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Home My WebLink About7407_Pitt_C&DLandfillInc_CDLF_Phase1_Phase2_MNA_FID1822742_20231214MONITORED NATURAL ATTENUATION EVALUATION REPORT Closed Phase I Landfill C&D Landfill, Inc. Greenville, North Carolina 7407-CDLF-2001 Prepared for: C&D Landfill, Inc. 801 Recycling Lane Greenville, North Carolina 27834 Prepared by: �X. e sot�Ti ELM Site Solutions, Inc. P.O. Box 97607 Raleigh, North Carolina 27624 (919) 792-3733 December 2023 Closed Phase I Landfill C&D Landfill, Inc. Greenville, North Carolina 7407-CDLF-2001 Prepared for C&D Landfill, Inc. 801 Recycling Lane Greenville, North Carolina 27834 Prepared by X je Slot& Ti ELM Site Solutions, Inc. P.O. Box 97607 Raleigh, North Carolina 27624 (919) 792-3733 —qoseph Guarnaccia, PhD Senior Engineer rl� Senior Engineer Table of Contents Contents ExecutiveSummary......................................................................................................................4 Section1 Introduction................................................................................................................... 6 1.1. Purpose......................................................................................................................6 1.2. Limitations.................................................................................................................. 6 Section 2 Conceptual Site Model..................................................................................................8 2.1. Source Conditions......................................................................................................8 2.2. Hydrogeology...........................................................................................................11 2.3. Nature and Extent of Compounds of Interest...........................................................18 2.4 Fate Processes........................................................................................................ 22 Section3 Conclusions................................................................................................................28 Section4 References..................................................................................................................29 List of Tables Table 1 Data Summary Table for COls Table 2 Summary of COI Data Collected during the GSI Event Table 3 pH Data at Relevant Wells Table 4 Output from USGS (2021) Table 5 Fate and Transport Model Input/Output Summary List of Figures Figure 1 Site Location Map Figure 2 Facility Topography Figure 3 Coastal Plain Map Figure 4a Monitoring Well Network and Hydrogeologic Cross -Section Location Map Figure 4b Cross Section A -A' Figure 4c Cross section D-D' Figure 5 Typical Shallow Aquifer Water Level Contour Map Figure 6 Vertical Hydrogeology Map Figure 7 Hydraulic Head Map Figure 8 Shallow Groundwater Flow Map Figure 9 Benzene and Vinyl Chloride Data at Phase 1 Wells Figure 10 1,4-Dioxane and Tetrahydrofuran Data at Phase 1 Wells Figure 11 Evidence of Aerobic Degradation Figure 12 Evidence of Aerobic Co -metabolic Biodegradation Appendices Appendix 1 — Groundwater -Surface Water Interaction Study Work Plan and Data Summary Appendix 2 — Mann -Kendall Trend Analysis Appendix 3 — BioPic Model Closed Phase I Landfill 3 MNA Evaluation Report C&D Landfill, Inc. December 2023 Executive Summary On July 6, 2023, the North Carolina Department of Environmental Quality (NCDEQ), Division of Waste Management (DWM) Solid Waste Section (SWS) issued a letter regarding requirements for C&D Landfill, Inc.'s (C&D Landfill) Phase 1 closure (Permit number 7407-CDLF-2001). One requirement outlined in the letter was that a monitoring natural attenuation (MNA) evaluation be completed. Currently, the corrective actions for Phase I include landfill capping and MNA to restore groundwater quality at and beyond the relevant point of compliance, to effectively reduce the overall groundwater contamination at the landfill and to control the migration of contaminated groundwater to prevent unacceptable impacts. On September 8, 2023, a Corrective Action Plan (CAP) Addendum modifying the landfill capping portion of the remedy was submitted to the NCDEQ-DWM, SWS and was approved on October 20, 2023. This document presents a baseline MNA evaluation, under current conditions, for the recorded organic compounds that exceed their respective groundwater quality standards associated with the Phase 1 construction and demolition (C&D) debris landfill. The evaluation is based on six years of semi-annual groundwater data (2018 to 2023), additional groundwater data collected from a site -specific groundwater - surface water interaction (GSI) study and modeling to estimate the relevant degradation rates. The available data were compiled to develop a physically -based conceptual site model (CSM) that integrates source and hydrogeological and geochemical conditions with the observed nature and extent of site -specific organic compounds in groundwater. The CSM is summarized as follows: 1. Source conditions: Phase 1 is in hydraulic communication with local shallow groundwater, and because precipitation infiltration can potentially mobilize organic compounds present in C&D waste through dissolution, the landfill presents as a potential source for observed organic compounds in groundwater. 2. Hydrogeology: Phase 1 is in hydraulic communication with an unconfined shallow aquifer that is in hydraulic communication with surrounding surface water drainage features that represent groundwater discharge zones. 3. Compounds of Interest (COls): Based on the aforementioned six years of groundwater quality data, there are three COls that consistently exceed their Closed Phase I Landfill 4 MNA Evaluation Report C&D Landfill, Inc. December 2023 respective 15A NCAC 2L Groundwater Quality Standard (GWQS) or their interim maximum allowable concentration (IMAC): benzene, vinyl chloride, and 1,4-dioxane. In addition to these compounds, tetrahydrofuran is also included in the MNA analysis because it represents a co -metabolite that supports 1,4- dioxane biodegradation. 4. COls in groundwater: The nature and extent of COls in groundwater and groundwater geochemistry, including field parameters and parameters indicative of MNA processes, are characterized based on monitoring well data and groundwater data from the GSI study. The weight of evidence supports effective MNA for the COls under current conditions. The primary NA processes are: adsorption, mass uptake/destruction via groundwater interaction with plants, and metabolic and co -metabolic aerobic biodegradation. Application of the landfill capping portion of the approved corrective action program will continue to support effective MNA in two ways: 1. Reduce rainfall infiltration, which will reduce groundwater mounding (i.e., waste in contact with groundwater), and thus, volumetric mass flux. 2. Enhance COI mass uptake/destruction via groundwater interaction with plants and grasses. Closed Phase I Landfill Jr MNA Evaluation Report C&D Landfill, Inc. December 2023 Section 1 Introduction 1.1. Purpose On July 6, 2023, the North Carolina Department of Environmental Quality (NCDEQ), Division of Waste Management (DWM) Solid Waste Section (SWS) issued a letter regarding requirements for C&D Landfill, Inc.'s (C&D Landfill) Phase 1 closure (Permit number 7407-CDLF-2001) [FID1810242] (NCDEQ-DWM, SWS 2023a). One requirement outlined in the letter was that a monitoring natural attenuation (MNA) evaluation be completed. Currently, the corrective actions for Phase I include landfill capping and MNA to restore groundwater quality at and beyond the relevant point of compliance, to effectively reduce the overall groundwater contamination at the landfill, and to control the migration of contaminated groundwater to prevent unacceptable impacts. On September 8, 2023, a Corrective Action Plan (CAP) Addendum modifying the landfill capping portion of the remedy was submitted to the NCDEQ-DWM, SWS (ELMSS, 2023), and was approved on October 20, 2023 (NCDEQ-DWM, 2023b). This document presents a baseline MNA evaluation, under current conditions, for the recorded organic compounds that exceed their respective groundwater quality standards associated with the Phase 1 construction and demolition (C&D) debris landfill. 1.2. Limitations The MNA analysis presented herein follows the NC Solid Waste Section Guidelines for Monitored Natural Attenuation (NCDEQ-DWM, 2008) where MNA effectiveness is based upon the following technical and scientific demonstrations: 1. The reduction of the contaminant concentrations caused by chemical or biological attenuation of the contaminant; 2. The sampling analytical results show that the plume has stabilized horizontally and vertically in size and is not migrating; and 3. A statistical reduction in the contaminant concentrations along specific flow paths can be shown. Closed Phase I Landfill 6 MNA Evaluation Report C&D Landfill, Inc. December 2023 These aspects are in turn evaluated based on the development of a physically based conceptual site model (CSM) that connects observed groundwater quality conditions with a characterization of natural and anthropogenic source conditions, hydrogeology, geochemistry and fate processes, statistical evaluation of temporal trends, and application of appropriate MNA screening modes. The CSM is derived from a weight of evidence made apparent by a review of the following data and documentation: 1. Semi-annual compliance monitoring reports and associated data required by Phase 1 permit rule, completed and issued for the period between 2018 and 2023. The documents and associated data are available in the SWS files. The data include site -specific hydrogeological data (boring logs, aquifer parameters [thickness, hydraulic conductivity, and porosity] and monitoring well water levels), and groundwater and surface water volatile organic compounds (VOCs), metals, and field and MNA parameter analyses [as specified in NCDEQ-DWM (2008)]. 2. GIS data made available on the NC OneMap web site (NC OneMap) and on the Pitt County, NC, web site [Pitt County GIS Website (pittcountync.gov)], including regional geology, natural topography, surface water and wetlands features, and property lines. 3. Data made available from a site -specific groundwater and surface water interaction (GSI) study conducted in September 2023 according to the work plan provided in Appendix 1. Statistical evaluation of temporal trends is provided using an intrawell Mann -Kendal analysis tool (GSI, 2012). MNA screening is provided using two models: a USGS model (USGS, 2008) to assess geochemical conditions in groundwater, and BioPic (Danyko et al., 2021), a tool that follows EPA OSWER directive 9200.4-17P on MNA of chlorinated ethenes, while including ethanes and 1,4-dioxane. Closed Phase I Landfill 7 MNA Evaluation Report C&D Landfill, Inc. December 2023 Section 2 Conceptual Site Model 2.1. Source Conditions C&D Landfill, located at 802 Recycling Lane, Greenville, North Carolina, operates a C&D landfill under Solid Waste Permit # 7407- CDLF- 2001 and # 7407- CDLF- 2009 (hereinafter referred to as the 'Facility'). The Facility is comprised of two unlined landfill units, Phase 1 and Phase 2. The phases became operational in May 2001 and August 2009, respectively. It should be noted that a large percentage of the contents of Phase 1 is Hurricane Floyd flood damage debris in 1999 that resulted from the NCDEQ's request that C&D Landfill change their permit from Land Clearing and Inert Debris (LCID) to C&D in order to accept hurricane debris following the storm The Facility is currently required to submit semi-annual groundwater monitoring reports to the SWS. Figure 1 provides a Facility Location Map. Phase 1 ceased accepting waste in 2006 and entered final closure in late 2022. Phase 2 is currently active. The two phases were developed in two adjacent, non-contiguous, areas. Figure 2 depicts the natural and anthropogenic topography. Both areas were previously used for agricultural purposes. Phase 1 source conditions are characterized as follows: 1. Initially, Phase 1 operated as a LCID landfill and then, noted above, as a C&D landfill as an emergency disposal facility accepting demolition material resulting from Hurricane Floyd damage. 2. In general, C&D debris is non -hazardous solid waste generated during the construction, remodeling, repair or demolition of homes and buildings. Materials included in the C&D debris generation estimates are wood products, drywall and plaster, brick and clay tile, asphalt shingles, and concrete (Construction and Demolition Debris: Material -Specific Data I US EPA). 3. Phase 1 is unlined and currently capped with a native soil cover sourced from adjacent borrow areas with natural vegetation. Thus, it is hydraulically connected to the natural hydrogeologic setting through precipitation infiltration. 4. Organic compounds present in the C&D waste may be mobilized through dissolution into leachate generated from rainfall infiltration. 5. As discussed in Section 2.3, there are four organic compounds that consistently present in groundwater: benzene, vinyl chloride, 1,4-dioxane, and tetrahydrofuran. These compounds may be intermixed with the C&D waste as follows: benzene associated with BTEX-containing liquids, vinyl chloride associated with PVC materials used in many household products (furniture, Closed Phase I Landfill 8 MNA Evaluation Report C&D Landfill, Inc. December 2023 flooring, siding, etc.), and 1,4-dioxane (1,4-D) (and tetra hydrofuran) commonly associated with liquid surfactants (i.e., by-products of surfactant manufacture). It is noted that the NCDEQ-DWM, SWS has issued two historical memorandums that cite the need to sample for 1,4-D and THE as common contaminants in C&D landfills (NCDEQ-DWM 2010 and 2018, respectively). In summary, because Phase 1 is in hydraulic communication with local shallow groundwater, and because precipitation infiltration can potentially mobilize organic compounds present in C&D waste through dissolution, the landfill presents as a potential source for observed organic compounds in groundwater. Closed Phase I Landfill 9 MNA Evaluation Report C&D Landfill, Inc. December 2023 po!! fin 2 j- . I `•� _ y.xa own _ �- ighway 26 - ' Phase 2 Figure 1 - Site Location Map - Phase 1 and Phase 2 C&D debris landfills. Adapted from the 1979 USGS Grimesland, NC and Leggetts Crossroads, NC 7.5 Minute quadrangles. Closed Phase I Landfill 10 MNA Evaluation Report C&D Landfill, Inc. December 2023 %' Phase 2 —70' MSL Figure 2 — Facility Topography — includes surrounding terrain topography (elevations feet above mean sea level) and surface water features. The top elevation of the Phase 1 facility is approximately 100' above mean sea level (msl). The surrounding natural topography range is approximately 18' to 10' msl. 2.2. Hydrogeology The Site is located within the Coastal Plain physiographic and geologic province of North Carolina (Figure 3). It is underlain by the Yorktown Formation (Tpy), which is characterized as stratified fluvial deposits containing layers or pockets of low permeability and high permeability horizons. Site -specific boring logs (AMEC, 2017) confirm the surficial deposits (uppermost aquifer) consist of poorly stratified sand and clay layers, extending to depths varying between 12 and 30 feet. The upper sands are underlain by the Yorktown Formation, presenting as a sticky silty clay, which is easily identified by a deep green -gray color and a distinctive fossil -marker bed. Closed Phase I Landfill 11 MNA Evaluation Report C&D Landfill, Inc. December 2023 Based on boring logs (AMEC, 2017), the Facility -specific hydrogeology is characterized as a two -aquifer system (i.e., upper and lower sandy units separated by a clay confining layer). Figure 4a provides the existing well locations, and cross-section transects are provided in Figures 4b, and 4c. Hydrological Unit 1 (Aquifer Unit 1, 10 to 15 feet thick) is unconfined, while Hydrological Unit 2 (Aquifer Unit 2) is confined. Horizontal groundwater flow in the upper aquifer is toward the southwest and Grindle Creek, with water level contours that reflect the ground surface topography (Figure 5). This implies that unconfined conditions prevail. Based on hydrogeological data between 2018 to 2023, the estimated average groundwater seepage velocity (v) along the downgradient edge of Phase 1 is 20.5 feet/year (v = Ki/n, where average hydraulic conductivity, K = 205 feet/year, effective porosity, n = 0.08, and hydraulic gradient, i = 0.008 ft/ft). The vertical hydraulic gradient is illustrated in Figure 6 and Figure 7. Figure 6 shows the temporal trend in water level at each nested monitoring well set. The data show that the upper and lower aquifers are hydraulically isolated, and that the upper aquifer is affected by groundwater mounding due to Phase 1 s topographic effect (also depicted on Figure 5). Figure 7 shows that shallow groundwater discharges to surface water features that surround Phase 1 (also see Appendix 1). A comprehensive shallow aquifer flow map is presented in Figure 8, which includes the Pitt County GIS wetlands layer (characterized by mature swamp and bottomland forest). In summary, Phase 1 is in hydraulic communication with a 10- to 15-foot-thick unconfined shallow aquifer that is in hydraulic communication with surrounding surface water drainage features that represent groundwater discharge zones. Closed Phase I Landfill 12 MNA Evaluation Report C&D Landfill, Inc. December 2023 no COASTAL PLAIN QUATERNARY r7o� SURFICIAL DEPOSITS, UNDIVIDED —.Send, clay. grovel, end at depo- sited in marine, fluvial. eolian. and lacustrine environments Gijatprnary deposits not shown at altitudes greater than approximately 25 feet above mean sea level (Suffolk Scarp, in part) TERTIARY TP PINENURST FORMATION — Sand, Inedium- to coarse -grained. cross- - bedding and rhythmic bands of clayoy sand common, unconcolidatod T� TPRACC DCPOSITS AND UFLAND SCDIMCNT — GIAVCI. LIdyCy JdIld. _ and sand, minor iron -oxide cemented sandstone TpyW WACCAMAW FORMATION — F093111forou3 sand with alit and clay, hluish-gray to tan. lonsely r.nnsolidated StraddlPc PlaictnrAnN- Phocene boundary IDr YORKTOWN FORMATION AND DUPLIN FORMATION. UNDIVIDED Yorktown Formation: Fosslliferous clay with varyinq amounts of fine- grained sand. bluish gray, shell material commonly concentrated in lenses; mainly In area north of Neuse River Duplin Formation: Shellyy medium- to coaroc-grained sand, sandy marl, aril limwcinno. hluich (Iray: mainly in aroma cnuth of Nw iso River Figure 3 — Coastal Plain Map - The Facility is located in the NC coastal plain and Yorktown Formation and Duplin Formation, Undivided (NCTpy;11) (usas.gov) Closed Phase I Landfill 13 MNA Evaluation Report C&D Landfill, Inc. December 2023 Figure 4a: Monitoring Well Network and Hydrogeologic Cross -Section Location Map Monitoring well locations shown (the "D"-series wells are screened in the deep confined aquifer; all other wells are screened in the shallow unconfined aquifer). Closed Phase I Landfill 14 MNA Evaluation Report C&D Landfill, Inc. December 2023 MW-115O, h1W-14U .j PHASE 2 (A( I M MW 1s \ 11 -M11W � MW r j SVY3 2S MW-1_' �r , . r- MW3D MW-3S / MW-3A 10. 11 MW-5 i 11.3b Rw w.op -- XP- � • 10' MW-2o-_ ' MW-2S / e filet -- 8.59 r M PHASF 1 (( I OSFD) F' 11 r Ij Figure 5 — Typical Shallow Aquifer Water Level Contour Map (adapted from ELMSS, 2023, Figure 1). Data shown are from the Spring 2023 semi-annual monitoring event. Flow is generally to the southeast toward Grindle Creek. Figure 6 — Vertical Hydrogeology Map — shows temporal trend at each nested monitoring well set. The data show that the upper and lower aquifers are hydraulically isolated, and that the upper aquifer is affected by groundwater mounding due to Phase 1's topographic effect (see also Figure 5). Closed Phase I Landfill 16 MNA Evaluation Report C&D Landfill, Inc. December 2023 Figure 7 — Hydraulic Head Map — difference across the groundwater -surface water interface (PZ-series piezometers). A value of -999 indicates dry conditions at the time of sampling or otherwise, values indicate the head difference in feet between groundwater and surface water, where a positive value indicates groundwater discharge to the surface water (i.e., groundwater head is greater than the surface water elevation). Closed Phase I Landfill 17 MNA Evaluation Report C&D Landfill, Inc. December 2023 Figure 8 — Shallow Groundwater Flow Map - shows pattern emanating from the Phase 1 landfill based on water level data, stratigraphy, topography, and surface hydrology. 2.3. Nature and Extent of Compounds of Interest A review of the groundwater data collected between 2018 and 20231 shows that there are four organic compounds that consistently present above their respective method detection limits: benzene, vinyl chloride, 1,4-dioxane and tetrahydrofuran. These compounds are referred to as compounds of interest (COls). Given the hydrogeology discussed in Section 2.2, the following wells are used to assess the extent and fate of the COls in shallow groundwater emanating from the Phase 1 landfill: 1 Refer to semi-annual groundwater monitoring reports available at 7407 (nc.gov). Closed Phase I Landfill 18 MNA Evaluation Report C&D Landfill, Inc. December 2023 • Upgradient: MW-8, MW-11 and MW-12S • Downgradient: MW-2S, MW-3A, MW-3S, MW-5, MW-6 and MW-7 Table 1 provides a data summary between 2018 and 2023, Figure 9 provides time -series plots of the data associated with benzene and vinyl chloride, and Figure 10 provides the same for 1,4-dioxane and tetrahydrofuran. It is noted that three of the four COls (benzene, vinyl chloride and 1,4-dioxane) exceed their 15A NCAC 2L Groundwater Quality Standard (GWQS at one or more wells (see Table 1)). It is also noted that while tetrahydrofuran is present well below its standard, it is included in this analysis as a characterization compound. Specifically, tetrahydrofuran has been identified as a primary substrate that can support 1,4-dioxane co -metabolic biodegradation under aerobic conditions (ITRC, 2021, Section 3.1.7.2). This analysis is discussed further in Section 2.4. To assess the temporal stability of COls in groundwater, a Mann -Kendall (M-K) statistical analysis was applied to the data for each COI at each well (the data and analyses are presented in Appendix 2). Table 1 provides a summary of the M-K analysis. A review of Appendix 2 and Table 1 shows that COI impact is essentially stable (declining trends upgradient and stable trends downgradient). This is consistent with the concept that the source for the observed impacts is the Hurricane Floyd C&D waste resulting in a steady state to declining mass flux. The observed trends at monitoring wells are supported by the GSI data summarized in Table 2. • There is a clear attenuation trend along the flow path that connects wells MW-12S, MW-3A and MW-3S with piezometer PZ-5. • Shallow impacts close to the Phase 1 footprint (PZ-8, PZ-9A and PZ-10) tend to be higher than those at nearby monitoring wells (MW-2S, MW-6 and MW-7). This is primarily due to the fact that the sampling (screen) intervals are different, where the MW-series wells employ 10 to 15 foot screens that span the shallow saturated thickness, while the PZ-series piezometers employ a 1-foot screen located at the top of the saturated zone. While this is the case, as shown in Table 2, surface water in the discharge zone is unaffected showing attenuation across a short space scale (discussed further in Section 2.4). In summary, Phase 1 continues to provide a steady state to declining COI mass flux to shallow groundwater resulting in stable conditions that attenuate rapidly before discharge to surface water features. Fate processes are discussed in Section 2.4. Closed Phase I Landfill 19 MNA Evaluation Report C&D Landfill, Inc. December 2023 Table 1 - Data Summary Table for COls - data is generated between 2018 and 2023. Half the detection limit is used for non -detects. Wells are listed upgradient first (MW-8, MW-11 and MW-12S), then along the downgradient edges (MW-3A, MW-3S, MW-5, MW-2S, MW-6, and MW-7) Well Parameter NC 2L GWQS (uglL) Number of events Min (ugfL) Max (ugfL] Mean (ugfL] Median (ugfL] Standard Deviation (ugfL] COV Confidence Factor Mann - KendallMann-Kendall Test Value IS) Trend Test (90% Confidence Level) BZ 1.0 11 0.1 1.2 0.38 0.1 0.40 1.06 99% -28 Decreasing MW-8 VC 0.03 1 11 not detected 14D 3 10 36.50 218 86.130 76.400 43.32 0.57 50% -1 Stable THE 2000 11 7.94 32.3 17.822 14.70 7.83 0.44 68% -7 Stable BZ 1.0 11 0.1 2.6 0.85 0.7 0.74 0.88 96% -24 Decreasing MW-11 VC 0.03 11 0.1 0.7 0.20 0.1 0.23 1.14 93% -18 Prob. Decreasing 14D 3 10 1.35 25 12.346 3.000 8.16 0.66 81% 11 No Trend THE 2000 11 0.20 44.0 15.354 8.02 15.04 1 0.34 62% 5 No Trend BZ 1.0 11 1.1 3.0 1.33 2.1 0.53 0.30 70% 8 No Trend MW-123 VC 0.0 11 0.1 3.3 1.66 1.4 0.34 0.57 36Y -23 Decreasing 14D 3 10 8.82 35 24.782 28.200 3.87 0.40 81% 11 No Trend THE 2000 11 13.70 64.3 41.286 40.10 14.42 0.35 50% 1 No Trend BZ 1.0 11 0.1 1.7 0.87 0.3 0.51 0.59 1 84% -14 Stable MW-3A VC 0.03 11 1 not detected 14D 3 10 41.10 257 100.050 84.600 53.87 57% 3 No Trend THE 2000 11 4.50 30.6 16.332 16.50 8.39 tO.471 91% 18 Prob. Increasing BZ 1.0 9 0.5 2.3 1.31 1.2 0.62 62% 4 No Trend MW-33 VC 0.03 9 not detected 14D 3 8 118.00 326 180.250 167.000 63.62 0.35 98% -18 Decreasing THE 2000 9 23.10 35.3 27.756 26.60 3.35 0.14 80% -9 Stable BZ 1.0 10 not detected VC 0.03 10 not detected MW-5 140 3 9 7.22 74 27.484 20.200 20.73 0.76 50Y 0 Stable THE 2000 10 0.20 28.3 7.665 3.34 10.60 1.38 71/. -8 Stablrr BZ 1.0 11 not detected MW-2S VC 0.03 11 not detected 14D 3 10 1.36 129 28.596 11.600 40.83 1.43 76% -9 No Trend THE 2000 11 0.20 28.3 7.665 3.34 10.60 1.38 71'/. -8 No Trend BZ 1.0 11 not detected MW-6 VC 0.03 11 not detected 14D 3 10 1.35 40 18.305 17.400 12.46 0.66 89'/. -15 Stable THE 2000 11 0.20 15.2 8.235 6.88 5.16 0.63 62'/. -5 Stable BZ 1.0 11 not detected VC 0.03 11 not detected MW-7 140 3 10 1.35 19 10.232 3.655 6.30 0.62 76'/. -9 Stable THE 2000 11 2.47 32.0 13.037 11.50 3.33 0.76 62'/. -5 Stable Closed Phase I Landfill 20 MNA Evaluation Report C&D Landfill, Inc. December 2023 Figure 9 — Benzene and Vinyl Chloride Data at Phase 1 Wells - note that different scales are used at each well to highlight temporal trend. When considered with the hydrologic characterization, these compounds are sourced in the northwest corner of Phase 1 and in the drainage channel that separates Phase 1 and Phase 2. Figure 10 — 1,4-Dioxane and Tetrahydrofuran Data at Phase 1 Wells — note that different scales are used at each well to highlight temporal trend. These compounds are spatially widespread and co -located, which supports a common source. The highest concentrations are similarly located with benzene and vinyl chloride (see Figure 9). Closed Phase I Landfill 21 MNA Evaluation Report C&D Landfill, Inc. December 2023 Table 2 — Summary of COI Data Collected during the GSI Event (see Appendix 1). At each GSI location where water was available, a groundwater sample (PZ-series) and a surface water sample (SW-GS-series) were collected. The inset map is from Figure 8. Included in the Table are monitoring well (MW-series) and surface water (SW -series) data collected during, or previous to, the GSI event. The data are grouped by implied groundwater flow paths. c0I vc 1,4-D THE Location BZ [ug/L] [ug/L] [ug/L] [ug/L] PZ-1 ND ND ND ND SW-GS-1 ND ND ND ND PZ-2 1 3 ND 54 SW-GS-1 ND ND ND ND MW-12S 1 0.7 29 42 PZ-3 ND ND ND ND SW-GS-3 ND ND ND ND PZ-4 ND ND ND 19 SW-GS-4 ND ND ND ND SW-3 ND ND 5.6 3 MW-3A ND ND 82 22 MW-3S 1 ND 163 35 PZ-5 ND ND ND ND ND ND ND SW-GS-5 ND PZ-6 DRY SW-GS-6 ND ND I ND ND PZ-7 DRY SW-GS-7 ND ND ND ND MW-2S ND ND 1.4 23 PZ-8 ND ND 93.4 37 SW-GS-8 ND ND ND ND MW-6 ND NO 7 4 PZ-9A 0.71 ND 63.3 23.8 SW-GS-9 ND ND ND ND SW-2 ND ND ND 1 MW-7 ND ND 8.2 11.5 PZ-10 ND ND 14.6 20.5 SW-GS-10 ND ND ND ND PZ-11 1.59 ND 138 70 SW-GS-11 NM NM NM NM 2.4 Fate Processes Dissolved COls in groundwater migrate downgradient of Phase 1 via the following transport and fate processes: Transport: advection, dispersion, and diffusion. • Fate: o Adsorption o Mass uptake/destruction via groundwater interaction with plants: transpiration and root zone biological processes o Biotic mass destruction In this Section, the fate processes noted above are assessed. Closed Phase I Landfill 22 MNA Evaluation Report C&D Landfill, Inc. December 2023 Adsorption Adsorption to native organic carbon associated with aquifer materials will significantly retard the relatively hydrophobic COls (i.e., benzene and vinyl chloride), significantly reducing transport. 1,4-dioxane and tetrahydrofuran are miscible in water and thus, are unaffected by adsorption to organic carbon. It can be seen that discharging groundwater to wetland surface water must pass through organic -rich sediment, which is in part responsible for the observed attenuation of benzene and vinyl chloride. In this case, the retarded mass has time to be affected by other fate processes. Mass Uptake/Destruction via Groundwater Interaction with Plants Transpiration and Root Zone Biological Processes It can be observed from Figure 8 that discharging groundwater to wetland surface water must pass through extensive swamp and bottomland forest root zones. Because 1,4- dioxane and tetrahydrofuran are miscible in water and non-sorptive, they are readily taken up by the vegetation and transpired (essentially, a groundwater extraction and mass removal process). Once released into the atmosphere, 1,4-dioxane is photodegraded by UV light from the sun (ITRC, 2021). In addition to transpiration, research has shown that bacteria live in symbiotic communities near or within plants, and they may facilitate a bio- degradation process. Biotic mass destruction The Facility COls are susceptible to biodegradation, given favorable aerobic geochemical conditions. Parameters indicative of favorable conditions include: pH, dissolved oxygen (DO), oxidation-reduction potential (ORP) and reduction -oxidation conditions (REDOX). Table 3 shows that the shallow aquifer pH is in the optimal range between 5 and 9 (CLU- IN I Technoloaies > Remediation > About Remediation Technoloaies > Bioremediation > Aerobic Bioremediation (Direct)). Aerobic conditions are indicated when DO is >0.5 mg/L and ORP is >50 eV. Figure 10 shows that these conditions prevail, which is consistent with shallow unconfined aquifers. Finally, REDOX conditions are assessed using a USGS REDOX Assignment Model (USGS, 2008). Table 4 summarizes the conditions at relevant sampling points. These data, in concert indicate favorable geochemistry, support aerobic biodegradation. Under aerobic conditions, the end degradation product for benzene, vinyl chloride, and 1,4-dioxane degradation is carbon dioxide (CO2). While benzene and vinyl chloride are readily biodegradable as food sources, 1,4-dioxane must be degraded through a co - Closed Phase I Landfill 23 MNA Evaluation Report C&D Landfill, Inc. December 2023 metabolic process. Specifically, tetrahydrofuran represents a food source, and the biologically expressed enzymes used to degrade tetrahydrofuran also happen to degrade 1,4-dioxane, though the 1,4-dioxane is not necessarily a food source. Thus, 1,4-dioxane is degraded through co -metabolic degradation of tetrahydrofuran. Evidence of aerobic biodegradation of benzene and vinyl chloride is provided in Figure 11, which plots the time trend in concentration along with CO2, the terminal degradation product. Figure 12 provides the same presentation, but for 1,4-dioxane and tetrahydrofuran. In general CO2 increases while COls decrease. To further assess the fate of 1,4-D in groundwater, an NA model was developed (Danko et al., 2021) to estimate its decay rate (mass loss as a function of time). The calibrated model result is presented in Appendix 3, and the input/output parameters are summarized in Table 5. A concentration half-life was computed to be 3 years (i.e., the concentration is reduced by '/2 every 3 years). This result shows that a source concentration of 350 ug/L will attenuate to the GWQS in approximately 492 feet. Table 3 - pH Data at Relevant Wells - shows that the pH is within the optimal range (5 to 9) to support aerobic biodegradation processes. ate MW-12S MW-3A MW-3S MW-S MW-2S MW-6 6/12/18 6.8 6.8 6.8 7 6.7 6.6 12/10/18 6.6 6.7 6.9 6.6 6.6 6.8 6/15/19 6.6 6.8 6.8 6.6 6.5 6.7 12/15/19 6.7 6.8 6.9 6.7 6.8 6.8 6/22/20 6.7 6.8 6.7 6.8 6.5 6.7 12/2/20 6.9 6.8 6.9 6.9 6.6 6.6 6/23/21 6.6 6.5 6.7 6.7 6.3 6.6 12/15/21 6.8 7 6.9 6.6 6.9 6/27/22 1 6.7 1 6.8 6.8 6.9 6.7 6.9 12/15/22 6.9 6.9 7.5 9.1 7.1 6/22/23 1 6.72 6.81 6.8 8.57 6.52 Closed Phase I Landfill 24 MNA Evaluation Report C&D Landfill, Inc. December 2023 Table 4 - Output from USGS (2021) - uses recent data at each location shown. A blank cell means that no data was collected. Sample ID Redox Variables Dissolved 02 NO3- (as Nitrogen) Mn 2. Fe 2. Z_ SO, Sulfide (sum of HZS, HS', S s-) Redox Assignment Units milligAL __j millig/L f microg/L microg/L millig/L millig/L 0.6 0.5 50 100 0.6 none Threshold values Num of Params General Redox Category Redox Process MW-12s MW-3A Clear Redox MW-2S Assignments 0.98 0.02 0.632 1.3 15.5 0.9 6 Oxic 02 1.47 0.18 1 21 71 0.08 6 Oxic 02 3.14 1.89 0.0013 0.006 60.2 0.025 6 Oxic 02 MW-5 5.67 0.02 0-571 14.4 224 0.07 6 Oxic 02 MW-6 3.36 2 0.88 11.7 139 0.025 6 1 Oxic 02 MW-7 3.37 2 0.8 22 108 0.6 6 Oxic 02 MW-8 MW-11 Assign PZ-3 Redox PZ 4 Categories PZ-5 Processes PZ 8 2.8 0.11 0.84 27.2 226 0.11 6 Oxic 02 3.36 0.02 0.343 25.5 377 0.1 6 Oxic 02 16 6.9 0.03 0.1 10.3 0.4 6 Oxic 02 0.5 0.02 2.4 18.1 361 0.05 6 Oxic 02 0.44 3 0.08 0.47 14 0.05 6 Anoxic NO3 1 0.02 3.3 25 18.5 0.14 6 Oxic 02 PZ-11 0.02 2.7 14.7 5.9 0.1 5 OxicOrSuboxic 02?OrSuboxic PZ-9A 0.02 0.12 0.23 133 0.15 5 OxicOrSuboxic 02?OrSuboxic PZ-10 1.23 0.02 0.35 16.9 1 44.9 0.05 6 Oxic 02 Svr��a ♦: w16 2s 210 MW-12S \� u///w aA : 0 100 8 I 50 E r 0 a0 I O5 50 :S 0 -100 -OOI^! OAF 5 MW-3A s 1 • 100 5 1 13 50 = 0 82 p 1 50 - 0 -100 -001, -onv tmh a 6 140 / MW-S 5 120 100 3 so E 8 2 1 O 3 120 1 20 YiVA.2 3 100 �:Xa C •0 0 0 -DO In y 2 60 E ,° ,° �° 20 0 os w vrM 0 e+e a +o+° ,+�,ti �� -oti-DO[^WL) %,^ 3.5 3 ISO _ J2.1 2 100 E 50 $ Is I 0 0 0.5 -50 YOOI 0 -100 ADO ImWL a.aa,�a,+aaaa 3 2 5 210 no 5 2 E 11 100 s0 E 8 5 50 ff 05 -100.W� 0 -ISO _00[mWL �o y �l°+y��+ �+ y�OAi [mV] 150 100 50 E Oo I5 1 0 c -50 O O5 -100imm 0 I50 tDO 119A] � 2DO MR'•6 3 5 150 a 2 5 100 E E 2 50 S IS 0 O 1 05 w 0 -100 -DO I- - ,°'y�,° yp° ��v°$��,°+°$~aA`� _oar 1- .. a .5'a a�a,\bS�a�a a+ Figure 10 - Temporal trends in DO and ORP - shows that aerobic conditions prevail in the shallow, unconfined, aquifer (i.e., DO >0.5 mg/L and ORP >50 mV (see Table 3)). This is consistent with the oxidizing conditions resulting in Table 3. Closed Phase I Landfill 25 MNA Evaluation Report C&D Landfill, Inc. December 2023 533 MWll 4ao500°°00 3soaoo - -- s.s M W 12S,s500°o0O > z 2 x350=w 5 a 3 _ S is • 1�0sro°°°oo g j2.5 30000o aJ1 = 1 loaaao V 2 2s00oo ? iei X o.s 5°000 E'LZ i 125 000 0 �oenzene ° ° 8 os sOW —vinyl ouoriee R; a R R c a o _ o SSaa- -a �r o °^° —(2r0on Dioxide a m a a ? 3S MW8 ,s500OW \ ` \ ` = Sraso 00P __,µ / r zsVA % • io500°°0000 3 -- 3s M W 3A ,sa000 > z • 20DODD 3 zs . 350000 -- +s,•..L g 1.5 1 � o > 300000 ? I 3 IODOOD u 2 • 250000 .J 'I ` 0.5 s0000 g 1S z00000 o o 0 0 ioW 19:31 IS 88UU�b �b o.s WOW «« «««« 0 0 �r• - �6$T��R ^12Ma• �« �n3aaaa3a3aa ° MW3S , mm R R R R R C 2 r s 2 1 MW7 ,w500°°°roo '3.s ,Doom ��3?��a`a� -3.s 3 3 35mm '�. �^ '�' a '� a s l 3 3,500000 _ u 12 233 0OODO , 50ODDO s z.2 J'-. 30000o aJi> MWS asoDDD yy z / 20mm _ '' ]SOOm ? 33 35400°°°WOD `� 11 .�(/ 3 lamm j 8 0.5 SDooO > 2= 3 3 -•Z- / o.s 500�°0°° 0 0 1.5 // % o p 0 ,P4,�9,A•9,�11 looti 141�,Av' "' 1 imm" ./ �� RRRRR?Zs��R 0 0 �a3aaa• aa^ s ~ a a n n 535 MW2S 4a5o5000m0000 ° MW6 .Sa500°°°aao 3.s 'mom• u a ar -' 25 30005°00°00 a s I.5 350000 - 2 2s = > 3oom0 Jai 200D00 2 . zsoom _. c l.s `\\ v • 1500m O l.s • 100DDO O 7 1 y"'' 100D0o V •• 1 2� J 8 as s0000 M as saom 0 0 0 0 ;3 5, css� Sa^3�3 aa�! caaaaa?aa^ Figure 11 — Evidence of Aerobic Degradation. Plots of benzene, vinyl chloride and carbon dioxide (CO2), where CO2 is the terminal degradation product for both benzene and vinyl chloride under aerobic conditions. CO2 tends to increase as benzene and vinyl chloride decrease. Note that the plotting scales are held constant to provide a comparison with respect to magnitude. 350 5 3W M W l l ,aso500°°°0000 250 350DOO ^ 33o M W 12S �,50500°°D000• 4 zm 3m0m LL 250 - 350000 c 350 • 25m0D _ 10OWD t zm • 250DDD 5 0• lm lsamo y 200000 - 5000D C 1W 125 mU o PARAMETERjDmide 0°0°°so SOoo-1,a-Droo S 6 b o 6 s S 0°�Te hy= rponJ a a « °° ..T. "R % s z N R .v _ 350 5°°OD° ? a a a s u a s a 300 MW8 4000DO 250 35C°pp0 .--• a r 000 MW3A 455000000000 .-y:-;- - =zoo • • 25mO 400000 _ lso - 250 350000 o• lo0 15000o O c_I • • 250000 a `� 50000 y 0150 V SOW O D 0 gy m.. s a a o S o o a3w MW3S 400 ,so5000moDoo aa3a�aa3a\ea _ a3W MW7 .s502mo zso-�•-� 3saom ^ °--�'-'• 3 zso 35,0OOOOoaoO - i zm 3aaom j350 150 c MWS ,d / _ c / zIw zw0moo ;a O '°° • boom 0DOO" 250 350000 - l/�j o lro o 30000o j 1ao°Oo 50 so°0°° c 15�0 2500m soo°o .^. c .a. 0 JJ 15ooDoDDDW � % 0 a 0 8 "s s 8 O• lm / 250000 3 /• c p S s 8 «E' S �C�� h_ 'osoo0°°°°00 / /` 33azSSc -Sr-- - — 3a a3e tea^ S a a a c a a ^ 3- MW2S ,50s°04o _ 3so MW6 ,sa500oa0000 a' a � a uZ a a a 250 3400s °D°o - aJia ,00000 3500DO - 200 zs� ? t 2m ` ,/• 3o00m% ]SO • 20DDDO «o c 150 V • 2500°° 3 Im \ _ _ io500000000 8 c 100 • 15°°°° O 30 lam^ SOOoo a so 30000D V 0 o so0oo 0 0 " o Q Q o Q C M EEC' R o "' o 0 0 6 s a-;s 2-:9 s a��aaa^3a�^ Figure 12 — Evidence of Aerobic Co -metabolic Biodegradation. Plots of 1,4-dioxane, tetrahydrofuran and CO2, where CO2 is the terminal degradation product for 1,4-dioxane under aerobic conditions. CO2 tends to increase when 1,4- dioxane decreases. Closed Phase I Landfill 26 MNA Evaluation Report C&D Landfill, Inc. December 2023 Table 5 — Fate and Transport Model Input/Output Summary (Appendix 3). The model shows that under steady state source conditions, the decay rate is sufficient to achieve compliance at the receptor Model input parameter value units comment seepage velocity 20.5 ft/yr averag 2018 to 2023 source released 2003 2 years after filling began source concentration 350 ug/L highest value recorded in GW source decay 0 /year steady state source width 1000 feet between MW-12S and -2S receptor distance from source 500 feet from source to PZ-5 data along plume CL in 2018 180 ug/L at MW-3S/A 3 ug/L 2L at PZ-5 (assume steady state) transport time from source to receptor 24 years =distance /velocity Model output parameter value units comment 1st order decay rate (k) 0.225 /year C(t)/C(t=0) = ell(-kt) time required to degrade 350 ug/L to 3 ug/L 21 years =-LN(3/350) / 0.225 Closed Phase I Landfill 27 MNA Evaluation Report C&D Landfill, Inc. December 2023 Section 3 Conclusions The weight of evidence supports effective MNA for the COls under current conditions. The primary NA processes are: adsorption, mass uptake/destruction via groundwater interaction with plants, and metabolic and co -metabolic aerobic biodegradation. Application of the landfill capping portion of the approved corrective action program will continue to support effective MNA in two ways: • Reduce rainfall infiltration, which will reduce groundwater mounding (i.e., waste in contact with groundwater), and thus, volumetric mass flux. • Enhance COI mass uptake/destruction via groundwater interaction with plants and grasses. Validation of these MNA conclusions, specifically that source mass flux will be significantly reduced with implementation of landfill capping, can be achieved by monitoring the temporal trends of field parameters (pH, DO, ORP, specific conductance) and the COls from continued semi-annual monitoring of the following wells: MW-2S, MW- 3A, MW-3S, MW-5, MW-6, MW-7, MW-8, MW-11, and MW-12S. Closed Phase I Landfill 28 MNA Evaluation Report C&D Landfill, Inc. December 2023 Section 4 References AMEC (2017). "Assessment of Corrective Action, C&D Landfill, Inc." 7407 (nc.gov): 7407 CandDLandfilllnc 20171031 ACM DIN28637 GSI (2012). Software User's Manual GSI Mann -Kendall Toolkit for Constituent Trend Analysis, Version 1. GSI Mann Kendall Toolkit - GSI Environmental Inc. Danko et al. (2021). "BioPic Users Guide." Development of a Quantitative Framework for Evaluating Natural Attenuation of 1,1,1-TCA, 1,1-DCA, 1,1-DCE, and 1,4-Dioxane in Groundwater (serdp-estcp.org). ELMSS (2023). "Corrective Action Plan Addendum." September 8, 2023 [7407 Pitt C&DLandfilllnc CDLF Phase1 CAPAddendum FID1817418 202309081. ITRC (2021). "Technical Resources for Addressing Environmental Releases of 1,4-dioxane. Interstate Technology & Regulatory Council, February 2021. 14d (itrcweb.org). NCDEQ-DWM (2008). "MNA Excerpt from Examples of Approved Groundwater Corrective Measures for Solid Waste Management Facilities." NCDEQ-DWM, June 2008. STATE OF NORTH CAROLINA (nc.gov). NCDEQ-DWM (2010). "Tetrahydrofuran Analysis at Construction and Demolition Landfills." North Carolina Division of Waste Management, Solid Waste Section. 6/25/2010. download (nc.gov). NCDEQ-DWM (2018). "1,4-Dioxane Analysis, Solid Waste Section Limits, and Laboratory Analytical Methods." North Carolina Division of Waste Management, Solid Waste Section, 5/29/2018. download (nc.gov). NCDEQ-DWM (2023a). Groundwater Corrective Action Plan Addendum Requirement letter. July 6, 2023 Fin lRingag NCDEQ-DWM (2023b). Corrective Action Plan Addendum approval letter, October 20, 2023.[7407 Pitt C&DLandfilllnc CDLF Phase1 Phase2 CAPAddendumResponse FID1819368 20231 020]. USEPA (2023). "Construction and Demolition Debris: Material -Specific Data." Construction and Demolition Debris: Material -Specific Data I US EPA. November, 2023. USGS (2008). "An Excel® Workbook for Identifying Redox Processes in Ground Water." USGS Open -File Report 2009-1004: An Excel <sup>®</sup> Workbook for Identifying Redox Processes in Ground Water. Closed Phase I Landfill 29 MNA Evaluation Report C&D Landfill, Inc. December 2023 Appendices Closed Phase I Landfill MNA Evaluation Report C&D Landfill, Inc. December 2023 Appendix 1 Groundwater -Surface Water Interaction Study Work Plan and Data Summary Closed Phase I Landfill MNA Evaluation Report C&D Landfill, Inc. December 2023 Work Plan for Field Groundwater -Surface Water Interaction Study C&D Landfill, Inc., Greenville, NC August 2023 Project Description The Phase I landfill at the C&D Landfill, Inc. facility (Site) began operations in 2001 and ceased accepting waste in 2006. The landfill is unlined and accepted construction and demolition (C&D) debris. To evaluate MNA and confirm the conceptual site model, ELMSS proposes to characterize the natural attenuation processes associated with volatile organic compounds (VOCs) and 1,4- dioxane in groundwater at concentrations that exceed the 2L Standards and verify that site groundwater discharges to surface water immediately downgradient of landfill Phases 1 and 2. To achieve this goal, a groundwater -surface water interaction study is proposed. Objectives The purpose for this work is to meet the following objectives: 1. Verify the conceptual site model that Site related groundwater discharges to surface water immediately downgradient of the Site, 2. Delineate Site -related groundwater impact. 3. Characterize natural attenuation processes associated with VOC impacts (biotic, abiotic, mass balance). Field Methodology The Solnist Drive Point Piezometer, Model 615, will be used to collect pore water (i.e., groundwater) chemistry and hydraulic gradient data within the hyporheic zone of the tributaries located upgradient and downgradient of the Site (see Figure 1). Dedicated polyethylene tubing will be attached to the screened interval of the drive point and the drive point will be driven into the sediment of the tributaries at 10 to 12 locations to a depth of approximately 2 to 4 feet. Once placed, the pore water pressure will be allowed to equilibrate whereupon the static water level in the drive points will be compared to the surface water level in the tributary. The hydraulic gradient magnitude and direction will be recorded as an indication of groundwater discharge or recharge. Where groundwater discharge conditions are observed, groundwater and surface water quality samples will be collected. For the groundwater samples, a peristaltic pump will be used to low - flow purge (50 to 200 ml/min) the drive points to obtain pore water field parameters (temperature, pH, dissolved oxygen, specific conductance, redox potential, and turbidity). Once stabilized field parameters are obtained, a pore water sample will be collected into laboratory sample containers for subsequent laboratory analysis of metals, VOCs, 1,4-dioxane, and MNA parameters (i.e., nitrate+nitrite, TOC, alkalinity, chloride, TDS, sulfate, sulfide, carbon dioxide, and dissolved gases). For the surface water samples, a peristaltic pump will be used to low -flow purge the surface water immediately next to each drive point. A surface water sample will be collected into laboratory sample containers for subsequent laboratory analysis of metals, VOCs, and 1,4- dioxane. Once the sampling is complete, the GPS coordinates for each location will be recorded. The drive point will be removed (if possible) and decontaminated for use at the next sample location. At a given drive point location, a pore water sample will not be collected if one of two conditions prevail as follows: 1. If the drive point is placed in sediment of such low hydraulic conductivity that a pore water sample cannot be collected in a reasonable amount of time (on the order of/z hour), then the location will be abandoned and marked as not permeable. 2. If the hydraulic gradient indicates downward flow, then the location will be marked as aquifer recharge. This protocol is considered appropriate because both of these conditions imply that significant groundwater discharge is not occurring at these locations. In order to provide a connection between surface water and groundwater quality at the time of sampling, in addition to the drive point locations identified above, the following existing wells will be sampled for the same analytical list as above: MW-2S, MW-3S, MW-3A, MW-5, MW-6, MW-8, MW-12S, MW-13, and MW-14S. Quality control samples will include one duplicate sample, one equipment blank, and one trip blank for the groundwater samples. Decontamination Procedure The drive point piezometers will be decontaminated using the following procedure before reuse at the next location: 1. Rinse the equipment with potable water; 2. Wash the equipment in a Liquinox/water solution; 3. Rinse the equipment with deionized or distilled water; and 4. Let equipment air dry before collecting the next sample. Appendix 2 Mann -Kendall Trend Analysis Closed Phase I Landfill MNA Evaluation Report C&D Landfill, Inc. December 2023 Analysis of Temporal Trends Mann -Kendall Summary Table Well Parameter NC 2L GN0]5 fugfL] Number of events Min [ug1L] Max [uglQ Mean (ug1L] Median (ug1L) Standard Deviation fugrL] COV Confidence Factor Mann - Kendall Test Value [S] Mann -Kendall Trend Test 190% Confidence Level) B 1.0 11 0.1 1.2 0.38 0.1 0.40 1.06 99/ -28 decreasing MW-8 VC 0.03 11 not detected 14D 3 10 36.50 218 86.190 76.400 49.32 0.57 50% 1 -1 Stable THE 2000 11 7.94 32.9 17.822 14.70 7.83 0.44 68% -7 Stable B 1.0 11 0.1 2.6 0.85 0.7 0.74 0.88 96% -24 Decreasing MW-11 VC 0.03 11 0.1 0.7 0.20 0.1 0.23 1.14 93% -18 Prob. Decreasing 14D 3 10 1.35 25 12.346 9.000 8.16 0.66 81% 11 No Trend THE 2000 11 0.20 44.0 15.954 8.02 15.04 0.94 62/ 5 No Trend B 1.0 11 1.1 3.0 1.99 2.1 0.59 0.30 70% 8 No Trend MW-125 VC 0.0 11 0.1 3.3 1.66 1.4 0.94 0.57 96% -23 Decreasing 14D 3 10 8.82 35 24.782 28.200 9.87 0.40 81% 11 No Trend THE 2000 11 13.70 64.9 41.286 40.10 14.42 0.35 50% 1 No Trend B 1.0 11 0.1 1.7 0.87 0.9 0.51 0.59 84/ -14 Stable MW-3A VC 0.03 11 not detected 14D 3 10 41.10 257 100.050 84.600 59.87 0.60 57% 3 No Trend THE 2000 11 4.50 30.6 16.992 16.50 8.39 0.49 91% 18 Prob. Increasing B 1.0 9 0.5 2.3 1.31 1.2 0.62 0.47 62% 4 No Trend MW-3S VC 0.03 9 not detected 14D 3 8 118.00 326 180.250 167.000 63.62 1 0.35 1 98% L -18 1 Decreasing THE 2000 9 23.10 35.3 1 27.756 26.60 3.95 1 0.14 1 BO/ -9 Stable B 1.0 10 not detected MW-5 VC 0.03 10 not detected 14D 3 9 7.22 74 27.484 20.200 20.79 0.76 50% 0 Stable THE 2000 10 0.20 28.9 7.665 3.94 10.60 1.38 71'/. -8 1 Stable B 1.0 11 not detected MW-2S VC 0.03 11 not detected 14D 3 10 1.36 129 28.596 11.600 40.83 1.43 76% -9 No Trend THE 2000 11 0.20 28.9 7.665 3.94 10.60 1.38 71% -8 No Trend B 1.0 11 not detected MW-6 VC 0.03 11 not detected 14D 3 10 1.35 40 18.905 17.400 12.46 1 0.66 89% -15 Stable THE 2000 11 0.20 15.2 8.235 6.88 5.16 1 0.63 1 62% FEW5 1 Stable B 1.0 11 not detected MW-7 VC 0.03 11 not detected 14D 3 10 1.35 19 10.232 9.655 6.30 0.62 76% -9 Stable THE 2000 11 2.47 32.0 13.097 11.50 9.93 0.76 62% -5 Stable MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name: C&D Landfill Constituent: MW-2S Conducted By: I ELMSS Concentration Units: ug/L Sampling Point ID: Benzene I Vinyl Chloride 1 4-dioxane I THE Event MP Date • • 1 6/15/18 0.12 0.32 1.1 2 12/15/18 0.12 0.06 6.20 4.9 3 6/15/19 0.12 0.06 11.90 3.9 4 12/15/19 0.44 0.06 129.00 27.9 5 0.12 0.06 12.10 3.8 6/15/20 6 12/2/20 0.12 0.06 11.30 4.1 7 6/15/21 0.12 0.06 3.99 0.2 8 12/15/21 0.12 0.06 38.50 9.2 9 6/13/22 0.36 0.06 67.60 28.9 10 12/12/22 0.12 0.06 4.01 0.2 11 7/5/23 0.12 0.06 1.36 0.2 12 13 14 15 16 17 18 19 20 Coefficient of Variation: i Mann -Kendall Statistic (S): Confidence Factor: �6& Concentration Trend: • . . 1000 Benzene J 100 tVinyl Chloride � -�1,4-dioxane -M-THF 10 O :r � 1 C O � 0.1 O U 0.01 09/17 02/19 06/20 10/21 03/23 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name. C&D Landfill Constituent: MW-3A Conducted By: ELM SS Concentration Units: ug/L Sampling Point ID: Benzene Vinyl Chloride 1 4-dioxane THE r. - • • 6/15/18 0.50 0.32 4.5 r52 12/15/18 1.69 87.00 24.4 6/15/19 1.00 0.06 66.90 8.4 12/15/19 1.49 0.06 257.00 20.5 0.94 0.06 88.00 16.5 6/15/20 6 12/2/20 0.82 0.06 73.10 16.5 7 6/15/21 0.12 0.06 41.10 5.8 8 12/15/21 0.12 0.06 88.20 13.5 9 6/14/22 0.88 0.06 82.00 25.2 10 12/14/22 1.32 0.06 135.00 30.6 11 6/30/23 0.67 0.06 82.20 21.0 12 13 14 15 16 17 18 19 20 Coefficient of Variation: Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: 1000 Benzene tVinyl Chloride J 100 d 1,4-dioxane - THE O 10 O Y >4 1 C d 0.1 O U 0.01 09/17 02119 06120 10121 03123 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name. C&D Landfill Constituent: MW-3S Conducted By: ELM SS Concentration Units: ug/L Sampling Point ID: Benzene Vinyl Chloride 1 4-dioxane THE • • 6/15/2018 1.20 28.80 752 12/15/2018 1.30 184.00 35.30 6/15/2019 0.89 0.06 176.00 26.60 12/15/2019 1.81 0.06 326.00 23.10 2.04 0.06 191.00 28.40 6/15/2020 6 12/15/2020 0.46 0.06 158.00 25.60 7 6/15/2021 0.83 0.06 142.00 24.80 8 12/15/2021 0.93 0.06 147.00 24.80 9 6/14/2022 2.30 0.06 118.00 32.40 10 11 12 13 14 15 16 17 18 19 20 Coefficient of Variation: 1.81 r 0.14 Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: No Trend Prob. 1000 Benzene tVinyl Chloride J 100 -*--1,4-dioxane - THE O 10 O Y i 1 C d 0.1 O U 0.01 09/17 04118 10/18 05/19 12119 06/20 01121 07/21 02122 08/22 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: I MNA Report Facility Name: I C&D Landfill Constituent: MW-5 Conducted By: I ELM SS Concentration Units: I ug/L Sampling Point ID: Benzene Vinyl Chloride 1 4-dioxane I THE Event Date CONCENTRATION 1 6/15/18 0.12 0.32 1.3 2 12/15/18 0.12 0.06 16.40 2.3 3 6/15/19 0.12 0.06 74.20 6.8 4 12/15/19 0.12 0.06 31.70 2.5 5 0.12 0.06 9.24 0.9 6/15/20 6 12/2/20 0.12 0.06 7.22 1.1 7 6/15/21 0.12 0.06 16.80 1.5 8 6/15/22 0.12 0.06 42.40 8.2 9 12 12 22 0.12 0.06 29.20 4.6 10 1 6/30/23 0.12 0.06 20.20 0.2 11 12 13 14 15 16 17 18 19 20 Coefficient of Variation: llllllllllllll0.00 Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: Stable Stable Stable Stable 100 Benzene J tVinyl Chloride 10 -�1,4-dioxane -M-THF C O 1 Y L r+ N ilk" C v 0.1 _ c O U 0.01 09/17 02119 06120 10121 03123 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name: C&D Landfill Constituent: MW-6 Conducted By: I ELMSS Concentration Units: ug/L Sampling Point ID: Benzene Vinyl Chloride 1 4-dioxane I THE Sampling Event Sampling r. te W-6 • • 1 6/15/18 0.12 0.32 5.6 2 12/15/18 0.12 0.18 13.50 6.9 3 6/15/19 0.12 0.06 40.10 14.4 4 12/15/19 0.12 0.06 25.30 14.7 5 0.12 0.06 23.00 12.2 6/15/20 6 12/2/20 0.12 0.06 1.35 0.2 7 6/15/21 0.12 0.06 19.70 2.8 8 12/15/21 0.39 0.06 35.70 15.2 9 6/15/22 0.12 0.06 8.66 7.7 10 12/14/22 0.12 0.06 15.10 6.9 11 7/5/23 0.12 0.06 6.64 4.1 12 13 14 15 16 17 18 19 20 Coefficient of Variation: 6 0.56 1 0.87 Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: No Trend I Prob. 100 Benzene J tVinyl Chloride 10 -�1,4-dioxane - THE C O 1 :r R w C � 0.1 c O U 0.01 09/17 06/20 10/21 03/23 1 "02119 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name: C&D Landfill Constituent: MW-7 Conducted By: I ELMSS Concentration Units: ug/L Sampli ng Point ID: Benzene I Vinyl Chloride 14-dioxane I THE Event MN Date • • 1 15-Jun-18 0.12rO2 6.3 2 15-Dec-18 0.12 18.20 32 3 15-Jun-19 0.316 17.00 27 4 15-Dec-19 0.126 8.51 2.47 5 15-Jun-20 0.126 10.80 19.3 6 2-Dec-20 0.126 1.35 3.23 7 15-Jun-21 0.12 0.06 3.53 3.5 8 15-Dec-21 0.12 0.06 19.20 18.1 9 15-Jun-22 0.12 0.06 4.33 8.67 10 12-Dec-22 0.12 0.06 11.20 12 11 6-Jul-23 0.12 0.06 8.20 11.5 12 13 14 15 16 17 18 19 20 Coefficient of Variation: 0.42 Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: Stable No Trend Stable Stabld 100 Benzene tVinyl Chloride J 10 -A--1,4-dioxane OE - THE C :rO 1 R w C � 0.1 c O U 0.01 09117 02119 06120 10121 03123 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: I MNA Report Facility Name: I C&D Landfill Constituent: MW-8 Conducted By: I ELM SS Concentration Units: I ug/L Sampling Point ID:J Benzene I Vinyl Chloride I 14-dioxane I THE Event MN r. te • • 1 15-Jun-18 0.30 0.32 10.5 2 15-Dec-18 0.48 49.3 21.2 3 15-Jun-19 1.17 0.06 94.7 28.1 4 15-Dec-19 1.13 0.06 218.0 32.9 5 15-Jun-20 0.36 0.06 71.0 14.7 6 2-Dec-20 0.12 0.06 36.5 7.94 7 15-Jun-21 0.12 0.06 78.0 10.9 8 15-Dec-21 0.12 0.06 81.5 22.4 9 15-Jun-22 0.12 0.06 84.8 19.9 10 15-Dec-22 0.12 0.06 74.8 1 14.5 11 30-Jun-23 0.12 0.06 73.3 13 12 13 14 15 16 17 18 19 20 Coefficient of Variation: Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: • - 1000 ..Benzene tVinyl Chloride J 100 dk � -�1,4-dioxane -M-THF O 10 O Y >4 1 C d 0.1 O U 0.01 09117 02119 06120 10121 T3123 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis J Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name: C&D Landfill Constituent: MW-11 Conducted By: I ELMSS Concentration Units: ug/L Sampli ng Point ID: Benzene Vinyl Chloride 14-dioxane THE Event MN Date • • 1 15-Jun-18 0.90 0.32 16 2 15-Dec-18 0.48 0.06 8.2 8.02 3 15-Jun-19 1.89 0.69 9.2 17.3 4 15-Dec-19 2.56 0.57 25.2 43.8 5 15-Jun-20 0.84 0.06 1.4 0.2 6 2-Dec-20 0.62 0.14 6.7 5.16 7 15-Jun-21 0.34 0.06 5.8 5.32 8 15-Dec-21 0.12 0.06 8.8 7.43 9 27-Jun-22 0.75 0.06 22.1 44 10 15-Dec-22 0.73 0.12 22.4 20.4 11 29-Jun-23 0.12 0.06 13.8 7.86 12 13 14 15 16 17 18 19 20 Coefficient of Variation: 0.88 1.14 IF 0.66 Mann -Kendall Statistic (S): Confidence Factor: •' Concentration Trend: Decreasing Prob.. Trend No Trend 100 Benzene J tVinyl Chloride 10 -&---1,4-dioxane - THE C 1 OIf R w C � 0.1 c O U 0.01 09/17 02119 06120 10121 03/23 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com MANN-KENDALL TOOLKIT for Constituent Trend Analysis Evaluation Date: 8-Aug-23 Job ID: MNA Report Facility Name. C&D Landfill Constituent: MW-12S Conducted By: ELM SS Concentration Units: ug/L Sampling Point ID: I Benzene Vinyl Chloride 1 4-dioxane THE r. - • • 1 6/15/2018 1.4 32.7 2.9 2 12/15/2018 1.5 2.2 8.8 38.75 3 2.5 3.3 6/15/2019 32.8 64.9 12/15/2019 27.4 40.1 4 2.1 1.3 5 2.1 1.8 6/15/2020 24.4 51.4 6 12/2/2020 14.1 29 7 6/15/2021 11.1 13.7 8 12/15/2021 34.5 59.3 9 6/27/2022 4j2.1 34.6 48.3 10 12/15/2022 31.1 34 11 6/29/2023 29.0 42 12 13 14 15 16 17 18 19 20 Coefficient of Variation: Mann -Kendall Statistic (S): Confidence Factor: Concentration Trend: 100 Benzene J 10 tVinyl Chloride -o-1,4-dioxane -.o-THF C O 1 Y L r+ C v 0.1 c O U 0.01 09/17 06120 10121 03123 Sampling Date Notes: 1. At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples. 2. Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing; >_ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S:50, and COV >_ 1 = No Trend; < 90% and COV < 1 = Stable. 3. Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales, Ground Water, 41(3):355-367, 2003. DISCLAIMER: The GSI Mann -Kendall Toolkit is available "as is". Considerable can; has been exercised in preparing this software product; however, no party, including without limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein. GSI Environmental Inc., www.gsi-not.com Appendix 3 BioPic Model Closed Phase I Landfill MNA Evaluation Report C&D Landfill, Inc. December 2023 MNA Rate Constant Estimator Site Name C&D Landfill Run Name 1 Date/Other 11/20/2023 1,4-Dioxane 4. SOURCE DATA Source Width 1000 (feet) Enter: tool source concentration 2111 Actual sourceconc.• 2111 Modeled source Cone. (ti9A) (a9iu (.910 KEY. 1. ADVECTION Year Source Released 2003 (xxxx) 1,4-Dioxane 350 350 Enter directly calculaj— Seepage Velocity Vs (ft/yd Year for Initial Source Concentration 2003 (xxxx) Formula SourceRestore Attenuation Rate: calselect a typical rate below, or adjust the rate so Column O bes 0.000 (per year) matches Column P. ______________________________________ ............................ ....................... Hydraulic Conductivity K 2.1E+02 (ft/yrf Typical Source Attenuation Rates: Constant Source: Some source after.: iFaster source other: i Leave blankiifsouaeroreiszerooriJcalibmtion (for Simplest way to Nn model enter zero) enter Oper year i 0.22 per year 0.45 per year year is same os year your source Eatastans. Hydraulic Gradient i 0.008 (ft/ft) S. FIELD DATA FROM MONITORING WELLS ALONG PLUME CENTERLINE Effective Porosity ne 0.08 (-) Year Data was Collected: (ug/L) (ug/0 (ug/L) (ug/L) Ng/L) (ug/L) (ug/L) (ug/L) Criteria (ug/L) 2. ADSORPTION Total Porosity n 0.3 (-) 1,4-Dioxane r 3 3.00 Fraction Organic Carbon foc 0Distance from Source (ft) S00 0.009 Retardation Factor Rf 0Well Name (optional) MW-35/A PZ-S Restore 3. GENERAL 6. BIODEGRADATION: ADJUST TO MATCH FIELD Biodegradation Rate Constant Estimation Tools (Optional) Calibrate Model to Data From this Year 2018 (xxxx) DATA; USE 6B OR 6C FOR HELP 6b: Estimate from Biomarker Data 6c: Initial Estimate from Field Data (Above) See Output in this Year 2023 (xxxx) First Order Rate Constant BiomarkerType: -- First Order Rate Constant Modeled Area Length 1000 (ft) 1,4-Dioxane 0.000 (per year) --Select Type-- DXMO -- (per year) 1,4-Dioxane�(per year) Distance from Source to Receptor 500 (ft) Preliminary plume rate estimates can be pulled from Enter Biomarker prmA (per year) 6b or 6c. Change to better Data RMO -- (per year) match field conditions or site Reset RDEG -- (per year) knowledge. Total (per year) Toggle Automatic RUN _J Recalculation: Plots Below Complex Model Select Model Page Currently OFF i L _J L Plots below can be edited. For model output data used in the plots below, see cell B47 in the "Complex" model. 1,4-Dioxane Modeled Concentrations in 2023 —1,4 Dioxane ■ Field Data ----- Receptor — — Criteria (ug/Q 1,000. f — t — t - RMSE = 0.219 r t ■ 100. ; r c o — r t t m 10. r c r t w c U , t 1. r _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ t r 0.1 t 0 100 200 300 400 500 600 700 800 900 1,000 Distance from Source (feet) RMSE: Root Mean Square Error. The lower the number, the better fit between the model and the field data. The number is the typical error between a measured point and the model results.