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Susitna-Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
SuWa 249
Mercury assessment and potential for bioaccumulation study (Study 5.7),
evaluation of continued mercury monitoring beyond 2014, technical
memorandum
Author(s) – Personal:
Author(s) – Corporate:
Tetra Tech
AEA-identified category, if specified:
September 30, 2014 technical memorandum filings
AEA-identified series, if specified:
Series (ARLIS-assigned report number): Existing numbers on document:
Susitna-Watana Hydroelectric Project document number 249
Published by: Date published:
[Anchorage, Alaska] : Alaska Energy Authority, [2014] September 2014
Published for: Date or date range of report: Alaska Energy Authority
Volume and/or Part numbers:
Final or Draft status, as indicated:
Attachment B
Revised
Document type: Pagination:
Technical memorandum ii, 13 p.
Related work(s): Pages added/changed by ARLIS:
Cover letter to this report: Susitna-Watana Hydroelectric Project,
FERC Project no. 14241-000; Third set of 2014 technical
memoranda for Initial Study Plan meeting. (SuWa 247)
Attachments A (SuWa 248) and C-F (SuWa 250-253)
Added cover letter (3 pages)
Notes:
"(revised per errata November 14, 2014)."
This entire document was replaced in November 2014 by replacement pages are found on pages 3
to 18 of Mercury assessment and potential for bioaccumulation study (Study 5.7), Errata to
evaluation of continued mercury monitoring beyond 2014, technical memorandum (September 30,
2014) (SuWa 268), which is Attachment N to Susitna-Watana Hydroelectric Project, Project no.
14241-000; Filing of Initial Study Plan meetings transcripts and additional information in response
to October 2014 Initial Study Plan meetings (SuWa 254).
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/
September 30, 2014
Ms. Kimberly D. Bose
Secretary
Federal Energy Regulatory Commission
888 First Street, N.E.
Washington, D.C. 20426
Re: Susitna-Watana Hydroelectric Project, Project No. 14241-000
Third Set of 2014 Technical Memoranda for Initial Study Plan Meetings
Dear Secretary Bose:
As the Alaska Energy Authority (AEA) explained in its September 17, 2014 filing
with the Federal Energy Regulatory Commission (Commission or FERC) for the
proposed Susitna-Watana Hydroelectric Project, FERC Project No. 14241 (Project), the
June 3, 2014 Initial Study Report (ISR) provided for AEA to prepare certain technical
memoranda and other information based on 2014 work. In accordance with Commission
Staff direction, on September 17 and September 26, AEA filed and distributed the first
and second sets of technical memoranda and other information generated during the 2014
study season.
With this letter, AEA is filing and distributing the third set of technical
memoranda generated during the 2014 study season, as described below.
This third set of technical memoranda includes:
• Attachment A: Baseline Water Quality Study (Study 5.5) and Water Quality
Modeling Study (Study 5.6), Water Quality and Lower River Modeling
Technical Memorandum. This technical memorandum evaluates water quality
data collected during 2013 and 2014 for adequacy in representation of current
riverine conditions. This Technical Memorandum further includes an
assessment of whether to extend the Water Quality Modeling Study’s riverine
model below PRM 29.9.
• Attachment B: Mercury Assessment and Potential for Bioaccumulation Study
(Study 5.7), Evaluation of Continued Mercury Monitoring Beyond 2014
Technical Memorandum. This technical memorandum evaluates the need for
continued monitoring of mercury data beyond 2014 and whether the existing
data collection efforts are sufficient to satisfy objectives for characterizing
baseline mercury conditions in the Susitna River and tributaries (Revised
Study Plan (RSP) Section 5.7.1).
2
• Attachment C: Groundwater Study (Study 7.5), Preliminary Groundwater and
Surface-Water Relationships in Lateral Aquatic Habitats within Focus Areas
FA-128 (Slough 8A) and FA-138 (Gold Creek) in the Middle Susitna River
Technical Memorandum. This technical memorandum provides an overview
of the types of data and information that are being collected to support the
Task 6 activities of the Groundwater Study, and describes the methods and
techniques that are being applied in analyzing the data leading to development
of response functions to be used for evaluating Project operational
effects. The TM centers on the analysis for FA-128 (Slough 8A) and to a
lesser extent FA-138 (Gold Creek) and represents an expansion of the
presentation materials provided during the Proof of Concept meetings held on
April 15-17, 2014.
• Attachment D: Groundwater Study (Study 7.5), Groundwater and Surface-
Water Relationships in Support of Riparian Vegetation Modeling Technical
Memorandum. This technical memorandum provides an overview of the
types of data and information that are being collected to support the Task 5
activities within the Groundwater Study, and describes the methods and
techniques that are being applied in analyzing the data leading to development
of response functions for evaluating Project operational effects. The TM
provides analysis objectives for FA-115 (Slough 6A) as a primary example of
upland versus riverine dominated groundwater conditions. Additional
examples are shown for FA-128 (Slough 8A) and FA-138 (Gold Creek).
• Attachment E: Salmon Escapement Study (Study 9.7), 2014 Implementation
and Preliminary Results Technical Memorandum. This technical
memorandum describes 2014 implementation (including methods and
variances) of and preliminary results from the Salmon Escapement Study.
• Attachment F: Cook Inlet Beluga Whale Study Plan (Study 9.17), 2015
Implementation Plan Technical Memorandum. This implementation plan
describes the methods for study activities proposed for 2015 that would
implement the Cook Inlet Beluga Whale Study (instead of those described in
RSP Section 9.17.1).
AEA appreciates the opportunity to provide this additional information to the
Commission and licensing participants, which it believes will be helpful in determining
the appropriate development of the 2015 study plan as set forth in the ISR. If you have
questions concerning this submission please contact me at wdyok@aidea.org or (907)
771-3955.
3
Sincerely,
Wayne Dyok
Project Manager
Alaska Energy Authority
Attachments
cc: Distribution List (w/o Attachments)
Attachment B
Mercury Assessment and Potential for Bioaccumulation Study (Study 5.7), Evaluation of
Continued Mercury Monitoring Beyond 2014 Technical Memorandum
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Mercury Assessment and Potential for Bioaccumulation
Study (Study 5.7)
Evaluation of Continued Mercury Monitoring Beyond 2014
Technical Memorandum
Prepared for
Alaska Energy Authority
Prepared by
Tetra Tech
September 2014
(revised per errata November 14, 2014)
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
TABLE OF CONTENTS
1. INTRODUCTION ............................................................................................................................... 1
2. STUDY OBJECTIVES ....................................................................................................................... 1
3. STUDY AREA ..................................................................................................................................... 2
4. ELEMENTS REQUIRED TO COMPLETE THE STUDY ........................................................... 2
4.1 Planned Monitoring Components in 2014 .................................................................................... 3
5. STUDY COMPONENTS COMPLETED IN 2014 .......................................................................... 3
5.1 Geologic Studies for the Inundation Zone .................................................................................... 3
5.2 Collection of Sediment and Porewater Samples ........................................................................... 3
5.3 Limited Winter Water Quality Sampling ...................................................................................... 4
5.4 Summer Monthly Sampling .......................................................................................................... 4
6. APPROACH FOR STUDY COMPLETION ................................................................................... 4
6.1 Pathway and Threshold Analyses ................................................................................................. 4
6.1.1 Data Applied to Pathways Analysis ...................................................................................... 5
6.1.2 Application of the Pathway Model ....................................................................................... 5
6.2 Comparison to Existing Criteria and Thresholds .......................................................................... 6
7. STEPS TO COMPLETE THE STUDY ............................................................................................ 7
7.1 Data Verification/Validation ......................................................................................................... 7
8. RECOMMENDATIONS .................................................................................................................... 7
9. REFERENCES .................................................................................................................................... 8
10. FIGURES ............................................................................................................................................. 9
11. TABLES ............................................................................................................................................. 12
LIST OF FIGURES
Figure 1-1. Factors in the Environment that Effect Mercury Bioconcentration and Bioaccumulation. ...... 9
Figure 1-2. Potential Mercury in a Mature Reservoir. ............................................................................... 10
Figure 5.5-1. Average 2013 Mercury Concentrations and Pathways for Transfer of Mercury in the
Susitna Basin. ..................................................................................................................................... 11
LIST OF TABLES
Table 5.3-1. 2014 Winter Sampling at Baseline Water Quality Monitoring Sites and Parameters. .......... 12
Table 5.3-2. 2014 Winter Sampling at Groundwater Well Monitoring Sites in Select Focus Areas. ........ 12
Table 6.2-1. Concentrations of Mercury Compared to Criteria or Thresholds. ......................................... 13
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
LIST OF ACRONYMS, ABBREVIATIONS, AND DEFINITIONS
Abbreviation Definition
ADEC Alaska Department of Environmental Conservation
AEA Alaska Energy Authority
AWQS Alaska Water Quality Standards
FA(s) Focus Area(s)
FERC Federal Energy Regulatory Commission
ILP Integrated Licensing Process
MeHg Methylmercury
NOAA National Oceanic and Atmospheric Administration
NTU Nephelometric turbidity unit
PRM Project River Mile
Project Susitna-Watana Hydroelectric Project
RSP Revised Study Plan
SQuiRT(s) Screening Quick Reference Table(s)
TEL Threshold Effects Level
USACE U.S. Army Corps of Engineers
USGS U.S. Geological Survey
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page ii September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
1. INTRODUCTION
The Alaska Energy Authority (AEA) is preparing a License Application that will be submitted to
the Federal Energy Regulatory Commission (FERC) for the Susitna-Watana Hydroelectric
Project (Project) using the Integrated Licensing Process (ILP). The Project is located on the
Susitna River, an approximately 320-mile-long river in Southcentral Alaska. The Project’s dam
site would be located at Project River Mile (PRM) 187.1.
Mercury contamination is widely known to present human health concerns. In the environment,
processes such as reducing and low oxygen conditions can lead to increased rates of mercury
methylation (Figure 1-1). Based on several studies, mercury that is found in newly formed
reservoirs originates predominantly from inundation of organic soils (Figure 1-2). The linkage
between sediment sources, mobilization into the water column (dissolved form), and the
potential for bioaccumulation in fish tissue and piscivores therefore presents a human health
concern with respect to mercury contamination. Methylmercury (MeHg) bioaccumulates, and the
highest concentrations are typically in the muscle tissue of adult predatory fish. Targeting adult
fish is a good way of monitoring methylmercury migration to the larger environment. Potential
for bioaccumulation in aquatic life is determined when chronic thresholds for toxics exposure in
a medium are identified. Potential for mortality is determined when acute criteria for toxics in a
medium are exceeded.
A Mercury and Potential for Bioaccumulation Study (Study 5.7) was initiated in 2013 to answer
key questions (Revised Study Plan [RSP] Section 5.7.1; AEA 2012) and determine: 1) whether
conditions within the reservoir will cause mercury methylation from inundated conditions, 2) the
concentrations of methylmercury that might occur, and 3) whether a mechanism exists to transfer
that methylmercury to wildlife, resulting in detrimental impacts.
Data on the mercury concentration in sediment, sediment porewater, soil, vegetation, water, fish,
and piscivorous mammals have been collected within the past two years (2013/2014) within the
Susitna River basin. These data were further evaluated for adequacy in representation of current
conditions in and around the Susitna River. The need for continued monitoring of mercury data
beyond 2014 is being evaluated to determine whether the existing data collection efforts are
sufficient to satisfy objectives for characterizing baseline mercury conditions in the Susitna River
and tributaries (RSP Section 5.7.1).
2. STUDY OBJECTIVES
Based on several studies, the mercury that is found in newly formed reservoirs originates
predominantly from inundation of organic soils. Receptors are and will be present in the
inundation area (macroinvertebrates, fish, birds, etc.). Mercury methylation in reservoirs is a
fairly well understood process, and numerous models exist to predict the occurrence and
magnitude of the phenomena.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 1 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
Given these known factors, key questions that need to be answered by this study include the
following:
1) Whether conditions within the reservoir will cause mercury methylation from this source.
2) The concentrations of methylmercury that might occur.
3) Whether a mechanism exists (fish and small invertebrates living in the methylation zone)
to transfer that methylmercury to wildlife, resulting in detrimental impacts.
Study 5.7 assesses the status of mercury concentrations in several media and mercury cycling
between the aquatic and terrestrial environment. Based on these questions, specific objectives of
Study 5.7 study are as follows:
• Summarize available and historic water quality 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.
This information will be used to develop maps of where mercury methylation may occur.
• Use the water quality model to predict where in the reservoir conditions (pH, dissolved
oxygen, turnover) are likely to be conducive to methylmercury formation.
• Use modeling to estimate methylmercury concentrations in fish.
• Assess potential pathways for methylmercury 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. An overview map and
detailed sample locations are provided in the Initial Study Report (ISR) (AEA 2014).
4. ELEMENTS REQUIRED TO COMPLETE THE STUDY
AEA initiated the Mercury Assessment of Potential for Bioaccumulation Study in 2013. To meet
study goals, AEA completed numerous study components which are summarized in ISR Study
5.7 Section 5. The following sections describe study components planned for 2014.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 2 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
4.1 Planned Monitoring Components in 2014
AEA summarized its plans for completing the Mercury Assessment and Potential for
Bioaccumulation Study in ISR Study 5.7, Part C, Section 7 as follows:
• Geologic studies for the inundation zone.
• Collection of sediment samples at the six remaining sites located on CIRWG lands (RSP
Section 5.7.4.2.4).
• Limited winter water quality sampling in January and March of 2014 (RSP Section
5.7.4.2.3).
• Summer monthly water sampling from June to September 2014 (see ISR Section 5.5 for
details).
• Completion of the Predictive Risk Analyses (RSP Section 5.7.4.6) and mercury modeling
(RSP Sections 5.7.4.7 and 5.7.4.8).
5. STUDY COMPONENTS COMPLETED IN 2014
The 2014 efforts focused on the collection of water and sediment mercury and methylmercury to
aid in the creation of a pathways analysis model used to determine the need for further mercury
sampling in other media. Specific study components completed in 2014 are summarized below.
5.1 Geologic Studies for the Inundation Zone
The ISR Study 4.5, Part C Section 7.2 states the following elements and 2015 schedule for
geologic mapping of the area to be inundated by the reservoir:
Geologic Mapping – summer mapping to be scheduled prior to leaf-out and after leaves have
fallen (May and September) for geologic mapping associated with regional geology
development, mineral resources and claims, reservoir rim stability, and a continuation of
geologic mapping as needed for lineaments and geologic features (potential fracture and shear
zones) and evaluation of rock displacement or rupture in the dam site area.
Results from this geologic characterization of the inundated land will be used to determine
potential for mobilization of mercury in the reservoir. This study is on-going and is not yet
completed.
5.2 Collection of Sediment and Porewater Samples
Sediment and porewater samples were collected at the six remaining sites located on CIRWG
lands (RSP Section 5.7.4.2.4) in 2014: Susitna River just below and above the proposed dam site,
and the mouths of Fog, Tsusena, Deadman, and Watana Creeks (Section 5.5.4.6 of the RSP;
Section 4.5 of the ISR).
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 3 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
5.3 Limited Winter Water Quality Sampling
Winter samples were collected from five baseline monitoring sites in January 2014 and March
2014 (Table 5.3-1). Field parameters were collected on-site during each visit and laboratory
parameters generated following analysis of samples. Laboratory data from 2014 winter sampling
has been completed and is now undergoing a quality assurance review. The procedure for a
quality assurance review includes development of a Data Validation/Verification Report (DVR)
for ten percent of all samples collected for this winter monitoring program. The DVR is a data
review requirement of ADEC to ensure compliance with use of high quality data used to make
regulatory decisions.
Three groundwater wells previously established in Focus Areas FA-104 (Whiskers Slough), FA-
128 (Slough 8A), and FA-138 (Gold Creek) were sampled in February 2014, March 2014, and
April 2014 (Table 5.3-2). Both field and laboratory parameter results were generated on three
separate sampling dates. Raw data is currently being reviewed to assure it meets acceptance
limits per the Quality Assurance Project Plan for Water Quality and Mercury Assessment for the
Susitna-Watana Hydroelectric Project Susitna River, Southcentral Alaska (QAPP).
5.4 Summer Monthly Sampling
Total mercury samples were collected from baseline water quality and seven Focus Area (FA)
transects identified in ISR Study 5.7 Sections 4.3 and 4.4, respectively, from June to September
2014. Total mercury samples were collected from one location on a transect at each of the
baseline water quality sites. Total mercury samples were also collected from each transect within
seven Focus Areas (Table 5.4-1). If a transect within a Focus Area crossed braided channels
then one total mercury sample was collected from the mainstem and another from the braided
channel area. A single fur sample was collected outside the inundation area and was the only
sample gathered during the 2014 field studies.
6. APPROACH FOR STUDY COMPLETION
6.1 Pathway and Threshold Analyses
An illustrative pathway model was constructed that reports concentrations of total, dissolved, and
methylmercury measured in various receptors in the Susitna River drainage (Figure 5.5-1) and
describes a preliminary evaluation of potential transfer between media (e.g., sediment– sediment
porewater, porewater–surface water, surface water–fish tissue). A final analysis of potential for
mercury bioaccumulation will combine evaluation of criteria or threshold exceedance and if
these concentrations promote transfer between connected components of the pathway (Figure 1-
2) model. An additional diagram as seen in Figure 1-2 will be constructed for the new reservoir
and include wetlands, bogs, and terrestrial vegetation that will be submerged by inundation.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 4 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
6.1.1 Data Applied to Pathways Analysis
Data used to construct the pathway model were primarily based on data collected in 2013 that
have undergone QA/QC review. Presence of mercury in each of the media sampled and
analyzed is identified and used to determine if a concentration gradient is present (e.g., potential
for transfer from sediment to porewater, porewater to surface water, and sediment to biota).
Evaluation for adequacy of data used in pathways analysis was based on factors like
completeness in sampling all media, determination for adequacy of number of samples collected
in each media, and spatial representation of the sampled media.
Fourteen sediment and sediment porewater samples were analyzed for total mercury in 2013 and
used in the preliminary pathways assessment. Fish sample collection occurred in August through
October 2013. Liver samples were also collected from burbot and analyzed for total mercury and
MeHg. A single fur sample collected from mink and otter outside the Project area was collected
in March 2014 and analyzed for total mercury. A total of 50 soil and vegetation samples from
five sites in each of ten locations within the reservoir inundation zone were collected during
August 2013. Vegetation and soil samples were analyzed for total mercury and MeHg. Each soil
and vegetation sample was analyzed for concentrations of mercury in wet samples and dry
weight results were calculated. In all cases dry weight sample concentrations (calculated values)
exceeded wet weight sample concentrations. Dry weight sample concentration results were used
in the current mercury conceptual pathway assessment.
6.1.2 Application of the Pathway Model
The initial approach used to assess mercury data from various media was to compare data with
existing and appropriate water quality criteria, sediment thresholds, and fish tissue screening
levels. Surface water results were compared to Alaska Water Quality Standards (18 ACC
70.020(b)) for protection of beneficial uses in fresh water and to criteria for protection of human
health. Sediment and fish tissue results were compared to the Screening Quick Reference Tables
(SQuiRTs) used by the National Oceanic and Atmospheric Administration (NOAA) to determine
if the threshold effects level (TEL) to aquatic life have been exceeded. Table 6.1-1 summarizes
the concentrations of mercury compared to criteria or thresholds, including human health as well
as criteria for protection of aquatic life.
Based on discussion provided in Section 5.7.2 of the RSP, naturally occurring deposits of
mercury may occur as parent geology for this element; for example, diorite and granodiorite
have been identified in the proposed inundation zone. Given the limited presence of small-scale
mining in the Project area other sources of mercury could be associated with atmospheric
deposition. Lakes at Glacier Bay, Alaska, have shown that current rates of atmospheric mercury
deposition are almost double the concentration currently than observed during pre-industrial
times (Engstrom and Swain 1997). The presence of mercury in organic rich soils from decades
of post-industrial deposition could be the only source of this element in the inundation zone.
Vegetation samples collected from the area provide some indication of intensity of aerial
deposition based on comparison with concentrations of mercury with known sources of this
element.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 5 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
6.2 Comparison to Existing Criteria and Thresholds
Preliminary examination of 2013 mercury results included a review from each of the media
sampled in both the aquatic and terrestrial environment. Comparison of results with criteria or
effects thresholds was one of the evaluation tools used to review results of mercury
concentrations in each of the media. Table 6.1-1 presents the maximum and minimum
concentrations from observations in each of the sampled media during 2013 and compares the
maximum concentrations with available criteria or thresholds. Comparison to maximum
concentrations is the most conservative approach for determining potential risk of effects from
high mercury concentrations. When the maximum mercury concentration exceeded the criterion,
further examination for how many results exceeded and if most results were near the minimum
concentration as reflected by the average concentration.
Of the 375 samples collected as part of the water quality baseline monitoring study in 2013 were
analyzed for total and dissolved mercury. The Focus Areas had a higher density of sampling
locations, so that prediction of change using the EFDC water quality model could be made with a
higher degree of resolution under Project operations during wet, dry, and average years. Grab
samples collected from the Focus Areas were analyzed for total mercury and methylmercury
generating 300 results. Focus Area water quality mercury sampling results have been compared
with state criteria and thresholds for protection of beneficial uses to evaluate how Project
operations will affect potential fish spawning and rearing habitat.
Based on 2013 sampling results, the average concentration of dissolved mercury in the water
column was 1.06 ng/L (Figure 5.5-1). This average is below the most stringent criterion, of 12
ng/L that is protective of aquatic life. Two dissolved mercury samples collected in June 2013
(from PRM 59.9) and July 2013 (PRM 33.6) exceeded the Human Health criterion of 50 ng/L at
58.7 and 56.4 ng/L, respectively (Table 6.1-1). The remainder of results were well below the
Human Health criterion. Comparison of total mercury concentrations were not compared to the
criterion for protection of aquatic life as results from 2013 did not pass acceptance limits. These
results will be compared against criteria once examination of the 2014 data set is made and
adjustments to 2013 results using a correction factor. Similarly, one mercury result (220 ng/g)
from 14 sediment samples exceeded the recommended SQuiRT Threshold of 174 ng/g.
Concentrations were much lower in the remainder; the overall average mercury concentration in
the sediment samples was 23.01 ng/g.
Background information for mercury in fish tissue was acquired from recent fish tissue analysis
by ADEC with results ranging from 29.07ng/g (total mercury in Sockeye salmon) – 380.0 ng/g
(total mercury in lake trout) in the Susitna Drainage (ADEC 2012). The average concentration
among several species of fish sampled in 2013 from the Susitna drainage was within the range
described by ADEC. Data collected in 2013 was similar to results collected by the 2012 ADEC
effort.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 6 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
7. STEPS TO COMPLETE THE STUDY
7.1 Data Verification/Validation
Revised Study Plan (RSP) Section 5.7.4.2.3 (AEA 2012) stated that AEA would recommend the
need for continuing surface water sampling for mercury in 2014 based on 2013 results. Total
mercury sample results collected in 2013; however, did not meet QA/QC requirement acceptance
limits specified in the QAPP. The review of 2014 sample results will be completed by December
2014 to determine if total mercury estimates in surface water, sediment, and pore water satisfies
acceptance limits and can be used for further data analysis and interpretation. Because ingestion
rates of mercury in piscivores is directly correlated with fish, a determination for potential for
bioaccumulation must initially be completed for aquatic receptors. Identifying a potential source
of mercury from fish (see Section 5.7.4.2 of the RSP) in the Project area must occur before any
conclusions can be made regarding transfer from aquatic to terrestrial receptors. This will be
completed when pathways analysis begins following review of the 2014 data results.
8. RECOMMENDATIONS
Based on results from 2013 sampling, the total mercury concentrations for 2013 from water
column samples are considered high estimates as results did not meet acceptance limits for
laboratory performance. A correction factor will be developed for the 2013 results following
QA/QC review of 2014 data. The concentrations of total mercury in sediments from four sites
that were collected in 2013 are well below SQuiRT TEL and the concentration of total mercury
in sediment porewater (Total Hg) is several times lower than the water column concentration.
The final pathway analysis has not yet been completed and is the next major component of this
study that will determine potential sources for bioaccumulation. Existing fish data collection and
tissue results will be used to identify these potential sources from several media where contact or
ingestion of mercury is possible. Pathways analysis will be used to determine if reservoir and
riverine habitat have the potential for generating methylmercury by using predicted elements
from the Environmental Fluid Dynamic Code (EFDC) model that are known to facilitate the
genesis of methylmercury (Figure 1-1). Post-reservoir conditions will establish potential sources
and location of predicted methylmercury concentrations and the subsequent potential for
bioaccumulation.
Based upon its preliminary review of the mercury results measured in each of the media, AEA is
not proposing any additional sampling for mercury in 2015. Most of the observations
characterizing mercury in each of the media were below existing thresholds or criteria.
Monitoring would be expanded (as stated in Section 5.5.4.4 of the RSP) if metals in surface
water, fish tissue, or sediment exceeded criteria or thresholds. Most of the mercury results in
select media did not exceed available criteria/thresholds, therefore, suggesting no additional
sampling is necessary.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 7 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
9. REFERENCES
ADEC (Alaska Department of Environmental Conservation). 2012. Mercury concentration in
fresh water fish Southcentral Susitna Watershed. Personal communication with Bob
Gerlach, VMD, State Veterinarian. June 2012.
AEA (Alaska Energy Authority). 2012. Revised Study Plan: Susitna-Watana Hydroelectric
Project FERC Project No. 14241. December 2012. Prepared for the Federal Energy
Regulatory Commission by the Alaska Energy Authority, Anchorage, Alaska.
http://www.susitna-watanahydro.org/study-plan.
AEA (Alaska Energy Authority). 2014. Mercury Assessment and Potential for Bioaccumulation
Study, Study Plan Section 5.7. Initial Study Report. June 2014. http://www.susitna-
watanahydro.org/wp-content/uploads/2014/05/05.7_MERC_ISR_PartA.pdf
Engstrom, D.R. and E.B. Swain. 1997. Recent declines in atmospheric mercury deposition in
the Upper Midwest: Environmental Science and Technology, v.31, no.4. p. 960-967.
Frenzel, S.A. 2000. Selected Organic Compounds and Trace Elements in Streambed Sediments
and Fish Tissues, Cook Inlet Basin, Alaska. USGS Water-Resources Investigations
Report 00-4004.
Jewett S.C. and L.K. Duffy. 2007. Mercury in Fishes of Alaska, with emphasis on subsistence
species. Sci. Total Envir. 387(1-3): 3-27.
USGS (U.S. Geological Survey). 2012. Streamflow Record Extension for Selected Streams in
the Susitna River Basin, Alaska, Scientific Investigations Report 2012–5210. 46 p.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 8 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
10. FIGURES
Figure 1-1. Factors in the Environment that Effect Mercury Bioconcentration and Bioaccumulation.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 9 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
Figure 1-2. Potential Mercury in a Mature Reservoir.
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 10 September 2014
TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
Figure 5.5-1. Average 2013 Mercury Concentrations and Pathways for Transfer of Mercury in the Susitna Basin.
Mercury Pathways Analysis
Sediment Hg = 23.01 ng/g
Porewater Total Hg= 2.67 ng/L
Water Column Dissolved Hg= 1.06 ng/L
Water Column Total Hg= 25.55 ng/L
(Provisional Data; Under Review)
Dry soil Hg = 60.46 ng/g
Dry Soil MeHg =0 .61 ng/g
Dry Organic Matter Hg= 58.25 ng/g
Dry Vegetation Hg= 9.16 ng/g
Dry Vegetation MeHg= 3.17 ng/g
Dry Fish Hg= 354.23 ng/g
Fish MeHg= 328.69 ng/g
Dry Mink Fur Hg = 6,258 ng/g (4 samples)
Dry Otter Fur Hg = NA (1 sample)
(Note: Not in study area)
Allocthonous Input Susitna-Watana Hydroelectric Project Alaska Energy Authority
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TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
11. TABLES
Table 5.3-1. 2014 Winter Sampling at Baseline Water Quality Monitoring Sites and Parameters.
Winter Baseline Water Quality Monitoring
Sampling Date Susitna River PRM Lab Parameters Field Parameters
1/28/2014 29.9, 87.8 TP, SRP, Ammonia, NO3+NO2, TKN,
MeHg, Alkalinity, Hardness, TDS, TSS,
TOC, DOC, Turbidity, Chlorophyll
Dissolved and Total Al, As, Fe, Ba, Be,
Cd, Cr, Co, Cu, Pb, Mo, Ni, Se, Tl, V,
Zn, Mn, Ca, Mg, Hg
Color, Temperature, DO,
pH, Specific
conductance, ORP,
Turbidity
1/29/2014 185, 225
1/30/2014 140
3/10/2014 29.9, 87.8
3/11/2014 185, 225
3/12/2014 140
Table 5.3-2. 2014 Winter Sampling at Groundwater Well Monitoring Sites in Select Focus Areas.
Winter Focus Area Groundwater Well Monitoring
Sampling Date Focus Area Lab Parameters Field Parameters
2/6/2014 FA-104 (Whiskers Slough)
TP, SRP, Ammonia,
NO3+NO2, TKN, MeHg, TOC,
DOC, Turbidity, Dissolved and
Total Al, Fe, Hg
Temperature, pH, Specific
conductance, ORP, DO
2/12/2014 FA-138 (Gold Creek)
2/17/2014 FA-128 (Slough 8A)
3/6/2014 FA-104 (Whiskers Slough)
3/12/2014 FA-138 (Gold Creek)
3/16/2014 FA-128 (Slough 8A)
4/2/2014 FA-104 (Whiskers Slough)
4/9/2014 FA-138 (Gold Creek)
4/13/2014 FA-128 (Slough 8A)
Table 5.4-1. Focus Areas at which water quality sampling occurred.
Focus Area ID (Common Name)
FA-144 (Slough 21)
FA-141 (Indian River)
FA-138 (Gold Creek)
FA-128 (Slough 8A)
FA-115 (Slough 6A)
FA-113 (Oxbow 1)
FA-104 (Whiskers Slough)
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TECHNICAL MEMORANDUM EVALUATION OF CONTINUED MERCURY MONITORING BEYOND 2014
Table 6.1-1. Concentrations of Mercury Compared to Criteria or Thresholds.
Sample Matrix Maximum (ng/g dry or ng/L wet)
Minimum (ng/g dry or ng/L wet)
Mean (ng/g dry or ng/ L wet)
Standard Deviation No. of Observations Criteria or Threshold
Hg in Dry
Vegetation
16.1 6.71 9.16 1.9 50
MeHg in Dry
Vegetation
5.15 2.54 3.17 0.53 50
Hg in Dry Organic
Matter
129 26.8 58.25 20.04 55
Hg in Dry Soil 119 27.1 60.46 21.07 55
MeHg in Dry Soil 4.34 0.096 0.61 0.89 55
1Dissolved Hg in
Water Column
58.7 0.5 1.06 4.21 375 Acute = 2,040
ng/L
Total Recoverable
Hg in Water Column
See note 2 See note 2 See note 2 See note 2 See note 2 Aquatic Life:
Chronic = 12 ng/L
Acute = 2,400
ng/L
Human Health =
50 ng/L
Hg in Sediment 220 1.82 23.01 54.76 14 (SQuiRT) 174
ng/g
Hg in Sediment
Porewater
12.5 0.5 2.67 3.98 14
Dry Fish Tissue Hg
(no liver included)
2,920 26.9 354.23 428.47 67 329.07 ng/g – 380
ng/g
Dry Fish MeHg (no
liver included)
2,860 25.2 328.69 307.79 67
4Dry Mink Fur Hg 7,670 4,180 6,258 1,278 4
4Dry Otter Fur Hg 6,330 2,070 NA NA 2
5Wet Wt. Otter Fur
Hg
417 NA NA NA 1
1 Dissolved acute criterion is 85% of total recoverable mercury.
2 Based on results from 2013 sampling, the total mercury concentrations for 2013 from water column samples are considered high estimates
as results did not meet acceptance limits for laboratory performance. A correction factor will be developed for the 2013 results following
QA/QC review of 2014 data
3 Indicates range of total mercury reported from ADEC (2012) Susitna Basin study from several species with minimum concentration in
Sockeye Salmon and maximum concentration in lake trout. (not an AWQS).
4 Fur samples were collected outside the study area (near the Sustina River between Indian River and Portage Creek) in 2014 and results
are considered provisional until the full quality assurance review is completed by mid-December 2014. Range of concentrations of Hg in
Mink combine results from fur and fur & pelt results.
5 River otter fur collected in the study area in 2014 and results are considered provisional until the full quality assurance review is
completed by mid-December 2014. A single sample consisting of 4 hairs provided a single result.
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