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Susitna‐Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
Mercury assessment and potential for bioaccumulation study, Study plan
Section 5.7, 2014 Study Implementation Report. [Main report] SuWa 289
Author(s) – Personal:
Author(s) – Corporate:
URS Corporation
Tetra Tech, Inc.
AEA‐identified category, if specified:
November 2015; Study Completion and 2014/2015 Implementation Reports
AEA‐identified series, if specified:
Series (ARLIS‐assigned report number):
Susitna-Watana Hydroelectric Project document number 289
Existing numbers on document:
Published by:
[Anchorage : Alaska Energy Authority, 2015]
Date published:
November 2015
(the appendix is dated October)
Published for:
Alaska Energy Authority
Date or date range of report:
Volume and/or Part numbers:
Study plan Section 5.7
Final or Draft status, as indicated:
Document type:
Pagination:
viii, 119 pages (main report only)
Related work(s):
Appendix A, Mercury assessment pathways analysis technical
memorandum
Pages added/changed by ARLIS:
Notes:
The two parts of Section 5.7 appear in separate electronic files.
All reports in the Susitna‐Watana Hydroelectric Project Document series include an ARLIS‐
produced cover page and an ARLIS‐assigned number for uniformity and citability. All reports
are posted online at http://www.arlis.org/resources/susitna‐watana/
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Mercury Assessment and Potential for
Bioaccumulation Study
Study Plan Section 5.7
2014 Study Implementation Report
Prepared for
Alaska Energy Authority
Prepared by
URS Corporation/Tetra Tech, Inc.
November 2015
STUDY IMPLEMENTATION REPORT MERCURY ASSESSMENT AND POTENTIAL
FOR BIOACCUMULATION STUDY (STUDY 5.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i November 2015
TABLE OF CONTENTS
1. Introduction ............................................................................................................................ 1
2. Study Objectives .................................................................................................................... 2
3. Study Area .............................................................................................................................. 2
4. Methods and Variances ......................................................................................................... 2
4.1. Summary of Available Information ............................................................................... 2
4.1.1. Variances from the Study Plan ............................................................................... 3
4.2. Collection and Analyses of Samples for Mercury ......................................................... 3
4.2.1. Vegetation and Soil ................................................................................................. 3
4.2.2. Water ....................................................................................................................... 3
4.2.3. Sediment and Sediment Porewater ......................................................................... 4
4.2.4. Piscivorous Birds and Mammals ............................................................................ 5
4.2.5. Fish Tissue .............................................................................................................. 6
4.3. Modeling ........................................................................................................................ 7
4.3.1. Harris and Hutchison Model ................................................................................... 7
4.3.2. Phosphorous Release Model ................................................................................... 7
4.3.3. Pathways Assessment ............................................................................................. 7
5. Results ..................................................................................................................................... 8
5.1. Summary of Available Information ............................................................................... 8
5.2. Vegetation ...................................................................................................................... 8
5.3. Soil 8
5.4. Water .............................................................................................................................. 9
5.5. Sediment and Sediment Porewater............................................................................... 10
5.5.1. Sediment ............................................................................................................... 10
5.5.2. Porewater .............................................................................................................. 10
5.6. Piscivorous Birds and Mammals .................................................................................. 10
5.7. Fish Tissue ................................................................................................................... 10
5.7.1. Lake Trout ............................................................................................................. 11
5.7.2. Longnose Sucker ................................................................................................... 11
5.7.3. Dolly Varden ......................................................................................................... 11
5.7.4. Arctic Grayling ..................................................................................................... 12
5.7.5. Burbot ................................................................................................................... 12
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5.7.6. Slimy Sculpin ........................................................................................................ 12
5.7.7. Whitefish sp. ......................................................................................................... 13
5.8. Modeling ...................................................................................................................... 13
5.8.1. Harris and Hutchison ............................................................................................ 13
5.8.2. Phosphorous Release Model ................................................................................. 13
5.8.3. Pathways Assessment ........................................................................................... 14
6. Discussion ............................................................................................................................. 16
6.1. Summary of Available Information ............................................................................. 16
6.1.1. Mercury Sources ................................................................................................... 16
6.1.2. Mercury Bioaccumulation .................................................................................... 18
6.1.3. Mercury Behavior in Reservoirs ........................................................................... 19
6.1.4. Potential Ecological Impacts ................................................................................. 20
6.2. Vegetation .................................................................................................................... 21
6.3. Soil 21
6.4. Water ............................................................................................................................ 22
6.5. Sediment and Sediment Porewater............................................................................... 22
6.6. Piscivorous Birds and Mammals .................................................................................. 23
6.7. Fish Tissue ................................................................................................................... 24
6.8. Modeling ...................................................................................................................... 25
6.8.1. Harris and Hutchison ............................................................................................ 26
6.8.2. Phosphorous Release Model ................................................................................. 27
6.8.3. Pathways Assessment ........................................................................................... 27
7. Completing the Study .......................................................................................................... 28
8. Literature Cited ................................................................................................................... 28
9. Tables .................................................................................................................................... 36
10. Figures .................................................................................................................................. 76
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LIST OF TABLES
Table 4.2-1. Sampling Parameters and Media ............................................................................. 36
Table 4.2-2. Vegetation and Soil Sample Locations .................................................................... 36
Table 4.2-3. Baseline Water Quality Monitoring Sites ................................................................ 38
Table 4.2-4. Focus Area Water Monitoring Sites ........................................................................ 38
Table 5.1-1. Historic Mercury Concentrations at Gold Creek (PRM 140.1) ............................... 39
Table 5.1-2. Historic Mercury Concentrations at Susitna at Parks Highway East (PRM 87.8) .. 40
Table 5.1-3. Historic Mercury at Susitna Station (PRM 29.9) .................................................... 41
Table 5.1-4. ADEC Mercury Statewide Data Compared to Susitna-Watana .............................. 43
Table 5.1-5. ADEC Mercury Data from Susitna Watershed ....................................................... 44
Table 5.1-6. Mercury in Cook Inlet Freshwater Sediments and Slimy Sculpin Tissue ............... 45
Table 5.1-7. Mercury Partitioning in Cook Inlet Freshwater Sediments and Fish ...................... 46
Table 5.1-8. WACAP Data for Lichen Samples .......................................................................... 47
Table 5.1-9. WACAP sand USGS Data for Alaska Fish ............................................................. 47
Table 5.2-1. Plant Species Observed and Collected at Each Sample Site ................................... 48
Table 5.2-2. Vegetation Results .................................................................................................... 49
Table 5.3-1. Soil Results ............................................................................................................... 51
Table 5.4-1 Surface Water Results Baseline Water Quality ......................................................... 54
Table 5.4-2. Surface Water Results Focus Areas ......................................................................... 59
Table 5.5-1. Sediment and Porewater Results .............................................................................. 61
Table 5.5-2. Sediment and Porewater Results .............................................................................. 62
Table 5.6-1 Results for Mammal Samples .................................................................................... 63
Table 5.7-1. Lake Trout Analytical Results .................................................................................. 64
Table 5.7-2. LNS Analytical Results ............................................................................................ 65
Table 5.7-3. Dolly Varden Analytical Results .............................................................................. 66
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Table 5.7-4. Arctic Grayling Analytical Results .......................................................................... 67
Table 5.7-5. Burbot Muscle Tissue Analytical Results ................................................................ 68
Table 5.7-6. Burbot Liver Analytical Results ............................................................................... 68
Table 5.7-7. Slimy Sculpin (Whole Body) Analytical Results ..................................................... 69
Table 5.7-8. Whitefish (sp.) Analytical Results ............................................................................ 70
Table 5.8-1. Predicted Peak MeHg Concentrations in Fish .......................................................... 71
Table 5.8-2. Factors that Influence Potential Bioavailability of MeHg ....................................... 72
Table 6.1-1 Mercury in Soil and Vegetation ................................................................................ 73
Table 6.5-1 Mercury SQuiRT Standards in Sediment .................................................................. 74
Table 6.8.1. Comparison Between Predicted Peak MeHg Concentrations in Fish ....................... 75
LIST OF FIGURES
Figure 3.1. Water Quality Sample Locations ............................................................................... 77
Figure 4.2-1. Vegetation and Soil Sampling Locations ............................................................... 78
Figure 4.2-2. Vegetation and Soil Sample Location: Site 1 ........................................................ 79
Figure 4.2-3. Vegetation and Soil Sample Location: Site 2 ........................................................ 80
Figure 4.2-4. Vegetation and Soil Sample Location: Site 3 ........................................................ 81
Figure 4.2-5. Vegetation and Soil Sample Location: Site 4 ........................................................ 82
Figure 4.2-6. Vegetation and Soil Sample Location: Site 5 ........................................................ 83
Figure 4.2-7. Vegetation and Soil Sample Location: Site 6 ........................................................ 84
Figure 4.2-8. Vegetation and Soil Sample Location: Site 7 ........................................................ 85
Figure 4.2-9. Vegetation and Soil Sample Location: Site 8 ........................................................ 86
Figure 4.2-10. Vegetation and Soil Sample Location: Site 9 ...................................................... 87
Figure 4.2-11. Vegetation and Soil Sample Location: Site 10 .................................................... 88
Figure 4.2-12. Focus Area Sampling Location Overview ........................................................... 89
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Figure 4.2-13. Example Detail of Focus Area 104: Whiskers Slough ......................................... 90
Figure 4.2-14. Detail of Focus Area 113: Oxbow I. .................................................................... 91
Figure 4.2-15. Detail of Focus Area 115: Slough 6A. ................................................................. 92
Figure 4.2-16. Detail of Focus Area 128: Slough 8A. ................................................................. 93
Figure 4.2-17. Detail of Focus Area 138: Gold Creek. ................................................................ 94
Figure 4.2-18. Detail of Focus Area 141: Indian River. .............................................................. 95
Figure 4.2-19. Detail of Focus Area 144: Side Channel 21. ........................................................ 96
Figure 4.2-20. Map of Sediment/Porewater Sampling Locations ................................................ 97
Figure 4.2-21. Sediment and Porewater Sample Locations for Goose and Jay Creeks ............... 98
Figure 4.2-22. Sediment and Porewater Sample Locations for Kosina Creek and Oshetna River
....................................................................................................................................................... 99
Figure 4.2-23. Sediment and Porewater Sample Locations for Above and Below Dam Site ... 100
Figure 4.2-24. Sediment and Porewater Sample Locations for Watana and Tsusena Creeks ... 101
Figure 4.2-25. Sediment and Porewater Sample Locations for Deadman and Fog Creeks ....... 102
Figure 4.2-26. Fish Tissue Sample Collection Locations .......................................................... 103
Figure 5.1-1. ADEC Fish Tissue Sample Collection Locations ................................................ 104
Figure 5.1-2. USGS (Frenzel 2000) Sample Locations ............................................................. 105
Figure 5.4-1. Total Mercury by Location in Mainstem Susitna River ....................................... 106
Figure 5.4-2. Total Mercury over Time at Susitna Station (PRM 29.9) .................................... 106
Figure 5.6-1. Sample Locations for Piscivorous Mammals ....................................................... 107
Figure 5.7-1. Lake Trout Fork Length and Age ......................................................................... 108
Figure 5.7-2. Lake Trout Fork Length and Total Hg (dw) ........................................................ 108
Figure 5.7-3. LNS Fork Length and Age ................................................................................... 109
Figure 5.7-4. LNS Fork Length and Total Hg (dw) ................................................................... 109
Figure 5.7-5. Dolly Varden Fork Length and Total Hg (dw) .................................................... 110
Figure 5.7-6. Arctic Grayling Fork Length and Age in the Upper Susitna ............................... 110
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Figure 5.7-7. Arctic Grayling Fork Length and Total Hg (dw) ................................................. 111
Figure 5.7-8. Burbot Fork Length and Total Hg (dw) ............................................................... 111
Figure 5.7-9. Slimy Sculpin Fork Length and Total Hg (dw) ................................................... 112
Figure 5.7-10. Round Whitefish Fork Length and Age ............................................................. 112
Figure 5.7-11. Round Whitefish Fork Length and Total Hg (dw) ............................................. 113
Figure 5.8-1. Factors that Effect Mercury Bioconcentration and Bioaccumulation. ................. 114
Figure 5.8-2. Potential Mercury Processes Under Existing Conditions. ................................... 115
Figure 5.8-3. Sediment Mercury Concentrations Under Existing Conditions ........................... 115
Figure 5.8-4. Porewater Mercury Concentrations Under Existing Conditions. ......................... 116
Figure 5.8-5. Sediment Selenium Concentrations Under Existing Conditions. ........................ 116
Figure 5.8-6. Surface Water pH Conditions at Sediment Interface Under Existing Conditions.
..................................................................................................................................................... 117
Figure 5.8-7. Surface Water Temperature Conditions at Sediment Interface Under Existing
Conditions. .................................................................................................................................. 117
Figure 5.8-8. Surface Water Dissolved Oxygen Concentrations at Sediment Interface Under
Existing Conditions. .................................................................................................................... 118
Figure 5.8-9. Surface Water Reduction/Oxidation Potential at the Sediment Interface Under
Existing Conditions. .................................................................................................................... 118
Figure 6.7-1. Comparison Between Fish Age and Mercury Concentrations. ............................ 119
Figure 6.7-2. Arctic Grayling Mean Size and Total Hg Comparison. ....................................... 119
LIST OF APPENDICES
Appendix A - Mercury Assessment Pathways Analysis Technical Memorandum
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LIST OF ACRONYMS, ABBREVIATIONS, AND DEFINITIONS
Abbreviation Definition
AEA Alaska Energy Authority
ADEC Alaska Department of Environmental Conservation
ADF&G Alaska Department of Fish and Game
AK-DHSS Alaska Department of Health and Social Services
APA Alaska Power Authority
AWQS Alaska Water Quality Standards
CFR Coe of Federal Regulations
CIRWG Cook Inlet Region Working Group
Cm Centimeter
DO dissolved oxygen
Dw dry weight
DNP Denali National Park
EFDC Environmental Fluid Dynamics Code
ELA Experimental Lakes Area
EPA U.S. Environmental Protection Agency
F Female
FAMS Florida Atmospheric Mercury Study
FERC Federal Energy Regulatory Commission
FDA Food and Drug Administration
g gram
GAAR Gates of the Arctic National Park
Hg Mercury
HgS Hydrogen sulfide
ILP Integrated licensing process
ISR Initial Study Report
Kg Kilogram
Km2 Square kilometer
Km3 Cubic kilometer
LNS longnose suckers
LOER Lowest observed effects residue
m male
m2 square meters(s)
MeHg Methylmercury
mm Millimeters
MW Megawatts
ng Nanograms
ng/g nanograms per gram
ng/l nanograms per liter
ng/m2/yr. nanograms per square meter per year
NOAA National Oceanic and Atmospheric Administration
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Abbreviation Definition
NOAT Noatak National Preserve
NOER No observed effects residue
NM Not measured
NS Not sampled
Project Susitna-Watana Project
PRM Project River Mile
QAPP Quality Assurance Project Plan
QA/QC quality assurance/quality control
RSP Revised Study Plan
Sp. Species
SPD Study Plan Determination
SQuiRTs Screening Quick Reference Tables
THg Total mercury
TOC total organic carbon
µg Microgram
µg/kg microgram per kilogram
µg/L micrograms per liter
USFWS U.S. Fish and Wildlife Service
UV Ultraviolet
USGS U.S. Geological Survey
WACAP Western Airborne Contaminants Assessment Project
WSENP Wrangell-St. Elias National Park
ww wet weight
Yr. Year
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1. INTRODUCTION
On December 14, 2012, Alaska Energy Authority (AEA) filed with the Federal Energy
Regulatory Commission (FERC or Commission) its Revised Study Plan (RSP), which included
58 individual study plans. Included in the Study Plan was the Mercury Assessment and Potential
for Bioaccumulation Study, Section 5.7. This part of the study focuses on determining the
current concentrations and methylation rates for mercury in the study area, and what changes
could occur with construction of the Susitna-Watana Project (Project) reservoir.
On February 1, 2013, FERC staff issued its study determination (February 1 Study Plan
Determination (SPD) for 44 of the 58 studies, approving 31 studies as filed and 13 with
modifications. On April 1, 2013 FERC issued its study determination (April 1 SPD) for the
remaining 14 studies; approving one study as filed and 13 with modifications. Study Plan
Section 5.7 was one of the 13 approved with modifications. In its April 1 SPD, FERC
recommended the following:
Use of Harris and Hutchinson and EFDC Models for Mercury Estimation
We recommend that AEA use the more sophisticated Phosphorus Release Model to
predict peak methylmercury levels in fish tissue, regardless of the outcome of the
other two models.
Mercury Effects on Riverine Receptors
We recommend that AEA include likely riverine receptors (i.e., biota living
downstream of the reservoir that may be exposed to elevated methylmercury
concentrations produced in the reservoir and discharged to the river) as part of the
predictive risk analysis. The additional study element would have a low cost
(section 5.9(b)(7)) because AEA would simply add consideration of additional
receptors to the existing analysis. This information is necessary to evaluate
potential project effects downstream of the reservoir (section 5.9 (b)(5)).
In accordance with the April 1 SPD, AEA has adopted the FERC requested modifications.
Following the first study season, FERC’s regulations for the Integrated Licensing Process (ILP)
require AEA to “prepare and file with the Commission an initial study report describing its
overall progress in implementing the study plan and schedule and the data collected, including an
explanation of any variance from the study plan and schedule.” (18 CFR 5.15(c)(1)) On June 3,
2014, AEA filed with the Commission the Initial Study Report (ISR) on Mercury Assessment
and Potential for Bioaccumulation in accordance with FERC’s ILP regulations. The ISR details
AEA’s status in implementing the study, as set forth in the FERC-approved RSP as modified by
FERC’s April 1 SPD and the Quality Assurance Project Plan for Mercury Assessment and
Potential for Bioaccumulation Study for the Susitna-Watana Hydroelectric Project (QAPP)
(collectively referred to herein as the “Study Plan”).
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2. STUDY OBJECTIVES
Previous studies have documented increased mercury concentrations in fish and wildlife
following the flooding of terrestrial areas to create hydroelectric reservoirs. The purpose of this
study is to assess the potential for such an occurrence in the proposed Project area. The study
objectives as established in Study Plan (Section 5.7.1) are as follows:
Summarize available and historic mercury information for the Susitna River basin,
including data collection from the 1980s Alaska Power Authority (APA) Susitna
Hydroelectric Project.
Characterize the baseline mercury concentrations of the Susitna River and tributaries.
This will include collection and analyses of vegetation, soil, water, sediment pore water,
sediment, piscivorous birds and mammals, and fish tissue samples for mercury.
Utilize available geologic information to determine if a mineralogical source of mercury
exists within the inundation area.
Map mercury concentrations of soils and vegetation within the proposed inundation area
and use this information to develop maps of where mercury methylation may occur.
Use the water quality model to predict where in the reservoir conditions (pH, dissolved
oxygen [DO], turnover) are likely to be conducive to methylmercury (MeHg) formation.
Use modeling to estimate MeHg concentrations in fish.
Assess potential pathways for MeHg to migrate to the surrounding environment.
Coordinate study results with other study areas, including fish, instream flow, and other
piscivorous bird and mammal studies.
3. STUDY AREA
As established in Study Plan Section 5.7.3, the study area begins at project river mile (PRM)
19.9 and extends upstream from the proposed reservoir to PRM 235.2 (Figure 3-1).
4. METHODS AND VARIANCES
The following section provides a brief summary of the tasks performed, the methods utilized,
and any variances from the methods described in the Study Plan (Section 5.7.4 of the RSP 5.7).
4.1. Summary of Available Information
Existing literature was reviewed to summarize the current understanding of the occurrence of
mercury in the environment. This review was previously presented in the study plan and the ISR
Section 5.7 filed June 3, 2014. Information derived from the initial review has been carried
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forward here for use as a comparison to data generated as part of this study. Sources included
the following:
APA Susitna Hydroelectric Project
Alaska Department of Environmental Conservation
U.S. Geological Survey (Frenzel 2000)
Western Airborne Contaminants Assessment Project (WACAP)
Jewett and Duffy (2007)
Geologic Data in ISR Section
4.1.1. Variances from the Study Plan
AEA implemented this portion of the plan using the methods as described in the Study Plan
(Section 5.7.4 of the RSP 5.7) with no variances.
4.2. Collection and Analyses of Samples for Mercury
Samples were collected from vegetation, soil, surface water, sediment, sediment pore water, and
fish tissue (Table 4.2-1). The sample methods have been detailed in the study plan and in ISR
Section 5.7. The ISR also includes any variances from the study plan.
In most cases the samples were collected in 2013, however, the analytical results were received
from the laboratory too late for inclusion in ISR Section 5.7. Those results are presented in this
report. The following sections provide a brief description of the work performed, and any
additional variances that were encountered in 2014.
4.2.1. Vegetation and Soil
Vegetation and soil samples were collected from within the proposed inundation zone in August
2013. Samples were collected from five sites at each of ten locations (Figure 4.2-1 through 4.2-
11 and Table 4.2-2). The sampling methods and preliminary results were previously discussed in
the ISR Section 5.7. Analytical results are presented in this report.
4.2.1.1. Variances from the Study Plan
No additional work was performed in 2014, and thus there were no variances in addition to the
soil sampling method variance that occurred in 2013 as noted in the ISR Section 4.2.2.1.
4.2.2. Water
There were two types of monitoring programs used to characterize mercury concentrations in
surface waters: Baseline Water Quality Monitoring (Study 5.5, Section 5.5.4.4) and Focus Area
Monitoring (Study 5.5, Section 5.5.4.5). These programs were distinguished by the frequency of
water sampling, the density of sampling effort in a localized area, and parameters analyzed.
Sampling programs for the surface water were initiated in 2013 and carried through to 2014.
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4.2.2.1. Baseline Sampling Protocols
For the baseline sampling protocols, water quality data collection occurred at various intervals
from the mouth of the river to above the inundation zone (Figure 3.1 and Table 4.2-3). The
sampling methods were previously discussed in the ISR Section 5.7 filed June 3, 2014.
Analytical results are presented in this report.
4.2.2.2. Focus Area Sampling Protocols
The Focus Areas had a higher density of sampling locations, in contrast to the mainstem
network, so that prediction of change in water quality conditions from Project operations could
be made with a higher degree of resolution. These were discrete samples taken at each collection
point (Figure 4.2-12 to 4.2-19 and Table 4.2-4). The sampling methods were previously
discussed in the ISR Section 5.7 filed June 3, 2014. Analytical results are presented in this report.
4.2.2.3. Variances from the Study Plan
Per Section 5.7.4.2.3 of the RSP, water quality sampling for mercury was supposed to be
discontinued after the March 2014 sampling if mercury concentrations did not exceed regulatory
criteria or thresholds. However, additional total mercury sampling was performed in 2014 due to
laboratory results that were qualified as “estimated”, and to further fine-tune a mercury model
pathways analysis. This decision was detailed in ISR Section 5.7 Part C: Executive Summary
and Section 7 filed June 3, 2014. This variance should enhance the results of this study.
4.2.3. Sediment and Sediment Porewater
In 2013 sediment samples were collected at four of the ten proposed sample locations at mouths
of Jay, Kosina, and Goose creeks, and the Oshetna River at the downstream of islands, and in
similar riverine locations in which water velocity was slowed, favoring accumulation of finer
sediment along the channel bottom. As detailed in ISR Section 5.7 Part C: Executive Summary
and Section 7 dated June 2014, the remaining sites could not be accessed in 2013, and were
sampled in 2014. These remaining sites were from the mainstem Susitna River just above and
below the proposed dam site, and at the mouths of Fog, Tsusena, Deadman, Watana, and Kosina
Creeks. The analytical results of the sediment sampling in 2013 were received from the contract
laboratory too late for inclusion in the ISR Section 5.7 dated June 3, 2014 and are included here
along with the 2014 results. A map of all the sediment/porewater sampling locations is shown in
Figure 4.2-20. Images of each sampling location can be seen in Figures 4.2-21 and 4.2-25.
4.2.3.1. Variances from the Study Plan
Sediment in the upper Susitna River was generally very coarse at accessible sample locations.
At each sample location several test pits were dug to attempt to locate the finest grained sediment
for sampling, however, only 30% of the samples had more than 5% fines as required in the Study
Plan. This does not appear to have adversely impacted the study results because mercury
concentrations in the sediments appear to be only poorly correlated with grain size, and sites with
few fines had similar mercury concentrations to those with more fines.
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As detailed in ISR Section 5.7 Part C: Executive Summary and Section 7 dated June 2014,
sample locations for sediment, and sediment porewater sites in the Upper River were modified
slightly due to lack of access (landing access for helicopters, river stage levels, property
ownership, and boat availability) (ISR Section 4.2.4.1.). These minor modifications to proposed
sample locations in the Upper River did not impact AEA’s ability to meet the study objectives.
4.2.4. Piscivorous Birds and Mammals
The purpose of the bird and mammal surveys was to collect biological specimens (fur and
feathers) and test them for mercury. An important part of this study is to collect, to the
maximum extent possible, biological specimens from the immediate vicinity of the inundation
area. This would allow the mercury concentrations found to be correlated with mercury
concentrations observed in fish, water, sediment, soil and vegetation. Mammals and birds from
other drainages may be exposed to higher or lower mercury concentrations, and data from those
sources may not be relevant to this study.
The drawback of this approach is residency. If the birds and mammals are not present, or present
at very low population levels, then it may not be possible to locate bird or mammal samples for
sample collection.
Because of the small populations, there were concerns that lethal sampling techniques would
adversely impact populations, and only non-lethal methods (salvaging feathers from nests, fur
snags), and purchasing furs from commercial trappers, were utilized.
4.2.4.1. Birds
AEA submitted a discussion of this issue in the ISR Section 5.7, Part C: Executive Summary and
Section 7 (June 2014). Attempts at collecting samples were unsuccessful due to the low
populations of piscivorous birds in the area. In addition,
Feathers of Bald Eagles could not be collected because the study team and the U.S. Fish
and Wildlife Service (USFWS) did not possess the necessary federal permit for salvage
of eagle feathers, and the permit could not be obtained in time to collect samples in the
2013 season.
Lack of access to Cook Inlet Region Working Group (CIRWG) lands in 2013 limited the
number of areas where nests could be examined; however, populations of piscivorous
birds in the inundation area appear to be relatively low, and it is not clear whether access
to CIRWG lands would have improved the study results.
Opportunistic collection of feathers from some species of piscivorous birds (Belted
Kingfisher and Osprey) for mercury analysis, as described in RSP Section 10.16.4.6, was
unsuccessful because these species do not appear to be resident in the study area.
For these reasons, it was determined that the results from mercury analysis of wildlife tissues
will not be necessary until the predictive reservoir and riverine models are complete and can
provide an accurate evaluation of the potential for transfer from the aquatic environment to the
terrestrial environment. The vegetation, soil, sediment, and fish tissue samples will be used to
perform a pathways analysis of potential bioaccumulation of mercury and MeHg throughout the
food chain. The results of the pathways analysis will help to determine the need for additional
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sample collection from birds. No additional work was completed on this task, and no new results
were generated in 2014.
4.2.4.2. Mammals
As noted in the study plan (Section 5.7.4.4) populations of piscivorous mammals are relatively
small in the study area, and sampling efforts collected few samples. Further hampering efforts
was an attempt to avoid a lethal take, which would damage the relatively small populations of
these species. The study plan specified that an attempt would be made to collect samples by the
following means:
Obtain fur samples from river otters and mink from animals harvested by trappers in the
study area.
Utilize data obtained in other studies on background concentrations of MeHg in natural
northern environments.
Place hair-snag “traps” at or near the mouths of tributaries near the proposed dam site,
including Fog, Deadman, Watana, Tsusena, Kosina, Jay, and Goose creeks, and the
Oshetna River.
4.2.4.3. Variances from the Study Plan
4.2.4.3.1. Birds
ISR Section 5.7 Part C: Executive Summary and Section 7 dated June 2014 describes the
variances for the sampling. No additional variances have occurred since that report was
submitted.
4.2.4.3.2. Mammals
During the aquatic furbearers study (Study 10.11) evidence of aquatic furbearers (tracks) was
only observed on Kosina and Deadman Creeks. Hair snags were not placed at the remaining
creeks.
In ISR Section 5.7 Part C: Executive Summary and Section 7 dated June 2014, the decision to
collect additional samples from piscivorous mammals has been deferred until the pathways
analysis has been completed and a determination made as to the potential for mercury to
bioaccumulate in aquatic receptors. If there is a potential for mercury transfer from aquatic to the
terrestrial environment, additional sampling may be performed.
4.2.5. Fish Tissue
The sampling methods and preliminary results were previously discussed in the ISR Section 5.7
dated June 3, 2014. Analytical results are presented in this report. No additional sampling or
analyses was performed in 2014.
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4.2.5.1. Variances from the Study Plan
Variances from the study plan were detailed in ISR Section 5.7 Part C: Executive Summary and
Section 7 dated June 2014. No additional variances are noted.
4.3. Modeling
4.3.1. Harris and Hutchison Model
A detailed description of the Harrison and Hutchison model was presented in the Study Plan
(Section 5.7.4 of the RSP 5.7). This model is a linear regression model based on studies of the
relationship between various reservoir parameters and the resulting mercury concentrations seen
in fish after reservoir construction. The model assumes that the primary source of MeHg in a
new reservoir is the flooded terrain, while the primary MeHg removal mechanism is
outflow/dilution. The highest MeHg concentrations in fish are therefore associated with
reservoirs that flood large areas, but have low flow-through. The results are adjusted for
piscivorous and non-piscivorous species of fish. The use of area in the calculation reflects an
assumption that MeHg removal mechanisms other than outflow are primarily related to reservoir
area (e.g., photodegradation, burial and sediment demethylation) rather than reservoir volume.
4.3.2. Phosphorous Release Model
A detailed description of the Phosphorous Release model was presented in the Study Plan
(Section 5.7.4 of the RSP 5.7). This model is not necessarily more accurate than the Harrison
and Hutchison model, and in fact may be slightly less accurate given the larger number of
parameters necessary to perform the calculations. However, it has the added benefit of
predicting when peak mercury concentrations are likely to occur after inundation, and how long
they are likely to persist. The model pays special attention to flood zone characteristics, because
decomposition of organic materiel after flooding is a key driver for increases in MeHg levels in
new reservoirs.
The model is semi-empirical: decaying organic material releases phosphorous at a set rate (the
phosphorus release curve), which controls decomposition of the organic material in the
inundation zone. This turns out to be a fairly accurate measure of the bioavailability of mercury
for fish, and can be used to predict mercury concentrations in muscle tissues.
Note that the predictions from this model generally tend to overestimate mercury concentrations
that will occur. This situation reflects a conscious choice on the part of the developers of the
formula to be conservative with their predictions.
4.3.3. Pathways Assessment
A detailed description of the pathways assessment method was presented in the Study Plan
(Section 5.7.4 of the RSP 5.7). Potential for bioaccumulation of mercury in aquatic life is
evaluated by reviewing water quality conditions that would increase mercury concentrations.
Examples of parameters that increase mercury concentrations are: low pH, low dissolved oxygen
concentrations, increased nutrients, increased temperature and several others.
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The pathways assessment is intended to identify water quality characteristics that would increase
mercury concentrations under different operational scenarios. Potential for bioaccumulation of
mercury during post-Project scenarios will be evaluated by inserting predicted water quality
conditions from the Environmental Fluid Dynamics Code (EFDC) into the pathways assessment
model. A separate pathways assessment for mercury will use the predicted water quality
conditions to evaluate potential for bioaccumulation during each operational scenario in the
reservoir and immediately below the dam.
The pathways assessment cannot be fully completed until the modeling for the reservoir is
complete (Study 5.6). However, the potential pathways assessment and impacts for existing
conditions in the inundation zone is presented in this report.
4.3.3.1. Variances from the Study Plan
There were no variances to the modeling methods described in the study plan.
5. RESULTS
5.1. Summary of Available Information
The available information on the concentrations of mercury in various media in Alaska is
extensive and fairly well documented. This information was summarized in the ISR Section 5.7
dated June 3, 2014. Additional information on mercury concentrations in Alaska fish has been
added (USGS 2014). Information generated from the review is summarized on Tables 5.1-1 to
5.1-9, and Figures 5.1-1 to 5.1-2.
5.2. Vegetation
The vegetation found at each of the sample sites is shown on Table 5.2-1, and was previously
summarized in the ISR Section 5.7. The analytical results of the vegetation analyses were
received from the contract laboratory too late for inclusion in the ISR and are presented in Table
5.2-2. In summary, there was little difference in the mercury concentrations between the various
sample locations inside the inundation zone. Concentrations of total mercury ranged from 7.00
to 16.1 nanograms per gram (ng/g) dw (dry weight), and 2.06 to 4.36 ng/g wet weight (ww)
(Table 5.2-2). There was little correlation between plant species and mercury concentrations,
which is consistent with the fact that relatively few species such as alder, willow, bog blueberry,
and low bush cranberry made up a majority of the vegetative mass at most locations.
5.3. Soil
As reported in the ISR Section 5.7, the soil samples each consisted of a combination of surface
moss, peat, and mineral soil (Table 5.3-1). At each sample location there was a significant
fraction of organic material (moss and peat) above the mineral soil. This material is the primary
potential source of mercury methylation in the reservoir after impoundment.
The analytical results of the soil analyses were received from the contract laboratory too late for
inclusion in the ISR and are presented here. Total mercury concentrations in the soil ranged
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from 27.1 to 119 ng/g dw, with a mean of 61 ng/g dw. The highest concentration of mercury
seemed to be located at SITE-3, which was also found to have the thickest accumulation of peat
in all the sample areas. Peat is well known as an ac cumulator and concentrator of mercury in
the environment (Mitchell et al. 2008).
Periodic detections of relatively high (> 1 ng/g) concentrations of MeHg were observed as well
(Table 5.3-1). These elevated detection had little effect on the total mercury concentration.
There was very little difference in the reported total mercury concentrations based on the type of
extraction method utilized. MeHg concentrations were generally found to be 2-3 times higher
using the organic extraction method; however, detection limits were also elevated, reducing the
value of this method.
5.4. Water
The analytical results of the water sampling were received from the contract laboratory too late
for inclusion in the ISR Section 5.7 dated June 14, 2014 and are summarized on Tables 5.4-1 and
5.4-2. The complete results are available at the Susitna project data website, and the Baseline
Water Quality Site Completion Report (Study 5.5). The following is a summary of the results:
There was very little difference in mercury concentrations collected in the middle of the
river to those collected at the margins, and little difference in mercury concentrations
with depth, suggesting the mercury present is well mixed in the river.
Total mercury concentrations ranged from 78.3 nanograms per liter (ng/L) to non-detect
(<0.5 ng/L).
Samples analyzed for dissolved mercury typically were one to two orders of magnitude
lower concentration than total mercury. The highest dissolved concentration of mercury
in water was 1.7 ng/L; however, most detections were at or below the detection limit (0.5
ng/L).
The 2013 total mercury data should be considered an estimate. While the samples were
collected and analyzed according to the Study Plan and appropriate guidance from EPA
and ADEC, high concentrations of suspended solids are believed to have biased the
results high. This is discussed in more detail in Water Quality Study Completion Report
(Study 5.5).
Concentrations of mercury generally decreased moving up river from Susitna Station
(PRM 29.9) to Oshetna River (PRM 235.2) (see Figure 5.4-1).
There is a strong seasonal component in the mercury concentrations, with higher
concentrations noted in the spring, and diminishing in the fall and winter (Figure 5.4-2).
Mercury is largely absent from the river water in the winter. This change tracks the
seasonal suspended sediment concentrations in the river.
The Deshka River has a significantly lower mercury concentration than the main stem
Susitna River.
Similar ranges of mercury concentrations were observed in the focus area samples,
suggesting that the focus areas are no more prone to mercury accumulation than the main
stem Susitna River.
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5.5. Sediment and Sediment Porewater
5.5.1. Sediment
Figures 4.2-20 to 4.2-25 show the sampling areas selected for the study. Sediment
concentrations of mercury ranged from 1.00 to 17.4 ng/g total mercury dw (Table 5.5-1).
Sediment tended to be fairly coarse grained in the upper river, with little fines (Table 5.5-2).
5.5.2. Porewater
Porewater samples were co-located with sediment samples. Results ranged from non-detect (<
0.51 ng/L) to 9.54 ng/L. In general the results were fairly low, with 24 of the 30 analytical
results under 2 ng/L (Table 5.5-1). This suggests that there is currently a very low primary
productivity of mercury in the river.
5.6. Piscivorous Birds and Mammals
No additional attempts at sampling tissues from piscivorous birds were performed, and as
detailed in the ISR Section 5.7, Part C: Executive Summary and Section 7 (June 2014), there are
no plans to attempt any additional tissue sample collection.
Fur samples from river otters and mink were sought from animals harvested by trappers in the
study area in 2013. However, state regulations prevent identification of trappers and harvest
locations using ADF&G data. The information was discussed in the ISR Section 5.7.
One river otter pelt and two mink pelts were obtained in late winter 2014 from a trapper who
harvested them near Chulitna River/Indian River (Figure 5.6-1). The exact location where the
furs were trapped was not recorded. The furs had been dried, but not tanned. Both the fur and
the pelt were analyzed for mercury. Concentrations were nearly identical for all three furs,
ranging from 6,330 to 7,670 ng/g dw (Table 5.6-1).
Eight hair snares were set at two main locations on March 8, 2014 - four were set at three sites
along Kosina Creek and four snags were set at three sites near Deadman Creek. The hair snags
were checked on March 25 and April 11, 2014 with no reported collection. One additional hair
snag was deployed along Kosina Creek on April 11, 2014. All snares were removed on April 23,
2014.
The effort produced only four hairs from a single river otter at one of the sites. Despite the low
sample volume, the sample was analyzed for total mercury and the results indicated a mercury
concentration of 417 ng/g ww. No other analyses could be performed due to the small sample
size.
5.7. Fish Tissue
The following sections discuss the available data on a species by species basis. While the fish
tissue samples were collected in 2013 and sampling details incorporated in the ISR Section 5.7
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dated June 3, 2014, the analytical results were received from the contract laboratory too late for
inclusion in the ISR and are presented here.
5.7.1. Lake Trout
Lake trout were collected from Sally Lake and Deadman Lake which would be hydrologically
connected to the proposed reservoir after filling (Figure 4.2-26). Otoliths were extracted from all
seven of these fish. While lake trout were present in Cushman Lake, none were caught during
the study period.
Previous studies of lake trout from various lakes in the Susitna drainage and in Deadman Lake
(Burr 1987) found there to be a good relationship between fish fork length and age (Figure
5.7-1). It should be noted that the relationship between lake trout length to age may be lake
specific, and even small changes in lake conditions can impact growth significantly (Burr 1987).
Based on otolith data extracted from the lake trout, the fish captured for this study ranged from 7
to 26 years old, which is consistent with the information from Burr (1987) (Figure 5.7-1).
The fish ranged in size from 355 to 625 millimeters (mm) fork length, and 500 to 2,200 grams
(g) in weight (Table 5.7-1. As anticipated, lake trout showed the highest concentration of
mercury in their tissues, and the concentration was closely related to the size of the fish (Figure
5.7-2). Concentrations ranged from 136 to 637 ng/g total mercury ww, and 592 to 2,920 ng/g
dw. As anticipated, a majority, if not all, of this mercury is MeHg (Table 5.7-1).
5.7.2. Longnose Sucker
A total of seven longnose suckers (LNS) were captured from the river. Five of these fish were
captured at the confluence of the Susitna and Oshetna Rivers, the remainder in the mainstem
Upper Susitna River (Figure 4.2-26). The fish ranged in size from 315 to 430 mm, and in weight
from 303 to 500 g (Table 5.7-2). Otoliths were successfully extracted from 5 of these fish.
Previous studies of the LNS in the Susitna Middle River (APA 1984b) found there to be a good
relationship between fish fork length and age (Figure 5.7-3). Based on that relationship and the
data collected in this study, the LNS captured in this study ranged from seven to over 13 years
old.
Mercury concentrations in the fish tissue ranged from 33.1 to 640 ng/g ww, and 153 to 640 ng/g
dw (Table 5.7-2). There appeared to be a poor correlation between fish size and mercury
concentration (Figure 5.7-4), which may be due to the narrow range of fish sizes sampled. As
anticipated, a majority, if not all, of this mercury is MeHg.
5.7.3. Dolly Varden
Dolly Varden were found to be rare in the inundation zone, with the only area of their occurrence
being the upper Watana Creek (Figure 4.2-26). A total of seven fish were captured from this
location. The fish narrowly ranged in size from 177 mm to 204 mm, and in weight from 47 g to
70 g (Table 5.7-3). Otoliths were successfully extracted from four of the fish as part of this study.
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The fish were found to be essentially the same age, and had mercury concentrations ranging from
20.8 to 83.7 ng/g ww, and 88.3 to 359 ng/g dw (Table 5.7-3). Only a weak correlation was found
between fish size and mercury concentration (Figure 5.7-5). This may be because of the narrow
range of sizes sampled. As anticipated, a majority, if not all, of this mercury is MeHg.
5.7.4. Arctic Grayling
A total of 16 Arctic grayling were captured as part of this study. Most were captured from
Kosina Creek in 2013, where the species appears to be plentiful (Figure 4.2-26). The fish ranged
in size from 75 mm to 340 mm, and in weight from 12 g and 385 g (Table 5.7-4). Two fish were
also captured in 2012 from Watana Creek, and one was captured from the Oshetna River. Some
of the fish captured appeared to be juveniles (<2 years old), however, the field crews were
directed to keep any fish accidentally killed during other studies for inclusion in this study. No
otoliths were successfully extracted from Arctic grayling.
Previous studies of the Arctic grayling in the Upper Susitna River (APA 1984a) found there to be
a good relationship between fish fork length and age (Figure 5.7-6). Using this data, it would
appear that the fish captured in 2013 ranged from 0.5 to over 8 years old.
Mercury concentrations in the fish tissue ranged from 19.3 to 100 ng/g ww, and 78.1 to 533 ng/g
dw (Table 5.7-4). There is a weak correlation between fish size and mercury concentrations
(Figure 5.7-7). As anticipated, a majority, if not all, of this mercury is MeHg.
5.7.5. Burbot
A total of eight burbot were collected from the mainstem of the Upper Susitna River in the
inundation zone, two were captured in 2012, and six in 2013 (Figure 4.2-26). The fish ranged
narrowly in size from 390 mm to 467 mm, and in weight from 312 g to 553 g (Table 5.7-5).
Two otoliths were successfully extracted from the burbot, and in both cases the fish was found to
be approximately 5 years of age. For the fish collected in 2013, burbot livers were also analyzed
for mercury and other metals.
Mercury concentrations in the fish tissue ranged from 39.8 to 113 ng/g ww, and 200 to 547 ng/g
dw (Table 5.7-5). Mercury concentrations in liver tissue were generally lower, ranging from
14.7 to 44.2 ng/g ww, and 31.6 to 241 ng/g dw (Table 5.7-6). There is a weak correlation
between fish size and mercury concentrations (Figure 5.7-8), which may be due to the narrow
range of sizes sampled. As anticipated, a majority, if not all, of this mercury is MeHg.
5.7.6. Slimy Sculpin
A total of seven slimy sculpin were collected from the mainstem of the Upper Susitna River in
the inundation zone in 2013 (Figure 4.2-26). Unlike the other species studied here, the analytical
results of the slimy sculpin were evaluated for whole fish. The fish ranged narrowly in size from
74 mm to 100 mm, and in weight from 3.6 g to 6.6 g (Table 5.7-7). Otoliths were not sampled
due to the small size of the fish. Mercury concentrations in the fish tissue ranged from 23.3 to
85.1 ng/g ww, and 104 to 387 ng/g dw (Table 5.7-7). There appears to be a poor correlation
between slimy sculpin size and mercury concentration (Figure 5.7-9), however, this may be
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because the total mercury concentrations in the fish were nearly the same for all sizes. As
anticipated, a majority, if not all, of this mercury is MeHg.
5.7.7. Whitefish sp.
A total of 13 whitefish were collected from the mainstem of the Upper Susitna River in the
inundation zone in 2013 (Figure 4.2-26).
Humpback whitefish were found to be rare in the inundation zone. Only a single fish was
positively identified; however, two other unidentified whitefish were also captured. The
remaining 10 whitefish captured appeared to be round whitefish. The fish were captured
throughout the proposed inundation zone. Otoliths were extracted from three of the fish for
analyses.
Three of the whitefish captured appeared to be juveniles, but were analyzed since they had been
accidentally killed in rotary screw traps. Including the juveniles, the fish ranged in size from 140
to 450 mm, and in weight from 57.1 to 470 g (Table 5.7-8).
Previous studies of the round whitefish in the Susitna Middle River (APA 1984b) found there to
be a good relationship between fork length and age (Figure 5.7-10). Based on the data collected
in this study the fish captured for this study ranged from 1 to 20 years. It should be noted that
the Middle River is more productive than the Upper River, meaning the same size fish may be
younger in the Middle River than the Upper River because there is more food available.
Therefore using age data from the Middle River could underestimate age for Upper River fish.
Mercury concentrations in the fish tissue ranged from 5.68 to 102 ng/g ww, and 26.9 to 379 ng/g
dw (Table 5.7-8). The concentration of mercury appeared to be reasonably correlated with fish
size (Figure 5.7-11). As anticipated, a majority, if not all, of this mercury is MeHg.
5.8. Modeling
5.8.1. Harris and Hutchison
Results of the model simulation to predict peak increase factors (relative increases) for the
proposed the project are shown on Table 5.8-1. These predicted relative increases are low (2.77
for non-piscivorous fish and to 4.24 for piscivorous fish) compared to what has been observed in
Canadian reservoirs (Schetagne et al. 2003; Bodaly et al. 2007). The low predicted peak values
were due to both low relative increases and relatively low baseline concentrations of mercury at
the site.
5.8.2. Phosphorous Release Model
The phosphorous release model cannot be completed at this time because it requires inputs from
the reservoir model (Study 5.6).
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5.8.3. Pathways Assessment
The pathways assessment cannot be fully completed because it requires inputs from the reservoir
model (Study 5.6), particularly predictions of mercury and phosphorous concentrations in water
and sediment post impoundment. However, an assessment of the existing mercury pathways
can be presented here.
The primary source of mercury to the reservoir will be atmospheric deposition, and degradation
of mercury inside the inundation zone that is stored in vegetation, peat, and shallow soil s. The
existing relationship between mercury in the environment in the inundation area can be
summarized as follows:
Atmospheric deposition (336 ng/m2/yr.) (from WACAP 2008).
Vegetation uptake (9.16 ng/g dw)
Concentration of vegetation in organic soils (58.25 ng/g dw)
Transport in surface water (5 ng/L)
Concentration in sediment/porewater (9 ng/g dw)
Concentration in bacteria
Concentration in invertebrates
Concentration in non-piscivorous fish (205 ng/g dw)
Concentration in piscivorous fish (1,088 ng/g dw) and mammals (7,000 ng/g dw)
Transferability of mercury between media (e.g., sediment to pore water) is enhanced by several
environmental factors that increase methylation from sediments or in pore water or that
sequesters mercury into sediments (Figure 5.8-1). The Technical Memorandum Mercury
Pathways Analysis describes in detail approach and methods for conducting this pathways
assessment for mercury (Appendix A). An increase in the methylation rate might be due to the
following conditions:
Presence of aquatic vegetation;
A reducing environment (redox potential) or low oxygen concentrations;
Increased nutrients;
Increased temperature;
Increased microbial respiration;
Presence of dissolved organic carbon;
Neutral to low pH.
A decrease in the methylation rate in sediments or pore water (Figure 5.8-1) could be a result of:
Higher dissolved oxygen concentrations;
Presence of sulfides or acid-volatile sulfides;
Presence of selenium in sediments.
Mercury sequestered in sediments, entrained in pore water, or in the water column can be bound
to organic matter or exist in a methylated form. The transfer process from sediment to
bioaccumulation in the food chain is shown on Figure 5.8-2. Elemental mercury or mercury
adsorbed to organic particles can be physically transferred in a riverine setting from sediment to
pore water to surface water by moving water that re-suspends adsorbed mercury on organic
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particles from the sediment. The increase or decrease in MeHg in any of these compartments are
dependent on factors that either enhance or diminish the methylation process.
The pathways assessment is completed in two steps: 1) determination of potential toxic
concentrations in sediment or pore water and if exposure of aquatic life results in chronic or
acute effects, and 2) examination of water quality factors that could enhance methylation of
mercury and aquatic life are exposed to lethal concentrations.
The presence of mercury under existing conditions was evaluated for potential toxicity to aquatic
life using available criteria: 1) National Oceanic and Atmospheric Administration (NOAA)
Screening Quick Reference Tables (SQuiRTs) for sediments, and 2) Alaska Water Quality
Standards (AWQS) for pore water and surface water. Sediment was collected from three points
at each sample site with analysis for mercury described separately (Figure 5.8-3). The SQuiRT
threshold for mercury in sediment is 174 ng/g dw with all observations for mercury in sediment
falling well below this concentration at all sites.
Porewater was collected and analyzed for mercury at the same sites as the sediment samples.
The results were compared to AWQS, and are well below the environmental thresholds for
protection of aquatic life. The controlling state standard for mercury in surface water is 0.050
micrograms per liter (µg/L) or 50 ng/L and is intended to protect aquatic organisms from
exposure as well as protection of potable water sources. Dissolved mercury results for porewater
were less than one-quarter of the water quality standard for protection of the designated
beneficial uses. Most of the porewater concentrations from tributary sediments were at or near
detection limits; detection limits are shown on Figure 5.8-4.
Some factors diminish the toxic effects of MeHg. For example, the selenium in sediments will
typically bind with mercury forming mercury selenide, reducing the formation of MeHg.
Selenium will also reduce the toxicity of mercury inside an organism. Once uptake of Hg has
occurred in aquatic organisms, the body burden of this metal does not determine toxicity, rather,
a combination of the presence of selenium and mercury better represent potential toxic effects.
Peterson et al. (2009) indicated that the concentration of mercury in tissues is not the critical
indicator for toxicity. Instead toxicity is determined by the ratio of moles of mercury to the
moles of selenium in the organism. As the molar ratio for selenium: mercury approaches or
exceeds 1:1, mercury toxicity decreases.
The upper river sites had low concentrations of selenium in sediment (Figure 5.8-5) and non-
detectable concentrations at several sample points (e.g., Kosina, Jay, Goose, and Oshetna
Creeks). However, the concentration of selenium in sediments was typically two orders of
magnitude (100 times) larger than mercury sediment concentrations from the same sample
points, suggesting that the toxicity of mercury in the ecosystem is low.
Additional factors and fate processes that influence increases in mercury methylation rates
include: pH, dissolved oxygen concentration, temperature, and redox potential. These factors are
further examined for compliance with current water quality standards in Figure 5.8-6 through
Figure 5.8-9. Field observations for these factors were within water quality standards as reported
in select graphs (Figure 5.8-6 through Figure 5.8-8); the one exception was one dissolved oxygen
concentration among the sample points collected from Oshetna River (Figure 5.8-8). All other
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results were within a range that are protective of beneficial uses, including aquatic life, and were
not considered influential for increasing methylation of mercury. Individual data points for
factors and fate processes, as reported in Figure 5.8-6 through Figure 5.8-9, that influence
mercury methylation rates are found in Table 5.8-2.
Increased nutrients can contribute to increased mercury methylation rates. A surrogate indicator,
percent TOC, was examined for nutrient content in sediment samples. TOC at all sample points
represented in sediments was less than one percent, indicating a dominance of inorganic material
present at all locations (Table 5.5-1).
6. DISCUSSION
6.1. Summary of Available Information
The available information on the concentrations of mercury in various media in Alaska is
extensive and fairly well documented in the ISR Study Plan Section 5.7.
The following is a discussion of information on the general characteristics of mercury in the
environment, the accumulation of mercury in biological organisms, and the potential impacts to
ecological resources. It is included here to allow for a better understanding of the analytical data
generated, and the Harris and Hutchison modeling and pathways assessment.
6.1.1. Mercury Sources
In nature, the mineral cinnabar (mercury sulfide or HgS) occurs in concentrated deposits and has
been used as the primary source of commercially mined mercury. However, mercury is bound
very tightly to sulfur in cinnabar, and typically weathers slowly (USGS 2013). In areas that lack
the necessary mercury mineralization, the mercury concentration in parent geologic materials is
typically very low, and cannot explain the mercury concentrations observed in sediment in
aquatic ecosystems (Fitzgerald et al. 1998; Swain et al. 1992; Wiener et al. 2006). This is
because numerous studies have shown the primary source of mercury to aquatic ecosystems is
atmospheric. For example, the 1992-1996 Florida Atmospheric Mercury Study (FAMS)
demonstrated that atmospheric deposition accounts for more than 95% of the mercury in the
Everglades each year (Guentzel et al. 1994). Because the primary source of mercury is
atmospheric, mercury can create problems in aquatic ecosystem even when a primary source of
mercury is distant.
This would appear to be true for the proposed reservoir; given the rock types and mineralization
in the proposed inundation zone do not appear to contain significant sources of mercury,
however, this does not mean that mercury concentrations in the resulting reservoir will not be
elevated over background.
The primary sources of mercury to the atmosphere are 1) Volcanic eruptions 2) Forest fires, and
3) coal burning. Volcanic eruptions cycle mercury into the atmosphere from deep in the Earth.
Forest fires liberate mercury that has previously been deposited on the land, and has been
absorbed by plant life. Coal is fossilized plant life, which contains the trace amounts of mercury
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that was present in the plants when they died and were buried. Burning coal liberates this
mercury into the environment. In 2000 it was estimated that as much as two-thirds of the total
anthropogenic emissions of mercury world-wide was from the combustion of fossil fuels (Pacyna
et al. 2006), mostly coal. It is estimated that over the last 100 years, anthropogenic mercury has
accounted for approximately 70% of the total atmospheric deposition of mercury at the location
of the Upper Freemont Glacier in the western United States, with the remainder coming from
other sources (Schuster et al. 2002).
WACAP (2008) observed an annual atmospheric influx of mercury of 336 ng/m2/yr. at Wonder
Lake. It is expected that a similar influx would occur at Watana. Given the reservoir will be
23,500 acres (95.1 million square meters), annual atmospheric contributions to the reservoir
would be approximately 31.95 grams per year.
This influx of mercury has been incorporated into the vegetation in the inundation zone. The
estimated vegetative mass per square meter at the site is 4 kg ww (derived from Mead 1998).
Assuming an average concentration in the vegetation of 2.8 ng/g of mercury ww, the total
mercury stored in the vegetation of the inundation zone is estimated at 11,200 ng/m2. Viewed
from another perspective, the vegetation has captured and stored approximately 33 years of
atmospherically deposited mercury.
An average of 60 ng/g dw of mercury was present in the organic soils (peat) within the
inundation zone. The average thickness of this layer was found to be 10 cm. Peat has a dry
density of 4 g/cm3. Therefore each square meter of soil would therefore contain 400,000 g of
organic soils (dw). This equals 24,000,000 ng/m2. Viewed from another perspective, the
organic soils are storing approximately 2,143 times the amount stored in the vegetation.
This relationship between atmospheric mercury deposition, vegetation, and peat is logically
consistent, in that vegetation takes many years (or decades) to grow, and peat takes hundreds, if
not thousands of years, to form from the vegetation.
These calculations also clearly illustrate why mercury concentrations typically spike after
inundation of a reservoir. As the vegetation and especially the fine organic soils are broken down
by bacteria, the accumulated atmospheric mercury is released to the reservoir, and is available to
aquatic organisms. This influx of mercury can be many times what may occur via natural
atmospheric deposition. It should be noted that not all the vegetation and organic soils are
susceptible to biological break down. Woody debris degrades very slowly in cold water, and
organic material at the bottom of the reservoir tends to get sequestered in fine sediment, and
degrades slowly, if all. Most of the biological breakdown of plants and organic soils occurs in
fine organic material on the margins of the reservoir.
Previous studies have found that increases in MeHg concentrations in a reservoir after filling are
not related to atmospheric deposition. Rudd (1995) has shown that only 0.3% to 3% of the
mercury in a newly formed reservoir is derived from precipitation, while the remainder is from
inundated fine organic soil particles. Studies have found that the primary source of mercury to a
new reservoir is inundated soils (Meister et al. 1979), especially the upper organic soil horizon
(Bodaly et al. 1984).
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6.1.2. Mercury Bioaccumulation
As a volatile liquid, in some ways, mercury behaves much like water does as part of the
hydrologic cycle (Figure 5.8-2). Under the right conditions, it evaporates from the Earth’s
surface, can travel as a vapor, and can be precipitated at remote locations, changing its chemical
form as it moves. Ultimately, mercury is sequestered in sediments, absorbed by fish, plants, and
wildlife, or evaporated back to the atmosphere by volatilization.
Mercury exposure to the ecosystem via water, sediment or soil is typically low, and
concentrations of mercury in these media are often undetectable. The various forms of mercury
can be converted from one to the next; most important is the conversion to MeHg, which is more
toxic and hazardous because it bioaccumulates in species. In water bodies, bacteria generate
MeHg as part of their metabolic processes. Bacteria pass the MeHg up the food chain, where it
becomes slowly concentrated in higher organisms (Figure 5.8-2). The rate of bioaccumulation is
often specific to each organism. Size, age, diet, and species greatly influence the rate of mercury
bioaccumulation. In general, the longer an organism lives, the higher trophic level it occupies,
the more mercury it will tend to bioaccumulate. For example, Arctic grayling may live shorter
lives, and generally subsist on insects and fish eggs. Lake trout typically live longer, and feed on
insects, but also on small crustaceans, and fish. Because of this, lake trout typically
bioaccumulate higher concentrations of mercury in similar ecosystems than Arctic grayling.
Physical factors can also greatly influence the formation and uptake of MeHg. Ocean, lake, and
stream habitats each have different physical properties that affect the input and retention of
mercury in the system. In general lakes and ponds retain mercury longer than streams and rivers.
Photodegradation is a primary demethylation mechanism for MeHg, and water bodies with high
levels of circulation offer greater opportunities for this mechanism to occur (Seller et al. 1996).
Water quality parameters also affect MeHg uptake rates for aqueous organisms. Wiener et al.
2006 concluded that high dissolved sulfate, low selenium, low lake water pH, and high organic
carbon favored MeHg bioaccumulation. Lake temperature has also been implicated in
methylation (Schindler et al. 1995; Lambertson and Nilsson 2006; Power et al. 2002).
Krabbenhoft et al. (1999) showed that the density of nearby wetlands was the most important
factor increasing methylation rates. The location of sampling in relation to point sources of
mercury contamination also clearly has an effect on mercury levels in fish.
In general, total mercury in fish consists of > 85% MeHg, but in some species (such as pike)
MeHg has been found to be is nearly 100% of the total mercury (Jewett et al. 2003). This was
consistent with the results of this study. MeHg is most likely to be present in fish because it
bioaccumulates in tissue, whereas elemental mercury can pass through organisms relatively
quickly.
Because mercury, unlike many other contaminants, concentrates in the muscle tissue of the
organism, it cannot be filleted or cooked out of consumable game fish.
Looking at the results of this study, the non-piscivorous fish (Arctic graying, whitefish, and
longnose suckers) seemed to have concentrations of total mercury of around 40 to 80 ng/g ww.
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Piscivorous species (lake trout) had a mean total mercury concentration of 247 ng/g ww, or
approximately 4 times the concentration of the non-piscivorous species. This suggests a fairly
typical mercury relationship between trophic levels (Tremblay 1999).
Slimy sculpin were analyzed as whole body. Adjusting for this factor and slimy sculpin would
have similar total mercury concentrations of muscle tissue to other non-piscivorous species.
The burbot results were anomalous. While burbot are typically a piscivorous species, they
typically don’t begin feeding on other fish until their 5th to 6th year in the aquatic environment.
All of the burbot captured during this study were below this threshold age, and are therefore
considered non-piscivorous for the purposes of this study. Their mercury concentrations were
largely consistent with what was observed for other non-piscivorous fish studied at the
impoundment area.
6.1.3. Mercury Behavior in Reservoirs
Many studies have documented increased mercury levels in fish following the flooding of
terrestrial areas to create hydroelectric reservoirs (Bodaly et al. 1984; Bodaly et al 1997; Bodaly
et al 2004; Bodaly et al. 2007; Rylander et al. 2006; Lockhart et al 2005; Johnston et al. 1991;
Kelly et al. 1997; Morrison 1991). These problems have been sometimes acute in hydropower
projects from northern climates including Canada and Finland (Rosenberg et al. 1997). When
boreal forests are flooded, substantial quantities of organic carbon and mercury stored in
vegetation biomass and soils become inputs to the newly formed reservoir (Bodaly et al. 1984;
Grigal 2003; Kelly et al. 1997). This flooding accelerates microbial decomposition, causing
accelerated microbial methylation of mercury. Part of the MeHg produced is released into the
water column where it may be transferred to fish via zooplankton. Insect larvae feeding in the
top centimeters of flooded soils can assimilate the MeHg available and transfer it to fish (Figure
5.8-2). The production and transfer of MeHg is governed by the amount and type of flooded
organic matter and by biological and physical factors such as bacterial activity, water
temperature, oxygen content of the water, etc. of the newly formed reservoir.
Because the fine organic material that is being inundated is a finite source, and is slowly
consumed by the bacteria, or sequestered under accumulating sediment, MeHg concentrations in
the reservoir generally return to background concentrations. Studies have shown this increase
lasts between 10 and 35 years (Hydro-Quebec 2003; Bodaly et al. 2007).
The magnitude and timing of the change in MeHg concentrations can vary significantly by
trophic levels in the same reservoir. Peak MeHg concentrations first occur in the water column,
in lower trophic level organisms and young fish, and later in top predators, such as lake trout
(Bodaly et al. 2007; Schetagne et al. 2003). These trends are consistent with a pulse in MeHg
production that peaks within a few years after inundation, and then takes time to move through
the food web to top predators.
The peak MeHg concentrations in some higher tropic level fish (lake trout) species are typically
4 to 7 times greater than background levels (Bodaly et al. 2007; Schetagne et al. 2003). Lower
trophic level fish species such as Arctic grayling tend to have lower concentrations and slightly
lower relative increases (2 to 5 times above baseline). Increased mercury concentrations have
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also been noted at other trophic levels within aquatic food chains of reservoirs, such as aquatic
invertebrates (Hall et al. 1998). However, it is not uncommon for concentrations at lower trophic
levels to be too low to measure.
Fish mercury concentrations downstream of some reservoirs can increase as well (Schetagne et
al. 2003; Anderson 2011). The distance downstream of reservoirs where increased fish MeHg
levels occur depends on system-specific features. A study was performed to identify how
mercury is transported downstream from reservoirs and to assess the amount of mercury being
exported (Schetagne et al 2000). The results indicated that the dissolved MeHg and the
suspended particulate matter are the major components by which mercury is transferred
downstream of reservoirs, accounting for 64 and 33%, respectively, of the total amounts
exported. Plant debris, benthic invertebrates, fish, phytoplankton, and zooplankton were found to
be much less important pathways for mercury export because of their very low biomass per
water volume coming out of the generating station, as opposed to the high biomass of suspended
particulate matter.
In the case of the Susitna-Watana Dam downstream export appears unlikely. The river
downstream of the dam will be relatively shallow and highly oxygenated. MeHg is not stable in
water exposed to air and sunlight, and quickly breaks down. Lehnherr and St. Louis (2009)
found that, depending on the quantity and type of radiation, up to 75% of MeHg in lakes can be
demethylated by sunlight. UV radiation accounts for 58% and 79% of the photodemethylation
activity in a clear and colored lake, respectively.
Chetelat et al. (2008) studied MeHg transfer to fish in high arctic lakes and found that mercury is
bound to organic material rather than inorganic particles, and low organic carbon in water and
sediment reduce mercury retention in lakes. The capacity of the sediment bacterial community
to generate MeHg may be strongly limited by poor environmental conditions for methylation
rather than the availability of inorganic mercury.
6.1.4. Potential Ecological Impacts
In fish, mercury accumulation is typically age-dependent. This was certainly found to be the
case in this study (Figures 5.7-2, 5.7-5, 5.7-7, and 5.7-8). However the correlation appears to be
weak with whitefish, and nonexistent with slimy sculpin (Figures 5.7-9 and 5.7-11). This
difference is likely diet related. As fish get older their diet may consist of larger prey, at a
steadily higher trophic level. However, round white fish feed mostly on invertebrates, such as
crustaceans, insect larvae, and do not typically feed at much higher trophic levels as they get
older. Slimy sculpin are very small, and have limited choices of prey as they age.
WACAP (2008) found that the increase in mercury concentrations with age generally diminished
after 15 years. It has been theorized that after 15 years the highest trophic level of feeding for
each species has been reached (Kidd et al. 1995; Evans et al. 2005), or that some sort of
metabolic balance is achieved (Trudel and Rasmussen 1997). A third possible explanation is that
mercury might increase steadily, until it eventually reaches toxic levels (WACAP 2008). As a
result, only fish with fairly low starting concentrations of mercury live past 15 years. Because
the source of mercury is atmospheric, the rate of mercury bioaccumulation in an ecosystem is
typically not source dependent, that is to say the rate of mercury bioaccumulation is dependent
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on site specific conditions for the formation of MeHg. It has been documented extensively that
areas can have concentrated mercury sources, but low methylation rates, and hence low
concentrations of mercury in fish tissue (Bloom 1992). WACAP (2008) found that sites with
elevated mercury flux in snow and sediment were found to have lower concentrations of mercury
in fish, while areas with low mercury deposition were found to nonetheless have high
concentrations of mercury in fish. On this basis, it appears that even though atmospheric
deposition is a primary source of mercury to most ecosystems, the linkage between atmospheric
deposition rates and fish concentrations is weak. These results indicate that we should not expect
a direct relationship between mercury concentrations in soil, vegetation, precipitation, and fish at
the project site. Indeed, the WACAP study of several Alaska National parks found there to be
none.
6.2. Vegetation
The vegetation types at the site do not appear to be variable within the inundation zone, with
only three to four species representing the majority of the vegetation mass. However, there was
a considerable mass of organic material (moss and peat) at almost all the sample locations.
Friedli et al. (2007) found there to be a significant variation in mercury concentrations between
plant species, with moss, lichen, and leaf litter typically showing the highest concentrations of
mercury (Table 6.1-1). These concentrations are consistent with concentrations observed in the
soils at the site, as opposed to the vegetative matter. Table 5.1-8 presents the results for the
lichen collected as part of the WACAP study in Alaska, and shows similar results.
There are no regulatory standards for mercury in vegetation; however, the concentrations are
typically very low.
6.3. Soil
Where soils have developed on uniform parent material vegetation, cover type and cover age are
important variables affecting concentration of mercury in soils (Grigal et al. 1994). This is
certainly true in an upland boreal forest in the Prince Albert National Park, Saskatchewan,
Canada (Friedli et al. 2007). They found that 93 to 97 percent of the mercury resided in the
organic soil (peat and forest litter) above the mineral layer. They also found that periodic forest
fires can “reset” the mercury concentration to a lower level, and that mercury concentrations
increase slowly in the soil over time (Table 6.1-1).
Soil concentrations of mercury can be compared to the NOAA SQuiRTs. These are thresholds
used as screening values for evaluation of toxics and potential effect to aquatic life in several
media. It is suggested that mercury concentrations should be <100 ng/g dw in soil to protect
invertebrates, and < 300 ng/g dw to protect plants. The highest concentration of mercury noted in
the soil was 119 ng/g dw at SITE-3 N2, but most samples were well below this concentration
(Table 5.3-1).
MeHg concentrations need to be below 1.58 ng/g dw to protect the reference species of voles
used for establishing the cleanup standard. While most of the samples had MeHg concentrations
below this level, a few samples significantly exceeded this concentration (Table 5.3-1).
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The SQuiRT table indicates that the mean background concentration of mercury in soil
nationwide is 58 ng/g dw. This is close to the mean for all the soils samples collected in the
inundation zone of 61 ng/g dw. This suggests that the soils present in the inundation zone show
no particular evidence of mercury accumulation above nominal background levels.
In July 2012 ADEC set the following cleanup standards for mercury in soil:
• MeHg in soil of 0.012 mg/kg (12 ng/g dw)
• Total Mercury 1.4 mg/kg (1,400 ng/g dw)
None of the soil samples were found to exceed these concentrations. Both of these cleanup
levels assume that migration to groundwater (and surrounding water bodies) is the primary
exposure pathway.
6.4. Water
While mercury samples were collected during studies conducted in the 1980s, it appears that the
analytical methods utilized at the time were not sensitive enough to detect mercury
concentrations in the water. Their detection range was <0.1 µg/L (<100 ng/L), compared to
current detection limits of approximately 0.5 ng/L. Most detections of mercury reported in the
1980s were at or very near the detection limit for the analytical method (Tables 5.1-1 to 5.1-3).
Such detections are often suspect, given they are close to the theoretical maximum sensitivity of
the equipment.
Modern analyses by the USGS (Table 5.1-1 to 5.1-3) and in this study (Tables 5.4-1 and 5.4-2)
indicate that total mercury concentrations in the water range from <0.5 to 68 ng/L, and is largely
undetectable as dissolved mercury, suggesting that the majority of the mercury detected is
associated with suspended sediment. As previously stated, mercury sorbs onto fine carbon, and
that may be the reason for this result.
Surface water concentrations of mercury can be compared to the NOAA SQuiRT tables. NOAA
recommends screening levels of 1,400 ng/L for total mercury (acute), and 770 ng/L for total
mercury (chronic). AWQS (18 AAC 75.345) has set a cleanup level for surface and groundwater
of 2,000 ng/L. Total mercury concentrations in the Susitna River, as expected, are well below
these concentrations (Tables 5.4-1 and 5.4-2).
6.5. Sediment and Sediment Porewater
The methylation process is largely mediated by anaerobic bacteria in aquatic bed sediment
(Gilmour et al. 2011; Fleming et al. 2006). Once formed, MeHg can enter the benthic food web.
The purpose of the sediment and porewater sampling was to document the primary production of
MeHg at the base of the food web.
Total mercury concentrations ranged more than an order of magnitude between sample locations.
Concentrations of mercury in porewater and sediment from this study (1.00 to 17.4 ng/g dw in
sediment and <0.5 to 12.5 ng/L in porewater) is on the low end of what has been observed in
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other freshwater streams (1.9 to 4,517 ng/g dw) reported in a survey of 106 streams throughout
the United States (Marvin-Depasquale et al. 2009).
Concentrations of mercury in sediment also appeared to be low (Table 5.1-6) when compared to
concentrations found in other freshwater streams and rivers around Cook Inlet (Frenzel 2000).
Table 5.1-7 shows the partitioning of mercury in select samples from the Frenzel (2000) study.
Concentrations of mercury at the site were low compared to most of the other sites, but in
sediment, fish, and water. Interestingly, the one site sampled by Frenzel (2000) with similar
mercury concentrations was Costello Creek, which is located north of the project site near
Cantwell (Figure 5.1-2).
Sediment grain size and TOC typically exert a dominant influence on sediment mercury
concentrations at most sites; however, in this study there appeared to be little correlation between
TOC and mercury concentrations. It is likely the cause of the breakdown in this relationship is
the overall low concentrations of TOC observed in the sediments (Table 5.5-1). Total mercury
concentrations did appear to be loosely related to the sediment size, with finer grained sediments
often producing higher concentrations of mercury, however this was not always the case.
Overall the data suggests that there is a low primary productivity for MeHg in upper Susitna
within the inundation zone.
These sediment concentrations can be compared to NOAA Squirt guidelines (Table 6.5-1). As
with the soil and water results, the concentrations of mercury in sediment at the site were well
below screening levels.
6.6. Piscivorous Birds and Mammals
Efforts to collect bird specimens have so far been unsuccessful. This potential problem was
identified in the Study Plan and discussed with the TWG, in that it is difficult to collect non-
lethal samples for animals with very low population densities in rugged terrain. Lack of access
to CIRWG lands and a Bald Eagle collection permit further limited the potential for sample
collection.
For the two samples of otter hair analyzed, one of the samples exhibited a very low concentration
of mercury (417 ng/g ww; Table 5.6-1). It is possible that the individual hairs found in the trap
may belong to a juvenile, which would explain their relatively low concentration of mercury
compared to the adult sample. However, the mercury concentration in the adult fur sample also
seems relatively low (1,610 ng/g ww) compared typical concentrations found in other studies
(Yates et al. 2005), and these concentration are consistent with relatively low mercury
concentrations found in fish, sediment, and surface water. It is also consistent with the relatively
low concentrations of mercury found in the mink pelts.
Other studies have documented mercury levels in river otter fur ranging from 2,800 to 73,700
ng/g ww in Maine, with a mean of 20,700 ng/g ww (Yates et al. 2005). This compares to 417 to
1,610 ng/g ww found during this project. Concentrations of total mercury in fur samples from
Nova Scotia averaged 25,000 ng/g dw, ranging from 1,400 to 137,000 ng/g dw (Spencer et al,
2011). This compares to 6,330 ng/g dw found during this project. Overall the concentrations
found appear to be relatively low compared to concentrations seen elsewhere.
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Studies have documented mercury levels in mink ranging from 1,780 to 68,500 ng/g ww in
Maine, with a mean of 17,500 ng/g ww (Yates et al. 2005). This compares to 2,170 to 2,970
ng/g ww found in the mink samples collected as part of this study. Again, these results are
consistent with the relatively low concentrations documented in the sediment, water, and fish
tissues at the site.
6.7. Fish Tissue
The data indicates that mercury concentrations in trout continue to increase as the trout age
(Figure 6.7-1). This is consistent with the fact that as trout age they get larger and feed at
progressively higher trophic levels. This relationship was not observed as much with the non-
piscivorous fish. This is especially noticeable for the Arctic grayling and whitefish (sp.) (Figure
6.7-1). Arctic grayling showed a correlation between age and mercury concentrations, but the
results were more scattered, and had more exceptions. Whitefish showed only a moderate
increase in mercury concentrations with age.
The burbot showed somewhat anomalous results, with relatively low concentrations for a
piscivorous species (Figure 5.7-8). The feeding habits of burbot are complex, and may vary
seasonally, and with life stage (Dixon and Vokoun, 2009). It is possible that burbot captured
were non-piscivorous, and their close range in size suggests that all the fish captured are at the
same life stage.
In general, mercury concentrations reported in fish captured inside the inundation zone were
consistent with results for the same species captured elsewhere in Alaska. Comparing the results
from this study to ADEC statewide results (ADEC 2012), the results for the Upper Susitna
seemed to be on the low end of the average observed for the state (Table 5.1-4). Overall the
mean and median were lower for all species of fish, except for longnose suckers. However,
these results represent an average for ADEC sampling across the state, and ADEC tends to focus
on sampling watersheds where a problem may exist. In addition, the ADEC analytical method
does not follow standard EPA procedures, and results from these analyses should be considered
estimates.
Table 5.1-5 presents the samples from the previous ADEC study, but only for samples from the
Susitna River Drainage (Figure 5.1-1). Again, the results from this study of the Upper Susitna
River appear to be slightly lower than concentrations found elsewhere in the drainage.
Comparing slimy sculpin concentrations to those found in various freshwater streams around
Cook Inlet (Frenzel (2000), it appears the concentrations are consistent with what has been
recorded elsewhere (Table 5.1-6, Figure 5.1-2).
The WACAP study looked at concentrations of mercury in fish in relatively pristine national
parks in Alaska. Concentrations of mercury in lake trout and burbot caught in these lakes were
very similar to the concentrations reported as part of this project (Table 5.1-9).
Looking through the literature, Arctic grayling appear to be the fish most commonly analyzed for
mercury in Alaska. The results from multiple studies have been compared on Figure 6.7-2. The
results are graphed on the basis of mean weight and mean mercury concentration per capture
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location, to better adjust for the increase in mercury concentrations in larger fish. In summary,
the results from this study appear to reside on the lower end of mercury previously observed for
Arctic grayling in Alaska.
6.8. Modeling
After construction of a reservoir, mercury concentrations in fish typically increase several times
above background levels. These fish tissue concentrations typically peak 5-15 years after
flooding, and may take 2-3 decades to diminish back to background concentrations. This
phenomenon is well understood and studied, and the cause of this pulse of mercury though the
ecosystem is the decay of naturally occurring fine organic materiel within the inundation zone.
The volume of organic soils, biological productivity, rate of breakdown of this materiel, reservoir
flow through, and other factors determine the rate and amount of mercury that will accumulate in
fish species. The exhaustion of the fine organic materials in the reservoir is typically what
causes the mercury concentrations in fish to slowly return to background over decades.
Several models have been created to predict mercury concentrations in reservoirs post
impoundment. These models have been tested against multiple reservoirs, as well as the
Experimental Lakes Area (ELA)in Ontario, Canada (Bodaly et al. 2005). Two of these models
have been considered as part of this study.
Schetagne et al. (2003) found a strong correlation between the ratio of flooded area, the mean
annual flow through of the reservoir, and maximum mercury concentrations in fish tissue. This
approach was further refined by Harris and Hutchinson (2008) to provide a predictive tool for
MeHg concentrations in fish. Regression calculations using historical data from multiple
reservoirs have determined the coefficients that control these equations. The drawback to these
models is that they only predict peak MeHg concentrations, not when these concentrations will
occur or subside. The advantage of this type of model is that it is simple, and requires relatively
few input parameters. Because the input data is relatively simple to determine and calculate, this
type of model is often used to screen potential impacts. This screening function is not meant to
imply that the model is any less accurate than alternatives, in fact, given the model relies on
easily and accurately determined parameters, it may be more accurate than more complex
models.
The phosphorous release model is a more complex method of estimating MeHg impacts. It was
pioneered by Messier et al. (1985) based on the work of the whole-ecosystem reservoir
experiments at the ELA (Bodaly et al. 2005), and confirmed by decades-long studies of
reservoirs by Hydro-Quebec (2003). The model is more complex than the Harris and Hutchison
model, however, the purpose of the additional complexity is to allow for a prediction of when the
peak mercury concentration would likely occur, and how long elevated mercury concentrations
in fish would be likely to persist. The model pays special attention to flood zone characteristics,
because decomposition after flooding is a key driver for increases in MeHg levels in new
reservoirs.
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6.8.1. Harris and Hutchison
The Harris and Hutchison model results are presented in Section 5.8.2 of this study report, and
suggest that that inundation of the Susitna-Watana reservoir is unlikely to increase
concentrations of mercury in fish to concentrations that may adverse impact human health and
the environment (Table 5.8-1). The maximum predicted mean concentration for piscivorous fish
species was 1,047 ng/g ww, while for non-piscivorous species it was 212 ng/g ww. It should be
noted that this maximum concentration may only be present in the reservoir for a brief period,
and would decline shortly thereafter.
It is difficult to precisely determine the impact of mercury in fish tissue on various species of
mammal, birds, as well as humans. This is because the sensitivity of these receptors varies with
species, as well as feeding habits and frequency.
For human health risk, muscle mercury concentrations can be compared to fish consumption
guidelines recommended by the Alaska Department of Health and Social Services (AK-DHSS)
to protect women who are or can become pregnant, nursing mothers, and young children
(Verbrugge 2007). These consumption guidelines suggest the following:
0 to 150 ng/g ww – unlimited fish consumption.
150 to 320 ng/g ww – limit to 4 meals per week.
320 to 400 ng/g ww – limit to 3 meals per week.
400 to 640 ng/g ww – limit to 2 meals per week.
640 to 1,230 ng/g ww – limit to 1 meal per week.
>1,230 ng/g ww fish should not be routinely consumed.
These numbers are considered to be fairly conservative, given they were calculated based on the
most vulnerable parts of our population. Based on the Harris and Hutchison model, it would
appear that mercury concentrations in fish at the proposed reservoir may cause a need to place
certain catch limits and consumption guidelines during the period of time when mercury
concentrations peak in the fish, however, these restrictions would not appear to be significant,
and would likely last only a brief period of time.
While muscle tissue results best represents potential exposure to humans, whole body results
more accurately estimate ecosystem exposures. These muscle tissue results can be converted to
whole body concentrations in order to assess the toxicological risks of mercury to wildlife
(Peterson et al. 2005). The whole body fish concentrations for piscivorous fish (lake trout)
would be 281 ng/g ww, and 67 ng/g ww for non-piscivorous fish.
To assess potential toxicological effects of mercury to fish, the estimates of whole-body mercury
can be compared to a no-observed-effects-residue (NOER) of 200 ng/g ww (Beckvar et al. 2005)
and a lowest-observed-effects-residue (LOER) of 300 ng/g ww (Sandheinrich et al. 2011). Fish
with whole body mercury concentrations less than the NOER benchmark are not commonly
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associated with altered behavioral, development, growth, or reproduction. Fish with whole body
mercury concentrations greater than the LOER benchmark have been consistently associated
with sublethal effects, including changes in reproductive health.
Based on these criteria, concentrations of mercury in non-piscivorous fish are unlikely to ever
exceed the NOER, and concentrations in piscivorous fish are unlikely to exceed LOER. Overall
it appears unlikely the concentrations of peak mercury will have significant or noticeable impact
on fish populations.
For piscivorous birds, whole-body mercury concentrations can be compared to toxicological
benchmarks representing risks to sensitive species. A review of field and laboratory studies on
mercury toxicity in common loons found that mercury concentrations greater than 180 ng/g ww
whole body in prey fish were associated with significant reductions in reproductive success
(Depew et al. 2012). The non-piscivorous fish would appear to be well below this standard,
however, the piscivorous fish may exceed this standard. Given that the piscivorous birds would
be unlikely to feed exclusively on one species of fish (lake trout), it appears unlikely that adverse
impacts would occur.
Another method to evaluate these results is to compare them to other reservoirs in Alaska. If
similar concentrations of mercury were present in other Alaska reservoirs without adverse
impacts human health and the ecosystem, it would be unlikely to do so in the case of this project.
Unfortunately mercury accumulation in reservoir fish has not be previously studied in Alaska,
and no baseline data exists for actual (versus predicted) mercury accumulation rates. However,
the same Harrison and Hutchison linear model can be applied to other constructed reservoirs in
Alaska. This comparison can be seen on Table 6.8-1. Significant ecological and human health
impacts from mercury have not been observed in these older reservoirs, and it appears that this
project would have similar impacts.
6.8.2. Phosphorous Release Model
Because of its greater complexity, the phosphorous release model requires more data inputs.
Some of these inputs, such as phosphorous concentrations in the reservoir water after inundation,
will be generated by the EFDC modeling being performed under Study 5.6. Until that modeling
is done, the phosphorus release model cannot be completed.
6.8.3. Pathways Assessment
Several factors can affect the potential for bioavailability of mercury in the aquatic environment.
Factors affecting bioavailability are described in Figure 5.8-1 and the processes of circulation in
the ecosystem (e.g., sediments, surface water, biotic) in Figure 5.8-2. Fate processes and factors
that increase methylation of mercury or decrease the chance for methylation to occur were the
focus for evaluation of existing conditions immediately below and in the proposed reservoir area.
The procedure for evaluating potential pathways where risk for bioavailability of mercury occurs
under existing conditions is the following:
Identify factors and fate processes that increase potential exposure of aquatic life;
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Determine if factors (fate processes) are within water quality standards; and
Interpret potential for mercury transfer between media and aquatic life at risk from
exposure resulting from this transfer.
An evaluation of factors and fate processes with a focus on potential increases of methylation of
mercury are reported in Table 5.8-2. Examination of how each factor contributes to increases in
methylation of mercury and an assessment of data describing existing conditions at each sample
site informed on potential for exposure from this bioavailable form. Low concentrations of
mercury in sediments from the sites and absence of critical factors or fate processes that would
contribute to methylation of mercury are evidence that risk of exposure to aquatic life is low
(Table 5.8-2).
This evaluation will be revised when the EFDC model for the reservoir is complete (Study 5.6).
7. COMPLETING THE STUDY
Significant progress has been made since June 2014 in meeting the objectives of the Mercury
Study. Sample collection efforts have met all the objectives outlined in Section 2 of the ISR. No
additional field work is planned or would appear to be necessary at this time.
The remaining tasks for this study include:
Phosphorous release modeling for evaluating potential mercury concentrations in fish
after reservoir development. Completion of this modeling is dependent on completion of
the EFDC modeling (Study 5.6) for the surface water.
Update of the pathways assessment to include information generated from EFDC
modeling (Study 5.6) for the surface water.
A decision on additional terrestrial biological sampling (mammals and birds) will be
made based on the results of the two previous bullet items. Based on the results of the
Harris and Hutchison modeling, as well as all the currently available information,
additional sampling of terrestrial tissues is unlikely to be necessary, given the
concentrations of mercury in fish are unlikely to exceed levels of concern.
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L.G. Woodruff, W.F. Cannon, and S.J. Balogh. 2006. Mercury in soils, lakes, and fish in
Voyageurs National Park (Minnesota) - Importance of atmospheric deposition and
ecosystem factors. Environmental Science and Technology, v. 40, p. 6261-6268.
Yates, D.E., D.T. Mayack, K. Munney, D.C. Evers, A. Major, K. Tranjit and R.L. Taylor. 2005.
Mercury Levels in Mink (Mustela vison) and River Otter (Lontra canadensis) from
Northeastern North America. Ecotoxicology, 14, 263–274, 2005.
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9. TABLES
Table 4.2-1. Sampling Parameters and Media
Parameter
Media
Vegetation Soil Surface Water Sediment Sediment
Porewater
Piscivorous Birds
and Mammals
Fish Tissue
Filet Liver
TOC X X
Mercury Total Total Total, Dissolved Total Dissolved Total Total Total
Methyl Mercury X X X X X
Sediment Size X
Total Solids X
See ISR Section 5.5 for additional parameters collected for Baseline Monthly and Focus Area Water Quality Sampling
Table 4.2-2. Vegetation and Soil Sample Locations
Sample Site Latitude Longitude Nearest PRM
Site 1 N1 62.8206 -148.1557 200.3
Site 1 N2 62.8207 -148.1560 200.3
Site 1 N3 62.8206 -148.1553 200.3
Site1 N4 62.8207 -148.1562 200.3
Site1 N5 62.8206 -148.1552 200.3
Site 2 N1 62.7976 -148.0707 203.8
Site 2 N2 62.7975 -148.0706 203.8
Site 2 N3 62.7974 -148.0704 203.8
Site 2 N4 62.7976 -148.0708 203.8
Site 2 N5 62.7973 -148.0703 203.8
Site 2 N6 62.7973 -148.0703 203.8
Site 3 N1 62.7895 -148.0556 208.0
Site 3 N2 62.7895 -148.0561 208.0
Site 3 N3 62.7897 -148.0551 208.0
Site 3 N4 62.7896 -148.0563 208.0
Site 3 N5 62.7898 -148.0552 208.0
Site 3 N6 62.7898 -148.0552 208.0
Site 4S alt1 62.7884 -148.0074 206.2
Site 4S alt2 62.7883 -148.0077 206.2
Site 4S alt3 62.7883 -148.0071 206.2
Site 4S alt4 62.7883 -148.0079 206.2
Site 4S alt5 62.7883 -148.0068 206.2
Site 4S alt6 62.7883 -148.0068 206.2
Site 5S 1 62.7842 -147.9521 208.2
Site 5S 2 62.7845 -147.9521 208.2
Site 5S 3 62.7842 -147.9520 208.2
Site 5S 4 62.7846 -147.9524 208.2
Site 5S 5 62.7840 -147.9519 208.2
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Samples collected from August 6 to 7, 2013.
Site 6S-1 62.7790 -147.9189 209.8
Site 6S-2 62.7789 -147.9195 209.8
Site 6S-3 62.7790 -147.9185 209.8
Site 6S-4 62.7788 -147.9198 209.8
Site 6S-5 62.7792 -147.9183 209.8
Site 7 N1 62.7784 -147.8787 211.5
Site 7 N2 62.7784 -147.8787 211.5
Site 7 N3 62.7786 -147.8787 211.5
Site 7 N4 62.7782 -147.8789 211.5
Site 7 N5 62.7787 -147.8789 211.5
Site 7 N6 62.7787 -147.8789 211.5
Site 8 S1 62.7728 -147.8483 212.5
Site 8 S2 62.7729 -147.8481 212.5
Site 8 S3 62.7725 -147.8484 212.5
Site 8 S4 62.7731 -147.8480 212.5
Site 8 S5 62.7724 -147.8486 212.5
Site 9 N1 62.8509 -148.2314 NA
Site 9 N2 62.8508 -148.2316 NA
Site 9 N3 62.8509 -148.2311 NA
Site 9 N4 62.8510 -148.2317 NA
Site 9 N5 62.8507 -148.2310 NA
Site 9 N6 62.8507 -148.2310 NA
Site 10 N1 62.8577 -148.2133 NA
Site 10 N2 62.8574 -148.2131 NA
Site 10 N3 62.8572 -148.2134 NA
Site 10 N4 62.8576 -148.2129 NA
Site 10 N5 62.8571 -148.2136 NA
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Table 4.2-3. Baseline Water Quality Monitoring Sites
PRM Description Latitude Longitude Location Rationale
29.9 Susitna Station 61.544280 -150.515560 Influence of upstream tributary
32.5 Yentna River 61.587604 -150.483017 Major tributary
33.6 Susitna above Yentna 61.575950 -150.427410 Above major tributary
45.1 Deshka River 61.710142 -150.324700 Major tributary
59.9 Susitna 61.862200 -150.184630 Above major tributary
87.8 Susitna at Parks
Highway East 62.174531 -150.173677 Mainstem river site
102.8 Talkeetna River 62.342430 -150.112660 Major tributary
107 Talkeetna 62.397240 -150.137280 Upstream of existing townsite; Historic
(1980s) monitoring site
118.6 Chulitna River 62.567703 -150.237828 Major tributary
124.2 Curry Fishwheel Camp 62.617830 -150.013730 Important side channel habitat
140.1 Gold Creek 62.767892 -149.689781 Major tributary
142.2 Indian River 62.78635 -149.658780 Major tributary
142.3 Susitna above Indian
River 62.785776 -149.648900 Historic (1980s) monitoring site
152.2 Susitna below Portage
Creek 62.830397 -149.382743 Downstream of major tributary
152.3 Portage Creek 62.830379 -149.380289 Major tributary
152.7 Susitna above Portage
Creek 62.827002 -149. 827002 Historic (1980s) monitoring site
187.2 Susitna at Watana Dam
site 62.822600 -148.553000 Boundary condition between the reservoir
and riverine models
235.2 Oshetna River 62.639610 -147.383109 Uppermost tributary in the Project area
PRM = project river mile
Table 4.2-4. Focus Area Water Monitoring Sites
Focus Area PRM Latitude Longitude
Whiskers Slough 104 62.3729 -150.1572
Oxbow I 113 62.5015 -150.1027
Slough 6A 115 62.5142 -150.1115
Slough 8A 128 62.6605 -149.9193
Gold Creek 138 62.7657 -149.7079
Indian River 141 62.7856 -149.6459
Slough 21 144 62.8110 -149.5898
PRM = project river mile
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Table 5.1-1. Historic Mercury Concentrations at Gold Creek (PRM 140.1)
Date
Mercury in water
(filtered, µg/L)
Mercury in water
(unfiltered, µg/L)
Mercury in suspended
sediment (µg/kg)
6/14/77 NS <0.5 NS
8/10/77 NS <0.5 NS
10/4/77 NS 0.2 NS
6/23/81 NS 0.4 0.4
7/21/81 0.2 0.3 0.1
3/30/82 <0.1 <0.1 NS
7/1/82 <0.1 0.2 NS
9/16/82 <0.1 0.2 NS
3/18/83 <0.1 <0.1 NS
6/28/83 <0.1 0.1 NS
7/28/83 <0.1 0.3 NS
6/27/84 <0.1 0.1 NS
7/25/84 0.2 3.0 NS
6/27/85 0.2 0.0 NS
7/24/85 <0.1 <0.1 0.1
8/28/85 <0.1 <0.1 NS
3/24/86 <0.1 0.1 NS
6/25/86 <0.1 <0.1 NS
7/30/86 0.2 0.1 NS
8/25/86 0.8 0.5 NS
6/6/12 <0.005 0.007 NS
8/15/12 <0.005 0.008 NS
6/6/13 <0.005 0.023 NS
NS = not sampled
< = detection limit
µg/L = micrograms per liter
µg/kg = micrograms per kilogram
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Table 5.1-2. Historic Mercury Concentrations at Susitna at Parks Highway East (PRM 87.8)
Date Mercury in water
(filtered, µg/L)
Mercury in water
(unfiltered, µg/L)
Mercury in suspended
sediment (µg/kg)
6/15/77 NS <0.5 NS
8/10/77 NS <0.5 NS
10/4/77 NS <0.10 NS
3/25/81 0.10 0.1 0.0
6/25/81 0.00 0.6 0.6
7/23/81 0.10 0.3 0.2
7/2/82 <0.10 0.2 NS
9/15/82 0.10 0.2 0.1
10/13/82 0.10 0.1 0.0
1/20/83 <0.10 NS NS
3/17/83 <0.10 <0.10 NS
6/24/83 <0.10 0.2 NS
7/27/83 <0.10 0.3 NS
6/14/84 <0.10 0.9 NS
7/19/85 <0.10 0.1 NS
1/10/85 <0.10 <0.10 NS
6/25/85 <0.10 0.1 NS
7/23/85 <0.10 <0.10 NS
8/27/85 <0.10 <0.10 NS
3/18/86 <0.10 <0.10 NS
6/25/86 <0.10 <0.10 NS
6/5/12 <0.005 0.015 NS
8/13/12 <0.005 0.023 NS
6/3/13 <0.005 0.035 NS
NS = not sampled
< = detection limit
µg/L = micrograms per liter
µg/kg = micrograms per kilogram
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Table 5.1-3. Historic Mercury at Susitna Station (PRM 29.9)
Date Mercury in water
(filtered, µg/L)
Mercury in water
(unfiltered, µg/L)
Mercury in suspended
sediment (µg/kg)
1/20/75 <0.5 <0.5 0.0
5/23/75 <0.5 <0.5 0.0
8/27/75 <0.5 <0.5 0.0
10/3/75 <0.5 <0.5 0.0
3/17/76 <0.5 <0.5 0.0
5/28/76 <0.5 <0.5 0.0
7/26/76 <0.5 <0.5 0.3
10/6/76 <0.5 <0.5 0.0
3/9/77 <0.5 <0.5 NS
5/23/77 <0.5 <0.5 0.0
8/19/77 <0.5 <0.5 0.2
12/13/77 <0.1 <0.1 0.0
4/5/78 <0.1 <0.1 0.0
5/24/78 <0.1 <0.1 0.1
7/17/78 <0.1 0.2 0.1
1/15/79 <0.1 <0.1 0.1
5/14/79 <0.1 0.2 0.2
6/19/79 <0.1 <0.1 0.1
9/17/79 <0.1 <0.1 0.1
3/12/80 0.0 0.1 0.1
6/16/80 0.0 0.1 0.1
7/30/80 0.1 0.1 0.0
4/9/81 0.0 0.1 0.1
6/12/81 0.0 0.3 0.3
7/15/81 0.2 0.8 0.6
4/9/82 <0.1 <0.1 NS
5/19/82 <0.1 0.1 NS
7/14/82 0.2 0.2 0.0
10/5/82 0.1 NS NS
4/5/83 <0.1 NS NS
6/22/83 0.1 NS NS
7/27/83 <0.1 NS NS
9/30/83 <0.1 NS NS
4/6/84 <0.1 NS NS
5/18/84 <0.1 NS NS
7/18/84 <0.1 NS NS
9/20/84 <0.1 NS NS
3/27/85 0.1 NS NS
5/24/85 <0.1 NS NS
7/18/85 0.2 NS NS
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Date Mercury in water
(filtered, µg/L)
Mercury in water
(unfiltered, µg/L)
Mercury in suspended
sediment (µg/kg)
9/19/85 <0.1 NS NS
12/4/85 0.1 NS NS
7/29/86 0.1 NS NS
9/25/86 3.0 NS NS
5/30/13 <0.005 NS NS
NS= not sampled
< = detection limit
µg/L = micrograms per liter; µg/kg = micrograms per kilogram
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Table 5.1-4. ADEC Mercury Statewide Data Compared to Susitna-Watana
Species Date source Tissue Number Mean and Std. Dev.
(ng/g ww)
Median
(ng/g ww)
Range
(ng/g ww)
Lake trout ADEC Fillet 53 360 ± 180 320 64-740
Susitna-Watana Fillet 9 247± 171 173 136-637
Arctic grayling
ADEC Fillet 48 87 ± 34 82 33-180
Susitna-Watana Fillet 16 44 ± 24 37 19-100
Dolly Varden ADEC Fillet 22 120 ± 160 58 11-550
Susitna-Watana Fillet 7 43 ± 24 47 17-84
Humpback whitefish ADEC Fillet 98 67 ± 32 66 8-18
Round whitefish
ADEC Fillet 12 75 ± 56 68 8-200
Susitna-Watana Fillet 13 57± 29 55 6-102
Burbot
ADEC Fillet 27 330 ± 280 250 ND–850
Susitna-Watana Fillet 8 68 ± 27 64 36-113
Longnose sucker
ADEC Fillet 3 71 ± 12 73 59-82
Susitna-Watana Fillet 7 77 ± 42 68 33-138
All results are total mercury
ADEC = Alaska Department of Environmental Conservation
ng/g ww = nanograms per gram wet weight.
Susitna-Watana results are from this study. ADEC results are from ADEC (2012)
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Table 5.1-5. ADEC Mercury Data from Susitna Watershed
Species Site Name Fish Length (mm) Fish Weight (g) Age Sex Hg (ng/g dw)
Lake trout Lakes near Tyone Creek 600 2,939 NM M 130
Lakes near Tyone Creek 610 3,089 NM M 270
Lakes near Tyone Creek 730 5,294 NM F 740
Arctic grayling Lake Louise 288 200 4.5 M 110
Lake Louise 290 230 4 M 110
Lakes near Tyone Creek 200 NM 2 NM 95
Lakes near Tyone Creek 201 NM 2 NM 91
Lakes near Tyone Creek 330 340 5 F 180
Lakes near Tyone Creek 278 200 <1 F 160
Lakes near Tyone Creek 220 110 2 M 110
Lakes near Tyone Creek 270 190 3.5 F 80
Lakes near Tyone Creek 290 230 4 NM 80
Finger Lake 370 460 7 M 67
Fishook Lake 310 310 4 F 77
Fishook Lake 370 160 7 F 100
Fishook Lake 320 350 5 M 130
Upper Talkeetna River 360 420 6.5 NM 93
Upper Talkeetna River 370 430 7 M 51
Christianson Lake 260 160 3.5 F 120
Christianson Lake 204 10 2.5 NM 130
Christianson Lake 272 190 3.5 F 59
Burbot Big Lake 579 1,038 9 NM 94
Round whitefish Knob Lake 390 490 20 F 120
Knob Lake 360 310 7 F 200
Knob Lake 340 220 8 F 78
Knob Lake 320 230 6 M 58
Knob Lake 280 150 1 M 90
Coal Creek Lake 330 290 12 M 140
Coal Creek Lake 310 220 13 F 79
mm = millimeters, g = grams, NM = not measured, M=male, F = female
ng/g dw = nanograms per gram dry weight
All results are from ADEC (2012)
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Table 5.1-6. Mercury in Cook Inlet Freshwater Sediments and Slimy Sculpin Tissue
Site Name Sediment Hg (ng/g dw) Slimy Sculpin Hg (ng/g dw)
Susitna-Watana (this study) 6.7 (mean) 178 (mean)
Ninilchik River 50 150
Kenai River at Soldotna 30 200
South Fork Campbell Creek 30 210
Chester Creek 180 100
Talkeetna River 40 80
Deshka River 460 110
Moose Creek 200 160
Kamishak River 40 90
Johnson River 130 NS
Kenai River Below Russian 70 120
Kenai River at Jim’s Landing 90 140
Kenai River below Skilak Lake Outlet 70 150
Colorado Creek 180 NS
Costelllo Creek 230 80
National mean 60 NA
National mean is derived from Gilliom et al (1998)
Fish and sediment data for Cook Inlet freshwater is derived from Frenzel (2000)
ng/g dw = nanograms per gram dry weight
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Table 5.1-7. Mercury Partitioning in Cook Inlet Freshwater Sediments and Fish
Site Name
Total Hg in
Sediment
(ng/g dw)
MeHg in
Sediment
(ng/g dw)
Total Hg in Fish (ng/g dw) Total Hg in
Water (ng/L)
MeHg in
water (ng/L)
Susitna-Watana at Dam site
(This Study) 6.7 (mean) NS 178 Slimy Sculpin (mean) 3.531 NS 183 Dolly Varden (mean)
South Fork Campbell Creek 200 0.67 292 Slimy Sculpin 2.50 0.02 429 Dolly Varden
Chester Creek 109 0.38 152 Slimy Sculpin 2.96 0.02 ND Dolly Varden
Deshka River 21 5.10 246 Slimy Sculpin NS NS
Johnson River 50 0.01 NS 9.78 0.02
Costelllo Creek 169 0.04 ND Slimy Sculpin 4.97 0.02 101 Dolly Varden
ND = not detected. NS = not sampled.
Fish and sediment data for Cook Inlet freshwater is derived from Frenzel (2000)
1 = as measured at dam site July 2014.
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Table 5.1-8. WACAP Data for Lichen Samples
Site Name Species Number Median Hg (ng/g ww)
NOAT Masonhalea richardsonii 3 17
NOAT Flavocetraria cucullata 2 23
GAAR Masonhalea richardsonii 2 22
GAAR Flavocetraria cucullata 4 26
DNP Masonhalea richardsonii 6 12
DNP Flavocetraria cucullata 6 21
NOAT = Noatak National Preserve; GAAR = Gates of the Arctic National Park; and DNP = Denali National Park
ng/g ww = nanograms per gram wet weight
Data from WACAP (2008)
Table 5.1-9. WACAP sand USGS Data for Alaska Fish
Site Name Species Number Mean Age Mean Hg (ng/g ww)
Susitna-Watana (This Study) Lake trout 9 12 173
Susitna-Watana (This Study) Burbot 8 5 64
Susitna-Watana (This Study) Arctic grayling 16 4 44
NOAT Burial Lake Lake trout 10 20 130
GAAR Matcharak Lake Lake trout 10 18 218
DNP Wonder Lake Lake trout 10 17 113
DNP McLeod Lake Burbot 4 4 58
WSENP Copper Lake Lake trout 15 13 145
WSENP Grizzly Lake Burbot 15 11 41
WSENP Tanada lake Lake trout 15 14 372
WSENP Tanada lake Burbot 13 11 383
WSENP Tanada lake Arctic Grayling 10 11 109
Results are for whole body samples.
NOAT = Noatak National Preserve; GAAR = Gates of the Arctic National Park; DNP = Denali National Park; WSENP = Wrangell St. Elias National Park
ng/g ww = nanograms per gram wet weight.
Data from WACAP (2008) and USGS (2014)
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Table 5.2-1. Plant Species Observed and Collected at Each Sample Site
Species Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Site-7 Site-8 Site-9 Site-10
Alder (Alnus spp.) X X X X X X X X
Willow (Salix spp.) X X O X X X X X X X
Bog Blueberry (Vaccinium uliginosum) X X X X X X X X X X
Low-bush Cranberry (Vaccinium vitus-
idaea) X X X X X X O X X
Salmonberry (Rubus spectabilis) X X
Prickly Rose (Rosa acicularis) X O X O X X
Crowberry (Empetrum nigrum) X X O O X O
American Red Currant (Ribes triste) X
Clover (Trifolium sp.) X
Spruce (Picea sp.) X O O
Sweet Gale (Myrica gale) X O
Arctic Coltsfoot (Petasites frigidus) O O O X X X
Horsetail (Equisetum sp.) O O O O O O O O
Bog Birch (Betula glandulosa) O O O O O O O O O
Bush Cinquefoil (Dasiphora fruticosa) O O O O O O
Common Labrador Tea (Ledum
groenlandicum) O O O O O O O O O
Cloudberry (Rubus chamaemorus) O O O
Wintergreen (Pyrola sp.) O O O
Dwarf Dogwood (Cornus canadensis) O O O
Soapberry (Shepherdia canadensis) O
Twisted Stalk (Streptopus amplexifolius) O
Fireweed (Chamerion angustifolium) O
Marsh Five-finger (Comarum palustre) O
Red Bearberry (Arctostaphylos rubra) O O O O O
X are plants included in the sampling. O are plants observed, but not included due to low vegetative mass.
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Table 5.2-2. Vegetation Results
Location Latitude Longitude PRM % solids Total Hg
(ng/g dw)
Total Hg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
SITE-1 N1 62.8206 -148.1557 200.3 29.10 8.61 2.51 <3.42 <1.00
SITE-1 N2 62.8207 -148.1560 200.3 39.11 7.00 2.74 <2.54 <0.99
SITE-1 N3 62.8206 -148.1553 200.3 25.52 10.1 2.59 <3.73 <0.95
SITE-1 N4 62.8207 -148.1562 200.3 31.94 8.63 2.75 <3.08 <0.99
SITE-1 N5 62.8206 -148.1552 200.3 33.60 7.79 2.62 <2.90 <0.98
SITE-2 N1 62.7976 -148.0707 203.8 35.50 7.46 2.65 <2.73 <0.97
SITE-2 N2 62.7975 -148.0706 203.8 36.32 7.31 2.66 <2.54 <0.92
SITE-2 N3 62.7974 -148.0704 203.8 35.72 8.04 2.87 <2.61 <0.93
SITE-2 N4 62.7976 -148.0708 203.8 30.30 9.54 2.89 <3.18 <0.96
SITE-2 N5 62.7973 -148.0703 203.8 36.63 7.39 2.71 <2.55 <0.93
SITE-2 N6 62.7973 -148.0703 203.8 37.52 7.48 2.81 <2.57 <0.96
SITE-3 N1 62.7895 -148.0556 208.0 32.63 13.3 4.32 <2.93 <0.96
SITE-3 N2 62.7895 -148.0561 208.0 33.63 13.0 4.36 <2.75 <0.92
SITE-3 N3 62.7897 -148.0551 208.0 34.53 8.15 2.82 <2.65 <0.91
SITE-3 N4 62.7896 -148.0563 208.0 34.73 9.23 3.20 <2.75 <0.95
SITE-3 N5 62.7898 -148.0552 208.0 36.62 8.97 3.29 <2.68 <0.98
SITE-3 N6 62.7898 -148.0552 208.0 31.86 10.7 3.40 <3.06 <0.97
SITE-4S alt1 62.7884 -148.0074 206.2 37.09 7.98 2.96 <2.68 <0.99
SITE-4S alt2 62.7883 -148.0077 206.2 32.04 9.04 2.9 <2.96 <0.95
SITE-4S alt3 62.7883 -148.0071 206.2 31.84 9.01 2.87 <3.07 <0.98
SITE-4S alt4 62.7883 -148.0079 206.2 28.84 8.08 2.33 <3.24 <0.93
SITE-4S alt5 62.7883 -148.0068 206.2 33.01 8.39 2.77 <2.81 <0.93
SITE-4S alt6 62.7883 -148.0068 206.2 30.62 6.71 2.06 <3.08 <0.94
SITE-5S 1 62.7842 -147.9521 208.2 27.77 7.56 2.10 <3.44 <0.96
SITE-5S 2 62.7845 -147.9521 208.2 24.23 9.80 2.38 <3.87 <0.94
SITE-5S 3 62.7842 -147.9520 208.2 31.16 11.2 3.49 <3.06 <0.95
SITE-5S 4 62.7846 -147.9524 208.2 21.11 16.1 3.39 <4.77 <1.01
SITE-5S 5 62.7840 -147.9519 208.2 29.13 8.75 2.55 <3.23 <0.94
SITE-6S-1 62.7790 -147.9189 209.8 33.38 7.19 2.4 <2.97 <0.99
SITE-6S-2 62.7789 -147.9195 209.8 35.96 8.92 3.21 <2.69 <0.97
SITE-6S-3 62.7790 -147.9185 209.8 33.73 7.00 2.36 <2.96 <1.00
SITE-6S-4 62.7788 -147.9198 209.8 35.50 11.2 3.99 <2.60 <0.92
SITE-6S-5 62.7792 -147.9183 209.8 31.42 7.88 2.48 <3.13 <0.98
SITE-7 N1 62.7784 -147.8787 211.5 22.39 10.3 2.32 <4.28 <0.96
SITE-7 N2 62.7784 -147.8787 211.5 29.17 9.16 2.67 <3.23 <0.94
SITE-7 N3 62.7786 -147.8787 211.5 26.71 12.2 3.26 <3.68 <0.98
SITE-7 N4 62.7782 -147.8789 211.5 27.57 12.3 3.38 <3.32 <0.91
SITE-7 N5 62.7787 -147.8789 211.5 18.70 11.4 2.14 <5.15 <0.96
SITE-7 N6 62.7787 -147.8789 211.5 20.47 10.5 2.14 <4.93 <1.01
SITE-8 S1 62.7728 -147.8483 212.5 31.62 7.45 2.35 <3.03 <0.96
SITE-8 S2 62.7729 -147.8481 212.5 29.63 8.56 2.54 <3.36 <1.00
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Location Latitude Longitude PRM % solids Total Hg
(ng/g dw)
Total Hg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
SITE-8 S3 62.7725 -147.8484 212.5 24.31 11.4 2.77 <3.82 <0.93
SITE-8 S4 62.7731 -147.8480 212.5 30.33 9.36 2.84 <3.22 <0.98
SITE-8 S5 62.7724 -147.8486 212.5 27.78 7.57 2.10 <3.48 <0.97
SITE-9 N1 62.8509 -148.2314 NA 31.71 7.45 2.36 <2.95 <0.93
SITE-9 N2 62.8508 -148.2316 NA 31.14 7.91 2.46 <3.17 <0.99
SITE-9 N3 62.8509 -148.2311 NA 31.26 7.89 2.47 <3.13 <0.98
SITE-9 N4 62.8510 -148.2317 NA 29.11 9.02 2.63 <3.27 <0.95
SITE-9 N5 62.8507 -148.2310 NA 34.55 7.79 2.69 <2.85 <0.99
SITE-9 N6 62.8507 -148.2310 NA 32.96 8.27 2.73 <2.85 <0.94
SITE-10 N1 62.8577 -148.2133 NA 27.93 10.7 3.00 <3.28 0.92
SITE-10 N2 62.8574 -148.2131 NA 31.02 8.78 2.7 <3.03 <0.94
SITE-10 N3 62.8572 -148.2134 NA 32.11 10.7 3.42 <3.05 <0.98
SITE-10 N4 62.8576 -148.2129 NA 32.11 7.79 2.5 <2.94 <0.95
SITE-10 N5 62.8571 -148.2136 NA 30.20 9.60 2.9 <3.09 <0.93
ng/g dw = nanograms per gram dry weight
ng/g ww = nanograms per gram wet weight
Hg= mercury
MeHg = methylated mercury
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Table 5.3-1. Soil Results
EPA Method 1631
(Sed./Soil)
EPA Method 1631
(Organic)
Location Sample
Number
Latitude Longitude PRM Soil
Description
Moss
(cm)
Peat
(cm)
Total
organics
(cm)
% Total
Solids
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
SITE-1 N-1 62.8206 -148.1557 200.3 Silt with clay 4.50 9.5 14.0 25.05 64.6 0.570 59.0 <3.90
SITE-1 N-2 62.8207 -148.1560 200.3 Silt with clay 6.50 18.0 24.5 19.59 60.8 1.30 50.0 <4.70
SITE-1 N-3 62.8206 -148.1553 200.3 Silt with clay 5.00 13.0 18.0 20.68 50.7 0.283 51.6 <4.74
SITE-1 N-4 62.8207 -148.1562 200.3 Silt with clay 3.50 6.5 10.0 21.23 59.6 2.62 57.1 <4.69
SITE-1 N-5 62.8206 -148.1552 200.3 Silt with Clay 4.00 14.5 18.5 41.76 43.9 0.224 39.0 <2.28
SITE-2 N-1 62.7976 -148.0707 203.8 Silt 4.50 8.9 13.4 27.19 59.1 0.365 58.6 <3.50
SITE-2 N-2 62.7975 -148.0706 203.8 Silt 3.60 15.0 18.6 23.69 77.9 0.341 80.5 <4.11
SITE-2 N-3 62.7974 -148.0704 203.8 Clayey silt 8.50 13.0 21.5 27.93 68.3 0.247 59.2 <3.34
SITE-2 N-4 62.7976 -148.0708 203.8 Silt 4.80 19.0 23.8 31.25 68.5 0.214 65.7 <3.07
SITE-2 N-5 62.7973 -148.0703 203.8 Clayey silt 3.80 9.2 13.0 23.55 63.9 0.188 54.5 <4.16
SITE-2 N-6 62.7973 -148.0703 203.8 Clayey silt 3.80 9.2 13.0 19.65 67.0 0.371 51.4 <5.06
SITE-3 N-1 62.7895 -148.0556 208.0 Clayey silt 4.50 28.5 33.0 26.12 64.2 0.469 61.8 <3.76
SITE-3 N-2 62.7895 -148.0561 208.0 Clayey silt 4.50 20.5 25.0 26.02 119 0.210 129 <3.51
SITE-3 N-3 62.7897 -148.0551 208.0 Clayey silt 4.50 15.3 19.8 28.30 107 0.225 89.6 <3.30
SITE-3 N-4 62.7896 -148.0563 208.0 Clayey silt 3.50 9.0 12.5 28.01 105 0.135 106 <3.47
SITE-3 N-5 62.7898 -148.0552 208.0 Clayey silt 7.00 5.0 12.0 27.28 70.1 0.384 64.2 <3.50
SITE-3 N-6 62.7898 -148.0552 208.0 Clayey silt 7.00 5.0 12.0 25.91 73.6 0.280 64.2 <3.66
SITE-4S alt 1 62.7884 -148.0074 206.2 Silt 3.80 6.2 10.0 19.25 48.0 0.424 45.7 <4.98
SITE-4S alt 2 62.7883 -148.0077 206.2 Silt 12.50 4.2 16.7 22.44 48.1 0.213 45.8 <4.60
SITE-4S alt 3 62.7883 -148.0071 206.2 Silt 4.20 8.2 12.4 26.26 58.2 0.228 54.6 <3.48
SITE-4S alt 4 62.7883 -148.0079 206.2 Silt 1.90 0.0 1.9 20.32 50.5 0.325 53.8 <5.37
SITE-4S alt 5 62.7883 -148.0068 206.2 Silt 8.20 6.2 14.4 25.60 46.2 0.257 43.8 <3.71
SITE-4S alt 6 62.7883 -148.0068 206.2 Silt 8.20 6.2 14.4 26.42 43.0 0.102 38.7 <3.61
SITE-5S 1 62.7842 -147.9521 208.2 Silty sand 4.00 4.0 8.0 38.09 60.2 0.267 54.1 <2.73
SITE-5S 2 62.7845 -147.9521 208.2 Clayey silt sand 5.00 8.0 13.0 33.27 40.2 0.159 39.6 <3.27
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EPA Method 1631
(Sed./Soil)
EPA Method 1631
(Organic)
Location Sample
Number
Latitude Longitude PRM Soil
Description
Moss
(cm)
Peat
(cm)
Total
organics
(cm)
% Total
Solids
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
SITE-5S 3 62.7842 -147.9520 208.2 Silty sand 4.50 15.0 19.5 35.95 47.7 0.198 49.8 <2.87
SITE-5S 4 62.7846 -147.9524 208.2 Clayey silty
sand
3.80 8.1 11.9 44.67 37.8 0.136 37.3 <2.34
SITE-5S 5 62.7840 -147.9519 208.2 Clayey silt 4.30 2.5 6.8 23.48 74.8 0.171 75.2 <4.33
SITE-6S 1 62.7790 -147.9189 209.8 Silty sand 3.50 1.0 4.5 30.25 37.3 2.55 34.3 8.80
SITE-6S 2 62.7789 -147.9195 209.8 Silty sand 2.50 0.0 2.5 54.53 27.1 0.305 33.3 <1.88
SITE-6S 3 62.7790 -147.9185 209.8 Silt 5.50 2.0 7.5 28.91 35.3 3.97 36.9 8.03
SITE-6S 4 62.7788 -147.9198 209.8 Silty sand 2.00 0.0 2.0 29.87 27.3 0.192 26.8 <3.43
SITE-6S 5 62.7792 -147.9183 209.8 Clayey silt 6.00 10.0 16.0 23.90 33.7 4.34 35.8 6.51
SITE-7 N-1 62.7784 -147.8787 211.5 Silt 4.30 0.0 4.3 18.44 45.2 0.137 49.2 <4.91
SITE-7 N-2 62.7784 -147.8787 211.5 Silt 3.50 0.0 3.5 19.47 60.4 0.252 61.9 <5.34
SITE-7 N-3 62.7786 -147.8787 211.5 Silt 6.00 0.0 6.0 20.71 70.1 0.190 71.0 <5.05
SITE-7 N-4 62.7782 -147.8789 211.5 Silt 4.50 5.0 9.5 23.41 100 0.508 100 <4.22
SITE-7 N-5 62.7787 -147.8789 211.5 Silt 3.80 0.0 3.8 23.61 72.8 0.266 75.6 4.05
SITE-7 N-6 62.7787 -147.8789 211.5 Silt 3.80 0.0 3.8 19.50 48.9 0.157 51.3 <5.07
SITE-8 S-1 62.7728 -147.8483 212.5 Silt 3.50 0.0 3.5 37.62 42.4 1.10 42.7 2.67
SITE-8 S-2 62.7729 -147.8481 212.5 Silt 4.00 0.0 4.0 26.54 77.8 0.349 65.6 <3.63
SITE-8 S-3 62.7725 -147.8484 212.5 Silt 4.00 0.0 4.0 42.70 44.8 0.681 48.0 <2.48
SITE-8 S-4 62.7731 -147.8480 212.5 Clayey Silt 3.80 0.0 3.8 28.67 52.6 0.193 54.9 3.62
SITE-8 S-5 62.7724 -147.8486 212.5 Clayey silt 3.50 0.0 3.5 35.36 59.8 2.37 59.3 2.99
SITE-9 N-1 62.85085 -148.2314 NA Clayey silt 3.50 7.5 11.0 27.66 44.9 0.096 44.5 <3.40
SITE-9 N-2 62.85083 -148.2316 NA Silt 3.00 6.5 9.5 32.48 106 0.218 109 <2.81
SITE-9 N-3 62.85089 -148.2311 NA Silt 3.50 11.5 15.0 17.51 30.6 0.189 36.5 <5.22
SITE-9 N-4 62.85104 -148.2317 NA Clayey silt 4.00 9.5 13.5 25.17 49.8 0.205 40.0 <3.85
SITE-9 N-5 62.85074 -148.2310 NA Clayey silt 6.00 7.5 13.5 30.99 42.3 0.182 47.3 <3.09
SITE-9 N-6 62.85074 -148.2310 NA Clayey Silt 6.00 7.5 13.5 26.73 49.9 0.193 53.7 <3.69
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EPA Method 1631
(Sed./Soil)
EPA Method 1631
(Organic)
Location Sample
Number
Latitude Longitude PRM Soil
Description
Moss
(cm)
Peat
(cm)
Total
organics
(cm)
% Total
Solids
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
Total Hg
(ng/g dw)
Total MeHg
(ng/g dw)
SITE-10 N-1 62.8577 -148.2133 NA Clayey Silt 7.00 6.5 13.5 27.14 97.4 1.67 67.1 <3.47
SITE-10 N-2 62.8574 -148.2131 NA Clayey silt 5.50 7.5 13.0 27.85 69.6 0.539 67.7 <3.43
SITE-10 N-3 62.8572 -148.2134 NA Clayey silt 4.50 6.8 11.3 29.75 84.5 0.843 76.3 <3.08
SITE-10 N-4 62.8576 -148.2129 NA Clayey silt 4.50 6.5 11.0 25.24 81.7 0.321 75.5 <3.83
SITE-10 N-5 62.8571 -148.2136 NA Clayey silt 2.5 1.5 4.0 23.98 55.0 0.689 53.3 <4.14
NA = not applicable - site is inside inundation zone, but equidistant from more than one part of the river.
PRM = project river mile
cm = centimeter
ng/g dw = nanograms per gram dry weight
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Table 5.4-1 Surface Water Results Baseline Water Quality
Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
Hg (ng/L)
Max
Dissolved
Hg (ng/L)
Mean
Dissolved
Hg (ng/L)
Susitna Station 29.9
June 2013 6 22.6 29.1 25.9 <0.5 0.642 <0.5
July 2013 6 27.4 32.1 29.1 All samples <0.5
August 2013 6 15.9 26.5 21.4 All samples <0.5
September 2013 6 6.90 16.3 12.7 0.799 1.48 0.989
January 2014 1 2.26 2.26 2.26 1.19 1.19 1.19
March 2014 2 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
June 2014 1 18.7 18.7 18.7 NA NA NA
July 2014 1 14.1 14.1 14.1 NA NA NA
August 2014 1 25.1 25.1 25.1 NA NA NA
September 2014 1 6.09 6.09 6.09 NA NA NA
Yentna River 32.5
June 2013 4 30.6 27.2 28.7 0.523 0.874 0.729
July 2013 6 27.1 33.6 29.4 <0.5 0.680 <0.5
August 2013 6 14.4 21.5 17.8 All samples <0.5
September 2013 6 14.0 19.2 15.3 0.581 0.809 0.683
June 2014 1 13.6 13.6 13.6 NA NA NA
July 2014 1 8.43 8.43 8.43 NA NA NA
August 2014 1 31.4 31.4 31.4 NA NA NA
September 2014 1 10.6 10.6 10.6 NA NA NA
Susitna above Yentna 33.6
June 2013 6 37.5 44.9 41.5 0.712 1.23 0.866
July 2013 6 56.3 66.6 60.7 0.653 0.743 0.696
August 2013 6 25.3 33.7 29.3 <0.5 1.59 0.517
September 2013 6 9.82 60.5 19.7 <0.5 0.720 0.513
June 2014 1 8.37 8.37 8.37 NA NA NA
July 2014 1 13.6 13.6 13.6 NA NA NA
August 2014 1 13.4 13.4 13.4 NA NA NA
September 2014 1 3.18 3.18 3.18 NA NA NA
Deshka River 45.1
June 2013 6 1.00 1.64 1.22 0.713 0.838 0.810
July 2013 5 1.11 1.54 1.25 1.00 1.34 1.25
August 2013 5 0.923 1.31 1.13 0.650 1.31 0.783
September 2013 5 3.75 4.17 3.98 2.91 3.36 3.14
June 2014 1 1.09 1.09 1.09 NA NA NA
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Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
Hg (ng/L)
Max
Dissolved
Hg (ng/L)
Mean
Dissolved
Hg (ng/L)
July 2014 1 1.26 1.26 1.26 NA NA NA
August 2014 1 0.58 0.58 0.58 NA NA NA
September 2014 1 0.99 0.99 0.99 NA NA NA
Susitna 59.9
June 2013 5 51.7 58.7 55.8 <0.5 0.892 0.632
July 2013 5 28.0 34.3 30.8 <0.5 0.674 <0.5
August 2013 5 24.8 28.7 27.6 <0.5 2.15 0.630
September 2013 5 6.48 7.55 6.88 All samples <0.5
June 2014 1 10.4 10.4 10.4 NA NA NA
July 2014 1 10.8 10.8 10.8 NA NA NA
August 2014 1 13.3 13.3 13.3 NA NA NA
September 2014 1 2.75 2.75 2.75 NA NA NA
Susitna at Parks
Highway East
87.8
June 2013 5 51.0 80.1 66.8 <0.5 0.815 0.5
July 2013 5 33.4 60.2 39.9 <0.5 0.558 <0.5
August 2013 5 26.5 32.4 29.3 <0.5 1.54 0.618
September 2013 6 12.3 22.4 18.4 0.599 0.762 0.700
January 2014 1 1.18 1.18 1.18 0.636 0.636 0.636
March 2014 1 All samples <0.5 All samples <0.5
June 2014 1 21.1 21.1 21.1 NA NA NA
July 2014 1 5.8 5.8 5.8 NA NA NA
August 2014 1 14.8 14.8 14.8 NA NA NA
September 2014 1 3.49 3.49 3.49 NA NA NA
Talkeetna River 102.8
June 2013 4 40.6 67.3 51.1 1.07 1.15 1.12
July 2013 3 NS NS NS 0.912 2.54 1.48
August 2013 3 57.4 78.3 67.9 0.509 0.855 0.709
September 2013 4 4.3 28.4 13.0 0.768 1.06 0.880
June 2014 1 2.64 2.64 2.64 NA NA NA
July 2014 1 18.5 18.5 18.5 NA NA NA
August 2014 1 23.0 23.0 23.0 NA NA NA
September 2014 1 2.66 2.66 2.66 NA NA NA
June 2013 6 13.2 17.9 14.8 <0.5 1.21 0.640
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Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
Hg (ng/L)
Max
Dissolved
Hg (ng/L)
Mean
Dissolved
Hg (ng/L)
Talkeetna 107.0
July 2013 5 12.2 13.1 12.8 <0.5 0.819 <0.5
August 2013 5 18.3 25.3 19.2 <0.5 1.11 0.511
September 2013 6 11.0 14.7 12.9 <0.5 0.668 0.524
June 2014 1 2.39 2.39 2.39 NA NA NA
July 2014 1 3.65 3.65 3.65 NA NA NA
August 2014 1 2.36 2.36 2.36 NA NA NA
September 2014 1 1.02 1.02 1.02 NA NA NA
Chulitna River
118.6
June 2013 6 38.8 54.5 47.1 0.563 0.874 0.660
July 2013 6 35.3 52.4 41.0 <0.5 1.57 0.549
August 2013 6 32.4 45.3 38.3 <0.5 3.54 0.798
September 2013 6 19.1 39.1 29.7 0.632 0.898 0.779
June 2014 1 24.6 24.6 24.6 NA NA NA
July 2014 1 23.2 23.2 23.2 NA NA NA
August 2014 1 27.1 27.1 27.1 NA NA NA
September 2014 1 4.95 4.95 4.95 NA NA NA
Curry Fishwheel
Camp 124.2
June 2013 6 11.1 15.8 12.9 <0.5 0.612 <0.5
July 2013 6 12.7 16.0 14.2 <0.5 2.28 1.39
August 2013 6 15.2 18.5 17.1 <0.5 0.521 <0.5
September 2013 6 4.84 6.04 5.25 <0.5 0.669 <0.5
June 2014 1 3.41 3.41 3.41 NA NA NA
July 2014 1 4.98 4.98 4.98 NA NA NA
August 2014 1 2.81 2.81 2.81 NA NA NA
September 2014 1 1.09 1.09 1.09 NA NA NA
Gold Creek 140.1
June 2013 6 14.3 21.1 18.1 <0.5 0.631 <0.5
July 2013 5 10.5 12.3 11.2 0.501 0.815 0.576
August 2013 6 15.3 16.7 16.0 <0.5 0.664 <0.5
September 2013 5 3.41 8.54 5.30 <0.5 0.637 <0.5
January 2014 3 0.57 1.04 0.763 <0.5 0.524 <0.5
March 2014 1 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
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Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
Hg (ng/L)
Max
Dissolved
Hg (ng/L)
Mean
Dissolved
Hg (ng/L)
June 2014 1 3.72 3.72 3.72 NA NA NA
July 2014 1 5.08 5.08 5.08 NA NA NA
August 2014 1 2.36 2.36 2.36 NA NA NA
September 2014 1 1.53 1.53 1.53 NA NA NA
Indian River 142.2
June 2013 6 15.8 25.0 20.8 <0.5 0.658 0.536
July 2013 6 9.09 10.9 10.2 <0.5 0.704 <0.5
August 2013 5 17.9 21.3 19.8 <0.5 0.949 <0.5
September 2013 6 3.34 9.75 5.52 0.513 4.02 1.16
June 2014 1 3.78 3.78 3.78 NA NA NA
July 2014 1 9.69 9.69 9.69 NA NA NA
August 2014 1 2.07 2.07 2.07 NA NA NA
September 2014 1 1.69 1.69 1.69 NA NA NA
Susitna above Indian
River 142.3
June 2013 5 11.9 15.6 13.4 <0.5 0.683 0.538
July 2013 4 7.74 8.74 8.15 <0.5 1.01 0.511
August 2013 5 19.0 23.1 20.7 <0.5 0.851 0.602
September 2013 6 3.22 5.37 4.06 0.521 0.699 0.594
June 2014 1 3.31 3.31 3.31 NA NA NA
July 2014 1 4.50 4.50 4.50 NA NA NA
August 2014 1 3.44 3.44 3.44 NA NA NA
September 2014 1 1.92 1.92 1.92 NA NA NA
Portage Creek 152.3
July 2013 6 17.8 23.0 20.5 All samples <0.5
August 2013 6 3.69 30.6 19.7 <0.5 0.583 <0.5
September 2013 6 1.75 4.84 3.68 0.723 2.20 1.29
June 2014 1 3.86 3.86 3.86 NA NA NA
July 2014 1 3.74 3.74 3.74 NA NA NA
August 2014 1 1.76 1.76 1.76 NA NA NA
September 2014 1 1.77 1.77 1.77 NA NA NA
Susitna above
Portage 152.7 July 2013 6 19.6 22.9 21.9 All samples <0.5
August 2013 6 23.2 25.8 24.4 <0.5 0.672 <0.5
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Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
Hg (ng/L)
Max
Dissolved
Hg (ng/L)
Mean
Dissolved
Hg (ng/L)
September 2013 6 4.23 5.50 4.88 0.801 0.958 0.871
June 2014 1 5.20 5.20 5.20 NA NA NA
July 2014 1 6.39 6.39 6.39 NA NA NA
August 2014 1 3.32 3.32 3.32 NA NA NA
September 2014 1 2.94 2.94 2.94 NA NA NA
Susitna 174.0 August 2014 2 2.32 10.0 6.16 All samples <0.5
September 2014 1 2.99 2.99 2.99 1.70 1.70 1.70
Susitna at Watana
Dam
187.2
June 2013 1 22.0 22.0 22.0 All samples <0.5
July 2013 1 12.6 12.6 12.6 0.722 0.722 0.722
August 2013 2 11.3 12.6 11.7 <0.5 1.17 0.629
September 2013 1 3.31 3.31 3.31 1.46 1.46 1.46
185.01 January 2014 1 0.784 0.784 0.784 All samples <0.5
March 2014 1 0.536 0.536 0.536 All samples <0.5
187.2
June 2014 1 3.40 3.40 3.40 NA NA NA
July 2014 1 3.53 3.53 3.53 NA NA NA
August 2014 1 2.81 2.81 2.81 NA NA NA
September 2014 1 0.83 0.83 0.83 NA NA NA
Oshetna River
235.2
June 2013 1 22.2 22.2 22.2 0.762 0.762 0.762
July 2013 1 15.6 15.6 15.6 0.971 0.971 0.971
August 2013 1 3.43 3.43 3.43 <0.5 <0.5 <0.5
September 2013 1 3.15 3.15 3.15 1.57 1.57 1.57
225.01 January 2014 1 0.705 0.705 0.705 0.525 0.525 0.525
March 2014 1 All samples <0.5 All samples <0.5
235.2
June 2014 1 2.94 2.94 2.94 NA NA NA
July 2014 1 3.16 3.16 3.16 NA NA NA
August 2014 1 0.99 0.99 0.99 NA NA NA
September 2014 1 3.09 3.09 3.09 NA NA NA
1 alternate winter sample location based on limited site access
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Table 5.4-2. Surface Water Results Focus Areas
Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
MeHg (ng/L)
Max
Dissolved
MeHg (ng/L)
Mean
Dissolved
MeHg (ng/L)
Whiskers Slough 104
July 28, 2013 14 11.3 14.5 12.2 <0.020 <0.020 <0.020
August 11 2013 14 5.8 19.4 10.1 <0.020 <0.020 <0.020
August 30, 2013 14 13.4 24.7 17.9 <0.020 0.08 <0.020
July 24, 2014 6 1.94 4.05 2.86 NS NS NS
September 17, 2014 6 3.88 5.03 4.51 NS NS NS
Oxbow 1 113
July 27, 2013 8 11.5 13.9 12.5 <0.020 <0.020 <0.020
August 10, 2013 8 8.76 14.9 12.4 <0.020 <0.020 <0.020
August 20, 2013 8 18.2 23.0 20.2 <0.020 <0.020 <0.020
July 17, 2014 3 3.69 4.21 3.96 NS NS NS
September 16, 2014 3 <0.10 <0.10 <0.10 NS NS NS
Lane Creek 115
July 26, 2013 14 11.4 20.8 13.5 <0.020 0.025 <0.020
August 9, 2013 14 11.9 14.4 12.7 <0.020 <0.020 <0.020
August 24, 2013 14 7.07 14.9 9.5 <0.020 <0.020 <0.020
July 17, 2014 6 3.63 4.63 4.21 NS NS NS
September 6, 2014 6 3.06 3.38 3.21 NS NS NS
Skull Creek Complex 128
July 25, 2013 11 11.1 15.0 12.3 <0.020 <0.020 <0.020
August 8, 2013 11 8.49 12.0 10.1 <0.020 <0.020 <0.020
August 25, 2013 11 6.54 11.4 7.90 <0.020 <0.020 <0.020
July 17, 2014 5 4.19 5.31 4.85 NS NS NS
September 16, 2014 5 0.89 1.22 1.02 NS NS NS
Gold Creek 138
July 24, 2013 6 10.5 14.8 12.4 <0.020 <0.020 <0.020
August 7, 2013 6 9.83 10.5 10.2 <0.020 <0.020 <0.020
August 23, 2013 6 4.92 5.60 5.30 <0.020 <0.020 <0.020
July 16, 2014 2 3.6 15.3 9.45 NS NS NS
September 14, 2014 2 0.83 1.43 1.13 NS NS NS
Indian River 141
July 23, 2013 9 10.9 13.4 12.3 <0.020 <0.020 <0.020
August 6, 2013 9 9.33 12.9 11.4 <0.020 <0.020 <0.020
August 22, 2013 9 25.5 84.3 47.2 <0.020 <0.020 <0.020
July 15, 2014 3 7.05 9.87 8.13 NS NS NS
September 10, 2014 3 1.23 1.35 1.28 NS NS NS
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Location PRM Month N Min Total
Hg (ng/L)
Max Total
Hg (ng/L)
Mean
Total Hg
(ng/L)
Min
Dissolved
MeHg (ng/L)
Max
Dissolved
MeHg (ng/L)
Mean
Dissolved
MeHg (ng/L)
Side Channel 21 144
July 22, 2013 10 13.8 25.5 16.3 <0.020 <0.020 <0.020
August 5, 2013 10 13.9 15.7 14.6 <0.020 <0.020 <0.020
August 21, 2013 10 15.3 47.2 26.2 <0.020 0.085 <0.020
July 15, 2014 3 6.72 8.46 7.51 NS NS NS
September 10, 2014 3 0.95 1.21 1.04 NS NS NS
PRM = project river mile
N = number of samples
Hg = mercury
MeHg = methylmercury
ng/L = nanograms per liter
< = detection limit
Max = maximum
Min = minimum
NS = not sampled
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Table 5.5-1. Sediment and Porewater Results
Location Latitude Longitude PRM %
solids
Total Hg Sediment
(ng/g dw)
TOC Sediment
(% dry)
Total Hg
Porewater (ng/L)
TOC Porewater
(mg/L)
Fog Creek
62.77542 -148.71762 179.3 78.1 14.1 <0.05 0.58 1.87
62.77553 -148.71740 179.3 80.7 8.59 <0.05 0.54 1.60
62.77583 -148.71697 179.3 82.1 11.8 <0.05 0.55 1.54
Tsusena Creek
62.82242 -148.61498 184.6 79.9 1.71 <0.05 0.82 0.777
62.82315 -148.61578 184.6 79.8 1.75 <0.05 <0.51 0.726
62.82335 -148.61630 184.6 77.9 4.32 0.092 4.49 0.713
Below Dam Site
62.82177 -148.57805 187.1 78.3 5.34 0.141 <0.51 1.7
62.82193 -148.57743 187.1 81.1 5.60 0.188 4.99 8.37
62.82220 -148.57653 187.1 82.3 5.16 0.138 0.73 1.23
Above Dam Site
62.82300 -148.53540 187.3 80.9 17.4 0.072 0.70 3.68
62.82320 -148.53567 187.3 80.0 4.10 0.094 0.99 5.93
62.82317 -148.53640 187.3 80.1 3.73 0.084 1.90 4.54
Deadman Creek
62.82942 -148.47590 189.3 82.6 1.00 <0.05 0.66 1.36
62.82942 -148.47643 189.3 82.0 1.31 <0.05 <0.51 1.37
62.82930 -148.47867 189.3 84.3 1.08 <0.05 0.65 1.14
Watana Creek
62.82923 -148.25803 196.8 80.6 6.86 <0.05 0.63 1.70
62.82943 -148.25895 196.8 77.4 8.49 0.053 <0.51 2.04
62.82953 -148.25927 196.8 80.1 12.1 0.364 <0.51 1.64
Kosina Creek
62.78349 -147.94318 209.1 70.9 13.6 0.215 <0.50 1.92
62.78342 -147.94299 209.1 78.3 2.09 0.058 0.529 1.73
62.78288 -147.94221 209.1 82.8 1.82 0.027 0.814 2.38
Jay Creek
62.77716 -147.88979 211.0 77.5 7.10 0.156 0.527 1.92
62.77729 -147.88992 211.0 75.6 10.1 0.145 0.607 1.73
62.77743 -147.89046 211.0 75.6 14.7 0.145 <0.5 2.38
Goose Creek
62.64403 -147.43614 232.6 72.1 12.2 0.785 1.17 4.53
62.64426 -147.43553 232.6 74.3 8.56 0.144 1.32 4.44
62.64451 -147.43544 232.6 79.4 5.62 0.158 0.886 9.18
Oshetna River
62.63880 -147.38757 235.2 80.5 6.75 0.057 8.69 26.5
62.63852 -147.38806 235.2 85.8 6.59 0.024 9.54 24.9
62.63992 -147.38428 235.2 85.7 5.21 0.046 12.5 1.82
PRM = project river mile. ng/g = nanograms per gram. ng/L = nanograms per liter. mg/L = milligrams per liter. Hg = mercury. TOC = Total organic carbon. dw = dry weight
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Table 5.5-2. Sediment and Porewater Results
Location Latitude Longitude PRM Soil Type Sieve Results (% passing)
#4 #10 #20 #40 #60 #100 #200
Fog Creek
62.77542 -148.71762 179.3 SP 100 100 100 97 61 8 0.8
62.77553 -148.71740 179.3 SP 99 88 53 20 6 1 0.6
62.77583 -148.71697 179.3 SP 96 82 46 7 1 0 0.1
Tsusena Creek
62.82242 -148.61498 184.6 SP 85 73 38 8 2 1 0.8
62.82315 -148.61578 184.6 SP 93 92 70 22 6 2 0.5
62.82335 -148.61630 184.6 SM 100 100 95 82 44 29 15.3
Below Dam Site
62.82177 -148.57805 187.1 SP 100 100 99 71 37 10 0.5
62.82193 -148.57743 187.1 SP 100 100 95 65 33 16 2.3
62.82220 -148.57653 187.1 SP 99 96 88 70 45 21 3.1
Above Dam Site
62.82300 -148.53540 187.3 SP 98 98 91 36 8 3 2.7
62.82320 -148.53567 187.3 SP-SM 100 100 100 98 74 28 6.3
62.82317 -148.53640 187.3 SP 100 100 100 96 66 13 1.4
Deadman Creek
62.82942 -148.47590 189.3 SP 100 99 59 11 2 0 0.2
62.82942 -148.47643 189.3 SP 99 97 78 36 10 2 0.7
62.82930 -148.47867 189.3 SP 84 82 69 26 8 3 1.0
Watana Creek
62.82923 -148.25803 196.8 GP 44 36 27 16 7 3 1.2
62.82943 -148.25895 196.8 SP 100 99 95 80 32 7 1.6
62.82953 -148.25927 196.8 ML 96 95 93 89 83 71 50.5
Kosina Creek
62.78349 -147.94318 209.1 SP-SM 81 77 68 48 30 17 5.2
62.78342 -147.94299 209.1 SP 87 76 48 19 9 6 3.1
62.78288 -147.94221 209.1 SP 66 45 24 12 7 2 0.6
Jay Creek
62.77716 -147.88979 211.0 SM 88 83 78 76 71 55 21.2
62.77729 -147.88992 211.0 SM 99 94 88 80 70 58 28.9
62.77743 -147.89046 211.0 SM 100 100 99 97 95 78 25.7
Goose Creek
62.64403 -147.43614 232.6 SM 92 91 68 71 57 37 16.9
62.64426 -147.43553 232.6 SM 78 73 68 66 64 52 26.5
62.64451 -147.43544 232.6 SP-SM 96 95 81 45 25 15 6.0
Oshetna River
62.63880 -147.38757 235.2 SP 63 46 34 27 14 6 2.8
62.63852 -147.38806 235.2 SW 62 35 23 15 6 2 1.4
62.63992 -147.38428 235.2 GP 40 27 15 8 4 2 1.2
PRM = project river mile.
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Table 5.6-1 Results for Mammal Samples
Mammal % Solids Total Hg (ng/g dw) Total Hg (ng/g ww)
Mink Fur 1 28.22 7,670 2,170
Mink Fur 2 47.23 6,530 2,970
Otter Fur 1 24.48 6,330 1,610
Otter Fur 2 (4 strands) 28.84 NA 417
NA = not analyzed
ng/g = nanograms per gram
dw = dry weight
ww = wet weight
Hg = mercury
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Table 5.7-1. Lake Trout Analytical Results
Drainage Latitude Longitude PRM Sample
Date
Fish
Fork
Length
(mm)
Fish
Weight
(g)
Estimated
Age (yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Sally Lake 62.8381 -148.1907 194.1 8/5/2012 510 1806 14 22.08 912 201 1000 222
430 1082 8 28.66 633 181 631 181
Deadman Lake 63.0076 -148.2364 NA 09/20/13
625 2200 26 21.83 2920 637 2860 624
450 1000 9 25.94 609 158 603 156
460 1000 9 27.29 633 173 548 149
590 1600 22 20.12 2140 431 2140 430
455 800 9 22.63 747 169 907 205
355 1300 6 22.39 612 137 645 145
380 500 7 22.91 592 136 563 129
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram. ww= wet weight. dw = dry weight.
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Table 5.7-2. LNS Analytical Results
Drainage Latitude Longitude PRM Sample
Date
Fish
Length
(mm)
Fish
Weight
(g)
Estimated
Age (yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Oshetna River
62.639 -147.382 235.2 8/13/2013
350 500 9 23.50 295 67.9 313 72.1
430 380 >10 24.15 471 114 420 101
340 370 8 18.00 579 104 546 98.3
315 350 7 22.43 188 42.2 167 37.5
8/14/2013 350 355 9 21.48 640 138 644 138
Upper Susitna 62.834 -148.301 195.5 8/9/2013 320 303 7 22.65 161 36.4 152 34.4
Upper Susitna 62.754 -147.720 217.1 9/12/2013 330 371 8 21.63 153 33.1 137 29.7
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram, ww= wet weight. dw = dry weight
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Table 5.7-3. Dolly Varden Analytical Results
Drainage Latitude Longitude Sample Date Fish
Length
(mm)
Fish
Weight
(g)
Estimated
Age (yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Upper Watana
Creek 62.9107
-147.9714 9/18/2013 187 55 4 23.59 88.3 20.8 82.3 19.0
204 70 4 20.78 120 24.9 107 22.3
-147.8966 10/3/2013 195 64 4 23.33 359 83.7 360 83.9
-147.9349 10/3/2013
194 68 3 24.35 255 62.0 214 52.2
186 57 4 21.94 218 47.9 222 48.6
196 69 4 27.18 172 46.7 139 37.8
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; ww = wet weight; dw = dry weight
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Table 5.7-4. Arctic Grayling Analytical Results
Drainage Latitude Longitude PRM Sample Date Fish
Length
(mm)
Fish
Weight
(g)
Est. Age
(yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Watana Creek 62.9034 -148.1185 194.1 8/11/2012 248 148 4 24.72 78.1 19.3 102 25.1
62.9034 -148.1185 194.1 8/11/2012 340 385 8 26.54 143 38.1 117 31.0
Kosina Creek
62.8921 -148.1365 209.2 6/25/2013 160 102 2 19.76 126 24.9 101 19.9
62.8921 -148.1365 209.2 6/25/2013 225 233 3 21.45 142 30.5 107 22.9
62.8921 -148.1365 209.2 6/25/2013 155 84 1.5 21.38 97.0 20.7 79.6 17.0
62.8921 -148.1365 209.2 6/25/2013 185 125 2.5 19.34 142 27.4 113 21.8
62.8921 -148.1365 209.2 6/25/2013 220 250 2.5 20.99 176 37.1 145 30.4
62.8921 -148.1365 209.2 6/25/2013 180 119 2.5 23.22 125 29.0 86.4 20.1
62.8921 -148.1365 209.2 6/25/2013 170 106 2 21.38 126 27.0 92.0 19.7
62.8921 -148.1365 209.2 6/25/2013 215 221 3 22.68 215 48.8 158 35.8
62.8921 -148.1365 209.2 6/25/2013 215 241 3 22.49 272 61.3 213 47.8
62.8921 -148.1365 209.2 6/25/2013 235 269 4 20.62 185 38.1 159 32.9
62.7827 -147.9417 209.2 8/4/2013 300 300 6 21.87 326 71.4 334 73.1
62.7560 -147.9552 209.2 8/4/2013 330 320 8 20.67 421 87.1 395 81.7
62.7560 -147.9552 209.2 8/4/2013 310 251 7 18.79 533 100 452 84.9
Oshetna River 62.6394 -147.3813 235.2 6/25/2013 75 12 0.5 20.98 180 37.7 139 29.2
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; dw= dry weight; ww = wet weight.
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Table 5.7-5. Burbot Muscle Tissue Analytical Results
Drainage Latitude Longitude PRM Sample
Date
Fish
Length
(mm)
Fish
Weight
(g)
Est.
Age
(yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Upper Susitna
62.8308 -148.4666 186.8 8/5/2012 410 553 5 19.85 200 39.6 207 41.1
62.8346 -148.3017 192.6 8/3/2012 410 553 5 18.56 297 54.7 321 59.5
62.8246 -148.4226 195.3 8/9/2013 443 541 5 22.13 338 74.7 298 66.0
62.8284 -148.3713 193.1 8/28/2013 454 503 5 19.26 311 59.9 239 46.1
62.6966 -147.5645 224.3 8/16/2013 467 470 4 20.72 547 113 474 98.3
62.7528 -147.7208 217.1 8/17/2013 390 362 3.5 20.78 324 67.3 242 50.2
62.7608 -147.7938 214.7 10/4/2013 451 437 4 19.58 513 100 461 90.3
62.7608 -147.7938 214.7 10/4/2013 417 312 3 18.84 498 93.8 423 79.7
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; dw = dry weight; ww = wet weight
Table 5.7-6. Burbot Liver Analytical Results
Drainage Latitude Longitude PRM Sample
Date
Fish
Length
(mm)
Fish
Weight
(g)
Est.
Age
(yr.)
%
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Upper Susitna
62.8246 -148.4226 195.3 8/9/2013 443 541 5 38.72 44.3 17.1 43.5 16.8
62.8284 -148.3713 193.1 8/28/2013 454 503 5 46.39 31.6 14.7 31.1 14.4
62.6966 -147.5645 224.3 8/16/2013 467 470 4 46.97 47.1 22.1 34.4 16.1
62.7528 -147.7208 217.1 8/17/2013 390 362 3.5 30.88 106 32.6 94.0 29.0
62.7608 -147.7938 214.7 10/4/2013 451 437 4 18.39 241 44.2 199 36.6
62.7608 -147.7938 214.7 10/4/2013 417 312 3 17.91 200 35.9 170 30.5
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; dw = dry weight; ww = wet weight
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Table 5.7-7. Slimy Sculpin (Whole Body) Analytical Results
Drainage Latitude Longitude PRM Sample
Date
Fish
Length
(mm)
Fish
Weight
(g)
% Solids THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Upper Susitna
62.7302 -147.6672 219.5 9/12/2013 85 5 24.02 165 39.7 137 33.0
62.7302 -147.6672 219.5 9/12/2013 86 5 22.01 387 85.1 248 54.5
62.7302 -147.6672 219.5 9/12/2013 87 5.3 23.05 158 36.4 102 23.4
62.8006 -148.1006 202.7 9/16/2013 100 6.6 23.81 159 37.9 220 52.3
62.8006 -148.1006 202.7 9/16/2013 87 5.4 22.39 104 23.3 121 27.0
62.8006 -148.1006 202.7 9/16/2013 92 6.9 22.71 125 28.3 117 26.5
62.8330 -148.3018 195.5 9/18/2013 74 3.4 25.71 149 38.3 146 37.5
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; dw = dry weight; ww = wet weight
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Table 5.7-8. Whitefish (sp.) Analytical Results
Drainage Latitude Longitude PRM Sample Date
Fish
Length
(mm)
Fish
Weight
(g)
Est.
Age
(yr.)
%
Total
Solids
THg
(ng/g dw)
THg
(ng/g ww)
MeHg
(ng/g dw)
MeHg
(ng/g ww)
Watana Creek 62.861 -148.200 194.1 8/30/2013 278 155 4 25.54 150 38.3 136 34.8
Upper Susitna
62.826 -148.442 190.7 8/29/2013 309 258 6 24.94 177 44.2 175 43.6
62.730 -147.668 219.5 8/16/2013 450 415 20 26.39 262 69.1 225 59.4
62.775 -147.857 212.3 8/18/2013 372 495 10 30.68 332 102 258 79.3
62.781 -147.922 209.9 8/18/2013 317 310 6 28.56 137 39.2 116 33.2
62.645 -147.405 233.9 9/10/2013 140 256 1 23.40 350 81.8 279 65.4
62.645 -147.405 233.9 9/10/2013 175 263 1.5 26.53 208 55.3 167 44.2
62.645 -147.405 233.9 9/10/2013 342 365 8 27.98 171 47.9 131 36.6
62.782 -148.049 205.1 9/16/2013 355 470 9 27.64 201 55.6 219 60.5
Kosina Creek 62.756 -147.996 209.2 8/14/2013 365b 340 10 23.97 379 90.8 269 64.5
Oshetna River
62.640 -147.383 235.2 8/13/2013 190b 57.1 1 23.95 76.5 18.3 126 30.2
62.640 -147.383 235.2 8/13/2013 340a 370 8 31.74 273 86.6 281 89.2
62.639 -147.381 235.2 6/26/2013 130 55 1 21.10 26.9 5.68 25.2 5.31
All fish are round whitefish with the exception of a (humpback whitefish) and b (whitefish species unknown).
PRM = project river mile; NA = not applicable; mm = millimeters; g = grams; yr. = year; THg = total mercury; MeHg = methylmercury, ng/g = nanograms per gram; dw = dry weight; ww = wet weight
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Table 5.8-1. Predicted Peak MeHg Concentrations in Fish
Species N Predicted peak increase factor
(relative increase)
Current Mean Total
Hg in fish tissue
(ng/g ww)
Predicted Peak Mean
Total Hg in fish tissue
(ng/g ww)
Lake Trout 9 4.25 247 1,047
Arctic Grayling 16 2.75 44 121
Dolly Varden 7 2.75 43 119
Slimy Sculpin 7 2.75 41 114
Round Whitefish 14 2.75 57 157
Burbot 6 4.25 68 289
Longnose Sucker 7 2.75 77 212
Calculation performed using formula from Harris and Hutchison (2008)
MeHg = methylmercury
N = sample number
Hg = mercury
ng/g ww = nanograms per gram wet weight
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Table 5.8-2. Factors that Influence Potential Bioavailability of MeHg
Fate Processes
Affecting Methylation
of Mercury
Evaluating Potential for Bioavailability of Mercury under Existing Conditions Likelihood of Increasing Methylation under Existing
Conditions and Potential for Bioavailability
Low Risk Moderate Risk High Risk
Selenium (in sediment) Presence of selenium in sediments reduce potential for toxic effects of mercury by complexing.
Mercury selenide (HgSe) is formed and reduces toxic effects of mercury, when present.
Selenium is present and in higher concentrations than mercury in sediment. Formation of HgSe is
likely and will reduce potential for bioavailability.
X
Dissolved Oxygen Anaerobic conditions enhance microbial respiration that increases the rate of mercury
methylation. Anaerobic conditions are characterized by low pH and low dissolved oxygen
concentrations.
Oxygen concentrations at the sediment/surface water interface are within water quality standards.
The exception was at a single sample point on Oshetna River.
X
pH Mobilization of mercury from sediments tends to occur in the presence of surface water conditions
with low pH. Adsorption of bioavailable mercury (dissolved) in the water column to organic
particles is minimized under conditions with low pH.
All pH readings at the surface water sediment interface were within water quality standards and
unlikely have an effect on release of mercury from sediments.
X
Temperature Rate of microbial respiration may be enhanced with increased water temperature. Warmer water
temperatures promote lower dissolved oxygen concentrations.
Water temperatures at the sediment/surface water interface were consistently below the water
quality standard at these Upper River sampling sites.
X
Redox Potential Redox potential is primarily a function of oxides or sulfides present in sediments which is, in turn,
a function of the oxygen concentration in the overlying water (Chapman et al. 2003).
Surface water redox potential near the sediment was high at all sample points. The potential for
bioavailable mercury is low under existing conditions.
X
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Table 6.1-1 Mercury in Soil and Vegetation
Media Hg (ng/g, dw)
39 year old stand
Hg (ng/g, dw)
133 year old stand
Hg (ng/g dw)
180 year old stand
Moss 94.5 108 90.6
Aspen leaves NS 8 NS
Spruce needles 9.9 NS NS
Aspen bark NS 15.9 NS
Jack pine bark 38.6 NS NS
Lichen 30.6 74 227.1
Leaf litter 68.3 NS 127.1
Aspen wood NS 2.08 NS
White spruce wood 1.86 NS NS
Organic soil 100-160 120 - 300 160-250
Mineral soil 9.2 8.8 25.2
Hg = mercury
ng/g dw = nanograms per gram dry weight
Information from Friedli et al. 2007
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Table 6.5-1 Mercury SQuiRT Standards in Sediment
NOAA SQuiRT (ng/g) Maximum concentration
Observed on Site (ng/g) Background TEC TEL LEL PEC SEL
4-51 189 174 200 1060 2000 17.4
from NOAA (2015).
TEL = Threshold Effects Level: A chemical concentration in some item (dose) that is ingested by an organism, above which some effect (or response) will be produced and below which it will not. This item is usually food, but
can also be soil, sediment, or surface water that is incidentally (accidentally) ingested as well.
TEC = Threshold Effects Concentration: A concentration in media (surface water, sediment, soil) to which a plant or animal is exposed, above which some effect (or response) will be produced and below which it will not
LEL = Lowest Effect Level. The lowest level of a chemical stressor evaluated in a toxicity test that shows harmful effects on a plant or animal.
PEC = Probable Effects Concentration: The level of a concentration in the media to which a plant or animal is directly exposed that is likely to cause an adverse effect.
PEL= Probable Effects Level: A chemical concentration in some item (dose) prey that is ingested by an organism, which is likely to cause an adverse effect. The ingested item is usually food, but can be soil, sediment, or
surface water that is incidentally (accidentally) ingested.
SEL = Severe Effect Level: is that at which pronounced disturbance of the sediment-dwelling community can be expected. This is the concentration that would be detrimental to the majority of the benthic community.
ng/g = nanograms per gram
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Table 6.8.1. Comparison Between Predicted Peak MeHg Concentrations in Fish
Facility Capacity
(MW)
Area
Flooded
(km2)
Area
Total
(km2)
Mean
Annual Flow
(km3/yr.)
Predicted piscivorous
fish peak increase factor
(times background)
Predicted non-piscivorous
fish increase factor (times
background)
Susitna-Watana 600 86.74 103.38 7.23 4.24 2.77
Bradley Lake 126 10.43 15.46 0.62 4.27 2.99
Solomon Gulch 12 2.08 2.49 0.11 4.81 3.39
Swan Lake 22.4 1.82 6.07 0.39 2.69 1.67
Terror Lake 20 2.99 4.13 0.22 4.18 2.82
MeHg = methylmercury
MW = megawatts
Km2 = square kilometers
Km3 = cubic kilometers
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10. FIGURES
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Figure 3.1. Water Quality Sample Locations
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Figure 4.2-1. Vegetation and Soil Sampling Locations
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Figure 4.2-2. Vegetation and Soil Sample Location: Site 1
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Figure 4.2-3. Vegetation and Soil Sample Location: Site 2
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Figure 4.2-4. Vegetation and Soil Sample Location: Site 3
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Figure 4.2-5. Vegetation and Soil Sample Location: Site 4
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Figure 4.2-6. Vegetation and Soil Sample Location: Site 5
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Figure 4.2-7. Vegetation and Soil Sample Location: Site 6
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Figure 4.2-8. Vegetation and Soil Sample Location: Site 7
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Figure 4.2-9. Vegetation and Soil Sample Location: Site 8
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Figure 4.2-10. Vegetation and Soil Sample Location: Site 9
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Figure 4.2-11. Vegetation and Soil Sample Location: Site 10
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Figure 4.2-12. Focus Area Sampling Location Overview
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Figure 4.2-13. Example Detail of Focus Area 104: Whiskers Slough
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Figure 4.2-14. Detail of Focus Area 113: Oxbow I.
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Figure 4.2-15. Detail of Focus Area 115: Slough 6A.
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Figure 4.2-16. Detail of Focus Area 128: Slough 8A.
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Figure 4.2-17. Detail of Focus Area 138: Gold Creek.
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Figure 4.2-18. Detail of Focus Area 141: Indian River.
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Figure 4.2-19. Detail of Focus Area 144: Side Channel 21.
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Figure 4.2-20. Map of Sediment/Porewater Sampling Locations
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Figure 4.2-21. Sediment and Porewater Sample Locations for Goose and Jay Creeks
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Figure 4.2-22. Sediment and Porewater Sample Locations for Kosina Creek and Oshetna River
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Figure 4.2-23. Sediment and Porewater Sample Locations for Above and Below Dam Site
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Figure 4.2-24. Sediment and Porewater Sample Locations for Watana and Tsusena Creeks
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Figure 4.2-25. Sediment and Porewater Sample Locations for Deadman and Fog Creeks
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Figure 4.2-26. Fish Tissue Sample Collection Locations
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Figure 5.1-1. ADEC Fish Tissue Sample Collection Locations
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Figure 5.1-2. USGS (Frenzel 2000) Sample Locations
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Figure 5.4-1. Total Mercury by Location in Mainstem Susitna River
Figure 5.4-2. Total Mercury over Time at Susitna Station (PRM 29.9)
0
5
10
15
20
25
0 50 100 150 200 250Mean Total Hg (ng/L)PRM
Jun-14 Sep-14
Susitna Station
Watana Dam site
0
5
10
15
20
25
30
35
May-13 Aug-13 Nov-13 Mar-14 Jun-14 Sep-14 Dec-14Total Hg (ng/L)Total Mercury Concentration
Above Yentna River
Oshetna River
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Figure 5.6-1. Sample Locations for Piscivorous Mammals
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Figure 5.7-1. Lake Trout Fork Length and Age
From Burr (1987) and this study
Figure 5.7-2. Lake Trout Fork Length and Total Hg (dw)
0
100
200
300
400
500
600
700
800
900
1000
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Fork length (mm)Age (years)
Various Susitna Drainage Lakes (1966)
Deadman Lake (1966)
Deadman Lake (2013)
0
500
1000
1500
2000
2500
3000
3500
300 350 400 450 500 550 600 650Total Hg (ng/g dw)Fork Length (mm)
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Figure 5.7-3. LNS Fork Length and Age
Susitna Middle River Data from APA (1984b)
Figure 5.7-4. LNS Fork Length and Total Hg (dw)
0
100
200
300
400
500
0 1 2 3 4 5 6 7 8 9 10 11 12 13Fork length (mm)Age of Fish (years)
LNS Susitna Middle River (1980s)
LNS Upper Susitna (This Study)
0
100
200
300
400
500
600
700
250 270 290 310 330 350 370 390 410 430 450Total Hg (ng/g dw)Fork Length (mm)
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Figure 5.7-5. Dolly Varden Fork Length and Total Hg (dw)
Figure 5.7-6. Arctic Grayling Fork Length and Age in the Upper Susitna
Susitna Middle River Data from APA (1984a)
0
50
100
150
200
250
300
350
400
175 180 185 190 195 200 205 210Total Hg (ng/g dw)Fish Fork Length (mm)
0
50
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12 14Fork length (mm)Age (years)
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Figure 5.7-7. Arctic Grayling Fork Length and Total Hg (dw)
Figure 5.7-8. Burbot Fork Length and Total Hg (dw)
0
100
200
300
400
500
600
50 100 150 200 250 300 350 400Total Hg (ng/g dw)Fish fork length (mm)
0
100
200
300
400
500
600
380 390 400 410 420 430 440 450 460 470 480Total Hg (ng/g dw)Fork Length (mm)
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Figure 5.7-9. Slimy Sculpin Fork Length and Total Hg (dw)
Figure 5.7-10. Round Whitefish Fork Length and Age
Susitna Middle River Data from APA (1984b)
0
50
100
150
200
250
300
350
400
450
60 65 70 75 80 85 90 95 100 105Total Hg (ng/g dw)Fork Length (mm)
0
50
100
150
200
250
300
350
400
0 1 2 3 4 5 6 7 8 9 10 11 12Fork length (mm)Age of Fish (years)
Susitna Middle River
This Study
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Figure 5.7-11. Round Whitefish Fork Length and Total Hg (dw)
0
20
40
60
80
100
120
100 150 200 250 300 350 400 450 500Total Hg (ng/g dw)Fork length (mm)
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Figure 5.8-1. Factors that Effect Mercury Bioconcentration and Bioaccumulation.
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Figure 5.8-2. Potential Mercury Processes Under Existing Conditions.
Figure 5.8-3. Sediment Mercury Concentrations Under Existing Conditions
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Sediment Mercury (ng/g)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3
SQuiRT:Threshold Effects Level = 174 ng/g
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Figure 5.8-4. Porewater Mercury Concentrations Under Existing Conditions.
Figure 5.8-5. Sediment Selenium Concentrations Under Existing Conditions.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Porewater Dissolved Mercury (ng/L)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Sediment Selenium (mg/kg)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3
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Figure 5.8-6. Surface Water pH Conditions at Sediment Interface Under Existing Conditions.
Figure 5.8-7. Surface Water Temperature Conditions at Sediment Interface Under Existing Conditions.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
pHSample Pt. 1 Sample Pt. 2 Sample Pt. 3
Water Quality
Criteria 6.5 -8.5 pH
units
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
Temperature (°C)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3
Water Quality Criteria
13°C - 20°C
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Figure 5.8-8. Surface Water Dissolved Oxygen Concentrations at Sediment Interface Under Existing
Conditions.
Figure 5.8-9. Surface Water Reduction/Oxidation Potential at the Sediment Interface Under Existing
Conditions.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
Dissolved Oxygen (mg/L)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3 Series4 Series5
Water Quality
Criteria ≥ 7.0 and ≤
17.0
0
50
100
150
200
250
300
350
400
450
500
ORP (mV)Sample Pt. 1 Sample Pt. 2 Sample Pt. 3
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Figure 6.7-1. Comparison Between Fish Age and Mercury Concentrations.
Figure 6.7-2. Arctic Grayling Mean Size and Total Hg Comparison.
Data from this study (green markers), as well as ADEC (2012); Jewett et al (2003); Gray et al (1996); Mueller and Matz (2002);
Mueller et al. (1993); and Snyder-Conn et al. (1993)r
0
100
200
300
400
500
600
700
0 5 10 15 20 25 30Total Hg (ng/g dw)Age (yrs.)
Lake trout Arctic Grayling Whitefish (sp.)
Watana Creek
Kosina Creek
Oshetna River
Lake Loise
Lakes near Tyone
Creek
Finger Lake
Fishhook Lake Upper Talkeetna
River
Christianson Lake
Yukon River
(Andreafsky R.)
Kuskokwim River
(Geroge R.)
SW Alaska (8 rivers)
Innoko NWR
Selawik NWR
Nowita NWR
Kanuti NWR
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350 400 450 500Mean Total Hg (ng/g ww)Mean size of fish (g)