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AR226-2507 COMPILATION OF HISTORICAL C-8 DATA DUPONT WASHINGTON WORKS MAIN PLANT AND LANDFILLS Date: January 2002 Project No: D6WW7423 h^ CORPORATE REMEDIATION GROUP An ASSamnbetmmn DuPontend tlHS Diamond B u ky Mill Ptea. Building 27 Wilmington, Delaware 13805 JS 0 0 1 5 0 4 2 1ID 620777 "II-- TABLE OF CONTENTS 1.0 Introduction 1.1 Document Organization I________ 1.2 C*S Historical Laboratoi|r Analysis 2.0 Washington Works Main Plant. 2.1 Introduction. 2.2 Environmental Setting..., 2.2.1, Geology.-------- 5..........................,, .....,, ,.1 ^ ^ ; , 2.Z2 Hydrology, Hydtpgeology and GrotmdwagMF 2.3 ------------ A------- ----------------- m k m 2.3.1 Surface Water Q uality.......... 2.3.2 Groundwater Q uality. 2.3.3 Drinking/Tap W ater Quality..,, 2.4 Site Conceptual M odel. 2.5 Data Gaps,..,, 2.6 References.... 3.0 Local Landfill..................... 3,1 Introduction.,.,,..,___ _ 3.2 Environmental Setting., 3.2.1 Geology...__ _______ ... J.2,2 Hydrology, Hydrogeology and Groundwater Flow 3.3 Water Quality., 3:3.1 Surface Water Q uality..... 3.3.2 Groundwater Quality.... . 3.4 Site Conceptual Model,,....... ...... 3.5 Data Gaps. 3.6 References, 4.0 Letart Landfill.... 4.1 Introduction >*****"' .4*1 4.2 Environmental Setting, 4.2.1 Geology......,,, 4.2.2 Hydrology, H y d f o g e ^ ^ i S i S 4.3 W ater Quality...... .................................. 4 J.1 Surface Water Quality........................... 4.3.2 Groundwater Q uality................... .4-2 .4-2 Z ; : : : ---------t44--t342 ..................... ................,44. --44. 4.4 Site Conceptual Model................................................................................. " t s 4.5 4.6 References..... ----- ..4-7 JS0015043 EID620778 Main P lert and Landfills Table of Contents 5.0 Dry Run Landfill....................... 5.1 Introduction............... 5.2 Environmental Setting....... 5.2.1 Geology................ 5-2.2 Hydrology, Hydrogeology and Groundwater Flow 5.3 W ater Quality 5.3.1 Surface W ater Q uality...>.*********< 5.3.2 Groundwater Quality' **********************< 5.4 Site Conceptual Model 5.5 Data Gaps 5.6 References *****! TABLES '****** 5-1 5-2 5-2 5-2 .,5-3 5-4 54 .... 5-4 .5-5 5-6 5-6 Table 2,0 Washington Works Mam Plant Monitoring W ells Construction Data Table %1A Washington Works Main Plant Analytical Data Table - Surface Water Table 2.IB Washington Works Main Plant Analytical Data Table-Groundwater Table 2.1C Washington Works Main Plant Analytical Data Table - Drinking Water Table 3.0 Local Landfill Monitoring Wells Construction Data Table 3,1A Local Landfill Analytical Data Tables - Surface Water Table 3.1B Local Landfill Analytical Data Tables - Groundwater Table 4.0 Letart Landfill Monitoring Wells Construction Data Table 4.1A Table 4.1B Table 5.0 Letart Landfill Analytical Data T ables-Surface Water Letart Landfill Analytical Data Tables--Groundwater Dry Run Landfill Monitoring Wells Construction Data Table 5.1A Dry Run Landfill Analytical Data T ables-Surface Water T*? 5.1B p ry Run Landfill Analytiral Dato Tables - Groundwater FIGURES Figure 1.0 Solubilities o f O7F15COOM in W ater as a Function o f Temperature Figure 2.0 Washington Works Main Plant Location and SWMU Map Figure 2.1 Washington Works Main Plant and Local Landfill 1-mile Radius Map Figure 2.2 Washington Works Main Plant Monitoring Well and Surface Water Sample Location Map Figure 2 3 Washington Works Main Plant Cross Section Location Map Figure 2.4A Washington Works Main Plant Cross Section A-A* Figure 2.4B Washington Works Main Plant Cross Section B-B* Figure 2.4C Washington Works Main Plant Cross Section C-C' Figure 2AD Washington Works Main Plant Cross Section D-D' CmptottonofhistorydaisDraft2*vttoc Mar.11,02 " ' Wilmington.DE : " --------- JSOO15044 1ID 620779 Main Plant and landfills Table of Contents Figure 2.4E Washington Works Main Plant Cross Section E-E' Figure 2.4F Washington Works Main Plant Cross Section F-F' Figure 2.5A Washington Works Main Plant Groundwater Elevation Map - November 2000 Figure 2.5B Washington Works Main Plant Groundwater Elevation Map - February 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 Landfill Location Map Figure 3.1 Local Landfill and Washington Works Main Plant 1-mile Radius Map Figure 3.2 Local Landfill Monitoring Well and Surface W ater Sample Location Map Figure 33 Local Landfill Cross Section Location Map Figure 3.4A Local Landfill Cross Section A-A' Figure 3.4B Local Landfill Cross Section B-B* Figure 3.5A Local Landfill Groundwater Elevation Map - November2001 Figure 3.5B Local Landfill Groundwater 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 Figure 3.5G Figure 3.6A Local Landfill Groundwater Elevation M ap-Decem ber 199$ Local Landfill Groundwater Elevation Map - December 1994 Local Landfill C-8 Concentration - May 2001 Figure 3.6B Local Landfill C-8 Concenttation-M ay 2000 Figure 3.6C Local Landfill C-8 Concentration - May 1999 Figure 3.6D Local Landfill C-8 Concentration *May 1998 Figure 4,0 Letart Landfill Location Map Figure 4.1 Letart Landfill 1-mile Radius Map Figure 4,2 Letart Landfill Monitoring W ell and Surface W ater Sample Location Map Figure 4.3 Letart Landfill Cross Section Location Map Figure 4.4A Letart Landfill Cross Section A-A' Figure 4.4B Letart Landfill Cross Section B-B* CompSaBonofhistorydata Draft 2rtrv.doc Mar. 02 WlmlnotmnF 111 JSO015045 EID620780 Main Plant and Landfills Table of Contents Figure 4.5A Letart Landfill F-Zone Groundwater Elevation Map - November 2001 Figure 4.5B Letart Landfill F-Zone Groundwater Elevation Map - January 2001 Figure 4.5C Letart Landfill F-Zone Groundwater Elevation Map - October 1999 Figure 4.5D Letart Landfill F-Zone Groundwater Elevation Map October 1998 Figure 4.5E Letart Landfill F-Zone Groundwater Elevation Map - December 1994 Figure 4.5F Letart Landfill F-Zone Groundwater Elevation Map - December 1992 Figure 4.6A Letart C-8 Concentration Map - July 2001 Figure 4.6B Letart 0 8 Concentration Map - January 2000 Figure 4.6C Letart 0 8 Concentration Map - July 1999 Figure 4.6D Letart 0 8 Concentration Map - November 1991 Figure 5,0 Dry Run Landfill Location Map Figure 5.1 Dry Run Landfill 1-rnile Radius Map Figure 5.2 Dry Run Landfill Monitoring Well and Surface W ater Sample Location Map Figure 5.3 Dry Run Landfill Cross Section Location Map Figure 5.4A Dry Run Landfill Cross Section A-A' Figure 5.4B Dry Run Landfill Cross Section B-B' Figure 5.5A Dry Run Landfill Groundwater Elevation Map - October 2001 Figure 5.5B Dry Run Landfill Groundwater Elevation Map - October 1999 Figure 5.5C Dry Run Landfill Groundwater Elevation Map - October 1998 Figure 5.5D . Dry Run Landfill Groundwater Elevation Map - October 1993 Figure 5.5E Dry Run Landfill Groundwater Elevation Map - April 1992 Figure 5.6A Dry Run C-8 Concentration Map Bedrock Wells - July 2000 Figure 5.6B Dry Run C-S Concentration Map Bedrock Wells - July 1999 Figure 5.6C Dry Run C-8 Concentration Map Bedrock Wells - July 1997 Figure 5.6D Dry Run C-8 Concentration Map Overburden W ells July 2000 Figure 5.6B Dry Run C-8 Concentration Map Overburden Wells - July 1999 Figure 5.6F Dry Run C-8 Concentration Map Overburden W ells - May 1998 Appendix 1 . Consent Order APP1NDIX CompaaUon or hriDfy data DraS 2w .doc Wilmington, PE 7S001S046 EID620781 Main Plant end Landfills Introduction 1.0 INTRODUCTION A multi-media Consent Order was entered into between the W est Virginia Department o f Environmental Protection (WVDEP), the W est Virginia Department o f Health and Human Resources-Bureau for Public Health (WVDHHR-BPH) and DuPont on November 14,2001, A copy o f the Consent Order (Order No. GWR-2001-019) Is contained in Appendix 1. The Consent Order identified a series o f 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 o f releases o f ammonium perfluorooctanoate (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 Groundwater 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 o f C-8 in drinking water, groundwater, and surface water at mid around the main plant, and die Local, Letart and Dry Run Landfills. Pursuant to Attachment A o f 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 o f Task B is to develop mad implement a monitoring plan that determines the presence and extent o f C-8 in drinking water, groundwater and surface water in and around die main plant, and the Local, Letart and Dry Run Landfills, and to provide a compilation o f available grotmdwater/surface water monitoring results and hydrogeologic 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 pfoi and the Local, die Letart and die Dry Run Landfills, respectively. Each section includes text, tables, mid figures specific to the site being discussed in that section. A t die end o f each section, data gaps are identified. D ie 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 -l o f foe Consent Order. In addition, supplemental information is provided as needed to develop and present a site conceptual model for foe four locations discussed. 1.2 C-8 Historical Laboratory Analysis o f 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 foe DuPont Experimental Station in Wilmington, Delaware, fa 1991, when foe RCRA Verification Investigation urns conducted, foe analysis was contracted to the CifeMHill Laboratory fa Montgomery, Alabama: Both labs used a Gas Chromatography/Electron Capture Compilation of history data Draft 2rev.doc M ar. 1 1 .0 2 WDmlnoton, DE JS0O 13O 47 EID620782 Main Plant and Landfills Introduction Dectector (GC-ECD) based analytical method with detection limits for 0 8 that ranged from 0.1 to 1.0 ug/1. CH2MHiU conducted C-8 analysis for DuPont into the fell o f 1998 when the laboratory ceased operation. At that time, DuPont had completed one round o f 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 analysis using 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) feat utilizes Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). DuPont adopted the use o fLC/MS/MS for C-8 analysis in November 2001. 1.3 Physicochemical Data fo r Ammonium Perfluorooctanoate (C-8) C-8, also identified as FC-143, is a fluorinated surfactant used in the fluropolymer manufacturing at the mam plant. Figure 1.0 shows fee solubilities o f C7Fi5COOM in water as a function o f temperature (Figure 6.9 in Kissa, 1994), The following summary lists the physicochemical date available for C-8 (Kissa, 1994): O Molecular Formula " CFj(CF2)tCOO'NH+ Molecular weight = 431.098 g/mole Q LDso acute oral rat = 680 mg/kg O BCF= 1,8 pH 5 (0.5% aqueous) pKa " 2,8 (-COOH) Q Melting Point 56-58DC (-COOH) Q COD ~700 mg/kg Q Koc=25 Water Solubility >1000 mg C-8/L Vapor pressure (at 22C) = 7.1 x 10-?mm Hg Q Kraft Point ~ 2.5 C Qi Critical Micelle Concentration = 33 mmol/L LO: L t l MD 5 0 having joitpfotabiEtyofcausisgdcalh ^ f" bam'd -^^B"ww*Ml*iidiifcrSda5t20dign><i*C ^ S S r--- Koc: OrgjaJc Carbm Fnthiaiteg Coefficient 1,4 References Kissa, E. 1994. Fluorinated Surfactants. New York: Marcel Dekker, fee. Compilation of history data Draft 2wv.iMx M ar. 11,02 WRmlngton, DE 7SO 015O 48 EID620783 Figure 1.0 Solubilities of C7F15 COOM in water as a function o f temperature (Kissa, 1994). JSO015049 EID620784 M an Plant and Landfills Washington Works Main Plant 2,0 WASHINGTON WORKS MAIN PLANT llroduction Environmental Setting.. ,, WitterQuality-- -- ,,,, Site ConceptualMode! . . . Data Gap*.-- ,,, ,, Refercncea^^.,.__ ___ _ Table2 4 Table 2,1A Thblo 2.1B Table 2.1C Figure 2.0 Figure 2.1 R poe 222 Figure 7 i Figure 2.4A Figure 2.4B Figure 2,4C Figure 2.4D Figure 2.4E Figure 2.4F Figure 2-5A Figure 2 Figure 2-5C Figure 2.6A Figure 2.60 T&W Washing!. Worte Mam Plant Monitoring Welle Construction Data Washington Works Main Plant Analytical Dali Table- Surface Water Washington Wort Main Plast AnalyticalBata Table- Groundwater Wajhington Worta Main Plant Analytical Data Table- Diinldng/Tap Wats' Figure Washington Worte Main Plan Location and 5WMUMap Washington Works Main Plantand Local Landfill l-mlle Radius Map ' Washington W ette Main Plant Monitoring Welland Surface WaferSample Location Mip Wasbsigton Worte Main plant C m Section Location Map Washington Worte Mam Plant C*s SectionA-A` Washington W ette Main Plant Ckoes SectionB-B' Washington Worte Main Plant CfO Section C-C' Washington Worte Main Plent Crona Section D-D' Washington Worte Main Plant Clo Section E-F` Washington Worte Main Plant Crosa Section P-F Washington Weste hfess Plant Gnsnn4waterEfevati6nMnpFleut3i^cr2060 Washington Wtnte Main Plant Groundwater Elevates Map - Primary i 999 Witthbgtoo Worte Mata Plant GroundwaterElevation Map - November 1298 Washington W eite Mata Plant C-8 Concentration Map- February 1999 Washington Worte Main Plant 0-8 Coneenttatte, Map- November 1998 - -- ..,,.2-2 -- .......2-i CornpBnBon of history duta D m * 2rev.doc IVter. 11, 08 Wlimln0ton.DE ---- TM - ' --------- ------------------------7T7 2-1 JSO015050 EXD62078S Main R ant and Inm lfflb Washington Works Man 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 o f Parkersburg, West Virginia (Figure 2.0). A water use and well survey is currently being conducted for the area within a 1-mile radius o f the m ain plant mid Local Landfill property boundaries Significant historical hydrogeologic and groundwater quality data for C-8 at the main plant is available from previous investigations that have been conducted. T ie most significant study was a Resource Conservation and Recovery Act (RCRA) Facility TM tig f ti n (RFO conducted in the fall o f 1998 on four Solid Waste Management Units (SWMUs) at the main plant to satisfy requirements o f the RCRA Hazardous mid Solid Waste Amendments (HSWA) Perm it Number WVD 04-387-2591 (DuPont, 1999). A brief description o f each o f the SWMUs investigated is presented below. SWMU locations are shown on Figure 2.0. SWMU A-3, Riverbank Landfill: The Riverbank Landfill is about 4,500-feet long and lies along the northern edge o f 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, Alter closure, it was covered with 6 to 35 inches o f soil. Currently, the 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 o f 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) nnrit jpgg when the pond contents and upper few feet o f clay liner and pond berm material w ise removed and disposed o f off-site. The pond area was backfilled and capped with topsoil, and the area is currently vegetated with grass. SWMU C-6, Polyaeetal Waste Incinerators (Waste Incinerators): The former Waste Incinerators consisted o f two brick-lined pits in the western portion o fthe m ^ufacturing area. The Waste Incinerators operated between 1959 and 1990, The Waste Incinerators have been excavated and backfilled with clean soil. SWMU H-14, Burning Ground: The Burning Ground is located in the central portion o f 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 buildings and asphalt A previous Verification Investigation (V 0 found evidence o freleases o f C-8 to soil and K f 'S T v S f O H * . foods, - d Buming Ground (D u g 1992). Little evidence o f releasee were found In soil at the site o f the fotmer Waste CompteBon o f history data D m * Zwy.doc M ar. 11. oe ... Wilmington, DE " " " ----------------------------- -- --- --------------- 2-2 JSO015OSI B ID 620786 Main Plant and Landfills Washington Works Main Plant Plant-wide groundwater sampling was also conducted during two separate monitoring events, the first in November 1998 and file second in February 1999, during the RFI. 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. A ll plant wells sampled during the RFI were analyzed for C-8. C-8 was detected in all groundwater samples. 0-8 concentrations and the extent in groundwater is discussed in Section 2,3 Water Quality. 2.2 Environmental Setting 2.2,1 Geology The geology o f the main plant is shown on six geologic cross-sections developed during the VI (DuPont, 1992) and revised based on additional findings from the RFI, The locations o f the geologic cross-sections are shown in Figure 2.3. Two east-west cross sections, A-A'and F-F, are shown on Figures 2.4A and 2.4F. Four north-south cross sections, B-B', C-C, D-D', and E-E* are shown on Figures 2.4B, 2 .4 0 ,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 terrace is topographically flat and lies approximately 50 feet above the Ohio River, which flows east to west past the main plant (sec Figure 2.0). The alluvial terrace is underlain by a flat, river-scoured bedrock surftce of the Dunkard Series that rises Steeply and outcrops in the southern edge o f the site to fbnn the valley w all The Quaternary alluvium ranges from 60 to 100 feet in depth and consists o fcoarsening downward unconsolidated river deposits o fpoorly to well-sorted, brown and gray sand, silts, clay and gravel. The Dunkard Series bedrock consists primarily o fred and varicolored sandy shale; gray, grew and brown sandstone; and minor beds o f coal, claystone, black carbonaceous shale, and limestone. The average river water elevation is about 580 feet above Mean Sea Level (MSL) and the elevation o f the Ohio River terrace deposits under the main plant are about 630 feet above MSL. Due to riverbank undercutting, some slumping o f clay and silt exists along the northern boundary o f the main plant along the river's edge. Figure 2.4C shows an example o f the relationship o f fill and clay layers along the riverbank. 2.2,2 Hydrology, Hydrogeology and Groundwater Flow Hydrology Regional water needs are primarily satisfied by the Ohio River and Little Kanawha River near Parkersburg, These sources provide water to the cities o f Parkersburg, ComplaBon c# history data Draft 2rw .doc M ar. 11,02 Wilmington, DE JSO0150S2 E D 620787 Main Plant and Landfills Washington Works Main Plant West Virginia and Belpre, Ohio, h i less populated areas (i.e,, near die main 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 die main plant discharges through drains and storm sewers, mid drainage swales. Seeps located along the riverbank may originate from precipitation that has infiltrated topsoil or fill and that flows along die top o fthe underlying shallow clay and discharges along die riverbank. Two drainage swales, one located in the facility's southwest comm, mid the other located on the extreme eastern end o f die facility, convey surface runoffduring rainy weather to the Ohio River. During dry weather, the drainage swales are dry. Hydrogeology Regional groundwater supplies are obtained from die Dunkard Group bedrock and Ohio River alluvial terrace deposits. The saturated portion o f the Ohio River alluvial terrace deposits comprise 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) (Schulte, 1984). Based on these high yields, numerous industrial mid 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, . D ie Ohio River alluvial terrace deposits contain a single key aquifer underlying the mam plant. The water table occurs at a depth o f 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 o f 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 o f the Dunkard Group (Washington Formation), which consists primarily o f shale and silt, likely bounds the lower extent o f the site aquifer. In addition, regional groundwater communication between the Ohio River and bedrock will likely result in upward gradients to the alluvial aquifer. Groundwater 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 o fall hydrogeologic units in the region (Schulte 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, w inaing. U Infiltration o fprecipitation falling directly on the alluvium O lateral movement o f the river water through the alluvium via permeable sand and gravel zones O Seepage from stream tributaries that discharge to the Ohio River The maximum amount o f water available to the alluvium depends on the degree o f hydraulic connection to the river. The degree o f hydraulic connection is a function o f the permeability and thickness o fthe riverbed, permeability and thickness o f the alluvium, and hydraulic gradient between the groundwater and the river. Pumping o f on-site active CMpItfonofhfctctyd a t o t i 2mv.doc Mar. 11,02 Wilmington, DE JSOO15053 EID620788 Main Plant and Landfills Washington Works Main Plant . well fields near and parallel to the :iver (i.e., the Ranney W< II, tl e ptiPont-Lubeck Well Field, and the East Well Field sho1 in Figure 2 2 ) lowers the mnndwater 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. mBM Groundwater Flow Groundwater generally flows to th south-southwest in to e a l|||y a q u ife r. However, groundwater elevations, flow directions, and flow rates on-site arc strorjgly influenced by die Ohio River and by pumping o f bn-site production wells, fSe'oh-site production wells include the Ranney W ell, a radial collector well whichpumpSOJb 1,000 gpm; the seven wells in the East Well Field, which pump a combined hverag rate o f2,000 gpm; and the five DuPont-Lubeck wells, which pump about 700 gpm epjmbined. 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 , Mid C, respectively. The direction o f groundwater flow is indicated by flie flow arrows. As shown on the groundwater elevation contour maps, groundwater flow in the northeast part o f the site is toward the East Well Field wells, to the northcentral portion o f the site, groundwater flow is toward the Ranney W ell, to the central and western portion o f the site, groundwater flow is south-southwest towards the DuPontLubeck Well Field. Pumping o f the production wells (Ranney Well, East Well Field, and the DuPont-Lubeck Well Field) eliminates off-site migration o f impacted groundwater that may originate from the SWMU areas. Additional groundwater elevation data was obtained from the General Electric (GE) property located to toe westo f toe main plant. Data from toe main plant and GE were used in calibrating toe Washington Works groundwater model (DuPont, 1999). The groundwater model conclusions indicated that groundwater from toe main plant area is contained to toe DuPont property by operation of the site production wells. to a 1990 hydrogeologic assessment, production well specific capacity testing o f the DuPont-Lubeck Well Field and toe East Well Field was conducted. The results were used to calculate the transmissivity Mid the hydraulic conductivity o f toe alluvial aquifer (DuPont 1990). to the vicinity o f the DuPont-Lubeck Well Field, transmissivity values ranged between 114,900 and 127,500 gallons per day per square foot (gpd/ft2). to toe vicinity o f the East W ell Field, the transmissivity values ranged between 16,050 and 50,000 gpd/ft*. Hydraulic conductivity values were calculated from toe transmissivity values for toe East Well Field. For W ells AX13-PW01 and AZ13-PW01, the hydraulic conductivity values ranged from 0.013 to 0.055 centuneters/second (cm/sec) and from 0.01 to 0.049 cm/sec, respectively. Using toe hydraulic conductivity values from toe 1990 study and the hydraulic gradient values determined from groundwater elevations measured in 1990 and assuming an effective porosity value for sand and gravel o f 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 TI3-MW01 and LI 8-MW01 in toe southwest portion o ftoe site. A groundwater flow velocity o f 3 ft/d was estimated between monitoring wells P06-MW01 and K14-MW01 in the western central portion o f the site. CempfetiOBof history data Draft 2rsv.doc Mar. 11,02 W lm ftigtoaDE 2 -5 JSO015054 EID620789 Main Plant and Landfills Washington Works Main Plant to the eastern portion o f the site, a groundwater flow velocity o f 2.5 ft/d was estimated for the site aquifer between monitoring wells AL10-MW01 and A009-MW 01. Groundwater seeps at the Riverbank Landfill were identified and sampled during the VI (DuPont 1992). An active French-Drain groundwater collection has been to operation at the Riverbank Landfill since 1991. The RFI verified that the collection system effectively captures water at the seep area. 2.3 W ater Quality 2.3.1 Surface W ater Quality Historical surtoce water C-8 concentrations me presented to Table 2.1A. Surface water sample locations are shown on Figure 2.2. Surface water C-8 concentrations were measured to 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/1 to 199 ug/1, while Outfall 002 C*8 concentrations overall have been much lower, ranging from 0.436 ug/1 to 8 5 4 ug/1. In general, Outfall C-8 concentrations have significantly declined to 2001. This is the result . o f installation o f a carbon adsorption treatment system in the fluropolymers process. The system is designed to remove a major percentage o f C-8 from the process wastewater. 2.3.2 Groundwater Quality Concentrations o f C*8 to groundwater sampled at the main plant have been evaluated since 1991 (Table 2.1B), 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 to January 2001. Two plant-wide groundwater sampling events were conducted as part o f 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 LandfiU/Digestion Ponds SWMUs. All plant wells sampled during the RFI were analyzed for C-8. A t the Riverbank LandfiU/Digestion Ponds area (to the western portion o f the Riverbank Landfill), C-8 was detected in groundwater and previous seep samples. Figures 2.6C and 2.6D d*pfrt the well locations and resulte for C-8, Measured concentrations ranged from <0,1 to 13,600 pg/L, Concentrations were below 40 pg/L to 28 o f the 37 wells sampled; to the other 9 weUs, maximum concentrations ranged from 380 to 13,600 pg/L. The highest concentrations were measured to monitoring wells P04-MW2 and RQ4-MW02, near the Digestion Ponds area. The RFI C-8 concentration values were utilized for contouring. Isoconcentration map were prepared and are presented in Figures 2.6A and 2.6B. CompSatton o f history dofa Draft 2rev.doo M ar. 11 ,02 WSmbBim.DE JSOQ15055 EID62079O Mam Plant arid Landfill Washington Works Main Plant 2,3,3 Drinking/Tap Water Quality Production W ell AM07-PW01 (historically known as well 336) supplies potable water to tire main p lan t 0 8 concentrations in drinking/tap waterhave been measured at four distribution points on the plant periodically since May 1999 (Table 2.1C). Concentrations ranged from 0,213 ug/1 to 0.589 ug/1. 0 8 concentrations detected .at three sampling points in the distribution system on October 11,2001 were 0.507,0.45, and 0.423 ug/1, 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 current and ftftuxe 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, W aste Incinerators, and Digestion Ponds) or covered and vegetated. Therefore, contact with these materials is considered to be an incomplete exposure pathway. A large portion o f 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 C8 impacted soils is considered to be an incomplete exposure pathway. Much o f the precipitation falling on site is routed toward drains and storm sewers, which ultimately discharge into the Ohio River, Precipitation falling on the riverbank slope either percolates into the soil or runs o ff 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 m d silt o f die Ohio River deposits that underlie topsoil and fill along the riverbank. Contact with impacted seep water is considered to be an incomplete exposure pathway due to the active french-drain groundwater collection system. Direct exposure to groundwater impacted by C-8 is also considered to be mi incomplete pathway because groundwater is located a t about 60 feet bgs. The only potential contact route for groundwater is via contact with w ater pumped from production wells. Water pumped from production wells is used for two purposes, supplying drinking water and providing industrial process water. Well AM07-PW01 is one o f three production wells that provides drinking water to the main plant. Other wells are A008-PW01 and AQ09-PW01, AM07-PW01 was sampled eight times. Measured concentrations o f C-8 in this well suggested that this exposure pathway is considered to be complete. However, average concentrations o f C-8 in drinking w ater at point o f use (which is a m ixture o fwater 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 (K16-PW01, V05-PW01, and L04-PW01). The maximum concentration o f 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 hlatory data Draft 2rev.tloe M ar. 1 1 ,0 2 2-7 JSO015056 EID620791 Maki Plan and Landfills 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 o f C-8 in process water at the point o f use (which is a mixture o f water from several production wells) will be lower than maximum concentrations detected in any angle well. Therefore, while this exposure pathway is complete, it is considered to be minimal. The RFJ ecological evaluation focused on identifying whether significant ecological 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 potentialecoldgical exposure medium within tre RFI study ama. Surface water contact with C-8 impacted soils or groundwater is not likely because the Waste Incinerators and Burning Ground SWMUs are covered with gravel, asphalt, or buildings mid do not provide ecological habitat Subsurface soil (greater than 2 feet) and groundwater are not exposure media o f concern for ecological receptora, and groundwater does not discharge to surface water at the site. 2.5 Data dap s The following data gaps were identified for the main plant: Additional monitoring weds are needed to filrther delineate C-8 concentrations in groundwater and to evaluate groundwater flow directions, particularly for groundwater flow in the bedrock below the unconfined alluvial aquifer. Continued refinement of the groundwater model for the main plant is required to reevaluate that groundwater capture by fire pumping wells is occurring at the site and that no off-site migration o f C-8 impacted groundwater is occurring. Surface water quality in the Ohio River should be evaluated. A separate work plan is currently being designed to address this Issue. Activities to fill the date gaps will be proposed and discussed in the work plan. 2.6 References DuPont 1990. Washington Works 1990Preliminary Hydrogeologie Assessment, Solid Waste & Geolgica] Engineering Department. ` 1992. Verification Investigation EJ. DuPont de Nemours Co. Washington Works April 1992. (Vol. 1). , 1999. RCRA Facility Investigation Report, DuPont Washington Works, June 30,1999. Corporate Remediation Group. Haskell Laboratory. 1991. Ammonium Perfluorooctanoate (FC-143). Compite!) of histoiy data Draft 2rov.doc Mar. 11,02 WSmlngten, P * CTSO015057 EID620792 Main Plan! and Landfills Washington Works Main Plant Schultz, R.A. 1984. Groundwater Hydrology o fthe Minor Tributary Basins o fthe Ohio River, W est Virginia Compilation til histoty data Draft 5ft>v.doc Mar. 11,02 Wilmington, DS JSO015O58 EID620793 Table 2.0 Monitoring Wei! Construction Data DuPont Washington Works Main Plant Washington, WV Monitoring Wells New ID Old ID Q04-MW02 Q05-MW01 P06-MW02 P08-MW01 NI3*MW0I M16-MW01 A008-PW01 AQ09-PW01 ATiO-PWOl V11-PW01 AXI3-PW0I AM07-PW01 " AZI3-PW01 L0APW0I U7-PW01 K18-PW01 K19-PW01 K16-PW01 J17-PW01 VO5-PW01 J08-MW01 Q07-MW01 " " Z07-MW01 Q1Q-MW01 TI3-MW0I .........U16-MW1 AQ09-MW01 L18-MW1 V09-MWO1 N4-MW01 P06-MWO1 ARO9-MW01 AX12-MW01 AGO7-MW01 AJ06-MW01 AO08-MW0I Y05-MW01 ACO5-MW0I AL10-MW01 Ron's MW-1 Ron's MW-2 Ron's MW-3 Ron's MW4 Ron's MTW-5 RorfsMW-6 331 332 333 334 335 336 337 GALLERY LK351) L2352) L3353) 14(354) L5355) RNNEY TW-1 (tw-28) TW-20 TW-21 (307) TW*22 TW-23 TW-24 TW-25 TW-26 TW-27 TW-3 (pW-3) TW-32 TW-33 TW-38 TW-39 TW-40 TW-41 W-46 TW-48 TW-5 TW-6 TW-61 TW-E4 TW-E5 TW-E6 TW-M1 Surface Total Elevation Depth (feet) (feet) 629.39 71 598.76 42 629.29 71 630.82" 75 625.87 70 627.14 70 632.91 1 95 634.36 96 634.37 633.49 97 9329 630,69 634,26 90 96 628.04 92 589.75 633.93 634.92 634.2 623.24 624.78 632 92 630.21 630.35 632,49 6314 632.69 638.23 632.89 635.82 628.5 594.48 630.63 635.27 635.23 632.87 635.09 MU 101.4 10X60 m ai 93.5 103.2? 636,02 631.16 635.22 631,61 101,16 101,61 Well Diameter (inches) 2 2 2 2 2 2 18 18 18 18 18 18 18 . 18 18 18 18 NA 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 4 6 4 Slot Size (Inches) Screen Length (feet) 10 10 10 5 5 10 20 20 20 19 13 20 20 NA 18 1 20 20 20 20 20 20 20 20 29 Elevation of Screen Interval (fee*) 566,0 - 556,0 567*0 - 557,0 567.0 - 557.0 559.0 - 554.0 560,0 - 555.0 565.0 - 555.0 558.7.538.7 533.8-533.8 553.5-533.3 553,7-536.7 m o - 543.0 555,0 - 535.0 555.0 - 535.0 542.0-541,0 555-533 550-530 550-530 550-530 550-539 550-530 550-530 550-530 550-530 Page 1 of2 JSO1550 EID62O704 fa b le 2.0 Monitoring Weil Construction Dala DuPont Washington Works Main Plant Washington, WV Monitorina W ells New ID ow n 1 Surface Elevation IQ7-MW01 K14-MW01 D8-MW01 F06-MW0 U03-MW01 U05-MW02 U05-MW01 L04-MWW AA04-MW01 AA5-MW01 AB07-MW02 AC7-MW02 AE11-MW0I . AL06-MW01 B13-MW01 G7-MW0J L06-MW01 M04-MW02 MO4-MW03 N04-MW02 N05-MW01 P04-MW02 P05-MW02 R04-MW02 S05-MW02 ....... 4-MW01 VO6-MW01 W5-MW01 Y14-MW01 Z06-MW2 Z07-MW01 Z09-MW01 TW-M2 TW-M3 TW-M4 TW-M5 TW-M6 TW-N2 TW-P12 TW-W1 WOO-57? 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 i 610.23 627.34 600.67 601.14 592.44 631.17 632.11 597.4 630.8 630.6 633.2 629,51 634.04 623.5 630.5 629.85 593.5 593.6 593.6 633.48 590.6 631.68 593.2 631.18 593.1 629.93 6325 629.93 640.1 629.64 630.7 Total Depth (feet) 97.34 62. i0 2 .ll 43 76 72 74 72 72 74 80 77 25 26 26 82 28 80 28 78 27 77 76 90 72 74 70 Well Slot .Screen Diameter Siro Length (inches) finche? [(fe e t) SSliP^ ! 20 4 . B i 4 * fe20 4 4V 6* 6 6 ' 20 2 IO io 2 IO 10 2 lo 10 2 10 10 2 10 10 2 io 10 2 10 10 2 io 10 2 10 io 2 10 10 2 10 10 2 10 10 2 10 io 2 10 IO 2 10 io 2 10 10 2 10 10 2 10 IO 2 10 10 2 IO io 2 10 10 2 10 10 2 10 10 2 10 10 Elevation of Screen Interval lfe e t>...... 550-530 SSO-530 550-530 564.4 - 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 - 552,85 578,3-568.5 577.6 - 567.6 577.6 - 567.6 561.48 - 551.48 572.6- S 561,68 - 551.68 575.2 - 565.2 563.18 - 553.18 576.1-566.1 562.93 - 552.93 56425 - 554.25 549.93 - 539.93 578.1 - 568.1 565.64 - 555.64 570.7 - 560.7 M16-MW01 N3-MW01 P08-MW01 O04-MEW02 TW-55 TW-54 TW-33 TW-50 627,14 625.87 629.29 598.76 Fledand Italics - approximate - Information taken off cross-section Bold -Taken from UFI WP Paga 2 of2 JS O 015060 B ID 620795 Table 2.1A Summary o f Analytical Results: C-8 In Surface Water Samples DuPont Washington Works Main Plant Washington WV OUTFALL002 OUTFALL003 RIVER BELOW SOS RIVER BELOW PAGES RUM e i KV25/Q1 0/10/01 7/11/01 6/14/01 5/31/01 4/11/01 3/21/01 2/14/01 10/25/01 9/19/01 8/30/01 7/11/01 5/31/01 4/11/01 3/21/01 2/14/01 6/14/01 6/14/01 ,v 2.8 0.113 0.558 0.594 -------------0-.-4-3-6----------- . 8.54 " 1.74 65.7 2.86 2.16 120 74 1.43 ; SOFT 199 .. " ' " ' ' 153 - 0.034 J 0,075 J --- J ~ estimated value (below laboratory quantitation limit) JSO15061 1 ID620796 ....... .... Table 2,1 B Summary of Analytical Results; C-8 in Groundwater DuPont Washington Works Main Plant Washington, WV S 3 jn p lo A A 04-M W 01 AA05-M W 01 2 3' -A asm . 11/12/98 11/12/98 (dup) ....... 2 /4 /9 9 11/11/98 " " 5 ,4 3 0 .1 0 .4 2 1.46 ft7 7 -- 2T.v AB07-M W C S 2 /4 /9 9 '-- "W iSH 0 .5 3 5 ..... 0.21 AC07-MW 02 2 /4 /9 9 " 11/16/98 0 .3 5 6 A E11-M W 01 2/2/99 11/1 98 0.69 L 0,41 A IQ 6-M W 01 2 /3 /9 9 11/16/98 .18B 0.1 ......... A M 07*FW 01 11/20/00 8/16/00 " 5/12/99 2 /3 /9 9 __ 0.24 0.071 J 0 .5 7 8 0.682 B " 11/18/98 " 8/19/98 e a rn 4 /2 /9 6 1.9 L ........ 4 ' _ _ _ " __ 0.79 ' "-- A06-PW 01 11/20/00 ' 11/20/00 {durt 0 .4 0 .2 8 8/15/co 0 ,1 6 7 5/12/99 0.307 6/19/98 1 6/2/97 ........ 0 .5 5 4 /2 /9 6 0 .5 2 ACKKWW01 10/11/61 5/12/99 6.496 1215 E13-MW 01 5/12/99 2 /2 /9 9 0 .8 8 2 FDfrM W OI 11/11/98 mm ... 11/11/98 2 0.35 L 0.1 G17-M W 01 5/12/99 2 /2 /9 9 2.47 2 J lT ~ 11/11/98 13 K16-PW 01 11/20/00 2 /9 /9 9 7 .5 18.2 W 4-PW Q 1 11/18/98 " TO T 4/HW1 0.46 L 0.202 3.99 11/20/00 mm 13.8 5.09 1 I 11/18/98 7.9 J 3.9 J L06-MW 01 L17-PW 01 mm 11/13/98 w iW " ' 4,91 870 2,31 4/11/01 1,58 9/14/00 ....................... 0 8 1 9 ....... ........ 6/3/99 1.63 2/9/99 11/18/98 mm 2 .7 8 oaa 18 5/29/97 7 .9 4/11/96 3 .7 ......... - .................... 1 2/16/04 2 JS O 015O 62 11D 620797 Table 2,1 B Summary of Analytical Results (con't.); C-8 in Groundwater DuPont W ashington Works Main Plant, Washington, WV M 0W 2 M 04-M W 03 M1B-MW01 M 04-M W CB N054UM/O1 M W -/UP M W -M G M ... M W -TW W ...... ...................M W B S M13MW 0t PO4-MW02 P0S-M W 02 P8-MW02 P08-M W 01 Q04-MW2 Q 03-M W 01 RO^MWCa VOSW OI T13-MWQ1 U 04-M W 01 U1M4W 01 S05-MW 02 V084/M KH W 0544W 01 Y ;I4-M W W Z06-MWC8 ZQ7-MW01 Z09.MW 01 B a ..i 5 iS ......... ... . .f u g * . . 2/7/99 17 11/12/98 05 mm 11/12/98 2 1 .1 .................... <0.1 2/ 3/99 3 ,6 6 1 11/10/98 0.88 1/2S/01 098 1/25/01 (due) 696 mm 329 11/12/98 380 2 /5 /9 9 815 lT /iS 3 a 13______ . 4 /1 8 /9 6 <0.4 4 /1 8 /9 8 0.09 m tm 0.86 4/2 /9 8 <0.1 2 /2 /9 9 11/11/98 <0.1 1/26/01 2/6/99 12600 13600 W Sm B300 2/5/99 434 11/19/98 ......... 1200 2/579 ' 414 .......... 11/13/98 31 43.4 11/19/98 ' mm 11/13/98 36 994 660 ...... 11/13/98............ 38 ~ ... 1/25/01 2 /6/99 11/12/98 7/11/01 4/11/01 11/20/00 13800 -- 1300 11.4 ......... ... ..... '" O S .."" 13.7 - 2/7 /9 9 2/7/99 (duo) _ 132^.4 ~ T liW 0.68 L 2 /3 /9 9 0.64 L 2/3/99 (dUd) 1.30 L 11/17/98 <0.1 R 2 /6 /0 9 11/12/98 4,2... . 1.8 5 /1 1 /0 0 ...... 5/20/99 6 /1 9 /9 8 4.7 ` 2 11 2 /5 /9 9 11/13/93 174 6!S : 2 /4/99 11/16/98 1.91 1.7 2 /8 /9 9 11/17/98 0.729 0.31 2 /2/99 11/10/98 4 .9 5 1, 12 ........... 2 /4 /9 9 0.003 11/10/98 4 .5 2 /4 /9 9 11/16/93 2.05 3 .0 2/6/99 ...... 2.74 11/17/98 <0.1 R JSO01S063 EXD620798 Table 2.1 B Summary of Analytical Results (con't): ' C'8 In Groundwater DuPont W ashington Works Main Plant, W ashington, WY " 1,1 RBLMW1 " RBLMW2 12/5)91 12/5/91 idup) 12/11/91 1 RBLMW3 11 K6LM W 4 RBLMW5 RBLMW8 W iM m " RBLMWB RBLMWB R0LMW 10 ~ RBLMW11 ------ --------------RBLMW12 ...................... BGMW2 BGMW3 m- u ...... BGMW5 ADPM W 1 ADPM W 2 ADPMW 3 .. ......... _ 12/11/91 12/5/91 12/10/91 11/21/91 11/21/91 11/21/91 (dUB) .......... 12/10/91 12/10/91 11/20/91 11/20/91 12/10/91 12/13/91 12/13/91 . 12/13/91 (dup) 12/11/91 12/6/91 ' ...... 12/6/91 12/6/91 R unusable data result (relative to QA/QC) j a estknated value (below laboratory quantification lim it) L = possible low bias result (relative to CWQC) B seom pounddeterteaiftQ cbhinit a Non-deteci a t stated laboratory method detection lim it ..... ........ --" 140 140 el 67 7100 0 1300 3300 4B 52 2.4 3.4 14 47 4.B 2 .3 4 3.6 55 7800 25 20000 ... _____ ..... . _____ ........ . ... ..... JS 0015064 EID620799 T ab le 2.1C Summary of ti8 Analytical Results; Drinking/Tap Water Samples DuPont Washington Works Main Plant Washington, WV ^ m :ieameBBieeiil&3s8R'. ILDS 1MAIN BUX3231 BLDG233 " BLDGS !5 #& ^ 0 ie irsHS 1(211/01 sm z. iS jB M W ' 0.SOTi 1 i 11 8/15/00 10/11/01 5/12/99 5/12/99(dup) 10/11/01 .. ;5/12/b ' 5/12/98 ..... *ttisaaf5^ ...... A4&--' 'TM 0i308/.;rt ft2B8." " ......~ ___-*o4m___-___ ... 0.213 --V JSOQ15065 EID620800 :] II ! 21 1F 1s 1 11 111 111 i 111111 35 S S 5 3 i ; ; i 33 SlSIlliililIHS 11111111111111111 O S ill lilliiilillliilil Main Plant and Landfills Local Landfill 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 die Ohio River In Washington, West Virginia, approximately seven miles southwest of Parkersburg, W est Virginia A water use and well survey is currently being conducted for the area within a 1-mile radius o f the landfill perimeter (Figure 3.1). The Local Landfill consists o f three separate closed cells located on the heavily wooded 250-acre site. The cells were operated from 1964 to the middle 1980s under W est Virginin/Nflrinnal Pollutant Discharge Elimination Systran (WVNPDES)Permit No, 0076538. The permit is currently undergoing renewal and is expected to be effective in January 2002. The permit requires monthly surface water sampling and semi-annual groundwater monitoring. Materials landfilled included scrap product, scrap metal, wood pallets and bins, and Powerhouse ash. Approximately 144 tons o f waste per year were disposed in the landfill, Powerhouse ash comprised about 70 percent o f the total waste. The specific source o f C- 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 o f the three cells, monitoring w ells, arid surface w ater sampling points. The cells have no com pacted or synthetic bottom linens. However, a hydrogeologie evaluation indicated that the natural soil present under the cell m aterials is composed o f reddish brown clay and weathered shale having a very low hydraulic conductivity o f about 5 X H T 7 cm/sec (DuPont, 1990) and ranges from 3.5 to 19.5 feet in thickness. 3 .2 E n viro n m en tal Setting 3,2.1 Geology The Local l andfill is situated in a hilly area with relief o f approximately 30 to 40 feet. The slopes appear to be a combination o f natural topography with terraced outcrops o f massive sandstone and siltstone underlying varying amounts o f soil cover and man-made landfill plateaus. The locations o f two cross-sections developed for the Local Landfill me 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 silty zones, and some pebbles and fragments o f sandstone in some locations, The clays are o f low plasticity and appear to be well compacted, often displaying a 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 round surface. Comptoilon o f btetwy data Draft 2rev.doc Mar. 11.02 WSmlncitCuOB a so o iB o e? EID620802 Main Plant and tandBIs Loca! Landfill The bedrock at the Local Landfill consists o f inter-bedded red and varicolored sandy or calcareous shale, and gray, green, and brown sandstone o f the Permian age Dunkard Group. The maximum thickness of the Dunkard Group in this region is 570 feet. The cross-sections show that the sandstone layers dip gently towards the north. Most of fee sandstone layers located in the upper portion o f fee stratigraphic section are lenticular and laterally discontinuous. Two laterally continuous sandstone layers are located in fee lower stratigraphic section. 3.2.2 Hydrology, Hydrogeology and Groundwater Flow Hydrology In general, infiltration o fprecipitation is limited due to fee very low hydraulic conductivity (5 x 10'7 cm/see) o f fee surficial days (where these clays exist) and the weathered bedrock (DuPont, 1992). In addition, infiltration o fprecipitation into fee cells is limited by approximately 2-feet o flow permeability soil and vegetative cover capping o ffee cells. Leachate from fee southern cell and fee eastern cell flows from fee seeps in fee steep valley walls to leachate collection ponds, Pond 1,2 and 3 (Figure 3.2b Ti-adiattt from these ponds is discharged into a pipeline and conveyed to the main plant where it passes through storm water Outfall no. 001 into fee Ohio River. Monitoring o f combined pond effluent conveyed in fee pipeline is conducted at Outlet 101. Hydrogeology Groundwater underlying the Local Landfill occurs in two zones. The discontinuous upper zone consists o f fee clays and underlying weathered bedrock and has a very low hydraulic conductivity (DuPont, 1992). The lower zone consists o f fee continuous and discontinuous sandstone layers having low permeability o f 1 x I0's cm/sec. The sandstone layers are separated by laterally continuous shale layers. Well yields from fee sandstone layers are very low, ranging from <0.5 gpm to 1.5 gpm (DuPont, 1992). The upper (and thicker) o f fee two laterally continuous sandstone layers located in fee lower zone at elevations between 710-740 feet above Mean Sea Level (Figures 3.4A and 3.4B) has been designated as the "underlying significant aquifer" and is currently monitored semiannually as required by fee permit. In 1989, eight monitoring wells were installed at the Local Landfill by Tetta Tech Richardson (LLMW-1 through 8). However, five o f these monitor wells (LLMW-1, -2, 3, -5, and -7 ) were closed in 1996 because they were screened in fee 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 fee significant underlying aquifer. Table 3.0 summarizes fee well construction data for the existing monitoring wells. Groundwater Flow Groundwater elevations have berm measured semiannually srnce 1994. Groundwater elevation contour maps for fee significant underlying aquifer have been prepared from this data as required by fee WVNFDBS Permit No. 0076538. Figures 3.5A through 3.5G present maps for 2001 through 1996 and 1994. The groundwater contours were CompSatton ofhlstotydata Draft 2rev.doc Mar. 11,02 Wilmington. OB 3-3 J S O O IS EID620803 Main Plant anti Landfills Local Landfill transferred from the original maps submitted for the permit to the updated Local Landfill base map. Evaluation o flimited groundwater elevation data for the closed wells (based on well ingtnUatinn information) indicates a downward vertical gradient between the upper discontinuous water bearing zone and the lower sandstone layers containing the underlying significant aquifer, hr additimi, C-8 present in the underlying significant aquifer provides further support for a downward vertical gradient. The groundwater contour maps for the underlying significant aquifer show that flow is from die south to the mirth towards the p lan t The sandstones o f die underlying significant aquifer outcrop in the valley walls where discharge may occur as seeps. However, groundwater may also flow downslope within the fractured rocks o fthe valley . walls and ultimately enter the alluvial terrace deposit on die main p lan t Groundwater discharging to seeps ultimately migrates to the plant through a number o fpathways. It can discharge downward to leachate collection ponds and pipes to the mam plant where it enters storm sewers and discharges to the Ohio River. Groundwater also can seep to small streams draining (he property to the north and flowing to the Quaternary alluvial terrace unconfined aquifer where pumping o f on-site active well fields controls groundwater flow. Groundwater flow in the alluvial aquifer, adjacent to the valley walls o f the Local Landfill, is towards the pumping wells located near and parallel to the Ohio River. The pumping o f these well fields also lowers the groundwater level to below river stage, inhering surface water from the river to flow into die alluvium towards the pumping wells. W ater from the pumping wells is used for non-contact cooling purposes and ultimately is discharged to the Ohio River, 3.3 W ater Q uality 3.3.1 Surface W ater Quality Table 3.1A presents the historical C-8 concentration data available for surface water. Figure 3.2 shows the surface water sampling locations, if the location currently exists. Samples from two outfalls, four outlets, rivo streams, id one leachate sampling location have been collected periodically since 1994. C-8 concentrations in the outfalls and outlets range from <0.2 ug/1 to 80 ug/1. Stream sample C-8 concentrations ranged from 4,12 ug/1 to 15 ug/1. The leachate sample, collected in the pipe from the leachate ponds, had a concentration o f 31 ug/1 (February 1994). For sample locations having more than two sampling events, the concentration o f C-8 is decreasing with time although it is difficult to accurately identity trends in samples with tile limited data se t The C-8 concentration at Outlet 101, located at the northeastern portion o f the side, have decreased from 54 ug/1 to 12 ug/1 over the course o f three sampling events. 3.3.2 Groundwater Quality Analysis o f 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 Compilation o f history data Orati Zrev.doc Mar. 11.02 W tlmin6Iiin.DE JSO015Q69 E D 620804 Main Plant and Landfills Local Landfill * . ,v ..\ . amount o f data makes it difficult to develop concentration eontopypaps. In addition, the monitoring wells are located at three separate areas (cells) o f foeTandfili; 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 MO range from non-detcctable'to 0.22 ug/1. The other two wells, LLMW-4 and -6, hdve the highest concentratipn|j|ngm g from 1.4 to 39 ug/1 and from 1.32 to 15 ug/1 respectively. Although there is lim iifd a ta , the data shows a distinct ' reduction ......... in C-8 concentra.tion over tim e for wells LLMV/;4, -6, and -9. 3,4 Site Conceptual Model The Local T,w tfill 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 foe toad entrances. However, a posted nature trail has been established on foe east side o f foe landfill property. The frail loops around foe eastern part o f foe landfill starting and finding near foe landfill's electrically operated gate. The nature frail is a marked trail and does not cross the cells. Access to the site from surrounding roads is possible but is discouraged due to foe heavily wooded nature o f foe property and foe hilly terrain. The three cells at foe Local Landfill are covered with a low permeabaity soil and vegetative cover. This cover prevents human and ecological receptors' exposure to foe landfilled materials and to the soils potentially impacted by foe landfill materials. However, these materials could potentially be exposed by extensive digging or rooting in foe soil by animals or unauthorized people. Therefore this pathway is considered to be potentially complete but minimal. An additional potentially complete exposure pathway exists if the soil and vegetative cap is eroded by precipitation. Permit WV0076538 requires that the landfill surface will be inspected quarterly for evidence o f cracking or erosion (which could allow surface water to enter foe solid waste deposit) and evidence o f settling o f solid waste (causing ponding o f surface water). Per Condition G -l 6 o f foe permit, a stormwater 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 foe cells. However, foe low permeability o f foe soil cover reduces the amount o f infiltration. If the precipitation infiltrates the soil cover, it will possibly encounter foe landfill materials and will continue downwards. It may be prevented from further downward migration by foe low permeability clays and weathered bedrock. However, if this water migrated farther downward, it should encounter foe sandstones and shale layers. Groundwater flowing through foe sandstone layers that outcrop in foe valley walls located above foe plant site's southern edge would be exposed at the surface in seeps, if seeps exist. The existence and location o f seeps at some places on the property have been observed, particularly those mentioned near foe leachate collection ponds. Much of foe site remains unexplored, ComptotkOOfhistorydrta Draft 2rev.doc M8T. 11,02 Wlmlngton. DE 3 -3 JS 0015070 EID620805 Mftirt W ant and Landfills Local Landfill therefore, complete evaluation o f 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. In this case the water would not encounter the fill materials at any point it time. This potential exposure pathway is considered incomplete. Contactwith groundwater impacted by C-8 is anotherpotential exposure route for current and future hnwum and ecological receptors. However, contact with groundwater under die landfill is limited, although, contact with leachate that has reached toe pound surface via seeps is possible in toe vicinity ofPond 1, near toe southern most cell. Ponds are open and accessible to limited number o fDuJPont employees. As stated previously, groundwater flowing through toe 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 o f the valley walls and discharges to the main plant alluvial terrace. Determining toe existence and location o f seeps on the property has not been completed therefore, this potential exposure pathway cannot be folly evaluated. 3.5 Data Gaps ^ The following d a ta g e s were identified for the Local Landfill: Identify toe locations o f seeps in toe valley walls and determine water qualify with respect to C-8 concentration. Q Determine the C-8 concentration in streams and other surface water bodies. Q Acquire additional geological data to refine toe Site Conceptual Model, Trustait additional monitoring wells to provide additional groundwater flow data and groundwater qualify data, Gather additional C-8 concentration data from monitoring wells for plume delineation. Activities to fill toe data gaps will be proposed and discussed in toe work plan. 3.6 References DuPont 1990. Washington Works 1990Preliminary Hydrogeohgic Assessment. Solid Waste St Geological Engineering Department. ______. 1992. Verification Investigation E J. DuPont de Nemours Co. Washington . Works April 1992. (V ol 1). com tflatton othistw y data Draft 2ww.doc Mar. 11,02 WSmtftgton, 0 8 3 -6 JSO0SO71 110620806 Table 3.0 Monitoring Weil Construction Data Local Landfill Washington, WV Monitoring Wells LLMW- 4 LLMW- 6 LLMW- 3 LLMW- 10 Surface Elevation (feet) 844.7 793.2 788.54 805.94 Total Depth (feet) 155 90 80 87 Well Slot Diameter Size {Inches} {Inches) 4 0.020 4 0.020 4 0.020 4 0.020 Screen Length (feet) 20 20 20 20 Elevation of Screen Interval (feet) 717.2-697.2 723.2-703.2 726.54*708.54 738.94-718.94 i E ID 620807 i wu ooHtonJ M Table 3.1A Summary of Analytical Results: C-8 in Surface Water Samples Local Landfill Washington, WV mmm ' (.p a CHATE OUTFALL 004 OUTFALL 005 OUTLET 001 OUTLET 002 " OUTLET 003 OUTLET 101 ` STREAM 1 STREAMS - 2/16/1384 0/27/2000 12/10/1999 6/3/1899 .... 6/2/1998 2 9 /1 9 8 7 4/2/1998 2/16/1934 9/27/2000 " 12/10/1999 6/3/1069 " 672/1908 5729/1997 .... 472/1606 2/16/1994 .... ,, ' ...... ' "" " ..... S/29Z1997 4/2/1096 S /29/1997, 4/2/1998 2 9 /1 9 9 7 ..... 4/2/1996 9/14/2000 6/3/1999 672/1098 2 9 /1 9 8 7 " * " 4/2/1906 0/14/2000 12/29/1999 6/2/1008 4/2/1996 ...... ..... .......... . " 04M 31 .j-S E B S S ______ 71 3.08 12 13 13 11 < iv i _____ ______ ....... .. ' 34 O 39 ... " 41 --------------------- -30 3 5 ........_ 6? 72 20 12 15 54 72 ____ ... ...... 10.7 15 14 ..... JS0015073 EID620808 Table 3.1B Summary of Analytical Results: C*8 In Groundwater Local Landfill Washington, WV r.?.. ' . m m - , " 1AMW-4 . LLMW-6 U.MW-9 ` U.MW-10 -jv.-'-.srflM -i-f-* ` 5/11/2000 5/10/1999 5/27/1998 4/11/1996 5/16/2001 ... 5/10/2000 5/19/1999 5/27/1968 4/1-1/1906 5/16/2001 5/10/2000 5/20/1999 5/27/1998 ... 4/11/1990 ... S/20/1999 508/1998 .. .... ' .... ` 10 ... 165 ______ 20 ....... 39 1.42 132 9 15 ... <0.029 ...0.0484 <0.1 0.14 0.15 022 ... . JS 001S 074 EID620809 Man Plani and Landlte Letart Landfill 4.0 l e t a r t LA N D F IL L | ; Introduction...-- -------.------------------------------------- ................~ Sm toonenttl Sertbtg.-----------........... .--------w --" ' ................... ... ' Water Q u ilit/-- ---- ---------........................................................... .Site Conceptual .. ........'7' Dt0*p>-- -- TM-- " -- -- ------**"------- -- --------- ---------------------- References.,..,.,.----- .................... ........--.... ........'.............. . . . . .. .. .. .. .. ..................................... . Table 4.0 Table 4.IA T itle 4.IB Tab)? Lstart Landfill Monitoring W ells CoStrtietlc Dais LetartLandfill Analytical Dala Tibie - Surface Water Letart Landfill Analytical Data Table - Groundwater H8>ne 4 .0 Figuic4.1 figure 4 2 Figure 4.3 Figure 4.4A figure 44B Figure 4.5A Figure 4 5B Figure 43C Figure 45D figure 4jB Figure 4.5F Figure 4.6A Figure 4.6B Figure 4.6C Figure 4 D Figure* Letart Landfill Location Map LetartLandfill I-fitifeRadass Map Letart Landfill M onitoring We!) and Surface Water Sample Locution Map Letart Landfill Cross Scctfos Location M ap Letart Landfill Cross Section A-A* Letart LandfillCross Settion B-B* Letart Landfill F-Zone Groundwater Elevation Map -November 2001 Letart Landfill F-Zonc Groundwater Elevation Map - January 2001 Letart Landfill F-Zone Groundwater Elevation Map - October 1999 Letart Landfill F-Zone Groondwaler Elevation Map - October 1998 Letart Landfill F-Zoftc Groundwater Elevation Map - December 1994 Letart Landfill F-Zono Groundwater Eleveson Map - December 1992 Letart 0 8 Concentration Map - July 2001 Letart 0 8 Concentration M ap-January 2000 Letart 0 8 Concentration M sp-July 1999 Letart0 8 Courentration Map - November 1991. .,, 4 -2 ....4 -2 ...4 -4 _.4*6 :.,,4-7 ,4-8 C om pte& n o f history d ata Drafl 2Krv.doc Mar. 1 1 ,0 2 Viffkntogton DE JSO 015075 EID620810 Main Rent and Landfills Letart Landfill 4.1 Introduction The Letart Landfill is locatedjust north o f the town of Letart in Mason County, w i t 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 covets approximately 17-acies o f a 205-acre parcel of l ^ d ^ by M o n t Washington Works. It was in operation fromthe early 1960s to 1995. The landfill was o n e ra te d id closed under West Virginia Solid Waste /National Pollutant Discharge Simulation SystemPermit No. WV 0076066. This permit requires quarterly groundwater monitoring, outfall and surface water monitoring and engineered cap maintenance. Figure 4 1 shows the landfill extent, orientation, topography, and monitoring weU locations. H ie landfill was constructed within a natural ravine mid has nocompacted or svnthetic bottom liners. However, a hydrogeologic evaluation indicated that the natural f S nresent under the landfill material is composed of highly plastic clay and silt having a permeability ofabout cm/see (DuPont, 1993). The soil thickness ra n p s from 4 to 14 feet, averaging about 8 feet in thickness, Letart Landfill received waste was from the Fluoropolymer manufacturing process at fee plant feat consisted primarily o f scrap product, scrap metel, wood pallets miscellaneous trash. Approximately 5,000,000 pounds o f w ^ e p r y e^w ere disposed in fee landfill. This waste is believed to be fee source o f C-8 in fee historical groundwater and surface water samples collected from on-site locations. . The Letart t andfill was permanently closed by installing an engineered multi-layer geosyttfeetic and soil cap (DuPont, 2001). Included in fee closure activities were fee Installation o f a leachate collection system, erosion and drainage c o n l measures and chain-link fencing. The cap construction was completed in April 2001. 4,2 Environmental Setting 4.2.1 oology Hus Letart Landfill is situated on a heavily disserted plateau consis^ . f V-shaned valleys. Residual soil covers most landfill areas. In general, fee soil at fee mte has been d e s c rib e d as residual in nature, consisting primarily of heavy clays derived from fee weathering o fbedrock. At most landfill areas, fee soil is less fean ten feet thick, wife a maximum thickness o f 20.5 feet. sandy or calcareous shale, mid gray, peen, and brown sanfetone o f feePemuan age Dunkard Group. The maximum thickness o f fee Dunkard Group m this repon is 570 S tT h e location of two cross-sections, A-A' and B~B%crossing the landfill areshown in Figure 4-3. The two raross-sections o f the underlying geology are shown on Figures 4.4A and 4.4B. Compilation OfNstary data Draft aov-doo MW. 11.02 WmlStan. DE jr s o 0 1 5 0 7 6 EID620811 Main Plant and Landfills Letart Landfill Geologic investigations conducted at the Letart Landfill identified six stratigraphic water bearing zones that were designated as Zone A through Zone F, with Zone A being the shallowest zone and Zone F the deepest These zones consist o f massive, very fine to fine grained crystalline sandstone with occasional shale lenses. Zones A through F are separated by locally continuous shale unite that are generally ten feet or greater in fidckness. Zones A through D/E are discontinuous. Zone F is the first laterally continuous zone aider the landfill. Zones A, C, D/E mid F outcrop on die valley sides and dong the Ohio River near the southern mid of the landfill. 4,2.2 Hydrology, Hydrogeology and Groundwater Flow Hydrology The Letart Tnndffll engineered cap system prevents surface water from contacting landfilled materials. Precipitation falling on the engineered cap system takes one o f two paths. It m ay infiltrate downward through the vegetated soil and encounter die impermeable geomembrane and then flow laterally downslope on top o f the geomembrane. Alternatively, precipitation may flow via overland flow on top o f the vegetative layer downslope. In either situation, this surface water does not contact the landfillRd materials and migrates downslope towards drainage ditches constructed in or adjacent to the cap system. Precipitation falling on the northwest side o f 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 o f the cap flow downslope and towards the south hr drainage ditches. Hydrogeology Hydraulic conductivity testing [i,e,, slug tests (Zone A) and borehole packer tests (Zones C, D/E and F)] o f tire bedrock zones indicates that these zones display low hydraulic conductivity (Tetia Tech Richardson, 1990). Zone A hydraulic conductivity is low, ranging from 10*4 ero/sec to less than JO'5cm/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*4 cm/sec to less than 1O'4cm/sec, Zone D/E hydraulic conductivities are also very low and range from 10"5cm/sec to 1CTcm/sec. Zone F has been designated the "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 o f the landfill- Most current groundwater monitoring is conducted in Zone F. The low hydraulic conductivity can be attributed to the very fine-pained nature o f the water-bearing unite, fit addition, many sandstone units in the region typically display effective porosity as low as 1percent. 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 die southeast (DuPont, 2000). These values are relatively low, 0.01 and 0.003 ft/day respectively. The low velocities calculated in the F zone indicate that groundwater flow beneath the landfill is very slow, attributable to the CompIMenofWstoiydata Draft2mv.doc Mar. 11,02 WIMnetorvDE............................................... ................. ................................ 4-3 T SO 015077 EID620812 Main Plant and LandRIis Letart Landfill low hydraulic conductivity present in the F zone and all the overlying.units as well- Low vertical hydraulic conductivities in the overlying shallow zones limit infiltration and recharge down to die F zone. The saturated thickness o f 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, a n d -Il). in many instances, the monitoring wells at the landfill cannot be sampled until 48 hows (or longer) after purging, when a sufficient quantity o f groundwater has recovered in the weU screen interval. Groundwater Row Thirteen monitoring wells have been installed at the Letart Landfill in the Zone A, C, D/B, and F sandstone units (Tetra Tech Richardson, 1989; 1990). ^ LMW-10 and LMW-11, were installed in October 2001.to provide additional data from Zone F to the north and south ofthe landfill. Table 4.0 lists the wells monitoring each zone and provides well construction information. Water level measurements an 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 the permit to the updated Letart Landfill base map. The location and limited number o f monitoring wells within Zones A, C and D/E prevents determination o f groundwater 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 underihe center ofthe indffll in a north-south direction. Groundwater east o f the divide flows southeast towards the Ohio River. Groundwater west ofthe divide flows towmds the west and southw est Groundwater elevation data, including the newly installed LMW -U, the most northern monitoring well, indicates a slight component o f northward groundwater.flow in Zone F in this area. Rapid decreases in the observed volume o f water discharging from the leachate collection system in 2001 indicate that groundwater flow under the landfill is being greatly reduced in response to the insolation ofthe engineered cap system, fa addition, this reduction ftyflratea that a new equilibrium state for groundwater flow has not yet been reached. Continued monitoring o f groundwater elevations o f Zones A through F is required to evaluate long-term changes in groundwater flow resulting from closure activities. 4.3 W ater Quality 4,3.1 Surface Water Quality Voluntary surface water sampling for C-8 has been performed periodically since 1991. This date is presented in Table 4.1A, The two locations sampled most frequently, the Upper and Lower ponds, no longer exist. During construction o f the engineered cap system, these ponds were de-watered and the sediments underlying the ponds were excavated and placed in low areas o f the landfill prior to the installation o fthe cap. Currently, only two surface water locations still exist (due to landfill cap construction) Compilationof hfctoty data Draft 2rev.doc Mar. 11. to Wilmington. DE ft- JS 0015078 EID620813 Main Plant and Landfill Letart Landfill and am being sampled. These locations include the leachate from the landfill [location 002(leachate basin)] and the stream located slightly east of the property line along Rt. 33. The locations o f these surface water-sampling points are shown in Figure 4.2. 4,3.2 Groundwater Quality Groundwater from the monitoring wells has also been voluntarily sampled and analyzed for C-8 periodically since 1991. However, sampling did not take place on an annual . has?s unfil 1996 and quarterly sampling began the second half o f 1999, when C-8 was added to the permit 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 o f the groundwater data does not show any obvious overall concentration trends (Table 4.1B). For wells having data from 1991 through 2001, it appears t o t the concentrations measured in 1991 were the low est From 1991, the concentrations hi all wells increased. Currently, concentrations are now decreasing again in the most recent sampling events. However, identifying trends in the data is ' complicated by t o t o t t o t three different analytical laboratories have been contracted to perform t o analyses between 1991 and 2001. In addition, t o effects o f t o installation o f t o engineered cap system (preventing further surface water infiltration) may or may not he observable in t o limited recent data. For the most recent sampling event and analysis (October 2001), the sampling and analytical procedures, and t o analytical mstrumentation used were modified to gam better accuracy in t o C-8 analytical results. These modified procedures w ill be utilized for all future analysis o f groundwater samples tor C*8. Continued monitoring o f C-8 concentrations In groundwater is required to accurately evaluate t o long-term trends in groundwater quality. If it is assumed t o t impacted groundwater flows from Zone A downward to Zone F and ultimately migrates to t o Ohio River, t o C-8 historical mean for LMW-5B (Table 4. IB) cambe used along with t o estimated groundwater flux to calculate the C-8 loading to t o river. The following assumptions were made in torn calculation. Q The saturated thickness is 25 ft at LMW-5B. This is higher than t o most recent groundwater elevation measurement and therefore, is a conservative value, Q The length o f t o aquifer discharging to t o Ohio River is 1000 ft based on the geologic cross-sections. Q The historical mean value o f 855 ug/1 for LMW-5B, a downgradient well, represents t o concentration o f C-8 in t o aquifer. O The velocity of groundwater in t o aquifer is 0,01 ft/day. Groundwater average linear velocities for t o F zone are calculated to be 0.01 fi/day from t o north to t o southwest and 0.003 ft/day from t o north to t o southeast (DuPont, 2000). Using there assumptions, t o calculation for loading to t o Ohio River is shown below; CompasSon rfh ia w y dala b ra * Zrw .itoc Mar. 1 1 ,0 2 Wilmington, DB 4 -5 JSO15079 EID620814 M n Plant and landfills Letart Landfill A = Area ~ 1000 ft length x 25 ft saturated thickness for Zone F - 25,000 ft* V - Velocity = 0.01 ft/day (estimated) Q - fiux = A x V - (25,000 ft2) x (0,01 ft/day) x (7.48 gal/ft3) x (365 day/yr.) = 682,550 gal/yr Mass - (855 ug/1) x (ig/109ug) x (lkg/1000g) x ( l lb/2.205 kg) x (4.7851/gal) . ~ 1,47x1o-9 lb/gal x 682,550 galtyr = 1 xKT3 Ib/yr ttefirnatwl ptmnal loading to the Ohio River is veiy low based on die calculated mass and should result in a very low 0*8 concentration in the Ohio River, The low calculated mass Is reasonable given die 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 o r incomplete. The Letart Landfill closure was completed in April 2001 with the installation o f an engineered cap system. The engineered cap system prevents human and ecological contact with tre 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 pathway. Exposure o f landfilled material because o f erosion of the engineered cap system due to storm runoffis also a potential human and ecological exposure pathway. However, cap system drainage controls were designed to convey the runofffrom the landfill cap to a discharge point and to eliminate tihe potential for runoff-related erosion o f the cap. In addition, the landfill cap is required to he inspected at least quarterly (permit requirement C.12.A) for evidence o f erosion as part o fthe site Storm Water Pollution Prevention Plan. Therefore, this potential exposure pathway is also a potentially complete hut 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 discharged at the southern edge o f the landfill. Because this surface water does not contact tire 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 fins impacted groundwater presents a possible human and ecological exposure pathway due to groundwater flow patterns. Groundwater flow under tire landfill has shown that prior to the installation o f the engineered cap, surface water impinging on the landfill Complanen cfH sM y data Draft Zrev-dcp MW. 11.02 W IM ngton.D E JSO015O80 EID620815 Main Plonl and landfills 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. Groundwater under the engineered cap migrates to the leachate collection system. Discharge from the leachate collection system is piped to an outfall [002(leaehate basin)] where it enters a small, shallow, wet weather stream that flows approximately400 feet before it discharges to the Ohio River. Contact with leachate is a potential pathway exposure route for current and, future human and receptors, however, this pathway is considered complete but limited due to the restricted access to the area. , Zones B/E and F occur at elevations lower than the leachate collection system. Groundwater 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 walls. However, in general, groundwater flows downslope within the shallow soil, colluvium, and fractured rocks o f 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 o f seeps on the slopes adjacent to the landfill or along the Ohio River. Therefore, evaluation o f this potential pathway exposure route for current and future human and ecological receptors is not possible at this time. , Groundwater that flows to the west from Zone F is likely to discharge to nearby valley ffrpmag systems and to ultimately migrate to the Ohio River. Again, groundwater flows downslope within the fractured rocks o f the valley walls and would only be exposed at the surface if seeps ex ist Currently, there is no data available on the existence or location o f seeps in the valleys south o f the landfill. Therefore, evaluation o f this potential pathway exposure route for current mid ftiture human and ecological receptors is not possible at this time. 4.5 Data Gaps The following data gaps were identified for the Letart Landfill: Identify the locations o f seeps in the valley walls, particularly in the steep valley wall along the Ohio River, and determine water quality with respect to C-8 concentration. Determine the C-8 concentration in the Ohio River. a Determine the C-8 concentration in streams and other surface water bodies. Q Acquire additional geological data to refine the Site Conceptual Model. Install additional monitor wells to provide additional groundwater flow data and groundwater quality data. 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. CompItaUcfiGfhfatoty data Draft 2i,dqc Mar. 11.02 4-7 JS O O li E ID S 20816 Main Rant and Landfills Letart Landfill 4.6 References D uPont 1993. Letart Landfill Hydrogeoiogic Evaluation, July 1993. Corporate Remediation Group. . 2000. Letart Landfill Groundwater Protection Pian SW/NPDES Permit No, WV0076066, January 7,2000. Corporate Remediation Group. _ 2001. Certification Report Letart Landfill Cap Construction, June 2001. Corporate Remediation Group. Tetra Tech Richardson. 1989. Monitoring Well Installation Program, October 1989. ______. 1990. Monitoring Well Installation Program at LetartLandfill-Sum m ary Report, August 1990. CompteUon of htetory data Draft 2w.doo M w.11,02 WBmlngton.ee JSOQ1S082 EID6208X7 JS O 0150B 3 EXD620818 Table 4.1A Summary o f Analytical R e s u lt s : C-8 In Surface W ater Samples Letart Landfill Letart, W V a s s a i . aeS tfe a -- -.i ; 002(LEACHAT BASIN) 7m e m 4 /3 /2 0 0 0 1/14/2000 10/21/1999 " LEACHATE 11/27/2001 " .... 7/20/01 ---------7 /2 5 /2 0 0 0 7 /2 0 /1 9 9 9 ^ ' LOWER POND 1/14/2000 " 4/3/2000 10/21/1999 7/19/1999 ~ 5/28/1998 ....... 7/23/1997 ~ -- 4717/1996 9/20/1994 3/15/1994 12/27/1991" ' -- 11/22/1991 .... 4/28/1991 3/22/1991 ------- ------------------------- ..." ^ N SPRING FLOW KT 33 STREAM STREAM MM RD T SW SPRING FLOW ... ............ '~ UPPER POND 1/18/1991 9 /1 2 /1 9 9 2 3/12/1992 7 /2 0 0 0 0 1 7/31/2000 7 /2 0 /1 9 9 9 7/23/1997 4 /1 7 /1 9 9 8 .... 3/15/1994 9/20/1994 3/12/1992 7/19/1999 5/28/1998 7/23/1997 4/17/1998 3/16/1994 12/27/1991 11/22/1991 4/26/1991 3/22/1991 2/8/1991 1/18/1991 r .. .... " J' u " .... 1350 1900 920 3240 .. _ ______ 159 50 1030 126 ` ?sao 1190 liiio 1600 1900 2200 730 flo o 1660 670 3^40 1200 ..... _ .... -- .. .. _____ ........ 63 0.573 22T 2 1.8 0 . 1 .... ... 480 <200 2100 4400 4100 790 930 500 2300 2900 .... ....... .....- ______ JS 015084 EID620819 Table 4.1 B Summary of Analytical Results: C 8 In Groundwater Letart Landfill Letart, WV mittayr: s&tnrsr~ -- uBZSr---------" LMW-4 1,1 LMW-5A 7/19/1999 11/22/1991 3/22/1991 4 /3 /2 0 0 0 1/14/2000 11/22/1991 3/28/1991 11/22/1991 3/22/1991 s^sss.'Sfc'K f t 6oa 350 ...... 380 272 172 830 690 0.8 1J8 ... _ J S 0015085 EID620820 Table 4.1 B Summary of Analytical Results (Con't): C-8 In Groundwater Letart Landfill Letart, WV <;c.:31sis I S S H K D a / '; . p l m w -3 11/22/1091 ..... 1000 3/22/1991 IM W -1 UVtW-7 .... LMW*a sar 7/ 19/2001 .... 1/31/2001 ' 10/4/2001 7 /2 4 /2 0 0 0 4 /3 0 0 0 0 1/13/2000 ....... 1001/1899 7 0 0 /1 9 9 9 " 8/28/199 " 7/23/1997 4/17/1996 11/22/1991 3 0 2 /1 9 9 1 .... 7 /2 0 0 0 0 1 ` 1/31/2001 10/4/2000 `"f B M W 4 /3 0 0 0 0 1/13/2000 10/20/1999 7/20/1999 5/28/1998 7 0 3 /1 9 9 7 4/17/1999 11/22/1991 7/19/2001 1 /3 0 0 0 0 1 10/4/2000 ..... 7 0 4 0 0 0 0 4 /3 0 0 0 0 1 /1 3 0 0 0 0 1 0 0 0 /1 9 9 9 7/20/1999 5 0 8 /1 0 9 8 7 0 3 /1 0 9 7 4/17/1996 11/22/1991 " ' 6100 9190 .... . . I B S ........................... 8990 13600 17400 ......... 12600 6920 ` 24000 S100 1700 ' ' 68 1 60 242 .......... 249 ___ m 158 "" 211 219 "" 930 7 8 .3 260 - ....... 53 15 ai ........ 1120 2650 2300 2160 2180 2100 3260 1790 2700 2000 2200 280 JS0015086 EID620821 PPfflf Main Plant and tan d fils Pry Run Landfill 5.0 DRY RUN LANDFILL Introduction.TM,,,---- w as? {unity------- - Site Conceptual M odel-TM -- --------- -- TM_----- -- ------ - D tU U a p ,-^ ------- -- ----------------- ------------- - R eftstnett......--* Table 5,0 Table 5,1A Table 5.10 Tables DryRun Landfill Monitoring WellsConstruction Data DtyRim LandfillAnalytical DataT ablet-Suffice Water DryRun LandfillAnalytical DaleTablet-tkoundw tter __ ,, - ___ _____..,..5-2 ............ .. ..............5-4 .............. 5-5 _______ 58 r^ Figure 5.0 Figure!! Figure 5.2 Figure! 5 Figure 5-4A Figure 5.4B Figure 5-5A Figure 5 4B Figure 5.5C Figure 55D Figure 5.5B Figure !$A Figure 5.6B Figure5.6C Figure 5,$D Figure3,6E Figured? DfyRim Landfill Location Map Dry Run U tidfin Ita lic RadiusM*p DryRunLandfill Monitoring Well and Surface WaterSampleLocation Map DryRunLandfill Cross Section Locatieri Map . DryRim Lrmdfill Cioss Section A-A' DryRim Landfill Cross SectionB-B' Dry Run Landfill GroundwaterElevation MapOetobtf 2001 DryRim Landfill Groundwaternievalim Map- October 1999 Dry Rim landfill Groundwater Elcyniioo Map, October 1998 DryRun Landfill GroundwaterElevation Map-October 1993 DryRim landfill GroundwaterElevation M ap- April 1992 I>iyRrmC-8 Concentration Map BedrockW ells-July2000 Dry Run C 8 CuncaJB*tiffl Map Bedtoek Well, July 1999 Dry Run 0 8 CoawWrationMsp Bedrock Welt*-July 1997 Dry Ron C 8 Concentration Map Overburden Weill - July 20 Dry RTM 0 8 Concentration Mtp Overburden Welli - July 1999 DryRun 0 8 CtmeeollaScioMep Overburden Wells - May 1998 temptation of Itbksy data DraftSPV.doc Mar, 11,02 WiWngtem,DE i JSO015087 EID620822 Main Plant awtlandHts Pry Run Landfill 5.1 Introduction The P ry Run Landfill Is located west o f the town o f Lubeck, m Wood County, W estVhgim a (Figure 5.0) and is about eight miles southwest of die Washington Works m sm plant and the Local Landfill. A water use and well survey search is being completed for the area within a 1-mile radius from the Dry RunLandfill perimeter (Figure 5.1). ' The Dry Run Landfill covers approximately 17-acres o f a 535-aere parcel o f land owned by DuPont. The landfill began operation in 1986 and is still active at present. The d f ill is operated under W est Virginia Solid Waste /National Pollutant Discharge Elimination System Permit No.WV 0076244. This permit requires quarterly groundwater momtoringandmouthly outfall'surface'water'monitoring. Figure 5.2 shows the location o f the landfill, monitoring wells and surface water sampling points. The landfill was constructed within the drainage basm ofD ry Rim, a tributary o f the North Fork o f Lee Creek, which is a tributary 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 o f d ay and weathered shale. The Dry Run Landfill receives waste from the main plant consisting o fnon-hazardous waste including scrap product, scrap metal, wood pallets, fly ash and bins, and miscellaneous trash. Approximately 50,000,000 p o u n d so fw e ep er j w j ^ b w n disposed in the landfill. Currently, the C-8 source is believed to be Ae dudges from the closure o f the main plant anaerobic digestion ponds that were landfified at DryRun m 1988 The Dry Run Landfill remaining capacity calculations for 2001 show 4,4 years ot remaining life on the existing cell based on a 128,000 ydVyr net fill volume consumption (DuPont 2000). 5.2 Environmental Setting 5.2.1 Geology The Dry Run Landfill is situated on a heavily dissected plateau consisting o f several steep V-shaped valleys. Residual soil covers most landfill areas. In general, the soil at the site hasbeen described as residual in nature, consisting primarily of heavy clays derived from , the weathering o f shale. A geotechnical investigation for the Dry Ron Landfill was completed by DuPontj.1996). The investigation consisted o f advancing soil test borings, test pits, laboratory testing of soil physical properties, stability analyses, and settlement analyses. DuPont (1996) d e to Jn c d t i e natural residual soil underlying the landfilled matenals consisted o f stiff to very hard silty clay and clayey silt with occasional reck fragments and a trace o f sand. The thickness o f this natural soil ranged from 12 to 28 feet in the test borings within the area. A 1989 monitoring well installation program, prepared by Teira Tech Richardson Inc., indicated similar silty clay and weathered shale overburden. Four CorapJattoncfhlstwy data Draft Zrev.doo Mar. 11,02 WiMnatauDi JSO 015088 EID620823 MainPlant and landBta_______________________ ____ Dry Run Landfill -- ------ ------- ------ ---- ----------- 1------ overburden wells (DRMW 12A, 12B, 13A, 6A) were installed to depths ranging ftom 11 to 17 feet. The underlying bedrock at the Dry Run Landfill consists o f inter-bedded red and varicolored sandy or calcareous shale, and gray, green, and brown sandstone o f the Permian age Punkard Group (Tetra Tech Richardson, 1989). The maximum thickness o f the Punkard Group in this region is 570 fe et The location o f two cross-sections, A-A mid B -B \ crossing the landfill mid downgradient o f the landfill are shown m Figure 5.3. The two cross-sections are shown in Figures 5.4A and 5.4B, There are only a limited number o f deep monitoring wells around and upgradient flora toe landfill (DRMW-14). Dashed geologic contact lines were drawn on cross-section A A ' (Figure 5.4A) because there is not sufficient data to confidently extrapolate between DRMW-14, the upgradient well, mid DRMW-13, the downgradient weM. More geological data is available (DRMW-6, -11, -12, and-13) and was used in d ev e lo p in g ^ downgradient cross-section, B-B' (Figure 5.4B) with more confidence. Cross-section BB* supports the interpretations made in cross-section A-A` o f rather flat lying sttatigraphie units o f 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 consisting o f several steep V-shaped valleys. Dry Run drains the valley in which the landfill is located. Many small tributaries discharge to rn the nearby valleys into Dry Run before it joins up with the North Fork o f Lee Creek. Potesta & Associates, Inc. (1989) completed a hydrologic and hydraulic analysis o f 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 flow capacity at 481 cubic feet per second (that is greater than the 100-year 24hour stortn). Potesta (1989) also evaluated the 24-hour precipitation amount that would result in M l flow conditions at the location where file capacity was estimated. Potesta determined that precipitation values between 5.25-5.99 inches in 24 hours would result m full flow. The installation ofa leachate collection system at the Dry Run Landfill encompassing the Inactive lower half o fthe landfill was completed by Potesta & Associates Inc. m 1999. Peufjiat from the landfill discharges into a leachate collection sump located northwest o f the landfill (Figure 5.2) through perforated pipes buried at the low edge o f the fiU area. The leachate is pumped from the collection sump to a 50,Q00gallon collection tank located at the top o f 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 Groundwater is found in the overburden and the underlying bedrock aquifer. The bedrock aquifer is considered the underlying significant aquifer for NPDES permit required groundwater monitoring. A total o f 15 monitoring wells have been installed at Dry Run to monitor the overburden and bedrock aquifers. At ibis time, four overburden Compilation of history io ta Draft /.doc Mar. 11,02 Wlmlngton. DE J S O 0L S 089 EID620824 Main Plant and landBte Dry Run Landfill wells (DRMW-6A, -12A, -12B, and 13A), and four bedrock ^ ( 0 1 ^ ^ 1 3 , -14, an d -IS ) still exist. The other seven weUs were abandoned in 1999 by Poterta& Associates, Inc. as required by the perm it because they were not being utilized tor m L o rin g CPotesti 1999). TaWe 5.0 p v id th. well coaattucW . *> for existing monitoring wells. Groundwater Flow . Water levels measured in November 2001 indS^tedoverburden encountered between 4 and 6 feet below ground surface. A i^ o u # 3 of 4 wells completed in the overburden monitor the same hydrogeologre unit, well DRMW-6A ^ completed at a relatively lighee mme, vddeh la dmcmdmiom, at lo w lopojtapbc am . No groundwater How maps were prepared lo r the shadow war encountered m the overburden section. Annual groundwater elevation maps for the underlying significant acgdfei-wereavail;We for the years 1992-1994, and 1998-2001. These maps are presented in Figures 5.5A through 5.5G. The groundwater contours were tren sto ed from the submitted for the permit to the updated Dry Run Landfill base map. T ^ maps drew that The gr,,ounwdiwraa.ter groundwater in the bhedrock aqauifer flows from the elevations measured for nested wells ^souutotheeaasst towwaareds C D R M W -l^-lM .~tahnednoirmthwi, aens d 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 o f the landfill. 5,3 W ater Quality 5.3.1 Surface W ater Quality Historical surface water 0 8 concentrations are presented in Table 5.1A for s k w l m g points. Sampling location for surface water sampling points still m existence can be found on Figure 5.2. Surface water samples have been collected periodically from these locations since 1996 and have been collected consistently for t e e locations (DRUachate, Outlet 001 and at the property boundary) since l^gg. Tbe conoentiation of C-8 in the leachate samples have been decreasing over tune (from 62 n^ w j a 2 1 A ug/1) while concentration from the other locations are variable and do not indicate a clear trend (Table 5.1A). 5.3.2 Groundwater Quality Historical groundwater sampling began in 1996. For wells that currently exist, sampling continues (DRMW-6 was abandoned in 1999; Potesta, 1999). C o n c e n tra tio n were . contoured for some o f 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 m Figure 5.6B was plotted but not contoured due to the data spread. Thedatafor DRMW12-B and DRMW13-A for July 1999 appears anomalous compared to m eother data for these two wells. The contour maps show that the highest concentration o f 0 8 exists m monitoring wells 13 and 13A, bedrock and overburden wells, respectively. Compilation of Wstwy data Draft 2rav.doc Maf. 11,02 WImlnston, DE 5 -4 JSOOISO&O 110620825 Msin Plant Swl Landfills Dry Run Landfill These two wells arc located downgradient from the central axis o f the landfill. For the ^ n t s fbrm ost o f the other wells, both o v e rb u rd e n ^ k o d c . the C-S concentration has been less than 1 ugrt. The C-8 concentraoon or e sampling event in DRMW-14 was W gherthan other values groundwater flowing from the landfill toward die DRMW-14 w dh , $.4 Site Conceptual Model The Dry Run site conceptual model describes the potential exposure routes for current S K X g i c a l receptors. Potential exposure routes were evaluated and classified as complete or incomplete. ^ Adcess to die Dry Run Landfill by is controlled by electronic gates on the major roads m d locked gatefon smaller roads, to addition, because the landfiU is active, there is a sew of w o t o on the landfdlm ea during normal working bourn. The J d y activity discourages trespassers on the site. Therefore, direct contact with landfilled materials is a complete but minimal exposure route, limited to the workers in active . landfill. Direct contact with landfill materials in the toaenye, lower halfo f the to d fill is incomplete due to toe leachate collection system 's geotextile andgeomembranecoyer. Contact with leachate at the landfill (or at the main plant where the lea.shatem is cim idered a potentially complete but limited exposure route for the landfill and plant workers and samplers. . Currently, toe inactive lower halfo f the landfill is ^ v e r ^ b y geotextiles and eeomembranes o f toe leachate collection system. Therefore, precipitation falling on this portion o f toe landfill does not come in contact with the landfilled materials. This precipitation flows downslope via overland flow and disetongesm tostonn water drainage ditches and eventually reaches Dry Run Creek. Therefore, this potential exposure route is considered incomplete. Precipitation falling in the upper halfo f the landfill may also flow via o v e r flow down slope to toe drainage ditches, again, an incomplete exposure route. Alternatively, this precipitation may infiltrate and come in contact with the laodfflle.1 J* . migrates downgradient. However, this impacted water flowing withm the landfill may be collected by theleachate collection system. If this impacted water n u ta te s downward through the landfilled materials, it may eventually come m com actw thtoeim derlym g shalesand sandstone of toe bedrock and migrate downgradient within the bedrock aquifer. Contact with impacted groundwater is a potentially complete exposure route E u g h currently, not enough hydrogeologic data exists to accurately evaluate this exposure pathway. Plans are underway for toe expansion o f toe leachate collection system and for a final cap/cover system. These activities in the future will further reduce precipitation infiltrating and contacting landfilled materials. Completiono f history d a ft Draft 2rev.tK>c Mar. 11,02 WUrmlnoton. m JS O 015091 EID620826 Main Plant and Lftndlilla -- ------ -- .... Dry Run Landfill -------- ---------- ------" ' " " ~ 5.5 Data Gaps The following data gaps were identified for the Dry Run landfdh Q identify the locations o f seeps in the valley walls and determine water quality with respect to C*8 concentration. p Determine the C-8 concentration in streams and other surface water bodies. . Acquire additional geological data to more accurately develop the Site Conceptual Model. p Install a c tio n a l monitor wells to provide additional groundwater flow data and groundwater quality data. Gather additional C-8 concentration data from monitoring wells for plume delineation. Activities to fill the data gaps will be proposed mid discussed in the work plan. 5.6 References DuPont. 1996. Report o f Geotechnical Investigation Dry Run Landfill,^Washington . Works Main Plant, Parkersburg, WV. Geotechnical Group, Crvd Engineering Systems. DuPont Engineering. April 25; 1996. . 2000. 2000 Dry Run Landfill Operational Report. Submitted January 26,2001. Potest & Associates, Inc. 1989. Hydrologic and Hydraulic Analysis o fDry Run, Area No. I . October 9,1989. Letter from P . Mark Kiser to Dan Weber. 1999 Monitoring Wells MW-1. MW-1A, MW-4, MW-4A, MW-6 MW-10. MW10 Abandonment Report, Dry Run Landfill, DuPont Washington Works. March 1999. T rtta Tech Richardson. 1989. Monitoring Well Installation Program, October 1989. CompSaaonorhl3tydrtaftaS2,vltoc Mar-11-02 wummgionuts JS O O 15O02 1ID 620827 SXD620828 t u h* Ut o to u T able 5.0 Monitoring Wett Construction Data Dry Run Landfill Lubeck, WV Monitoring Wi!s TM DRMVV- 14 DRMW- 13 DRMW- 13A DRMW- 12 DRMW- 12A 1 ' DRMW* 12B 11, DDRRM|pWj .- SA 15 " Surface ovation {feet) 938.14 720.6 720.3 730.5 730.3 730.5 ! 744.93 I 73.S7 Total Depth (feet) 250 35 11 35 17 15 12.2 45 W ei Slot Diameter Size (Indies) (inches) ^ M " 4 0.010 4 0.010 4 0.010 4 0.010 4 0.010 2 2 0.010 Screen Elevation of Length Screen interval ... - NA 15 (feet) _ na 700.6-685.6.. 5 714.3-709.3 15 710.5-595*5 5 {i'-Jk*/"\5.3 10 725.5-715.5 20 Table 5.1A Summary of Analytical Results: C-8 in Surface W ater Samples Dry Run Landfill Lubeck, WV .... ....... O O W N S tl^ DRLEACHATE O UTLET001 PROPERTY BOUNDARY ____ ... 10/3/2000 12/28/1999 5 /1 0 /1 9 9 8 7 /2 2 /1 9 9 7 10/3/2000 12/29/1999 57 1 9 /1 9 4 /9 /1 9 9 8 18/3/2000 "-- 7 /1 4 /1 9 9 8 '" " `12/29/1999 " STREAM SAMPLING P O lM rn ' STREAM. SAMPLING POINT#2 ...12/29/1999 5 /1 9 /1 3 9 8 1 0 /3 /2 0 0 0 12/29/1999 5/19/1998 a -x m a .: M a i b , -.'Sis-,/ J"u~ ]..... 9R 2 7 .4 94 58 _ 82 66 ...... -11--------------- ------------ 96 9 .9 0 .8 8 ... 39 J 0.5 4 - ..... - " i "TM ... .... ~ 87 4 .6 ... JSO015094 EID620829 Table 5,1B Summary o f Analytical Results: C-8 In Groundwater Dry Run Landfill Lubeck, VW 1' * ' ..... ' aam m m PRMW -12 DRMW -12A "B RM W -12B DRM W -13 DRMW -13A DRMW -14 DRMW -15 D RM W -6 " BRMW-6A * *!& 7 /1 9 /2 0 0 0 # fe - 0 .1 6 t i i i h m ~ ................. .... ' 0.134 5/26/1998 < 0 .1 0 7/22/1997 "" 1 0 .1 " 4/10/1996 " <0.1 ...7 /1 9 /2 0 0 0 ... 7/21/1999 5 /2 6 /1 9 8 8 ....... ..... 0.128 0.081 J < 0 .1 0 7/22/1997 4 /1 0 /1 9 9 6 ....... <0.1 <0.1 .............. ......... 7/20/2000 7 /2 1 /1 9 9 9 " ..... 6/16/1998 -------- N O IO .M 9 )-........ ........ .... 5.4 <0.1 7 /2 0 /2 0 0 0 ...... 7/21/1999 ...... 5/20/1998 ~ r "..... 9 .8 3B 9.2 7/22/1907 ' 7.... . *" " "7/20/2000 9.9 7 /2 1 /1 9 9 9 5/26/199B ... 0 .070J 8.7 ........... ......... 7/22/1907 "18 4 /1 0 /1 9 9 6 ...........a ,2 ....... ...................... 11 7 /2 0 /2 0 0 0 0.115 7 /2 1 /1 9 9 9 6 /1 6 /1 0 9 8 7 /2 1 /1 9 9 7 .......................... 2 .5 <0.1 ' r <0.1 . 4 /1 0 /1 9 9 0 7 /2 0 /2 0 0 0 7 /2 1 /1 9 9 9 7 /2 2 /1 9 9 7 4 /1 0 /1 9 9 0 ........... ............... """ <0.1 0.763 osm i 0.97 .... 7/20/2000 ' 7/21/1990 " " ........... 0 5 1 2 0.096 ~ 5/26/1998 7/22/1897 4 /1 0 /1 9 9 6 ... 057 0.38 0.19 ___ J = estimated -value (below laboratory quantitation limit). 080015095 BID62O830 FIGURES J S O O 15O06 EID620831 Figures can be found on hard copy in central files. JS O 015O 97 EID620832 ' APPENDIX 1 CONSENT ORDER (ORDER NO. GWR-2001-019) JSO01S099 EID620833