Ash Monofill Annual Groundwater Monitoring and Corrective ......The Ash Monofill is constructed...

Ash Monofill Annual Groundwater Monitoring and Corrective Action Report for 2018

Revision 0Rawhide Energy StationLaramie County, Colorado

Platte River Power Authority

Project Number: 60569963

January 31, 2019

Environment Submitted to: Submitted by:Platte River Power Authority AECOMFort Collins, CO Greenwood Village, CO

60514655January 31, 2019

Platte River Power Authority Ash MonofillAnnual Groundwater Monitoring andCorrective Action Report for 2018

Revision 0

_________________________________Prepared ByRichard HenryPrincipal Hydrogeologist

_________________________________Reviewed ByGregg SomermeyerProgram Manager

_________________________________Approved ByGeoff WebbSenior Project Manager

AECOM Environment i

PRPA Ash Monofill Annual Report for 2018 January 2019

List of Acronyms

AECOM AECOM Technical Services, Inc.

APHA American Public Health Association

ASD alternate source demonstration

AWWA American Water Works Association

Ba barium

bgs below ground surface

BNSF Burlington Northern Santa Fe Railway Company

CCR Coal Combustion Residuals

CFR Code of Federal Regulations

DO dissolved oxygen

EROP Engineering Report and Operational Plan

ft feet

ft/d feet/day

GWPS groundwater protection standard

i.d. inner diameter

LCL lower confidence limit

LPL lower prediction limit

MS/MSD matrix spike/matrix spike duplicate sample

NTUs nephelometric turbidity units

ORP oxidation reduction potential

PRPA Platte River Power Authority

PVC polyvinyl chloride

QA/QC Quality assurance and quality control

Se selenium

SSI statistically significant increase

SSL statistically significant level

TDS total dissolved solids

UPL upper prediction limit

AECOM Environment i


Contents

1.0 Introduction .......................................................................................................................... 1-1

1.1 Report Organization ..................................................................................................... 1-1

2.0 Facility Description ............................................................................................................... 2-1

2.1 Facility Location and Operational History ....................................................................... 2-1

2.2 Ash Monofill Description ............................................................................................... 2-1

2.3 Rawhide Station Hydrogeology ..................................................................................... 2-1

2.4 Ash Monofill Hydrogeology ........................................................................................... 2-1

3.0 Appendix III Alternate Source Demonstration ...................................................................... 3-1

3.1 Alternate Source Demonstration Findings ..................................................................... 3-1

3.2 Initiation of Assessment Monitoring ............................................................................... 3-1

4.0 Groundwater Monitoring Activities in 2018 .......................................................................... 4-1

4.1 Modified Groundwater Monitoring Well System Installation ............................................ 4-1

4.2 Monitoring Well Development ....................................................................................... 4-2

4.3 Surveying .................................................................................................................... 4-2

4.4 Well Hydraulic Testing .................................................................................................. 4-2

4.5 Water Level Measurements .......................................................................................... 4-2

4.6 Groundwater Sample Collection.................................................................................... 4-3

4.7 Analytical Program ....................................................................................................... 4-3

4.8 Quality Control/Quality Assurance ................................................................................. 4-3

4.9 Data Validation............................................................................................................. 4-3

5.0 Monitoring Results and Evaluation ...................................................................................... 5-1

5.1 Groundwater Potentiometric Surface............................................................................. 5-1

5.2 Groundwater Flow ........................................................................................................ 5-1

5.3 Groundwater Analytical Results .................................................................................... 5-1

5.4 Groundwater Monitoring System Evaluation .................................................................. 5-1

5.5 Problems Encountered and Actions Taken .................................................................... 5-2

6.0 Statistical Analysis Results .................................................................................................. 6-1

6.1 Appendix III SSI Determination ..................................................................................... 6-1

6.2 Appendix IV SSI Determination ..................................................................................... 6-1

6.3 Establishment of Groundwater Protection Standards ..................................................... 6-1

AECOM Environment ii


6.4 Appendix IV SSL Determination .................................................................................... 6-2

7.0 Projected Activities in 2019 .................................................................................................. 7-1

8.0 Summary and Findings ........................................................................................................ 8-1

9.0 References ............................................................................................................................ 9-1

List of Tables

Table 1 Ash Monofill Monitoring Well Construction Details

Table 2 Ash Monofill Water Level Measurements 2018

Table 3 Ash Monofill Analytical Results June 2018

Table 4 Ash Monofill Analytical Results October 2018

Table 5 Ash Monofill Appendix III Background Upper Prediction Limits

Table 6 Ash Monofill Appendix IV Background Upper Prediction Limits

Table 7 Ash Monofill Appendix IV Statistical Analysis Results

List of Figures

Figure 1 Ash Monofill Monitoring Well Network

Figure 2 Ash Monofill June 2018 Potentiometric Surface Map

Figure 3 Ash Monofill October 2018 Potentiometric Surface Map

List of Appendices

Appendix A Monitoring Well Boring Logs and Well Construction Diagrams

Appendix B Well Development Forms

Appendix C Groundwater Sampling Forms

Appendix D Laboratory Analytical Reports and Data Validation Reports

Appendix E Statistical Analysis Results

Appendix F Modified Groundwater Monitoring Well Network Certification

Appendix G Ash Monofill Appendix III Alternate Source Demonstration

AECOM Environment 1-1


1.0 Introduction

This is the 2018 Annual Groundwater Monitoring and Corrective Action Report for the Coal CombustionResiduals (CCR) Ash Monofill at the Platte River Power Authority (PRPA) Rawhide Energy Station(Rawhide Station or Site) in Larimer County, Colorado. This report was developed by AECOM TechnicalServices, Inc. (AECOM) at the request of PRPA. The purpose of this report is to provide a summary ofthe groundwater monitoring activities performed at the Ash Monofill in 2018 to comply with therequirements of Title 40 of the Code of Federal Regulations (CFR) Part 257 Subpart D, known as theCCR Rule, which became effective on October 19, 2015. The rule provides standards for the disposal ofCCR in landfills and surface impoundments (CCR units) and establishes groundwater monitoringrequirements in 40 CFR 257.90 through 257.94. In accordance with 40 CFR 257.90(e), an annual reportmust document the status of the groundwater monitoring and correction action program (as applicable)for the CCR unit, summarize the key actions completed the previous year, describe any problemsencountered, discuss actions taken to resolve the problems, and project key activities for the upcomingyear. The annual report will be considered complete when it is placed in the facility operating record byJanuary 31, 2019.

1.1 Report Organization

This Annual Report is divided into nine sections as outlined below and includes text, tables, figures, andappendices. The sections include:

· Section 1.0 includes this introduction and report organization;

· Section 2.0 provides a facility description that includes the facility location and operationalhistory, a description of the CCR unit and a summary of the areal and site hydrogeology;

· Section 3.0 summarizes the results of the alternate source demonstration (ASD) performed forthe Appendix III constituents;

· Section 4.0 summarizes the groundwater monitoring and corrective action activities performed in2018, and references appendices to this report that contain detailed documentation of thoseactivities;

· Section 5.0 summarizes the groundwater sampling and analysis results;

· Section 6.0 provides the statistical analyses and results;

· Section 7.0 provides a projection of the key activities anticipated in 2019;

· Section 8.0 provides a summary of findings; and

· Section 9.0 provides a list of references cited in the report.

The report also includes seven appendices that provide supporting documentation of the groundwatermonitoring and related activities conducted in 2018 that include:

· Appendix A Monitoring Well Boring Logs and Well Completion Diagrams

· Appendix B Well Development Forms

· Appendix C Groundwater Sampling Forms

· Appendix D Laboratory Analytical and Data Validation Reports

· Appendix E Statistical Analysis Results

· Appendix F Modified Groundwater Monitoring Well Network Certification

· Appendix G Ash Monofill Appendix III Alternate Source Demonstration



2.0 Facility Description

2.1 Facility Location and Operational History

The Rawhide Station encompasses approximately 4,560 acres north of Wellington in Larimer County,Colorado. In addition to the plant buildings, the major feature of the facility is an approximately 500acre dry-land construction reservoir of reclaimed wastewater from the City of Fort Collins, also knownas Hamilton Reservoir, which contains approximately 15,000 acre-feet of water and is used for coolingprocesses. The power block area contains the boiler and turbine buildings, the air quality controlequipment, and the administrative offices. A rail spur along the northern edge of the Site connects theRawhide Facility with the mainline of the Burlington Northern Santa Fe Railway Company (BNSF)Railway Company and is used to deliver coal and construction materials for plant operations. Sixgenerating units are located at the Rawhide Station. Units A, B, C, D, and F are fueled by natural gas,and Unit 1 is fueled by coal from the Powder River Basin in Wyoming.

2.2 Ash Monofill Description

The Ash Monofill is located northwest of the main plant and north of Hamilton Reservoir. CCR solidwaste from Unit 1 operations is disposed in the Ash Monofill which is comprised of two cells, Cell 1 andCell 2, as shown on Figure 1. Cell 1 was operated from approximately 1980 to 2007 and is no longer inuse. It is capped with cover soils but has not undergone final closure. Cell 2 is active, lies to the west ofCell 1, and is progressively advancing northwards as further ash material is placed within the cell.

2.3 Rawhide Station Hydrogeology

The hydrogeology of the Rawhide Station is discussed in the Engineering Report and OperationalPlan (EROP) for the Solid Waste Disposal Facility (PRPA, 1980), and in the Final Report Investigationof the Groundwater Monitoring Program for the Bottom Ash Disposal Site conducted by Lidstone andAnderson (1989). According to the 1980 EROP, hydrogeology of the Rawhide Station was originallyinvestigated by drilling and installing twenty-three (23) piezometers in conjunction with the originalgeotechnical investigation of the site prior to construction of the facility. Data from the piezometersindicated that a groundwater table exists within the weathered and fractured Pierre Shale bedrockbeneath the Site, and in alluvial deposits along Coal Creek. The report indicated that the depth togroundwater varied across the Site from 11 to 67 feet (ft) below ground surface (bgs), withgroundwater generally flowing to the south-southeast. The shallow water table, as explained in the1980 EROP, was reported to be directly recharged by infiltration from precipitation and surface runoff.

Following construction and operation of the Rawhide Station, Lidstone and Anderson (1989)concluded that sufficient groundwater data were collected to determine that a mound had formed inthe shallow, weathered, and fractured Pierre Shale in the vicinity of Hamilton Reservoir. After a reviewof available groundwater level information for Rawhide Station, AECOM concluded that the CCR unitspresent at the Site are located hydraulically upgradient of any groundwater mound created byHamilton Reservoir.

2.4 Ash Monofill Hydrogeology

The Ash Monofill is constructed within a narrow south-sloping valley with bedrock highs along bothsides. The uppermost water-bearing stratum at the Ash Monofill was identified during groundwatermonitoring well installation as the weathered and fractured Pierre Shale. Groundwater at the AshMonofill is under water table conditions and, in 2018, lies at depths from approximately 14 to 40 ft bgs.Groundwater flow is generally from northwest to south-southeast, from the Ash Monofill towardsHamilton Reservoir, generally following the topographic slope of the valley.



3.0 Appendix III Alternate Source Demonstration

3.1 Alternate Source Demonstration Findings

An alternate source demonstration (ASD) was performed to assess whether a source other than the AshMonofill is responsible for the statistically significant increases (SSIs) over background for Appendix IIIconstituents boron, calcium, chloride, sulfate, and total dissolved solids (TDS) at downgradientmonitoring wells ASH-03, ASH-04, and ASH-05. The ASD was completed under the Coal CombustionResiduals (CCR) Rule, 40 Code of Federal Regulations (CFR) Part 257.94. The completed ASD wascertified by a professional engineer, placed in the facility’s operating record, and is included in thisannual report as specified in 40 CFR 257.94(e)(2). A copy of the ASD is provided in Appendix G.

As specified in 40 CFR 257.94(e)(2), alternate sources for an SSI can include errors in sampling,laboratory analysis, and statistical evaluation, natural variation in groundwater quality, or ananthropogenic source. A review of these possible alternative causes for the Appendix III SSIs revealedno errors in sampling, laboratory analysis, or statistical evaluation. The review also did not find any likelynatural variations in groundwater quality or anthropogenic (agricultural or industrial) sources that causedthe SSIs. The results of the ASD suggests that the coal ash disposed in the Ash Monofill is the likelysource of the elevated concentrations of Appendix III constituents that result in the SSIs observed in thebaseline and detection monitoring data.

3.2 Initiation of Assessment Monitoring

The lack of a successful ASD for the Appendix III SSIs at the Ash Monofill required that assessmentmonitoring be initiated at the Ash Monofill per 40 CFR 257.94(e)(2) which states if an alternate sourcedemonstration is not successful, the owner or operator must initiate an assessment monitoring programas required under 40 CFR 257.95. The initial assessment monitoring event must be completed within 90days of triggering assessment monitoring which is assumed to be the date of publication of the ASD,April 30, 2018. The initial assessment monitoring event was completed before the 90 day deadline onJune 21, 2018. A second assessment monitoring event was completed on October 16, 2018.

PRPA prepared a written notification that an assessment monitoring program was established at the AshMonofill per 40 CFR 257.94(e)(3). The notification was placed within the facility’s operating record within30 days of establishing the assessment monitoring program [40 CFR 257.105(h)(5)]. This notificationwas placed on the publicly accessible website per 40 CFR 257.107(h)(4). The Colorado Department ofHealth and Environment (CDPHE) and the Larimer County Health Department were also notified that anassessment monitoring program was initiated per 40 CFR 257.106(h)(4).



4.0 Groundwater Monitoring Activities in 2018

This section summarizes groundwater monitoring activities conducted during 2018 to comply with theCCR Rule. Groundwater monitoring activities included:

· Completion of an ASD for Appendix III constituents on April 30, 2018;

· Initiation of an assessment monitoring program per 40 CFR 257.94(e)(2) that includedgroundwater sampling and analysis for Appendix IV constituents in June and October 2018;

· Groundwater sampling and analysis of Appendix III constituents was also conducted in 2018 toprovide additional data to identify potential releases from the Ash Monofill and to update thebackground statistics.

· Statistical analysis of the Appendix IV assessment monitoring results collected during 2018 wasconducted to determine if there were any statistically significant increases (SSIs) overbackground and whether any of the SSIs were above groundwater protection standards(GWPS) at a statistically significant level (SSL); and

· Modification of the monitoring well network through the installation of two additional groundwatermonitoring wells, ASH-06 and ASH-07, in December 2018. The modified monitoring wellnetwork was certified by a professional engineer in accordance with 40 CFR 257.91(c). A copyof the certification is provided in Appendix F.

4.1 Modified Groundwater Monitoring Well System Installation

Two new groundwater monitoring wells were installed at the Ash Monofill in December 2018. Monitoringwell ASH-06 was installed upgradient of the Ash Monofill to provide additional background data whilemonitoring well ASH-07 was installed downgradient of the Ash Monofill to further characterize the extentof SSIs. The modified groundwater monitoring well network for the Ash Monofill is shown on Figure 1.The Ash Monofill network includes two upgradient wells, ASH-01 and ASH-06, that are used to establishbackground groundwater constituent concentrations, and four downgradient wells, ASH-03, ASH-04,ASH-05, and ASH-07, along the southern edge of the Ash Monofill that are designated compliance wells.Monitoring well ASH-01 was installed in 1980 as MW-01 for a site-wide monitoring well network.Monitoring wells ASH-03, ASH-04, and ASH-05 were installed in 2016 to comply with the CCR Rule.Per 40 CFR 257.95(g)(1), monitoring well ASH-07 was installed to characterize the extent of Appendix IVSSIs downgradient of the Ash Monofill. This network satisfies the requirements of 40 CFR 257.91because the Ash Monofill is constructed within a narrow valley that is sloped to the south that localizesgroundwater that may have been affected by a release from the landfill. The downgradient monitoringwells extend across the width of the valley mouth and allow detection of potentially impactedgroundwater from beneath the Ash Monofill.

The two new monitoring wells, ASH-06 and ASH-07, were installed in December 2018. The wellswere installed at locations cleared by PRPA and One Call. Badger Daylighting services performedhydrovac services to clear V-trenches at each boring location to a depth of 7 to 8 ft bgs to reduce thepossibility of the drill rig encountering subsurface utilities. The soil borings were drilled by DrillingEngineers, Inc. of Fort Collins, Colorado using a hollow-stem auger rig equipped with 8.25-inchaugers. Continuous soil cores were collected for logging and visual evaluation of lithology andwater-bearing zones by AECOM’s field geologist. Boring logs were completed in the field as theborings were advanced. The borings were logged by visual observation to lithologically classify thesoils and note the presence or absence of moist soil core, free water in fractures, or groundwaterseepage into the borings.



A permanent monitoring well was installed in each of the new soil borings. The wells wereconstructed with 2-inch internal diameter (i.d.), Schedule 40 polyvinyl chloride (PVC) well casing, and10 slot (0.010-inch machine slotted) well screen. The monitoring wells were screened across thewater-bearing interval observed in the soil core. Monitoring well ASH-06 was equipped with a 15-ftlong screen and monitoring well ASH-07 was equipped with a 10-ft long screen. Filter pack,consisting of 20-40 silica sand, was placed in the well annulus from the bottom to a minimum of 2 ftabove the well screen. A minimum 2-foot thick 3/8-inch hydrated bentonite chip seal was placed ontop of the sand filter pack using coated time-release bentonite chips. A Portland cement-bentonite(neat cement) grout was mixed and placed in the well annulus from the top of the hydrated bentoniteseal to near ground surface. The wells were completed with above ground steel protective casings (2to 3 ft high) with locking expansion plugs. The steel protective casings were set within a 2-ft by 2-ftby 4-6 inch thick concrete pad and surrounded by three steel bollards. Monitoring well completiondetails are shown on Table 1. The boring logs and well construction diagrams for the monitoringwells are included in Appendix A.

4.2 Monitoring Well Development

Following monitoring well installation, the monitoring wells were developed to improve yield and reduceturbidity. Wells were developed by Drilling Engineers using a surge block, bailer, and submersible electricpump. Well development began no sooner than 24-hours after the well was completed and consisted ofremoving approximately 5 to 10 well casing volumes from the well. During well development, AECOMpersonnel sampled the development water for pH, temperature, specific conductance, turbidity, and otherobservations (i.e., color and clarity) after each well casing volume was removed. Each well wasdeveloped to obtain water that was relatively clear (i.e., turbidity is less than 50 nephelometric turbidityunits [NTUs]) and/or all field parameters stabilized (i.e., less than a 10 percent change betweenmeasurements). A well was considered developed when the field parameters stabilized, when 10 wellcasing volumes were removed, or when the well was pumped dry. Well development activities weredocumented on well development forms and are presented in Appendix B.

4.3 Surveying

The horizontal (x and y) and vertical (z) coordinates of the new monitoring wells were measured byNorthern Engineering, a Colorado-licensed surveyor, of Fort Collins, Colorado. Surveymeasurements were referenced to Universal Transverse Mercator (UTM) Zone 13 North, NorthAmerican Datum 1983 (NAD83), and North American Vertical Datum 1988 (NAVD88). Formonitoring wells, the top of the well casing and the ground surface elevation were surveyed. Thehorizontal position was reported in northing and easting coordinates to the nearest 0.10 ft relative tothe survey control points, and vertical position was reported as elevation to the nearest 0.01 ft.

4.4 Well Hydraulic Testing

No well hydraulic tests were conducted in 2018 as the wells were installed in December. Slug tests willbe performed at monitoring wells ASH-06 and ASH-07 in 2019.

4.5 Water Level Measurements

During each monitoring event, groundwater levels were measured using an electronic water level meter.AECOM also measured the total depth of each monitoring well during Round 1 by lowering the metersensor to the bottom of the well. Groundwater levels and total depth measurements were recorded to thenearest hundredth (0.01) of a foot. The water level meter cable and sensor were decontaminated at thestart of field activities and after use at each well to limit the potential for cross-contamination betweenwells. Water level measurements were recorded on groundwater sampling forms, provided in AppendixC, and are tabulated in Table 2 for both assessment monitoring sampling rounds.



4.6 Groundwater Sample Collection

Two rounds of groundwater assessment monitoring samples were collected from the Ash Monofill wellson June 21 and October 10 to 16, 2018. Groundwater samples were collected in general accordancewith the Ash Monofill Sampling and Analysis Plan (AECOM 2017). Each well was initially purged using asubmersible bladder pump and dedicated polyethylene bonded tubing. Disposable bladder liners werereplaced before sampling each monitoring well and the pump casing was decontaminated prior topurging and sampling each monitoring well to avoid cross contamination between wells. The bladderpump tubing was lowered into the well to a depth within the screen interval that was at least 1 to 2 ft offthe bottom of the well to avoid disturbing accumulated sediment in the lower part of the well screen.Monitoring wells were purged using low flow sampling techniques until field parameter measurements ofpH, temperature, dissolved oxygen (DO), oxidation reduction potential (ORP), turbidity, and conductivitystabilized within ±10 percent. Purge water volumes were recorded on groundwater sampling forms(Appendix C).

Groundwater samples were collected after purging each monitoring well. The samples were collectedfrom the tubing outlet of the bladder pump directly into laboratory-supplied sample containers. Samplewater was slowly pumped into each laboratory sample container until the containers were appropriatelyfilled, taking care not to spill the laboratory preservative contained in sample bottles. The groundwatersamples were not field-filtered.. The sample containers were then labeled and placed on ice in a samplecooler. At the conclusion of the field day, the samples were either shipped or delivered by overnightcarrier to Pace Analytical in Lenexa, Kansas for analysis.

4.7 Analytical Program

Groundwater samples collected from the Ash Monofill wells were analyzed using U.S. EnvironmentalProtection Agency SW-846 methods for Appendix III and Appendix IV constituents. All analytical resultsare reported as totals. Tables 3 and 4 summarize the groundwater analytical results for each samplinground. The laboratory analytical reports are provided in Appendix D.

Appendix III constituents included: boron (Method 6010C), chloride (Method 9056A), calcium (Method6010C), fluoride (Method 9056A), pH (field), sulfate (Method 9056A), and total dissolved solids (TDS)(APHA et al. [1998] Standard Method 2540C).

Appendix IV constituents included: antimony (Method 6020A), arsenic (Method 6020A), barium (Method6020A), beryllium (Method 6020A), cadmium (Method 6020A), chromium (Method 6020A), cobalt(Method 6020A), fluoride (Method 9056A), lead (Method 6020A), lithium (Method 6010C), mercury(Method 7470A), molybdenum (Method 6020A), radium 226/228 combined (Method 9315), selenium(Method 6020A), and thallium (Method 6020A).

4.8 Quality Control/Quality Assurance

Quality assurance and quality control (QA/QC) samples collected during sampling activities included onefield duplicate for each round of assessment monitoring, one equipment rinse blank, and one matrixspike/matrix spike duplicate sample (MS/MSD). The field duplicate samples were collected immediatelyfollowing collection of the primary samples using the same sampling procedures. The equipment rinseblank samples were collected after decontaminating the bladder pump casing using techniques outlinedin the sampling and analysis plan.

4.9 Data Validation

The laboratory data were validated by AECOM chemists using U.S. Environmental Protection Agencyguidance. Data validation reports are provided in Appendix D.



5.0 Monitoring Results and Evaluation

This section discusses potentiometric surface elevations, groundwater flow directions, and analyticalsampling results for the samples collected during the two assessment monitoring events in 2018 at theAsh Monofill.

5.1 Groundwater Potentiometric Surface

As required by 40 CFR 257.93(c), the static depth to groundwater was measured at each well duringeach sampling round prior to purging. The depth to groundwater measurements (Table 2) were usedwith the top of casing elevations to calculate the groundwater elevations and prepare potentiometricsurface maps for each sampling round (Figures 2 and 3). These maps were used to determine thatgroundwater in the uppermost aquifer beneath the Ash Monofill flows from northwest to southeast at anaverage hydraulic gradient of 0.016 feet/foot.

5.2 Groundwater Flow

An average flow rate was calculated for groundwater in the uppermost aquifer beneath the Ash Monofillusing the average hydraulic gradient (0.016 ft/ft) determined between monitoring wells ASH-01 andASH-05, the minimum and maximum hydraulic conductivities determined from the slug tests, and anassumed effective porosity of 15 percent. The results indicate that groundwater in the uppermost aquiferbeneath the Ash Monofill flows at a rate ranging from approximately 0.051 to 0.131 ft per day, with ageometric mean of 0.073 ft/d.

5.3 Groundwater Analytical Results

Groundwater samples were collected and analyzed for Appendix III and IV parameters specified inSection 4.7 in June and October 2018. Pace Analytical provided laboratory analytical reports for eachmonitoring event. These laboratory analytical reports are provided in Appendix D and included in thefacility operating record. The laboratory results were reviewed for completeness against the project-required analytical methods and the chain-of-custody forms and subsequently validated by AECOM.The data were found to be valid and useable without qualification. Tables 3 and 4 summarize thegroundwater analytical results for each sampling round.

5.4 Groundwater Monitoring System Evaluation

As described in Section 4, drilling equipment and procedures were employed to identify the uppermostaquifer and determine that each new monitoring well was installed with appropriate total depth andplacement of well screen to: (1) facilitate collection of representative samples of groundwater in theuppermost aquifer, and (2) to accurately measure water-table elevations to determine the groundwaterhydraulic gradient and flow direction. All monitoring wells comprising the Ash Monofill groundwatermonitoring system were inspected during each sampling round and were found to be in good conditionand capable of supplying a representative sample.

Analysis of potentiometric surface maps constructed using the depth to groundwater measurementsobtained during each sampling round (Figures 2 and 3) indicate that groundwater beneath the AshMonofill generally flows from northwest to southeast at average gradient of 0.016 ft/ft and a mean flowrate of approximately 0.073 ft/d. This flow direction is consistent with the groundwater flow directionsobserved during 2016 and 2017. These data confirm that monitoring well ASH-01 is located upgradientof the Ash Monofill and represents background ground water quality and that monitoring wells ASH-03,ASH-04, and ASH-05 are located downgradient of the Ash Monofill and represent downgradientgroundwater quality.



5.5 Problems Encountered and Actions Taken

There were no problems encountered nor actions taken during 2018.



6.0 Statistical Analysis Results

The Appendix IV groundwater quality data were evaluated using the certified statistical approachpresented in the Coal Combustion Residuals (CCR) Ash Monofill Groundwater Detection MonitoringPlan (AECOM 2017). Groundwater quality data were evaluated using an interwell approach thatstatistically compared constituent concentrations at downgradient monitoring wells to those present at abackground monitoring well. For the PRPA Ash Landfill, monitoring well ASH-01 is designated as thebackground well because it is located upgradient of the northern landfill boundary, whereas monitoringwells ASH-03, ASH-04, and ASH-05 are designated as compliance wells because they are located atthe southern monofill boundary.

The statistical analyses were performed in accordance with 40 CFR Parts 257.93(f), 257.93(g), and257.93(h) and the Statistical Method Certification (AECOM 2017). Prediction limits (i.e., parametric ornonparametric) with 1 of 2 retesting were developed for each constituent based on the frequency of non-detect values and whether the background data for that constituent exhibited a normal, lognormal, ornonparametric distribution. For the statistical analysis, non-detect values were represented as one-halfthe detection limit. No outliers were identified in the background data. Analytical data from thebackground monitoring wells collected between March 2016 and October 2018 were used to develop anupper prediction limit (UPL) for the Appendix IV background data at 95 percent confidence. Data fromthe downgradient monitoring wells for the same time period were compared to the UPL to identifystatistically significant increases (SSIs) over background. Mann-Kendall trend analysis was used toidentify statistically significant increasing trends for constituents with SSIs. ProUCL Version 5.1 wasused to store the data and run the statistical analyses. The results of the analyses, including the UPLs,are provided in Table 5. The statistical analysis output is provided in Appendix E.

6.1 Appendix III SSI Determination

The Appendix III detection monitoring results were compared against their respective background UPLsto determine if they exhibited SSIs above background. This comparison indicates that boron, calcium,chloride, sulfate, and total dissolved solids (TDS) at monitoring wells ASH-03, ASH-04, and ASH-05have confirmed SSIs above background UPLs. Fluoride and pH did not show any SSIs abovebackground. The Appendix III SSIs found during 2018 are consistent with those identified during the2016-2017 monitoring period.

6.2 Appendix IV SSI Determination

The Appendix IV assessment monitoring results were compared against their respective backgroundUPLs to determine if they exhibited SSIs above background. This comparison indicates that barium (Ba)at monitoring wells ASH-03 and ASH-05, and selenium (Se) at monitoring wells ASH-03, ASH-04, andASH-05 have SSIs over background that were confirmed by the second assessment monitoring event(Table 5). None of the SSIs had statistically significant increasing trends. No other Appendix IVconstituents exhibited SSIs.

6.3 Establishment of Groundwater Protection Standards

Although no timeframe was specified in the CCR Rule to establish groundwater protection standards(GWPS), other than after an Appendix IV constituent is detected in groundwater for the first time andprior to the next Annual Report [40 CFR 257.95(d)(3)], GWPS were selected for the Ash Monofill usingthe criteria specified in 40 CFR 257.95(h). The GWPS listed on Table 5 were selected from the U.S.Environmental Protection Agency drinking water maximum contaminant limits (MCLs), groundwaterstandards provided in 40 CFR 257.95(3)(h)(2), or the background UPLs where they exceed either of theprevious standards.



6.4 Appendix IV SSL Determination

Constituents exhibiting an SSI over the background UPL, Ba and Se, were further evaluated todetermine whether they are present at statistically significant levels (SSLs) relative to groundwaterprotection standards (GWPS) established under the CCR Rule [40 CFR 257.95(d)(2)]. SSLs wereidentified by calculating the 95 percent lower confidence limit (95 LCL) for the detection and assessmentmonitoring data at the downgradient compliance wells at the Ash Monofill and comparing the 95 LCL tothe GWPS. A constituent is present at an SSL over the GWPS if the 95 LCL is greater than the GWPS.Se at monitoring well ASH-05 was found to exhibit an SSL above its GWPS because its 95 LCL [0.067milligrams per liter (mg/L)] was greater than the GWPS of 0.05 mg/L. Se and Ba were not present at aSSL above the GWPS at any of the other wells because their 95LCLs were less than their respectiveGWPS.



7.0 Projected Activities in 2019

The following activities are anticipated to be performed at the Ash Monofill during calendar year 2019:

· Because several SSIs were found in the Appendix IV constituents during assessmentmonitoring, PRPA has elected to perform an ASD for Ba and Se that show a SSI overbackground to demonstrate that a source other than the Ash Monofill caused the contamination,or that the SSI resulted from error in sampling, analysis, statistical evaluation, or natural variationin groundwater quality. Marine shales like the Pierre Shale are known to have elevated Ba andSe and may be the source of the SSIs. The ASD must be completed within 90 days ofidentifying the SSIs which occurred on December 18, 2018. Thus, the ASD must be completedby March 18, 2019.

· If the ASD is not successful, PRPA must initiate and complete within 90 days an assessment ofcorrective measures as required by 40 CFR 257.96(a) to prevent further releases, to remediateany releases, and to restore the affected area to original conditions. The assessment ofcorrective measures must be performed for Se which occurs at a SSL above the GWPSestablished under 40 CFR 257.95(h). If the ASD is successful, an assessment of correctivemeasures is not required and the site resumes assessment monitoring.

· PRPA must also characterize the nature and extent of the Se release and any site conditionsthat might affect the remedy ultimately selected as specified in 40 CFR 257.95(g)(1).Characterization includes installing additional monitoring wells as necessary to define thecontaminant plume [40 CFR 257.95(g)(1)(i)] and installing at least one additional well at thefacility boundary in the direction of contaminant migration [40 CFR 257.95(g)(1)(iii)];

· PRPA will continue groundwater monitoring on a semiannual basis for the Appendix IIIconstituents and for the Appendix IV constituents that were detected as specified in 40 CFR257.95(d)(1) or 40 CFR 257.95(f). The full list of Appendix IV constituents must be sampledannually.

· Wells ASH-06 and ASH-07 will be added to the monitoring program. Baseline data will becollected for Appendix III and IV constituents on a quarterly basis until eight samples have beencollected at each well. The wells will then be incorporated into the routine detection andassessment monitoring programs. Sampling and analysis will be performed in accordance withthe Ash Monofill Groundwater Monitoring Plan (AECOM 2017). Laboratory analyses will beperformed by Pace Analytical. The new data will be incorporated into the statistical analyses asappropriate.

· Well hydraulic tests (slug or pump tests) will be performed at monitoring wells ASH-06 and ASH-07 in 2019 to determine the hydraulic conductivities of the Pierre Shale. These results will becombined with previous results and used to calculate groundwater flow velocities at the AshMonofill.



8.0 Summary and Findings

AECOM, on behalf of PRPA, oversaw the preparation of an Appendix III ASD, groundwater samplingand analysis of Appendix IV assessment monitoring constituents, establishment of GWPS, statisticaldetermination of Appendix IV SSIs and SSLs above the GWPS, and installation of two new monitoringwells at the Ash Monofill.

An ASD was completed on April 30, 2018 and found no evidence that the Appendix III SSIs were fromerrors in sampling, laboratory analysis, or statistical evaluation, natural variation in groundwaterquality, or an anthropogenic (agricultural or industrial) source. The results of the ASD suggests that thecoal ash disposed in the Ash Monofill is a contributor to the source of the elevated concentrations ofAppendix III constituents that result in the SSIs observed in the baseline and detection monitoringdata.

The lack of a successful ASD required that assessment monitoring be initiated at the Ash Monofill.Two rounds of Appendix IV assessment monitoring data were collected in the uppermost aquiferbeneath the Ash Monofill in June and October 2018. Statistical analyses of the assessment monitoringdata identified Appendix IV SSIs over background UPLs for Ba at monitoring wells ASH-03 and ASH-05, and Se at monitoring wells ASH-03, ASH-04, and ASH-05. No other Appendix IV constituentsexhibited SSIs.

GWPS were selected for the Ash Monofill using the criteria specified in 40 CFR 257.95(h). The GWPSwere selected from the U.S. Environmental Protection Agency drinking water MCLs, groundwaterstandards provided in 40 CFR 257.95(3)(h)(2), or the background UPLs where they exceed either of theprevious standards.

Ba and Se were further evaluated to determine whether they are present at SSLs relative to GWPS. Seat monitoring well ASH-05 was found to exhibit an SSL above its GWPS because its 95 LCL (0.067mg/L) was greater than the GWPS of 0.05 mg/L. Se and Ba were not present at an SSL above theGWPS at any of the other wells.

The existing Ash Monofill monitoring well network was modified by the installation of two new monitoringwells in December 2018. Monitoring well ASH-06 was installed upgradient of the Ash Monofill to assessthe variability of background. Monitoring well ASH-07 was installed downgradient of the Ash Monofill tocharacterize SSI constituent extent.



9.0 References

AECOM. 2017. Coal Combustion Residuals (CCR) Ash Monofill Groundwater Detection MonitoringPlan Revision 0. Prepared for Platte River Power Authority Rawhide Energy Station LaramieCounty, Colorado. October 10, 2017.

American Public Health Association (APHA), American Water Works Association (AWWA), and WaterEnvironment Federation. 1998. Standard Methods for the Examination of Water andWastewater, 20th Edition.

Lidstone & Anderson, Inc. 1989. Investigation of the Ground-Water Monitoring Program for the BottomAsh Disposal Site. March 1989.

Platte River Power Authority (PRPA). 1980. Engineering Report and Operational Plan for the SolidWaste Disposal Facility, Rawhide Energy Project, December 1980.

Title 40 of the Code of Federal Regulations (CFR) Part 257 Subpart D.

AECOM Environment


Tables

Well Name Location Relativeto Waste Unit

Easting(ft)

Northing(ft)

GroundSurface

Elevation(ft amsl)

Top ofCasing

Elevation(ft amsl)

TotalDepth

(ft bgs)

WellScreenInterval(ft bgs)

Well ScreenLithology

ASH-01 Upgradient Well 3124781.307 1562659.296 5759.29 5760.15 31 26-29 Shale

ASH-03 Downgradient Well 3126904.393 1558820.854 5714.21 5717.18 49 39-49 Shale



ASH-06 Upgradient Well 3126039.957 1562657.603 5783.23 5786.41 65 50-65 Shale


Notes:

ASH-01 was installed in December 1980 as MW-1 by Black & Veatch.ASH-03 is also referred to as PRS-7.Wells surveyed in North American Datum 1983 (NAD83)

ft amsl = feet above mean sea level; ft bgs = feet below ground surface

Table 1

Monitoring Well Construction DetailsPRPA Rawhide Facility

Ash Monofill

Page 1 of 1

Table 2 Ash Monofill Water Level Measurements 2018

Well ID SamplingEvent

MeasurementDate

Measuring PointElevation(ft amsl)

Depth toWater

(ft)

GroundwaterElevation(ft amsl)

Round 1 6/21/2018 5760.15 14.33 5745.82

Round 2 10/10/2018 5760.15 14.17 5745.98

Round 1 6/21/2018 5717.18 40.38 5676.80

Round 2 10/16/2018 5717.18 40.45 5676.73

Round 1 6/21/2018 5692.57 16.24 5676.33

Round 2 10/12/2018 5692.57 16.19 5676.38

Round 1 6/21/2018 5698.71 22.83 5675.88

Round 2 10/12/2018 5698.71 23.19 5675.52

Notes:ft = feetft amsl = feet above mean sea level

ASH-01

ASH-03

ASH-04

ASH-05

Page 1 of 1

Table 3 Ash Monofill Analytical Results June 2018

ASH-01 ASH-03 ASH-04 ASH-056/21/2018 6/21/2018 6/21/2018 6/21/2018

Appendix III Constituents Analytical Method UnitBoron SW 846/6010C mg/L 0.52 0.858 0.721 0.831Calcium SW 846/6010C mg/L 339 412 409 468Chloride SW 846/9056A mg/L 19 58.4 200 188Fluoride SW 846/9056A mg/L 0.33 < 0.2 < 0.2 0.26pH Field Measure SU 7.14 7.01 7.33 7.05Sulfate SW 846/9056A mg/L 2520 3850 3460 2890Total Dissolved Solids SM2540C mg/L 3350 5410 5510 4220Appendix IV Constituents Analytical Method UnitAntimony SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Arsenic SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Barium SW 846/6020A mg/L 0.0096 0.0125 0.0104 0.0133Beryllium SW 846/6020A mg/L < 0.0005 < 0.0005 < 0.0015 < 0.0015Cadmium SW 846/6020A mg/L < 0.0015 < 0.0015 < 0.0015 < 0.0015Chromium SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Cobalt SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Lead SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Lithium SW 846/6010C mg/L 0.433 0.41 0.392 0.322Mercury SW 846/7470A mg/L < 0.0002 < 0.0002 < 0.0002 < 0.0002Molybdenum SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Radium 226/228 Combined SW846/9315-9320 pCi/L 0.797 2.51 1.03 1.73Selenium SW 846/6020A mg/L < 0.003 0.0747 0.0426 0.0924Thallium SW 846/6020A mg/L < 0.003 < 0.003 < 0.003 < 0.003Field Parameters Analytical Method UnitDissolved Oxygen Field Measure mg/L 2.33 0.36 0.19 0.00Oxidation Reduction Potential Field Measure mv 113.5 100.6 91.1 113.5Specific Conductivity Field Measure uS/cm 3763 5546 5766 4852Temperature Field Measure degC 12.42 12.8 13.64 13.45Turbidity Field Measure NTU 5.4 100 11.5 28.7Notes:mg/L = milligram per litermv =millivoltsSU = standard unitsuS/cm = microSiemens per centimeterNTU = nephelometric turbidity unitsug/L = microgram per literpCi/L = picocuries per liter< = not detected above indicated reporting limitdegC = degrees Centigrade

Well IDSample Date

Page 1 of 1

Table 4 Ash Monofill Analytical Results October 2018

ASH-01 ASH-03 ASH-04 ASH-0510/10/2018 10/16/2018 10/12/2018 10/12/2018

Appendix III Constituents Analytical Method UnitBoron SW 846/6010C mg/L 0.471 0.781 0.694 0.74Calcium SW 846/6010C mg/L 355 420 414 475Chloride SW 846/9056A mg/L 19.4 66.2 207 221Fluoride SW 846/9056A mg/L 0.23 < 0.2 0.31 0.31pH Field Measure SU 6.76 6.85 7.22 6.94Sulfate SW 846/9056A mg/L 1710 4620 3950 3420Total Dissolved Solids SM2540C mg/L 3190 5420 5130 3960Appendix IV Constituents Analytical Method UnitAntimony SW 846/6020A mg/L < 0.0005 < 0.0005 < 0.0005 < 0.0005Arsenic SW 846/6020A mg/L < 0.0005 0.0028 0.00062 0.0021Barium SW 846/6020A mg/L 0.0119 0.0437 0.0203 0.125Beryllium SW 846/6020A mg/L < 0.0002 < 0.001 < 0.0002 < 0.0002Cadmium SW 846/6020A mg/L <0.00008 <0.00008 <0.00008 <0.00008Chromium SW 846/6020A mg/L < 0.00093 0.0102 < 0.0005 0.0065Cobalt SW 846/6020A mg/L < 0.0005 0.003 0.0012 0.0035Lead SW 846/6020A mg/L 0.0005 0.0057 0.00022 0.003Lithium SW 846/6010C mg/L 0.409 0.392 0.354 0.289Mercury SW 846/7470A mg/L < 0.0002 < 0.0002 < 0.0002 < 0.0002Molybdenum SW 846/6020A mg/L < 0.0005 0.001 0.0014 0.0007Radium 226/228 Combined SW846/9315-9320 pCi/L 1.58 1.45 1.23 1.45Selenium SW 846/6020A mg/L < 0.0005 0.0406 0.0554 0.105Thallium SW 846/6020A mg/L < 0.0001 < 0.0001 < 0.0001 < 0.0001Field Parameters Analytical Method UnitDissolved Oxygen Field Measure mg/L 0.28 0 0 0Oxidation Reduction Potential Field Measure mv 92.5 58 90 37Specific Conductivity Field Measure us/cm 3680 5.6 5.68 4.81Temperature Field Measure degC 11.19 11.92 13.85 14.46Turbidity Field Measure NTU 0 82 105 194Notes:mg/L = milligram per litermv =millivoltsSU = standard unitsuS/cm = microSiemens per centimeterNTU = nephelometric turbidity unitsug/L = microgram per literpCi/L = picocuries per liter< = not detected above indicated reporting limitdegC = degrees Centigrade

Well IDSample Date

Page 1 of 1

of 1

Table 5 Ash Monofill Appendix III Background Upper Prediction Limits (UPLs)

Parameter(Units)

Number ofSamples

PercentNondetects

Normal orLognormal

Distribution?Statistical

TestBackground

Limit

Boron (mg/L) 10 0 Yes/Yes Parametric 0.62

Calcium (mg/L) 10 0 Yes/Yes Parametric 388

Chloride (mg/L) 10 0 Yes/Yes Parametric 29.1

Fluoride (mg/L) 10 20 No/Yes Parametric 1.55

pH (standard units) 10 0 Yes/Yes Parametric 7.45

Sulfate (mg/L) 10 0 No/No Nonparametric 2,740

Total Dissolved Solids(mg/L) 10 0 Yes/Yes Parametric 3,856

Notes:mg/L = milligrams per liter

of 1

Table 6 Ash Monofill Appendix IV Background Upper Prediction Limits (UPLs) and GWPS

Parameter(Units)

Number ofSamples

PercentNondetects

Normal orLognormal

Distribution?Statistical

TestBackground

Limit GWPS

Antimony (mg/L) 10 100 No/No MDL 0.003 0.006

Arsenic (mg/L) 10 100 No/No MDL 0.003 0.05

Barium (mg/L) 10 0 Yes/Yes Parametric 0.012 2.0

Beryllium (mg/L) 10 100 No/No MDL 0.001 0.004

Cadmium (mg/L) 10 100 No/No MDL 0.0015 0.005

Chromium (mg/L) 10 100 No/No MDL 0.003 0.1

Cobalt (mg/L) 10 100 No/No MDL 0.003 0.006

Fluoride (mg/L) 10 20 No/Yes Parametric 1.55 4.0

Lead (mg/L) 10 90 No/No Nonparametric 0.003 0.015

Lithium (mg/L) 10 0 No/No Nonparametric 0.57 0.57

Mercury (mg/L) 10 100 No/No MDL 0.0002 0.002

Molybdenum (mg/L) 10 100 No/No MDL 0.003 0.1

Selenium (mg/L) 10 30 No/No Nonparametric 0.003 0.05

Thallium (mg/L) 10 100 No/No MDL 0.003 0.003

Radium-226+228Combined (pCi//L) 10 20 Yes/Yes Parametric 2.63 5

Notes:mg/L = milligrams per literpCi/L = picoCuries per literMDL = background limit set at maximum detection or reporting limit

All of the antimony, beryllium, cadmium, chromium, cobalt, mercury, molybdenum, and thallium results in thebackground monitoring wells were reported as not detected or detected less than 5 percent. For these constituents, themaximum detection or reporting limit was selected as the UPL per the double quantification rule in the U.S.Environmental Protection Agency’s Unified Statistical Guidance (2009).

Table 7. Ash Monofill Assessment Monitoring Statistical Results for June and October 2018.

Parameter Units BackgroundUPL GWPS ASH-01

Jun 2018ASH-01Oct 2018

ASH-03Jun 2018

ASH-03Oct 2018

ASH-04Jun 2018

ASH-04Oct 2018

ASH-05Jun 2018

ASH-05Oct 2018

Antimony mg/L 0.003 0.006 < 0.003 < 0.0005 < 0.003 < 0.0005 < 0.003 < 0.0005 < 0.003 < 0.0005

Arsenic mg/L 0.003 0.05 < 0.003 < 0.0005 < 0.003 0.0028 < 0.003 0.00062 < 0.003 0.0021

Barium mg/L 0.012 2.0 0.0096 0.0119 0.0125 0.0437 0.0104 0.0203 0.0133 0.125

Beryllium mg/L 0.001 0.004 < 0.0005 < 0.0002 < 0.0005 < 0.001 < 0.0015 < 0.0002 < 0.0015 < 0.0002

Cadmium mg/L 0.0015 0.005 < 0.0015 <0.00008 < 0.0015 <0.00008 < 0.0015 <0.00008 < 0.0015 <0.00008

Chromium mg/L 0.003 0.1 < 0.003 < 0.00093 < 0.003 0.0102 < 0.003 < 0.0005 < 0.003 0.0065

Cobalt mg/L 0.003 0.006 < 0.003 < 0.0005 < 0.003 0.003 < 0.003 0.0012 < 0.003 0.0035

Fluoride mg/L 1.55 4.0 0.33 0.23 < 0.2 < 0.2 < 0.2 0.31 0.26 0.31

Lead mg/L 0.003 0.015 < 0.003 0.0005 < 0.003 0.0057 < 0.003 0.00022 < 0.003 0.003

Lithium mg/L 0.57 0.57 0.433 0.409 0.41 0.392 0.392 0.354 0.322 0.289

Mercury mg/L 0.0002 0.002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002

Molybdenum mg/L 0.003 0.1 < 0.003 < 0.0005 < 0.003 0.001 < 0.003 0.0014 < 0.003 0.0007

Selenium mg/L 0.003 0.05 < 0.003 < 0.0005 0.0747 0.0406 0.0426 0.0554 0.0924 0.105

Thallium mg/L 0.003 0.003 < 0.003 < 0.0001 < 0.003 < 0.0001 < 0.003 < 0.0001 < 0.003 < 0.0001

Ra-226+228 pCi/L 2.63 5 0.797 1.58 2.51 1.45 1.03 1.23 1.73 1.45Notes:Groundwater protection standards (GWPS) are U.S. Environmental Protection Agency primary drinking water standard maximum contaminant limits (MCL) or GWPS provided in 40CFR 257.95(3)(h)(2), except for lithium which is based on the background UPL

Bold black values are detected results; gray shaded cell shows a statistically significant increase (SSI) above background UPL; bold red values exceed the GWPS by directcomparison; yellow shaded cell indicates a statistically significant level (SSL) above the GWPS (i.e., 95 LCL > GWPS)

Ra-226/228 = combined radium 226 and 228; mg/L = milligrams per liter; pCi/L = picoCuries per liter; < = constituent concentration is less than laboratory reporting limit

AECOM Environment


Figures

0 1,000 2,000

Scale in Feet

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RAWHIDE ENERGY STATIONASH MONOFILL MONITORING

WELL NETWORKPlatte River Power Authority Larimer County, COProject No.: 60514655 Date: 01-31-2019

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Ash Monofill Annual Report 2018

PRS Impoundments

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Figure 2

RAWHIDE ENERGY STATIONASH MONOFILL

POTENTIOMETRIC SURFACE MAPPlatte River Power Authority Larimer County, COProject No.: 60514655 Date: 01-31-2019

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PRS Impoundments

JUNE 2018

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Groundwater Elevation Contour (ft msl)



PRS Impoundments

OCTOBER 2018

AECOM Environment


Appendix ABoring Logs andMonitoring WellConstruction Diagrams

Project Name:

Client:

Project Number:

Date(s) Logged J. Hurshman Checked C. Littlefield Total Depth of

Drilled By By Borehole (ft) 67

Drilling Diameter of Ground Surface

Method Borehole (in) Elevation (ft-msl)

Drill Rig Drilling Groundwater

Type Company Elevation (ft-msl)

Driller's Name Measuring Point

Elevation (ft-msl)

Northing

Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

riser

Por

tland

gro

ut

Por

tland

gro

ut

bent

onite

chi

ps

bent

onite

chi

ps

CL

SC

ML

SP

GM

0-4: dark brown silty clay with some gravel, rootlets, stiff, moist, poor recovery, poorly sorted

4-7.5: gravelly silt/clay with sand, poorly sorted, may be fill material from pothole, appears like augers tracked into pothole, granitic gravels

7.5-9: light tan silt, no sand/gravel, little to no clay, no plasticity

9-14: as above, slightly pink in color

14-16.5: as above

16.5-17.5: as above

17.5-19: fine sand grading into medium to coarse sand near 18.5 ft, soft, tan, dry, hard sandstone at 18.8 ft, white in color, homogeneous, hard, well cemented, well sorted

19-20.5: gravels, cobbles, and blocks of sandstone to 20.5, granite gravels, poorly sorted subrounded

6 90 N/AN/A

4 100 N/AN/A

5 100 N/AN/A

N/AN/A

3 100 N/AN/A

1 25 N/A

2 50

SAMPLES

SamplerType

5' core barrel

N/A

Description of Sample Location

(ft bgs) 59.2

HSA 8.25" see well contruction details

PID

(p

pm

)

US

CS

Sym

bo

lMATERIAL DESCRIPTION Well Construction

CME Drilling Engineers

Boring Log

Rawhide - Well Installation

ASH-06Platte River Power Authority Boring ID:60590010

Rob G

12/11/18-12/12/18Depth to Water

Dep

th

(ft-

bg

s)

Sa

mp

le ID

1562657.603

3126039.957

1 of 4

Project Name:

Client:

Project Number:








Elevation (ft-msl)Northing

Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

riser

hydr

ated

ben

toni

te c

hips

hydr

ated

ben

toni

te c

hips

Por

tland

gro

ut

Por

tland

gro

ut

32-33: fine sand, dry, soft, homogeneous, well sorted, tan to brown color

33-34: silt, tan, little fine sand, no clay, no plasticity, dry

34-35: gravelly sand, fine to coarse grained, subrounded to subangular, granitic, poorly sorted, dry

35-36.5: silt, little sand, tan color, dry, little to no clay, no plasticity, soft

36.5-39: silty clay to 39 ft, little to no plasticity, increasing clay content with depth, tan/pinkinsh, oxidized zones (1 cm) at 37.5 and 38.7 ft

39-40: as above

GM

ML

SM to ML

SP

ML

ML to CL

20.5-21.5: silt, tan, soft, dry, no sand/gravel

21.5-24: gravelly silt with medium sand, tan to pink in color, dry, poorly sorted, 10-15% gravel, almost no gravel at 24 ft, soft silt, no clay, no plasticity

24-26.5: as above, minor interbedded sand and gravel 24-25 ft, then decreasing to no gravel, light brown at 26.3 ft

29-31.5: as above

31.5-32: as above

26.5-29: tan silt with minor gravels/sand to 27.5, silt, dry, no clay

N/AN/A

14 100 N/A

N/A

13

N/AN/A

12 100

N/A

10 80 N/AN/A

100

N/A

N/A

N/A

6 90 N/A N/A

N/AN/A

9 60

12/11/18-12/12/18

MATERIAL DESCRIPTION

11

8 100

80


SAMPLESP

ID (

pp

m)

N/A

7 100

N/A

Platte River Power Authority

Well Construction


SamplerType

5' core barrelRob G

US

CS

Sym

bo

l

Depth to Water

(ft bgs) 59.2


Boring Log


ASH-06Boring ID:60590010

Dep

th

(ft-

bg

s)

Sa

mp

le ID

1562657.603

3126039.957

2 of 4

Project Name:

Client:

Project Number:









Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

10/2

0 si

lica

sand

10/2

0 si

lica

sand

hydr

ated

ben

toni

te c

hips

hydr

ated

ben

toni

te c

hips

riser

0.01

slo

t sc

reen

59-59.2: wet at 59.2 ft for ~ 1-2 inches59.2-61.5: as above, blocky weathered shale, orange and red oxidation in fractures, fractures vertically and lower angles throughout, moist, brown to gray colored mottled shale

40-41.5: as above, moist, low plasticity, mottled tan to oxidized orange veins

41.5-44: clayey silt, soft, moist, tan to brown with a few mottled light gray veins, no sand

44-45.5: as above

45.5-46.5: sandy gravel, poorly sorted, fine to coarse sand with gravel, granitic, subangular gravel

46.5-49: sandy gravel as above

49-51.5: as above

CL to ML

GM

SP to SM

CL

we

ath

ere

d s

ha

le

N/AN/A22 100

20 100 N/A N/A

19 100 N/A

21 100 N/A N/A

18 55 N/A N/A

16 90 N/A N/A

17 45 N/A

14 100 N/A N/A

15 100 N/A

N/A

N/A

N/A

51.5-53.5: as above

53.5-54: silty fine sand, brown, moist, no clay, small gravel lens (1 cm) at 53.8 ft, appears to be harder clay at 54 in bottom of drill shoe54-56.5: silty clay, moist, appears to be grading into weathered shale, almost blocky, brown, no sand or gravel, minor interbedded oxidation

56.5-59: weathered shale, brown, slightly broken, fractures, breaks/crumbles easily, oxidized along fractures, moist, almost wet in a few fractures, silt interbedded


SAMPLESP

ID (

pp

m)

US

CS

Sym

bo

l


SamplerType

5' core barrelRob G

12/11/18-12/12/18Depth to Water

(ft bgs) 59.2


Boring Log



3126039.957

Dep

th

(ft-

bg

s)

1562657.603S

am

ple

ID MATERIAL DESCRIPTION Well Construction

3 of 4

Project Name:

Client:

Project Number:









Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

61

62

63

64

65

66

67TD = 67 ft

Well Completion: 68 sump: 65-67

screen (0.01 slot): 50-65riser: 0-5010/20 silica sand: 48-67

69 hydrated bentonite chips: 33-48Portland grout: 4-33

70

71

72

73

74

75

76

77

78

79

80

10/2

0 si

lica

sand

sum

p

1562657.603

61.5-64: gray weathered shale, fractured with oxidation platy, moist, wet in thin <1 cm zone at 62.8 ft, silt along bedding, vertical fracture 63.5-64 ft.

64-67: weathered dark shale with few fractures, fractures have faint orange oxidation, moist to wet along fractures, shell fragments

10/2

0 si

lica

sand

Well Construction

Drilling Engineers

5' core barrel

N/AN/A24 100

23 100 N/A N/A

we

ath

ere

d s

ha

le

22 100 N/AN/A

CME

SamplerType

MATERIAL DESCRIPTION


SAMPLESP

ID (

pp

m)

US

CS

S

ymb

ol

Rob G

12/11/18-12/12/18Depth to Water

(ft bgs) 59.2



Dep

th

(ft-

bg

s)

Sa

mp

le ID

Northing and Easting are in NAD1983 State Plane Colorado North from the Northern Engineering survey on 12/20/18. Boring log was updated by CL on 1/17/19.

3126039.957

Boring Log


4 of 4

WELL ID:

PROJECT NO: DATE INSTALLED: INSTALLED BY:

PIPE SCHEDULE:

PIPE JOINTS:

0 SOLVENT USED:

SCREEN TYPE:

SCR. SLOT SIZE: INCH

BOREHOLE DIAMETER IN. FROM TO FT.IN. FROM TO FT.

SURF. CASING DIAMETER IN. FROM TO FT.

IN. FROM TO FT.

DEVELOPMENT METHOD:

TIME DEVELOPING: HOURS

WATER REMOVED: GALLONS

WATER ADDED: GALLONS

CLARITY BEFORE:

COLOR BEFORE:

CLARITY AFTER:

COLOR AFTER:

ODOR (IF PRESENT):

BEFORE DEVELOPING

AFTER DEVELOPING:

NOTES: OTHER

OTHER

PROTECTIVE COVER AND LOCK INSTALLED?

PERMANENT, LEGIBLE WELL LABEL ADDED?

BOTTOM OF FILTER PACK

FILTER PACK MATERIAL

BOTTOM OF SCREENSC

RE

EN

LE

NG

TH

HOLE BOTTOM

BENTONITE PLUG

BACKFILL MATERIAL

WATER LEVEL SUMMARY

T/PVC

T/PVC

T/PVC

T/PVC

SWE MEASUREMENT DATE TIME

CASING AND SCREEN DETAILS

WELL DEVELOPMENT

TYPE OF RISER:

GROUND SURFACE

TOP OF SCREEN

BENTONITE SEAL MATERIAL

WATER CLARITY BEFORE / AFTER DEVELOPMENT

TOP OF CASING

GROUT

GROUT/BACKFILL MATERIAL

GROUT/BACKFILL METHOD

WELL CONSTRUCTION DATA

CHECKED BY:

PROJECT NAME:

BENTONITE SEAL

DEPTH BELOW OR ABOVE GROUND SURFACE (FEET)

CEMENT SURFACE PLUG

ELEVATION(BENCHMARK: USGS)

RIS

ER

PIP

E L

EN

GT

H

YES NO

YES NO

bentonite chips

Platte River Power Authority - Rawhide Station ASH-06

60590010 12/12/18 JH CL

5786.41 3.18sch. 40 PVCthreaded

5783.23 none

4

sch. 40 PVC

0.01

8.25 0 67Portland grout

332 0 67

hydrated chips48 see development form

5733.23 50

10/20 silica sand

5718.23 65

67

NA

none

67

"JH" = Jeremy Hurshman and Drilling Engineers"CL" = Camille LittlefieldElevations are feet above mean sea level from theNorthern Engineering survey on 12/20/18.

✔

✔

Project Name:

Client:

Project Number:








Elevation (ft-msl)

Northing

Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

1558643.688

3127068.621Description of Sample Location

SAMPLES

Dep

th

(ft-

bg

s)

Sa

mp

le ID

N/AN/A

3 100 N/A

N/A

Boring Log



Rob G

12/4/2018Depth to Water

(ft bgs)



SamplerType

5' core barrel

5-9: upper zone of weathered shale, blocky, crumbles, highly fractured with orange oxidiation along fractures, tan to olive gray color with oxidation, white precipitates at 8.5 ft for ~ 0.5 inches

9-11.5: platy shale, weathered, oxidized on fractures, moist, thinly bedded, silt along bedding planes, olive gray color, minor white precipitates near 11 ft

11.5-14: as above, increasing moisture, oxidized fracture/slightly wet zone of 14 ft bgs.

14-16.5: as above, wet in thin zones at 14.4, 14.6, 15 and 16.1 ft. ( 1 cm thick), olive gray, precipitate crystals in wet zones

PID

(p

pm

)

US

CS

Sym

bo

lMATERIAL DESCRIPTION Well Construction

1 100 N/A

2 100

N/A

N/A

5 100 N/AN/A

4 100 N/A

7 100 N/AN/A

we

ath

ere

d s

ha

le

6

16.5-19: as above, wet/moist zone 16.5-17.5, wet at 18, 18.5 (1-2 inches) each precipitates/oxidation where wet, fractures

N/A

19-20: as above, moist

N/A100

0-4: light tan, silty clay with sand, medium sand ~ 10-20%, rounded gravel, poorly sorted, dry, rootlets 0-2 medium to soft

CL

4-5: as above

10/2

0 si

lica

sand

riser

0.01

slo

t sc

reen

hydr

ated

ben

toni

te c

hips

10/2

0 si

lica

sa

nd

hyd

rate

d b

en

ton

ite c

hip

s

Por

tland

gro

ut

Por

tland

gro

ut

bent

onite

chi

ps

bent

onite

chi

ps

1 of 2

Project Name:

Client:

Project Number:









Easting

Ru

n N

um

be

r

Re

co

ve

ry (

%)

21

22

23

24

25

26

27TD = 27 ft

Well Completion: 28 sump: 25-27 ft bgs

0.01 slot screen: 15-25 ft bgs10/20 silica sand: 13-27 ft bgshydrated bentonite chips: 8-13 ft bgs

29 Portland grout: 5-8 ft bgsBentonite chips: 0-5 ft bgs

30

31

32

33

34

35

36

37

38

39

40

Sa

mp

le ID

Northing and Easting are in NAD1983 State Plane Colorado North from the Northern Engineering survey on 12/20/18. Boring log was updated by CL on 1/17/19.

1558643.688

3127068.621


(ft bgs)


SamplerType

5' core barrel

12/4/2018

Boring Log

SAMPLESP

ID (

pp

m)


MATERIAL DESCRIPTION Well Construction


US

CS

Sym

bo

l

Rob G

Dep

th

(ft-

bg

s)

100


N/A

9 100 N/A

7 100 N/A

8

21.5-23: as above to 23 ft

23-24: dark gray shale, little weathering, platy, thinly bedded, moist, light gray silt along bedding planes, thinly bedded

24-27: as above

N/A

we

ath

ere

d s

ha

le

N/A

N/A

sum

p

10/2

0 si

lica

sand

20-21.5: as above, moist, mottled colors (tan to olive gray)

10/2

0 si

lica

sand

Depth to Water

2 of 2

WELL ID:

PROJECT NO: DATE INSTALLED: INSTALLED BY:

PIPE SCHEDULE:

PIPE JOINTS:

0 SOLVENT USED:

SCREEN TYPE:

SCR. SLOT SIZE: INCH

BOREHOLE DIAMETER IN. FROM TO FT.IN. FROM TO FT.

SURF. CASING DIAMETER IN. FROM TO FT.

IN. FROM TO FT.

DEVELOPMENT METHOD:

TIME DEVELOPING: HOURS

WATER REMOVED: GALLONS

WATER ADDED: GALLONS

CLARITY BEFORE:

COLOR BEFORE:

CLARITY AFTER:

COLOR AFTER:

ODOR (IF PRESENT):

BEFORE DEVELOPING

AFTER DEVELOPING:

NOTES: OTHER

OTHER

PROTECTIVE COVER AND LOCK INSTALLED?

PERMANENT, LEGIBLE WELL LABEL ADDED?

BOTTOM OF FILTER PACK

FILTER PACK MATERIAL

BOTTOM OF SCREENSC

RE

EN

LE

NG

TH

HOLE BOTTOM

BENTONITE PLUG

BACKFILL MATERIAL

WATER LEVEL SUMMARY

T/PVC

T/PVC

T/PVC

T/PVC

SWE MEASUREMENT DATE TIME

CASING AND SCREEN DETAILS

WELL DEVELOPMENT

TYPE OF RISER:

GROUND SURFACE

TOP OF SCREEN

BENTONITE SEAL MATERIAL

WATER CLARITY BEFORE / AFTER DEVELOPMENT

TOP OF CASING

GROUT

GROUT/BACKFILL MATERIAL

GROUT/BACKFILL METHOD

WELL CONSTRUCTION DATA

CHECKED BY:

PROJECT NAME:

BENTONITE SEAL

DEPTH BELOW OR ABOVE GROUND SURFACE (FEET)

CEMENT SURFACE PLUG

ELEVATION(BENCHMARK: USGS)

RIS

ER

PIP

E L

EN

GT

H

YES NO

YES NO

bentonite chips

Platte River Power Authority - Rawhide Station ASH-07

60590010 12/4/18 JH CL

5690.56 2.98sch. 40 PVCthreaded

5687.58 none

5

sch. 40 PVC

0.01

8.25 0 27Portland grout

82 0 27

hydrated chips13 see development form

5672.58 15

10/20 silica sand

5662.58 25

27

NA

none

27

"JH" = Jeremy Hurshman and Drilling Engineers"CL" = Camille LittlefieldElevations are feet above mean sea level from theNorthern Engineering survey on 12/20/18.

✔

✔

AECOM Environment


Appendix BWell Development Forms

"JH" = Jeremy Hurshman "CL" = Camille Littlefield

1 1

PRPA Rawhide - Well Install

60590010 JH CL 1/17/19

ASH-06 ✔

✔

✔

1310 12/18/18

0.11

see below

✔

✔

✔

✔0

N/A

66.65

67.30

2-3

Dry

purged ~ 2 cups water

12/18 - Purged ~ 1.8 ft of water from well sump, well may be dry12/19 at 930 - DTW = 69.86, TD = 70.10, water in sump

4.872.243.19

--

12/19/18

12/18/19

"CA" = Chris Ahrendt "CL" = Camille Littlefield

1 1

PRPA Rawhide - Well Install

60590010 CA CL 1/17/19

ASH-07 ✔

✔

✔

1315 12/18/18

2.13

20

✔

✔

✔

✔

0

N/A

17.04'

30.09

0

17.05

1327

1349

1401

0905

0917

37.7 7.26 - 4451 12.09 0 gal, light gray

33.9 7.43 - 4606 12.36 4 gal, light gray

35.1 7.40 - 4335 11.15 9 gal, light gray

purged dry

- 7.34 +1000 - 12.45 14 gal, light brown

- 7.46 error - 11.42 20 gal, light brown

12/18 - Turbidity meter was not working. Water level after well was purged dry on 12/18 at 14:10 was 27.23 ft.12/19 - Depth to water at start of development = 17.05 ft, total depth = 30.10 ft, well was purged dry for the second time after 15 minutesof purging

AECOM Environment


Appendix CGroundwater SamplingForms

APPENDIX C

GROUNDWATER SAMPLING FORMS

June, 2018 Event – Monitoring Wells

ASH-O1

ASH-03

ASH-04

ASH-05

October, 2018 Event – Monitoring Wells

ASH-O1

ASH-03

ASH-04

ASH-05

June, 2018 Event – Monitoring Wells

ASH-O1

ASH-03

ASH-04

ASH-05

October, 2018 Event – Monitoring Wells

ASH-O1

ASH-03

ASH-04

ASH-05

AECOM Environment


Appendix DLaboratory Analytical andData Validation Reports

APPENDIX D

DATA VALIDATION REPORTS AND QUALIFIED DATA SHEETS

June, 2018

Data Package: 60273354

October, 2018

Data Packages: 60583634

60284115

June, 2018


of 3

M:\DCS\Projects\ENV\PRPA\60569963_CCRAshGW18\500_Deliverables\2018 Ash Monofill Annual GW Report\Appendices\Appendix D - Data Validation Reports and Qualified Data Sheets\June 2018\60273354_Rawhide DVR.docx

Platte River Power Authority – Rawhide

DATA REVIEW CHECK


Sampling Event: June 21, 2018 Data Reviewer: Brian Rothmeyer Date Completed: August 31, 2018

Peer Reviewer: Sheri Fling Date Completed: September 4, 2018

This report contains the final results of the data validation conducted for the water samples collected on June 21, 2018. The data review was conducted in accordance with the method and

laboratory criteria, as applicable. The data review was conducted in accordance with method requirements and laboratory limits using guidance from USEPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540-R-2017-001 (January 2017).

General Overall Assessment:

Data are usable without qualification. X Data are usable with qualification (noted below).

Some or all data are unusable for any purpose (detailed below).

Data Review Checklist Review

Parameter Criteria Criteria

Met? Sample-specific

Parameters

For each “No” response, list qualified data and bias direction in

Table 1 or explain no qualification in comments .

Yes No NA

Chain of Custody, Sample Identification, & Sample Receipt

Samples were received intact and the cooler temperature was <6 degree Celsius upon arrival at the laboratory. X

Holding Times The samples were analyzed within the method required holding times. X

Method Blanks (MB) No target analytes reported in the associated MB.

Analyte Concentration

MB 1486165

Radium-228 0.290 ± 0.289 pCi/L ± - P lus or Minus pCi/L – Picocuries Per Liter

X1

Quality Control Samples: Laboratory

Control Sample (LCS)/ Laboratory Control Sample Duplicate (LCSD)

The LCS/LCSD recoveries were within the laboratory determined acceptance limits. X

Matrix Spike / Matrix Spike Duplicate (MS/MSD)

The recoveries and relative percent differences for the matrix

spike and matrix spike duplicate analyses were within the laboratory-determined acceptance ranges.

Results in the native sample greater than four times the concentration of the spike added during digestions/extractions are

not considered to be a representative measure of accuracy. Further action with respect to spike recovery evaluation or qualification of data was not considered necessary.

X

Laboratory Duplicate

The laboratory duplicate samples were within the laboratory determined acceptance limits. The following concentration X

2

of 3


Review Parameter

Criteria Criteria Met?

Sample-specific

Parameters

For each “No” response, list qualified data and bias direction in Table 1 or explain no qualification in comments .

Yes No NA

dependent criteria were used to evaluate laboratory duplicates:

When both the sample and duplicate values are >5x the reporting limit (RL), acceptable sampling and analytical precision is indicated by an RPD between the results of ≤20%.

Where the result for one or both analytes of the method duplicate pair is <5xRL, satisfactory precision is indicated if the absolute difference between the method duplicate results is <1xRL.

The agreement between parent sample results and the lab duplicate sample results were evaluated. The duplicate error ratios (DER) met the criterion of a DER ≤1.

Field Duplicate The field duplicate sample results satisfied the evaluation criteria below:

Parent Sample Field Duplicate

ASH-02 DUP-1

When both the sample and duplicate values are >5xRL

acceptable sampling and analytical precision is indicated by a relative percent difference (RPD) between the results of ≤30%.

Where the result for one or both analytes of the field duplicate pair is <5xRL, satisfactory precision is indicated if

the absolute difference between the field duplicate results is <2xRL.


X

Equipment Blanks No target analytes reported in the associated equipment blank. X

Reporting Limits Met

(Non –Radiochemistry)

No samples performed at dilutions or reported as non-detect at elevated method detection limits/reporting limits . X

3

Detection Limits Mets

(Radiochemistry )

For radiochemical results if the associated uncertainty was greater than the reported result, the 2 sigma (σ) uncertainty multiplied by 1.65 was less than or equal to the specified detection limit.

X

Tracer and/or Carrier Recovery The sample specific recoveries were within the laboratory limits. X

Package Completeness No results were qualified as unusable and the data are 100% complete. X

Comments

Other – During review of the data package it was noted that the radium-226 and radium-228 LCS/LCSD results, LCS/LCSD

recovery limits, MS/MSD sample result concentrations, and MS/MSD recovery limits were not provided. Upon request, the laboratory provided a supplemental quality control assessment that included these parameters. Therefore, no further action was required.

1 – The associated radium-228 results reported at concentrations <5x the concentration of the blank contamination were

of 3


Review Parameter


Sample-specific

Parameters


Yes No NA

qualified as estimated (J bl-H) to reflect the potential high bias indicated by the blank contamination.

2 – The fluoride RPD reported by the laboratory for the laboratory duplicate performed on sample ASH-01 exceed the laboratory duplicate criterion RPD of 15% with an RPD of 47%. However, as the parent sample and laboratory duplicate sample results were <5x the RL, the criterion that the difference between the parent sample and laboratory duplicate results should be <1xRL was met. Therefore, no further action was required and qualification was not considered necessary.

3 – Several analytes were reported as non-detect at elevated reporting limits. These non-detect results will need to be evaluated by the end user of the data with respect to project objectives.

> – Greater Than < –Less Than ≤ – Less Than or Equal To pCi/L – Picocuries Per Liter % – Percent ± –Plus or Minus bl – Laboratory Blank Contamination DER – Duplicate Error Ration H – High Bias J – Estimated LCS – Laboratory Control Sample LCSD – Laboratory Control Sample Duplicate MB – Method Blank MS/MSD – Matrix Spike/Matrix Spike Duplicate NA – Not Applicable RL – Reporting Limit RPD – Relative Percent Difference

October, 2018

Data Packages: 60583634

60284115

of 3

M:\DCS\Projects\ENV\PRPA\60569963_CCRAshGW18\500_Deliverables\2018 Ash Monofill Annual GW Report\Appendices\Appendix D - Data Validation Reports and Qualified Data Sheets\October 2018\60284115_Rawhide DVR.docx


DATA REVIEW CHECK


Sampling Event: October 16th, 2018 Data Reviewer: Brian Rothmeyer Date Completed: November 26, 2018

Peer Reviewer: Sheri Fling Date Completed: December 6, 2018

This report contains the final results of the data validation conducted for the water samples collected October 16

th, 2018. The data review was conducted in accordance with the method and

laboratory criteria, as applicable. The data review was conducted in accordance with method requirements and laboratory limits using guidance from USEPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540-R-2017-001 (January 2017).







Parameters



Yes No NA




Method Blanks (MB) No target analytes reported in the associated MB. X

Quality Control Samples: Laboratory Control Sample (LCS)/ Laboratory Control Sample Duplicate (LCSD)



The recoveries and relative percent differences for the matrix spike and matrix spike duplicate analyses were within the laboratory-determined acceptance ranges.

Results in the native sample greater than four times the

concentration of the spike added during digestions/extractions are not considered to be a representative measure of accuracy.

Further action with respect to spike recovery evaluation or qualification of data was not considered necessary.

Analyte MS/MSD

(%)

Limits

(%)

RPD

(%)

Limits

(%)

ASH-3

Barium 111/129 75-125 11 20

Chloride 121/121 80-120 1 15 % - Percent MS/MSD – Matrix Spike/ Matrix Spike Duplicate

RPD – Relative Percent Difference Bold indicates a value that is outside of acceptance limits.

X

1

of 3


Review Parameter


Sample-specific

Parameters


Yes No NA

Analyte MS/MSD

(%)

Limits

(%)

DER

Limits

ASH-4

Ra-226 79/101 71-136 2.0 <1

Ra-228 92/80 60-127 1.1 <1 % – Percent

< – Less Than DER – Duplicate Error Ration MS/MSD – Matrix Spike/ Matrix Spike Duplicate Bold indicates a value that is outside of acceptance limits.


The laboratory duplicate samples were within the laboratory determined acceptance limits. The following concentration dependent criteria were used to evaluate laboratory duplicates:

When both the sample and duplicate values are >5x the reporting limit (RL), acceptable sampling and analytical precision is indicated by an relative percent difference (RPD) between the results of ≤20%.

Where the result for one or both analytes of the method

duplicate pair is <5xRL, satisfactory precision is indicated if the absolute difference between the method duplicate results is <1xRL.

The agreement between parent sample results and the lab

duplicate sample results were evaluated. The duplicate error ratios (DER) met the criterion of a DER ≤1.

X2

Field Duplicate The field duplicate sample results satisfied the evaluation criteria

below:


ASH-05 DUP-4

When both the sample and duplicate values are >5xRL acceptable sampling and analytical precision is indicated by a RPD between the results of ≤30%.

Where the result for one or both analytes of the field duplicate pair is <5xRL, satisfactory precision is indicated if the absolute difference between the field duplicate results is <2xRL.

The agreement between parent sample results and the lab duplicate sample results were evaluated. The DER met the criterion of a DER ≤1.

X

Equipment Blanks No target analytes reported in the associated equipment blank.


ERB-3

Chromium 0.74 µg/L

TDS 8 mg/L µg/L – Microgram per Liter mg/L – Milligram per Liter

X3




4

of 3


Review Parameter


Sample-specific

Parameters


Yes No NA


(Radiochemistry )


X



Comments

1 – As the potential bias was considered to be high, the associated detected barium and chloride results for sample ASH-3 were qualified as estimated (J+ m).

As the DER was outside the control limits, the Ra-226 and Ra-228 results for sample ASH-3 were qualified as estimated (J ld).

2 – The total dissolved solid (TDS) RPD reported by the laboratory for the laboratory duplicate performed on sample ERB-3 exceed the laboratory duplicate criterion RPD of 10% with an RPD of 37%. However, as the parent sample and laboratory

duplicate sample results were <5x the RL, the criterion that the difference between the parent sample and laboratory duplicate results should be <1xRL was met. Therefore, no further action was required and qualification was not considered necessary.

3 – During review of the equipment blank results, it was noted that the 6010 metals results were reported at concentrations

that are inconsistent with an equipment blank. In addition the 6010 metals results for sample ASH-3 were not inconsistent with historical results. Upon inquiry to the laboratory, it was determined that the sample container identification (ID) lab els during digestion were inadvertently switched for samples ASH-3 and ERB-3. In addition, the laboratory re-analyzed the

samples for confirmation and confirmed the sample IDs were switched. The laboratory revised and reissued the data package and no further action was required.

The associated chromium and TDS results were reported at concentrations >5x the concentration of the blank contamination, qualification was not considered necessary.

> – Greater Than < –Less Than ≤ – Less Than or Equal To σ – Sigma µg/L – Microgram per Liter mg/L – Milligram Per Liter pCi/L – Picocuries Per Liter % – Percent ± –Plus or Minus DER – Duplicate Error Ration ID – Identification J – Estimated ld – Laboratory Duplicate RPD LCS – Laboratory Control Sample LCSD – Laboratory Control Sample Duplicate m – Matrix Spike Recovery MS/MSD – Matrix Spike/Matrix Spike Duplicate NA – Not Applicable RL – Reporting Limit RPD – Relative Percent Difference TDS – Total Dissolved Solids

of 3



DATA REVIEW CHECK


Sampling Event: October 10th-12th, 2018 Data Reviewer: Brian Rothmeyer Date Completed: November 26, 2018

Peer Reviewer: Sheri Fling Date Completed: December 6, 2018

This report contains the final results of the data validation conducted for the water samples collected October 10

th through 12

th, 2018. The data review was conducted in accordance with

the method and laboratory criteria, as applicable. The data review was conducted in accordance with method requirements and laboratory limits using guidance from USEPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540-R-2017-001 (January 2017).







Parameters



Yes No NA




Method Blanks (MB) No target analytes reported in the associated MB.


MB 3101670

Barium 0.67 µg/L

MB 1546499

Ra-226 0.682 ± 0.479 pCi/L ± – P lus or Minus µg/L – Microgram per Liter pCi/L – Picocuries Per Liter MB – Method Blank Ra – Radium

X1

Quality Control Samples: Laboratory Control Sample (LCS)/ Laboratory Control Sample Duplicate (LCSD)



The recoveries and relative percent differences for the matrix spike and matrix spike duplicate analyses were within the laboratory-determined acceptance ranges.

Results in the native sample greater than four times the

concentration of the spike added during digestions/extractions are not considered to be a representative measure of accuracy.

Further action with respect to spike recovery evaluation or qualification of data was not considered necessary.

X

2

of 3


Review Parameter


Sample-specific

Parameters


Yes No NA

Analyte MS/MSD

(%)

Limits

(%)

RPD

(%)

Limits

(%)

ASH-4

Selenium 136/138 75-125 1 20

Chloride 129/128 80-120 0 15 % - Percent MS/MSD – Matrix Spike/ Matrix Spike Duplicate RPD – Relative Percent Difference Bold indicates a value that is outside of acceptance limits.

Analyte MS/MSD

(%)

Limits

(%)

DER

Limits

ASH-4

Ra-226 82/109 71-136 2.2 <1 % – Percent < – Less Than DER – Duplicate Error Ration MS/MSD – Matrix Spike/ Matrix Spike Duplicate Bold indicates a value that is outside of acceptance limits.


The laboratory duplicate samples were within the laboratory determined acceptance limits. The following concentration dependent criteria were used to evaluate laboratory duplicates:

When both the sample and duplicate values are >5x the

reporting limit (RL), acceptable sampling and analytical precision is indicated by a relative percent difference (RPD) between the results of ≤20%.

Where the result for one or both analytes of the method

duplicate pair is <5xRL, satisfactory precision is indicated if the absolute difference between the method duplicate results is <1xRL.


X

Field Duplicate The field duplicate sample results satisfied the evaluation criteria

below:


ASH-05 DUP-4

When both the sample and duplicate values are >5xRL

acceptable sampling and analytical precision is indicated by a RPD between the results of ≤30%.

Where the result for one or both analytes of the field

duplicate pair is <5xRL, satisfactory precision is indicated if the absolute difference between the field duplicate results is <2xRL.

The agreement between parent sample results and the lab

duplicate sample results were evaluated. The DER met the criterion of a DER ≤1.

X

Equipment Blanks No target analytes reported in the associated equipment blank. X3

of 3


Review Parameter


Sample-specific

Parameters


Yes No NA


ERB-3

Chromium 0.74 µg/L

TDS 8 mg/L µg/L – Microgram per Liter mg/L – Milligram per Liter





(Radiochemistry )


X



Comments

1 – The associated barium sample results were reported at concentrations >5x the concentration of the blank contamination, qualification was not considered necessary.

The associated radium-226 sample results reported at concentrations <5x the concentration of the blank contamination were qualified as estimated (J+ bl) to reflect the potential high bias indicated by the blank contamination.

2 – As the potential bias was considered to be high, the associated detected selenium and chloride results for sample ASH-4 were qualified as estimated (J+ m).

As the DER was outside the control limits, the Ra-226 result for sample ASH-4 was qualified as estimated (J ld).

3 – The chromium result for sample MW-1 (ASH-1) was reported at a concentration <5x the concentration of the blank contamination and was qualified as non-detect (U be).

> – Greater Than < –Less Than ≤ – Less Than or Equal To σ – Sigma µg/L – Microgram per Liter mg/L – Milligram per Liter pCi/L – Picocuries Per Liter % – Percent ± –Plus or Minus bl – Laboratory Blank Contamination be – Equipment Blank Contamination DER – Duplicate Error Ration J – Estimated ld – Laboratory Duplicate RPD LCS – Laboratory Control Sample

LCSD – Laboratory Control Sample Duplicate MS/MSD – Matrix Spike/Matrix Spike Duplicate NA – Not Applicable RL – Reporting Limit RPD – Relative Percent Difference U – Non-detect

AECOM Environment


Appendix EStatistical Analysis Results

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

A B C D E F G H I J K L M N

Background Statistics Assuming Gamma Distribution

MLE Mean (bias corrected) 0.512 MLE Sd (bias corrected) 0.0634

Theta hat (MLE) 0.0055 Theta star (bias corrected MLE) 0.00785

nu hat (MLE) 1863 nu star (bias corrected) 1305

Gamma Statistics

k hat (MLE) 93.15 k star (bias corrected MLE) 65.27

5% K-S Critical Value 0.266Detected data appear Gamma Distributed at 5% Significance Level

Detected data appear Gamma Distributed at 5% Significance Level

5% A-D Critical Value 0.724Detected data appear Gamma Distributed at 5% Significance Level

K-S Test Statistic 0.177 Kolmogorov-Smirnov Gamma GOF Test

Gamma GOF Test

A-D Test Statistic 0.385 Anderson-Darling Gamma GOF Test

95% UPL (t) 0.623 95% Percentile (z) 0.607

95% USL 0.637 99% Percentile (z) 0.646

Background Statistics Assuming Normal Distribution

95% UTL with 95% Coverage 0.679 90% Percentile (z) 0.586

5% Lilliefors Critical Value 0.262 Data appear Normal at 5% Significance Level

Data appear Normal at 5% Significance Level

5% Shapiro Wilk Critical Value 0.842 Data appear Normal at 5% Significance Level

Lilliefors Test Statistic 0.183 Lilliefors GOF Test

Normal GOF Test

Shapiro Wilk Test Statistic 0.904 Shapiro Wilk GOF Test

Critical Values for Background Threshold Values (BTVs)

Tolerance Factor K (For UTL) 2.911 d2max (for USL) 2.176

Coefficient of Variation 0.112 Skewness 1.06

Mean of logged Data -0.675 SD of logged Data 0.108

Maximum 0.63 Third Quartile 0.535

Mean 0.512 SD 0.0574

Minimum 0.45 First Quartile 0.47

Second Largest 0.58 Median 0.5

B

General Statistics

Total Number of Observations 10 Number of Distinct Observations 9

Coverage 95%

Different or Future K Observations 1

Number of Bootstrap Operations 2000

From File Ash_Monofill_ProUCL_Input.xls

Full Precision OFF

Confidence Coefficient 95%

Background Statistics for Data Sets with Non-Detects

User Selected Options

Date/Time of Computation ProUCL 5.11/31/2019 1:53:42 PM

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Mean of logged Data 5.861 SD of logged Data 0.055

Mean 351.4 SD 19.22

Coefficient of Variation 0.0547 Skewness -0.141

Second Largest 370 Median 352.5

Maximum 380 Third Quartile 367.5


Minimum 320 First Quartile 339.3

represents a background data set and when many onsite observations need to be compared with the BTV.

Ca

General Statistics

Note: The use of USL tends to yield a conservative estimate of BTV, especially when the sample size starts exceeding 20.

Therefore, one may use USL to estimate a BTV only when the data set represents a background data set free of outliers

and consists of observations collected from clean unimpacted locations.

The use of USL tends to provide a balance between false positives and false negatives provided the data

95% Chebyshev UPL 0.775 99% Percentile 0.626

95% USL 0.63

95% UPL 0.63 90% Percentile 0.585


Approximate Sample Size needed to achieve specified CC 59

95% Percentile Bootstrap UTL with 95% Coverage 0.63 95% BCA Bootstrap UTL with 95% Coverage 0.63

Order of Statistic, r 10 95% UTL with 95% Coverage 0.63

Approx, f used to compute achieved CC 0.526Approximate Actual Confidence Coefficient achieved by UTL 0.401

Nonparametric Distribution Free Background Statistics


Nonparametric Upper Limits for Background Threshold Values


95% USL 0.644 99% Percentile (z) 0.655

Background Statistics assuming Lognormal Distribution


5% Lilliefors Critical Value 0.262 Data appear Lognormal at 5% Significance Level

Data appear Lognormal at 5% Significance Level

5% Shapiro Wilk Critical Value 0.842 Data appear Lognormal at 5% Significance Level

Lilliefors Test Statistic 0.168 Lilliefors Lognormal GOF Test

Lognormal GOF Test

Shapiro Wilk Test Statistic 0.923 Shapiro Wilk Lognormal GOF Test

95% HW Approx. Gamma UTL with 95% Coverage 0.692

95% WH USL 0.642 95% HW USL 0.642

95% Hawkins Wixley (HW) Approx. Gamma UPL 0.626 95% Percentile 0.621

95% WH Approx. Gamma UTL with 95% Coverage 0.691 99% Percentile 0.671

95% Wilson Hilferty (WH) Approx. Gamma UPL 0.625 90% Percentile 0.595

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Order of Statistic, r 10 95% UTL with 95% Coverage 380





95% USL 395.5 99% Percentile (z) 398.8







Lognormal GOF Test



95% WH USL 394.7 95% HW USL 394.9








Gamma Statistics






Gamma GOF Test


95% UPL (t) 388.4 95% Percentile (z) 383

95% USL 393.2 99% Percentile (z) 396.1


95% UTL with 95% Coverage 407.4 90% Percentile (z) 376





Normal GOF Test


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Gamma Statistics






Gamma GOF Test



95% USL 29.89 99% Percentile (z) 30.37







Normal GOF Test





Mean 22.94 SD 3.196


Second Largest 25 Median 23

Maximum 29 Third Quartile 25


Minimum 19 First Quartile 20.25


Cl

General Statistics






95% USL 380

95% UPL 380 90% Percentile 371



95% Percentile Bootstrap UTL with 95% Coverage 380 95% BCA Bootstrap UTL with 95% Coverage 380


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Minimum Detect 0.12 Minimum Non-Detect 0.2

Maximum Detect 1.65 Maximum Non-Detect 0.2

Number of Detects 8 Number of Non-Detects 2

Number of Distinct Detects 8 Number of Distinct Non-Detects 1

Total Number of Observations 10 Number of Missing Observations 0

Number of Distinct Observations 8


F

General Statistics






95% USL 29

95% UPL 29 90% Percentile 25.4

90% Chebyshev UPL 33 95% Percentile 27.2









95% USL 30.68 99% Percentile (z) 31.32







Lognormal GOF Test



95% WH USL 30.38 95% HW USL 30.45






nu hat (MLE) 1168 nu star (bias corrected) 819.2

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Maximum 1.65 Median 0.31

SD 0.475 CV 1.193

This is especially true when the sample size is small.

For gamma distributed detected data, BTVs and UCLs may be computed using gamma distribution on KM estimates

Minimum 0.01 Mean 0.398

Gamma ROS Statistics using Imputed Non-Detects

GROS may not be used when data set has > 50% NDs with many tied observations at multiple DLs

GROS may not be used when kstar of detects is small such as <1.0, especially when the sample size is small (e.g., <15-20)

For such situations, GROS method may yield incorrect values of UCLs and BTVs

MLE Mean (bias corrected) 0.495

MLE Sd (bias corrected) 0.444 95% Percentile of Chisquare (2kstar) 6.912


nu hat (MLE) 29.75 nu star (bias corrected) 19.93

Gamma Statistics on Detected Data Only





K-S Test Statistic 0.237 Kolmogorov-Smirnov GOF

Gamma GOF Tests on Detected Observations Only

A-D Test Statistic 0.499 Anderson-Darling GOF Test

99% Percentile (z) 1.485 95% USL 1.416

DL/2 is not a recommended method. DL/2 provided for comparisons and historical reasons

95% UTL95% Coverage 1.754 95% UPL (t) 1.3

90% Percentile (z) 1.005 95% Percentile (z) 1.172

DL/2 Substitution Background Statistics Assuming Normal Distribution

Mean 0.416 SD 0.46

99% KM Percentile (z) 1.428 95% KM USL 1.363

95% UTL95% Coverage 1.681 95% KM UPL (t) 1.253

90% KM Percentile (z) 0.975 95% KM Percentile (z) 1.133

Kaplan Meier (KM) Background Statistics Assuming Normal Distribution

KM Mean 0.42 KM SD 0.433

5% Lilliefors Critical Value 0.283 Data Not Normal at 5% Significance Level

Data Not Normal at 5% Significance Level

5% Shapiro Wilk Critical Value 0.818 Data Not Normal at 5% Significance Level


Normal GOF Test on Detects Only




Mean of Detected Logged Data -0.996 SD of Detected Logged Data 0.769

Variance Detected 0.236 Percent Non-Detects 20%

Mean Detected 0.495 SD Detected 0.486

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SD in Original Scale 0.46 SD in Log Scale 0.874

Background DL/2 Statistics Assuming Lognormal Distribution

Mean in Original Scale 0.416 Mean in Log Scale -1.257

KM SD of Logged Data 0.785 95% KM UPL (Lognormal) 1.336

95% KM Percentile Lognormal (z) 1.074 95% KM USL (Lognormal) 1.63

Statistics using KM estimates on Logged Data and Assuming Lognormal Distribution

KM Mean of Logged Data -1.22 95% KM UTL (Lognormal)95% Coverage 2.903

99% Percentile (z) 2.204 95% USL 1.931

95% Bootstrap (%) UTL95% Coverage 1.65 95% UPL (t) 1.545



95% UTL95% Coverage 3.686 95% BCA UTL95% Coverage 1.65

Background Lognormal ROS Statistics Assuming Lognormal Distribution Using Imputed Non-Detects


5% Lilliefors Critical Value 0.283 Detected Data appear Lognormal at 5% Significance Level

Detected Data appear Lognormal at 5% Significance Level

5% Shapiro Wilk Critical Value 0.818 Detected Data appear Lognormal at 5% Significance Level


Lognormal GOF Test on Detected Observations Only


1.243

95% KM Gamma Percentile 1.05 1.049 95% Gamma USL 1.411 1.443

95% Approx. Gamma UTL with 95% Coverage 2.035 2.159 95% Approx. Gamma UPL 1.23

The following statistics are computed using gamma distribution and KM estimates

Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods

WH HW WH HW

80% gamma percentile (KM) 0.69 90% gamma percentile (KM) 1.046


nu hat (KM) 18.8 nu star (KM) 14.49

theta hat (KM) 0.447 theta star (KM) 0.58

Variance (KM) 0.188 SE of Mean (KM) 0.146

k hat (KM) 0.94 k star (KM) 0.725

Estimates of Gamma Parameters using KM Estimates

Mean (KM) 0.42 SD (KM) 0.433

1.882

95% Gamma USL 1.985 2.317


The following statistics are computed using Gamma ROS Statistics on Imputed Data


WH HW WH HW

95% Percentile of Chisquare (2kstar) 4.285 90% Percentile 1.038

95% Percentile 1.438 99% Percentile 2.408





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Gamma GOF Test



95% USL 7.509 99% Percentile (z) 7.546







Normal GOF Test




Coefficient of Variation 0.0349 Skewness -0.413



Mean 6.98 SD 0.243



pH

General Statistics







95% USL 1.65 95% KM Chebyshev UPL 2.401


Approximate Sample Size needed to achieve specified CC 59 95% UPL 1.65

Nonparametric Upper Limits for BTVs(no distinction made between detects and nondetects)

Order of Statistic, r 10 95% UTL with95% Coverage 1.65

DL/2 is not a Recommended Method. DL/2 provided for comparisons and historical reasons.


Data appear to follow a Discernible Distribution at 5% Significance Level


99% Percentile (z) 2.174 95% USL 1.907


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SO4

General Statistics






95% USL 7.3

95% UPL 7.3 90% Percentile 7.228










95% USL 7.53 99% Percentile (z) 7.569







Lognormal GOF Test



95% WH USL 7.523 95% HW USL 7.524








Gamma Statistics

k hat (MLE) 907 k star (bias corrected MLE) 634.9



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5% Lilliefors Critical Value 0.262 Data Not Lognormal at 5% Significance Level

Data Not Lognormal at 5% Significance Level

5% Shapiro Wilk Critical Value 0.842 Data Not Lognormal at 5% Significance Level


Lognormal GOF Test


95% HW Approx. Gamma UTL with 95% Coverage 2981

95% WH USL 2751 95% HW USL 2753

95% Hawkins Wixley (HW) Approx. Gamma UPL 2678 95% Percentile 2656

95% WH Approx. Gamma UTL with 95% Coverage 2974 99% Percentile 2885


95% Wilson Hilferty (WH) Approx. Gamma UPL 2677 90% Percentile 2539

MLE Mean (bias corrected) 2166 MLE Sd (bias corrected) 285.6



Gamma Statistics


5% K-S Critical Value 0.266 Data Not Gamma Distributed at 5% Significance Level

Data Not Gamma Distributed at 5% Significance Level

5% A-D Critical Value 0.724 Data Not Gamma Distributed at 5% Significance Level


Gamma GOF Test


95% UPL (t) 2672 95% Percentile (z) 2599

95% USL 2738 99% Percentile (z) 2778


95% UTL with 95% Coverage 2932 90% Percentile (z) 2503





Normal GOF Test





Mean 2166 SD 263





Minimum 1900 First Quartile 2000

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95% USL 3898 99% Percentile (z) 3923







Normal GOF Test





Mean 3538 SD 165.7





Minimum 3330 First Quartile 3425


TDS

General Statistics





95% Chebyshev UPL 3368 99% Percentile 2720

95% USL 2740








Data do not follow a Discernible Distribution (0.05)



95% USL 2760 99% Percentile (z) 2807



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95% USL 3900











95% USL 3908 99% Percentile (z) 3935







Lognormal GOF Test


95% HW Approx. Gamma UTL with 95% Coverage 4037

95% WH USL 3905 95% HW USL 3905

95% Hawkins Wixley (HW) Approx. Gamma UPL 3861 95% Percentile 3849

95% WH Approx. Gamma UTL with 95% Coverage 4035 99% Percentile 3985


95% Wilson Hilferty (WH) Approx. Gamma UPL 3860 90% Percentile 3778

MLE Mean (bias corrected) 3538 MLE Sd (bias corrected) 185.9



Gamma Statistics






Gamma GOF Test


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Coverage 95%

Different or Future K Observations 1

Number of Bootstrap Operations 2000

From File Ash_Monofill_ProUCL_Input_b.xls

Full Precision OFF

Confidence Coefficient 95%

Background Statistics for Data Sets with Non-Detects

User Selected Options

Date/Time of Computation ProUCL 5.11/31/2019 2:43:59 PM


Minimum Detect N/A Minimum Non-Detect 5.0000E-4



As

General Statistics


Warning: All observations are Non-Detects (NDs), therefore all statistics and estimates should also be NDs!

Specifically, sample mean, UCLs, UPLs, and other statistics are also NDs lying below the largest detection limit!

The Project Team may decide to use alternative site specific values to estimate environmental parameters (e.g., EPC, BTV).

Mean Detected N/A SD Detected N/A

Mean of Detected Logged Data N/A SD of Detected Logged Data N/A

Maximum Detect N/A Maximum Non-Detect 0.003

Variance Detected N/A Percent Non-Detects 100%



General Statistics


The data set for variable As was not processed!

Ba






Mean 0.00995 SD 0.00114





Normal GOF Test


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Gamma GOF Test



95% USL 0.0124 99% Percentile (z) 0.0126

Theta hat (MLE) 1.1914E-4 Theta star (bias corrected MLE) 1.7000E-4


Gamma Statistics













Lognormal GOF Test



95% WH USL 0.0126 95% HW USL 0.0126





95% USL 0.0127 99% Percentile (z) 0.013



95% UPL 0.0119 90% Percentile 0.0111







95% USL 0.0119

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Be

General Statistics











Cd

General Statistics




The data set for variable Be was not processed!










Co

General Statistics




The data set for variable Cd was not processed!




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The data set for variable Co was not processed!








Cr

General Statistics








F

General Statistics




The data set for variable Cr was not processed!








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Mean 0.397 SD 0.463








99% Percentile (z) 1.475 95% USL 1.405









SD 0.478 CV 1.26












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A B C D E F G H I J K L M N95% Percentile of Chisquare (2kstar) 4.255 90% Percentile 0.991


1.777

95% Gamma USL 1.893 2.188




WH HW WH HW




k hat (KM) 0.842 k star (KM) 0.656


Mean (KM) 0.401 SD (KM) 0.437



WH HW WH HW







1.19











99% Percentile (z) 2.105 95% USL 1.841











99% Percentile (z) 2.004 95% USL 1.76

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Hg

General Statistics







Maximum Detect N/A Maximum Non-Detect 2.0000E-4




General Statistics


The data set for variable Hg was not processed!

Li






Mean 0.44 SD 0.0594

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Normal GOF Test




Gamma GOF Test



95% USL 0.569 99% Percentile (z) 0.578


nu hat (MLE) 1357 nu star (bias corrected) 951.1

Gamma Statistics













Lognormal GOF Test



95% WH USL 0.571 95% HW USL 0.572





95% USL 0.573 99% Percentile (z) 0.584





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95% UPL 0.57 90% Percentile 0.53





Mo

General Statistics






95% USL 0.57







Pb

General Statistics




The data set for variable Mo was not processed!




Minimum Detect 0.002 Minimum Non-Detect 5.0000E-4






Warning: Only one distinct data value was detected! ProUCL (or any other software) should not be used on such a data set!

It is suggested to use alternative site specific values determined by the Project Team to estimate environmental parameters (e.g., EPC, BTV).

The data set for variable Pb was not processed!

Mean of Detected Logged Data -6.215 SD of Detected Logged Data N/A


Mean Detected 0.002 SD Detected N/A

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Sb

General Statistics











General Statistics


The data set for variable Sb was not processed!

Se

Mean Detected 0.002 SD Detected 5.7735E-4



Variance Detected 3.3333E-7 Percent Non-Detects 30%


Minimum Detect 0.001 Minimum Non-Detect 5.0000E-4










KM Mean 0.00165 KM SD 7.7217E-4




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Mean 0.00163 SD 8.2706E-4







99% Percentile (z) 0.00355 95% USL 0.00342



MLE Sd (bias corrected) 7.4841E-4 95% Percentile of Chisquare (2kstar) 24.06

Theta hat (MLE) 1.6220E-4 Theta star (bias corrected MLE) 2.8006E-4





SD 0.00389 CV 0.885














0.014

95% Gamma USL 0.0156 0.0163




WH HW WH HW


theta hat (KM) 3.6136E-4 theta star (KM) 5.0569E-4

Variance (KM) 5.9625E-7 SE of Mean (KM) 2.7442E-4

k hat (KM) 4.566 k star (KM) 3.263


Mean (KM) 0.00165 SD (KM) 7.7217E-4


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WH HW WH HW






0.00394



SD in Original Scale 6.1114E-4 SD in Log Scale 0.358








99% Percentile (z) 0.00386 95% USL 0.00366



SD in Original Scale 8.2706E-4 SD in Log Scale 0.77












99% Percentile (z) 0.00801 95% USL 0.00714









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Tl

General Statistics











General Statistics


The data set for variable Tl was not processed!

RaC


Mean of Detected Logged Data 0.264 SD of Detected Logged Data 0.443

Maximum Detect 3 Maximum Non-Detect 0.71




5% Shapiro Wilk Critical Value 0.818 Detected Data appear Normal at 5% Significance Level










5% Lilliefors Critical Value 0.283 Detected Data appear Normal at 5% Significance Level

Detected Data appear Normal at 5% Significance Level


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Mean 1.204 SD 0.804







99% Percentile (z) 3.076 95% USL 2.955








Maximum 3 Median 1.03

SD 0.873 CV 0.757














5.043

95% Gamma USL 5.111 6.091




WH HW WH HW




k hat (KM) 2.955 k star (KM) 2.135


Mean (KM) 1.241 SD (KM) 0.722



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WH HW WH HW





2.841




95% UTL95% Coverage 6.006 95% BCA UTL95% Coverage 3


Mean in Original Scale 1.233 Mean in Log Scale 0.0488




KM Mean of Logged Data 0.0646 95% KM UTL (Lognormal)95% Coverage 5.21

99% Percentile (z) 4.231 95% USL 3.867

95% Bootstrap (%) UTL95% Coverage 3 95% UPL (t) 3.322









Order of Statistic, r 10 95% UTL with95% Coverage 3





99% Percentile (z) 5.497 95% USL 4.913






95% USL 3 95% KM Chebyshev UPL 4.54


Approximate Sample Size needed to achieve specified CC 59 95% UPL 3

AECOM Environment


Appendix FModified GroundwaterMonitoring Well NetworkCertification

AECOM Environment


Appendix GAsh MonofillAppendix III AlternateSource Demonstration

Memorandum

To:

Office:

Courtney Stewart, PEChris Wood

Platte River Power AuthorityFt. Collins, Colorado

From:

Office:

Date:

Richard HenryGregg Somermeyer, PEGeoff Webb

Greenwood Village, CO

April 30, 2018

Subject: Ash Monofill Appendix III Constituents Alternate Source Demonstration

Introduction

This memorandum provides the written results of an Alternate Source Demonstration (ASD) forthe Ash Monofill at the Platte River Power Authority Rawhide Energy Station in LarimerCounty, Colorado. The purpose of the ASD is to assess whether a source other than the AshMonofill is responsible for the statistically significant increases (SSIs) over background forAppendix III constituents boron, calcium, chloride, sulfate, and total dissolved solids (TDS) atdowngradient monitoring wells ASH-03, ASH-04, and ASH-05. This ASD is being completedunder the Coal Combustion Residuals (CCR) Rule, 40 Code of Federal Regulations (CFR) Part257, promulgated on April 17, 2015.

Regulatory Background

The Ash Monofill is regulated under the CCR Rule (40 CFR 257) which allows an owner oroperator to demonstrate that a source other than a CCR unit caused the SSI over background forAppendix III constituents, or that the SSI resulted from an error in sampling, analysis, statisticalevaluation, or natural variation in groundwater quality [40 CFR 257.94(e)(2)]. The owner oroperator must complete a written demonstration within 90 days of detecting an SSI overbackground that includes a certification by a qualified professional engineer verifying theaccuracy of the information in the report. If a successful demonstration is completed within the90-day period, the owner or operator of the CCR unit may continue with detection monitoring inaccordance with 40 CFR 257.94. If a successful demonstration is not completed within 90 days,an assessment monitoring program must be initiated as described in 40 CFR 257.95. For the AshMonofill, the initial detection of Appendix III SSIs occurred on January 30, 2018, thus, the ASDmust be completed by April 30, 2018.

Ash Monofill Site Conditions

The Ash Monofill is located northwest of the Rawhide Energy Station main plant and north ofthe Cooling Pond (Figure 1). CCR fly and bottom ash from Unit 1 operations is disposed in the

Memorandum

2

Ash Monofill which is comprised of two cells, Cell 1 and Cell 2 (Figure 1). Cell 1 was operatedfrom approximately 1980 to 2007 and is no longer in use. It is capped with cover soils but hasnot undergone final closure. Cell 2 is active, lies to the west of the closed Cell 1, and currentlyreceives ash material.

The uppermost water-bearing stratum beneath the Ash Monofill was identified as the weatheredand fractured Pierre Shale during prior groundwater monitoring well installation activities.Groundwater beneath the Ash Monofill is under water table conditions and lies at depths rangingfrom approximately 12 to 38 feet below ground surface. The Ash Monofill is constructed withina narrow south-sloping valley with bedrock highs along both sides. Groundwater flow isgenerally from northwest to south-southeast, from the Ash Monofill to the Cooling Pond,generally following the topographic slope of the valley. Although water occurs in the weatheredand fractured Pierre Shale, it is naturally of poor quality and limited quantity.

Eight rounds of baseline detection monitoring data were collected at the Ash Monofill betweenSeptember 2016 and July 2017 for Appendix III and IV constituents to comply with the CCRRule. Based on statistical analysis results, SSIs over background were found for Appendix IIIconstituents boron, calcium, chloride, sulfate, and TDS at downgradient monitoring wells ASH-03, ASH-04, and ASH-05 (AECOM 2018). PRPA elected to perform an ASD to assess whetherthe observed SSIs are from an alternative source other than the Ash Monofill.

Types of Alternative Sources

As specified in 40 CFR 257.94(e)(2), alternative sources for a SSI can include errors insampling, laboratory analysis, statistical evaluation, natural variation in groundwater quality, or asource other than the CCR unit. Errors in sampling can include sample mislabeling, inadvertentcontamination of a sample, change in sampling technique, or excessive suspended solids.Laboratory analysis errors can include choice of analytical and digestion methods, instrumentcalibration, analytical technique, inadvertent laboratory contamination, analyte interferences,dilution errors, and data recording and transcription errors. Errors in statistical evaluation caninclude lack of statistical independence between samples, outliers, trends, and results belowdetection limits. Natural variations in groundwater quality are influenced by site geology,precipitation, seasonality, water level, changes in pH or oxidation-reduction potential (ORP),biological activity, and time of travel. Other sources can include agricultural or industrialactivities. The potential for each of these alternative source types to account for the SSIsidentified at the Ash Monofill is discussed in the sections below.

Memorandum

3

Sampling Errors

AECOM reviewed the field sampling and field instrument calibration records and the chain-of-custody (COC) forms to determine if sampling errors may have occurred. Sampling wasperformed in accordance with the procedures outlined in the CCR Ash Monofill GroundwaterDetection Monitoring Plan Revision 0 (AECOM 2017) so that consistent sampling techniqueswere used for all of the baseline sampling events. Samples were collected using low-flowtechniques to minimize excessive suspended solids. Turbidity measurements were generallylow, indicating that suspended solids were also low.

Sampling started with the upgradient well (ASH-01), followed by the downgradient wells (ASH-03, ASH-04, and ASH-05), to minimize the potential for cross contamination. Nondisposablesampling equipment was decontaminated between wells to further minimize the potential forcross contamination. Equipment rinse blanks were collected to confirm the effectiveness ofdecontamination. No other sampling errors such as sample bottle or COC mislabeling ortranscription errors were noted in the field records. Sampling errors do not appear to haveoccurred that could lead to the SSIs identified for the downgradient Ash Monofill monitoringwells.

Laboratory Analysis Errors

The baseline laboratory data were previously verified by AECOM chemists (AECOM 2018).Verification included review of the data for the field duplicate, equipment rinse blank, andmatrix spike/matrix spike duplicate (MS/MSD) quality assurance/quality control (QA/QC)samples collected during each sampling event. Validation also included review of laboratoryQA/QC data supplied with the laboratory analysis reports. AECOM also reviewed theconsistency of the Appendix III constituent concentrations for each sampling event using timeseries graphs. An example time series graph for TDS is shown as Figure 2. TDS concentrationsare consistent between sampling events, which suggests that significant laboratory analysis errorsdid not occur and that the SSIs are not a result of laboratory analysis error. Similar concentrationtrends are also observed for the other Appendix III constituents.

Statistical Evaluation Errors

Statistical evaluation errors could influence the identification of Appendix III SSIs. These errorsmight include data entry errors, lack of statistical independence between samples, outliers,constituent trends, and not detected results. Baseline Appendix III data were loaded into adatabase from the laboratory electronic data deliverables (EDDs) to minimize the potential fordata entry errors. Data in the database were also checked against the laboratory reports toconfirm that the data in the EDDs were correct. No data entry errors were found. The baseline

Memorandum

4

groundwater samples were collected at approximately 1 ½ month intervals. Travel timeestimates indicate that this time interval is sufficient to ensure statistical independence betweensamples. Prior to performing the statistical analyses the data were examined for outliers usingbox plots and outlier tests. No outliers were found. The Appendix III data were also examinedfor non-detect values. None of the Appendix III constituents with SSIs had non-detect values.The Appendix III data were also examined for constituent trends using time-series plots andMann-Kendall trend tests. No statistically significant constituent trends (positive or negative)were apparent. Statistical evaluation errors do not appear to have contributed to the Appendix IIISSIs in the downgradient Ash Monofill monitoring wells.

Natural Variation in Groundwater Quality

An SSI could also be caused by natural variations in groundwater quality that are influenced bysite geology, precipitation, seasonality, water level, changes in pH or oxidation-reductionpotential (ORP), biological activity, and time of travel. Annual precipitation during the baselinesampling period (September 2016 through July 2017) in Fort Collins, CO was 15.78 inches,which is consistent with the average annual precipitation of 15.08 inches (U.S. Climate Data2018). No evidence of significant seasonal changes in Appendix III constituent concentrationswas observed in constituent time-series graphs (Figure 2). Groundwater levels and gradientspresented in the 2017 Annual Report (AECOM 2018) were also consistent over the baselinesampling period suggesting that groundwater travel times were also consistent. No significantchanges in pH or ORP were noted during the baseline sampling period that would have increasedAppendix III constituent concentrations.

The Ash Monofill is underlain by the weathered and fractured Pierre Shale, an upper Cretaceousmarine shale formation. The Pierre Shale is recognized by the U.S. Geological Survey (Schultzet al. 1980) to be composed of many of the Appendix III constituents, including calcium [2.7 ±0.48 weight percent (wt %)], sulfur (0.37 ± 1.1 wt %), fluorine (0.71 ± 0.15 wt %), chlorine (0.16± 0.024 wt %), and boron [99 ± 49 parts per million (ppm)]; and, groundwater in the shale isknown to have poor water quality with high TDS concentrations. These constituents are largelyderived from the clays, plagioclase feldspars, calcite, dolomite, and pyrite minerals in the shale.All of these constituents are present in the groundwater at upgradient (background) well ASH-01(Table 2).

The Appendix III constituents are also present in the coal ash. To distinguish constituent sourcesderived from the Pierre Shale or coal ash, molar concentration ratios of some of the Appendix IIIconstituents were calculated for average constituent concentrations in upgradient anddowngradient groundwater and are listed in Table 3. Review of Table 3 indicates that theaverage molar ratios vary considerably between the upgradient and downgradient groundwaters,

Memorandum

5

suggesting that a source other than the Pierre Shale is likely causing the Appendix III SSIs.Some of the molar ratios (B/Cl, F/Cl, Ca/Cl, SO4/Cl) decreased in response to increased chlorideand sulfate concentrations, whereas other molar ratios (B/F and Ca/SO4) increased in response toincreased boron and calcium concentrations. The most likely source for the increased boron,calcium, chloride, and sulfate concentrations is the coal ash and comingled flue gasdesulfurization (FGD) waste disposed in the Ash Monofill. Coal ash, particularly fly ash, andFGD waste are known to contain elevated concentrations of boron, calcium, chloride, andsulfate.

Anthropogenic Sources

The Rawhide Energy Station is located on largely undeveloped rangeland in Larimer County,Colorado. Review of Google Earth satellite images shows that rangelands lie upgradient of theAsh Monofill. Offsite industrial or agricultural activities, other than cattle grazing, were notnoted upgradient or lateral to the Ash Monofill. The nearest residential properties areapproximately 0.75 mile west of the Ash Monofill. No evidence was found during our reviewthat indicated upgradient “offsite” activities are responsible for the observed Appendix III SSIs.

The Ash Monofill is located adjacent to the Phosphorus Recovery System (PRS) Impoundmentsand about ¼ mile upgradient of the Cooling Pond. Groundwater potentiometric and surfacewater elevations in the pond indicate that the Cooling Pond does not appear to influencegroundwater at the Ash Monofill, and is not likely to have caused the Appendix III SSIs.

Monitoring well ASH-03 is located at the southwest corner of the PRS impoundments as shownon Figure 1. The PRS Impoundments are used to manage sludge residuals from the Station’sWastewater Treatment Plant. An alum sludge is generated in the clarifier when metal ions(typically aluminum, iron, and calcium) are used to precipitate suspended solids from thewastewater. The sludge consists of an estimated 1 percent (%) by weight of solids, which iscomposed of approximately 40% aluminum hydroxide, 30% aluminum phosphate, and 30%various other suspended solids removed by the system. The sludge is discharged with water tothe PRS impoundments where the solids settle out and the water is allowed to evaporate.Dissolved constituents in the water likely increase in concentration as the water evaporates, oftenprecipitating salts around the receding pond extent.

A summary of average Ash Monofill Appendix III constituent concentrations at monitoring wellsASH-03, ASH-04, and ASH-05 for 2016-2017 and average PRS Impoundment surface waterconcentrations for 2005-2016 is provided in Table 1. Review of the results in Table 1 shows thatboron and chloride could be sourced from percolating PRS Impoundment surface water as theirconcentrations are higher than those in the Ash Monofill monitoring wells. However, theconcentrations of the other Appendix III constituents in the monitoring wells are significantly

Memorandum

6

higher than those in the PRS Impoundments. This suggests that the PRS Impoundments are notthe source of the SSIs at the Ash Monofill.

Findings

An ASD was performed to assess whether the observed Appendix III SSIs at the Ash Monofillare from an alternative source. As specified in 40 CFR 257.94(e)(2), alternative sources for aSSI can include errors in sampling, laboratory analysis, and statistical evaluation, naturalvariation in groundwater quality, or an anthropogenic source. Our review of these possiblealternative sources for the SSIs revealed no errors in sampling, laboratory analysis, or statisticalevaluation. Our review also did not find any likely natural variations in groundwater quality oranthropogenic (agricultural or industrial) sources that caused the SSIs. It appears that the coalash disposed in the Ash Monofill is a contributor to the source of the elevated concentrations ofAppendix III constituents that result in the SSIs observed in the baseline monitoring data.

Next Steps

The results of this certified ASD must be placed in the facility’s operating record and included inthe Annual Report for 2018 as specified in 40 CFR 257.94(e)(2).

The lack of a successful ASD for the Appendix III SSIs at the Ash Monofill requires thatassessment monitoring be initiated at the Ash Monofill per 40 CFR 257.94(e)(2) which states ifan alternate source demonstration is not successful, the owner or operator must initiate anassessment monitoring program as required under 40 CFR 257.95. The initial assessmentmonitoring event must be completed within 90 days of triggering assessment monitoring whichis assumed to be April 30, 2018, so the initial assessment monitoring event must be completedbefore July 29, 2018.

The owner or operator must prepare a written notification that an assessment monitoringprogram has been established at the Ash Monofill [40 CFR 257.94(e)(3)]. The notification mustbe placed within the facility’s operating record within 30 days of establishing the assessmentmonitoring program [40 CFR 257.105(h)(5)]. This notification must also be placed on thepublicly accessible website [40 CFR 257.107(h)(4)].

The owner or operator must also notify the Colorado Department of Health and Environment(CDPHE) and the Larimer County Health Department that an assessment monitoring programhas been initiated [40 CFR 257.106(h)(4)] and when new information has been placed in thefacility’s operating record [40 CFR 257.106(h)].

Memorandum

7

References

40 Code of Federal Regulations (CFR) Part 257. 2015. Disposal of Coal Combustion Residualsfrom Electric Utilities. Federal Register Vol. 80, No. 74. April 17.

AECOM. 2018. Ash Monofill First Annual Groundwater Monitoring and Corrective ActionReport 2016-2017 Revision 0. Platte River Power Authority Rawhide Energy Station, LarimerCounty, Colorado. January 31.

Colorado Department of Public Health and Environment. 2016. Water Quality ControlCommission Regulation 41 Basic Standards for Ground Water. December.

Electric Power Research Institute (EPRI). 2015. Groundwater Monitoring Guidance for the CoalCombustion Residuals Rule. November.

Electric Power Research Institute (EPRI). 2017. Guidelines for Development of AlternativeSource Demonstrations at Coal Combustion Residuals Sites. October.

Schultz, L.G., H. A. Tourtelot, J.R. Gill, and J.G. Boerngen. 1980. Composition and Propertiesof the Pierre Shale and Equivalent Rocks, Northern Great Plains Region. U.S. Geological SurveyProfessional Paper 1064-B. 114 pp.

U.S. Environmental Protection Agency. 2009. Statistical Analysis of Groundwater MonitoringData at RCRA Facilities, Unified Guidance. March.

Memorandum

Table 1. Comparison Average Appendix III Baseline Constituent Concentrations in DowngradientGroundwater at the Ash Monofill (2016-2017) with Average PRS Impoundments Surface WaterConcentrations (2005-2016).

Parameter (Units) Ash Monofill Groundwater(ASH-03, ASH-04, ASH-05)

PRS ImpoundmentsSurface Water

Ratio of Ash Monofill toPRS Impoundments

Boron (mg/L) 0.76 0.98 0.78

Calcium (mg/L) 448 110 4.1

Chloride (mg/L) 140 220 0.64

pH (std units) 7.12 8.75 0.81

Sulfate (mg/L) 3,096 657 4.7

TDS (mg/L) 5,116 1,476 3.5

Memorandum

Table 3. Average Molar Ratios of Appendix III Constituents in Groundwater at Monitoring Wells ASH-01(Upgradient/Background) and ASH-03, ASH-04, and ASH-05 (Downgradient).

ConstituentRatio

ASH-01(average molar ratio)

ASH-03, ASH-04, and ASH-05(average molar ratio)

B/Cl 0.024 0.018

F/Cl 0.017 0.005

B/F 1.99 3.39

Ca/Cl 15.4 2.8

Ca/SO4 0.17 0.35

SO4/Cl 31.7 8.2

!? !?

!?

!?

Cooling Pond(HamiltonReservoir)

Cell 2

Cell 1

Ash Monofill

ASH-05

ASH-03

ASH-01

ASH-04

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/AirbusDS, USDA, USGS, AeroGRID, IGN, and the GIS User Community

0 800 1,600

Scale in Feet

μFigure 1

RAWHIDE ENERGY STATIONASH MONOFILLLOCATION MAPPlatte River Power Authority Larimer County, CO

Project No.: 60514657 Date: 04-30-2018

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!? Existing Ash Monofill Well


Ash Monofill Alternate Source Demonstration

PRS Impoundments

Memorandum

Figure 2. TDS Concentrations in Ash Monofill Monitoring Wells.

CCR Groundwater Monitoring System Report Basin Electric Power Cooperative Laramie River Station

Prepared for: Basin Electric Power Cooperative AECOM1

Geoff WebbSenior Project ManagerT: 303.740.3916M: 303.885.0962E: [email protected]

AECOM6200 South Quebec StreetGreenwood Village, CO 80111aecom.com

Ash Monofill Annual Groundwater Monitoring and Corrective ......The Ash Monofill is constructed...

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