Purpose of Statistical Analysis Summary Report

Transcription

1 Purpose of Statistical Analysis Summary Report During the initial phase of ground water monitoring, the CCR rule requires AEP to collect at least eight independent samples from at least one up-gradient and three downgradient wells for 21 substances listed in the CCR rule. The CCR rule also requires us to select a statistical method that will be used to evaluate the samples in the later phases of the ground water monitoring program. The Statistical Plan, which has been posted to AEP s CCR website, describes the methods selected by AEP. See AEP s Statistical Analysis Plans. Each Statistical Analysis Summary Report is based on the results of the 8 independent samples that were collected by October 17, 217, and reported in the Annual Groundwater Monitoring Report. Using the statistical methods chosen by AEP, the samples were evaluated to eliminate outliers, determine variability and general trends in the data, and establish background values for: boron, calcium chloride, fluoride, ph, sulfate, and total dissolved solids. Appendix IV substances were evaluated for purposes of identifying outliers and understanding data trends. A subsequent sample taken during the first detection monitoring sampling event was also compared using the proper statistical methods to the background values that were established for these seven substances from the eight independent samples. A second or third re-sampling event occurred, and the results compared using the same methods. This work is reported in the memorandum included in attachment A. If confirmed, AEP will be required to enter the next phase of monitoring. The results of future sampling will be further analyzed to target any specific substances for which ongoing monitoring or potential corrective action is required.

2 STATISTICAL ANALYSIS SUMMARY LANDFILL Flint Creek Plant Gentry, Arkansas Submitted to 1 Riverside Plaza Columbus, Ohio Submitted by 15 East Wilson Bridge Road Suite 232 Worthington, Ohio 4385 January 3, 218 CHA8423

3 Statistical Analysis January 3, 218 TABLE OF CONTENTS SECTION 1 Executive Summary... ES-1 SECTION 2 Landfill Evaluation Data Validation & QA/QC Statistical Analysis Background Outlier Evaluation Establishment of Background Levels Certification by Qualified Professional Engineer Conclusions SECTION 3 References CHA Flint Creek LF Report i

4 Statistical Analysis January 3, 218 LIST OF TABLES Table 1 Table 2 Table 3 Groundwater Data Summary Outlier Analysis Summary Background Level Summary LIST OF ATTACHMENTS Attachment A Attachment B Evaluation of Detection Monitoring Data Statistical Analysis Output 217 CHA Flint Creek LF Report ii

5 Statistical Analysis January 3, 218 LIST OF ACRONYMS AND ABBREVIATIONS AEP ANOVA CCR CCV CFR EPA LFB LPL LRB NELAP PQL QA QC SSI SWFPR TDS UPL USEPA American Electric Power Analysis of Variance Coal Combustion Residuals Continuing Calibration Value Code of Federal Regulations Environmental Protection Agency Laboratory Fortified Blanks Lower Prediction Limit Laboratory Reagent Blanks National Environmental Laboratory Accreditation Program Practical Quantitation Limit Quality Assurance Quality Control Statistically Significant Increase Site-Wide False-Positive Rate Total Dissolved Solids Upper Prediction Limit United States Environmental Protection Agency 217 CHA Flint Creek LF Report iii

6 Statistical Analysis January 3, 218 SECTION 1 EXECUTIVE SUMMARY In accordance with the United States Environmental Protection Agency s (USEPA s) regulations regarding the disposal of coal combustion residuals (CCR) in landfills and surface impoundments (4 CFR , CCR rule ), groundwater monitoring has been conducted at the Class 3N Landfill, an existing CCR unit at the Flint Creek Power Plant located in Gentry, Arkansas. Ten monitoring events were completed prior to October 17, 217 to establish background concentrations for Appendix III and Appendix IV parameters under the CCR rule. Groundwater data underwent several validation tests, including those for completeness, sample tracking accuracy, transcription errors, and consistent use of measurement units. No data quality issues were identified which would impact the usability of the data. The monitoring data were submitted to Groundwater Stats Consulting, LLC for statistical analysis. The background data were reviewed for outliers, which were removed (when appropriate) prior to calculating upper prediction limits (UPLs) for each Appendix III parameter to represent background values. Oversight on the use of statistical calculations was provided by Dr. Kirk Cameron of MacStat Consulting, Ltd. A groundwater sampling event occurred on August 28 and 29, 217 at the landfill. This sampling event obtained the first sample for the 1-of-2 prediction interval statistical test used for detection monitoring. The results of this sampling event are included in this report. 217 CHA Flint Creek LF Report ES-1

7 Statistical Analysis January 3, 218 SECTION 2 LANDFILL EVALUATION 2.1 Data Validation & QA/QC During the background monitoring program, ten sets of samples were collected for analysis from each background and compliance well. A summary of data collected during background and detection monitoring sampling may be found in Table 1. Chemical analysis was completed by an analytical laboratory certified by the National Environmental Laboratory Accreditation Program (NELAP). Quality assurance and quality control (QA/QC) samples completed by the analytical laboratory included the use of laboratory reagent blanks (LRBs), continuing calibration verification (CCV) samples, and laboratory fortified blanks (LFBs). The analytical data were imported into a Microsoft Access database, where QA/QC checks were completed to assess the accuracy of sample location identification and analyte identification. Where necessary, unit conversions were applied to standardize reported units across all sampling events. Exported data files were created for use with the Sanitas v statistics software. The export was checked against the analytical data for transcription errors and completeness. No QA/QC issues were noted which would impact data usability. 2.2 Statistical Analysis The background data used to conduct the statistical analyses and the detection monitoring data are summarized in Table 1. Statistical analyses for the Landfill were conducted in accordance with the January 217 Statistical Analysis Plan (AEP, 217), except where noted below. The complete statistical analysis results are included in Attachment A. Time series plots of Appendix III and IV parameters are included in Attachment A. Mann-Kendall analyses (α =.1) were conducted to evaluate trends in the background data. The following statistically significant trends were observed: Cadmium was found to be significantly decreasing at compliance well. Calcium was found to be significantly decreasing at background well B-1B and significantly increasing at background well B-7A. Cobalt was found to be significantly decreasing at background well B-12. ph was found to be significantly decreasing at background well B-12 and at compliance well B CHA Flint Creek LF Report 2-1

8 Sulfate was found to be significantly decreasing at background well B-12. Statistical Analysis January 3, 218 Total dissolved solids (TDS) was found to be significantly decreasing at background well. No other significant increasing or decreasing trends were observed for other parameters or at other monitoring wells Background Outlier Evaluation Potential outliers were identified using Tukey s outlier test; i.e., data points were considered potential outliers if they met one of the following criteria: where: x i < x.25 3 IQR (1) or x i > x.75 3 IQR (2) x i = x.25 = x.75 = IQR = individual data point first quartile third quartile the interquartile range = x.75 x.25 Background well data were first pooled, and Tukey s outlier test was performed on the pooled dataset. For the compliance wells, Tukey s outlier test was applied individually to each compliance well. Data that were evaluated as potential outliers are summarized in Attachment A. Tukey s outlier test indicated three potential outliers, which are summarized in Table 2. Next, the data were reviewed to identify possible sources of errors or discrepancies, including data recording errors, unusual sampling conditions, laboratory quality, or inconsistent sample turbidity. The findings of this data review are summarized below. Two potential outliers were identified for reported arsenic concentrations at the compliance well. The reported concentration of.116 for the May 19, 217 sampling event was an estimated (J-flagged value) and was not removed from the dataset. The remaining two potential outliers for arsenic (.32 ) and mercury (.97 ), both collected at compliance well on September 14, 216 did not have an apparent reason for their elevated values and were removed as recommended by USEPA s Unified Guidance (USEPA, 29). The two outliers that were removed were associated with Appendix IV parameters at a compliance monitoring well; therefore, their removal did not affect the calculation of background levels presented below. 217 CHA Flint Creek LF Report 2-2

9 Statistical Analysis January 3, Establishment of Background Levels Analysis of variance (ANOVA) was conducted to determine whether spatial variation was present among the six background wells (Attachment A). ANOVA indicated significant variation among the six background wells for all Appendix III parameters. Therefore, the appropriateness of using intrawell tests was evaluated for the Appendix III parameters at Flint Creek Landfill. Intrawell tests presume that the groundwater quality in the compliance wells was not initially impacted by the CCR unit. To test this presumption, the data from the background wells were pooled and the data from each compliance well were compared to a pooled background value. Non-parametric tolerance limits were calculated using the pooled background data for the Appendix III parameters. Confidence intervals were calculated for each of the Appendix III parameters at each compliance monitoring well. If the lower confidence limit from a compliance well exceeded the upper tolerance limit for the pooled background data, it was concluded that compliance groundwater concentrations were above background concentrations. In these instances, intrawell tests would not be appropriate. However, these analyses indicated no significant exceedances for calcium, chloride, fluoride, ph, sulfate, and TDS; elevated concentrations of boron were observed. Therefore, intrawell tests were used to evaluate potential statistically significant increases (SSIs) for calcium, chloride, fluoride, ph, sulfate, and TDS. Nonparametric interwell tests were used to evaluate potential SSIs for boron. After equality of variance was tested and identified outliers were removed (where appropriate), a parametric or non-parametric analysis was selected based on the distribution of the data and the frequency of non-detect data. Estimated results less than the practical quantitation limit (PQL) i.e., J-flagged data were considered detections and the estimated results were used in the statistical analyses. Non-parametric analyses were selected for datasets with at least 5% nondetect data or datasets that could not be normalized. Parametric analyses were selected for datasets (either transformed or untransformed) that passed the Shapiro-Wilk / Shapiro-Francía test for normality. The Kaplan-Meier non-detect adjustment was applied to datasets with between 15% and 5% non-detect data. For datasets with fewer than 15% non-detect data, non-detect data were replaced with one half of the PQL. The selected analysis (i.e., parametric or non-parametric) and transformation (where applicable) for each background dataset are shown in Attachment A. Upper prediction limits (UPLs) were calculated for each Appendix III parameter to represent background values. A lower prediction limit (LPL) was also calculated for ph. To conduct the intrawell tests for calcium, chloride, fluoride, ph, sulfate, and TDS, a separate UPL was calculated for each compliance well for each of these parameters. To conduct the interwell tests for boron, a single prediction interval was calculated for each of these parameters using pooled data from the six background wells. The background data used for the UPL calculations are summarized in Table 1; the calculated UPLs are summarized in Table 3. Although a significant decreasing trend in ph was observed at compliance well B-1, the UPL was calculated as if no trend were present; i.e., the dataset was not limited to more recent data nor 217 CHA Flint Creek LF Report 2-3

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11 Statistical Analysis January 3, Conclusions Ten background monitoring events and one detection monitoring event were completed in accordance with the CCR Rules. The laboratory and field data were reviewed prior to statistical analysis, with no QA/QC issues identified that impacted data usability. A review of outliers identified three potential outliers, with two values removed from the dataset without replacement. Prediction intervals were constructed based on the remaining background data and a one-of-two retesting procedure. Intrawell tests were selected for calcium, chloride, fluoride, ph, sulfate, and TDS, whereas interwell tests were selected for boron. 217 CHA Flint Creek LF Report 2-5

12 Statistical Analysis January 3, 218 SECTION 3 REFERENCES American Electric Power (AEP) Statistical Analysis Plan Flint Creek Plant. January 217. United States Environmental Protection Agency (USEPA). 29. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities Unified Guidance. EPA 53/R-9-7. March CHA Flint Creek LF Report 3-1

13 TABLES

14 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-1B Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/29/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U.127J <.93U <.93U Arsenic <.15U <.15U <.15U <.15U <.15U.1268J <.15U <.15U <.15U.143J - Barium Beryllium.48J.36J <.2U.37J.33J.22J <.2U.4J.3J <.2U - Boron Cadmium <.7U <.7U <.7U <.7U.77J <.7U <.7U <.7U <.7U <.7U - Calcium Chloride Chromium.81J.612J.1.985J.2.1 <.23U.85J.3J.33J - Cobalt.442J.527J.454J.75J.917J.385J.325J.49J.49J.47J - Combined Radium pci/l Fluoride.5955J.4424J.487J.4557J <.83U <.83U <.83U.53J.4551J <.83U.416J Lead <.68U.135J.1J.135J.136J <.68U <.68U <.68U <.68U <.68U - Lithium Mercury.23J.18J <.5U <.5U.6J.8J <.5U <.5U.9J <.5U - Molybdenum.212J.87J.613J <.29U.298J.645J.562J <.29U <.29U <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

15 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/29/217 Background Detection Antimony <.93U <.93U.1816J <.93U.1152J.1321J.6 <.93U.117J <.93U - Arsenic <.15U <.15U.8 <.15U J <.15U.139J.177J.18J - Barium Beryllium.131J.297J.1.169J.3.764J.158J.22J.17J.17J - Boron Cadmium <.7U <.7U.348J <.7U.87J <.7U <.7U.8J <.7U.9J - Calcium Chloride Chromium Cobalt.952J.2189J J J.124J.47J.167J - Combined Radium pci/l Fluoride <.83U.3361J <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U Lead <.68U.198J J J <.68U.132J.8J.8J - Lithium Mercury.21J.9J.27 <.5U.5.13J <.5U <.5U <.5U <.5U - Molybdenum J.2597J.784J.2692J.833J.478J.77J.34J.21J - Selenium Total Dissolved Solids Sulfate Thallium <.86U <.86U.989J <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

16 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-4 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/29/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U.2636J.195J <.93U <.93U.452J - Arsenic <.15U <.15U <.15U <.15U.1758J <.15U <.15U <.15U <.15U.118J - Barium Beryllium.25J.212J.38J.44J.382J.21J.242J.8J.9J.22J - Boron Cadmium <.7U <.7U <.7U <.7U.131J <.7U <.7U <.7U <.7U.8J - Calcium Chloride Chromium J.99J.82J - Cobalt.37J.15J.414J.2342J.1228J.749J.65J.28J <.14U.19J - Combined Radium pci/l Fluoride <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U Lead <.68U <.68U.1166J.1657J.943J <.68U <.68U.87J <.68U <.68U - Lithium <.13U J.77J Mercury.15J.7J <.5U <.5U.8J <.5U <.5U <.5U.5J <.5U - Molybdenum <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U.111J <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U.919J <.86U <.86U <.86U <.86U <.86U <.86U.9J - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

17 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-5 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/29/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U.124J <.93U <.93U - Arsenic <.15U.195J <.15U <.15U <.15U <.15U <.15U.187J.116J <.15U - Barium Beryllium.538J.578J.422J.78J.557J.635J.548J.56J.65J.6J - Boron Cadmium.131J <.7U.18J.94J.1.137J <.7U.15J.8J.7J - Calcium Chloride Chromium Cobalt.635J.67J.632J.2247J.962J.1126J.62J.92J.84J.63J - Combined Radium pci/l Fluoride <.83U <.83U <.83U.2728J <.83U <.83U <.83U <.83U <.83U <.83U <.83U Lead <.68U.951J <.68U.2222J <.68U <.68U <.68U <.68U <.68U <.68U - Lithium.323J Mercury.35.13J.11J.49.21J.53.14J.13J.13J.8J - Molybdenum <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U - Selenium Total Dissolved Solids Sulfate Thallium.178J <.86U <.86U <.86U <.86U.121J <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

18 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-6 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U - Arsenic <.15U <.15U <.15U.3636J <.15U <.15U <.15U.189J.149J.15J - Barium Beryllium.33J.169J <.2U.559J.135J.217J.141J.26J.12J.16J - Boron Cadmium <.7U <.7U <.7U.268J.117J <.7U <.7U.16J <.7U <.7U - Calcium Chloride Chromium Cobalt.534J.1235J.1266J.4751J.1683J.2574J.1957J.274J.116J.158J - Combined Radium pci/l Fluoride <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U.266J Lead <.68U.849J.1531J.47J.173J.131J.2182J.244J.116J.13J - Lithium.846J Mercury.12J.1J <.5U.13J.12J.8J.7J.8J <.5U <.5U - Molybdenum <.29U.864J <.29U.732J <.29U.868J.329J.62J.43J.5J - Selenium.1384J.333J.3351J.34J.222J.1164J.139J.45J.14J <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U.116J - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

19 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-7A Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U - Arsenic <.15U.1332J <.15U <.15U.114J <.15U <.15U <.15U.125J <.15U - Barium Beryllium <.2U.76J <.2U <.2U <.2U <.2U <.2U <.2U <.2U <.2U - Boron Cadmium <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U - Calcium Chloride Chromium <.23U.241J.354J <.23U.282J <.23U.433J <.23U.24J <.23U - Cobalt.649J.345J.395J.843J.667J.353J.458J.64J.56J.43J - Combined Radium pci/l Fluoride <.83U.3892J <.83U.3235J <.83U <.83U <.83U <.83U <.83U <.83U.274J Lead <.68U.791J <.68U <.68U <.68U <.68U <.68U <.68U <.68U.174J - Lithium Mercury J <.5U.7J <.5U.6J <.5U.8J <.5U - Molybdenum.838J.62J.477J.68J <.29U <.29U <.29U <.29U <.29U <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U - Total Dissolved Solids Sulfate Thallium <.86U.1985J <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

20 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-9 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U.1391J <.93U <.93U <.93U - Arsenic <.15U <.15U <.15U <.15U <.15U <.15U <.15U.113J.168J.111J - Barium Beryllium.48J.71J <.2U <.2U.2J.33J <.2U <.2U.3J.4J - Boron.1.947J.7119J.7681J J Cadmium <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U <.7U - Calcium Chloride Chromium Cobalt.649J.52J.134J.1782J.1482J.1219J.887J.93J.83J.132J - Combined Radium pci/l Fluoride <.83U.3556J <.83U.1884J <.83U <.83U <.83U.31J <.83U <.83U.2389J Lead <.68U.756J <.68U.693J <.68U <.68U <.68U.79J <.68U <.68U - Lithium Mercury.15J.14J <.5U <.5U.8J <.5U <.5U <.5U <.5U <.5U - Molybdenum.872J <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U - Total Dissolved Solids Sulfate Thallium.1516J.144J <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

21 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-1 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U - Arsenic <.15U <.15U.1736J <.15U.6 <.15U <.15U.15J <.15U <.15U - Barium Beryllium.28J.51J <.2U <.2U.35J.49J <.2U <.2U <.2U <.2U - Boron Cadmium <.7U <.7U <.7U <.7U.413J <.7U <.7U <.7U <.7U <.7U - Calcium Chloride Chromium J.59J.39J - Cobalt.568J.487J.1459J.617J.5.121J.815J.65J.76J.117J - Combined Radium pci/l Fluoride <.83U <.83U <.83U.2319J <.83U <.83U <.83U.3J <.83U <.83U.334J Lead <.68U <.68U.1566J <.68U.2578J <.68U <.68U <.68U <.68U <.68U - Lithium Mercury.18J.23J <.5U <.5U.15J <.5U <.5U <.5U <.5U <.5U - Molybdenum.177J <.29U.46J.982J.1182J.1261J.122J.92J.155J.128J - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

22 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U - Arsenic <.15U J <.15U <.15U <.15U <.15U.116J <.15U - Barium Beryllium.9J J.136J.249J.38J.39J.41J - Boron Cadmium J.418J.478J.56J.15J.13J - Calcium Chloride Chromium Cobalt.3285J J.824J.287J.554J.124J.97J.18J - Combined Radium pci/l Fluoride <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U <.83U Lead.4234J <.68U <.68U <.68U.83J <.68U.123J - Lithium Mercury.25J.24J.97 <.5U <.5U <.5U <.5U <.5U <.5U <.5U - Molybdenum.362J.59J.3326J.371J <.29U <.29U <.29U <.29U <.29U <.29U - Selenium <.99U.1896J <.99U.1955J <.99U <.99U.272J.152J.268J.115J - Total Dissolved Solids Sulfate Thallium <.86U <.86U.11J <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

23 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-12 Parameter Unit 5/24/216 7/19/216 9/14/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/29/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U.192J <.93U <.93U - Arsenic <.15U <.15U <.15U <.15U.8 <.15U <.15U.123J.165J <.15U - Barium Beryllium.2J.84J <.2U <.2U.1 <.2U <.2U.2J.7J <.2U - Boron Cadmium <.7U <.7U <.7U <.7U.465J <.7U <.7U <.7U <.7U <.7U - Calcium Chloride Chromium.981J J J.1.65J J - Cobalt.3362J.2846J.2534J.2315J J.162J.134J.195J.13J - Combined Radium pci/l Fluoride <.83U <.83U <.83U.198J <.83U <.83U <.83U <.83U <.83U <.83U <.83U Lead.78J.1174J.716J <.68U.15 <.68U.93J <.68U.77J <.68U - Lithium.759J.1.875J J J - Mercury.17J.22J <.5U <.5U.39 <.5U <.5U.6J <.5U <.5U - Molybdenum.2949J.3868J.3272J.29J.4655J.1144J.268J.69J.58J <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

24 Table 1 - Groundwater Data Summary Flint Creek Plant - Landfill B-13 Parameter Unit 5/24/216 7/19/216 9/13/216 1/5/216 11/8/216 1/24/217 3/7/217 4/26/217 5/16/217 6/16/217 8/28/217 Background Detection Antimony <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U <.93U - Arsenic <.15U <.15U <.15U <.15U <.15U <.15U <.15U.192J <.15U <.15U - Barium Beryllium.123J.224J <.2U.238J.285J.293J.142J.22J.13J.12J - Boron Cadmium.18J <.7U <.7U <.7U.256J <.7U <.7U.1J <.7U <.7U - Calcium Chloride Chromium Cobalt.1818J.161J.1452J.2785J.152J.1481J.77J.194J.99J.126J - Combined Radium pci/l Fluoride <.83U <.83U <.83U <.83U.2121J <.83U <.83U <.83U <.83U <.83U <.83U Lead <.68U.135J <.68U.1814J.1588J <.68U <.68U.12J <.68U <.68U - Lithium <.13U Mercury.22J.14J <.5U <.5U.8J <.5U <.5U.21J <.5U <.5U - Molybdenum <.29U <.29U <.29U.539J <.29U <.29U <.29U <.29U <.29U <.29U - Selenium <.99U <.99U <.99U <.99U <.99U <.99U <.99U.168J.138J <.99U - Total Dissolved Solids Sulfate Thallium <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U <.86U - ph SU Notes: : milligrams per liter pci/l: picocuries per liter SU: standard unit U: Component was not present in concentrations above method detection limit and is reported as the reporting limit J: Estimated value. Component was detected in concentrations below the reporting limit -: Not sampled Geosyntec Consultants, Inc.

25 Table 2: Outlier Analysis Summary Flint Creek Landfill Geosyntec Consultants, Inc. Location Well ID Sample Date Parameter Reported Value Units Conclusions Compliance 9/14/216 Arsenic.32 This value was removed from the dataset. Its removal did not affect the calculation of background values Compliance 5/19/217 Arsenic.116 J This value was estimated (J-flagged) and was not removed from the dataset. Compliance 9/14/216 Mercury.97 This value was removed from the dataset. Its removal did not affect the calculation of background values

26 Table 3: Background Level Summary Flint Creek Plant - Landfill Geosyntec Consultants, Inc. Parameter Unit Description B-6 B-9 B-1 Boron Interwell Background Value (UPL).588 Calcium Intrawell Background Value (UPL) Chloride Intrawell Background Value (UPL) Fluoride Intrawell Background Value (UPL) ph SU Intrawell Background Value (UPL) SU Intrawell Background Value (LPL) Total Dissolved Solids Intrawell Background Value (UPL) Sulfate Intrawell Background Value (UPL) Notes: UPL: Upper prediction limit LPL: Lower prediction limit

27 ATTACHMENT A Evaluation of Detection Monitoring Data

28 15 E.Wilson Bridge Road, Suite 232 Columbus, Ohio 4385 PH FAX Memorandum Date: February 26, 218 To: Copies to: From: Subject: David Miller (AEP) Terence Wehling (AEP) Allison Kreinberg and Bruce Sass, Ph.D. (Geosyntec) Evaluation of Detection Monitoring Data at Flint Creek Plant s Landfill (LF) In accordance with the United States Environmental Protection Agency s (USEPA s) regulations regarding the disposal of coal combustion residuals (CCR) in landfills and surface impoundments (4 CFR , CCR rule ), detection monitoring events were completed on August 28-29, 217 and December 21, 217 at the Landfill (LF), an existing CCR unit at the Flint Creek Power Plant located in Gentry, Arkansas. Ten background monitoring events were conducted at the Flint Creek LF prior to these detection monitoring events, and upper prediction limits (UPLs) were calculated for each Appendix III parameter to represent background values. A lower prediction limit (LPL) was also calculated for ph. Details on the calculation of these background values are described in Geosyntec s Statistical Analysis Summary report, dated January 3, 218. To achieve an acceptably high statistical power while maintaining a site-wide false-positive rate (SWFPR) of 1% per year or less, prediction limits were calculated based on a one-of-two retesting procedure. With this procedure, a statistically significant increase (SSI) is only concluded if both samples in a series of two exceeds the UPL. In practice, if the initial result did not exceed the UPL, a second sample was not collected or analyzed. Detection monitoring results and the relevant background values are summarized in Table 1-B. Boron concentrations exceeded the interwell UPL of.588 in both the initial (1.7 ) and second (.7 ) samples collected at, both the initial (.62 ) and second (.65 ) samples collected at B-6, and both the initial (.266 ) and second (.227 ) samples collected at. Therefore, an SSI over background is concluded for boron at, B-6 and B- 11. CHA Flint Creek LF Addendum Memo

29 Evaluation of Detection Monitoring Data Flint Creek LF February 26, 218 Page 2 As a result, the Flint Creek LF CCR unit will conduct an alternate source demonstration. No other exceedances of UPLs were observed during these detection monitoring events. The following modifications to Geosyntec s Statistical Analysis Summary report were incorporated after the certification date of January 3, 218: Table 1 ( Groundwater Data Summary ) was revised to reflect appropriate significant digits for estimated (J-flagged) values; and, Figure E ( Analysis of Variance ) of Attachment A ( Statistical Analysis Output ) was revised to correct a formatting error. ***** CHA Flint Creek LF Addendum Memo

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31 Table 1-B: Detection Monitoring Data Evaluation Flint Creek Plant - Landfill Geosyntec Consultants, Inc. Parameter Units Description B-6 B-9 B-1 8/29/217 12/21/217 8/28/217 12/21/217 8/28/217 8/28/217 8/28/217 12/21/217 Boron Calcium Chloride Fluoride Interwell Background Value (UPL).59 Detection Monitoring Result Intrawell Background Value (UPL) Detection Monitoring Result Intrawell Background Value (UPL) Detection Monitoring Result Intrawell Background Value (UPL) Detection Monitoring Result SU Intrawell Background Value (UPL) ph SU Intrawell Background Value (LPL) SU Detection Monitoring Result Total Dissolved Solids Intrawell Background Value (UPL) Detection Monitoring Result Sulfate Intrawell Background Value (UPL) Detection Monitoring Result Notes: UPL: Upper prediction limit LPL: Lower prediction limit --: not sampled Bold values exceed the background value. Background values are shaded gray.

32 ATTACHMENT B Statistical Analysis Output

33 GROUNDWATER STATS CONSULTING November 9, 217 Geosyntec Consultants Attn: Mr. Bruce Sass 15 E. Wilson Bridge Rd., #232 Worthington, OH 4385 Dear Mr. Sass, Groundwater Stats Consulting, formerly the statistical consulting division of Sanitas Technologies, is pleased to provide the screening and statistical analysis of background groundwater data for American Electric Power s Flint Creek Landfill. The analysis complies with the federal rule for the Disposal of Coal Combustion Residuals from Electric Utilities (CCR Rule, 215) as well as with the USEPA Unified Guidance (29). Sampling began at Flint Creek Landfill for the CCR program in 216, and 8 background samples have been collected at each of the groundwater monitoring wells. The monitoring well network, as provided by Geosyntec Consultants, consists of the following: upgradient wells B-1B, B-4, B-5, B-7A, B-12, and B-13; and downgradient wells, B-6, B-9, B-1, and. Data were sent electronically to Groundwater Stats Consulting, and the statistical analysis was reviewed by Dr. Kirk Cameron, PhD Statistician with MacStat Consulting, primary author of the USEPA Unified Guidance, and Senior Advisor to Groundwater Stats Consulting. The following constituents were evaluated: Appendix III parameters boron, calcium, chloride, fluoride, ph, sulfate, and TDS; and Appendix IV parameters - antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, combined radium 226 & 228, fluoride, lead, lithium, mercury, molybdenum, selenium, and thallium. Time series plots for Appendix III and IV parameters at all wells are provided for the purpose of screening data at these wells (Figure A). Additionally, box plots are included for all constituents at upgradient and downgradient wells (Figure B). The time series plots are used to initially screen for suspected outliers and trends, while the box plots provide visual representation of variation within individual wells and between all wells. Data at all wells were evaluated for the following: 1) outliers; 2) trends; 3) most appropriate statistical method for Appendix III parameters based on site characteristics of groundwater data upgradient of the facility; and 4) eligibility of downgradient wells when intrawell statistical methods are recommended. Power Groundwater Stats Consulting ph:

34 curves are provided to demonstrate that the selected statistical methods for Appendix III parameters comply with the USEPA Unified Guidance recommendations as discussed below. Summary of Statistical Method: 1) Intrawell prediction limits, combined with a 1-of-2 resample plan for calcium, chloride; fluoride, ph, sulfate, and TDS; and 2) Interwell prediction limits combined with a 1-of-2 resample plan for boron. Parametric prediction limits are utilized when the screened historical data follow a normal or transformednormal distribution. When data cannot be normalized or the majority of data are nondetects, a nonparametric test is utilized. The distribution of data is tested using the Shapiro-Wilk/Shapiro-Francia test for normality. After testing for normality and performing any adjustments as discussed below (US EPA, 29), data are analyzed using either parametric or non-parametric prediction limits. No statistical analyses are required on wells and analytes containing 1% nondetects (USEPA Unified Guidance, 29, Chapter 6). When data contain <15% nondetects in background, simple substitution of one-half the reporting limit is utilized in the statistical analysis. The reporting limit utilized for nondetects is the practical quantification limit (PQL) as reported by the laboratory. When data contain between 15-5% nondetects, the Kaplan-Meier nondetect adjustment is applied to the background data. This technique adjusts the mean and standard deviation of the historical concentrations to account for concentrations below the reporting limit. Nonparametric prediction limits are used on data containing greater than 5% nondetects. Background Screening Outlier Evaluation Time series plots are used to identify suspected outliers, or extreme values that would result in limits that are not conservative from a regulatory perspective, in proposed background data. Suspected outliers at all wells for Appendix III and Appendix IV parameters were formally tested using Tukey s box plot method and, when identified, flagged in the computer database with o and deselected prior to construction of statistical limits (Figure C). Tukey s outlier test noted a few outliers as may be seen on the Outlier Summary Table and accompanying graphs. Any values flagged as outliers are plotted in a lighter font on the time series graph. A substitution of the most recent reporting limit was applied when varying detection limits existed in data. No true seasonal patterns were observed on the time series plots for any of the detected data; therefore, no deseasonalizing adjustments were made to the data. When seasonal patterns are observed, data may be deseasonalized so that the resulting limits will correctly account for the seasonality as a predictable pattern rather than random variation or a release. Groundwater Stats Consulting ph:

35 While trends may be visual, a quantification of the trend and its significance is needed. The Sen s Slope/Mann Kendall trend test was used to evaluate all data at each well to identify statistically significant increasing or decreasing trends (Figure D). In the absence of suspected contamination, significant trending data are typically not included as part of the background data used for construction of prediction limits. This step serves to eliminate the trend and, thus, reduce variation in background. When statistically significant decreasing trends are present, earlier data are evaluated to determine whether earlier concentration levels are significantly different than current reported concentrations and will be deselected as necessary. When the historical records of data are truncated for the reasons above, a summary report will be provided to show the date ranges used in construction of the statistical limits. The results of the trend analyses showed several statistically significant decreasing trends and one increasing trend for calcium in an upgradient well, as may be seen on the Trend Test Summary Table that accompanies the trend tests. These trends were relatively low in magnitude when compared to average concentrations; therefore, no adjustments were made to the data sets. Appendix III Determination of Spatial Variation The Analysis of Variance (ANOVA) was used to statistically evaluate differences in average concentrations among upgradient wells, which assists in identifying the most appropriate statistical approach (Figure E). Interwell tests, which compare downgradient well data to statistical limits constructed from pooled upgradient well data, are appropriate when average concentrations are similar across upgradient wells. Intrawell tests, which compare compliance data from a single well to screened historical data within the same well, are appropriate when upgradient wells exhibit spatial variation; when statistical limits constructed from upgradient wells would not be conservative from a regulatory perspective; and when downgradient water quality is unimpacted compared to upgradient water quality for the same parameter. The ANOVA identified variation for all Appendix III parameters; therefore, these data were further evaluated as described for the appropriateness of intrawell testing to accommodate the groundwater quality. A summary table of the ANOVA results is included with the reports. Appendix III - Statistical Limits Intrawell limits constructed from carefully screened background data from within each well serve to provide statistical limits that are conservative (i.e. lower) from a regulatory perspective, and that will rapidly identify a change in more recent compliance data from within a given well. This statistical method removes the element of variation from across wells and eliminates the chance of mistaking natural spatial variation for a release from the facility. Prior to performing intrawell prediction limits, several steps are required to reasonably demonstrate downgradient water quality does not have existing impacts from the practices of the facility. Exploratory data analysis was used as a general comparison of concentrations in downgradient wells for all Appendix III parameters recommended for intrawell analyses to concentrations reported in upgradient wells. Upper tolerance limits are used in conjunction with confidence intervals to determine whether the estimated averages in downgradient wells are higher than observed levels upgradient of the facility. The upper tolerance limits were constructed to represent the extreme upper range of possible background levels at the site. Groundwater Stats Consulting ph:

36 In cases where downgradient average concentrations are higher than observed concentrations upgradient for a given constituent, an independent study and hydrogeological investigation would be required to identify local geochemical conditions and expected groundwater quality for the region to justify an intrawell approach. Such an assessment is beyond the scope of services provided by Groundwater Stats Consulting. When there is not an obvious explanation for observed concentration differences in downgradient wells relative to reported concentrations in upgradient wells, interwell prediction limits will initially be selected for the statistical method until further evidence shows that concentrations are due to natural variation rather than a result of the facility. Parametric tolerance limits were constructed with a target of 99% confidence and 95% coverage using pooled upgradient well data for each of the Appendix III parameters(figure F). The confidence and coverage levels for nonparametric tolerance limits are dependent upon the number of background samples. As more data are collected, the background population is better represented and the confidence and coverage levels increase. Confidence intervals were constructed on downgradient wells for each of the Appendix III parameters, using the tolerance limits discussed above, to determine intrawell eligibility (Figure G). When the entire confidence interval is above a background standard for a given parameter, interwell methods are initially recommended as the statistical method. Therefore, only parameters with confidence intervals which did not exceed background standards are eligible for intrawell prediction limits. Confidence intervals for the above parameters were found to be within their respective background limit for all Appendix III parameters with the exception of boron. Therefore, intrawell methods are recommended for calcium, chloride, fluoride, ph, sulfate and TDS; and interwell methods are recommended initially for boron. As mentioned earlier, if a demonstration supports natural variation in groundwater, intrawell methods will be considered for all parameters. All available data through June 217 at each well were used to establish intrawell background limits based on a 1-of-2 resample plan that will be used for future comparisons (Figure H). Interwell prediction limits, combined with a 1-of-2 resample plan, were constructed from upgradient wells for boron (Figure I). Downgradient measurements will be compared to these background limits during each subsequent semiannual sampling event. Natural systems continuously evolve due to physical changes made to the environment. Examples include capping a landfill, paving areas near a well, or lining a drainage channel to prevent erosion. Periodic updating of background statistical limits will be necessary to accommodate these types of changes In the interwell case, newer data will be included in background when a minimum of 2 new samples are available. In the intrawell case, data for all wells and constituents are re-evaluated when a minimum of 4 new data points are available to determine whether earlier concentrations are representative of present-day groundwater quality. In some cases, the earlier portion of data are deselected prior to construction of limits in order to provide sensitive limits that will rapidly detect changes in groundwater quality. Even though the data are excluded from the calculation, the values will continue to be reported and shown in tables and graphs. Groundwater Stats Consulting ph: