 bearing materials contained within the SWMUs is minimal or non-existent, because these materials have been removed and regraded or paved (Burning Ground, Waste Incinerators, and Digestion Ponds) or covered and vegetated. Therefore, contact with these materials is considered to be an incomplete exposure pathway. A large portion of the plant site is covered with asphalt and concrete. Hence surface water contact with C-8 impacted soils or groundwater is not likely in these areas. Therefore, surface water contacting C-8 impacted soils is considered to be an incomplete exposure pathway. Much of the precipitation falling on site is routed toward drains and storm sewers, which ultimately discharge into the Ohio River. Precipitation falling on die riverbank slope either percolates into die soil or runs off to the river. The seeps that occur in places along the riverbank are probably caused by percolated water that accumulates above the slumped, low-permeability clay and silt of the Ohio River deposits that underlie topsoil and fill along the riverbaok. Contact with impacted seep water is considered to be an incomplete exposure pathway due to the active trench-drain groundwater collection system. Direct exposure to youndwater impacted by C-S is also considered to be an incomplete pathway because groundwater is located at about 60 feet bgs. The only potential contact route for groundwater is via contact with water pumped from production wells. Water pumped from production wells is used for two purposes, supplying drinking water and providing industrial process water. Well AM07-PWOI is one of three production wells that provides drinking water to the main plant. Other wells are A008-PW01 and AQ09-PW01. AM07-PWOI was sampled eight tunes. Measured concentrations of C-8 in this well suggested that this exposure pathway is considered to be complete. However, average concentrations of C-8 in drinkingwater at point of use (which is a mixture of water from the three wells) will be lower than the maximum concentrations detected in any single well. Contact with impacted drinking/tap water is a complete exposure pathway. C-8 was detected in production wells providing industrial process water (Kl 6-PWO 1, V05-PW01, and L04-PW01). The maximum concentration of C-8 was detected in well K16-PW01 (16.2 ug/1). Water from these wells is not used for drinking, but rather for industrial processes including non-contact and contact cooling water, fire water, process Compilation of history data Draft Zrev.doc Mar. 11.02 2-7 Wllmlogton, DE iTSOOlSOSS EID620791 Main Plant and Landinis___________._____Washington Works Main Plant water, conversion to demineralized water to generate steam, and/or consumption in the manufacturing processes. There is a potential for limited contact, however, this contact is expected to be minimal. Average concentrations of C-8 in process water at me point of use (which is a mixture of water from several production wells) will be lower than maximum concentrations detected in any single well. Therefore, while this exposure pathway is complete, it is considered to be minimal. The RFI ecological evaluation focused on identifying whether significantecological resources may be exposed to site-related constituents released from the SWMUs. This evaluation concluded that surface soil at the Riverbank Landfill/Digestion Ponds is the only potential ecological exposure medium within the RFI studyarea. Surface water contact with C-8 impacted soils or groundwater is not likely because the Waste Incinerators and Burning Ground SWMUs acre covered with gravel, asphalt, or buildings and do not provide ecological habitat Subsurface soil (greater than 2 feet) and groundwater are not exposure media of concern for ecological receptors, and grouiidwater does not dischargeto surface water at me site. 2.5 Data Gaps The following date gaps were identified for the main plant: 0 Additional monitoring wells are needed to farther delineate C-8 concentrations m grouadwater and to evaluate groundwater flow directions, particularly for groundwater flow in the bedrock below the unconfined alluvial aquifer. Q Continued refinement of the groundwater model for the main plant is required to reevaluate that groundwater capture by the pumping wells is occurring at the site and mat no off-site migration of C-8 impacted groundwater is occurring. Q Surface water quality in Ac Ohio River should be evaluated. A separate work plan is currently being designed to address this issue. Activities to fill me date gaps will be proposed and discussed in the work plaa. 2.6 References DuPont. 1990. Washington Works 1990 Preliminary Hydrogeologic Assessment. Solid Waste & Geological Engineering Department. _ _,, ._. 1992. Verification Investigation E.I. DuPont de Nemours Co. Washington Works April 1992, (Vol.1). ___. 1999. RCRA Facility Investigation Report, DuPont Washington Works, June 30, 1999. Corporate Remedialion Group. Haskell Laboratory. 1991. Ammonium Perfluorooctanoate (FC-143). Compilation of history data Draft Zrev.doc Mar, 11, 02 2-B WIlinington.DE JS0015057 EID620792 Main plant and landfills__________________Washington Works Matn Plant Schultz, R..A. 1984. Groundwater Hydrology of the Minor Tributary Basins of the Ohio River, West Virginia. Compilation of history data Draft 2rBV.doc Mar. 11,02 Wllmtngton, DE 2.9 JS0015058 EID620793 Table 2.0 Monitoring Well Construction Data DuPont Washington Works Main Plant Washington, WV Monitoring Wells New ID OldID Q04.MW02 QOS-MWOl P06-MW02 P08-MW01 N13-MW01 M16-MW01 AOOS-PWOl AQ09..PW01 AT10-PW01 AV11-PW01 AX13-PW01 AM07-PW01 AZ13-PW01 L04.PWOI L17-PW01 K18-PW01 K19^PW01 K.16-PV01 J17.PW01 V05-PW01 J08-MW01 Q07-MW01 Z07-MW01 G10-MW01 T13-MWOI U16-MW01 A009-MW01 L18-MWOI V09-MW01 N04-MW01 P06-MW01 AR09-MW01 AX12-MW01 A007-MW01 AJ06-MW01 A008-MW01 Y05.MW01 AC05-MW01 AL10-MW01 Ron's MW-1 Ron's MW-2 Ron's MW-3 Ron'$ MW-4 Ron's MW-5 Ron's MW.6 331 332 333 334 335 336 337 , GALLERY U(35J1 L2(352) L3(353) L4(354) 15(3551 RANNEY TW-1 (tw-28) TW-20 TW-21 (307) TW-22 TW-23 TW-24 TW-25 TW-26 TW-27 TW-3 Qw-3) TW-32 TW.33 TW-38 TW-39 TW-40 TW-41 TW-46 TW-48 TW-S TW-60 TW-61 TW-E4 TW-E5 TW-E6 TW.M1 Surface Elevation Jfeet) 629.39 598.76 629.29 630.82 625.87 627.14 632.91 634.36 634.37 633.49 630.69 634,26 628.04 589.75 633.93 634.92 634,2 623.24 624.78 632 630.21 630.35 632.49 631,4 632,69 638.23 632.89 635.82 628.5 594.48 630.63 635.27 635.23 632.87 635.09 636.02 631.16 635.22 631.61 Total Depth (feet) 71 42 71 7S 70 70 95 96 91 93.9 90 96 92 Well Diameter (Inches) 2 2 2 2 2 2 18 18 18 18 18 18 18 Slot Size (inches) 18 18 18 18 92 NA 95.21 -6 6 6 10J.4 6 162.69 6 J08.23 6 6 6 98.5 6 6 6 /M.27 6 6 6 6 6 101.16 4 6 101.61 4 Screen Length (fBBt} 10 10 10 S 5 10 20 20 20 19 13 20 26 NA 18 1 29 29 29 M 29 M W . 29 M Elevation of Screen Interval (feet) 566,0. 5S6.0 567.0-557.0 567.0-5S7.0 559.0-554,0 560.0-555,0 565.0.555.0 558.7-538.7 553.8-533.8 S53.5. 533.5 SS5.7-536.7 556.0-543.0 S5S.O-S35.0 555.0-535.0 S42.0-541.0 S55-5S5 550-539 550 539 550-5)9 SSO-S39 550 -539 , SSe-W S50-5S9 SSO-S39 Pagel of 2 JTS0015059 EID620794 Table 2.0 Monitoring Well Construction Data DuPont Washington Works Main Plant Washington, WV Monitoring Wells New ID Old ID I07-MWOI K14.MW01 D08-MWOI P06.MW01 U03-MW01 U05-MW02 U05-MW01 L04-MW01 AA04-MW01 AA05-MWOI AB07.MW02 AC07-MWQ2 AE11-MW01 AI06-MW01 E13-MW01 G17-MW01 L06-MW01 M04-MW02 M04-MW03 N04-MW02 N05-MW01 P04-MW02 P05-MW02 R04-MW02 S05-MW02 U04.MW01 V06-MW01 WOS-MW01 Y14-MW01 Z06-MW02 Z07-MWOI Z09-MW01 TW.M2 TW.M3 TW.M4 TW.M5 TW-M6 TW-N2 TW-P12 TW-W1 WOO-577 TW-70 TW-71 TW-72 TW-73 TW-74 TW-75 TW-76 TW-77 TW.78 TW-79 TW-80 TW.81 TW-82 TW-83 TW-84 TW-85 TW.86 TW.87 TW.88 TW.89 TW.90 TW.91 TW.92 TW.93 Surface Elevation (feetL 610.23 627,34 600.67 601.14 592.44 631.17 632.11 Total Depth (feet) 97.34 63.S 102.11 Well Diameter [inches) 4 4 4 4 6 6 6 Slot Size (Inches) Screen Length JLfeet) 29 39 M 597.4 43 2 630.8 70 2 630.6 72 2 633.2 74 2 629.51 72 2 634.04 72 2 623.5 74 2 630.5 80 2 629.85 77 2 593.5 25 2 593.6 26 2 593.6 26 2 633.48 82 2 590,6 28 2 631.68 80 1 593.2 28 2 631.18 78 2 593.) 27 2 629.93 77 2 630.25 76 2 629.93 90 2 640.1 72 2 629.64 74 2 630.7 70 2 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 Elevation of Screen Interval (teet) 556-S30 556-536 SSV-539 564.4-554.4 570.8-560.8 568.6-558.6 569.2-559.2 567.51-557.1 572.04-562.04 559.5-549.5 560.5-550.5 562.85-552.85 578.5-568.5 577.6-567.6 577.6-567.6 561.48-551.48 572.6-562.6 561.68-551.68 575.2-565.2 563.18-553.18 576.1-566.1 562.93 . 552.93 564.25-554.25 549.93.539.93 578.1 - 568.1 565.64.555.64 570.7 - 560.7 M16-MWOI N13-MW01 P08-MW01 Q04-MW02 TW-55 TW-54 TW-53 TW-50 627.14 625.87 629.29 598.76 Red and Italics ~ approximate Bold - Taken froin RFI WP information taken off cross-section Page 2 of 2 JS0015060 EID620795 Table 2.1 A Summary of Analytical Results: C-8 in Surface Water Samples DuPont Washington Works Main Plant Washington, WV ^>,. 5' . .Sample .;';' ::' OUTFALL 002 OUTFALLOOS RIVER BELOW 005 RIVER BELOW PAGES RUN oate 10/25ffl1 9/19/01 7/11/01 6/14/01 6/31/01 4/11/01 3/21/01 2/14/01 10/25/01 9/1B/01 8/30/01 7/11/01 6/14/01 5/31/01 4/11/01 3/21/01 ahwri 6/14/01 ;..., : , .ie-8(ugffl.'. 2.8 o.na 0.558 0.594 0.436 1.5 8.54 1.74 66,7 2.86 2.16 1ZO 7.4 1.43 4.31 199 153 0.034 J 0.075 J ;-!s.!:...'S J = estimated value (below laboratory quantitation limit) JS0015061 EID620796 Table 2.1 B Summary of Analytical Results: C-8 in Groundwater DuPont Washington Works Main Plant Washington, WV ^'.a"', SannNff;;:: AA04-MW01 AAOS-MW01 AB07-MW02 ACOT.MW02 AE11-MW01 A106.MW01 AM07-PW01 A008-PW01 AQ09-PW01 E13-MW01 F06-MW01 G17.MW01 K16.PW01 L04-PW01 Lowwyoi L17.PW01 ':: ' ' ,- :. Oa^ " 2/B99 11/12/98 11/12/98 (dup) 2/4/99 11/11/68 2/4/99 11/18/96 2/4/99 11/16/98 '" 2/2/99 11/10/98 2/3/99 11/16/98 11/20/00 8/16/00 5(12/99 " ^ r 11/18/98 " S1B/98 6/2/97 4/2/96 11/20/00 IIBO/OO (dup) 8/15/00 S12/8S 6/16W S/2W 4/2/96 10/11/01 ----"--5il2re9~"'"" 5/12/99 2C/99 11/11/98 2/2/99 11/11/88 5/12/99 2/2/89 11/11/98 11/20/00 2/OT8 11/W98 7/11/01 4/11/01 11/20/00 mm 11/W9 11/18/98 WUBS 21W/9 11/13/98 7/11/01 4/11/01 W14/00 6/3/99 2/9/99 11/18/98 60/98 5/29/97 4/11/96 2/16/94 C.8(ugm 5.43 <0.1 0.42 1.46 0.77 0,835 <0.2T 0,356 0.79 0.69 L 0.41 0,138 <0.1 0.24 0.071 J 0.578 0.082 B 1.9 L 0.4 0.79 Q.4B 0.4 0.26 0.167 0.307 1 0,55 0.52 0.498 1,46 0.882 0.59 L 2 0.35 L 0.1 2.47 2.11 L 13 7.5 16.2 6,481 0.202 3.99 13.8 5.89 7.9J 3.9 J 4,81 870 2.31 1.58 0.819 1.63 2.76 0.33 16 7.9 3.7 2 JS0015062 EID620797 Table 2.1 B Summary of Analytical Rasults (con't): C-8 in Qroundwatar DuPont Washington Works Main Plant, Washington, WV ^^-W^'SwwtSS^^-'^ M04-MW02 M04-MW03 M16-MW01 N04-MW02 N06-MW01 MW-AJP MW-MQM MW-WW MWBG M^VMOt P04-MW02 PQ5-MW02 POfrMWOZ POB-MW01 Q04-MW02 Q05-MW01 R04-MW02 V05-PW01 T13-MW01 U04-MW01 U16-MW01 S06.MW02 V08-MW01 WOS^VIWOI Y14-MW01 Z06-MW02 Z07-MW01 Z09-MW01 .'' "^J'Dafa .;;'..."' 2/7/99 11/12/98 2/7/89 11/12/88 2/3/99 11/10/98 1/25(01 1/25/01 (dup) 2/7/89 11/12/98 2/5/99 11/13/9B 4/18/86 . 4/18/96 4J18/96 40/66 2/2/99 11/11/98 1/25/01 2/6/99 11/12/98 2/6/99 11/13/98 2/S89 11/13/89 2/4/89 11/13/98 2/4/99 11/13/98 11/13/98 1/2S/01 2/6/99 11/12/98 7/11/01 4/11/01 n/20/do ~ 2/7/99 2/7/99 (dup) 11/1B/9B 2/3/99 Z/3/99 (duo) 11/17/98 2/6/98 11/12/89 S11/00 S/20/99 . 6/19/98 215199 11/13/8B 2/4/99 11/16/98 2/6/99 11/17/98 .aa9& 11/10/98 2/4/99 11/16/98 2/4/&9 11/16/98 2/6/99 11/17/98 G-fSwaSI 17 0,2 21.1 <0.1 3.66 L 0.88 688 690 329 380 815 13 <0.4 0.69 0.85 <0.1 28.6 L -0.1 12600 13600 8300 434 1200 414 31 43.4 36 9S4 660 38 13800 9420 1300 11.4 6,46 " - 13.7 12.4 3.96 0.66 L 0;6<L 1,30 L <0.1R 4.2 1.6 4.7 2 11 174 690 1.91 1.7 0,729 0.31 4.96 L 12 O.B03 4.5 2.05 3.8 2.74 <0.1R ...: .:;: JS0015063 EID620798 Table 2.1 B Summary of Analytical Results (con't): C-8 in Groundwater DuPont Washington Works Main Plant, Washington, WV "::%.. ^L ' s^SSmplB";'. '::... ' ^ RBIMW1 RBLMW2 ' RBLMW3 RBLMW4 RBLMW6 RBLMW6 RBLMW7 RH.MW8 RBLWW9 RBLMW10 RBLMW11 RBIMW12 B6MW2 B6MW3 BQVMB ADPMW1 ADFWW2 ADPMW3 ""':.;;';." 12/5/91 12/5/81 (duD) 12/11/91 12/11(91 (dup) 12/11/91 12/5/91 12(10/91 11(21/91 11/21/81 11/21/91 (dup) 12/10/81 12/10/91 11/20/81 11/20/81 12(10/91 12/13(91 12/13/B1 12/13(91 (dup) 12(11/81 12/6/91 12/6/91 12/6/91 R " unusable data result (relative to QA/QC) J ' Mlimated value (below laboratory quantification llmil) L s possible tow bias rteult (ralauve to QA/QC) B= compound detectwi to QC blank < E Non-dotect at stated laboratory method detection limit V . C-8<UBffl 140 . . . . 140 65 er 7100 550 1300 3300 48 2 2.4 3,4 14 47 4,6 2.3 4 3.6 5,6 7800 25 20000 JS0015064 EID620799 Table 2.1 C Summary of C-8 Analytical Results: Drinkingn'ap Water Samples DuPont Washington Works Main Plant Washington, WV ^ ::%;.aasssarittii!'.a?;^':BLDG 1 MAIN BLDG231 BLDS293 BLDSS ' !v- Wt -:;;:,i"? ...:. 10/1 V01 10/11/01 (AIR) ffl16/00 . . 1OTV01 6/12/99 aia89(dup) 10/11/01 812^9 5/12/99 . owwrn. '. ., 0.507 Q.m 0.5B9 0.46 O.SOB 0.2B9 0.423 0.496 0.213 JS0015065 EID620800 Main Plant and Landfills Local Landfill 3.0 LOCAL LANDFILL EflviTOwicntal Si Wme Quality...SiteConteptaalli Dat0ap..-....-- q ^ ,.,,......,,.,,,,........................ 3-2 .--,,...,,.... ..,,,,.,,.... . M Table 3.0 Tabb3.1A Tablei.lB Fi6mc3.0 PipnB3.1 Rgwe 3.2 HgineSJ Fipie 3.4A npni3.4B Figine 3.5A Rpe3.5B REUIT 3,5C PigiBc3.5D Fipae3.5E ngte3^P Rgiae3.50 HgiMt 3.(A Figure 3 ,SB Figuns3.6C Figare3.6D TableE Local Landfill Monitoring Well Construction DaQ Local Landfill Analytical Data Tatte - Surface Wattr Local Landfill Analytical Date Tables - GnMidwater Loca] Lanilfill Locaiion Mlip FIgmil Local lAidfillaad WashingloiiWoAB Main Plant 1-mile RAdiiir, Map Lixal Landfill Mwiitoring Weil mil Surface Water Sample Locallon Msf Lncal Landfill Creat Seetkm Loeifion Mp Local Lundfill Crw SeetiDB A-A* Loeal LBndfill Cross Section B-B1 Local Landfill GnmiidwaiEr Elevation Map - November 2001 Local Landfill Gwiitlwata'BteyitltaMtp-Deeanbia' 2000 Local Landfill Groiuidwati-r Elevition Map - November 1999 LacatLaniifillORluadwatcrElCTilionMtp-NovCTibB-lWS Local Laiutfill GrauadwatB'Btevilim Mip - Nimmber 1997 Local LaDdnilOnmndwaifrElwtiOBN.ip-DiKiiaibisf 1996 Local Landfill GiTMBdwiiter Elevation Mip-DawAcr 1994 Local Landfill &8 Ceneeiiiiailtti - May 2001 Local Landfill C-8 Concentration - Miy 2000 Locil LaodfiU C.8 CBnEntltiBB May 1999 Lotal LaBdflll C-8 CDncHitnition-May 1998 ComplattonofNstoiry<!ataDralt2rBv,cloe Mar. 11,02 Wllmlngton, D6 3-1 JS0015066 EID620801 Main Plant and Landfills Landfill ____________________Local 3.1 Introduction The Local Landfill is located immediately adjacent to the main plant off the southern perimeter (Figure 3.0). The landfill and plant are located along the Ohio River in Washington, West Virginia, approximately seven miles southwest ofParkersburg, West Virginia. A water use and well survey is currently being conducted for die area within a l.mile radius of the landfill perimeter (Figure 3.1), The Local Landfill consists of three separate closed cells located on the heavily wooded 250-acre site. The cells were operated from 1964 to the middle 1980s under West Virginia/National Pollutant Discharge Elimination System (WVNPDBS) Permit No. 0076538. The permit is currently undergoing renewal and is expectedto be effective in January 2002. The permit requires monthly surface water samplingand semi-annual groundwater monitoring. Materials landfllled included scrap product, scrap metal, wood pallets and bins, and Powerhouse ash. Approximately 144 tons of waste per year were disposed in the landfill. Powerhouse ash comprised about 70 percent of the total waste. The specific source ofC- 8 in historical groundwater and surface water samples collected from on-site locations has not yet been determined. The cells were closed and covered with approximately two feet of low permeability soil. Figure 3.2 shows the location of the three cells, monitoring wells, and surface water sampling points. The cells have no compacted or syntheticbottom liners. However, a hydrogeologic evaluation indicated that the natural soil present under the cell materials is composed of reddish brown clay and weathered shale having a very low hydraulic conductivity of about 5 X 10"7cm/sec (DuPoiW, 1990) and ranges from 3.5 to 19.5 feet in thickness. 3.2 environmental Setting 3.2.1 Geology The Local Landfill is situated in a hilly area with relief of approximately 30 to 40 feet. The slopes appear to be a combination of natural topography with terraced outcrops of massive sandstone and siltstone underlying varying amounts of soil cover and man-made landfill plateaus. The locations of two cross-sections developed for the Local Landfill are shown in Figure 3.3. The two cross-sections, A-A' and B-B', are shown in Figures 3.4A and 3.4B, respectively. A shallow tight clay layer starting at ground surface ranges from three to 25 feet thick. The clay contains some minor sandy and silly zones, and some pebbles and fragments of sandstone in some locations. The clays are of low plasticity and appear to be well compacted, often displayinga laminar structure (DuPont, 1990). Underlying the shallow clay layer is weathered shale ranging from 10 to 35 feet thick. Below this competent bedrock is present at depths ranging from 21 to 40 feet below ground surface. Compilation af htetay data Draft Zrev.doc Mar. 11,02 3-2 Wllmlngton, 06 JS0015067 EID620802 Main Plant and LanflffilS Landfill __________^________._______LpCal The bedrock at the Local Landfill consists ofinter-bedded red and varicolored sandy or calcareous shale, and gray, green, and brown sandstone of the Permian age Dunkard Group, The Dniaxinnan thickness of the Dunkard Group in this region is 570 feet. The cross-sections show mat the sandstone layers dip gently towards the north. Most of the sandstone layers located in the upper portion of Ac stratigraphic section are lenticular and laterally discontinuous. Two laterally continuous sandstone layers are located in the lower stratigraphic section. 3.2.2 Hydrology, Hydregeology and Groundwater Flow Hydrology Ini general, infiltration of precipitation is limited due to the very low hydraulic conductivity (5 x 10"7cm/sec) of the surfidal clays (where these clays exist) and the weathered bedrock (DuPont, 1992), In addition, infiltration of precipitation into the cells is limited by approximately 2-feet of low permeability soil and vegetative cover capping of the cells. Leachate from the southern cell and the eastern cell flows from the seeps in the steep valley walls to leachate collection ponds. Pond 1,2 and 3 (Figure 3,2). Leachate from these ponds is discharged into a pipeline and conveyed to the main plant where it passes through stonn water Outfall no. 001 into the Ohio River, Monitoring of combined pond effluent conveyed in the pipeline is conducted at Outlet 101. Hydrogeology Groundwater underlying the Local Landfill occurs in two zones. The discontinuous upper 2oae consists of the clays and underlying weathered bedrock and has a very low hydraulic conductivity (DuPont, 1992). The lower zone consists of the continuous and discontinuous sandstone layers having low permeability of 1 K 10'5 cm/sec. The sandstone layers are separated by laterally continuous shale layers. Well yields from the sandstone layers are very low, ranging fixan <0.5 gpm to 1.5 gprn (DuPont, 1992). The upper (and thicker) of the two laterally continuous sandstone layers located in the lower zone at elevations between 710-740 feet above Mean Sea Level (Figures 3.4A and 3.4B) has been designatedas the "underlying significant aquifer" and is currently monitored semiannually as required by the pennit. In 1989, eight monitoring wells were installed at the Local Landfill by Tetra Tech Richardson (LLMW-1 through 8). However, five of these monitor wells (LLMW-1, -2, - 3, -5, and -7) were closed in 1996 because they were screened in the discontinuous shallow clays and Underlying weathered bedrock. LLMW-8, a bedrock well, was closed in 1997 because it was dry. Two additional bedrock wells, LLMW-9 and -10 were installed in 1995 and 1997, respectively. LLMW-9 was installed as a background well, These wells are screened within the significant underlying aquifer. Table 3.0 summarizes the well construction data for the existing monitoring wells. Groundwater Flow Oroundwater elevations have been measured semiannually since 1994. Groundwater elevation contour maps for die significant underlying aquifer have been prepared from this date as required by the WVNPDES Pennit No. 0076538, Figures 3.5A through 3.50 present maps for 2001 through 1996 and 1994. The groundwater contours were Compilation o( historydata Draft 2rev.doc Mar. 11,02 3-3 Wllmlngton, DE JS0015068 EID620803 Main Plant and Landfill Landfills_______________________________LpCal transferred from the original maps submitted for the permit to the updatedLocal Landfill base map. Evaluation of limited groundwater elevation data for the closed wells (based on well installation information) indicates a downward vertical gradient between the upper discontinuous water bearing zone and the lower sandstone layers containing the underlying significant aquifer. In addition, C-8 present in the underlying significant aquifer provides Anther support for a downward vertical gradient. The groundwater contour maps for the underlying significant aquifer show that flow is from the south to the north towards the plant. The sandstones of the underlying significant aquifer outcrop in the valley walls where discharge may occur as seeps. However, groundwater may also flow downstopewithin the fractured rocks of the valley walls and ultimately enter the alluvial terrace deposit on the main plant Groundwater discharging to seeps ultimately migrates to the plant through a number of pathways. It can discharge downward to leachate collection ponds and pipes to the main plant where it enters stonn sewers and discharges to the Ohio River. Groundwater also can seep to small screams draining the property to the north and flowing to me Quaternary alluvial terrace unconfmed aquifer where pumping ofon-site active well fields controls groundwater flow. Groundwater flow in the alluvial aquifer, adjacent to me valley walls of the Local Landfill, is towards the pumping wells located near and parallel to the Ohio River. The pumping of these well fields also lowers the groundwater level to below river stage, inducing surface water from the river to flow into the alluvium towards the pumping wells. Water from the pumping wells is used for non-contact cooling purposes and ultimately is discharged to the Ohio River. 3.3 Water Quality 3.3.1 Surface Water Quality Table 3.1 A presents the historical C-8 concentration data available for surface water. Figure 3.2 shows the surface water sampling locations, if me location currently exists. Samples from two outfalls, four outlets, two streams, and one leachate sampling location have been collected periodically since 1994. C-8 concentrations in the outfalls and outlets range from <0.2 ug/1to 80 ug/1. Stream sample C.8 concentrations ranged fi-oin 4.12 ug/1to 15 ug/1. The leachate sample, collected in the pipe from me leachate ponds, . had a concentration of 31 ug/1 (February 1994). For sample locations having more than two sampling events, the concentration of C-8 is decreasing with time although it is difficult to accurately identify trends in samples with the limited data set The C-8 concentration at Outlet 101, located at the northeastern portion oflhe side, have decreased from 54 ug/1 to 12 ug/1over the course of three sampling events. 3.3.2 Groundwater Quality Analysis of C-8 in groundwater has been conducted annually on a voluntary basis since 1996. Table 3.1B presents the data available for C-8 in Local Landfill monitoring wells, Groundwater was sampled annually in 1996, and 1998 through 2001 for three wells, LLMW-4, .6, and -9- LLMW-10 was sampled twice in 1998 and 1999. The limited Complalto) of history data Draft Zrev.doc Mar. 11,02 3-4 WllfflinBton. DE JS001506& EID620804 Mate Plant and landflllB________________________________ Local Landfill amount of data makes it difficult to develop concentration contour maps. In addition, the monitoring wells are located at three separate areas (cells) of the landfill; therefore, annual data for the past four years is posted in Figures 3.6A through 3.6D but is not contoured. C-8 concentrations in LLMW-9 and -10 range from non-detectable to 0.22 ug/L The other two wells, LLMW-4 and -6, have the highestconcentrations, ranging from 1.4 to 39 ug/1and from 1.32 to 15 ug/1respectively. Although there is limited data, the data shows a distinct reduction in C-8 concentration over time for wells LLMW-4, -6, and -9. 3.4 Site Conceptual Model The Local Landfill site conceptual model describes the potential exposure routes for current and future human and ecological receptors. Potential exposure routes were evaluated and classified as complete or incomplete. Access to the Local Landfill is restricted by electronic and locked gates at Hie road entrances. However, a posted nature trail has been established on the east side of the landfill property. The trail loops around the eastern part of Ac landfill starting and ending near tile landfill's electrically operated gate. The nature trail is a marked trail and does not cross the cells. Access to the site from surrounding roads is possible but is discouraged due to the heavily wooded nature of the property and the hilly terrain. The three cells at the Local Landfill are covered with. a low permeability soil and vegetative cover. This cover prevents human and ecological receptors' exposure to the landiBlled materials and to the soils potentially impacted by the landfill materials. However, these materials could potentially be exposed by extensive digging or rooting in the soil by animals or unauthorized people. Therefore this pathway is considered to be potentially complete but naioimal. An additional potentially complete exposure pathway exists if the soil and vegetative cap is eroded by precipitation. Permit WV0076538 requires mat the landfill surface will be inspected quarterly for evidence of cracking or erosion (which could allow surface water to enter the solid waste deposit)and evidence of settling of solid waste (causing ponding of surface water). Per Condition G-l 6 of the permit, a stonnwater erosion inspection is conducted annually. Therefore, this potentially complete pathway is considered to be minimal. At the landfill, precipitation is expected to take one of two paths. It may infiltrate downward through the vegetated soil cover and into the cells. However, the low permeability of the soil cover reduces the amount of infiltration. If the precipitation infiltrates the soil cover, it will possibly encounter the landfill materials and will continue downwards. It may be prevented from further downward migration by the low permeability clays and weathered bedrock. However, if this water migrated further downward, it should encounter the sandstones and shale layers. Groundwater flowing through the sandstone layers mat outcrop in the valley walls located above die plant site's southern edge would be exposed at the surface in seeps, if seeps exist. The existence and location of seeps at some places on the property have been observed, particularly those mentioned near the leachate collection ponds. Much of the site remains unexplored, n. CampBatton of hiatotydirts Draft Zrev-doc Mar. 02 3-5 Wtmlngton, DE JS0015070 EID620805 Main Plant an Landfill dLandflls_______________________________________Local therefore, complete evaluation of this potential exposure pathway (surface water to groundwater to surface water) is currently not available. Another possible migration route for precipitation is direct flow as surface water via overland flow downslope. m this case the water would not encounter the fill materials at any point it time. This potential exposure pathway is considered incomplete. Contact with groundwater impacted by C-8 is another potential exposure route for current and future human and ecological receptors. However, contact with groundwater under the landfill is limited, although, contact with leachate that has reached the ground surface via seeps is possiblein the vicinity of Pond 1, near the southern most cell. Ponds are open and accessible to limited number ofDuPont employees. As stated previously, groundwater flowing through the sandstone layers that outcrop in the valley walls located above the plant site's southern edge would be a possible contact location. However, because seeps in this area are not evident, it is likely that groundwater flows downslope within the fractured rocks of the valley walls and discharges to the main plant alluvial terrace. Determining the existence and location of seeps on Hie property has not been completed therefore, this potential exposure pathway cannot be fully evaluated. 3.5 Data Gaps The following data gaps were identified for the Local Landfill: 0 Identify flue locations of seeps in the valley walls and determine water quality with respect to C-8 concentration. Q Determine the C-8 concentration in streams and other surface water bodies. 0 Acquire additional geological data to refine the Site Conceptual Model. Q Install additional monitoring wells to provide additional groundwater flow data and groundwater quality data. 0 Gather additional C-8 concentration data ftom monitoring wells for plume delineation. Activities to fill the date gaps will be proposed and discussed in the work plan. 3.6 References DtlPonfc 1990. Washington Works 1990 Preliminary Hydrogeohgic Assessment. Solid Waste &. Geological Engineering Department. ___. 1992. Verification Investigation E.L DuPontdeNemours Co. Washington Works April 1992. (Vol. 1). Compilation ofhtetoty data Draft 2rev.(toc Mar, 11,02 Wiliiiinglon, DE S-6 JS0015071 EID620806 Table 3.0 Monitoring Well Construction Data Local Landfill Washington. WV Monitoring Wells LLMW- 4 LLMW- 6 ULMW- 9 U.MW- 10 Surface Elevation (feet) 844,7 793.2 7B8.54 ; 805.94 Total Depth ffet} 155 SO 80 87 Well Diameter (inches) 4 4 4 4 Slot Size (inches) 0.020 0.020 0.020 0.020 Screen Length (feet) 20 20 20 20 Elevation of Screen Interval (fCBtl 717.2-697.2 723.2-7032 728.54-708.54 738.94-718.94 Table 3.1A Summary of Analytical Results: C-8 In Surface Water Samples Local Landfill Washington, WV ^^^s-^sssicSs:^. .T^LEACMATE OUTFALL 004 OUTFALL 005 OUTLET 001 OUTLET 002 OUTLET 003 OUTLET 101 STREAM 1 ~- ':;!:" ^iBirte.:..!"" 2/1S1984 9/27;2000 12/10/1993 sa/ia e/aiaaa 5/29?19By 4/ai996 2/16/1984 6/27(2000 12/10/1999 6/3/19B9 6/2/1998 S/2B/1SB7 4/189e 2/16/1994 6/28M997 4/2/1896 S/29/19B7 4/2/1B96 6/29/1997 4R/igae 9/14/2000 6/3/1899 60/1898 6/29/1997 4/2/1896 12/2B/1999 6/2/189B 4/2/1698 :'1',.. , c-S(ue/n 31 4J3 7.1 3.06 12 13 13 11 13.3 34 6,8 39 41 39 35 60 61 COS 72 23 20 12 15 54 11 72 4.12 10.7 15 14 ^^yy;:. JS0015073 EID620808 Table 3.1 B Summary of Analytical Results: C-8 In Groundwater Local Landfill Washington, WV ^'Wssi ^'W&s LLMW.4 LLMW-6 LLMW-9 U-MW-10 'W.'.."": '""s'IiMsBMi,ai ..-- "SW^ ' ".^'.O-S1-.f4tiMC'X.:^ sfnaooo 10 5M9/1889 16.2 5B7/188S 26 4|[11/1S96 39 shsissstft 3 5f1flttfl00 1.42 S/19;1S99 1,32 5f27/18@8 9 wwm S16Q001 15 0.039,1 snoaooo <0.029 S2WiBB9 0.046 J W27/1998 <0.1 4ni;19B6 0.14 5f20/1688 0.1S 613SIWW 0.22 JS0015074 EID620809 Main Plant and LandHlte Letart Landfill 4.0 LETART LANDFILL Introduction--.......<.,. .,,,,..,,-- Bnvnoflincntal Setting......... Wtta QiaU^-.TM--............. Sin; Conceptual Model..TM... DHa Qsys...-...,,..--...--.... RfilBCn[X9,.......--.-.----........ Ttlle 4,0 Tbl*.lA Tible 4. )B Tables Letillt LimdflM Manitoring Welll Conlnititl Dtta LaaBLandfill Analyticti Dttt.TaMss - Sutface Wtltr UUrt Umifill Anttytietl Dl!a TtMis - Gtouriwiitet riSurc4.0 Fi(,Wt4.1 Figmt 4^ Figure 43 Figure 4.4A Figure 4,4B figalt 1.5A Fliiro 4.5B Figun;4.5C Beuni 4jD Tffsc ^se. RgBe 4.5F BgllB 4.6A Figure 4.(B Fipire 4.6C riguie4.6D Figures Letstt UBilfill Location Map Lctart Landfill 1-mile Rtdiui Map lttrt Laidflll Monitoring Well and Surface Wattr Sample Location Map I^rtLiindfiBCitiS Section LoealionMsp Letart Laisdfill Cro8 SKtion A-A* Letart LtBdfill Cross Sectiirn B-B" UtiBt Ufldfill F.Zone GroundwtlBt Eicratioii Map - NovenbBr 2001 Lett UBdfliI F-Zone GnilMidwiuer Elevation Map - January 2001 Letart Landfill F-Zone Croundwaier BtivBtion M(>- Oetober 1999 LffiBt Liuidfill p-Zoiw Oroundwater Eteraiion Mp - Oiltoher 199B LetiBt Unitfll F-ZonB OrounnivaW BIewaon Map - Decnnbar 1994 Letart Undfiil F.Znae GtoundwatCT Elevttlloil Map - Dtiitinba-1992 UBBt C-8 COncCTIiHnn Map - July 2001 Letart C-8 CoaetftiiHioiiMp-Jimmy 2BOO Letart C-8 Coneeolnifion Mip - July 1999 LctiirtC-8 Coaccailration Mip Novtmber 1991 ...... 4-2 ..M.,.4.2 ,...-.+4 .......4-6 ,..-,..4.7 ........ 4-8 Compilation of histoly data Drall 2rev.doc Mar. 11,02 Wllmlnglan. DE 4-1 JS0015075 EID620810 Main Plant and Landfills __ Letart Landfill 4.1 Introduction The Letart Landfill is located just north of the town ofLetart in Mason County, West Virginia (Figure 4,0), A water use and well survey is being completed for the area within a 1-mile radius from the landfill perimeter (Figure 4.1). The landfill covers approximately 17-acres of a 205-aere parcel of land owned by DuPont Washington Works. It was in operation from the early 1960s to 1995. The landfill was operatedand closed under West Virginia Solid Waste /National Pollutant Discharge Elimination System Permit No. WV 0076066. This permit requires quarterly groundwater monitoring, outfall and surface water monitoring and engineered cap maintenance. Figure 4.2 shows the landfill extent, orientation, topography, and monitoring well locations. The landfill was constructed within a natural ravine and has no compacted or synthetic bottom liners. However, a hydrogeologic evaluation indicated that the natural soil present under the landfill material is composed of highly plastic clay and silt having a permeability of about 10"7cm/sec (DuPont, 1993). The soil thickness ranges from 4 to 14 feet, averaging about 8 feet in thickness. Letart Landfill received waste was from the Fluoropolymer manufacturing process at the plant mat consisted primarily of scrap product, scrap metal, wood pallets and bins, and miscellaneous trash. Approximately 5,000,000 pounds of waste per year were disposed in the landfill. This waste is believed to be the source of C-8 in me historical groundwater and surface water samples collected from on-site locations. The Letart Landfill was permanently closed by installing an engineered multi-layer geosynthetic and soil cap (DuPont, 2001). Included in the closure activities were me installation of a leachate collection system, erosion and drainage control measured and chain-liak fencing. The cap construction was completed in April 2001. 4.2 Environmental Setting 4.2.1 Geology The Letart Landfill is situated on a heavily dissected plateau consisting of several steep V-shaped valleys. 8-esidual soil covers roost landfill areas. In general, the soil at the site has been described as residual in nature, consisting primarily of heavy clays derived from me weathering of bedrock. At most landfill areas, the soil is less than ten feet thick, with a maximum thickness of 20.5 feet The underlying bedrock at the Letart Landfill consists ofinter-bedded red and varicolored sandyor calcareous shale, and gray, green, and brown sandstone of me Permian age Dunkard Group. The maximum thickness of the Dunkard Group in this region is 570 feet. The location of two cross-sections, A-A' and B-B', crossingthe landfill are shown in Figure 4.3. The two cross-sections of the underlying geology are shown on Figures 4.4Aand4.4B. Compteton of Nstory data Draft Srw.ttoc Mar. 11102 4-2 WllmlnBton, D6 JS0015076 EID620811 Main plant and Landfills__________________ _______Letart Landfill Geologic investigations conducted at the Letart Landfill identified six stratigraphic waterbearing zones that were designated as Zone A through Zone F, with Zone A being the shallowest zone and Zone P the deepest. These zones consist of massive, very fine to fine grained crystalline sandstone with occasional shale lenses. Zones A through F are separated by locally continuous shale units that are generally ten feet or greater in thickness. Zones A through D/E are discontinuous. Zone F is the first laterally continuous zone under the landfill. Zones A, C, D/E and F outcrop on the valley sides and along the Ohio River near the southern end of the landfill. 4.2.2 Hydrology, Hydrogeology and Groundwater Flow Hydrology The Letart Landfill engineeredcap system prevents surface water from contacting landfilled materials. Precipitation falling on me engineered cap system takes one of two paths. It may infiltrate downward through the vegetated soil and encounter the impermeable geomembrane and then flow laterally downslope on top of the geomembrane. Alternatively, precipitation may flow via overland flow on top of the vegetative layer downslope. In either situation, this surface water does not contact the landfuled materials and migrates downslope towards drainage ditches constructed In or adjacent to the cap system. Precipitation falling on the northwest side of the upper part of the cap flows downslope towards the southwest, away from the landfill, into a drainage ditch that flows to a sediment trap near LMW-6. Precipitation falling on the remaining portions of the cap flow downslope and towards the south in drainage ditches. Hydrogeology Hydraulic conductivity testing [i.e., slug tests (Zone A) and borehole packer tests (Zones C, D/E and F)] of the bedrock zones indicates mat these zones display low hydiwlic conductivity (Tetra. Tech Richardson, 1990). Zone A hydraulic conductivity is low, ranging from 10"4cm/sec to less than 10'5 cm/sec. (There are no wells monitoring Zone B, therefore, it was not tested.) Zones C and F have very low hydraulic conductivities ranging from 10"*cm/see to less than 10'8 cm/sec. Zone D/E hydraulic conductivities are also very low and range from lO'5 cm/sec to 10"8cm/see. Zone P has been designatedthe "underlying significant aquifer" as defined by to the West Virginia Solid Waste Management Regulations because it is laterally continuous under the landfill and is thought to be hydraulically connected to the Ohio River south of the landfill. Most current groundwater monitoring is conducted in Zone P, The low hydraulic conductivity can be attributed to the very fine-grained nature of the water-bearing units. In addition, many sandstone units in the region typically display effective porosity as low as 1 percent. This low porosity results from pore space being filled in by authigenic minerals (e.g. kaolinite) sometime after original sediment deposition. Zone F groundwater average linear velocities were calculated for flow from the north to the southwest and from the north to the southeast (DuPont, 2000). These values are relatively low, 0.01 and 0.003 ft/day respectively. The low velocities calculated in me F zone indicate that groundwater flow beneath the landfill is very slow, attributable to me Compilationof Wstotydate Draft 2rev.<toe Mar, 11,02 4-3 Wllmlngton, DE -. . . . . . . ... JS0015077 EID620812 Main Rant and Landfills __________________LetgrtJLandflll low hydraulic conductivity present in the P zone and all the overlying units as well. Low vertical hydraulic conductivities in the overlying shallow zones limit infiltration and recharge down to the F zone. The saturated thickness of Zone F ranges from 22 feet in the upgradient well (LMW-2A) to between 2 and 8 feet in five downgradient wells (LMW-5A, -6, -9, -10, and -11). la many instances, the monitoring wells at the landfill cannot be sampled until 48 hours (or longer) after purging, when a sufficient quantity ofgroundwater has recovered in the well screen interval. Groundwater Flow Thirteen monitoring wells have been installed at the Letart Landfill in the Zone A, C, D/E, and F sandstone units (Tetra Tech Richardson, 1989; 1990). Two of these wells, LMW-10 and LMW-11, were installed in October 2001 to provide additional data from Zone P to the north and south of the landfill. Table 4.0 lists the wells monitoring each zone and provides well construction information. Water level measurements and calculated groundwater elevations have been measured quarterly. Figures 4.5A through 4.5F provide available annual groundwater elevation contour maps for Zone F as required for the permit. This data was transferred from the original maps submitted for me permit to the updated Letart Landfill base map. The location and limited number of monitoring wells within Zones A, C and D/E prevents determination ofgroundwater flow directions within these zones. However, elevations measured in the monitoring wells indicate a downward vertical gradient within the site groundwater system. Within Zone F, a groundwater divide exists under the center of the landfill in a north-south direction. Groundwater east of the divide flows southeast towards the Ohio River. Groundwater west of the divide flows towards the west and southwest. Groundwater elevation data, including me newly installed LMW"! 1, the most northern monitoring well, indicates a slight component of northward groundwater flow in Zone F in this area. Rapid decreases to the observed volume of water discharging from me leachate collection system in 2001 indicate that groundwater flow under me landfill is being greatly reduced m response to the installation of the engineered cap system, to addition, this reduction indicates that a new equilibrium state for groundwater flow has not yet been reached. Continued monitoring ofgroundwater elevations of Zones A through F is required to evaluate long-term changes in groundwater flow resulting from closure activities, 4.3 Water Quality 4.3.1 Surface Water Quality Voluntary surface water sampling for 08 has been performed periodically since 1991. This data is presented in Table 4.1A. The two locations sampled most frequently, the Upper and Lower ponds, no longer exist. During construction of the engineered cap system, these ponds were de-watered and the sediments underlyingthe ponds were excavated and placed in low areas of the landfill prior to the installation of the cap. Currently, only two surface water locations still exist (due to landfill cap construction) Compilation of history data Draft aev.doc Mar. 11.02 4-4 Wllmlnglon, DE JS0015078 EID620813 Main Plant and Landfllte______________________________________Letartj-andfill and are being sampled. These locations include the leachate from die landfill [location 002(leachate basin)] and the stream located slightly east oflhe property line along Rt. 33. The locations of these surface water-sampling points are shown in Figure 4.2. 4.3.2 Groundwater Quality Groundwater from die monitoring wells has also been voluntarily sampled and analyzed for C-8 periodically since 1991, However, sampling did not take place on an annual basis until 1996 and quarterly sampling began the second half of 1999, when C-8 was added to the pennit as a monitoring parameter. Table 4.1B presents all historical analysis available for C-8 from monitoring wells at the Letart Landfill The limited data set makes contouring the values difficult, therefore, the values were posted on maps and not contoured. Figures 4.6A through 4.6D present the C-8 concentration values for July 2001, January 2000, July 1999, and November 1991, respectively. An initial examination of the groundwater data does not show any obvious overall concentration trends (Table 4.1B). For wells having data from 1991 through 2001, it appears that the concentrations measured in 1991 were the lowest. From 1991, the concentrations in all wells increased. Currently, concentrations are now decreasing again to the most recent samplmg events. However, identifying trends in the data is complicated by the fact that three different analytical laboratories have been contracted to perform me analysesbetween 1991 and 2001. In addition, the effects of title installation of the engineered cap system (preventing further surface water infiltration) may or may not be observable in the limited recent data. For the most recent sampling event and analysis (October 2001), the sampling and analytical procedures, and the analytical instrumentation used were modified to gain better accuracy to the C-8 analytical results. These modified procedures will be utilized for all future analysis of groundwater samples for C-8. Continued monitoring of C-8 concentrations in groundwater is required to accurately evaluate the long-term trends in groundwater quality, If it is assumed that impacted groundwater flows from Zone A downward to Zone F and ultimately migrates to me Ohio River, the C-8 historical mean. for LMW-5B (Table 4.1B) can be used along with the estimated groundwater flux to calculate the C-8 loading to the river. The following assumptions were made in this calculation. Q The saturated thickness is 25 ft at LMW-5B. This is higher than the most recent groundwater elevation measurement and therefore, is a conservative value. 0 The length of the aquifer dischargingto the Ohio River is 1000 ft based on the geologic cross-sections. Q The historical mean value of 855 ug/1for LMW-5B, a downgradient well, represents me concentration of C-8 in me aquifer. Q The velocity of groundwater in me aquifer is 0.01 ft/day. Gioundwater average linear velocities for Ae F zone are calculated to be 0,01 ft/day from the north to the southwest and 0.003 ft/day from the north to the southeast (DuPont, 2000). Using these assumptions,the calculation for loading to the Ohio River is shown below: Compilationof Mstary data Draft 2rBv.doc Mar. 11,02 4.5 Wilmlngton, DE JS0015079 EID620814 ^w'1' Mn Plant and Landflljg____________________________Letart Landfill A = Area = 1000 ft lengthx 25 ft saturated thictoe$s for Zone F = 25,000 ft2 V " VelocityI- 0.01 ft/day (estimated) (^flux^AxV- (25,000 ft2)x (0.01 ft/day) x (7.48 gal/ft3)x (365 day/yr.) = 682,550 gaVyr Mass - (855 ugO) x (Ig/lO'ug)x (Ikg/lOOOg)x (I lb/2.205 kg) x (4.785 1/gal) 1.47x1 O^lb/galx 682,550 gal/yr = 1 x 10'3 Ib/yr Estimated annual loading to the Ohio River is very low based on the calculated mass and should result in a very low C-S concentration to the Ohio River. The low calculated mass is reasonable given the low hydraulic conductivities and low average linear velocities observed in the F zone. 4.4 Site Conceptual Model The Letart Landfill site conceptual model describes the potential exposure routes for current and future human and ecological receptors. Potential exposure routes were evaluated and classified as complete or incomplete, The Letart Landfill closure was completed in April 2001 with the installation of an engineeredcap system. The engineered cap system prevents human and ecological contact with the landfilled materials. Contact with landfilled materials would only be possible if the cap system were to be intentionally breached by workers or trespassers or by extensive, vigorous digging by animals. However, dense vegetation and appropriately installed fencing restricts access by unauthorized individuals and animals. Therefore, direct exposure to landfilled materials is a potentially complete but very limited exposure pamway. Exposure of landfilled material because of erosion of the engineered cap system due to storm nmoffis also a potential human and ecological exposure pathway. However, cap system drainage controls were designed to convey the nmoffftom the landfill cap to a designated discharge point and to eliminate the potential for nmoff-related erosion of me cap. hi addition, the landfill cap is required to be inspected at least quarterly (permit requirement C. 12.A) for evidence of erosion as part of the site Storm Water Pollution Prevention Plan. Therefore, this potential exposure pathway is also a potentially complete but minimal exposure pathway. The Letart Landfill engineered cap system prevents surface water from contacting landfilled materials. Surface water migrates towards drainage ditches constructed in the cap system and is dischargedat me southern edge of the landfill. Because this surface water does not contact the landfilled materials, it is not impacted by C-8, Therefore, contact with this surface water is an incomplete exposure pathway. Groundwater contacting the landfilled material has been impacted by C.8. Contact with this impacted groucdwater presents a possible human and ecological exposure pathway due to groundwater flow patterns. Groundwater flow under the landfill has shown mat prior to the installation of the engineered cap, surface water impinging on the landfill Compiallon of Nstory date Draft Srev.doc Mar. 11,02 4-6 Wilmington, DE JS00150BO EID620815 Main Plant and LandBlte_________________'..._..__________Letart Landfill migrated downward through the landfill material. These waters continued to flow as groundwater downward towards Zone P where it then flowed laterally to the west and south. Currently, the engineered cap prevents surface water from contacting the landfilled materials although groundwater migrating laterally and vertically underneath the landfill may still contact the landfilled materials. Oroundwater under the engineered cap migrates to the leachate collection system. Discharge from the leachate collection system is pipedto an outfall [002(Ieaehate basin)] where it entera a small, shallow, wet weather stream that flows approximately 400 feet before it dischargesto the Ohio River. Contact wim leachate is a potential pathway exposure route for current and future human and ecological receptors, however, this pathway is considered complete but limited due to the restricted access to the area. Zones D/B and F occur at elevations lower than the leachate collection system. Grouadwater flowing from these zones to the south discharges to the Ohio River. Contact with this water is limited to the areas where these zones may outcrop on the valley waUs. However, in general, groundwater flows downslope within the shallow soil, colluvium, and fractured rocks of the valley walls and would only be exposed at the surface if seeps exist. Cwwsirtly, there is no data available on the existence or location of seeps on the slopesadjacent to the landfill or along the Ohio River, Therefore, evaluation of this potential pathway exposure route for current and ftiture human and ecological receptors is not possible at this time, Groundwater that flows to me west from Zone F is likely to discharge to nearby valley drainage systems and to ultimately migrate to me Ohio River. Again, groundwater flows downslope within the fractured rocks of the valley walls and would only be exposed at the surface if seeps exist. Currently, there is no data available on the existence or location of seeps in the valleys south of the landfill. Therefore, evaluation of this potential pathway exposure route for current and future human and ecological receptors is not possible at this time. 4.5 Date Gaps The following data gaps were identified for the Letart Landfill: 0 Identify the locations of seeps in the valley walls, particularly in the steep valley wall along me Ohio River, and determine water quality with respect to C-8 concentration, 0 Determine the C-8 concentration in the Ohio River. a Determine the C-8 concentration in streama and other surface water bodies. Q Acquire additional geological data to refine the Site Conceptual Model. 3 Install additional monitor wells to provide additional groundwater flow data and p-ouadwater quality data. a Gather additional C-8 concentration data from monitoring wells for plume delineation, Activities to fill me data gaps will be proposed and discussed in the work plan. Compilation of history date Draft 2rev.doc Mar. 11,02 4-7 Wilrnlnglon, DE JS0015081 EID620816 Main Plant and Landfill Umtllilla_________________________________________Letart 4.6 References DuPont 1993. Letart Landfill Hydrogeologic Evaluation, July 1993. Corporate Remediation Group. ___. 2000. Letart Landfill Groundwater Protection Plan SWNPDES WY0076066, January 7,2000. Corporate Remediation Group. Permit No. ___. 2001. Certification Report Letart Landfill Cap Construction, June 2001. Corporate Remediation Group. TetraTech Richardson. 1989. Monitoring Well Installation Program, October 1989. . 1990. Monitoring Well Installation Program at Letart Landfill-Summary Report, August 1990. 919i Comptetlon of history data Draft Zrev.doe Mar. 11,02 WllminBton, OE 4.8 JS0015082 EID620817 Table 4,0 Monitoring Well Construction Data 1-etart Landfill Letart, WV Zone A C D F Monitoring Wells LMW- 1 LMW- 7 LMW- 8 LMW- 3 LMW- 3A LMW- 4 LMW- 5A UVEW- 2A LMW- SB LMW- 6 LMW- 9 LMW- 10 LMW- 11 Surface Elevation (feel^ 768.53 770.24 777.06 673.1 672.6f 649.17 645.23 77a.53 644.39 754.22 774.85 732,37 774.34 Total Depth (feet) 33 3S 38.5 30 60,1 28 28 180.8 72 183 225 189.85 161.5 Wel! Diameter (indies) 2 4 4 2 4 2 4 4 4 4 4 4 4 Slot Size (inches) 0.010 0.010 0.010 0.01,0 0.010 0.010 0.010 0.010 Screen Length (foeQ 5 10 9 5 5 8 10 30 20 30 30 20 25 Elevatio Screen In ffeet> 73^.53-73 745.24-73 748.06-7 650.1-64 819.81-61 626.17-8 627.23-62 628.53-59 S94.3&-5 608.22-57 572.85-65 562.52-54 637.84-61 Table 4.1A Summary ef Analytical Results: C-8 in Surface Water Samples Letart Landfill Letart, VW ''A.; ';&. sAA;--.. 002(LEACHATE BASIN) LEACHATE LOWER POND N SPRING FLOW RT 33 STREAM STREAM MN RD 8W SPRIN@ PlOW UPPER POND ; ^ ' . Bate ^:' ,..,, 7/2S/2000 .i.j'.- 4/3/2000 1/14/2000 10/21/1989 11/27/2001 7/20/01 7/25/200Q 7/20/1999 1/14/2000 4/30000 10/2t/-i96B 7/19/'(999 5/28/1998 7/23/1997 4/17/1996 9/20/1994 3/15/1994 12/27/1891 11/22/1891 4/2B/1991 .... y ^ ^ 2161^1 ..- 1/16/1991 3/12/1892 3/12/1982 7/20/2001 """ 7/31/20tir ' " 7/20/1989 7/23/1997 4/17/196 3/15/19B4 9/20/1994 3/12/1S92 7/19/1999 5/28/1998 7/23/1997 4/17/1996 3/15/1994 1Z/27/19S1 11B2/1681 4/2S/1991 3/22/1991 2/8/1691 1/1B/1891 c-a'@i-;.> 1350 1900 920 3240 S3.2 1S9 22SO 1030 1410 1260 2630 Use 1100 1600 1900 2200 730 1300 1000 670 340 400 1200 0,3 0.3 2.01 O.S73 2,2S 2 1.8 O.S 0.9 1 617 480 <200 2100 4400 4100 790 930 500 2300 2900 -f-v, JS0015084 BID620819 Table 4.1 B Summary of Analytical Results: C-8 in roundwater Letart Landfill Letart, WV .i'^^si^^- K:,,.. ?-,:' ^MittuSo. ...'-'... LMW-2A LMW-SB LMW-6 LMW-9 ^''iSii1!^^:' V-sw'SWKSS'^. 7/19/2001 1/30/2001 10/6/2000 7/25/2000 4/3/2000 1/14/2000 10/21/199B 7/20/1669 5/28/1598 7/23/1B97 4/17/1996 B/20/1B94 3/15/18B4 1102/1991 3/Z2/1S91 7/20/2001 7/20/OKtiurt 1/31/2001 lOB/ZOOO 10/8/00 (dup) WlW 4/3/2000 4/3/00 (AID) i/waooo 10/21/1999 10/21;99 (dup) 7/20/1999 7/23(1997 9/20/19S4 3/15/1994 11/22/1991 3/22/1691 1/13/2000 S/2a/199a 11/22/1991 3/22/1991 10/7/1992 .-^ft'^w^:. ^sss^wswa. 242 423 248 27B 306 ---"" 4$3 370 350 990 460 460 279 . 260 83 50 483 592 616 1190,J 780 800. J 1100 1020 1030 1750 1700 445 480 530 1200 380 340 9,4 '""""""""""-"SO 24 25 0.2 w-'\ y^ J estimated value (below laboratory quantitation limit). ^Sl'i:' ii-s;.. ,.' .' ':sV.-.'.....,f*ft,..(a%E^feW'el]:.,.^,^ . :.: .,,.',,;, .: staias-" :.: " i "^wsw., . (XTAe/o ; : ^ : ^ ^ . LMW-3A 7/18/1999 605 11/22/1991 ., - 1.-.11--^ a/22/1991 380 LMW-4 4/3/2000 272 1/14/2000 172 11/22/1961 3/2B/1991 830 690 .. LMW-5A 11/22/1991 0.8 302/1991 1.6 JS0015085 EID620820 Table 4.1B Sunimary of Analytical Results (Con't): C-8 in Groundwater Letart Landfill Letart. WV ^ ^'y^: """- B,.. ! - .;Si>te'-.- LMW-3 '.^.^e^^TSWS;^^'. ,: .. ^ , D^^A;.'A. -^^." .n,g2/i9?i 3/22/1991 04(180).. 1000 390 .''" .,:,to e"" "-'ii''-' >--.- -->:-"-;- ,^. ""^ ; .-...;.;.--^ a* *a--m--piiB- .. - UflW-1 LMW-7 LMW-8 .^/^^..zjjiBt'waft: i':. "" T-,',1^.:.^", ',.,. '- ttttfi8 ;;'"'* 7/19/3301 -;:'',:-." 1f31C!1 10/4/2000 7ffi4/200Q 4/312000 ' 1rt&aoo6 ' ---10/21/199'9 7/20/1BB9 S28/19B8 mwosst 4/17/1996 11/22/1991 3/22/1991 7/200)01 1/31/2001 1Q/4/2000 rissaaoo --""WoBO1 1/13/2000 10SO/1&69 7/20/1SSS S28/1B98 7/23/16S7 4/17/1996 11/22/1991 7/19/2001 1/30/2001 1QWZQOO 7/24/2000 4/3/2000 1/13/2000 10/20/1999 7/20/1BB9 S/2B/1SSB 7/23/1997 4/17/1996 11/22/1991 OStliSflt" 6100 8160 10600 8990 13600 17400 12600 6920 24006 S100 1700 88 60 242 249 231 158 211 219 339 78-3 260 53 15 0.1 1120 26SO 2300 2160 2180 2100 3260 17BO 2700 2000 2200 280 ^'"';' ... JS0015086 EID620821 Main Plant and Landfills Dry Run Landfill 5.0 DRY RUN LANDFILL Iiitnidurtinn.,...,,,,,,.,.,,,... environmental Setting,,,, Wate Quality..___,, Site Conceptual Model.. Datt Gaps,.........-.--...... References..................... Table 5.0 Tahle5.1A Table S-l B Tabia Dry Run LiifldfiUMonitorini; Wells CcmstniaionDiila Diy Rim landfill Analytical DatTbl~ SwfteeWBlaDty Rmi Landfill Analytical Dt Tables - OtQundwate Figure 5.0 FigurtS.l Rguti 5,2 Figure 53 Figard 5.4A Flpire5,4B FigwB5.5A R(lire5,5B Figure S.5C Rgw?5,5I> Figure I.5E Figure 5.6A FigCTr 5.6B Fiiare5.6C RgurB 5.6D Figure S.(E FIBBS i.6F Figures Dry Run Landfill Localion Map Dry Rim Landfill 1-mile Radius Map Diy RUB Landfill Meniloring Wril rad Surface Water Sample LocaUnn Map Diy Run Landfill Cross Section Location Map fay Run Landfill Cress Ststioa A-A' DiyRinil-tiislfilICrottSeetiOTB-B' Diy Run LandBl) Gwutdwattf Btealiett Map -Octoba 2001 Dry Ran LBldfiB Gn>Udwler EicratiTM Map Oclotitr 3999 Diy Run LanlUB) Orounthiffitn Elevation Map -Oaobar 1998 Dry RIBI Landfill GrouiidwiiKr StevitloB Map Oaobfl' 1993 Dry Ran Landfill Croimdwmer Elevation Map - April 1992 D(y RUB C-8 CoaaaitraticB Map Bedrock Wells - July 2000 Dry Rim C-8 ConccBtnition Map Bedrock Wells My 1999 Diy Run C-8 Concentratiun Map Bedrock Wcllil- July 1997 Diy Run C-8 Cflttcnttratieti Mtp Overburdni Wnlls " luly 2006 Diy RBI 0-8 Coiicenaation Mtp Ovsbiirttn Wtlli - July 1999 Diy Run C-8 Concettiatkm Map Ovcrbunlen Wells - May 1998 .,,.,, 5-2 .,,...5-2 ......5-4 ......5-5 ......5-6 ....... S-6 Compilation of historydata Draft SBV-doc Mar. 11, 02 WIlmlngton. DE 5-1 JS0015087 EID620822 Main plant and tandflte __ _ .._.__ Pry Run Landfill 5.1 Introduction The Dry Run Landfill is located west of the town of Lubeck, in Wood County, West Virginia (Figure 5.0) and is about eight miles southwest of the Washington Works main plant sad fhe Local Landfill. A water use and well survey search is being completed for the area within a 1-mile radius from the Diy Run Landfill perimeter (Figure 5.1). The Dry Run Landfill covers approximately 17-acres of a 535-acre parcel of land owned by DuPont. The landfill began operation in 1986 and is still active at present. The landfill is operated under West Virginia Solid Waste /National Pollutant Discharge Elimination System Permit No.WV 0076244. This permit requires quarterly groundwater momtoringand monthly outfall sarface'water'mBnitOring; " --- " Figure 5.2 shows the location of the landfill, nionltoriBg wells and surface water samplingpoints. The landfill was constructed within the drainage basin of Dry Run, a tributary of the North Fork of Lee Creek, which is atributary of the Ohio River. The Dry Run Landfill has no compacted or synthetic bottom liners. However, natural soil present under the landfill material is composed of clay and weathered shale. The Dry Run Landfill receives waste from the main plant consisting of non-hazardous waste including scrap product, scrap metal, wood pallets, fly ash and bins, and miscellaneous ttash. Approximately 50,000,000 pounds of waste per year have been disposedin the landfill. Currently, the C-8 source is believed to be the sludges from the closure of the main plant anaerobic digestion ponds that were laadfilled at Dry Run in 1988. The Dry Run Landfill remaining capacity calculations for 2001 show 4.4 years of remaining life on fhe existing cell based on a 128,000 yd^yr net fill volume consumption (DuPont 2000). 5.2 Environmental Setting 5.2.1 oology The Dry Run Landfill is situated on a heavily dissected plateau consisting of several steep V-shaped valleys. Residual soil covers most landfill areas, m general, the soil at fte site > has been described as residual in nature, consisting primarily of heavy elays derived {mm me weathering of shale. A geotechnical investigation for the Dry Run Landfill was completed by DuPont (1996). The investigation consisted of advancing soil test borings, test pits, laboratory testing of soil physical properties, stability analyses, and settlement analyses. DuPont (1996) determined that the natural residual soil underlying me landfilled materials consisted of stiff to very hard silly clay and clayey silt with occasional rock fragments and a trace of sand. The thickness of this natural soil ranged from 12 to 28 feet m the test borings within the landfilled area. A 1989 monitoring well installation program, prepared by Tetra Tech Richardson Inc., indicated similar silty clay and weathered shale overburden. Four ConipBatiOfl of hltoiy date Draft 2rev.doc Mar. 11.02 5-2 Wllmington, DE <7S0015088 EID620823 Main plant and LandRib________________________Dry Run Landfill overburden wells (DBMW 12A, 12B, 13A, 6A) were installed to depthsranging from 11 to 17 feet. The underlying bedrock at die Dry Run Landfill consists ofinter-bedded red and varicolored sandy or calcareous shale, and gray, green, and brown sandstone of the Permian age Dunkard Group (Tetra Tech Richardson, 1989). The maximum thickness of die Dunkard Group in this region is 570 feet. The location of two cross-sections, A-A* and B-B', crossing the landfill and downgradient of the landfill are shown in Figure 5.3. The two cross-sections are shown in Figures 5.4A and 5.4B. There are only a limited number of deep monitoring wells around and upgradient from the landfill (DRMW-14). Dashed geologic contact lines were drawn on cross-section AA' (figure 5.4A) because Acre is not sufficient data to confidently extrapolate between DRMW-14, the upgradient well, and DRMW-13, the downgradient well. More geological data is available (DRMW-6, -11, -12, and -13) and was used in developing the downgradient cross-section, B-B' (Figure 5,45) with more confidence. Cross-section BB' supports the interpretations made in cross-section A-A* of rather flat lying stratigraphic units of sandstone layers separated by shale layers. 5.2.2 Hydrology, Hydrogeology and Groundwater Flow Hydrology The Dry Run Landfill is situated on a heavily dissected plateau consistingof several steep V-shaped valleys. Dry Run drains the valley in which the landfill is located. Many small tributaries discharge from the nearby valleys into Dry Run before it joins up with tfae Norfli Fork of Lee Creek. Potesta & Associates, Inc. (1989) completed a hydrologic and hydraulic analysis of the receiving stream below the Dry Run Landfill, They determined that the watershed soils are split between hydrologic soil groups (HSG) C and D and estimated the How capacity at 481 cubic feet per second (that is greater man the 100-year 24-hour stona). Potesta (1989) also evaluated A@ 24-hour precipitation amount mat would result in full flow conditions at the location where the capacity was estimated. Potesta determined that precipitation values between 5.25-5.99 inches in 24 hours would result in full flow. The installation of a leachate collection system at the Dry Run Landfill encompassingme inactive lower half of the landfill was completed by Potesta & Associates me. to 1999. . Leachate from the landfill discharges into a leachate collection sump located northwest of the landfill (Figure 5.2) through perforated pipesburied at the low edge of me fill area. The leachate is pumped from the collection sump to a 50,000-gallon collection tank located at the top of the hill. Leachate is pumped from the collection tank to a tanker truck, which is then hauled to the main plant for treatment in the site's wastewater treatment plant. Hydrogeology Groundwaler is found in the overburden and the underlying bedrock aquifer. The bedrock aquifer is considered the underlying significant aquifer forNPDES permit required groundwater monitoring. A total of 15 monitoring wells have been installed at Dry Run to monitor the overburden and bedrock aquifers. At this time, four overburden Compilation of history data Draft Zrev.rtro Mar, 11. OZ 5-3 Witmington, DE .780015089 EID620824 Main Plant and Landfilte___^ ___________________________Dry Run Landfill wells (DRMW-6A, -12A, -12B, and 13A), and four bedrock wells (DRMW-12, -13, -14, and -15) still exist. The other seven wells were abandoned in 1999 by Potesta & Associates, Sic. as required by the permit because they were not being utilized for quarterly monitoring (Potesta. 1999). Table 5,0 provides the well construction data for existing monitoring wells. Groundwater Flow Water levels measured in November 2001 indicated overburden groundwater was encountered between 4 and 6 feet below ground surface. Although 3 of the 4 wells completed in the overburden monitor the same hydrogeologicunit, well DRMW-6A is completed at a relatively higher zone, which is discontinuous at lower topographic areas. N0 groundwater flow maps were prepared for the shallow water encountered in the overburden section. Annual groundwater elevation maps for the underlying significant aquifer were available for the years 1992-1994, and 1998-2001. These maps are presented in Figures 5.5A through 5.5G. The groundwater contours were transferred from til original maps submitted for the permit to the updated Dry Run Landfill base map. These maps show that youadwater in the bedrock aquifer flows from the southeast towards the northwest. The groundwater elevations measured for nested wells (DRMW-12, -12A, and 12B, and DRMW-13 and -13A) are similar and the screened zones are constructed relatively close to each other, indicating that the overburden and bedrock aquifers may be in hydraulic communication downgradient of the landfill. 5.3 Watar Quality 5.3.1 Surface Water Quality Historical surface water C-8 concentrations arc presented in Table 5.1A for six sampling points. Sampling location for surface water sampling points still in existence can be found on Figure 5.2. Surface water sampleshave been collected periodically from these locations since 1996 and have been collected consistently for three locations (DRLeachate, Outlet 001 and at the property boundary) since 1998. The concentration of C-8 in the leachate samples have been decreasing over time (from 62 ug/1 down to 27.4 ug/1)while concentration from the other locations are variable and do not indicate a clear trend (Table 5.1A). 5.3.2 Qroundwater Quality Historical groundwater sampling began in 1996. For wells that currently exist, sampling continues (DRMW-6 was abandoned in 1999; Potesta. 1999), C-8 concentration were contoured for some of the sampling events for the overburden and bedrock wells. These concentration contours can be found in Figures 5.6A through 5.6 F. Data shown to Figure 5.6E was plotted but not contoured due to the data spread. The data for DRMW12-B and DRMW13-A for July 1999 appears anomalous compared to the other data for these two wells. The contour maps show that the highest concentration of C-8 existe in monitoring wells 13 and 13A, bedrock and overburden wells, respectively. Compilation of histoly data Draft 2rev.doE Mar. 11, 02 5-4 Wllmlngton, DE JS0015090 EID620825 Main Plant and Run Landfill Lanjjjilg________________________________________Dry J These two wells are located downgradient from the central axis of the landfill. For the majority of the sampling events for most of the other wells, both overburden and bedrock, the C-8 concentration has been less than 1 ug/1. The C-8 concentration for the 1999 sampling event in DRMW-14 was higher than other values measured for this well. Given that this well is an open bedrock well, and is relatively close to the landfill, this higher concentration may indicate communication of surface or shallow aquifer waters through Hie open well, particularly because groundwater flow in the underlying significant bedrock aquifer flows from DRMW-14 north west toward the landfill area as opposed to groundwater flowing from the landfill toward the DRMW-14 well. 5.4 Site Conceptual Model The Dry Run site conceptual model describes the potential exposure routes for cuireat and future ecological receptors. Potential exposure routes were evaluated and classified as complete or incomplete. Access to the Dry Run Landfill by is controlled by electronic gates on the major roads and locked gates on smaller roads. In addition, because the landfill is active, (here is a. crew of workers on the landfill area during normal working hours. The daily activity discourages trespassers on me site. Therefore, direct contact with landfilled materials is a complete but minimal exposure route, limited to the workers in active portions of the landfill. Direct contact with landfill materials u the inactive, lower half of the landfill is incomplete due to the leachate collection system's gcotextile and geomembrane cover. Contact with leachate at the landfill (or at the main plant where the leachate is treated) is considered a potentially complete but limited exposure route for the landfill and plant workers and samplers. Currently, &e inactive lower half of the landfill is covered by geotextiles and geomembranes of the leachate collection system. Therefore, precipitation falling on this portion of the landfill does not come in contact with the laadfilled materials. This precipitation flows downslope via overland flow and discharges into storm water drainage ditches and'eventually reaches Dry Run Creek. Therefore, this potential exposure route is considered incomplete. Precipitation falling in the upper half of me landfill may also flow via overland flow down slope to me drainage ditches, agate, an incomplete exposure route. Alternatively, this precipitation may infiltrate and come in contact with the landfilled materials as it migrates downgradient. However, this impacted water flowing within the landfill may be collected by the leachate collection system. If this impacted water migrates downward through (he landfilled materials, it may eventually come in contact with the underlying shales and sandstone of the bedrock and migrate downgradient within the bedrock aquifer. Contact with impactedgroundwater is a potentially complete exposure route alAough currently, not enough bydrogeologicdata. exists to accurately evaluate this exposure pathway. Plans are underway for the expansion of the leachate collection system and for a final cap/cover system. These activities in the future will further reduce precipitation infiltrating and contacting landfilled materials. CompBation of N5(617 data Draft 2rev.doc Mar. 11,02 5-5 WIWngton, DE JS0015091 EID620826 Main Plant and landlills_____________________DfyjJun Landfill 5.5 Data Gaps The following data gaps were identified for the Diy Run Landfill: Q Identify the locations of seeps in the valley walls and determine water quality with respect to C-8 concentration. Q Determine the C-8 concentration in streams aid other surface water bodies. Q Acquire additional geological data to more accurately develop the Site Conceptual Model. 0 Install additional monitor wells to provide additional groundwater flow data and gr&imdwater quality data. Q Gather additional C-8 concentration data from monitoring wells for plume delineation. Activities to fill the data gaps will be proposed and discussed in the work plan. 5.6 References DuPont. 1996. Report of Geotechnical Investigation Dry Run Landfill, Washington Works Main Plant, Parkersburg, WV. Geotechnical Group, Civil Engineering Systems, DuPont Engineering. April 23,1996. ___. 2000. 2000 Dry Run Landfill Operational Report. Submitted January 26,2001. Potesta & Associates, Inc. 1989. Hydrologic and Hydraulic Analysis of Dry Run, Area No. 1. October 9,1989. Letter from D. Mark Kiser to Dan Weber. . 1999. Monitoring Wells MW-1. MW-IA. MW-4, MW-4A, MW-6, MW-10, MW10 Abandonment Report, Dry Rim Landfill, DuPont Washington Works. March 1999, TettaTech Richardson. 1989. Monitoring Well Installation Program, October 1989. Compilation of historydata Orafl Zrev.doc Mar. 11,02 Wilmlngton, DE fr6 JS0015092 EID620827 '^ Table 5.0 Monitoring Well Construction Data Dry Run Landfill Lubeck, WV Manftoring Wells DRMW- 14 DRMW- 13 DRNW- 13A DRMW- 12 ORMW- 12A DRMW- 12B DRMW- 6A DRMW- 15 Surface Elevation (feet) 936.14 720.6 720,3 730.5 730.3 730.8 744.93 730.87 Total Depth {fwt) 260 35 11, 35 17 15 12-2 45 Well Diameter (Inches) 10 4 4 4 4 4 2 2 Slot Size finches) NA 0.010 0.010 0.010 0.010 0.010 0.010 Screen Length (feet) NA 1S 5 15 5 10 Elevation of Screen Interval (feet) NA 700.6-685-6 714.3-709.3 710.5-895.5 718.3-713-3 72S.5-715-5 20 705.87-685. B7 Table 5.1A Summary of Analytical Results: C-8 in Surface Water Samples Dry Run Landfill Lubeck.WV w.'i'tW 'i^MBiAe. .:;' r'S.Ta '.-. ^: ": nxt.i-r'i';"''6'1 j, .?:;.>-" DOWNSTREAM 4^1998 C4l^B '"ZS ' ' /-'^'A-" ' """ OUTLET OQ1 PROPERTY BOUNDARY STREAM SAMPLING POINTO STREAM 8AWUNQ PQ1NT2 1209/1999 5/18/1988 7/22/1W 10/3/2000 12Q9/'199 5/19/199B 4/9/1896 10/3/2000 4/9/1996 T/W1998 12/29/1999 10/3/2000 12/29/19S -^ wwsm"" - 10/3/2000 1288/1999 5/19/1998 34 56 62 31.8 66 17 86 10.3 9,6 0.88 39 o.7sa 0.54 " \ 27.6 67 4.6 JS0015094 EID620829 Table 5.1 B Summary of Analytical Results: C-8 In Groundwater Dry Run Landfill Lubeck, WV .: "": ^ : ~smW:. DRMW.12 DRMW-12A DIWIW-12B DRMW-13 DRMW-13A DRWW-14 DRMW-16 DRMW-6 DRMW-6A .-'B^ l<e- saSfSiKSK 7/19/2000 7/21/1899 312WQQB 7/Z2/1S97 4/10/1B96 7/1&/2000 7/21/1999 5/26/1999 7/22/1S87 4/10/1SS8 mwsm 7/21/1998 6;16/1B9B 7/29/2000 7/21/1999 5B8/1996 7?22/1997 7/20/2000 7/21/1999 5/26/1998 7/22/1997 4/10/1B96 4/10/1998 (An) 7/20/2000 7/21/1999 n'l99 7/21/1997 4/10/1996 7/20/2000 7/21/1999 7/22/1997 4/10/199B 7QO/2000 7/21/1999 S/2B/1998 7/22/1867 4/10/1996 ^y CWSSK'-:.f . 0.16 0.134 <0.10 t0.1 <0.1 0.128 0.061 J <0.10 <0.1 <0,1 ND (0.029) S.4 t0.1 9.8 3.6 ""' 9.2 7 9.9 0.070 J 8J 11111 15 ""1" 8.2 11 "11"1 , 1--"1 0.115 2.5 <0.1 ^ .,-,,,. <0.1 0.763 0.263 1 0.97 0212 0,086 0.27 0.36 0.19 J a estimated value (below laboratoiy quantltatfon Hmtt). JS0015095 EID620830 FIGURES JS0015096 EID620831 w Figures can be found on hard copy in central files. JS001S097 EID62083"2 I.* APPENDIX 1 CONSENT ORDER (ORDER NO. GWR-2001-019) JS0015098 EID620833