United States
Environmental Protection
Agency
Office of Wetlands, Oceans,
and Watersheds
Washington DC 20460
EPA/830/R-18/003
November 2018
SEPA
Analysis of the Biological Data
Collected from the Animas
and San Juan Rivers Following
the Gold King Mine Release
Collection offish tissue samples from the Animas River
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EPA/830/R-18/003
November 2018
Final Report
Analysis of the Biological Data Collected from
the Animas and San Juan Rivers Following the
Gold King Mine Release
Authors
Lareina Guenzel and Richard Mitchell, PhD
U.S. Environmental Protection Agency, Office of Wetlands, Oceans and Watersheds
Kate Sullivan, PhD and Michael Cyterski, PhD
U.S. Environmental Protection Agency, Office of Research and Development
Office of Wetlands, Oceans and Watersheds
U.S. Environmental Protection Agency
Washington, DC 20460
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EPA Gold King Mine Biological Response Report
Notice
The development of this report was funded and managed by U.S. Environmental Protection Agency (EPA)
through its Office of Wetlands, Oceans, and Watersheds and Office of Research and Development.
Mention of trade names or commercial products does not constitute endorsement or recommendation for
use.
Preferred Citation:
U.S. Environmental Protection Agency. 2018. Analysis of the Biological Data Collected from the Animas
and San Juan Rivers Following the Gold King Mine Release. U.S. Environmental Protection Agency,
Washington, DC, EPA/830/R-18/003, November 2018.
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EPA Gold King Mine Biological Response Report
Did the GKK1 release add to biological
degradation in the already contaminated
upper Animas River ?
Did the GKM release degrade biological
communities in other segments of the
Animas and San Juan rivers that had not
been known to have historic metal impacts?
Study Questions
Biological Response to the
GKM Release
• Some fish accumulated metals the
weeks after the GKM event. Levels in
fish declined to background conditions
when samples were collected again the
following spring and never triggered
human health consumption advisories.
• There were no measurable changes to
benthic macroinverlebrate assemblages
after the GKM release.
• There were no clear impacts on fish
populations after the GKM release.
• Differences in sampling methods used
by the states and other partners across
years limited what could be inteipreted
in the report.
Executive Summary
In response to the Gold King Mine (GKM) release on
August 5, 2015, EPA mobilized field crews to sample
water, sediment, and biological data from river segments
impacted by the plume. Rivers downstream of the GKM
release included the Animas River near Silverton, CO to
its confluence with the San Juan River in Farmington
NM, and the San Juan River from the Animas confluence
to Lake Powell in Utah. A detailed examination of the
water chemistry and sediment data collected from the
Animas and San Juan rivers is presented in the EPA
QRD report Analysis of the Transport and Fate of Metals
Released from the Gold King Mine in the Animas and
San Juan Rivers (EPA/600/R-16/296).
In this report, EPA presents its analysis of available
biological data collected from the Animas and San Juan
rivers to assess how the aquatic life responded to the
GKM release. Biological communities provide a
measure of water quality and aquatic habitat quality by
responding to extreme events, such as the GKM release,
and integrating stressors over time. Data gathered for this
analysis include the EPA near-term (post-GKM release
fall 2015) and long-term (fall 2016) biological
monitoring of 30 locations, as well as biological data
collected by federal, state, and tribal partners. The
sampling and analysis approach was designed to evaluate
potential changes in the species compositions, population
abundance, and the concentration of metals in the tissue
by comparing the post-GKM release data to the pre-
release conditions.
The upper Animas River immediately below the
confluence with Cement Creek experienced the highest
metal concentrations, the greatest number of water
quality standards excursions, and the greatest deposition
of GKM sediment, during and immediately following the
GKM release. A significant increase in copper and
decreases in manganese concentration were observed in
benthic macroinvertebrate tissue in the near-term 2015
samples. Although these conditions existed, the pre- and
post-GKM release analyses did not reveal any clear
changes in the aquatic community. The lack of a
biological response is largely because the aquatic life in
this section of the river has been impacted for decades by
legacy contamination from historic mine ore processing
and ongoing acid mine drainage contamination. The
sensitive macroinvertebrate and fish species that would
be expected to respond to the GKM release were already
extirpated from the upper reaches of the Animas River.
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In the middle Animas River, we also did not observe a clear loss of, or change in the more sensitive
macroinvertebrate and fish taxa that start to appear as one moves away from the concentrated historic
mining operations in the headwaters. Our review of the Animas River adult fish population data collected
by Colorado Parks and Wildlife near Durango agrees with existing state analyses, reports, and press
releases that concluded fish were not exposed to acutely toxic concentrations in 2015. Naturally
reproducing fish species (suckers and sculpin) and trout fry continue to be found in the Animas River at
pre-release abundance levels weeks after and a year following the GKM release, however small bluehead
suckers less than <200 mm were not observed in the 2016 data. The lack of a substantial biological
response in this section of the river can be attributed to dilution of the plume, the dominant form of the
metals was particulate rather than dissolved, and exposure duration was short, which resulted in fewer
excursions of water quality standards.
Our analysis of fish tissue data collected by New Mexico Department of Game and Fish showed that many
metals were significantly elevated in bluehead sucker and flannelmouth sucker liver and speckled dace
muscle tissue samples collected in weeks after the GKM release in the lower Animas River. The degree of
metal accumulation in liver differed by species, sampling location, and among the metals, with aluminum,
cadmium, lead and manganese exhibiting the greatest concentrations. Cadmium and mercury in liver tissue
and selenium in muscle were greater in the San Juan than in the Animas. When fish were sampled the
following spring and fall in 2016, the concentration of metals in muscle/filet samples were similar to pre-
release concentrations and were low throughout both rivers. For the most part, the elevated liver
concentrations in 2015 did not translate to elevated muscle concentrations. Metal concentrations in muscle
tissue never triggered human health consumption advisories. There were no fish population data available
from this section of the Animas River to help us understand if the metal concentrations in fish tissue were
sufficiently high to adversely affect the fish populations.
By the time the GKM plume reached its confluence with the San Juan River, total metal concentrations had
declined by three orders of magnitude from what they were when the plume entered the Animas because of
the combined effects of the dilution, chemical reactions, and deposition. The excursions of aquatic life
water quality criteria in the San Juan were limited to metals that are also naturally high in the sediment and
water.
The U.S. Fish and Wildlife Service fish population data for the San Juan River show that fish abundance in
2015 and 2016 was generally within pre-release levels. The exception to this was the abundance of
bluehead sucker, flannelmouth sucker, and speckled dace in the middle reaches of the San Juan River.
These species had historically low abundance in this area in both 2015 and 2016. The razorback sucker,
Colorado pikeminnow and channel catfish, however, had high abundance in 2015 and 2016, which are
potential predator/competitor species. We cannot conclude that changes in the physical (i.e., release from
the Navajo dam resulting in a short duration of increased flow) and chemical conditions in the San Juan
River during and after the plume contributed to changes in species abundance as, the aquatic life water
quality criteria excursions were limited and the flow increase was similar to a moderate-sized storm event.
It is as plausible that a combination of ecological (increase of predator/competitor species) and physical
interactions, and/or fisheries management actions (stocking of razorback and pikeminnow), contributed to
the observed changes.
With respect to metals accumulated in biota one-year post-GKM release, metal concentrations measured in
benthic macroinvertebrate tissue and fish tissue generally track the gradient of concentrations measured in
sediment and water through the watershed. The highest metal concentrations in tissue were typically
observed in the upper Animas and the lowest concentrations were observed in the San Juan. Localized high
metal concentrations were observed in the post-release tissue data; however, the location at which the high
concentrations were observed was not consistent among years highlighting the high intra- and inter- site
variability in tissue concentrations. In fall 2016, many metals were elevated in benthic macroinvertebrate
tissue when compared to the pre-release concentration; however, the high concentrations were also
observed in the upstream and tributary samples suggesting that something other than the GKM release
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contributed to the concentration change. Likely explanations include differences in sample collection
methodologies between years andtaxonomic differences between sampling locations. A comparison of pre-
and post-GKM fish muscle data among data provider showed similar concentrations that did not exceed
human health consumption screening advisory levels.
The EPA 2016 sampling was the first effort to obtain biological data that covered the entire Animas and
San Juan rivers in a single sampling event with consistent sampling methods. Our ability to conduct a
watershed-scale analysis of data collected by all partners was limited by the different sampling and
analytical methods and revealed the need for a consistent sampling approach. This was especially true for
studies focusing on bioaccumulation of metals. Future watershed-scale monitoring efforts should include
the development of consistent sampling methods when an objective is to compare results to data collected
from other areas of the watershed.
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EPA Gold King Mine Biological Response Report
Table of Contents
Executive Summary ii
Chapter 1 Overview 1
Chapter 2 Background water quality, sediment quality and ecology in the Animas and San Juan rivers 5
2.1 Watershed features 5
2.2 General distribution of aquatic life 8
2.2.1 Fish communities 9
2.2.2 Benthic macroinvertebrates 10
2.3 Persistent stressors to aquatic life 12
2.3.1 Metals in the watershed 12
2.3.2 Metal toxicity to aquatic life in the Animas River 19
2.4 Metal water quality criteria and sediment thresholds for aquatic life 20
2.5 Gold King Mine release 21
2.5.1 GKM plume water chemistry 21
2.5.2 GKM sediment deposits 22
2.5.3 GKM release water quality effects to aquatic life 24
2.5.4 GKM release exposure to aquatic life relative to background conditions 26
2.5.5 Metals in water and sediment return to background 30
Chapter 3 Objectives, data, methods, and analysis approach for assessment of biological data in association
with the GKM release 31
3.1 Study objectives 31
3.2 Sampling design 32
3.3 Historic biological data 39
3.4 Sampling methods and laboratory analyses 40
3.4.1 Benthic macroinvertebrate assemblage 40
3.4.2 Fish populations 41
3.4.3 EPA tissue collection methods 43
3.4.4 Colorado fish tissue collection methods 43
3.4.5 New Mexico tissue collection methods 43
3.4.6 Navajo Nation fish tissue methods 44
3.4.7 Physical habitat methods 44
3.4.8 Laboratory analytes and methods 45
3.5 Data QAQC 47
3.6 Assessment approach 47
Chapter 4 Physical habitat 49
Chapter 5 Benthic macroinvertebrate assemblages 51
5.1 Benthic macroinvertebrate data 51
5.2 Benthic macroinvertebrate assemblage assessment tools 51
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5.3 Trends in macroinvertebrate communities 53
5.3.1 Longitudinal trends within the river system 53
5.3.2 Pre- and post-GKM release comparisons of benthic macroinvertebrate data 57
5.4 Summary of benthic macroinvertebrate assemblage data 61
Chapter 6 Fish populations 63
6.1 Fish and wildlife studies in the Animas River 63
6.1.1 Sentinel fish study 65
6.1.2 Fish population data 65
6.1.3 Temporal patterns of fish populations in the Animas River 65
6.1.4 Summary of CPW survey data 69
6.2 Fish abundance in the San Juan River 70
6.2.1 Longitudinal patterns of fish populations in the San Juan River 71
6.2.2 Temporal patterns of fish populations in the San Juan River 2000-2016 72
Chapter 7 Metals in benthic macroinvertebrate tissue 75
7.1 EPA benthic macroinvertebrate tissue data 75
7.2 Pre- and post-GKM release comparisons of upper Animas benthic tissue data 77
7.3 Lower Animas and upper San JuanNMDGF post-release benthic macroinvertebrate data 82
7.4 Summary of metals in benthic macroinvertebrates tissue 87
Chapter 8 Metals in fish tissue 89
8.1 Fish tissue data 89
8.2 Analysis ofNMDGF post-GKM release fish tissue data 90
8.2.1 About NMDGF fish data 90
8.2.2 Individual fish, population and tissue-specific responses 93
8.2.3 Multiple metals in fish tissue considerations 97
8.2.4 Sampling location trends 99
8.2.5 Summary ofNMDGF fish data 105
8.3 Comparison of pre- and post-GKM fish tissue metal concentrations in the Animas River among
data providers 105
8.4 Comparison of post-GKM fish tissue metals concentrations in the San Juan River among data
providers 107
8.5 Fish tissue concentrations relative to fish consumption advisory levels 107
8.6 Summary of metals in fish tissue 109
Chapter 9 One-year post-GKM release: watershed-scale longitudinal trends in metal bioaccumulation.... 111
Chapter 10 Synthesis and discussion 115
10.1 Animas River aquatic community response 115
10.2 San Juan River aquatic community response 117
10.3 Watershed scale bioaccumulation of metals 118
10.4 Future monitoring considerations 118
10.4.1 Sampling and analytical considerations 118
10.4.2 Opportunities for future watershed-scale monitoring and analysis 120
References 121
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Appendix A: Sampling locations and assoicated sampling identifications A-l
Appendix B: Data sources B-l
Appendix C: Benthic macroinvertebrate assemblage supporting information C-l
Appendix D: Colorado Parks and Wildlife sentinel fish study notes and fish stocking records D-l
Appendix E: Metal in fish tissue supporting information F-l
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Table of Figures
Figure 1.1. Map of mines within the Animas River headwaters, many of which are abandoned. Mining has not been
economically viable in this area since the early 1990s. (Map modified from USGS 2007) 2
Figure 2.1. General map of the San Juan River watershed 5
Figure 2.2. Water quality conditions along the length of the Animas River (RKM 0 to 195) and the San Juan River
below its confluence with the Animas at Farmington (RKM 195-650): A) average maximum observed
water temperatures each year at USGS gages; B) streambed sediment distribution was obtained from EPA
post-release habitat surveys; C) range of pH observed annually measured by sondes deployed at USGS
gages 2016-2018; D) water hardness in 2015-2016 samples 8
Figure 2.3. Characteristics of macroinvertebrate populations in the Animas River 11
Figure 2.4. A) Generalized regional geology map of Animas River headwaters and surrounding regions near Silverton,
CO (from: USGS 2007). B) Aerial view of the Silverton caldera area and the three main tributaries to the
Animas River; Silverton is located in the center bottom of the image (Source: GoogleEarth) 13
Figure 2.5. Longitudinal distribution of copper (Cu) in A) soils, B) river bed sediment, C) river water, D)
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996) 15
Figure 2.6. Longitudinal distribution of zinc (Zn) in A) soils, B) river bed sediment, C) river water, D) benthic
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996) 16
Figure 2.7. Longitudinal distribution of lead (Pb) in A) soils, B) river bed sediment, C) river water, D) benthic
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996) 17
Figure 2.8. Longitudinal distribution of cadmium (Cd) in A) soils, B) river bed sediment, C) river water, D) benthic
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996) 18
Figure 2.9. Observed and empirically-modeled summed total metals minus major cations, in the Animas River as the
GKM plume passed from August 5-10, 2015 (from EPA 2016c) 22
Figure 2.10. Estimated deposited mass of metals from the GKM release as it passed through the Animas and San
Juan rivers. Deposited mass was estimated in 2-km segments of river by the Water Analysis Simulation
Program (WASP) model as reported in the EPA GKM release fate and transport study (EPA 2016c). 23
Figure 2.11. Concentrations of copper, lead, cadmium, manganese and selenium in sediment at the time of benthic
macroinvertebrate (Chapter 7) and fish tissue sampling (Chapter 8) in the New Mexico segments of the
Animas and San Juan rivers 24
Figure 2.12. Total and dissolved water concentrations of four metals in the Animas River at Durango, CO from August
5-10, 2015 as the GKM plume passed through. Conditions represent the metal exposure during the CPW
sentential caged trout study presented in Chapter 6 25
Figure-2.13. Acute aquatic life hazard quotients (HQ) for water samples collected from the Animas and San Juan
rivers 27
Figure-2.14. Chronic aquatic life hazard quotients (HQ) for water samples collected from the Animas and San Juan
rivers 28
Figure 2.15. Hazard quotient (HQ) for sediment probable effects concentrations (PECs) for water samples in the
Animas and San Juan Rivers 29
Figure 3.1. Locations sampled by EPA for surface water, sediment, physical habitat and biology in the Animas and
San Juan rivers following the GKM release 33
Figure 3.2. EPA sampling locations for biological data in the upper and middle Animas River following the GKM
release 34
Figure 3.3. New Mexico Department of Game and Fish sampling locations for benthic macroinvertebrate and fish
tissue 44
Figure 4.1. Longitudinal change in a) streambed silt and fine sediment and b) riparian human disturbance physical
habitat characteristics for the Animas River, San Juan River, and Mineral Creek 50
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EPA Gold King Mine Biological Response Report
Figure 5.1. Percent of benthic macroinvertebrate assemblage composed of Ephemeroptera, Plecoptera, and
Trichoptera (%EPT) 55
Figure 5.2. Total number of taxa collected during each sampling event 55
Figure 5.3. EPA's NRSA MMI scores for samples collected through the Animas and San Juan rivers 56
Figure 5.4. Colorado MMI scores for samples collected through the Animas and San Juan rivers 56
Figure 5.5. Changes in macroinvertebrate community metrics for sites with both pre- and post-release data following
the GKM release in August 2015 57
Figure 5.6. Relative abundance of Baetis spp. within the upper Animas from pre- and post-release sampling events.
The lack of a bar for a given sampling date indicates that no organisms were sampled 59
Figure 5.7. Relative abundance of Baetis spp. within the Middle Animas from pre- and post-release sampling events.
59
Figure 5.8. Relative abundance of Baetis spp. within the Lower Animas from pre- and post-release sampling events.
60
Figure 5.9. Relative abundance of Baetis spp. within the San Juan River from pre- and post-release sampling events.
60
Figure 6.1. Map depicting CPW large and small fish survey locations on the Animas River 64
Figure 6.2. Density of brook trout caught near Howardsville, CO and Teft Spur in surveys conducted by the Colorado
Department of Parks and Wildlife 66
Figure 6.3. The number of common native fishes and important salmonids caught from the Animas River near
Durango, CO (Reach 1 & 2 in Figure 6.1) in surveys conducted by the Colorado Department of Parks and
Wildlife 67
Figure 6.4. Top: the average density (#/km) of brown trout fry caught at seven Animas River sampling areas by CPW
in the late 90's compared to surveys in 2015 and 2016 68
Figure 6.5. Relative abundance of bluehead sucker in the Animas River near Durango (Reach 1 and 2 in Figure 6.1) for
pre-release (2002-2014) compared to the fall of 2015 and 2016 69
Figure 6.6. Nine segments of the San Juan River that have been historically sampled to assess fish abundance by the
USFWS 70
Figure 6.7. The average CPU for A) flannelmouth sucker, B) razorback sucker, and C) channel catfish at sampled
reaches of the San Juan River averaged from 2000-2016 71
Figure 6.8. Average CPUE for flannelmouth sucker, bluehead sucker, and speckled dace at A-C) high abundance sites
(LVW-020 and SJFP), D-F) intermediate abundance sites (SJSR, SJ4C, SJMC, and SJBB), and G-l) low
abundance sites (SJMH and SJCH) during the years 2000-2016 73
Figure 6.9. Average CPUE for 2000-2016 for A) razorback suckers at high abundance sites (SJFP and SJSR), B)
razorback sucker at low abundance sites (SJ4C, SJMC, SJBB, SJMH, and SJCH), C) channel catfish at all sites,
and D) Colorado pikeminnow at all sites 74
Figure 7.1 Comparison of the absolute value of the relative percent difference in benthic macroinvertebrate tissue
concentraitons by metal and sampling location 76
Figure 7.2. Comparison of pre (2012&2014) and post (2015 &2016) GKM release arsenic, aluminum, cadmium,
copper, iron and lead concentrations in benthic macroinvertebrate tissue samples collected from the
upper and middle Animas River 78
Figure 7.3 Comparison of pre (2012&2014) and post (2015 &2016) GKM release manganese, mercury, nickel,
selenium, and zinc concentrations in benthic macroinvertebrate tissue samples collected from the upper
and middle Animas River 79
Figure 7.4 Percent difference calculated from the natural log transformed pre-GKM release (2014) and post-GKM
release (2015) data collected from the upper Animas River 81
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Figure 7.5. The concentration of aluminum, arsenic, and cadmium measured in benthic macroinvertebrate tissue
samples collected by the NMDGF in the lower Animas and upper San Juan rivers in August 2015 and
March 2016 83
Figure 7.6 Concentration of copper, lead, and manganese measured in benthic macroinvertebrate tissue samples
collected by the NMDGF in the lower Animas and upper San Juan rivers in August 2015 and March 2016.
84
Figure 7.7. The mean concentration of metals ± 1SD (ppm ww) in all benthic macroinvertebrate taxonomic groups by
location in August 2015 and March 2016 86
Figure 8.1. Body size distribution offish by species sampled at all sites in August 2015. Boxplots show mean, median,
and quartiles 91
Figure 8.2. Liver tissue concentration of copper, lead, aluminum, arsenic, manganese and cadmium (mg/kg ww) in
individual fish identified by species 94
Figure 8.3. Muscle tissue concentration of copper, lead, aluminum, arsenic, manganese and cadmium (mg/kg ww) in
individual fish identified by species 95
Figure 8.4. Tissue concentrations of mercury and selenium (mg/kg ww) in liver and muscle samples of individual fish
identified by species 96
Figure 8.5. Comparison of the cumulative metal values in A) liver by species, B) muscle by species, C) liver by
sampling date and D) muscle by sampling date 98
Figure 8.6. Mean concentration of lead, aluminum, and arsenic in liver and muscle (mg/kg ww) of all fish sampled by
NMDGF at each location in each sampling period 100
Figure 8.7. Mean concentration of manganese, copper, and selenium in liver and muscle (mg/kg ww) of all fish
sampled by NMDGF at each location in each sampling period 101
Figure 8.8. Mean concentration of selenium and mercury in liver and muscle (mg/kg ww) of all fish sampled by
NMDGF at each location in each sampling period 102
Figure 8.9. Relationship offish tissue concentration to environmental metal concentrations for brook trout and
rainbow trout grouped and bluenose and flannelmouth suckers grouped for 3 metals 104
Figure 8.10. Comparison of pre-GKM brown trout and rainbow trout muscle tissue data collected at the Southern
Ute Indian Reservation to post-GKM data collected by EPA contractors (Fall 2016), Colorado Department
of Public Health (March 2016), and Environment and New Mexico Department of Game and Fish (March
2016) 106
Figure 8.11. Tissue concentration of aluminum and trace metals in channel catfish at multiple locations in the San
Juan River. Data were collected by NNEPA and EPA contractors after 2016 snowmelt had returned
conditions to background. NMDGF data were collected in August 2015 immediately after the GKM release
and in March 2016 108
Figure 8.12. Tissue concentration of selenium and mercury in channel catfish at multiple locations in the San Juan
River. Data were collected by NNEPA and EPA contractors after 2016 snowmelt had returned conditions
to background. NMDGF data were collected in August 2015 immediately after the GKM release and in
March 2016 109
Figure 9.1 Concentration of 2016 arsenic, lead cadmium, copper, lead, manganese and zinc in benthic
macroinvertebrate and fish filet (ppm dw), sediment (ppm dw), and dissolved water (ppb) with distance
from GKM (km) 113
Figure 9.2 Concentration of 2016 aluminum, iron, mercury, nickel, and selenium in benthic macroinvertebrate and
fish filet (ppm dw), sediment (ppm dw), and dissolved water (ppb) with distance from GKM (km). 114
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Table of Tables
Table 2.1 Fish occurrence within the Animas and San Juan rivers, as available from various sampling data listed in
Chapter 3 10
Table 2.2. Sediment probable effects concentration (PEC) benchmarks for aquatic life from MacDonald et al. (2000).
20
Table 3.1. Sampling locations and dates for biological and physical habitat data collected by the EPA, EPA
contractors, states, tribes and federal partners during the GKM-plume through spring 2017 35
Table 3.2. Comparison of benthic macroinvertebrate sampling methods used by the different data providers. 41
Table 3.3. A comparison of adult fish population sampling methods used by the Colorado Parks and Wildlife and U.S.
Fish and Wildlife Service to sample the Animas River and San Juan River, respectively 42
Table 3.4 Summary of the components used to characterize physical habitat at wadeable sampling locations. Similar
components were measured at non-wadable sites with methods that are modified to allow for sampling
from a boat 45
Table 3.5. Analytical methods, parameters and technology used for the biological tissue samples collected by EPA,
CDPHE, SUIT, and NMDGF 46
Table 3.6. Summary of pre- and post-GKM release biological and physical habitat data collected from the Animas and
San Juan rivers presented in this report 48
Table 4.1. EPA National Rivers and Streams Assessment physical habitat indices used to describe the aquatic habitat
condition 49
Table 4.2. Physical habitat condition for sampling locations on the San Juan River with pre-release NRSA physical
habitat data including 1 site on the San Juan River located upstream of the confluence with the Animas
(SJAR), and two downstream locations SJMC and SJBB 50
Table 5.1. EPA's NRSA benthic macroinvertebrate multi-metric index (MMI) characteristics for ecoregions applicable
to the Animas and San Juan rivers 52
Table 5.2. Colorado benthic macroinvertebrate MMI characteristics for Animas River biotypes 53
Table 5.3. Comparison benthic macroinvertebrate assemblage indices and metrics for sites that have pre- and post-
GKM release data 58
Table 6.1 Summary of the GKM response sampling and data collected by Colorado Parks and Wildlife 63
Table 7.1 Total number of benthic macroinvertebrate tissue samples (pre- and post-GKM) and percent detection by
analyte 75
Table 7.2. Mean metal concentrations in benthic macroinvertebrate tissue samples collected from the upper Animas
River (A68, A72, A73, A75D and Baker's Bridge) 77
Table 7.3. The mean difference in metal benthic macroinvertebrate concentration between the pre-release (2014)
and post-GKM (2015) samples collected from the upper Animas River (A72, A73, A75D and Baker's
Bridge), results of the statistical comparisons of the percent change, and potential sample variability. 81
Table 7.4. The total number and percent detection of samples that exceed the laboratory reporting limit of the
NMDGF benthic macroinvertebrate tissue metals data by taxonomic group 82
Table 8.1. Summary of general metals effects from the GKM release in the Animas and San Juan rivers during fish
sampling in August 2015 (post-release) and March 2016 90
Table 8.2. Count offish by location, sampling event, tissue type and species during fish tissue sampling conducted by
the NMDGF after the GKM release (August 2015) and in March 2016. Livers were collected from the same
fish as muscle tissue and were not collected from speckled dace 92
Table 8.3. Mean metal concentration measured in liver and muscle tissue samples collected by NMDGF in August
2016 and March 2017. Highlighted cells identify statistically significant differences in the species mean
concentration by sampling date (p<0.05) 97
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Table 9.1. Geometric mean metal concentration +/-1SD in benthic macroinvertebrate composite samples collected
in fall 2016 and fish filet samples (ppm dw) collected from the Animas and San Juan rivers in fall 2016 and
spring 2017 Ill
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Acknowledgments
EPA acknowledges all of the organizations that provided data and information for this report, including
EPA Regions 6, 8, and 9; Colorado Department of Public Health and Environment (CDPHE), Colorado
Parks and Wildlife (CPW); New Mexico Environment Department (NMED); New Mexico Department of
Game and Fish (NMDGF); Southern Ute Indian Tribe (SUIT); Ute Mountain Ute Tribe (UMUT); Navajo
Nation Environmental Protection Agency (NNEPA); Mountain Studies Institute (MSI); the Rivers of
Colorado Water Watch Network; and U.S. Fish and Wildlife Service (USFWS). EPA acknowledges the
contributions of Sandra Spence, Dan Wall, Maggie Pierce, and Karl Herman in EPA Region 8, Robert
Cook in Region 6, and Lourdes Prieto in EPA ORD who assisted in the report review and production.
Acronyms
AMD
acid mine drainage
CMP
conceptual monitoring plan
DOC
dissolved organic carbon
dw
dry weight
GKM
Gold King Mine
GLM
generalized linear model
RKM
river kilometer
MDL
minimum detection limit
MMI
multimetric index
ppb
parts per billion
ppm
parts per million
WW
wet weight
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EPA Gold King Mine Biological Response Report
CHAPTER 1 OVERVIEW
The impact of historic mining on water resources in the Animas River watershed in the San Juan Mountains
of southwest Colorado has been a concern for decades. Beginning in the 1870s, the headwaters of the
Animas River near the town of Silverton became home to a dense network of hard rock mines from which
gold, silver, lead, zinc, and copper ores were extracted from the highly mineralized geologic formations
found in the Colorado mineral belt (Figure 1.1). Mining operations in this area ceased by the early 1990s,
leaving hundreds of abandoned mines that historically have discharged an average of 5.4 million gallons of
acidic mine drainage (AMD) per day into the headwaters of the Animas River (USGS 2007). AMD
contains high concentrations of heavy metals, such as iron, aluminum, zinc, lead, cadmium, copper, and
many others. Metals generated from AMD and historic ore processing have impacted the Animas River and
its aquatic life for more than a century. The U.S. Geological Survey (USGS) focused considerable research
activity in the upper Animas watershed from 1995 to 2007, to guide restoration plans to abate AMD and
reduce metals contamination (USGS 2007) in this heavily impacted area. Research included the collection
of physical, chemical and biological data as well as metals accumulation in biota and toxicity tests.
As a result of these studies, federal and state governments, as well as stakeholder groups have conducted
remediation activities in the watershed. The Animas River Stakeholder Group, the Bureau of Land
Management, the Colorado Division of Reclamation/Mining and Safety, and EPA Region 8 have
completed remediation projects in the watershed (EPA Region 8, Upper Animas Mining District: Draft
Baseline Ecological Risk Assessment, http://www2.epa.gov/region8/upper-animas-mining-district-draft-
baseline-ecological-risk-assessment). The Colorado Department of Public Health and the Environment has
developed more than twenty-five Total Maximum Daily Loads (restoration plans required for waterbody
segments considered impaired under the Clean Water Act) to help guide restoration activities towards
meeting water quality standards. However, for some waters, including Cement Creek, the State of Colorado
has followed procedures under the Clean Water Act to remove aquatic life support as a designated use for
the waterbody because it is not an attainable goal (Colorado Department of Public Health & Environment,
https://www.colorado.gov/pacific/cdphe/tmdl-san-iuan-and-dolores-river-basins).
On August 5, 2015, an EPA team investigating the Gold King Mine as a source of metals inadvertently
triggered a release of 3 million gallons of acidic, mine-influenced waters. These waters had been trapped by
the collapsed mine structure and rock blocking the opening (or adit) of the mine, damming the water behind
the collapse and causing the waters to become pressurized. Over an eight-day period, the plume from the
release flowed down the Animas River to the San Juan River. The EPA report One Year After the Gold
King Mine Incident (EPA 2016f) provides an overview of the EPA's response to the GKM release and
additional information on the environmental conditions of the watershed prior to and after the incident.
The EPA, the states, and tribes began monitoring metals in water and river bed sediments throughout the
affected rivers to assess risk to public health as compared with water quality criteria and probable effect
concentrations. In September 2015, the EPA released a follow-up draft conceptual monitoring plan (CMP)
that specified how the agency would gather scientific data on physiochemical and biological parameters
downstream of the GKM release. The CMP was finalized March 2016 and incorporated comments received
from local, state and tribal stakeholders; knowledge gained from the first round of sampling in fall 2015
and increased familiarity with the historic data, (https://www.epa.gov/sites/production/files/2016-
03/documents/post-gkm-final-conceptual-monitoring-plan_2016_03_24_16.pdf). The primary objective of
the CMP was to provide biological data that span the watershed that can be used to compare current
conditions to conditions that existed in the watershed prior to the GKM release. These data were also
collected for use by EPA, states, tribes, and local entities to supplement a general assessment of water
quality, sediment quality, and biological conditions in the watershed.
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EPA Gold King Mine Biological Response Report
COLORADO
# •. v-t.; V
• • •# ;i..v
bouniary
Figure 1.1. Map of mines within the Animas River headwaters, many of which are
abandoned. Mining has not been economically viable in this area since the early 1990s.
(Map modified from USGS 2007).
The EPA Office of Research and Development (ORD) report Analysis of the Transport and Fate of Metals
Released from the Gold King Mine in the Animas and San Juan Rivers (EPA/600/R-16/296) provides a
detailed examination of the water chemi stry and sediment data collected from the Animas and San Juan
rivers before, during and after the release (EPA 2016c).
This report presents EPA's analyses of the biological data collected from the Animas and San Juan rivers
during the GKM release and in the months following, using data collected by states, tribes, federal partners,
and EPA. Post-release data providers included Colorado Parks and Wildlife (CPW), Colorado Department
of Public Health and Environment (CDPHE), New Mexico Environment Department (NMED), New
Mexico Department of Game and Fish (NMDGF), Southern Ute Indian Tribe (SUIT), Navajo Nation
Environmental Protection Agency (NNEPA), and U.S. Fish and Wildlife Service (USFWS). Biological
data presented here include fish and benthic macroinvertebrate community data, biological tissue data, and
physical habitat. States and tribes have already reported key findings of agency studies of the immediate
impacts of the event to their stakeholders.
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EPA Gold King Mine Biological Response Report
The objective of this report was to consolidate available data into an integrated analysis of the biological
response to the GKM release by exploring the following questions:
1. Did the GKM event add to biological degradation in the already contaminated upper Animas
River?
2. Did the GKM release degrade biological communities in other segments of the Animas and San
Juan rivers that had not been known to have historic metal impacts?
3. Were acute impacts to the biological communities observed during the initial GKM release when
metals concentrations were highest?
4. Were long-term changes in biological communities observed a year after the GKM release?
Report Outline
Chapter 2 provides an overview of the Animas and San Juan rivers watersheds, emphasizing the factors that
influence aquatic habitat and metals characteristics that contribute to the distribution and vitality of
macroinvertebrate and fish communities. The overview provides a brief review of two decades of extensive
study of the impact of acid mine drainage and historical mining practices on the biological conditions in the
mining district in the headwaters of the Animas River by USGS, EPA and academic researchers. This
chapter also reviews the physical and chemical conditions that may have influenced biological communities
during and after the GKM release.
Chapter 3 discusses the available biological data and methods of analysis used to synthesize a river-wide
assessment of the GKM release. Biologic data was collected by states, tribes, watershed groups, the
USFWS and EPA before, during, and after the GKM release.
Chapter 4 provides an overview of the post-GKM physical habitat conditions data collected by EPA and
contractors.
Chapters 5 and 6 present the benthic macroinvertebrate assemblage and fish community analyses,
respectively. Pre- and post-GKM release analyses are provided for sections of the Animas and San Juan
River with historic data.
Chapters 7 and 8 present analyses of the metals accumulated in benthic macroinvertebrate and fish tissue,
respectively.
Chapters 9 and 10 synthesize the findings and present watershed wide longitudinal trends in metal
concentration a year following the release, after the GKM deposit moved through the system. Chapter 10
also provides recommendations for future biological monitoring in the San Juan watershed.
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EPA Gold King Mine Biological Response Report
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EPA Gold King Mine Biological Response Report
CHAPTER 2 BACKGROUND WATER QUALITY, SEDIMENT QUALITY AND
ECOLOGY IN THE ANIMAS AND SAN JUAN RIVERS
2.1 Watershed features
The Animas River is a major tributary to the San Juan River that originates within the San Juan Mountains
in southwestern Colorado. After flowing southward for 200 km, the Animas joins the San Juan River at
Farmington, NM. (Figure 2.1). The San Juan River then flows westward for nearly 400 km through
increasingly arid s terrain until it flows into Lake Powell in Utah. The Animas and San Juan rivers
downstream of their confluence are hereafter referred to as the study area.
The baseline physical and chemical characteristics within the rivers establish the foundation for the
expected composition and abundance of the aquatic biota. Physical habitat characteristics such as water
temperatures, channel slope and river bed morphology, and composition influence the spatial distribution of
aquatic communities at a watershed and local scale. River ecosystems change significantly along the 600-
km length as the Animas and San Juan rivers transition through more than 5,100 ft (1,500 m) of elevation
change and flow through diverse climatic, geologic and geomorphic conditions. Anthropogenic alterations
to these conditions (e.g., riparian disturbance, channelization, flow modification and water quality
degradation) affect the abundance and distribution of species that would normally be expected to occupy
those habitats.
Colorado
A"a Yd fo
leservoir
Arizona
New
Mexico
Sources: Esrit USGS. NOAA
Figure 2.1. General map of the San Juan River watershed.
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EPA Gold King Mine Biological Response Report
Cement Creek (RKM 12.5)
Animas: at Bakes Bridge (RKM 64)
Animas: south of Durango (RKM 110)
Animas: near Cedar Hill (RKM 147)
Animas: at Farmington (RKM 190)
Upper and middle Animas River
The Animas River originates high in the San Juan Mountains of
southern Colorado near the town of Silverton, Colorado. Aquatic
habitats lie within the alpine and subalpine forests with most of the
watershed managed as the San Juan National Forest. From 8,500 ft
(2,600 m) elevation in Silverton, the Animas River flows
southward for approximately 50 km, descending through a steep
and narrow canyon carved into the Precambrian basement rocks.
The Animas abruptly exits the canyon at Baker's Bridge (RKM
64) and flows onto a wide alluvial valley near Hermosa Springs
about 30 km north of Durango, CO. The channel is heavily braided
for about 10 kilometers before establishing a meandering form that
persists to Durango. The high gradient segment above Bakers
Bridge is generally referred to as the upper Animas, while the
lower gradient segment that extends downstream through Durango
and the Southern Ute Indian Reservation to the Colorado/New
Mexico border is referred to as the middle Animas.
Within the upper Animas and tributaries (e.g., Cement Creek and
Mineral Creek), summer water temperatures are relatively cool (<
17°C; Figure 2.2) and river morphology is steep (0.7 to 1.6%
gradient) and characterized by riffles, cascades, and falls with
coarser substrates composed of gravel, cobble and boulders. Upon
exiting the canyon, the middle Animas segment transitions to
warmer water, fine substrate size, and transitional biotic
communities.
Lower Animas River
The Animas River becomes more constrained with a straighter
course within the incised valley from Durango, CO to Farmington,
NM where it joins the San Juan River 190 km from the headwaters
origin. The segment between Cedar Hill and Farmington is
generally referred to as the lower Animas River. The lower reaches
of the Animas are warm (maximum temperatures 26°C; Figure
2.2), channel slopes are moderate (0.4%) and habitat conditions
continue to transition to low gradient, fine substrate channels.
San Juan River
The San Juan River has been regulated by the Navajo Dam located
approximately 60 km upstream of its confluence with the Animas
at Farmington since the 1960's. The Animas routinely supplies
approximately 50% of the flow of the combined rivers and is the
primary unregulated source of perennial flow to the San Juan. The
Navajo Dam has altered the flow regime of the San Juan River
downstream of the dam, changing its ecology from a warm, muddy
and highly seasonal river to one with relatively constant flows. The
San Juan River retains more of its unregulated nature below the
confluence of the Animas
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EPA Gold King Mine Biological Response Report
San Juan: in Farmington (RKM 194)
San Juan: at Shiprock (RKM 246)
Spring snowmelt from the Animas and monsoonal storms in
the more arid tributaries are the primary source of flow
variability. Maximum water temperatures can exceed 30°C.
The San Juan River flows westerly towards its junction with
the Colorado River near Mexican Hat, UT within a valley that
for most of its length is shallowly incised into a series of
sedimentary rock formations at various depths. The river flows
through highly erodible marine and continental sedimentary
rocks and carries a high sediment load during seasonal storms.
Valley width ranges from tens to hundreds of meters and
channel widths range from 50 to 100 m with low gradient
ranging from 0.07 to 0.16% and dominated by fine-grained
particles. Braided channels are common in most of the
intermittent tributaries and probably was in much of the San
Juan River mainstem before flow control. Now the main stem:
channel alternates between stable multi-threaded channels with
vegetated island bars and straight intervening segments.
Land Use
Most of the combined Animas and San Juan River watershed
are remote and uninhabited. Vegetation is characterized by
subalpine forests in the headwaters of the Animas that is
managed primarily by the US Forest Service and shrubland,
rangeland and grassland i n the rest of the area (EPA 1979). The
watershed is lightly populated, with most settlements
concentrated along the San Juan and Animas
rivers. Farmington, New Mexico is the largest city and other
major population centers include Durango, Colorado, and
Aztec, and Shiprock, New Mexico. Irrigated agriculture is a
major land use in the middle and lower reaches of the Animas
River, withdrawing water through a system of ditches and
canals. There are also numerous wells drilled into the river
floodplains that supply public, domestic and irrigation users.
The San Juan River flows through the states of New Mexico
and Utah and the tribal lands of the Navajo Nation and Ute
Mountain Ute Tribe. Within this generally arid area, the river
supports irrigated farming. A large canal diverts water from the
San Juan River near Waterflow, NM to supply regional
irrigation water needs. Near Mexican Hat, UT, the San Juan
River ultimately flows into Lake Powell created by the Glen
Canyon Dam at Page, AZ at elevation of 3,400 ft. Population
density is sparse downstream of Shiprock, NM. Most of the
lower San Juan River in Utah flows through inaccessible
canyons that largely preclude habitation.
(RKM 346; August 2015)
San Juan: at Montezuma Creek
Photo: Utah Department of Environmental Quality
San Juan: at Bluff, Utah
(RKM 377; USGS Gage)
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EPA Gold King Mine Biological Response Report
A)
30
u
o
2 25
s
2
§.20
E
£
15
10
C)
12.4
Summer Maximum Water Temperature
200 300
Distance from GKM (km)
Annual Range of pH
Animas
San Juan
16.4
94 162.5 196 246
Distance from GKM (km)
2%
422
B)
Streambed Silt and Fine Sediment
100
90
SO
70
60
50
40
30
20
10
0
• Animas
~ San Juan
~ Mineral
D)
10,000
1,000
100 200 300 400 500 600
Water Hardness
Animas
> San Juan
100
100
500
600
200 300 400
Distance from GKM (km)
Figure 2.2. Water quality conditions along the length of the Animas River (RKM 0 to 195) and the San Juan River
below its confluence with the Animas at Farmington (RKM 195-650): A) average maximum observed water
temperatures each year at USGS gages; B) streambed sediment distribution was obtained from EPA post-
release habitat surveys; C) range of pH observed annually measured by sondes deployed at USGS gages 2016-
2018; D) water hardness in 2015-2016 samples.
2.2 General distribution of aquatic life
Fish need plants, insects and benthic macroinvertebrates to eat; in-stream and streambank cover for shelter;
appropriate streambed substrate conditions for spawning; and overhanging vegetation to shade the water in
which they live. The changes in temperature, dissolved oxygen, pH and myriad other physical and chemical
constituents in water along the river continuum influence the changes m species composition, species
abundance, and physical habitat that are observed as one moves from the headwaters down to Lake Powell.
The general longitudinal change in water quality and sediment conditions along the Animas and San Juan
rivers is provided in Figure 2.2. Water temperature increases while particle size of the benthic sediment
decreases with distance from headwaters. Watershed geology strongly influences water quality. The
volcanic geology within the upper Animas generate river flow with low pH and high metals content. The
sedimentary rocks characteristic of most of the watershed buffer pH. The importance of headwaters
geology in determining water quality will be discussed later in this chapter.
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EPA Gold King Mine Biological Response Report
2.2.1 Fish communities
Fish communities transition from coldwater species in the headwaters of the Animas River to warmwater
communities in the San Juan (Table 2.1). The upper Animas River lies entirely within alpine and subalpine
habitats and would be expected to support coldwater species typical of the Colorado Rockies. Barriers to
upstream movement in the Animas River canyon limited the composition of the native fish community to
cutthroat trout that are currently found in high altitude tributaries with good water quality (vonGuerard el
al. 2007). Brook trout were introduced to the upper Animas as early as 1885. Brook trout are well adapted
to coldwater, small stream habitats. Populations are sustaining and brook trout are currently the
predominant fish species, but are locally impacted by poor water quality (Besser and Brumbaugh 2007).
Rainbow trout were also stocked in the upper Animas at various times but were not as successful.
Below the Animas canyon, native fish species include bluehead sucker, flannelmouth sucker, white sucker,
speckled dace, and mottled sculpin. The Colorado Division of Wildlife (CDW) manages two segments of
the middle Animas River between Durango and the Colorado/New Mexico border to provide a high quality
recreational fishery of brown and rainbow trout. Natural reproduction of trout in the middle Animas River
is low; therefore, the fishery is supported by annual stocking with fry/fingerling/sub-catchable salmonids"
and catch limits are used to control angling pressure (CDW 2010, 2015). Cutthroat trout fingerlings have
also been stocked since 2005. Regular inventories of the Animas River fish for the last several decades
have shown that trout biomass and density vary from year to year due to multiple factors including water
temperatures, stocking rates, and potentially metals from the upper Animas basin (CDW 2010). Summer
water temperatures are near optimal for rainbow and brook trout in this segment (generally within 18°C)
but maximum temperatures can become stressful for rainbow trout during low flow years. The river is also
heavily used for recreational boating and swimming.
The lower Animas River is wider and warmer than the middle Animas. New Mexico Environment
Department (NMED) classifies this reach as marginal coldwater aquatic life (20.6.4 NMAC). Maximum
summer temperatures reach 28°C but seasonal temperatures during other times of the year are much more
moderate. New Mexico Department of Game and Fish (NMDGF) stocks a two-mile reach of the Animas
through Aztec, NM with catchable rainbow trout. The lower Animas has abundant populations of bluehead
suckers, flannelmouth suckers, and speckled dace with white suckers also present. The U.S. Fish and
Wildlife Service (USFWS) has stocked razorback sucker and Colorado pikeminnow in the lower Animas
River annually since 2011.
Like the lower Animas, the upper San Juan River near Farmington is designated as marginal coldwater
aquatic life and warmwater aquatic life by NMED. Summer maximum temperatures exceed 28°C. The San
Juan River provides habitat to at least eight native species including cutthroat trout, roundtail chub,
speckled dace, flannelmouth sucker, bluehead sucker, mottled sculpin, Colorado pikeminnow and
razorback sucker, with a possible ninth species being the bonytail chub. The non-native common carp and
channel catfish have become widespread in the lower reach of the San Juan (USFWS 2006). Rainbow and
brown trout occur near Farmington but abundance varies seasonally.
The San Juan River downstream of the Animas River is designated as critical habitat for federally
endangered Colorado pikeminnow and razorback sucker. The San Juan River Recovery and
Implementation Program (SJRIP) was established to support the recovery of the endangered Colorado
pikeminnow and razorback sucker, in conjunction with water development projects in the basin. The
USFWS with state and tribal partners manage the plan including conducting long-term fish community
surveys from the Navajo Reservoir to Lake Powell. The braiding channel type characteristic of this low
gradient river is important to successful reproduction of the native fish that use low velocity and backwater
habitats created by the braiding channel morphology. Flow management at the Navajo dam contributes to
the loss ofbraided-channels and associated habitat. Endangered fish are also subject to predation from non-
native fish; channel catfish are actively removed to facilitate recovery of the endangered fish.
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EPA Gold King Mine Biological Response Report
Table 2.1 Fish occurrence within the Animas and San Juan rivers, as available from various sampling data listed in
Chapter 3.
Common Name
Scientific Name
General Area Within Watershed
Collected
Status and Notes
Brook trout
Salvelin us fon tin alis
Upper Animas
Introduced, population limited
due to metals
Brown trout
Salmo trutta
Upper, middle, lower Animas,
upper San Juan durring sometimes
of year
Introduced, annual stocking
program in middle Animas
Rainbow trout
Oncorhynchus mykiss
Upper, middle, and lower Animas
Introduced, annual stocking
program in middle Animas
Cutthroat trout
Oncorhynchus clarkii
Upper and middle Animas
Native, confined to
uncontaminated high elevation
streams outside the mining
district; occasionally stocked
Mottled sculpin
Cottus bairdii
Upper and middle Animas
Native; limited in upper Animas
due to metals
Speckled dace
Rhinichthys osculus
Middle and lower Animas,
upper San Juan
Native
Bluehead
sucker
Catostomus discobolus
Middle and lower Animas,
upper San Juan
Native, larger river habitats
Flannelmouth
sucker
Catostomus latipinnis
Middle and lower Animas,
upper San Juan
Native, larger river habitats
White sucker
Catostomus
commersonii
Lower Animas
Native, larger river habitats
Razorback
sucker
Xyrauchen texanus
Upper and lower San Juan
Native, endangered status
since 1991 (flow modification)
Colorado
pikeminnow
Ptychocheilus lucius
Upper and lower San Juan
Endangered status since 1967
(flow modification)
Channel catfish
Ictalurus punctatus
Upper and lower San Juan
Introduced, eradication
program to reduce predation
on native fish
Common carp
Cyprinus carpio
Upper and lower San Juan
Introduced, eradication
program to reduce predation
on native fish
2.2.2 Benthic macroinvertebrates
Streams can have several hundred different kinds of benthic macroinvertebrates with total numbers ranging
in the thousands. Three orders of aquatic insects are common in the benthic macroinvertebrate
communities. These orders are Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera
(caddisflies). EPT taxa (combined Ephemeroptera, Plecoptera, and Trichoptera) tend to prefer higher
gradient, coarse substrate habitats and would be expected to be observed in high abundance in the coarser
river substrates characteristic of most of the Animas River. These taxa are also generally considered to be
sensitive to or intolerant of pollution and are widely used as indicators of water quality.
Macroinvertebrate communities have been sampled through the length of Animas River at various time s
over the past 20 years. Anderson et al. (2007) sampled the Animas River from the headwaters downstream
to the boarder with NM and a single sample in New Mexico in 1996, finding some degradation of benthic
macroinvertebrate communities relative to reference tributaries throughout. Various metrics of
macroinvertebrate communities presented by Anderson et al. (2007) are shown n Figure 2.3. Species
richness, number of taxa, and sensitive taxa are very low in the upper Animas River within the first 50 km
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EPA Gold King Mine Biological Response Report
of river length and tend to increase once the river enters onto the alluvial river valley near Bakers Bridge
(e.g. caddisflies and mayflies in Figure 2.3). While the San Juan River is not represented in the graphs
below, the expected composition of San Juan River macroinvertebrate communities would not be the same
as that expected from the Animas River. The macroinvertebrate composition in the San Juan River would
reflect the differing physical and chemico-physical factors such as the presence of increased fine-grained
particles in the stream bed as well as warmer water temperatures.
C)
Macroinvertebrate Population Density—Animas River
—~—Caddisflies -¦ Mayflies
B)
Macroinvertebrate Population Density-Animas River
E
II
Q- 150
0 50 100 150 200
Silverton Durango Farmington
Distance from Headwaters (km)
NRSAMMI Score
A)
Macroinvertebrate Population Density—All Species
3,000
2,500
2,000
E
"J 1,500
.o
E
2 1,000
50 100 150
Distance from Headwaters (km)
0 50 100 150 200
Distance from GKM (km)
1,400
1,200
0
0 50 100 150
Silverton Durango
Distance from Headwaters (km)
200
Farmington
Figure 2.3. Characteristics of macroinvertebrate populations in the Animas River. Data in figures A-C present
data from Anderson (2007), D) presents pre-release data collected by states and tribes.
The biological condition of the nation's flowing waters is assessed every five years during the EPA's
National Rivers and Streams Assessment (NRSA). In this national survey, regionally specific benthic
macroinvertebrate multi-metric indices (MMI) are the primary tool for assessing biological condition. Five
to six individual assemblage metrics, such as taxonomic richness, composition and diversity, functional
feeding groups, habits/habitats, and pollution tolerance, are combined to create each of the regionally
specific MMIs (EPA 2016b). By combining metrics that represent different aspects of the benthic
macroinvertebrate assemblage, each MMI integrates the influence of multiple chemical and physical
stressors. Additionally, due to the unique life history characteristics of benthic macroinvertebrates (life
cycles of weeks to a few years and relatively immobile), this assemblage integrates the spatial and temporal
impacts of stressors more comprehensively than other biological assemblages, such as algae and fish.
Regionally specific reference conditions were used to develop biological condition benchmarks for each
regional MMI. NRSA MMI scores for the Animas River are shown in Figure 2.3, and have been
categorized into good, fair, and poor condition based upon regionally relevant benchmarks, either the
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EPA Gold King Mine Biological Response Report
Western Mountains or Xeric aggregate ecoregion (EPA 2016b). When applied to pre-release samples,
NRSA MMI scores show a trend of increasing benthic macroinvertebrate condition on the Animas River as
you get further from the headwaters (Figure 2.3 D).
2.3 Persistent stressors to aquatic life
There are numerous stressors to fish and benthic macroinvertebrates in the Animas and San Juan rivers.
Like most watersheds, land use often impacts water quality through introduction of pollutants and loss of
riparian function. Those factors as well as flow management and recreational river use affect water quality
and aquatic communities, especially in the middle and lower reaches of the Animas and San Juan where
populations centers are located. Nutrient loading from agricultural runoff is high in lower reaches of the
Animas River. Sediment loads are high in the lower Animas and San Juan River during monsoonal storms
that occur in the region during the summer/fall months. However, metals contamination of water and
sediment due to the headwaters geology and past mining activity have had an impact on aquatic life in the
upper Animas River, extending downstream for some distance.
2.3.1 Metals in the watershed
The Animas River originates in a regionally important geologic zone known as the Colorado Mineral Belt
that was formed in a series of regional volcanic eruptions that took place during the late Paleogene (28-
23M years ago). Regional volcanism left relict features including the remnants of a large caldera almost 19
km in diameter that is also the source of the Animas River. Within the caldera are mineralized sulfide ores
that contain extensive areas of naturally acidic rocks and soils with vein-type deposits of gold, silver, zinc,
and copper. The ore deposits were extensively mined for 120 years before the last mine was shuttered in
1991 (Luedke and Burbank 1999; von Guerard etal. 2007).
The ore bodies generate high concentrations of trace heavy metals in soils and water and naturally low pH
in the streams that drain them. Three main headwater tributaries define the area containing the sulfide ores
and the mining district. Mineral Creek and the Upper Animas River border the caldera on its western and
eastern sides, respectively (Figure 2.4.A). Portions of their watersheds also drain the surrounding
calcareous sedimentary rocks that buffer acidity and create locally variable conditions of metals
concentrations and pH within these streams. Cement Creek dissects the caldera and has persistently high
metals concentrations and very low pH. Cement Creek, Mineral Creek, and the upper Animas River
converge in the valley where the town of Silverton is located (Figure 2.4.B).
Water quality in the upper Animas River and its tributaries is influenced by natural ores and historic
mining. Mining activities have added substantially to metals concentrations in water and sediments in the
aquatic environment. Mining operations left hundreds of abandoned mines with many miles of
underground workings that have altered subsurface hydrology at a hillside scale. The mining voids collect
and provide preferential flow paths for groundwater while the voids provide an ideal environment for
oxygen enrichment that triggers the acid-producing reactions in the ore deposits. Abandoned mines have
historically discharged an average of 5.4 million gallons of AMD per day into the headwaters of the
Animas River (USGS 2007). AMD contains high concentrations of heavy metals, such as iron, aluminum,
zinc, lead, cadmium, copper, and many others.
It was also common practice through much of the mining era to dump mine tailings and mine-waste rock
that had been pulverized to remove sulfide ores directly into the rivers (von Guerard el al. 2007). By the
time mining ended, more than 8.6 million short tons of mill tailings and waste had been discharged directly
into the Animas River and its tributaries from the headwaters to Durango (Jones 2007). Substantial
amounts of the discarded wastes have been subsequently transported downstream and dispersed in stream
deposits (Church et al. 1997; UGSS 2007), while considerable amounts remain in place where they were
dumped.
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EPA Gold King Mine Biological Response Report
jrxr
irn
B)
MT5BT
WTW
ramr
13HB
EXPLAN ATI ON
Laic Tertian,' Incrustve recks
TertlaTy volcanic rocks
Tertiary and Late Cretaceous Intrusive rocks
Mctczofc and Fa icc-zolc sedimentary rocks
Precambrtan rocks
Contact
Faults and vt3n structures Efcished where
.TgjfioKlniaJcJy looted
SlIverxDn calden structural margin
Dolled where concealed
San Juan caldcra topographic margin
Approximate^ located. queried where
extent unaniaii
6 MILES
i11 i11 'i i11 I i1
a k -cv: te=;
>3T3D
Mineral
Figure 2.4. A) Generalized regional geology map of Animas River headwaters and surrounding regions near
Silverton, CO (from: USGS 2007). B) Aerial view of the Silverton caldera area and the three main tributaries to
the Animas River; Silverton is located in the center bottom of the image (Source: GoogleEarth).
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EPA Gold King Mine Biological Response Report
Metals concentrations in the bed sediments of the Animas and San Juan rivers reflect the metals
concentrations in soils and the underlying geology from which they are formed. A watershed view of
metals concentrations in soils, river sediments and water as well as aquatic life are shown for 4 metals
known to be important to aquatic life including Cu, Zn, Pb, Cd in Figures 2.5-2.8. Soil metal maps shown
in panel A of each figure were obtained from the USGS Mineralogy website that spatially maps soil
concentrations from compiled nationwide soil pit data.
Metals concentrations in the soils along the trace of the Animas and San Juan rivers range from among the
highest measured in the United States within the sulfide ores in the headwaters to the lowest generally
observed along the length of the San Juan River, especially where local lithology is dominated by
continentally deposited sedimentary rocks. The concentrations of most trace metals are at extreme values in
a circle centered within the Silverton caldera and the headwaters mining district. High metals
concentrations are not constrained to the caldera but radiate outward for some distance. Concentrations
decline sharply or gradually along the river path, depending on the metal. Soil concentrations reach
moderate levels at some point along the Animas River within the middle to lower Animas. Most, but not
all, trace metals show a similar pattern.
Available sediment and dissolved water data collected by various agencies in study of the river are shown
in panels B and C, respectively. River data are plotted with the horizontal axis reversed to match the
general east to west flow of the river. Sediment and water metal concentrations within the Animas decline
from high values observed in the impacted mining district by two to three orders of magnitude by the time
the Animas joins the San Juan River. This decline is due to dilution with water and sediments from
surrounding low concentration geologic formations, as well as transformation of dissolved metals to solid
forms from biogeochemical reactions in higher pH waters (Figure 2.2.C).
Metals in river sediments generally follow the same trajectory as those in soils in the river proximity
(Figure B in each panel). The trace of the midpoint of the soils concentration categories in panel A are
shown on the sediment graph (panel B). Metals in river bed sediments tend to be similar to those in the
soils in the San Juan River while river bed sediment concentrations exceed soil concentrations in the
Animas River. This could reflect the contamination of river sediments from mine waste disposal during the
first 70 years of mining activity (Church et al. 1997, 2007, Jones 2007).
Dissolved water concentrations are also high in the headwaters within the ore deposits and decline with
distance downstream. Dissolved concentrations vary over a wider range at a location reflecting the
importance of seasonal runoff and storm events that may mobilize metals sequestered in the stream bed.
Metals concentrations are generally similar through the length of the San Juan. Metals concentrations in the
San Juan are most strongly influenced by episodic stormflow and suspended sediment loads (EPA 2016c).
The wide range and systematic declining pattern of background metals in water and sediment in the
Animas River at the watershed scale identifies the general influence of environmental concentrations on
biological communities. Fish and aquatic invertebrates readily assimilate metals from their environment
(Elder 1989). While most research has focused on conditions within and immediately downstream of the
mining district, a few have studied metals in the environmental and biota downstream to determine the
extent of mining impacts throughout the Animas River (Church et al. 1997; Anderson 2007; MSI 2016).
The metals concentrations in aquatic organisms has been measured for lengthy portions of the Animas
River as part of environmental impact assessment for public projects (US Bureau of Reclamation 1996) and
risk assessments in support of mining-related remediation activities in the mining district (USGS 2007,
EPA 2015).
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EPA Gold King Mine Biological Response Report
A)
Copper (Cu) in Soil
EXPLANATION
Cu - A Horizon
PERCENTILE
mgAg
90 lo 100 ~
~ 33.7 to 280
80 to 90 ~
wm
" 23.8 to 33.7
70 to 80 ~
[ 19.9 to 23.8
80 to 70 ~
[ 17.1 to 199
50 to 60 ~
" 14.8 to 17.1
40 to 50
" 12.8 to 148
30 to 40 "
] 10.4 to 12 8
20 to 30 ~
m
] 7 8 to 10 4
10 to 20 ~
~ 51 to 7.8
OtolO
<0.5 to 51
* 5090 Outfier. concentration
in mg/kg
M_ake P
B)
< 100
oo
£
A Pre-GKM Event
-~-Soil
Saasaaa
Gfflasfeaoa
Dissolved Copper in Water
I
San Juan < Animas
San Juan < Animas
Copper in Sediment
D)
600 500 400 300 200 100
Distance from Headwaters (km)
Copper in Macro in vertebrate Tissue
15
150 100 50
Distance from Headwaters (km)
E)
500 400 300 200
Distance from Headwaters (km)
Copper in Fish Tissue
•1 4
1 1
2 - 3
o »
u ^
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EPA Gold King Mine Biological Response Report
A)
B)
Zinc in Sediment
.2?
£
E
Pre-GKM Event
Soil
Animas A ^
iiiw:
son Juan <
D)
600 500 400 300 200 100
Distance from Headwaters (km)
Zinc in Macroinvertebrate Tissue
200 150 100 50
Distance from Headwaters (km)
10,000
E)
80
2 %
! I
u >
40
2 E
3 20
Dissolved Zinc in Water
San Juan < Animas
500 400 300 200
Distance from Headwaters (km)
Zinc in Fish Tissue
~ Brook an d Brown Trout
X Rainbow trout
A
O Mottled sculpin
O
A
~ Flannelmouth sucker
O
~
A A
x g J
A
I i I I 1 I I I I 1
X
a
*
~
~
~
1 I i > I 1
200
150 100 50
Distance from Headwaters (km)
Figure 2.6. Longitudinal distribution of zinc (Zn) in A) soils, B) river bed sediment, C) river water, D) benthic
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996). Horizontal (distance)
axes are reversed to follow east to west path of river. Soils map was obtained from the US Geological Survey
Mineral Resources On-Line Spatial Data website (https://mrdata.usgs.gov/soilgeochemistry).
Below Silverton
|&akers"Bridge
EXPLANATION
Zn A Honron
^ ^ ^ tesa,
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EPA Gold King Mine Biological Response Report
B)
Lead in Sediment
10,000
A Pre-GKM Event
-•—Soil
San Juan < Animas
_ 1,000
D)
500 400 300 200
Distance from Headwaters (km)
Lead in Macroinvertebrate Tissue
2
10
00
E
8 -
c
o
%
6
c
a>
c
4
u
Q>
2 -
5*
P
0
200 150 100 SO
Distance from Headwaters (km)
E)
= "
O
2 S 2.0
c "£
a» >
£ ~ 1.5
o m
<
* 1.0
p 0.5
0.0
Dissolved Lead in Water
~ aa
a !
. . ! :r! hi J
A A i AA A J
500 400
Distance from Headwaters (km)
Lead, Pb
-A*
300 200 100
"] A Brook and Brown Trout
X Rainbow trout
—~
O Mottled sculpin
~ Flannelmouth sucker
~
°D
X
4 4
o
X
X
A
A
A
2
A
150 100 50
Distance from Headwaters (km)
Figure 2.7. Longitudinal distribution of lead (Pb) in A) soils, B) river bed sediment, C) river water, D) benthic
macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996). Horizontal (distance)
axes are reversed to follow east to west path of river. Soils map was obtained from the US Geological Survey
Mineral Resources On-Line Spatial Data website (https://mrdata.usgs.gov/soilgeochemistrv).
EXPLANATION
Pb • A Honron
Ptfl&NTUi
90 to 100
00 to 90
70 to 80
GO to 70
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EPA Gold King Mine Biological Response Report
Cadmium (Cd) in Soil
EXPLANATION
Cd - A Horizon
PERCENTILE
90 to 100
7010 90
40 to 70
30 to 40
0 to 30
mg/kq
0 5to 86
0.3 to as
02to0L3
01 to 0.2
<01 toll
'Hermosa, Creek
B)
C)
D)
1.4
1.2
E
1
o
0.8
ro
c
0.6
0J
§
0.4
QJ
0.2
3
0
Cadmium in Sediment
Pre-GKM Event
Soil
San Juan < Animas
500 400 300 200
Distance from Headwaters (km)
Cadmium in MacroinvertebrateTissue
200 150 100 50
Distance from Headwaters (km)
E)
1 i
I |
u >
0 °°
U
01 00
5 E
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Dissolved Cadmium in Water
Pre-GKM Event
San Juan < Animas
A
700 600 500 400 300 200 100 0
Distance from Headwaters (km)
Cadmium, Cd
1 A Brook and Brown Trout
J X Rainbow trout
" ~ "
j O Mottled sculpin
j ~ Flannelmouth sucker
O
~ ~
A A
i-i
~ *
* A
I
T a
s
1 I 1 1 1 1 1
150 100 50
Distance from Headwaters (km)
Figure 2.8. Longitudinal distribution of cadmium (Cd) in A) soils, B) river bed sediment, C) river water, D)
benthic macroinvertebrate tissue (MSI 2016) and E) fish tissue (US Bureau of Reclamation 1996). Horizontal
(distance) axes are reversed to follow east to west path of river. Soils map was obtained from the LJS
Geological Survey Mineral Resources On-Line Spatial Data website
(https://mrdata.usgs.gov/soilgeochemistry).
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EPA Gold King Mine Biological Response Report
Metals in fish tissue were sampled in the 1990's at multiple locations from the headwaters to Farmington,
NM for the U.S. Bureau of Reclamation La Plata Project Environmental Impact Assessment (US Bureau of
Reclamation 1996). Mountain Studies Institute (MSI) collected macroinvertebrate populations in the upper
and middle Animas in 2014, including metals in macroinvertebrate tissue (MSI 2016). Data from these
sources are shown with soil, sediment and water concentrations in panels D (macroinvertebrates) and E
(fish) in Figures 2.5-2.8. Note that tissue data were only available from the Animas River.
These surveys show that fish and macroinvertebrates in the Animas River assimilate metals and generally
had higher body burdens of copper, cadmium, and zinc in the headwaters of the Animas where
concentrations in water and sediment are greatest. Lead and arsenic (not shown) were present in
macroinvertebrates but not in fish. Highest concentrations of metals in benthic macroinvertebrates (peaks in
D panels) were sampled from the monitoring location upstream of Cement Creek (A68). Field studies have
also established that the number of taxa and abundance increase with distance downstream from the mining
district (Besser and Leib 2007, Anderson 2007). Increasingly healthy aquatic communities generally follow
the longitudinal trends towards lower water and sediment concentrations and body burdens moving
downstream from the mining district (Figure 2.3).
2.3.2 Metal toxicity to aquatic life in the Animas River
Metal toxicity and bioaccumulation in aquatic environments is complex, and is influenced by multiple
routes of exposure (diet and solution) and physiochemical characteristics that control bioavailability (e.g.,
temperature, pH, dissolved organic carbon, inorganic cations and anions) (Luoma 1983; Paquin el a I. 2002,
Luoma and Rainbow 2005). Although some metals are essential for life, all metals are toxic at sufficiently
high concentrations (Luoma 1983). Metals are partitioned between solid and dissolved phases in aquatic
environments. Free metal ions in the water are highly bioavailable and may be the most important control
on bioaccumulation and toxicity, especially for some metals including cadmium, copper, iron, manganese
and zinc (Luoma 1983). Dissolved metals cause acute toxicity to fish by exposure to the gill, which
damages gill tissue and alters gill function. Metal exposure also occurs through ingestion of particulates in
sediment and suspended particulates. Intake through digestion and biomagnification through the food chain
is an important exposure route for some metals including selenium and mercury (Luoma 1983). Generally,
dissolved metals are considered more toxic, more reactive, and more mobile than particulate metals.
Laboratory and field toxicity studies of aquatic communities in the mining impacted reaches of the upper
Animas (Besser and Leib 2007; Courtney and Clements 2022; EPA 2015) and elsewhere (Mebane etal.
2012, 2017, Cadmus et al. 2016) have shown that persistently high concentrations of metals in water,
sediment and food resources degrade benthic organisms and fish populations. The USGS Professional
Report 1651 (USGS 2007) summarizes the historic field sampling and toxicity testing in the upper Animas
in support of AMD remediation activities in the Bonita Peak district near Silverton, CO. The EPA has also
performed additional toxicity tests, extensive monitoring, and risk analysis for aquatic life in the upper
Animas River (EPA 2015).
The USGS studies in the Animas River concluded through field observations and supporting toxicity tests
that Cu had the main impact on trout, while zinc was most important for macroinvertebrates and amphipods
(Besser etal. 2007; Besser and Leib 2007). USGS studies also identified potential impacts from dissolved
aluminum and deposited Al and Fe oxides. Toxicity tests of upper Animas River water and sediment
performed by EPA (2015) identified potential effects from Al, As, Cd, Cu, Pb, Mn, Ni, Se, Ag, and Zn.
Both efforts documented that persistently high metal concentrations in the upper Animas River are toxic to
many taxonomic groups. The direct toxic effects of metals cause mortality, reduced growth, decreased
reproductive output, and eliminate sensitive species from the aquatic community. This results in reduced
diversity and abundance of benthic macroinvertebrates and fish (Besser and Leib 2007; Courtney and
Clements 2002). There is significant variation in sensitivity to metals among taxa and complex responses
within the biological community that result in high spatial and temporal variability within the aquatic
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EPA Gold King Mine Biological Response Report
community (Besser and Leib 2007). For example, results of an in situ toxicity test in the Animas River
presented by Courtney and Clements (2002) identified that the greatest toxic effects are observed on
mayflies (Heptageniidae, Ephemerellidae) and stoneflies (Taeniopterygidae). Furthermore, food abundance
and quality in the Animas River was found to be reduced compared to reference tributaries, which also
likely contributed to the absence of sensitive species (Courtney and Clements 2002). EPA (2015) found
that rainbow and brown trout were more sensitive to metal concentration measured in the Animas River
than brook trout.
Some macroinvertebrate studies have concluded that water exposure is the primary route of exposure in the
Animas River (Courtney and Clements 2002) while other studies have emphasized the importance of
dietary exposure from sediment and food resources (Besser and Leib 2007). Data from the Animas River
presented in Besser et al. (2001) show that there is a strong relationship between metal concentrations in
the pore water, metals in sediment, and metals in the periphyton and in some of the macroinvertebrate
species. They observed that there were high concentrations of metals in the periphyton and that these
concentrations tended to match those of sediment. The interrelationship between metal concentrations in
sediment and water blurs inference from general surveys of causative exposure factors.
2.4 Metal water quality criteria and sediment thresholds for aquatic life
Water quality criteria are limits on chemicals or conditions in a waterbody that are derived to protect the
designated uses for the waterbody, such as aquatic life use. Numeric criteria are defined by a magnitude,
duration, and frequency of exposure. Pursuant to section 304(a) of the Clean Water Act, the EPA publishes
national pollutant criteria recommendations to protect aquatic life. EPA aquatic life criteria include acute
(short-term, or 1 hour) and chronic exposure (long-term; 96 hour) recommendations for the protection of
aquatic life (https://www.epa.gov/wqc/national-recommended-water-qualitv-criteria-aquatic-life-criteria-
table). States and tribes with jurisdiction of the Animas and San Juan rivers have generally adopted EPA's
304(a) criteria recommendations, or updated versions of the EPA's recommendations that take into
consideration the most recent toxicity data.
Water quality criteria for aquatic life target exposure to dissolved metals. Research has shown that toxicity
of most metals varies with the presence of dissolved calcium and magnesium carbonates (hardness) which
compete for binding sites on the gill surface. This interaction results in hardness modified water quality
criteria recommendations. Because of changes in species and hardness along the length of the Animas and
San Juan rivers, water criteria vary spatially and temporally but are more likely to be exceeded in the upper
and middle Animas as geology produces inherently
higher metals concentrations, water relatively lower
hardness, and lower pH (Figure 2.3) that is conducive
to maintaining metals in the dissolved and more
bioavailable solid phases. Metals criteria can vary
widely over the applicable hardness range. For
example, at hardness concentrations 25 to 400 mg/L,
acute water quality criteria for dissolved cadmium and
zinc ranges from 0.5 to 6.5 (ig/L and 36 to 378 (ig/L,
respectively. There are no comparable EPA, state or
tribal criteria for sediment; however, sediment
probable effects concentrations (PECs) have been
used to evaluate risk of sediment metals to aquatic life
(Table 2.2), including use in the EPA BERA (EPA
2015). PECs are concentrations in sediment above
which adverse effects are expected to occur more
often than not (MacDonald et al. 2000).
Table 2.2. Sediment probable effects concentration
(PEC) benchmarks for aquatic life from MacDonald
et al. (2000).
Metal
Probable Effect
Concentration (mg/kg)
Aluminum
60,000
Arsenic
33
Cadmium
4.98
Copper
149
Iron
250,000
Lead
128
Manganese
1,200
Mercury
1.06
Nickel
48.6
Zinc
459
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EPA Gold King Mine Biological Response Report
Biota in some portions of the Animas River headwaters and its tributaries, and river segments immediately
downstream from the mining district, are impacted by metals and pH to some degree, but sustainably
support aquatic life (USGS 2007, EPA 2015). Since 1998, the State of Colorado has designated some
segments of the upper Animas River, including Cement Creek, as persistently impaired for certain metals,
including lead, iron and aluminum, and has followed procedures under the Clean Water Act to remove
aquatic life support as a designated use for the waterbody because it is not an attainable goal (Colorado
Department of Public Health & Environment, https://www.colorado.gov/pacific/cdphe/tmdl-san-iuan-and-
dolores-river-basins).
2.5 Gold King Mine release
The EPA Office of Research and Development (ORD) report Analysis of the Transport and Fate of Metals
Released from the Gold King Mine in the Animas and San Juan Rivers (EPA/600/R-16/296) provides a
detailed examination of the water chemistry and sediment data collected from the Animas and San Juan
rivers before, during and after the release (EPA 2016c). In that report, ORD used a combination of
empirical and modeled observations to describe the GKM plume as it traveled from Cement Creek to the
San Juan River. The GKM release had the potential to impact the biological communities in the Animas
and San Juan rivers through direct acute and chronic toxic effects typically associated with the dissolved
fraction of the total metal. Generally, dissolved metals are considered more toxic, more reactive, and more
mobile than particulate metals. Physiological effects can also be observed with the deposition of metal-
bearing colloids that have a smothering effect on organisms and degrade aquatic habitat. Below we
summarize the key findings in the EPA ORD report that provide insight to the biological results (see the
full ORD report for all key findings).
2.5.1 GKM plume water chemistry
The GKM plume1 was generally characterized by metals concentrations that rose abruptly, peaked quickly
and fell rapidly within a period of about 12 hours as the central core of the plume moved past locations
within the watershed. Concentrations in the downstream rivers then tapered back towards pre-event levels
over days to weeks after the passing of the plume.
Once the GKM plume entered the Animas River, both dissolved and colloidal/particulate peak metals
concentrations began to decline rapidly (e.g., within ~ 12 hours) as chemical reactions and hydraulic
processes diluted, transformed, and deposited material. As the plume travelled, chemical transformations of
dissolved metals began as soon as the acidic GKM plume mixed with the more alkaline waters of the
Animas River at Silverton. As the plume traveled, acidity was neutralized and pH increased through
hydrolysis chemical reactions that consumed hydrogen ions and stimulated the formation of iron,
aluminum, and manganese hydr(oxides) and other incipient minerals. The incipient amorphous minerals
that formed as the plume flowed included colloids, precipitates, and adsorbed phases that sequestered the
trace metals including lead, copper, arsenic, zinc and others. The iron and aluminum reacted with the river
water to cause the characteristic bright yellow color that was visible for days as the plume traveled down
the river system.
Dilution of the GKM plume with river water also began as soon as it flowed into the larger Animas River
and then shortly joined Mineral Creek in the Silverton area. Within 4 km distance of travel the plume was
diluted to 38% of its original strength. Dilution reduced initial plume concentrations to 18% by Durango,
95 kilometers from the Gold King mine, and 15% by Farmington, 190 km from the source. Although the
plume was visually similar as it traveled through the Animas River, no two places along the river
experienced exactly the same plume when measured by the concentration or form of metals in the water.
1 In this document, we use GKM plume when discussing the eight-day period when the released metals traveled
through the Animas and San Juan rivers. GKM release is also used when discussing the entire event, including the
months after the plume when GKM deposits were present in the watershed.
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EPA Gold King Mine Biological Response Report
As the aluminum and iron hydro(oxide) minerals formed between Silverton and Durango, some remained
suspended in the water; some precipitated and settled to the river bed in slower waters along the edge and
bottom of the channel, in side channels, and behind flow obstructions; and some adhered or cohered to
rocks. By the time the GKM plume reached its confluence with the San Juan River, total metal
concentrations in the water had declined by 3 orders of magnitude from what they were when the plume
entered the Animas (Figure 2.9).
Summed Total Metals, Minus Major Cations - Animas River
100,000.0
10,000.0
RK16.4, 11,583
RK 63.8, 521 -RK94.
RK 12.5
RK 16.4
RK 63.8
RK 94.2
RK 131.5
RK 164.1
RK 190.2
• Observed
1,000.0
100.0
1.0 j
0.1
8/5 0:00
8/8 0:00
8/9 0:00
RK 12.5, 39,683
2, 214.2
Observed
RK 131.5,103.1 Aug 5-Aug 11,2015
- RK 164.1, 62.1
RK 190.2,40.1
8/6 0:00 8/7 0:00
8/10 0:00 8/110:00
Date
Figure 2.9. Observed and empirically-modeled summed total metals minus major cations, in the Animas River
as the GKM plume passed from August 5-10, 2015 (from EPA 2016c).
Photo series showing the daily progression of waste*
viewed from Trimble Bridge in Durango. Colorado
wastewater from the Gold King mine spill moving downstream via the Animas River as
(August 6 - August 20. 2016). Photos courtesy of the Joint Information Center.
Photo from CDPHE (2016a)
2.5.2 GKM sediment deposits
Only 10% of the GKM release reached Lake Powell with the plume. The other 90% was deposited onto the
streambed along the length of the Animas and San Juan rivers (Figure 2.10), where it remained in place for
various lengths of time depending on location (i.e., 3 weeks to 10 months). Subsequent effects on the
biological communities could occur from chronic exposures to metals sequestered in the streambed.
Freshly-deposited sediments dominated by iron and aluminum hydrous oxides are likely to be highly
enriched with other more toxic metals, and may form a reservoir contributing to longer-term effects on
stream biota. Any toxicity associated with the deposits should decline over time as they age.
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EPA Gold King Mine Biological Response Report
Deposition of Gold King Mine Release Metals Mass
1,000 .
"O
San Juan
0
0
100
200
300
400
500
600
Distance from Headwaters (km)
Figure 2.10. Estimated deposited mass of metals from the GKM release as it passed through the Animas and
San Juan rivers. Deposited mass was estimated in 2-km segments of river by the Water Analysis Simulation
Program (WASP) model as reported in the EPA GKM release fate and transport study (EPA 2016c).
Eighty percent of the GKM release (-390,000 kg) was deposited in the Animas River between Silverton
and Durango. This portion of the river also stores a large amount of legacy contamination from historic
mine ore processing and ongoing acid mine drainage contamination (Church et cil. 1997; 2007), to which
the GKM release added new material. The high concentrations of metals evident in Figures 2.5-2.8 reflect
natural and mining related deposits in this river segment. GKM deposits in the Animas from the
Colorado/New Mexico border northward to Silverton largely remained in place until 2016 snowmelt runoff
began, as there were no storm events large enough to move them through Fall 2015.
The mass of the GKM metal deposits amounted to 10% of the metal mass that already contaminated the
upper and middle Animas river. Targeted sampling of GKM deposits had high concentrations of metals.
Samples representative of the general deposition observed on the riverbed collected in the months after the
GKM release were not statistically different from pre-event concentrations where there were sufficient data
for comparison (EPA 2016c; Rodriguez-Freire et ctl. 2016). Dissolved metals in river water were
statistically lower in the upper Animas in the months following the GKM-event, possibly due to their
adsorption onto the new deposits.
An additional 5% of the released metals (-25,000 kg) was deposited in the lower Animas River within New
Mexico. Sediment metal concentrations measured in the reach from RKM 152 south of Cedar Hill, NM, to
RKM 162 near Aztec, NM, were elevated after the GKM plume passed, as shown in Figure 2.11. Lead and
zinc in the sediments exceeded recommended PECs for aquatic life (Table 2.2) within this reach for a time
after the plume passed. Another 5% of the released mass may have deposited along the length of the San
Juan River, but sediment samples only showed some evidence of this from Farmington (RKM 196) to
Fruitland, NM (RKM 214). Deposits in the lower Animas and San Juan rivers remained in place for 3
weeks until they were mobilized during a monsoonal event and delivered to Lake Powell. Sediment
samples collected after the event unambiguously showed that the concentrations of all metals in the
sediments of both rivers were at background levels following the storm.
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EPA Gold King Mine Biological Response Report
% % % % % % %
Animas River ][ San Juan River
Distance from GKM (km)
Lead in Sediment
» ' Awi age When GKM deposits present (8/11/2U1S to H/l f/iQl'i)
Maximum rtui ing GKM deposit period (8/11 to R/27)
lUckground (Aug 30 2015 toM^rdi lb. 2016)
'<& % % '<& % % % % % %
Animas River ]( San Juan River
Distance from GKM (km)
Copper in Sediment
i 1 Average When GKM deposits present (8/11/2015 to 8/27/2015)
Maximum during GKM deposit period (8/11 to 8/27)
Background (Aug 30 2015 to March 16,2016)
Fish Sampling Locations
450
~ BOO
a
£ 250
S 200
U
50
0
Cadmium in Sediment
' Average When GKM deposits present (8/11/2015 to 8/27/2015)
Maximum during GKM deposit period (8/11 to 8/27)
Background (Aug 30 2015 to March 16, 2016)
¦ Fish Sampling Locations
\
Animas River ][ San Juan River
Distance from GKM (km)
Manganese in Sediment
H Average When GKM deposits present (8/11/2015 to 8/27/2015)
- Maximum during GKM deposit period (8/11 to 8/27)
- Background (Aug 30 2015 to March 16, 2016)
Fish Sampling Locations
5,000
-i Sol'-
= 3,000
c 2.500
2,000
c 1,500
1,000
'-i> % \ % %
Animas River ][ San Juan River
Distance from GKM (km)
% %
1.0
0.5
Selenium in Sediment
~ Average When GKM deposits present (8/11/2015 to 8/27/2015)
- Maximum during GKM deposit period (8/11 to 8/27)
- Background (Aug 30 2015 to March 16,2016)
Fish Sampling Locations
<$. \ \ % \ % % %
Animas River )[ San Juan River
Distance from GKM (km)
%
Figure 2.11. Concentrations of copper, lead, cadmium, manganese and selenium in sediment at the time of
benthic macroinvertebrate (Chapter 7) and fish tissue sampling (Chapter 8) in the New Mexico segments of
the Animas and San Juan rivers. The post-GKM period includes data collected from August 8 to August 27,
2015. March 2016 represents background concentrations. Black squares on the sediment figures indicate the
location of fish sampling and the sites shown for water concentration.
2.5.3 GKM release water quality effects to aquatic life
For most metals, the peak concentrations that were observed as the GKM plume moved through the system
were not greater than aquatic life water quality criteria at most locations in the Animas or San Juan rivers.
Given the predominance of colloidal/particulate metals in the plume, criteria based on total concentration
were exceeded more often than those based on the dissolved fraction. Because of the short duration of the
plume, aquatic life was more vulnerable to acute, shorter-term concentrations during movement of the
plume itself. Most of the observed exc ursions were associated with the state acute aquatic life criteria for
aluminum. Excursions of acute aluminum criteria occurred throughout the Animas River and in the San
Juan River down to Shiprock, NM (296 RKM). The frequency of the excursions varied due to the change in
concentration and differences in the state and tribal water quality criteria for aluminum. The mainstem of
the Animas immediately below Silverton experienced the most excursions of metals criteria including acute
24
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EPA Gold King Mine Biological Response Report
aluminum, cadmium, copper, lead, manganese, and zinc. Within the spatial trend of declining
concentrations with distance, variation in excursions reflected the differences in criteria among states and
tribes along the route. The duration of water quality exceedances was generally associated with the core of
the plume where concentrations were highest and lasted several hours.2 For example, total and dissolved
metals concentrations in the Animas River are shown as the plume passed through Durango in Figure 2.12.
At this location, concentrations of several metals were briefly close to, but did not exceed, the acute aquatic
life criteria that are based on the dissolved concentration. Aluminum was the exception given the high total
recoverable concentrations and the criterion is based on total recoverable, rather than dissolved
concentration.
Metal Concentrations August 5-10, 2015 in the Animas River at Durango, CO
Copper, Cu
Total
Hi Dissolved
Acute Criteria: Dissolved
----Chronic Criteria: Dissolved
Zinc, Zn
Total
Dissolved
Acute Criteria: Dissolved
- - - • Chronic Criteria: Dissolved
— 1,000
8/5 20:50 8/6 20:20 8/7 0:30 8/7 14:35 8/8 19:45 8/9 12:25 8/9 20:00
8/5 20:50 8/6 20:20 8/7 0:30 8/714:35 8/819:45 8/912:25 8/9 20:00
Cadmium, Cd
Lead, Pb
Total Dissolved Acute Criteria: Dissolved - - - • Chronic Criteria: Dissolved
0.10
10,000.00 —
_ 1,000.00
1
Total
¦¦ Dissolved
Acute Criteria: Dissolved
- — — -ChronicCriteria: Dissolved
8/5 20:50 8/6 20:20 8/7 0:30 8/714:35 8/8 19:45 8/9 12:25 8/9 20:00
8/5 20:50 8/6 20:20 8/7 0:30 8/714:35 8/8 19:45 8/9 12:25 8/9 20:00
Aluminum, Al
Total
Dissolved
Acute Criteria: Total Recoverable
-Chronic Criteria: Total Recoverable
10,000
-= 1,000
Manganese, Mn
I Total
Dissolved
A
Acute Criteria: Dissolved
ML
— — — - Chronic Criteria: Dissolved
Aug 6
V —
> Aug 7
> Aug 8 > Aug 9 > Aug 10
20:50 8/6 20:20 8/7 0:30 8/7 14:35 8/8 19:45 8/9 12:25 8/9 20:00
8/5 20:50 8/6 20:20 8/7 0:30 8/7 14:35 8/8 19:45 8/9 12:25 8/9 20:00
Figure 2.12. Total and dissolved water concentrations of four metals in the Animas River at Durango, CO from
August 5-10, 2015 as the GKM plume passed through. Conditions represent the metal exposure during the
CPW sentential caged trout study presented in Chapter 6. Acute and chronic water quality criteria are shown
as solid and dashed red lines.
2 Aquatic life criteria duration varies among the states and tribes water quality standards. The EPA's 304(a) aquatic
life criteria recommendation for most metals is 1 hour for acute criteria and 96 hours for chronic criteria. The longest
duration of exceedance for chronic criteria was 44 hours for iron concentrations measured at RKM 132. See Tables 7-
5 through 7-8 in EPA (2016c) for additional details.
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EPA Gold King Mine Biological Response Report
2.5.4 GKM release exposure to aquatic life relative to background conditions
EPA, states, and tribes began monitoring metals in water and river bed sediments throughout the affected
rivers to assess risk to public and aquatic health as benchmarked by the water quality criteria. Monitoring
agencies collected samples over varying intervals, beginning at six-hours prior to the front end of the
plume, and continuing daily or weekly during later phases over the next year. We evaluated the metal
exposure to aquatic life before, during, and in the year following the event by comparing measured
concentrations to protective water and sediment benchmarks. Exposure identified in a single sample was
measured with a Hazard Quotient (HQ).
HQ = Observed Concentration/Benchmark Concentration
Where the benchmark was EPA's acute or chronic aquatic life criteria recommendation calculated at the
ambient water hardness or at hardness = 400 mg/L when hardness was greater than 400 mg/L for water or
the PEC for sediment (Table 2.2). This calculation for a single sample defines the magnitude but not the
duration of exposure. HQs equal to or greater than 1.0 for an individual sample identify a potential for
ecological risk in that established thresholds have been exceeded at that location. Samples with an HQ less
than 1 do not indicate a potential risk.
Acute and chronic HQ's calculated for pre-event, during and immediately after the event (the plume up to
1-month post release), and post event (2 months to 1 year following the GKM release) are shown in Figures
2.13 and 2.14, respectively. HQs for sediment are shown in Figure 2.15. The pre-event HQs were
calculated using the same concentration data shown in earlier Figures 2.5-2.8. Figures 2.13 through 2.15
represent nearly 4,000 samples collected before and after the event.
Acute and chronic HQs greater than 1 occurred frequently in the Animas headwaters within about 40 km
from GKM for most metals both before and after the release (Figures 2.13 and 2.14). Generally, HQs for all
metals followed similar longitudinal patterns and remained within the same range of variability at a
location before and after the GKM release.
Outside the Animas headwaters, acute HQs greater than 1 for all metals were rare. Chronic HQs greater
than 1 were frequently observed for zinc and lead throughout the system. Chronic HQs greater than 1 in the
lower Animas occur with high flow events typically associated with monsoonal storms. Lead HQs greater
than 1 in the San Juan are associated with mobilization of dissolved lead from the bed sediments during
monsoonal storms.
Sediment HQs after the GKM release were the same magnitude as prior to the release except for lead
(Figure 2.15). Lead was elevated in sediment from 50 to 200 km distance from headwaters (Bakers Bridge
to Farmington) during the immediate 1 -month period after the event (also shown in Figure 2.11), and
greater than the sediment PEC.
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EPA Gold King Mine Biological Response Report
Aquatic Acute Hazard Quotient
Copper, Cu
• Post A Immediate C3 Pre-event
1000.000
100.000
10.000
a i.ooo
0.100
0.010
0.001
* a*
Animas > San Juan
100 200 300 400 500
Distance from Headwaters (km)
600
700
Aquatic Acute Hazard Quotient
Zinc, Zn
• Post A Immediate ~ Pre-event
10.000
* 1.000
n 0.100
0.010
0.001
100 200 300 400 500 600 700
Distance from Headwaters (km)
10.000
o.ioo
Aquatic Acute Hazard Quotient
Cadmium, Cd
• Post A Immediate ~ Pre-event
Animas ^
Son Juan
0 100 200 300 400 500 600 700
Distance from Headwaters (km)
Aquatic Acute Hazard Quotient
Lead, Pb
• Post A Immediate n Pre-event
100.0000
10.0000
5 1.0000
a o.iooo
* o.oioo
o.ooio
A:hir.c;>
0.0001
200 300 400 500
Distance from Headwaters(km)
Figure-2.13. Acute aquatic life hazard quotients (HQ) for water samples collected from the Animas and San Juan rivers. The HQ was computed
as observed concentration divided by the acute water quality criterion. An HQ greater than 1 indicates the water quality benchmark was
exceeded. Pre-event samples were collected for several decades prior to the GKM release and include the same data shown in Figures 2.5 -2.8.
Immediate samples were collected from August 5 to August 28, 2015. Post samples were collected from September 2015 to September 2016.
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EPA Gold King Mine Biological Response Report
Aquatic Chronic Hazard Quotient
Copper, Cu
• Post a Immediate ~ Pre-event
10.000
0.100
"fSI 1 I I I
Animas > San Juan
100 200 300 400 500
Distance from Headwaters (km)
Aquatic Chronic Hazard Quotient
Cadmium, Cd
• Post a Immediate ~ Pre-event
600
700
1.000
0.100
0.001
Animas > San Juan
200 300 400 500
Distance from Headwaters (km)
Aquatic Chronic Hazard Quotient
Zinc, Zn
• Post a immediate ~ Pre-event
100.000
10.000
1.000
¦ 0.100
0.010
Animas > San Juan
' I*
0.001
100 200 300 400 500
Distance from Headwaters (km)
Aquatic Chronic Hazard Quotient
Lead, Pb
• Post a Immediate ~ Pre-event
600
700
~ 1.000
o
3
a
o.ooi
&ft
Animas > San Juan
100
200 300 400 500
Distance from Headwaters (km)
600
700
Figure-2.14. Chronic aquatic life hazard quotients (HQ) for water samples collected from the Animas and San Juan rivers. The HQ is computed as
observed concentration divided by the chronic water quality criterion. A value greater than 1 indicates the criterion was exceeded. Pre-event samples
were collected for several decades prior to the GKM release and include the same data shown in Figures 2.5-2.8. Immediate samples were collected
from August 5 to August 28, 2015. Post samples were collected from September 2015 to September 2016.
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EPA Gold King Mine Biological Response Report
10.000
1.000
Sediment Hazard Quotient
Copper, Cu
• Post a Immediate ~ Pre-event
o
=j
cr
0.100
0.010
0.001
A A
Animas > San Juan
100 200 300 400 500
Distance from Headwaters (km)
Sediment Hazard Quotient
Cadmium, Cd
• Post a Immediate ~ Pre-event
600
700
0 0.100
Animas > San Juan
100 200 300 400 500 600 700
Distance from Headwaters (km)
Sediment Hazard Quotient
Zinc, Zn
• Post a Immediate ~ Pre-event
1.000
H 0.100
0.010
• £ aa
A
Animas > San Juan
100 200 300 400 500 600 700
Distance from Headwaters (km)
Sediment Hazard Quotient
Lead, Pb
• Post a Immediate ~ Pre-event
k*
10.000
•n 1.000
5 0.100
0.010
~ ~
Animas > San Juan
• a
a—n~
Ml s
200 300 400 500
Distance from Headwaters (km)
Figure 2.15. Hazard quotient (HQ) for sediment probable effects concentrations (PECs) for water samples in the Animas and San Juan Rivers. The HQ
is computed as observed concentration divided by the water quality criteria. A value greater than 1 indicates the water quality criteria was
exceeded. Pre-event samples were collected for several decades prior to the GKM release and include the same data shown in Figures 2.5-2.8.
Immediate samples were collected from August 5 to August 28, 2015. Post samples were collected from September 2015 to September 2016.
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EPA Gold King Mine Biological Response Report
2.5.5 Metals in water and sediment return to background
The mass of metals in the GKM release was removed from the Animas and San Juan rivers and delivered to
Lake Powell in three primary events distributed over a 10-month period or the end of snow melt in 2016
(EPA 2016c). The first mass arrived with the plume approximately 8 to 9 days after the release. The second
event was triggered by a series of monsoonal storms that began in late August 2015 described in Section
2.5.2. The storm flow resulting from three inches of rain in a few hours during this event resuspended
GKM deposits in the Animas River below Cedar Hill, CO (RKM 140) to the confluence with the San Juan
River in Farmington, NM (RKM 193) as well as the entire length of the San Juan River. The third event
was associated with snowmelt runoff in 2016 that mobilized the remaining deposits in the Animas River
over the winter months.
EPA was able to isolate the GKM release metals from background metals in water and sediment in these
events and all data collected a year following the release with a metal "fingerprinting" technique (EPA
2016c). This technique associated the concentration of trace metals to that of aluminum or iron as
representative of the dominant metals in the geologic substrate and the soils and sediments that weather
from them. Water and sediment have typical relationships for each metal that have a strong central
tendency over a range of background sediment levels explained by the elemental composition in the
regional geology, as shown in Figures 2.5-2.8. If the trace metal ratio deviates from the central tendency,
another source of contamination is suggested. The "fingerprinting" technique was particularly effective in
detecting GKM release metals within the background concentrations of the San Juan River and was used to
account for the GKM mass and track its movement through the river during the GKM plume and in the
year following.
While water and sediment was extensively monitored for up to 1 year following the GKM event, various
organizations conducted biological studies to evaluate potential impacts of the GKM event on the river
biota. Sentinel studies of immediate survival of macroinvertebrates and fish as the plume passed were
conducted near Durango, CO. Longer term studies included sampling 7-months post event period when
GKM deposits were in place in Colorado and the lower Animas in New Mexico. EPA followed up with a
river-wide survey of macroinvertebrates and fish tissue a year following the event in 2016 to assess for
potential long-term impacts to aquatic life. EPA's response sampling was the first time the biological
communities were sampled through the entire length of the Animas/San Juan river system.
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EPA Gold King Mine Biological Response Report
CHAPTER 3 OBJECTIVES, DATA, METHODS, AND ANALYSIS APPROACH
FOR ASSESSMENT OF BIOLOGICAL DATA IN ASSOCIATION
WITH THE GKM RELEASE
3.1 Study objectives
Aquatic biological communities provide a measure of river
condition by responding to sudden changes in water quality,
such as the plume of metals that moved through the rivers
following the GKM release, and integrating persistent
stressors over time, such as the legacy mining and ongoing
acid mine drainage in the upper Animas watershed. Aquatic
community condition is also a core measure of aquatic life
use support in a given waterbody.
The EPA's primary objective was to gather and review all
readily available biological data collected from the San Juan
and Animas rivers to assess how the aquatic biota
responded to the GKM release. Data gathered for this
analysis included the EPA response sampling that targeted
the near-term biological conditions immediately following
the release (fall 2015) when deposits were still present in
the Animas River and the long-term biological conditions
occurring after the deposits have moved through the river
system (fall 2016). Data collected by state and tribal
partners were also included in our analyses. The sampling
and analysis approach was designed to evaluate potential
changes in the species compositions, population abundance,
and the concentration of metals in the tissue by comparing
the post-GKM release data to the pre-release conditions,
when available. In many instances and particularly on the
lower Animas and San Juan rivers, pre-release data were
less available for pre- and post-GKM comparisons.
Monitoring and assessment efforts occurring prior to the
GKM release identify pre-existing adverse impacts to water
quality, sediment quality, and biological communities in
this watershed (Besser etal. 2001; USGS 2007). Numerous
sources of metals contamination are present within the watershed that have impacted environmental quality
before the GKM release and continue to impact environmental quality post-GKM release (Chapter 2).
Therefore, our ability to determine if current environmental impacts relate to the GKM release is
confounded by the presence of on-going AMD sources in the upper watershed. Typical biological
conditions in many areas of this watershed are neither pristine nor free of impairments. New data gathered
post-GKM release are best understood by a comparison to previous conditions. It is well established that
the historic and ongoing AMD in the upper Animas River has resulted in degraded benthic
macroinvertebrate assemblages and portions of mainstem and tributaries that have not supported permanent
fish populations (Anderson 2007, Besser and Leib 2007). Moving away from the historic mining
operations, fish populations and benthic macroinvertebrate assemblages improve in the middle Animas.
Metal concentrations decrease yet continue to be one of many stressors typically associated with more
developed areas of watershed (CPW 2010). The aquatic communities in the lower Animas River and the
HOW DID THE AQUATIC
COMMUNITY, POPULATIONS,
AND METAL SEQUESTRATION
IN TISSUE RESPOND TO THE
GKM RELEASE?
• Did the GKM release add to
biological degradation in the
already contaminated upper
Animas River?
• Did the GKM release degrade
biological communities in other
segments of the Animas and San
Juan rivers that had not been
known to have metal-
contamination?
• Were acute impacts to the
biological communities observed
during the initial GKM release
when metals concentrations were
highest?
• Were long-term changes in
biological communities observed
a year after the GKM release?
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EPA Gold King Mine Biological Response Report
San Juan, on the other hand, are not known to be persistently disturbed by the AMD in the headwaters.
Therefore, the primary assessment objective was to compare the pre-release/historic and post-GKM release
biological data of the Animas River and San Juan River.
Our secondary objective was to present a watershed-wide analysis of all biological data collected from the
GKM release impacted areas of the San Juan and Animas rivers, regardless of existing historic data for
comparison. In this effort, we identified similarities and differences in existing state and tribal field
collection methods and assessment approaches. This information can be used to inform future monitoring
efforts in the San Juan watershed.
3.2 Sampling design
EPA mobilized field crews to sample water and sediment immediately after the GKM release occurred.
Rivers impacted by the GKM release include the Animas River near Silverton, CO to its confluence with
the San Juan River in Farmington, NM (190 RKM) and the San Juan River from the Animas confluence to
Lake Powell in Utah (-650 RKM). The EPA identified 30 monitoring locations along Cement Creek,
Mineral Creek, the Animas River, and the San Juan River based upon state, tribal or local interest; locations
used in the emergency response; and long-term or pre-release data availability (Figures 3.1 and 3.2; Table
3.1). Sites that were not impacted by the GKM release were also sampled for a measure of background
conditions in the watershed.
EPA targeted the response biological data collection (near-term sampling) at 22 sites in the fall of 2015 and
expanded the follow-up data collection (long-term sampling) to 29 sites in the fall of 2016. In 2015, the
EPA and contractors collected benthic macroinvertebrate samples at 4 locations from the Animas River
within a week following the release (8/12 and 8/13) and at 18 locations in September and October (Table
3.1). The EPA was unable to sample all sites identified in the its follow-up monitoring plan for biology
prior to the onset of winter conditions and exceedance of the index period for biological sampling in the fall
of 2015. In 2016, EPA and contractors implemented the full biological sampling design with Superfund
Technical Assessment and Response Team (START) contractor support and collected benthic
macroinvertebrate samples and tissue samples at 29 sites, including 1 site on the Animas River upstream of
Cement Creek (A68), 2 tributaries in the upper Animas River watershed (Cement Creek and Mineral
Creek), 17 locations on the mainstem of the Animas. San Juan River sampling included 1 location on the
mainstream upstream of the Animas confluence (SJAR) and 9 locations on the mainstem of the San Juan
River downstream of the confluence. Additional details on EPA GKM field events are found in EPA's
Field Activities Report (to be posted at https://www.epa.gov/goldkingmine).
In addition to the response and follow-up biological data collected by EPA, we issued a request for
biological data collected by state, tribal, local, and federal partners. Data providers included Colorado Parks
and Wildlife (CPW), Colorado Department of Public Health and Environment (CDPHE), New Mexico
Environment Department (NMED), New Mexico Department of Game and Fish (NMDGF), Southern Ute
Indian Tribe (SUIT), Navajo Nation Environmental Protection Agency (NNEPA), and U.S. Fish and
Wildlife Service (USFWS). The type of biological data, sampling dates, and locations of this additional
data are included in Table 3.1. When data providers used different location IDs or sampled slightly
different locations than those sampled by EPA, we reviewed the sampling coordinates and site descriptions
to determine if the locations generally represent a similar section of the river. When locations were similar
(e.g., aquatic habitat, no new sources or tributaries), GKM location IDs were assigned to facilitate
comparisons of the post-GKM release data with historic sampling sites (Appendix A). Differences in field
and analytical methods used by the various data providers are identified in the Section 3.4 and were taken
into consideration when developing our approach to the data analysis. Datasets were analyzed collectively
when methods were similar and, when possible, results are presented consistent with the state/tribal
analysis tools.
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EPA Gold King Mine Biological Response Report
Cemenf
Colorado
Silverton
Ute Mountain f
Ute TribLy
^Reservation/
Tacoma
SJMC
Duran,go
Southern £ Ute
Indian • Reservation
SJCH
iJte Mountain Ute
Tribe Reservation
Mexican Hat
SJ4C
SJMH
ADW-022
Four Corners
ADW-021
Navajo Nation
SjsR^Farmjngton
Shiprock
fsjFPr^Fruitland/y
SJAR
SJLP
Arizona
New Mexico
Legend
# Gold King Mine
~ City
O Sampling Site
A Reference Sampling Site
— Stream
Impacted Stream
Animas Watershed
Indian Land
State Boundary
Utah
FW-012
Figure 3.1. Locations sampled by EPA for surface water, sediment, physical habitat and biology in the Animas and San Juan rivers following the GKM release.
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EPA Gold King Mine Biological Response Report
CC48
Silverton
A75D
Tacoma
GKM05
Southern Ute
Indian Reservation
New Mexico
Legend
Gold King Mine
~ city
• Sampling Site
A Reference Sampling Site
Impacted Stream
Indian Land
Stream
Animas Watershed
I I State Boundary
Cement
Creek
| Bakers Bridge
Colorado
s w
"5 £
C M
i 2
-&He
3 H>.
Oxbow Park
132nd St Bridge
"Durango )
Figure 3.2. EPA sampling locations for biological data in the upper and middle Animas River following the GKM
release.
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EPA Gold King Mine Biological Response Report
Table 3.1. Sampling locations and dates for biological and physical habitat data collected by the EPA, EPA contractors, states, tribes and federal partners during
the GKM-plume through spring 2017. Pre = pre-release data available for this location within the period of record (upper Animas = 2005-8/5/2015; middle and
lower Animas and the San Juan = 2000-arrival of the plume). NS = not sampled. * identifies locations that were not impacted by the release and were sampled
to characterize background ** identifies locations that were only sampled for biology by state and/or tribal partners. See Appendix A of this report for location
descriptions and EPA's Field Activities Report for additional details on the EPA's sampling efforts.
Location
Distance
from GKM
Latitude
Longitude
Benthic
Macroinvertebrate
Assemblage
Benthic
Macroinvertebrate
Tissue
Fish
Tissue
Physical
Habitat
(KM)
Pre
Pre
Pre
Upper Animas River and Tributaries
CC48
12.54
37.818115
-107.661678
Yes
8/23/16
9/27/16
No
9/27/16
No
NS
Fall 2016
A68*
13.9
37.810983
-107.65936
Yes
8/8/15
8/12/15
9/23/15
8/23/16
9/27/16
Yes
9/23/15
9/27/16
No
10/30/16
Fall 2016
M34*
15.14
37.802921
-107.672724
Yes
8/23/16
9/27/16
Yes
9/27/16
No
NS
Fall 2016
A72
16.4
37.790017
-107.667536
Yes
8/8/15
8/12/15
9/23/15
8/23/16
9/27/16
Yes
9/23/15
9/27/16
No
NS
Fall 2016
A73
24.5
37.72215833
-107.6548278
No
10/15/15
8/26/16
10/3/16
Yes
10/15/15
10/3/16
No
10/31/16
NS
A75D
45.1
37.59793424
-107.775326
Yes
10/15/15
8/26/16
10/3/16
Yes
10/15/15
10/3/16
No
10/31/16
NS
Bakers Bridge
64.0
37.455731
-107.801095
Yes
9/21/15
8/22/16
9/29/16
Yes
9/21/15
9/29/16
No
11/1/16
Fall 2016
Middle Animas
James Ranch**
67.1
37.417822
-107.814819
Yes
9/21/15
No
9/21/15
No
NS
NS
9426
76.8
37.385148
-107.836946
Yes
10/29/15
8/22/16
9/29/16
No
9/29/16
No
11/1/16
Fall 2016
Oxbow Park
89.8
37.308898
-107.855793
No
9/18/15
No
9/18/15
No
NS
NS
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EPA Gold King Mine Biological Response Report
Location
Distance
from GKM
Latitude
Longitude
Benthic
Macroinvertebrate
Assemblage
Benthic
Macroinvertebrate
Tissue
Fish
Tissue
Physical
Habitat
(KM)
Pre
Pre
Pre
Middle Animas River
32nd Street Bridge
91.8
37.294805
-107.870469
Yes
8/6/15
8/7/15
8/13/15
9/22/15
8/22/16
9/28/16
No
9/22/15
9/28/16
No
11/1/16
Fall 2016
Animas Rotary Park
94.2
37.280534
-107.876622
Yes
8/6/15
8/7/15
8/13/15
9/20/15
8/22/16
9/28/16
No
9/20/15
9/28/16
No
11/3/16
NS
Above Lightner
96.0
37.26892921
-107.8862952
Yes
9/20/15
No
NS
No
NS
NS
GKM05
96.5
37.268704
-107.885857
No
10/27/15
8/25/16
9/30/16
No
9/20/15
9/30/16
No
8/14/15
3/18/16
11/3/16
Fall 2016
AR19-3
104
37.221297
-107.859598
Yes
8/6/15
8/10/15
9/22/15
9/2/16
10/4/16
No
9/22/15
10/4/16
Yes
11/2/16
Fall 2016
AR16-0**
109
37.187031
-107.869928
Yes
8/6/15
8/10/15
8/22/16
No
NS
No
NS
NS
AR7-2
123
37.085161
-107.879233
Yes
8/10/15
10/28/15
9/2/16
10/4/16
No
10/4/16
No
11/2/16
Fall 2016
AR2-7
131
37.032292
-107.875455
Yes
8/10/15
8/22/15
10/28/15
9/2/16
10/4/16
No
10/4/16
Yes
11/2/16
Fall 2016
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EPA Gold King Mine Biological Response Report
Location
Distance
from GKM
Latitude
Longitude
Benthic
Macroinvertebrate
Assemblage
Benthic
Macroinvertebrate
Tissue
Fish
Tissue
Physical
Habitat
(KM)
Pre
Pre
Pre
Lower Animas River
ADW-022
148
36.933295
-107.909073
No
10/28/15
8/24/16
9/2/16
9/30/16
No
8/2015
3/2016
9/30/16
No
8/2015
3/2016
4/19/17
Fall 2016
ADW-021
158
36.872838
-107.960741
No
8/24/16
10/1/16
No
10/1/16
No
4/19/17
Fall 2016
ADW-010
163
36.838545
-107.992183
Yes
8/24/16
10/1/16
No
8/2015
3/2016
10/1/16
No
8/2015
3/2016
4/19/17
Fall 2016
FW-012
177
36.783635
-108.102111
No
8/27/16
10/2/16
No
10/2/16
No
4/20/17
Fall 2016
FW-040
192
36.707467
-108.150813
Yes
8/27/16
10/2/16
No
10/2/16
No
4/20/17
Fall 2016
Upper San Juan River
SJAR*
190
36.719664
-108.207125
Yes
8/29/16
9/27/16
No
8/2015
3/2016
9/27/16
No
8/2015
3/2016
4/18/17
Fall 2016
LVW-020
197
36.730556
-108.251046
No
8/27/16
10/2/16
No
8/2015
3/2016
10/2/16
No
8/2015
3/2016
4/18/17
Fall 2016
SJLP
197
36.73588701
-108.2539868
No
8/29/16
9/27/16
No
9/27/16
No
11/15/16
Fall 2016
SJFP
214
36.74815602
-108.4120157
Yes
8/30/16
9/28/16
No
8/2015
3/2016
9/28/16
No
8/2015
3/2016
11/14/16
NS
SJSR
246
36.78162422
-108.6927838
No
8/30/16
9/28/16
No
9/28/16
No
11/6/16
Fall 2016
Lower San Juan
SJ4C
296
36.99621613
-109.0046838
No
10/26/15
8/31/16
9/29/16
No
9/29/16
No
11/8/16
Fall 2016
SJMC
346
37.25822644
-109.3106036
Yes
10/26/15
8/31/16
9/29/16
No
9/29/16
No
11/10/16
Fall 2016
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EPA Gold King Mine Biological Response Report
Location
Distance
from GKM
Latitude
Longitude
Benthic
Macroinvertebrate
Assemblage
Benthic
Macroinvertebrate
Tissue
Fish
Tissue
Physical
Habitat
(KM)
Pre
Pre
Pre
SJBB
378
37.25737015
-109.6185856
Yes
10/26/15
9/1/16
9/30/16
No
9/30/16
Yes
11/13/16
Fall 2016
SJMH
421
37.146948
-109.853672
No
10/26/15
9/1/16
9/30/16
No
9/30/16
No
11/13/16
Fall 2016
SJCH
511
37.293336
-110.399293
No
10/26/15
8/25/16
10/1/16
No
10/1/16
No
NS
Fall 2016
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EPA Gold King Mine Biological Response Report
3.3 Historic biological data
EPA worked with federal, state, tribal and local partners to compile the historic biological data for the
Animas and San Juan rivers.3 Most of the historic data were obtained from online sources, however some
were provided through data requests (see Appendix B). For the Animas River, the pre-release period of
record was defined as immediately before the GKM release (date varies by sampling location) back to
2005. Data collected prior to 2005 in the upper Animas River were avoided because of changes in the
watershed that affected water quality and the aquatic community.4 In the mid and lower Animas River and
San Juan River, the pre-release period of record included data collected back to 2000. The period of record
was greater for the San Juan because metal concentrations generally decline with distance from the mining
district and any changes in the upper Animas activities in the early 2000 's are less likely to be observed in
the San Juan River (Chapter 2). Data collected prior to 2000 were avoided since there is a greater likelihood
that the study objectives and sampling methods have been modified over the years, reducing the
comparability of the datasets.
Additionally, biological communities, particularly benthic macroinvertebrates, display seasonal variability
making comparisons difficult when samples were not collected during the same general time of year.
Therefore, the pre-release dataset was limited to samples that were collected in late summer and fall to
facilitate the comparison with EPA's response data that were mostly collected in the months of August-
October. Due to the effect of seasonal variability, we are not presenting historic spring sampling data in this
report.
Pre-GKM release benthic macroinvertebrate and fish data were available for a number of the Animas River
sampling locations in Colorado and Southern Ute Indian Reservation due to past and continued interest in
the effects of proximate mining run-off The historic benthic macroinvertebrate data for the upper Animas
has been funded and collected by several entities and most recent efforts were conducted by EPA
Superfund activities with the support of Mountain Studies Institute (MSI 2016). Pre-release and historic
macroinvertebrate data were less abundant further downstream on the Animas and San Juan River in New
Mexico, Ute Mountain Ute Reservation, the Navajo Nation, and Utah.
Fish population surveys, on the other hand, have been conducted on a regular basis for the last several
decades in the Animas River near Durango, CO by Colorado Parks and Wildlife and in the San Juan River,
by U.S. Fish and Wildlife Services to support the recovery of listed fish species.
3 In this report, we use historic, pre-release and background condition to describe when data were collected with
respect to the GKM release. Historic data include all data and studies that predate the GKM release. Pre-release data
include a subset of the historic data defined by the location specific period of record. Background condition is used to
describe the biological condition or concentrations that do not include GKM effects. Background condition can
include historic data and data collected after the plume and deposits were removed through the system.
4 http://animasriverstakeholdersgroup.org/blog/index.php/2015/10/23/gold-king-timeline/
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EPA Gold King Mine Biological Response Report
3.4 Sampling methods and laboratory analyses
Existing Colorado Department of Public Health and Environment (CDPHE), Mountain Studies Institute
(MSI) and EPA National Rivers and Streams Assessment (NRSA) methods were used to collect the benthic
macroinvertebrate and tissue samples in the response and follow-up monitoring. Below is the full list of
biological and physical habitat sampling and assessment methods that were used by EPA and other federal,
state and tribal partners that provided pre- and post-GKM release data. The data providers, sampling
methods and analytical approach for the water and sediment data presented in this report are found in the
EPA ORD report (EPA 2016c).
• Macroinvertebrate Collection and Identification
o Colorado Department of Public Health and Environment Policy Statement 10-1 (CDPHE
2010/2017)
o Southern Ute Indian Tribe macroinvertebrate sampling protocol (SUIT 2015)
o New Mexico Environment Department (NMED 2013)
o EPA Remedial Program method historically used on Animas River described in MSI (2016)
and Anderson (2007); identified as the Animas River method in this report
o EPA National Rivers and Streams Assessment method (EPA 2013a, 2013b)
• Fish Collection and Identification
o Colorado Parks and Wildlife (CPW 2010, 2015)
o U.S. Fish and Wildlife Service (USFWS 2012)
• Macroinvertebrate Tissue
o EPA Remedial Program method historically used on Animas River (MSI 2016)
• Fish Tissue
o EPA National Rivers and Streams Assessment method (EPA 2013a, 2013b)
• Physical Habitat
o EPA National Rivers and Streams Assessment method (EPA 2013a, 2013b)
When pre-release data and historic methods were not available for a given location, the EPA defaulted to
the NRSA method for follow-up monitoring for that indicator
(https://www.epa.gov/sites/production/files/2016-
04/documents/nrsal314 fom nonwadeable versionl 20130501.pdf). However, many of the sampling
locations have abundant pre-release biological data (e.g., benthic macroinvertebrates data in the Animas
River). In these situations, the EPA used the method that best matched the pre-release data collection
methods to maximize comparability. Below we provide brief descriptions and comparisons of the field and
analytical laboratory methods that were considered when determining the comparability of data collected
by different, federal, state, and tribal partners.
3.4.1 Benthic macroinvertebrate assemblage
In the upper Animas River from the GKM to Durango, benthic macroinvertebrate samples were collected
with a method developed by Chester Anderson and used previously within the Animas River watershed
(Anderson 2007). The upper Animas collection method utilizes modified protocols developed by the EPA
(Barbour et al. 1999) and CDPHE (CDPHE 2010a). In the lower Animas River from Durango to the
confluence with the San Juan River, EPA contractors used both CDPHE and EPA NRSA methods
depending on the availability of pre-release data at these sites. When the habitat primarily consists of
riffle/run, EPA NRSA and CDPHE methods are expected to generate similar results. In the San Juan River,
all benthic macroinvertebrate data were collected using EPA NRSA methods. The differences and
similarities in the field sampling methods are identified in Table 3.2. Overall, the methods used throughout
the basin have a number of common elements thus allowing for comparisons between pre- and post-release
benthic macroinvertebrate assemblages. Except for QA field duplicate samples, each sampling event was
represented by a single sample per location.
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EPA Gold King Mine Biological Response Report
Table 3.2. Comparison of benthic macroinvertebrate sampling methods used by the different data providers. LTU
= lowest taxonomic unit. NR = not reported.
Method
Comparison
Animas River
CDPHE
EPA NRSA
NMED
(EPA EMAP)
SUIT
Method
Wadeable
Wadeable
Wadeable
Non-wadeable
Large rivers
Wadeable
Habitat
Selection
riffle
riffle/run
11 multi-habitat
transects
11 multi-
habitat
transects
11 multi-
habitat
transects
riffle
Sampling
Net Type
rectangular dip
net w/ dolphin
bucket
rectangular kick
net w/ dolphin
bucket
D-frame
D-frame
D-frame
D-frame
w/
dolphin
bucket
Sampling
Net Size
46 cm X25 cm
8"xl8"
12"
12"
12"
18"
Sampling
Mesh Size
500 [am
500-600 [am
500 [am
500 [am
500 [am
500 [am
Sampling
Area
Method
0.115m2 hand
scrubbed rocks
1 m2 kick
0.093 m2
1-meter sweep
in primary
habitat
3 1-meter
sweeps (2 in
primary
habitat; 1 in
secondary
habitat)
1 m2 kick
Sample time
90s
60s
30s
NA
not timed
not timed
Reps in
composite
5 (diagonally
across riffle)
1
11
11
11
1
Total area
sampled
0.575 m2
1 m2
1 m2
11m2
33 m2
1 m2
Index Period
not provided
July 1- Oct 1
June 1 - Sept 30
June 1 - Sept 30
NR
NR
Subsampling
and
Enumeration
500 organisms
300 organisms
500 organisms
500 organisms
NR
300
organisms
Taxonomic
Level
LTU
LTU
Genus unless
otherwise
specified
Genus unless
otherwise
specified
NR
LTU
3.4.2 Fish populations
The EPA evaluated fish data that were collected by Colorado Parks and Wildlife (CPW) in the upper
Animas River and the U.S. Fish and Wildlife Service (USFWS) in the lower Animas River and San Juan
River. Both partners collected fish assemblage data with bank and/or raft electrofishing depending on the
sampling depth. Although the field sampling methods are somewhat different, the agencies collected
from unique river ecosystems that did not spatially overlap allowing for separate data analyses (Table
3.3).
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EPA Gold King Mine Biological Response Report
Table 3.3. A comparison of adult fish population sampling methods used by the Colorado Parks and Wildlife and
U.S. Fish and Wildlife Service to sample the Animas River and San Juan River, respectively.
Colorado Parks and Wildlife
US Fish and Wildlife Service
Study area
(GKM site ID)
Animas River
• Upper Animas (A72)
• Lower segments:
Animas River #1 (AR19-3)
Animas River #2 (32nd St Bridge, Rotary Park, GKM05)
San Juan River
Entire river from Navajo Reservoir to
Lake Powell; 2 out of every 3 river miles
(all San Juan GKM sites)
Method
Two-pass mark and recapture
Single pass
Gear
Upper Animas: bank electrofishing
Lower Animas: raft electrofishing
Raft electrofishing
(2 rafts)
Index period
NA
Late September to early October
Population data
Count, length, weight, deformities
Count, length, weight, deformities
Colorado Parks and Wildlife
The Colorado Parks and Wildlife (CPW) manages the segment of Animas River downstream of Durango
(Animas River #1) as a category 406 "coldwater regulation stocked stream" and Animas River through
Durango (Animas River #2) as a category 405 "regularly stocked with fry/fingerling/sub-catchable
salmonids" (CPW 2010, 2015). These management practices have led to regular monitoring of the Animas
River fishery for the last several decades, including adult (large) fish surveys typically conduced in the
spring and fall and fry (small) fish surveys in the summer.
For adult surveys, CPW implements a two-pass mark and recapture method. All fish are marked by
punching a small hole in the caudal fin, released back to the river, and resampled two days later. This
sampling method generates estimates of species-specific density, biomass and populations demographics.
The Animas River surveys target both the introduced trout and native species. Targeted small fish sampling
consists of multi-pass depletion surveys along 100m sections of shoreline in shallow water where trout fry
and other small fish (e.g., sculpin) would normally be found. Additional details on the CPW fish survey
methods are available at http://cpw.state.co.us/thingstodo/Pages/FishervManagementSurvevs.aspx.
U.S. Fish and Wildlife Service
Long-term fish community surveys, including targeted larval and adult surveys, have been conducted in the
San Juan River from Navajo Reservoir to Lake Powell by the U.S. FWS with state and tribal partners to
support the San Juan River Recovery and Implementation Program (SJRIP). SJRIP was established to
support the recovery of the endangered Colorado pikeminnow and razorback sucker, in conjunction with
water development projects in the basin. The raft electrofishing collection methods used in sub-adult and
adult fish monitoring programs are designed to "quantitatively document trends in fish community
population parameters (including relative and absolute population size and size structure) occurring over
time among populations of both native and nonnative large-bodied fishes in the San Juan River" (USFWS
2012). The USFWS performs these surveys in September and October each year so between-year
comparisons are not seasonally confounded. Typical sampling duration was 20-30 minutes. The data are
used to inform management actions that are being implemented by the SJRIP such as mimicry of the
natural flow regime, mechanical removal of non-native fishes, removal on in-stream dispersal impediments,
or augmentation of endangered fish populations. Additional details on the SJRIP and fish population data
are available at https://www.fws. gov/southwest/sirip/index.cfm.
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EPA Gold King Mine Biological Response Report
3.4.3 EPA tissue collection methods
EPA Benthic Macroinvertebrate
A composite, whole body benthic macroinvertebrate (BMI) sample was collected from each site for tissue
metal analyses. The samples were collected in a similar manner as the benthic community method used at
that site. The near-term response samples were collected by MSI in 2015 and the follow-up sampling was
conducted by an EPA START contractor in 2016. Using forceps and a fine mesh net, each specimen was
rinsed with deionized water in the field before combining all specimens into a community composite
sample for each site. The treatment of the caddisfly casings differed between 2015 and 2016 samples. In
2015, caddisfly larvae were removed from their cases prior to compositing and processing, which was
consistent with how the samples were collected in 2014. In 2016, the samples were composited and
processed with the caddisfly cases.
To meet laboratory and method analysis requirements, EPA contractors aimed to collect at least 2 grams of
wet weight BMI tissue for each site. Analytical methods were modified (i.e., analyzed "as is" or with micro
digestion techniques; see Section 3.4.6) for samples that fell short of this minimum tissue requirement
because of the limited benthic macroinvertebrate communities at the site. The samples were immediately
frozen (not held for gut content purging) and shipped on ice to the contract laboratory for metal analyses.
EPA Fish Tissue
NRSA fish tissue collection methods were implemented at 25 sampling locations (Table 3.1). The NRSA
method focuses on fish species common to the region of interest, are sufficiently abundant within a
sampling reach, and represent a species and size class that would be consumed by humans. Whole fish
samples were frozen and shipped on ice to Physis Environmental Laboratories for analysis. The filet with
skin was then dissected from the individual fish in the lab and sample replicates were composited prior to
analysis. Tissue samples represent a composite of four to five adult fish of the same species that are similar
in size (the smallest individual in the composite is no less than 75% of the total length of the largest
individual).
3.4.4 Colorado fish tissue collection methods
The CDPHE and CPW collected fish filets from rainbow and brown trout of catchable size from the
Animas River near the Durango area. This stretch of river is designated as gold medal fishery and includes
Rotary Park (94 RKM), GKM05 (96.5 RKM), and AR19-3 (104 RKM) sampling locations. Samples were
collected immediately following the GKM release in August 2015 and again in March 2016. The results of
the metals analyses were used to evaluate potential impacts to human health (CDPHE 2016b).
3.4.5 New Mexico tissue collection methods
The NMDGF collected benthic macroinvertebrate and fish tissue samples immediately following the GKM
release in August 2015 and again in March 2016. Sampling locations included 2 sites on the Animas River,
(ADW-022;148 RKM and ADW-010; 163 RKM) and three sites on the San Juan River, including one site
upstream of the confluence with the Animas River (SJAR; 191 RKM, LV-020; 196 RKM and SJFP; 214
RKM (Figure 3.2)).
NMDGF Benthic Macroinvertebrate Tissue
NMDGF collected benthic macroinvertebrate samples using a 1.0 meter kick-seine. Samples were sorted by
taxonomic group in the field prior to metals analysis. The goal was to collect >3.0 grams of tissue in the
following taxonomic groups: Plecoptera (stoneflies), Ephemeroptera (mayflies), Trichoptera (caddisflies),
and Diptera (true flies). Several orders were either not present or not present in sufficient numbers to
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EPA Gold King Mine Biological Response Report
collect the minimum tissue requirement. The whole-body samples were placed in a whirl-pak bag, labeled,
place in a cold cooler and frozen prior to shipment to the laboratory.
NMDGF Fish Tissue
NMDGF fish tissue samples were collected with a raft electroshocker. Fish samples were dissected prior to
metals analysis and were separated into muscle (filets without skin) and liver tissue samples, for all species
except speckled dace. Field crews aimed to collect a minimum of 5 grams for each tissue type. Multiple
replicates were collected when species were present in sufficient numbers. Each sample represented an
individual fish. Given the small mass of the speckled dace, speckled dace muscle samples represent a
compost of approximately 5 fish with the head and gut content removed.
lW-022
ADW-010
SJFP
LVW-020
SJAR
Legend
^ Collection Su«s
New Mexico Dept Game and Fish
Fish and Macroinvertebrate Collection for Heavy Metal Testing
Figure 3.3. New Mexico Department of Game and Fish sampling locations for benthic macroinvertebrate and fish
tissue.
3.4.6 Navajo Nation fish tissue methods
Navajo Nation Environmental Protection Agency (NNEPA) analyzed catfish filets without skin collected
from the San Juan River at five locations between Farmington, NM and Bluff, UT in June 2017 (NNEPA
2017). Samples consisted of two composites of five fish from each sampling location (50 total fish) and
were analyzed for 25 metals.
3.4.7 Physical habitat methods
Physical habitat refers to the structural attributes that influence the biological condition of an aquatic
resource. EPA measured the physical habitat characteristics in Table 3.4 to quantify the eight general
attributes of physical habitat condition, including: habitat volume/stream size; habitat complexity and cover
for aquatic biota; streambed particle size; bed stability and hydraulic conditions; channel-riparian and
floodplain interaction; hydrologic regime; riparian vegetation cover and structure; and riparian disturbance.
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EPA Gold King Mine Biological Response Report
At each location, physical habitat data were collected from longitudinal profiles and at 11 cross-sectional
transects. Streamside riparian plots were evenly spaced along a defined reach at the sampling sites in fall
2016. The length of each sampling reach was determined by the wetted channel width. Main channel and
mid-channel substrate were determined by probing the bottom and 11 littoral/riparian plots were spaced
systematically, alternating sides along the river sample reach.
Table 3.4 Summary of the components used to characterize physical habitat at wadeable sampling locations.
Similar components were measured at non-wadable sites with methods that are modified to allow for sampling
from a boat.
Component
Description
Thalweg Profile
Measure maximum depth, classify habitat and check presence of backwaters,
side channels and loose, soft deposits of sediment particles at 10 equally
spaced intervals between each of 11 transects (100 individual
measurements along entire reach) The number of thalweg measurements is
specified by the stream's mean wetted width.
Wetted Width /
Bar Width
Measure wetted width and bar width (if present) and evaluate substrate
particle size classes at 11 cross-section transects and midway between them
(21 width measurements and substrate notations along entire reach)
Woody Debris
Tally
Between each of the channel cross-sections, tally large woody debris numbers
within and above the bankfull channel according to specified length and
diameter classes (10 separate tallies).
Channel and
Riparian
Characterization
At 11 transects placed at equal intervals along reach:
• Measure channel cross-section dimensions, bank height, bank undercut distance,
bank angle, slope and compass bearing (backsight), and riparian canopy density
(with densiometer).
• Visually estimate: substrate size class, embeddedness and water depth at five
equidistant points on cross-section; areal cover class and type (e.g., woody trees) of
riparian vegetation in canopy, understory, and ground cover; areal cover class of
fish concealment features, aquatic macrophytes and filamentous algae.
• Observe and record: presence and proximity of human disturbances.
At 10 cross-sections that are midway between the 11 transects above:
• Visually estimate substrate size class at 5 equidistant points on each cross-section
Assessment of
Channel
Constraint, Debris
Torrents, and
Major Floods
After completing thalweg and transect measurements and observations,
identify features causing channel constraint, estimate the percentage of the
channel margin that is constrained for the whole reach, and estimate the
bankfull and valley widths. Check for evidence of recent major floods and
debris torrent scour or deposition.
Discharge
Measure water depth and velocity at 15 to 20 equally spaced intervals across
one carefully chosen channel cross-section.
21 In very small streams, measure discharge by timing the passage of a neutrally
buoyant object through a segment whose cross-sectional area has been
estimated or by timing the filling of a bucket.
3.4.8 Laboratory analytes and methods
EPA follow-up monitoring fish and benthic macroinvertebrate tissue samples were analyzed for the 16
metals and metalloids on the priority Metal/Cyanide Target Analyte List (TAL) that are most likely to
accumulate in biological tissues (see Table 3.5). All tissue samples were processed using inductively
coupled plasma (ICP) technologies that use mass spectrometry (MS) instrumentation. Mercury was
analyzed using cold vapor atomic fluorescence spectrometry (CVAFS). EPA 2016 tissue samples were
analyzed by Physis Environmental Laboratories, Inc., Anaheim, CA. EPA's 2015 benthic
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EPA Gold King Mine Biological Response Report
macroinvertebrate tissue samples and pre-release samples (2012 and 2014) were analyzed by the
Environmental Services Assistance Team (ESAT) contractor in R8 EPA Laboratory, Golden, CO.
Additional data analyzed in this report include samples collected by Colorado Department of Public Health
and Environment (CDPHE), Southern Ute Indian Tribe (SUIT), and New Mexico Department of Game and
Fish (NMDGF) and Navaho Nation EPA (NNEPA). The CDPHE, NMDGF, NNEPA results were reported
as wet weight concentrations, whereas SUIT results were reported as dry weight concentrations. Weights
are converted to a common standard when datasets are combined in analyses. Table 3.5 provides a general
guide to the laboratory methods used by all data providers.
Table 3.5. Analytical methods, parameters and technology used for the biological tissue samples collected by EPA,
CDPHE, SUIT, and NMDGF. BMI = benthic macroinvertebrate; a = dry weight results; b= wet weight result; c = as
received result; indicates a post-GKM release sample.
Data
Source
Matrix
Lab
Date (result
type)
Methodology
Parameter
Technology
EPA:
pre-
release
&
response
BMI
ESAT
(R8 Lab)
Golden, CO
Oct 2012 (a);
Sept-Oct 2014
(c);
Sept-Oct 2015
(c)*
EPA Method 200.7
Al, Be, Ca, Fe, Mg, Mn, K,
Na, Sr, Zn
ICP/AES
EPA Method 200.8
Sb, As, Ba, Cd, Cr, Co, Cu,
Pb, Mo, Ni, Se, Ag,TI, V, Zn,
ICP/MS
EPA Method 245.1
Hg
CVAA
EPA Method 7473
Hg
TDAAAS
EPA Method 200.2
Solids, dried at 602C
-
EPA:
follow-
up
BMI &
Fish (filet
composite
w/ skin)
Physis
Environmental
Lab
Anaheim, CA
Sept 2016(a)*;
April 2017(a)*
EPA Method 6020
Al, Sb, As, Cd, Cr, Cu, Fe, Pb,
Mn, Ni, Se, Ag, Sn, V, Zn,
ICP/MS
EPA Method 245.7
Hg
CVAFS
SM 2540B
Solids, dried at 103-1052C
Gravimetric
CDPHE
Fish
(filet)
Laboratory
Services
Division of
CDPHE
Aug 2015(b)*
Mar 2016(b)*
EPA Method
200.7/200.8
Be, As, Se, Cd, Pb, U, Al, Co,
Cu, Mn, Ni, Zn
--
EPA Method 7473
Hg
TDAAAS
SUIT
Fish
(muscle
Plug)
July 2015 (a)
—
As, Be, Se, Cd, Pb, U, Al, Co,
Cu, Mn, Ni, Zn, Hg
ICP/MS
-
Solids
-
NMDGF
BMI &
Fish
(filet w/o
skin; liver)
ALS
Environmental
Aug 2016(b)*
Mar 2016(b)*
EPA Method 6020
Al, As, Cd, Cu, Pb, Mn, Se,
Zn
ICP/MS
NNEPA
Fish (filet
w/o skin)
TestAmerica
April 2017(b)*
EPA Method 6020
Al, Sb, As, Ba, Be, Ca, Cd, Cr,
Co, Cu, Fe, Pb, Mg, Mn,
Mo,Ni, K, Se, Ag, Na, Sr, Ti,
Sn, V, Zn,
ICP/MS
Method 7471B
Hg
CV
Metal concentrations in tissue were converted from wet weight to dry weight and dry weight to wet weight
as needed to generate a common unit of concentration using the following equation, which is regularly used
to support tissue data analyses (Lusk et al. 2005, EPA 2016d):
[metal] ppm ww = [metal] ppm dw x (percent solid/100)
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EPA Gold King Mine Biological Response Report
3.5 Data QAQC
Biological data collection, processing, and quality review efforts followed quality assurance procedures
described in the Quality Assurance Project Plan (QAPP) titled "Sampling and analysis plan/quality
assurance plan for Gold King Mine long term monitoring - 2015-2016 sampling events. Version 3"
(Appendix in the EPA Gold King Mine Field Activities report; to be posted at
https://www.epa.gov/goldkingmine). A comprehensive list of data sources is provided in Appendix B. All
data acquired may not have been used in final data products presented in this report but have been archived
with project materials. EPA does not make any claims as to the quality or accuracy of the data gathered
from state, tribal, and federal partners. The project team applied quality assurance and quality control
measures to acquired data to ensure that the analyses performed were properly conducted and that the data
used in this report represented the original data obtained from all sources. Acquired data were reviewed and
normalized as needed to be able to do a watershed-scale analysis. Inspections occasionally identified errors
in the original flies, primarily related to sampling dates. The team corrected the errors in the master file
following consultation with source data owners. Edited data were notated in supporting documentation with
justification for doing so. Differences in field and analytical methods used by the various data providers
were identified, assessed for comparability and considered when developing our approach to the data
analysis. Datasets were analyzed collectively when methods were similar, and we present analyses
consistent with the state/tribal analysis tools when such tools were available.
3.6 Assessment approach
The report utilized available data to assess the impact of metals released from the Gold King Mine on
aquatic communities and their body burden of metals. These characteristics were assessed spatially along
the Animas and San Juan rivers that were affected by the release to various levels and temporal duration
during and in the 18-months following the event (EPA 2016c). Physical habitat, metal concentrations (pre-
release, during the plume and post-release), and the biological community were evaluated with the river
distance (km) downstream from the Gold King Mine to determine watershed-wide longitudinal trends. Pre-
and post-event data samples were compared where data availability allowed using statistical tests
appropriate to available data. Table 3.6 provides a summary of all sources of data that were acquired for
this report. Sources that are identified as primary data included multiple sampling locations, dates and
sample replicates. The additional data sources represent studies with limited sampling locations and/or
sampling dates. Chapters include additional description of data and analytical techniques, statistical tests,
and results.
The results of data analysis are organized in 5 chapters:
• Physical habitat in the Animas and San Juan rivers (Chapter 4)
• Benthic macroinvertebrate assemblage (Chapter 5)
• Fish populations (Chapter 6)
• Bioaccumulation of metals in benthic macroinvertebrates (Chapter 7)
• Bioaccumulation of metals in fish (Chapter 8)
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EPA Gold King Mine Biological Response Report
Table 3.6. Summary of pre- and post-GKM release biological and physical habitat data collected from the Animas
and San Juan rivers presented in this report. Sampling locations are distributed throughout the river unless
otherwise noted.
Data Source
Benthic
Macroinvertebrate
Assemblage
Benthic
Macroinvertebrate
Tissue
Fish
Population
Fish
Tissue
Physical
Habitat
EPA follow-up: START
Contractors
Post
(2016)
Animas
& San Juan
Animas
& San Juan
Animas
& San Juan
Animas
& San
Juan
<0
4-»
to
a
o
EPA response:
Superfund/
Mountain Studies
Institute (MSI)
Pre &
Post
(2015)
Animas
(upper & mid)
Animas
(upper & mid)
a>
u
i_
3
o
CO Parks and Wildlife
(CPW)
Pre&
Post
Animas
(upper &
mid)
to
E
T
a.
US Fish and Wildlife
Service (USFWS)
Pre&
Post
San Juan
NM Department of
Game & Fish
(NMDGF)
Post
Animas
(lower)
San Juan
(upper)
Animas
(lower)
San Juan
(upper)
Southern Ute Indian
Tribe
(SUIT)
Pre&
Post
Animas
(mid)
Animas
(mid)
CO Department of
Public Health and the
Environment (CDPHE)
Pre&
Post
Animas
Animas
(mid)
vt
ai
u
3
O
l/>
Animas River
Stakeholder Group
(ARSG)
Pre
Animas
(upper)
IS
4-»
IS
Q
Animas Watershed
Partnership (AWP)
Pre
Animas
(upper & mid)
IS
c
o
"D
EPA: National Rivers
and Streams
Assessment (NRSA)
Pre
San Juan
San Juan
<
NM Environment
Department
(NMED)
Pre
Animas (lower)
San Juan
Navajo Nation EPA
(NNEPA)
Post
(2017)
San Juan
Bureau of
Reclamation
Pre
(1996)
San Juan
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EPA Gold King Mine Biological Response Report
CHAPTER 4 PHYSICAL HABITAT
The Animas and San Juan river physical habitat Table 4.1. EPA National Rivers and Streams Assessment
analyses focused on four primary indicators of physical habitat indices used to describe the aquatic
physical habitat conditions in rivers and streams: habitat condition,
relative bed stability and excess fines, in-stream
fish habitat complexity, riparian (streamside)
vegetation, and riparian disturbance (EPA 2016b).
Table 4.1 provides details on each indicator and
accounts for several individual physical habitat
metrics. The primary indicators help document
the impact of our human footprint across the
landscape as well as the progress made through
widespread protection and mitigation efforts.
When pre-release NRSA data were available, the
2016 habitat condition was compared to pre-
release results.
In addition to the four primary habitat indicators,
the longitudinal patterns of percent fine sediment,
channel slope, and elevation throughout the
Animas and San Juan rivers were evaluated to
help interpret the spatial differences in biological
communities. Longitudinal patterns were
measured with the river distance (km)
downstream from the Gold King Mine.
The baseline physical and chemical characteristics
within the study area establishes the foundation
for the aquatic biota that are expected to occur at
the different sampling locations. The physical
habitat characteristics include naturally occurring conditions (e.g., elevation, temperature, substrate) as well
as anthropogenic alterations to these conditions (e.g., riparian disturbance, channelization, watershed
erosion). The habitat within the effected river length ranges from an elevation 8,500 ft in the Animas at the
confluence with Cement Creek to 3,400 ft at the furthest downstream location on the San Juan River. With
the elevation change, the aquatic habitat transitions from a mountain stream that is characterized by narrow
channels, steep gradient, and substrate dominated by cobble/boulder in the upper Animas River to a wide
channel, low gradient, frequently braided channels dominated by sand and finer substrates in the mainstem
of the San Juan River (Figure 4.1 .a). The channel slope in the Animas River is greatest at sampling
locations closest to GKM (A68 = 1.5%, A72 = 0.7%) and in Mineral Creek (M34 = 1.6%). The median
slope in the Animas River sampling locations is 0.4 %. The slope of the San Juan River, on the other hand,
is similar from the confluence with the Animas to the most downstream locations, with values ranges from
0.07-0.16%.
Habitat Index
Description
Relative bed
stability and
excess fines
(LRBS)
streambed stability defined by relative
substrate and particle size
Inst ream
habitat
complexity
(XFC_NAT)
areal cover of woody debris, brush,
undercut banks, overhanging
vegetation, boulders, and rock ledges
Riparian
vegetation
(XCMGW)
areal cover and type of streamside
vegetation found in the ground layer
(<0.5m), mid-vertical layer (0.5-5.0 m)
and upper vertical layer (>5.0m)
Riparian
human
disturbance
(W1_HALL)
relative measure of 11 human activities:
walls, dikes, revetment or dams,
buildings, pavement or cleared lots,
roads or railroads, influent or effluent
pipes, landfills or trash, parks or lawns,
row crop agriculture, pasture or
rangeland, logging and mining.
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EPA Gold King Mine Biological Response Report
One measure of anthropogenic impacts in the
immediate aquatic habitat is the level of
disturbance in the riparian zone. A wide range
of human disturbance in the riparian area is
observed in the Animas River watershed with
all sampling locations exhibiting metrics with
medium to high levels of disturbance.
Riparian disturbance generally decreases
downstream in the San Juan River, with the
most disturbed sites near the confluence with
the Animas (Figure 4.1.b).
Three sampling locations in the San Juan
River have pre-release habitat data that were
collected as part of the National Rivers and
Stream Assessment. Two sites, SJMC and
SJBB are located on the San Juan River below
the confluence with the Animas River. The
third site, SJAR is located on the San Juan
River above the confluence with the Animas
River. The condition of riparian vegetation
and habitat complexity has scored consistently
good over the years at all three locations
(Table 4.2). The relative bed stability and
habitat complexity has also remained
consistent at SJMC and SJBB, yet changed to
a more degraded condition at the upstream
location SJAR in 2016. Riparian human
disturbance scored medium and high at both
downstream locations over time, suggesting
that human activities near the mainstem have
been consistently present at these sites.
a)
b)
Streambed Silt and Fine Sediment
100
90
80
70
60
50
40
30
20
10
0
• ~
• •
100 200 300 400 500
Riparian Human Disturbance
• •
t
•
•
•
•
•
•
•
A *
• *
A
~ A
• Animas
A San Juan
~ Mineral
• Animas
a San Juan
~ Mineral
Low (0.33)
high (1.5)
100 200 300 400 500
Distance from GKM (km)
Figure 4.1. Longitudinal change in a) streambed silt and fine
sediment and b) riparian human disturbance physical habitat
characteristics for the Animas River, San Juan River, and
Mineral Creek.
Table 4.2. Physical
habitat condition for
sampling locations on
the San Juan River with
pre-release NRSA
physical habitat data
including 1 site on the
San Juan River located
upstream of the
confluence with the
Animas (SJAR), and two
downstream locations
SJMC and SJBB.
SITE
Year
Relative Bed
Stability
Riparian
Vegetation
Habitat
Complexity
Human Riparian
Disturbance
SJAR
(upstream)
2016
Poor
Good
Fair
High
2013
Fair
Good
Good
Medium
2009 (May)
Poor
Good
Good
Medium
2009 (June)
Fair
Good
Good
Low
SJMC
2016
Fair
Good
Good
Medium
2013
Fair
Good
Good
High
2009
Fair
Good
Good
Medium
SJBB
2016
Fair
Good
Good
Medium
2013
Fair
Good
Good
High
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EPA Gold King Mine Biological Response Report
CHAPTER 5 BENTHIC MACRO INVERTEBRATE ASSEMBLAGES
As discussed earlier in this report there are two overarching study questions about the potential impacts due
to the GKM release to biology in the Animas and San Juan rivers. First, did the GKM event add to
biological degradation in the already contaminated upper Animas river; and second did the GKM event
degrade biological communities in other downstream segments of the Animas and San Juan rivers that had
no previously known metal contamination? Chapter 5 reports on the results from the benthic
macroinvertebrate assemblage analysis, with an assessment of both pre- and post-release condition, and
longitudinal condition moving downstream from the confluence of Cement creek. This analysis found no
conclusive evidence of changes in the already degrade upper Animas river when comparing GKM pre- and
post-release benthic macroinvertebrate assemblage data, using both a multi-metric index or individual
assemblage metrics. When comparing samples throughout the Animas and San Juan Rivers, there was no
significant difference between per- and post-release samples and that benthic macroinvertebrate assessable
condition generally improved moving downstream.
5.1 Benthic macroinvertebrate data
Benthic macroinvertebrate assemblage data collected in the Animas and San Juan rivers between June 2008
to October 2016 were obtained from state, tribal and federal agencies as described in Chapter 3 and listed in
Table 3.5. Characteristics of the macroinvertebrate community composition were used to assess the health
of aquatic benthos in relation to time and location within the Animas and San Juan rivers. Time was
expressed in periods relative to the GKM release including pre-event, the event period defined as August 5
to August 13, 2015 when water quality effects were greatest, and post-event, from August 14, 2015 to April
2017 when the last samples were collected. Location was expressed as distance measured along the river
centerline length starting at the Gold King Mine in the headwaters of the Animas River in Cement Creek.
Samples of 300 to 500 organisms were collected from multiple habitats or targeted riffle/run locations
using kick-nets of varying size. Since most samples were processed using a fixed subsample approach, only
relative abundance of organisms and not density could be used during analysis. Most taxa were identified to
genus or species. Assessment of seasonal differences of the benthic macroinvertebrates assemblages
between pre- and post-GKM release was limited due to inadequate sampling in seasons other than summer.
Spring sampling with pre- and post-GKM release results were limited to only two sites (AR16-0 and AR2-
7), thus only samples collected during an index period of June through October were used in order to limit
the confounding effects of seasonal variation.
There are various metrics that assess the health of aquatic communities using population sampling to
characterize presence and relative abundance of macroinvertebrates and/or fish species. Some metrics
target specific members of the macroinvertebrate community (e.g. taxonomic or functional feeding group),
while others combine multiple assemblage metrics into multi-metric indices (MMI) that provide a more
holistic assessment of condition of the entire community. This assessment applied both individual
assemblage and multi-metric indices to assess the general health of macroinvertebrate communities in the
Animas and San Juan rivers before and following the GKM release. Additional analyses of pre- and post-
GKM release benthic macroinvertebrate data collected from the upper and middle Animas River were
presented in MSI (2016, 2017).
5.2 Benthic macroinvertebrate assemblage assessment tools
Two individual benthic macroinvertebrate metrics known to be responsive to elevated metal concentrations
were included in analysis of benthic macroinvertebrate species. Taxa richness is the total number of
distinct taxa units (TotalTaxa). Percent EPT (%EPT) is the percent of the total number of individuals that
represent Ephemeroptera, Plecoptera and Trichoptera taxa. These taxa favor habitats in cool, clear water
and rocky substrate that are most characteristic of the Animas River. Within the EPT taxa, four additional
taxonomic groups that have been identified as sensitive to metals pollution were also assessed. These
51
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EPA Gold King Mine Biological Response Report
included three Ephemeroptera taxa (Percent Ephemerellidae, Percent Heptageniidae, Percent Baetis), and
one Plecoptera taxa (Percent Taeniopterygidae).
MMIs have also been used throughout the United States to assess aquatic condition based on fish and
macroinvertebrate assemblage data (e.g., Karr and Chu 2000; Barbour el al. 1999; Barbour el al. 1996).
The multi-metric approach is an analytical process that combines metrics to define a locally or regionally
relevant index. The process involves summarizing various assemblage attributes (e.g., composition,
tolerance to disturbance, trophic and habitat preferences) as individual "metrics" or measures of the
biological community. Candidate metrics are evaluated for aspects of performance for each waterbody and
a subset of the best performing metrics are then combined into a locally-defined MMI. EPA and Colorado
CDPHE have each developed MMI methods; both were applied to the benthic macroinvertebrate data in an
attempt to gain better resolution and to be representative of the Animas River and San Juan River habitats.
EPA's MMI methodology was first developed in the Wadeable Stream Assessment (WSA) of 2004 and
later refined and used in the National Rivers and Streams Assessment (NRSA) of 2008/09 (EPA/841/R-
16/008). Additional details on the development of EPA's MMI is found in Stoddard et al. (2008) and
Herlihy et al. (2008). EPA's NRSA MMI is composed of 6 benthic macroinvertebrate metrics that are
specific to aggregated Level III ecoregions. Ecoregions are areas where ecosystems, and the type, quality,
and quantity of environmental resources are generally similar. The ecoregions relevant to the EPA MMI
assessment included the Western Mountain (WMT) and Xeric (XER) ecoregions.
EPA's ecoregion MMIs were developed for each ecoregion in the study area by summing the six metrics
that performed best in each (Table 5.1). Note that the 6 best-performing metrics varied somewhat between
the two ecoregions. The calculated MMI at a site is compared to two condition thresholds that generally
represent the 25 th and 5 th percentile of reference sites in the ecoregion. If the MMI is: greater than or equal
to the upper threshold, the condition of the community is considered good; between the upper and lower
threshold, conditions are fair; or less than the lower threshold, conditions are poor.
Table 5.1. EPA's NRSA benthic macroinvertebrate multi-metric index (MMI) characteristics
for ecoregions applicable to the Animas and San Juan rivers.
Ecoregion
Western Mountain
(WMT)
Xeric
(XER)
Metrics
• EPT % taxa richness
• % individuals in top 5 taxa
• Scraper taxa richness
• Clinger % taxa richness
• EPT taxa richness
• Tolerant % taxa richness
• Non-insect % individuals
• % individuals in top 5 taxa
• Scraper taxa richness
• Clinger % taxa richness
• EPT taxa richness
• Tolerant % taxa richness
Good
threshold
>54
>53
Poor threshold
<40
<40
Colorado's MMI assigned 3 biotypes to the Animas and San Juan rivers. Colorado's approach defines a
biotype as an aggregation of benthic macroinvertebrate sites that have similar community composition. The
biotype of a sampling location is defined by the ecoregion, elevation, and stream slope. The Mountain and
Transition biotypes were applied to the upper and middle Animas River. All of the Mountain and a portion
of the Transition biotypes coincided with EPA's WMT ecoregion. The lower Animas and San Juan River
sites are located within the Plains and Xeric biotypes.
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EPA Gold King Mine Biological Response Report
The CDPHE MMI also uses the 5-6 best-performing benthic macroinvertebrate metrics (CDPHE 2017).
Metrics selected for the 3 biotypes assigned to the Animas and San Juan are listed in Table 5.2. Using
Colorado's approach, the biological condition of a waterbody is determined by comparing the calculated
MMI to an upper and lower threshold that indicates attainment or impairment of ecological function,
respectively. When the MMI score falls between the attainment and impairment thresholds, additional
metrics are applied to determine if a waterbody supports the biological use.
A value for the NRSA and the Colorado MMIs was calculated for each sample dependent on the
ecoregion/biotype of the site. EPA and Colorado MMI's developed for the Animas and San Juan rivers
differ somewhat in ecoregion delineation, selected community metrics, and the attainment and impairment
thresholds (Tables 5.1 and 5.2). Both MMI scores range from 0 to 100, with higher scores indicating
healthier benthic macroinvertebrate assemblages.
Table 5.2. Colorado benthic macroinvertebrate MMI characteristics for Animas River biotypes. A
full description of the multimeric development can be found in CO DPHE 2017. Description of each
metric is located in Appendix C.
Biotypes
Mountain
Transition
Plains and Xeric
• TotalTax
• EPTTax*
• TotalTax
• EPTTaxA
• NonlnPct
• pt noninsect
Metrics
• pEPTnoB
• pEPTnoB
• pEPTnoB
• ClngrTax
• ColeoPct
• SprwlTaxA
• IntolTax
• pt Intol*
• IntolTax
• pi DecrMtnTrn
• pi IncrMidElev
• pi IncrPlains
• PredTaxFAC
• ClingrTax*
• PredTaxFAC
• ScrapPctFAC
• PredShrTaxFAC
• ScrapPctFAC
Attainment
threshold
Impairment
40
34
29
threshold
A Metric has been adjusted based on Julian Day of sample collection.
* Metric has been adjusted based on average summer temperature
5.3 Trends in macroinvertebrate communities
5.3.1 Longitudinal trends within the river system
Individual biological community metrics including the percentage of Ephemeroptera, Plecoptera, and
Trichoptera individuals relative to the entire sample assemblage (%EPT) and the total number of taxa are
shown in Figures 5.1 and 5.2, respectively. Site values were plotted longitudinally within the Animas and
San Juan rivers as a function of river distance. Data were identified by collection period relative to the
GKM release. A few samples were collected during the GKM event at selected locations within the upper
Animas River, although the Animas and San Juan rivers were broadly sampled a number of times in the
following 2-year post-GKM release period. A narrower set of sites also had pre-event data.
Individual community metrics can be influenced by differences in water quality stressors as well as
availability of suitable habitat for a species within a river system of this length. Lower %EPT or number of
taxa can indicate more highly polluted or degraded water, or it may simply indicate less available suitable
habitat for particular species. The species within the EPT taxa tend to prefer higher gradient, coarse
substrate habitats and would be expected to be observed in high abundance in the mountainous headwaters
53
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EPA Gold King Mine Biological Response Report
of the Animas. There is a strong longitudinal habitat gradient within the Animas River as the river descends
from the steep mountainous headwaters into the relatively low gradient valley in Hermosa Springs/Durango
area at river distance 65 km (Figure 4.1). Habitat conditions continue to transition to low gradient, fine
substrate channels in the lower Animas through the length of the San Juan River (Chapter 4).
A longitudinal trend in macroinvertebrate communities was evident to some extent in the study area. The
%EPT was generally highest in the upper Animas and similar in all sampling periods (Figure 5.1).
However, variability was as pronounced at similar distances as it was along the length of both rivers. The
main exception to this pattern is low %EPT observed in Cement Creek at river distance 14 km. Cement
Creek is one of three major tributaries in the Animas River headwaters that directly receives large amounts
of natural and mining-caused AMD producing water with low pH and high metal concentrations.
The total number of taxa is also a commonly used aquatic community metric, where fewer taxa than
expected for a given habitat within an ecoregion can indicate degraded water quality or poorer habitat. The
number of taxa observed was lowest in headwaters streams within the mining district and was similar in all
sampling periods (Figure 5.2). While the %EPT declined with distance in the Animas River, total taxa
increased along the length of the Animas River. Total taxa peaked in the lower Animas near where it joins
the San Juan River at river distance 193 km. Higher numbers of taxa persist for a few kilometers in the San
Juan River and then decline through the remaining length of the San Juan River, probably reflecting the
homogenous fine-grained river bed that characterizes much of its length. There was almost the same
variability in total taxa observed among sites at similar distances as there was observed along the length of
the affected rivers.
EPA NRSA and Colorado MMI scores are shown below in Figures 5.3 and 5.4, respectively. The lowest
MMI scores were observed in segments persistently impacted by acid mine drainage within Cement Creek
and immediately downstream of its confluence with the Animas River at Silverton, CO, presumably
reflecting the poor water quality that is routinely documented in this area. MMI scores remained generally
low and below attainment levels in the Animas River for some distance downstream of the mining district.
NRSA and Colorado MMI scores improved and achieved attainment at river distances of -80 and 50 km,
respectively near Durango, CO. The Colorado MMI tended to cluster at lower MMI values within the 80-
100 km distance during the 5-day GKM event period, but were within the pre-release range of variability
(Figure 5.4). The zone of impact of acid mine drainage in the upper Animas River is consistent with EPA
ecological risk assessments conducted in support of mine remediation efforts (EPA 2015).
54
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EPA Gold King Mine Biological Response Report
100
9
V
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V Fast-relsase
8
Animas River
8 8
San Juan Riwr
8
8
If
Distance from GKM (Km)
~T
8 8
¦T l£5
San Juan River
8
in
Figure 5.1. Percent of benthic macroinvertebrate assemblage composed of Ephemeroptera, Plecoptera, and
Trichoptera (%EPT).
CD
O
77 P ^
TuD O
Animas River
Q Pre-releas e
A Aug. 5-13, 2D15 F1i,me
V P2St-re)E35E
San Juan River
Distance from GKM (Km)
Figure 5.2. Total number of taxa collected during each sampling event.
55
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EPA Gold King Mine Biological Response Report
100
so -
tf)
£
8 60
w
<
£
+3 -
20 -
Western
Mourtsirs
V ° u
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teris
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San Juan River
i
.Animas River
O Pre-release
& Aug. 5-13, 2015 P lime
V Po=t-Elea=e
II
C istance from GKM (Km)
San Juan River
Figure 5.3. EPA's NRSA MMI scores for samples collected through the Animas and San Juan rivers. Solid blue
line = threshold between good and fair condition for each of the two ecoregions; Dashed blue line = threshold
between fair and poor condition for each of the two ecoregions.
1-»
E
8
yj 60
o
T=l
E
o
o
O
+3 - -a
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Bio type
T
O
¦ *?'
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5
77 7 ~ V
* V %
^ <7 <7 0
*¥**
Plains 6. )feric
Biotype
0
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EPA Gold King Mine Biological Response Report
5.3.2 Pre- and post-GKM release comparisons of benthic macroinvertebrate data
In addition to understanding the general condition of the benthic macroinvertebrate assemblage throughout
the Animas and San Juan rivers, it is also important to understand if the assemblage observed prior to the
GKM release changed after the event. Table 5.3 shows the pre- and post- event median MMI and metric
values from a subset of sites that were sampled for benthic macroinvertebrates during pre- and post- event.
These sites were distributed along the length of the Animas and San Juan rivers, as shown in Figures 5.1
through 5.4.
Due to the limited number of sites with pre- and post-event data, a non-parametric Wilcoxon Signed Rank
test was used to determine whether the median values of the post-event samples of each of the assemblage
metrics were statistically different than the median values of the pre-event samples (Table 5.3). The
Wilcoxon test found no significant difference between the pre- and post-GKM NRSA MMI or the Colorado
MMI. The individual metrics, %EPT and total taxa were statistically compared in the same way. There was
no significant difference in %EPT between the pre- and post-GKM release time periods. Total taxa were
significantly greater in the post-GKM release samples than those collected prior to the release. Appendix C
shows the site specific median values for the pre- and post- event periods. While the Wilcox Signed Rank
test showed no significant differences between the pre- and post-GKM release time periods, the number of
signed-rank scores greater than 10 was substantially higher than the sign-rank scores less than -10 within
the middle Animas (Figure 5.5), suggesting that benthic macroinvertebrates communities showed little
impact from the GKM release.
[Km 64-141]
~ NRSA MMI
o CO MMI
V % EF'T
a. Total Taxa
Km Below GKM
Figure 5.5. Changes in macroinvertebrate community metrics for sites with both pre- and post-release data
following the GKM release in August 2015. Changes in each metric are expressed as summed ranks from
Appendices C.2 through C.5, screened to show only positive or negative changes greater than 10.
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EPA Gold King Mine Biological Response Report
Table 5.3. Comparison benthic macroinvertebrate assemblage indices and metrics for sites that have pre-
and post-GKM release data. Statistical analysis used for the comparison was a Wilcoxon's signed-ranks test.
* Significant at p < 0.05. [Appendix C shows site specific median values for pre- and post- event periods]
Pre-GKM release Median
(Range of Median Values
Across Sites)
Post-GKM release Median
(Range of Median Values
Across Sites)
z-value
/j-valuc
% EPT
69.1 (30.5 -96.1)
68.0 (36.8-91.3)
-2.5854
0.0821
Total Taxa
15.3 (8-29)
18.0(9-25.4)
-2.3049
0.01779*
NRSA MMI
45.8 (23.2-67.7)
47.3 (32.6-66.1)
-1.0859
0.2979
Colorado MMI
47.5 (16.8-85.4)
48.6(17.9-70.8)
-0.7756
0.4637
Previous research within Colorado has identified a number of taxa groups that are sensitive to metal
pollution (Clements 1994, Clements et al. 2000). Due to the relative low number of these sensitive taxa
throughout the watershed, no statistical analysis was conducted to assess changes in relative abundance
between pre- and post-GKM release time periods. Of these sensitive taxa, Baetis spp. showed the greatest
distribution throughout the watershed (Figures 5.6-5.9). Baetis spp. showed similar relative abundance
between the pre- and post-GKM release time periods, with the middle Animas showing the greatest relative
abundances regardless of time periods (Figure 5.7). Clements et al. (2000) did find differences in
sensitivity of specific species of Baetis, and since taxa were not consistently identified to species in the
samples used in this study, those differences may have limited our ability to observe any differences
between the two time periods. Three other metal pollution sensitive taxa groups, Heptageniidae,
Ephemerellidae, and Taeniopterygidae had substantially lower relative abundance throughout the watershed
compared to Baetis spp. regardless of pre- or post-GKM release (Appendix C). In fact, Taeniopterygidae
was limited to only the upper Animas, and was found in very low abundance. Some of these taxa are more
prevalent during the winter/spring season due to life history and the seasonal abundance of more developed
instars. Thus, they may be underrepresented during the summer/fall collections.
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Upper Animas
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EPA Gold King Mine Biological Response Report
Lower Animas
60
50
Q)
S 30
CO
*
10
10/28/2015 8/24/2016 9/30/2016
ADW-022
I
8/24/2016 10/1/2016
ADW-021
¦ Pre-release
8/24/2016 10/1/2016
ADW-010
¦ Post-release
_
8/27/2016 10/2/2016
FW-012
8/27/2016 10/2/2016
FW-040
Figure 5.8. Relative abundance of Baetis spp. within the Lower Animas from pre- and post-release sampling
events.
San Juan
50
45
40
35
30
to
O 25
CO
I
rH rH
O O
(N
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EPA Gold King Mine Biological Response Report
5.4 Summary of benthic macroinvertebrate assemblage data
Macroinvertebrate population indices show that aquatic communities have experienced substantial
degradation in the headwaters of the Animas River due to historical mining activities in the upper Animas
watershed. Water and sediment quality conditions improve with distance from the headwaters as cleaner
incoming tributary flows moderate impacts. Previous studies have documented historic and ongoing mining
impacts on water and sediment quality and aquatic communities in this area (USGS 2007; EPA 2015; EPA
2016c). Mining impacts are most prevalent and persistent in the upper Animas River segment from
Silverton to Durango, CO. The aquatic communities in the lower Animas and San Juan rivers, when
applying the Colorado and NRSA MMIs, generally show attainment of the aquatic life use and fair-good
conditions, respectively.
Habitat differences as well as water quality appear to influence individual community metrics such as the
Percent of Ephemeroptera, Plecoptera, and Trichoptera taxa (%EPT) and total taxa. The 550-kilometers of
the Animas and San Juan rivers affected by the GKM release have diverse habitats that affect the
distribution and abundance of macroinvertebrate and fish species along their length. Additionally, great
variability was observed among samples collected at the same local. This variability likely reflects the
natural fluctuation inherent in riverine benthic communities but also likely reflects differing sampling
methodologies.
This analysis focused on samples collected during an index period of June through October. No significant
changes to the summer/fall benthic macroinvertebrate assemblages due to the GKM release were observed
when comparing post-release and pre-release samples in the Animas or San Juan Rivers. These results are
consistent with analyses presented in MSI (2016, 2017). Potential changes in spring benthic
macroinvertebrate communities are also of interest since some studies have reported that effects of metals
are often greatest in spring during periods of elevated flow and increased metal concentrations (Clements
1994). MSI (2017) presented the analysis of the limited spring benthic macroinvertebrate s data collected
from two middle Animas River sampling locations (James Ranch and 32nd Street Bridge) and concluded
that the post-GKM release community was consistent with historic conditions.
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EPA Gold King Mine Biological Response Report
CHAPTER 6 FISH POPULATIONS
Fish population characteristics in the post-GKM release data (2015 and 2016) were compared to long term
trends in fish population surveys conducted in the Animas and San Juan rivers to determine how different
fish species and age classes responded to the GKM release. More specifically, were acute impacts to the
fish populations observed during the initial GKM release when metals concentrations were highest? Were
long-term changes in fish populations observed a year after the GKM release? Chapter 6 presents spatial
and temporal trends observed in large (adult) and small (small adults and fry) fish surveys. Our analyses
showed there were no significant impacts on adult fish population abundance in the Animas River after the
GKM release, potential impact to juvenile bluehead suckers near Durango, and inconclusive results in the
San Juan River.
6.1 Fish and wildlife studies in the Animas River
The most robust fish population and wildlife response data for the Animas River were collected by the
Colorado Parks and Wildlife (CPW), which included a sentinel fish toxicity study, intensified fish
population surveys, wildlife mortality survey, and partnering with CDPHE to measure metals in fish tissue.
Large fish surveys were conducted in the Animas River (Figure 6.1) near Durango (Reaches 1 and 2) and
four locations in the upper Animas: Teft Spur, Elk Park, A72 (Silverton, CO) and upstream of the Cement
Creek confluence near Howardsville, CO. The Howardsville site is a ""control" site not affected by the
GKM release. Small fish/fry surveys were conducted at seven locations on the Animas River. Two dead
beavers were collected and submitted to Colorado State University for necropsy. The results of the
laboratory analyses did not suggest that the beavers died of exposure to toxic concentrations of minerals or
metals. The cause of death was inconclusive. Results of the sentinel fish study and fish surveys follow. The
metals in fish tissue results are presented in Chapter 8.
Table 6.1 Summary of the GKM response sampling and data collected by Colorado Parks and Wildlife.
Study
Dates
Description
Sentinel
fish/water quality
data
8/6-8/10/2015
1.5-inch rainbow trout fry were placed in cages at three sites in the
Animas River and one control site for four-days. Water-quality
samples were periodically collected at cage sites to measure metals
exposure.
Fish surveys
8/24-8/27/2015
Large fish surveys near Durango (Reaches 1 & 2)
September 2015
Small fish surveys (7 Animas River sites)
9/8-9/10/2015
Large fish surveys (Howardsville, A72, Elk Park, Teft Spur)
3/18/2016
Large fish surveys near Durango (Reaches 1 & 2)
7/19-7/20/2016
Small fish surveys (7 Animas River sites)
9/14-9/16/2016
Large fish surveys near Durango (Reaches 1 & 2)
Survey for fish and
wildlife mortality
8/16/2015
CPW staff rafted sections of the Animas to survey for fish kill or
other impacts. Two dead beavers were collected and submitted for
necropsy. Six dead fish were collected.
Metals in fish
tissue
8/14/2015
Five brown trout and five rainbow trout were collected from the
Animas near Durango. Filets were submitted to CPDHE for testing.
3/18/2016
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Legend
'•/ Gold King Mine
~ City
• Large Fish Survey Sites
• Small Fish Survey Sites
Large Fish Survey Reach 1
Large Fish Survey Reach 2
Stream
Animas Watershed
Indian Land
Cement
A
Creek
SILVERTON
~
/
A72r=-*
Howardsville
Elk Park p"**
Teft Spur
Colorado
Bakers Bridge
TACOMAtV ^
: £
£
[$
"1 y
Trimble Bridge
Durango High School
YV
Durango Mall
H
Basin Creek L—
Weaselskin Bridge
DURANGO
\ '
I
Southern Ute
Indian Reservation
High Flume Canyon
10 15, 20
km
A
Figure 6.1. Map depicting CPW large and small fish survey locations on the Animas River.
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EPA Gold King Mine Biological Response Report
6.1.1 Sentinel fish study
CPW placed three cages that each contained 12 trout fry (1.5 inches) at three locations in the Animas River
(32nd St. Bridge, the Hatchery, and High Bridge) and five cages at a control site (Junction Creek) as the
plume moved through Durango, CO from 8/6-8/11/15. The 96-hr exposure to the GKM plume would be
considered similar to the duration of acute toxicity tests typically used in the derivation of water quality
criteria. Cages were checked three times a day for the condition of the fish (e.g., responsiveness) and
mortality. Water samples were collected in the morning and afternoon and more frequently at hatchery site
during plume's passing and analyzed for a suite of total/dissolved metal concentrations. Although metal
concentrations rose and pH fell at the Animas River locations as the plume passed (e.g., from almost 8 to
7.3 at the hatchery), only limited fish mortality was observed. Of the 108 fish that were deployed in the
GKM plume, 2 mortalities were observed at the most downstream location. Death of the fry appeared to be
related to handling of the fish rather than the GKM release (Appendix D). In addition, no widespread fish
kills were reported on the Animas River during or after the GKM release. The low trout fry mortality is
consistent with the water quality criteria exceedance analyses that indicated the peak metal concentrations
observed in the Durango area were not acutely toxic to fish (see Section 2.3.3; Figure 2.12).
6.1.2 Fish population data
Pre- and post-GKM fish population data were collected by the Colorado Parks and Wildlife (CPW) agency
using electrofishing in the fall at various locations on the Animas River (Figure 6.1), as described in
Section 6.1. For Reaches 1 and 2 near Durango, the original dataset included samples taken as early as
August 1912. The pre-release conditions included on surveys done every few years during the period 2002-
2016. For the other four large fish survey sites, we examined data from sampling in 1992, 1998, 2005,
2010, 2014, and 2015 (after the GKM release). These data represent either the total count of fish caught
during sampling events (Reaches 1 and 2), or the density of fish (fish/mile). For the former count data, the
level of effort (total stream length sampled) was consistent from year to year, allowing for annual
comparisons to be made. For Reaches 1 and 2, we focused our examination on native species and the
recreationally-important salmonids: bluehead sucker, flannelmouth sucker, mottled sculpin, brown trout
and rainbow trout. We plotted count data (summed across both reaches) through time to assess whether
post-GKM release samples collected in 2015 and 2016 indicate a departure from pre-GKM release
conditions. Brook trout were the only targeted species at the four other survey sites. Data indicated virtually
no fish caught at A72 or Elk Park since 2005, so only data from Teft Spur and Howardsville were
examined.
We also looked at data from CPW small fish electrofishing surveys at seven different locations on the
Animas River (Figure 6.1). These were multi-pass depletion surveys along 100 meter sections of shoreline
in shallow water where trout fry would normally be found. The most upstream location is near Baker's
Bridge, and the most downstream location is about ten miles from the Colorado/New Mexico border on the
Animas (High Flume Canyon). These surveys have been done periodically since 1996, and are typically
done in July. An extra collection effort was made in September 2015, about a month after the GKM release.
6.1.3 Temporal patterns of fish populations in the Animas River
Sampling at Teft Spur indicates that brook trout populations dropped between 2005 and 2010 (Figure 6.2).
This may be related to the cessation of remediation activities of the Gladstone treatment plant on Cement
Creek in 2004 (CPW 2015, MSI 2017). The number of brook trout caught at Teft Spur in 2015 (post-GKM
release) was slightly greater than in 2014 and 2010. At Howardsville, brook trout density was slightly
greater in 2015 compared to 2014, but about half the density seen in 2005 and 2010.
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EPA Gold King Mine Biological Response Report
1200
Howardsville
Figure 6.2. Density of brook trout caught near Howardsville, CO and Teft Spur in surveys conducted by the
Colorado Department of Parks and Wildlife.
In Figure 6.3 (and later in Figures 6.8 and 6.9), dashed blue boxes denote pre-release "norms" of species
abundance. The upper and lower bounds of these rectangles depend on the number of pre-release samples.
With less than 10 samples, the largest and smallest pre-release values define the upper and lower rectangle
boundaries. For 10-20 samples, the highest and lowest pre-release values were discarded and the 2nd highest
and 2nd lowest values define the bounds. Using this methodology, we then determined if the number of
individuals caught during 2015 and 2016 (shown on the plots using red triangles) were outside the range
defined by pre-release data.
Fish counts were generally within the pre-release ranges, and no counts were low except for rainbow trout
in 2016 (Figure 6.3), which was slightly less than the pre-release low in 2010 (93 versus 98). However, the
2016 count is well within two standard deviations of the average number caught between 2002-2014, so
statistical significance was minimal. Also, effects of the GKM release on trout populations in the Durango
area were confounded with the annual autumn stocking of rainbow and brown trout. Rainbow trout
stocking in the fall of 2016 was low due to a shortage of hatchery fish (Appendix D). In 2015, nearly all
trout stocking was completed prior to the GKM-release, so the 2015 survey results for trout reflected
typical stocking rates. Overall, adult fish within these populations appear not to have been affected by the
GKM release.
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EPA Gold King Mine Biological Response Report
250
Bluehead Sucker
150 :
8 8
vD 00
8 8
fM fM
30
25
20
Flannelmouth Sucker
fM fM
8 8
Rainbow Trout
Brown Trout
600
M 400
5 200
250
Mottled Sculpin
=> 250
Figure 6.3. The number of common native fishes and important salmonids caught from the Animas River near
Durango, CO (Reach 1 & 2 in Figure 6.1) in surveys conducted by the Colorado Department of Parks and
Wildlife. Blue dots are pre-GKM release samples. Red triangles are post-GKM release samples. The blue dashed
rectangles in each figure denotes pre-GKM release survey ranges.
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EPA Gold King Mine Biological Response Report
Comparisons of the pre- and post-release small fish survey results provided insight into potential impacts to
metal sensitive taxa (i.e., mottled sculpin) and life stages. Figure 6.4 shows the brown trout fry and mottled
sculpin density (Man) before and after the GKM release. The survey in September 2015, weeks after the
GKM release, captured 20% less trout fry than in July 2015, and 11% less than July 2016. This decrease in
trout fry density could be related to the GKM release, but is more likely explained by the seasonal
movements of fry out of shoreline areas and into deeper pools in September and the lower flow in
September (CPW 2015), given the lack of mortality in the sentinel fish study. Figure 6.4 also shows that the
density of mottled sculpin seen in the small fish surveys does not indicate impact from the GKM release.
The shallow, graveled, shoreline habitat sampled in the small fish surveys is considered a more accurate
representation of mottled sculpin densities than the large fish surveys, which target larger fish in deeper
water (Personal communication, Jim White, CPW Aquatic Biologist).
Average Brown Trout Fry Density
800
700 -
600
500
ra 400
S 300 -
200
100 -
1996-1999 July Pre-GKM July 2015 Sept 2015
July 2016
4000 -
3500 -
E 3000
2500
U
OJO
2 2000
0)
S. 1500
1000
500 -
0
Average Mottled Sculpin Density
N=7
N=28
I
6.2
1996-1999 July Pre-GKM July 2015 Post-GKM Sept 2015 Post-GKM July 2016
Figure 6.4. Top: the average density (#/km) of brown trout fry caught at seven Animas River sampling
areas by CPW in the late 90's compared to surveys in 2015 and 2016. Error bars are +/- one standard
error of the mean. Bottom: the density of mottled sculpin caught in those same shoreline small fish
surveys.
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EPA Gold King Mine Biological Response Report
Relative abundance of bluehead sucker in the Animas River near Durango, plotted by total fish length and
averaged from 2002-2014, 2015 (post-GKM release) and 2016 is shown in Figure 6.5. The relative
abundance of adult fish in 2015 was similar to the pre-GKM release conditions, but an absence of fish less
than 200 mm in the 2016 data was apparent.
Bluehead Sucker
18
16
14
Q)
u
£
12
73
£
3
10
-Q
<
8
>
¦*->
J2
Ol
6
Cd
4
2
0
¦ 2002-2014
~ 2015 Post-GKM
¦ 2016
jl fi l.Jl.ft,- 'J Jj'AMJIJ.H
LO LO LO LO lO lO lO LO LO lO LO lD lD
OfN^UDCOOrsl^T'XiOOOfN'sr
t—I t-I t-H t-I t-1 (N fN fN fN fN CO fO CO
Total Length (mm)
Figure 6.5. Relative abundance of bluehead sucker in the Animas River near Durango (Reach 1 and 2 in
Figure 6.1) for pre-release (2002-2014) compared to the fall of 2015 and 2016.
6.2.1 Summary of CPW survey data
No widespread fish kills were reported on the Animas River during or after the GKM release. The CPW
sentinel fish cage study confirmed that the GKM release was not acutely toxic to fish. Additionally, we did
not find any evidence of declines in the number of adults sampled from the Animas River in 2015 and 2016
for any of the species we reviewed (Figure 6.2 and 6.3).
The lack of evidence of a negative response on adult populations the year following the GKM release does
not address potential longer-term impacts. The GKM release may have been more stressful on larval and
juvenile fish (Figures 6.4 and 6.5); however, CPW saw evidence of reproduction by native species (mottled
sculpin, bluehead sucker) in the months following the release, suggesting that the GKM release was not
acutely toxic to younger life stages (CPW 2015). Our review of the bluehead sucker data, which includes
an additional year of monitoring (2016), shows a lack of juvenile bluehead sucker (< 200 mm)(Figure 6.5)
while population abundance has remained within the range of pre-GKM release conditions (Figure 6.3).
For trout species, impacts on younger life stages were challenging to identify since population levels are
primarily determined by stocking and harvest rates established by the state of Colorado (Appendix D) and
not the recruitment of larvae and juveniles.
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6.3 Fish abundance in the San Juan River
A long funning dataset on fish abundance collected by the US Fish and Wildlife Service on the San Juan
River from Blanco, NM to the Clay Hills boat ramp in Utah (Figure 6.6) was analyzed to compare the post-
GKM release samples in 2015 and 2016 to data from 2000-2014. Fish were captured using raft
electrofishing, and the duration of the sampling period (in seconds) was used to standardize the number of
fish caught into a catch-per-unit-effort (CPUE) metric. The USFWS performs these surveys in September
and October each year so between-year comparisons are seasonally comparable. Typical sampling duration
was 20-30 minutes. We focused our analyses on four native species frequently seen across time and sites:
flannelmouth sucker (FMS), bluehead sucker (BHS), razorback sucker (RZS) and speckled dace (SPD).
The theoretical foundation for changes in fish abundance would be that the increased levels of dissolved
metals (primarily aluminum and iron) seen in the San Juan River in the fall of 2015 through the spring
snowmelt period of 2016 could be an irritant, causing fish to emigrate from these areas. There is a weir and
low-head dam in the few miles downstream of Fruitland on the San Juan (SJFP), and these features could
serve to inhibit the movement of fish from this area to the area upstream (LVW-020).
Utah
0 c/, „ Mexican Hat >>-
J
il %
Utc Mountain lite Tribe Reserv
"J~Lr r r— ~lA *
J J7J
h. ^
Bluff
^—-- _r /
gje® ' SjMc viAneth
.A
# %
ition
Cc
^ r
~jP
lite Mountain Ute
Tribe Reservation
1 ?
7 /
lorado
\ ?
\ jr
y f
/Southern lite '
Indian Reservation
-i l) 1
Legend
_ Fish Sampling Reach Endpoints
(Distances in miles)
• Water Quality Sampling Sites
* City
Stream
Indian Land
1 State Boundary
b)
f
J
Navajo Nation
Arizona
1
0 15 30 km
1 i i « 1
237*
%
L Shiprock _ . . .
• . Fruitland
158 6 SJFP le^Tvi^
A *{ Nev
i i
3 7
3\
) W
^ Farmington Blanco 5-
0 180 6 " gjfrB 204
v Mexico
Figure 6.6 Nine segments of the San Juan River that have been historically sampled to assess fish abundance by
the USFWS. Mile markers are given below each reach endpoint. Only one region, SJAR, is upstream of the
confluence of the San Juan and Animas River.
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EPA Gold King Mine Biological Response Report
6.3.1 Longitudinal patterns of fish populations in the San Juan River
Three species (BHS, FMS, SPD) showed the same a)
longitudinal pattern of abundance in the 2000-2016
population sampling. Figure 6.7A shows the average
catch per hour of sampling effort (CPUE) of FMS.
As with the other two species, FMS are most
abundant at sites immediately downstream of the
confluence with the Animas River (LWV-020 and :
SJFP) and decline longitudinally along the length of
the San Juan. However, these species are still present
in low numbers as far downstream as Clay Hills <
more than 300 km from Farmington. These species
are also found in much lower abundance upstream of
the confluence with the Animas River (SJAR). These
species are likely responding to temperature
gradients within the San Juan, with the sites closer to
the Animas River confluence being warmer at the g)
time of sampling than either sites upstream or farther
downstream of the confluence. Upstream of the
Animas confluence (~55km), the San Juan receives
the cool hypolimnetic waters discharged from
Navajo Lake.
x
Razorback sucker is listed as federally endangered, ;
and a formal management plan exists for assisting its
recovery to historic levels. The plan (fully j
implemented in 2009) includes a decades-long
stocking program that introduces fish at a variety of J
sites in the middle to lower San Juan. The average
CPUE for razorback sucker are shown in Figure 6.7B
peaks at Fruitland, suggesting that the weir and dam
downstream of Fruitland may limit upstream q
migration of razorback sucker to the LVW-020
segment in Farmington.
Channel catfish, a competitor of the other species, is
found in increasing abundance moving downstream
from Fruitland to Bluff, UT, and then declines
moving farther down to Mexican Hat and Clay Hills
(Figure 6.7C). The Colorado pikeminnow (not
shown) is observed occasionally at low abundance at
various locations along the length of the San Juan
River.
Flannelmouth Sucker (2000-2016)
Razorback Sucker
(2000-2016)
O
O
O
O
O o
Channel Catfish
(2000-2016)
50
45 -
40
35
30
25
20 -
15 -
10
5 -
f /"
Figure 6.7. The average CPU for A) flannelmouth
sucker, B) razorback sucker, and C) channel catfish
at sampled reaches of the San Juan River averaged
from 2000-2016.
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EPA Gold King Mine Biological Response Report
6.3.2 Temporal patterns of fish populations in the San Juan River 2000-2016
BHS, FMS, and SPD were commonly observed throughout most of the San Juan River but varied in
abundance longitudinally along the river (Figure 6.7). The temporal patterns of the average catch per unit
effort (CPUE) of these three species is shown in Figure 6.8, for three groupings of sites with similar species
abundance. Figures 6.8A, B, and C (top row) include sites located in the upper San Juan where these three
species were found at highest abundance (LVW-020 and SJFP). Data for sites where these species were
observed at intermediate abundance in the middle reaches of the San Juan River (SJSR, SJ4C, SJMC and
SJBB) are shown in Figure 6.8D, E, and F (middle row). Data at low abundance sites in the lower San Juan
River (SJMH and SJCH) are shown in Figure 6.8G, H, and I (bottom row). The reference site (SJAR),
located upstream of the GKM influence, is not included. As in Figure 6.3, the dashed blue rectangles define
"norms" based on pre-release data. Due to a larger historic sample size, the largest and smallest pre-release
observations were excluded from defining the pre-release range (see section 6.1.2 for further explanation).
The temporal trends in population estimates for RZS are shown grouped by high abundance (SJFP and
SJSR) in Figure 6.9A and low abundance sites (SJ4C, SJMC, SJBB, SJMH and SJCH) in Figure 6.9B. The
blue rectangle denotes norms for pre-release data (2000-2014) to give context to the CPUE measures seen
in 2015 and 2016. RZS populations were not examined at LVW-020 or at SJAR, which is upstream of the
Animas River. Temporal trends in abundance of channel catfish and Colorado pikeminnow are shown in
Figure 6.9C and D.
The average CPUE in surveys at San Juan River sites in 2015/2016 (Figures 6.8 and 6.9) were generally
within pre-release norms. However, abundance of BHS and FMS were low, especially at intermediate
abundance sites (Figure 6.8D and E). Longer terms trends of CPUE reductions in BHS, FMS, and SPD are
apparent in a number of these plots. Low 2015/2016 CPUE for these species is concurrent with high
abundance for the species shown in Figure 6.9. RZS CPUE in 2015/2016 was at or near pre-GKM release
highs in the San Juan (Figure 6.9A and B), channel catfish CPUE in 2015/2016 was above the pre-GKM
release median of 30 (Figure 6.9C), and Colorado pikeminnow CPUE in 2015/2016 was also well above
the pre-GKM release median of 0.07 (Figure 6.9D). Ecological interactions (these species are either
competitors with or predators on BHS/FMS/SPD) thus play a confounding role. As stated earlier, if
changes in water quality and sediments were more stressful/impactful on age-0 and juveniles of these
species, reductions in adult populations may not be evident for several more years. Both RZS and Colorado
pikeminnow are currently under conservation management plans, and appreciable numbers of both species
are annually stocked into the San Juan River.
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EPA Gold King Mine Biological Response Report
A)
B)
Flannelmouth Sucker
Bluehead Sucker
O o
O O
o
c)
Speckled Dace
High Abundance Sites
o
o
©
o
O o
o
o
5 o o
o A *
,0,^ .
§gggfggggg222!
D)
Flannelmouth Sucker
Intermediate Abundance Sites
60
5
2- 40
E)
Bluehead Sucker
Intermediate Abundance Sites
ooooooooooooooooo
QOOO©OOOOOMi-**»*»*»*»'
F)
Speckled Dace
Intermediate Abundance Sites
oooooooooo
oooooooooo
G)
W 15
5
S. 10
Flannelmouth Sucker
Low Abundance Sites
o ° °
o
A :
o
a:
o
©
©
§ | g
© o © o ©
© © © o
H)
Bluehead Sucker
Low Abundance Sites
©
o
o
o o
-A*i
Speckled Dace
Low Abundance Sites
0000000000>-)->-<>-*>-M
Figure 6.8. Average CPUE for flannelmouth sucker, bluehead sucker, and speckled dace at A-C) high
abundance sites (LVW-020 and SJFP), D-F) intermediate abundance sites (SJSR, SMC, SJMC, and SJBB), and G-l)
low abundance sites (SJMH and SJCH) during the years 2000-2016. Values are the average CPUE across sites in
the abundance category. Red triangles highlight samples from 2015 and 2016. Dashed blue boxes indicate pre-
GKM release ranges of CPUE estimates.
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EPA Gold King Mine Biological Response Report
A)
B)
Razorback Sucker
High Abundance Sites
Razorback Sucker
Low Abundance Sites
c)
Channel Catfish
£ 100
in 60
o o
D)
Colorado Pikeminnow
Figure 6.9. Average CPUE for 2000-2016 for A) razorback suckers at high abundance sites (SJFP and SJSR), B)
razorback sucker at low abundance sites (SJ4C, SJMC, SJBB, SJMH, and SJCH), C) channel catfish at all sites, and D)
Colorado pikeminnow at all sites. Values are the average CPUE at sites in the abundance category. Red triangles
highlight samples in 2015 and 2016 after the GKM release. Dashed blue boxes indicate pre-GKM release ranges of
CPUE estimates.
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EPA Gold King Mine Biological Response Report
CHAPTER 7 METALS IN BENTHIC MACRO INVERTEBRATE TISSUE
Bioaccumulation of metals in benthic macroinvertebrate tissue post-GKM release was assessed with
samples collected by the EPA and the NMDGF. In Chapter 7, we explore the spatial and annual variability
in benthic tissue metal concentrations and differences in benthic tissue concentrations among taxonomic
groups as they relate to the passing of the GKM plume, the presence of GKM metal deposits, and pre-GKM
release tissue concentrations. Analyses that could conducted with these data were limited by the availability
of pre-release data, collection dates, and differences in sampling methodology, analytical methods, and
laboratories between years. For example, EPA benthic macroinvertebrate tissue samples were a composite
of all taxonomic groups and were collected with the fall assemblage sample. NMDGF samples were sorted
and analyzed by taxonomic group and represent two seasons (fall and spring). Statistical analyses were
limited to locations that were sampled with the same methods. Additionally, all samples were frozen
following collection and likely included substantial quantities of organic detritus and/or mineral sediment
in their gut contents. These samples are most relevant to estimating metal exposure to higher-trophic level
organisms for ecological risk assessments since invertebrates are ingested whole. The inclusion of gut
content and in some situations caddisfly casings, in the tissue sample made it difficult to quantify
differences in benthic macroinvertebrate exposure to bioavailable metals. Additional information on the
ecological risk associated with metals in tissue sampled from the Animas River is available in the Upper
Animas Mining District: Draft Baseline Ecological Risk Assessment (EPA 2015).
Our analyses showed benthic tissue samples collected from the upper Animas after the GKM release in
September 2015 had significantly greater copper and lower manganese concentrations when compared to
pre-release concentrations. All other changes in metal concentrations from 2014 were not statistically
significant and were within the range of potential sample variability. In the lower Animas and upper San
Juan rivers, some metals were elevated at the lower Animas sites in August when compared to the San Juan
and samples collected the following spring.
7.1 EPA benthic macroinvertebrate tissue data
EPA contractors collected benthic macroinvertebrate
tissue samples post-GKM release in 2015 and the
following fall in 2016. In 2015, samples were collected
from 9 sites in the upper and middle Animas River,
including the upstream location A68 down to AR19-3
(104 RKM). In 2016, EPA contractors sampled a total
of 29 sites in the Animas and San Juan rivers, which
included three upstream/tributary locations (A68, M34,
and SJAR). Most metals were measured at
concentrations that were detectable with the analytical
method used, except for mercury, silver and vanadium
(Table 7.1).
In the upper Animas River, pre-release data were
available for a limited number of sites to conduct a pre-
and post-GKM release comparison of metals in benthic
macroinvertebrate tissue. Four locations were sampled
in 2012 (A68, M34, A72 and Baker's Bridge) and five
locations were sampled in 2014 (A68, A72, A73,
A75D, Baker's Bridge). All benthic macroinvertebrate
data were normalized to a common unit of expression
prior to analysis. The 2016 EPA samples were reported
as |ag of metal per gram of dry tissue, or jj.g/g dry
Table 7.1 Total number of benthic
macroinvertebrate tissue samples (pre- and post-
GKM) and percent detection by analyte.
All Data
N
% detected
Percent Solids
33
100
Aluminum
46
96
Antimony
46
70
Arsenic
50
88
Cadmium
50
98
Chromium
50
98
Copper
50
100
Iron
46
96
Lead
50
100
Manganese
46
100
Mercury
50
68
Nickel
46
87
Selenium
50
80
Silver
46
70
Tin
32
100
Vanadium
46
70
Zinc
50
100
75
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EPA Gold King Mine Biological Response Report
weight (dw) or ppm dw. The August post response samples collected in 2015 and pre-release samples
collected in 2014 from the upper Animas River were reported at pg of metal of tissue "as received", which
is equivalent to a wet weight (ww) concentration since samples were not dried prior to analysis.5 The 2014
and 2015 samples had insufficient biomass to analyze for percent solids given the overall low numbers of
invertebrates found at the site. For these samples, the dw concentrations were estimated using the percent
solids measured at that location in 2016 or the mean percent solids when more than one sample was
available, including the 2012 and 2016 duplicate samples. No percent solid data were available for the
James Ranch and Oxbow Park sampling locations. Therefore, the dry weight concentrations for the 2015
samples collected from James Ranch and Oxbow Park were estimated using the mean percent solids of all
Animas River sampling locations (Animas River mean = 23.4%, range = 15.9%-33.5%; San Juan River
mean percent solid = 14%, range = 8.5%-22.7%). Results that were reported between the method reporting
limit (MRL) and the method detection limit (MDL) were set to the estimated detected value. Results with
concentrations less than the MDL are presented at the MDL.
Field duplicate samples were collected at two locations in the Animas River (Rotary Park and FW-020) and
one location in the San Juan River (SJCH). The collection of duplicate samples at a sub-set of the sampling
locations is a standard QA/QC practice to document the precision of the sampling process. Field duplicates
are used to assess homogenization of the samples in the field, reproducibility of sample preparation and
analysis and, heterogeneity of the matrix by calculating the relative percent difference (RPD), which was
calculated as:
RPD = 100*([field duplicate]-[sample])/mean[field duplicate, sample])
Since site-replicate samples were not collected, the RPD was also used in this analysis to evaluate potential
within site variability (see Chapter 7.3). Comparisons of the RPDs by site and metal showed high inter- and
intra-site variability of metals in benthic macroinvertebrate tissue. The greatest intra-site variability was
observed in the SJCH and FW-012 samples. Some of the variability is likely attributed to the difference in
the % solids measured in FW-012 and SJCH samples (Figure 7.1) and the low tissue mass collected for
analysis, which was especially true at SJCH where habitat transitions from lotic to lentic. The total mass of
tissue in the SJCH sample and the field duplicate was 1.77 lg and 0.884g, respectively. High intra-site
variability in the EPA benthic macroinvertebrate tissue data highlights the complexity of metal
bioaccumulation, challenges with quantifying changes in tissue concentrations over time, and sample
characteristics that limit our ability to detect statistical differences.
200%
160%
140%
120%
100%
80%
60%
40%
20%
Relative Percent Difference:
2016 Benthic Macroinvertebrate Sample & Field Duplicate
Si*
j
n
n
r
ri
fin
1 L
i
n
n
n
n
n
n 1
n
Solids
~ Rotary Park
m FW-012
E3SJCH
Al
As
Cd
Cr
Cu
Fe
Pb Mn
Hg
Se
Zn
Figure 7.1 Comparison of the absolute value of the relative percent difference in benthic macroinvertebrate
tissue by metal and sampling location. Relative percent difference was calculated as the difference between the
sample result and the duplicate results divided by the mean of the sample and duplicate result.
5 Expressing the result "as received" accounts for the wet weight measured in the lab. It acknowledges that there was
likely some water loss from the sample resulting from freezing and transportation to the lab prior to analysis.
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EPA Gold King Mine Biological Response Report
7.2 Pre- and post-GKM release comparisons of upper Animas benthic tissue
data
Pre-release benthic macroinvertebrate tissue data
were available for six sites on the upper Animas
River, allowing for a pre- and post-GKM release
comparison of metals in benthic tissue. All benthic
tissue samples were collected between late
September and early October, which minimizes
potential variability due to seasonal differences in
metal bioaccumulation. The 2014 data were first
presented in the Baseline Ecological Risk Assessment
(EPA 2015) and an analysis of the 2014 pre- and
2015 post-GKM release data was prepared by MSI
for EPA following the GKM release (MSI 2016).
Differences in sample processing and laboratory
analyses between years limited our ability to quantify
differences observed between the pre (2012 and
2014) and post (2015 and 2016) samples, and the
statistical analyses that can be performed (see
Section 3.4.3 and Table 3.4). However, similarity in
the 2014 and 2015 field and laboratory methods
allowed for statistical comparison of those results,
which are presented below and in MSI (2016).
Table 7.2. Mean metal concentrations in benthic
macroinvertebrate tissue samples collected from
the upper Animas River (A68, A72, A73, A75D and
Baker's Bridge). Non-detects samples were set to
the MDL * indicates when all samples were below
the MDL. MDLs can change over time, when
different analytical methods are used, and between
laboratories.
Mean Concentration
(ppm dw)
Pre-GKM
Post-GKM
2012
2014
2015
2016
Aluminum
NA
874
997
9430
Arsenic
7.1
1.5
0.8
7.6
Cadmium
9.4
2.3
1.7
6.5
Copper
173.3
47
102
119
Iron
NA
2983
3217
19715
Lead
198
13
11
170
Manganese
NA
242
134
3292
Mercury
0.06
0.37*
0.13*
0.03
Nickel
NA
1.34
0.75
6.26
Selenium
1.17
1.86
1.45
1.30
Zinc
3376
504
440
1660
Figures 7.2 and 7.3 present benthic
macroinvertebrate tissue concentrations sampled
from the upper Animas River though the middle
Animas RKM 150. Pre-GKM release data were
limited to the upper Animas sites of A68, A72, A73,
A75D and Baker's Bridge, and the tributary site M34. Results at RKM 0 in the figures represent the
upstream sampling location on the Animas River (A68) and Mineral Creek (M34). In general, when
differences in concentration are observed between years, the 2014 and 2015 results are more similar than
the 2012 and 2016 (Table 7.2).
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EPA Gold King Mine Biological Response Report
O 2012 0 2014 ~ 2015 A 2016
~
10 A
Arsenic: Macroinvertebrates
A
o <>
~
~ ~
Aluminum: Macroinvertebrates
100,000
A
10,000 a 4 A A
~ £
1,000 c ~
% T ~
M4 a
25 50 75 100 125 150
Distance from GKM (km)
25 50 75 100 125 150
Distance from GKM (km)
100
5
"O
E 10
g 1 O
Cadmium: Macroinvertebrates
A
o
~
* A
A
~
25 50 75 100
Distance from GKM (km)
125
150
1,000
$
"O
E 100
Copper: Macroinvertebrates
* i ~
O A
I *
o ~
AO
O
~~
O
A*
A
*
~
A
A
j
J
j
*
25 50 75 100
Distance from GKM (km)
110,000
E
100
10
Iron: Macroinvertebrates
V A A
~ o -
o
25 50 75 100
Distance from GKM (km)
1,000
10
Lead: Macroinvertebrates
25 50 75 100
Distance from GKM (km)
125
Figure 7.2. Comparison of pre (2012&2014) and post (2015 &2016) GKM release arsenic, aluminum, cadmium,
copper, iron and lead concentrations in benthic macroinvertebrate tissue samples collected from the upper and
middle Animas River. Pre-release data were limited to sites sampled upstream of 65 RKM. Sites located at 0
RKM represent the upstream and tributary sites, A68 and M34, respectively. Open symbols = MDL. The 2012
samples were not analyzed for aluminum and iron.
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EPA Gold King Mine Biological Response Report
O 2012 o 2014 ~ 2015 A 2016
100,000
Manganese: Macroinvertebrates
1.0000
Mercury: Macroinvertebrates
o
10,000 A
1,000
A
t
° ~
~
10
25
A M
A A A
~
w
A
~ A—
O
~
50 75 100 125
Distance from GKM (km)
| 0.1000
£
0.0010
T o v
o
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EPA Gold King Mine Biological Response Report
A comparison of concentrations at sampling location immediately up and downstream of a given location
showed localized elevated tissue concentrations in the upper Animas. Elevated Al, Ba, Fe, K, and Pb were
measured in benthic tissue collected in 2015 from the depositional habitat at Oxbow Park (90 RKM) (MSI
2016). Oxbow Park was not sampled in 2016 to determine if the high concentrations continued the
following year; however, the 3 nearest downstream locations (32nd St. Bridge;91.8 RKM, Rotary Park; 94.2
RKM, and GKM05; 96.5 RKM) generally had similarly high metal concentrations in benthic tissue. In
2016, the greatest concentrations of As, Al, Cu, Fe, Pb, Ni, and Zn in benthic tissue were observed further
upstream at site 9426 (76.8 RKM). Pre-GKM release data were not available at any of these sites for a
comparison to post-release concentrations.
The 2015 benthic macroinvertebrate tissue samples were collected within the closest timeframe of the
GKM plume and when GKM sediment deposits were still present in the upper Animas (EPA 2016c). Five
sites in the upper Animas River had 2014 and 2015 samples suitable for statistical comparisons (A68, A72,
A73, A75D and Baker's Bridge). Given the limited sample size (i.e., n = 4; a single sample from each
location and date) and the lack of sample replicates, percent differences between 2014 and 2015 metal
concentrations were evaluated with both a non-parametric Wilcoxon signed-rank test and a two-tailed t-
test. Eight metals deemed most biologically significant in the GKM release were examined: aluminum,
arsenic, cadmium, copper, lead, iron, manganese, and zinc.
Percent Difference = 100*(C2oi5-C2oi4)/C2oi4
Where C is the natural logarithm of the metal concentration, with a value of 1.0 added to the concentration
prior to logging so 2014 concentrations near zero will not cause the fraction to dramatically increase. The
mean percent difference across the four sites was also compared to the mean relative percent difference
calculated from the natural log+1 transformed 2016 Animas River sites from duplicate samples (see
Section 7.1), as well as the change in concentration that was observed at the upstream location A68. The
percent differences calculated for each metal and sampling location are presented in Figure 7.4.
The mean percent difference in benthic macroinvertebrate tissue concentrations was not significantly
different for most metals, except for copper and manganese (Table 7.3). Results of the t-test indicate that
copper was significantly greater (p=0.005) and manganese was significantly lower in 2015 (p = 0.04). Both
copper and manganese were borderline significant when evaluating the differences with the non-parametric
test (p=0.07). A comparison of the change in copper concentration by location showed copper increases
ranging from 20-37% at the four sites downstream of GKM and a smaller, 1% increase was observed at the
upstream location A68 (Figure 7.4). This trend was also observed with manganese, except concentrations
were lower in 2015. The absolute value of the percent difference in copper and manganese was also greater
than the within-site sample variability (last column of Table 7.3). These multiple lines of evidence suggest
that the changes in copper and manganese concentrations were associated with the GKM-release. MSI
(2016) also identified a statistically significant increase in copper in benthic macroinvertebrates when
evaluating the non-transformed mean 2015 and 2014 concentrations (paired t-test; p = 0.0339).
With respect to the other metals with non-significant differences (Al, As, Cd, Fe, Pb, Zn), the four
downstream locations experienced a mix of increasing and decreasing concentrations that canceled each
other out, leading to the non-significant results (Figure 7.4). A different pattern of changing metal
concentrations was observed at the upstream location A68. These metals remained the same or declined;
however, the absolute value of the mean difference was less than or similar to the potential sample
variability, suggesting the differences in concentration may be within the range of variability expected at
the site.
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EPA Gold King Mine Biological Response Report
Table 7.3. The mean difference in metal benthic macroinvertebrate concentration between the pre-release (2014)
and post-GKM (2015) samples collected from the upper Animas River (A72, A73, A75D and Baker's Bridge), results
of the statistical comparisons of the percent change, and potential sample variability. P-values less than 0.05
indicate a result significantly different from zero. Potential sample variability is equal to the mean relative percent
difference calculated from the natural log -transformed 2016 Animas River sites with duplicate samples (see Section
7.1).
Mean % Difference of Wilcoxon „ „ ^ Potential
I -1 est
Ln(l+Concentrations) Signed-Rank Sample
Analyte (2015-2014)/2014 p-value p-value Variability
Aluminum (Al)
5%
0.14
0.18
3%
Arsenic (As)
-1.5%
0.72
0.94
8%
Cadmium (Cd)
-4.7%
0.72
0.80
25%
Copper (Cu)
30%
0.07
0.005
9%
Iron (Fe)
6%
0.14
0.09
3%
Lead(Pb)
-8%
0.47
0.48
11%
Manganese (Mn)
-17%
0.07
0.04
3%
Zinc (Zn) 2% 0.72 0.60 6%
Benthic Macroinvertebrate Tissue
Upper Animas (2014-2015}
u 70
+
tH
c' 50
8 30
I 10
5 -10
§ -30
I -50
-70
A68
A72
A73
A75D
Baker's Bridge
*
*
*
*
—1-
1 .
1
1
¦ =
¦
¦¦¦ ¦
¦n
¦
¦
¦ mm
¦
M"
U1 D
i =
m
:$
=1
**
**
§1
* *
1
**
-
¦ Aluminum DArsenic ¦ Cadmium I Copper Blron = Lead 1 Manganese HZinc
Figure 7.4 Percent difference calculated from the natural log transformed pre-GKM release (2014) and post-
GKM release (2015) data collected from the upper Animas River. * identifies a statistically significant
increase in copper (p = 0.005) and ** identifies a statistically significant decrease in manganese (p = 0.04).
Metal concentrations in benthic macroinvertebrate samples collected from the upper Animas River in 2016
were generally elevated when compared to 2014 and 2015 results (Table 7.2). The elevated concentrations
in 2016 were observed throughout the watershed, including the upstream and tributary sites, suggesting that
something other than the GKM release contributed to the high metal concentrations (Figures 7.2 and 7.3).
A comparison of metal concentration in benthic tissue by sampling year showed the highest concentration
of cadmium, copper, lead, and zinc were measured in the pre-release samples collected in 2012. The
greatest concentrations of aluminum, arsenic, iron, manganese, and nickel were measured in the post-GKM
release samples in 2016; note that of these five parameters, only arsenic was measured in 2012. The highest
mean selenium concentration in benthic macroinvertebrate tissue was observed in the pre-release samples
collected in 2014 (Table 7.2). We were unable to compare mercury concentrations between years due to
differences in the method detection limits.
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EPA Gold King Mine Biological Response Report
7.3 Lower Animas and upper San Juan NMDGF post-release benthic
macroinvertebrate data
Lower Animas River and upper San Juan River locations sampled by the New Mexico Department of
Game and Fish are presented in Figure 3.2. The benthic macroinvertebrate samples were sorted by taxa
prior to metals analysis. The benthic macroinvertebrate taxa collected varied by location and sampling date
(August 2015 and March 2016, both post-GKM). Mayflies and caddisflies were the most frequently
collected taxonomic group (Table 7.4). True flies were only sampled at sufficient mass for analysis at the
San Juan location upstream of the confluence SJAR. Stoneflies were only sampled from ADW-010 and
SJFP. Only the August 2015 samples were analyzed for mercury and concentrations were generally less
than the reporting limit.
Analyzing the results by taxonomic group shows that metal bioaccumulation in benthic macroinvertebrates
is highly variable. Consistent trends in bioaccumulation between taxonomic groups were not observed. For
example, the greatest concentration of lead was measured in caddisflies. Mayflies and stoneflies
accumulated the greatest concentrations of cadmium and copper, respectively (Figures 7.5 and 7.6). At
sampling location ADW-022, cadmium concentrations in mayflies were approximately 6 times the
concentration measured in caddisflies. Similarly, copper concentration measured in stoneflies were
approximately 5 times the concentration measured in mayflies and caddisflies. Since the sampling did not
include replicates and metals in benthic invertebrate tissue can be highly variable within a site, it is not
clear if the differences observed between the taxa represent differences in bioaccumulation or the spatial
variability of metals, and hence exposure that could occur at a given sampling location.
Table 7.4. The total number and percent detection of samples that exceed the laboratory reporting limit of the
NMDGF benthic macroinvertebrate tissue metals data by taxonomic group. Mercury was only analyzed in the
August 2016 sampling event.
Metal
Mayflies
(Ephemerpotera)
Stoneflies
(Plecoptera)
Caddisflies
(Trichoptera)
True flies
(Diptera)
N
% detect
N
% detect
N
% detect
N
% detect
Aluminum
10
100%
3
67%
7
100%
2
100%
Arsenic
10
100%
3
67%
7
86%
2
100%
Cadmium
10
50%
3
67%
7
57%
2
50%
Copper
10
90%
3
67%
7
71%
2
100%
Lead
10
90%
3
67%
7
86%
2
100%
Manganese
10
100%
3
100%
7
100%
2
100%
Mercury
5
20%
2
0%
4
50%
1
100%
Selenium
10
50%
3
67%
7
57%
2
50%
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EPA Gold King Mine Biological Response Report
400
350
300
250
200
150
100
50
0
Aluminum: NMDGF — August 2015
I
1
ADW-022 ADW-010 LVW-020
SJFP
SJAR
Upstream
Animas River ] [
i Mayflies Caddisflies
San Juan River
400
350
*
5
300
£
Q.
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150
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50
0
Aluminum: NMDGF — March 2016
1
I I
ADW-022 ADW-010 LVW-020 SJFP
Animas River ] [ San Juan River
SJAR
Upstream
¦ Stoneflies - True flies
i Mayflies Caddisflies ¦ Stoneflies -True flies
0.4
0.3
o 0.2
2
C
n
£ 0.1
Arsenic: NMDGF — August 2015
S 0
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0.7
6
5
4
3
2
1
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I ll I
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Animas River ] [ San Juan River
i Mayflies Caddisflies ¦ Stoneflies = True flies
Cadmium: NMDGF —August 2015
SJAR
Upstream
1
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River ][ San Juan River
¦ Mayflies ©Caddisflies ¦ Stoneflies s True flies
0.4
0.3
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c
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EPA Gold King Mine Biological Response Report
_ 6
3
I ^
! 4
c
o
S 3
Copper: NMDGF--August 2015
1
I
1
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River ] [ San Juan River
m Mayflies Caddisflies ¦ Stoneflies s True flies
Copper: NMDGF -- March 2016
1
ADW-022 ADW-010 LVW-020
SJFP
SJAR
Upstream
Animas River
it
San Juan River
I Mayflies Caddisflies ¦ Stoneflies = True flies
Lead: NMDGF -- August 2015
ADW-022 ADW-010 LVW-020 SJFP
Animas River ][ San Juan River
¦ Mayflies Caddisflies ¦ Stoneflies ¦ True flies
SJAR
Upstream
I 3
E
.2 2
Lead: NMDGF -- March 2016
Li
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River ] [ San Juan River
¦ Mayflies Caddisflies ¦ Stoneflies -True flies
200
5 150
£
| 100
re
c
0
1 50
u
0
Manganese: NMDGF— August 2015
ADW-022 ADW-010 LVW-020 SJFP
Animas River J [ San Juan River
I Mayflies . Caddisflies ¦ Stoneflies s True flies
SJAR
Upstream
200
1150
o 100
50
Manganese: NMDGF — March 2015
1
1
ADW-022 ADW-010 LVW-020 SJFP
Animas River ][ San Juan River
¦ Mayflies Caddisflies ¦ Stoneflies = True flies
SJAR
Upstream
Figure 7.6 Concentration of copper, lead, and manganese measured in benthic macroinvertebrate tissue samples
collected by the NMDGF in the lower Animas and upper San Juan rivers in August 2015 and March 2016. The
August 2015 samples were collected after the GKM release when deposits were present (see Section 2.3.2, Figure
2.11).
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EPA Gold King Mine Biological Response Report
The mean metal concentration in benthic tissue measured by location and sampling date was used to assess
the spatial and temporal differences in the NMDGF data. When calculating the mean concentration,
qualified results that were less than the reporting limit were set to a method detection limit given the high
variability of reporting limits that were observed among the sampling locations and dates. No pre-release
data were available from these sampling locations for analysis. Additionally, mean concentration results
obtained by NMDGF are not directly comparable to EPA macroinvertebrate tissue results due to
methodology differences. NMDGF samples were sorted and analyzed by taxonomic group whereas EPA
samples were a composite of all taxonomic groups. To test for differences in the mean concentration of
metals in the weeks following the GKM release (August 2015) and the following spring (March 2016), a
non-parametric test was used that considers the sign and magnitude of the observed differences (Wilcoxon
Signed Rank test). Site SJAR, upstream of the Animas-San Juan confluence, was not included in our
analysis. Since the differences between each pair were evaluated across locations, the results of the test
assess for a statistical difference throughout the study area rather than by location.
Spatial patterns in the NMDGF dataset were consistent with the longitudinal patterns observed in the EPA
2016 benthic tissue dataset (see Chapter 7.4). For arsenic and aluminum, the mean concentrations were
relatively similar at all sampling locations and dates, with the greatest concentrations observed at the
upstream location SJAR (Figure 7.7). The greatest mean concentration of cadmium and lead were observed
in the August samples collected from the lower Animas River sites (ADW-022 and ADW-010). Cadmium
and lead concentrations decreased at these sites the following spring to what appears to be the background
condition determined by concentrations measured at SJAR. It is reasonable to interpret the high
concentration of these metals in the August benthic invertebrate samples as a response to the GKM
sediments that were deposited in this area for three weeks after the event, although the differences in the
August 2015 and March 2016 concentrations were not statistically significant (Figure 7.7; all p-values >
0.09). An alternative hypothesis is that differences in the mean concentrations reflected seasonal changes in
the taxonomic composition of benthic macroinvertebrate and life stages occurring at the sites. Samples
were not collected in the summer/fall of 2016 so seasonal changes in benthic macroinvertebrate tissue
concentrations cannot be determined.
Copper and manganese concentrations measured in the lower Animas (ADW-022 and ADW-010) and San
Juan at LVW-020 (immediately downstream of the confluence with the Animas River) were greater than
SJAR on both sampling dates. The mean concentration of metals at SJFP (17 km downstream of LVW-
020), on the other hand, were similar to or less than what is observed at SJAR. Locations with the greatest
metal concentrations also exhibited the greatest variability among the taxonomic groups collected from the
site.
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EPA Gold King Mine Biological Response Report
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0.5
0.0
Arsenic: Benthic Macroinvertebrates
NMDGF
~ Aug-15 Mar-16
p = 0.625
ADW-022 ADW-010 LVW-020
Animas River ] [ San Juan River
SJFP SJAR
Upstream
Cadmium: Benthic Macroinvertebrates
NMDGF
0.8
0.7
_ 0.6
5
5
E 0.5
Q.
a.
| 0.4
g 0.3
o
° 0.2
0.1
0.0
~ Aug-15 Mar-16
p = 0.097
n ~ eh_
ADW-022 ADW-010 LVW-020
Animas River ] [ San Juan River
SJFP SJAR
Upstream
Lead: Benthic Macroinvertebrates
NMDGF
~ Aug-15 Mar-16
p =0.625
i
r
¦ i rf
j
J:;
p
\
ADW-022 ADW-010 LVW-020 SJFP SJAR
Animas River ] [ San Juan River ^ PStrea m
400
350
300
3
F
250
Q.
c
o
200
nj
c
150
o
u
100
50
0
Aluminum: Benthic Macroinvertebrates
NMDGF
~ Aug-15 Mar-16
p = 0.625
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River
San Juan River
Copper: Benthic Macroinvertebrates
NMDGF
~ Aug-15 Mar-16
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River
San Juan River
Manganese: Benthic Macroinvertebrates
NMDGF
~ Aug-15 Mar-16
p = 0.875
ADW-022 ADW-010 LVW-020 SJFP SJAR
Upstream
Animas River
San Juan River
Figure 7.7. The mean concentration of metals ± 1SD jppm ww) in ail benthic macroinvertebrate taxonomic
groups by location in August 2015 and March 2016. N varied by sampling location and date and ranged from
1-3. Both sampling dates represent post-GKM release conditions. Error bars represent 1 standard deviation
and the variability of metals among taxonomic groups at that location. The p-values are the results of
Wilcoxon signed rank test to compare concentrations by sample date.
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EPA Gold King Mine Biological Response Report
7.4 Summary of metals in benthic macroinvertebrates tissue
The accumulation of metals in benthic macroinvertebrates collected from the Animas and San Juan rivers
following the GKM release was spatially and temporally variable. Samples collected from the upper
Animas after the GKM release that represent near-term sampling (September 2015) had greater copper and
lower manganese concentrations when compared to pre-release concentrations. All other changes in metal
concentrations from 2014 were not statistically significant and were within the range of potential sample
variability. The lack of a consistent response by metal sheds light on the complexity of metal
bioaccumulation in benthic organisms.
In the lower Animas and upper San Juan rivers, historic concentrations were not available for a pre- and
post-GKM release analysis. Concentrations of cadmium and lead measured in the near-term samples
(August 2015) were elevated at the lower Animas site ADW-022 when compared to the following spring
(March 2016). Benthic tissue samples collected from ADW-022 also generally had greater metal
concentrations than the immediate up and downstream locations in the fall 2016. Many metals were
elevated in the fall 2016 samples when compared to the pre-release (2014) and the near-term post-release
(2015) concentrations. The 2016 samples were similar to concentrations observed in 2012. These high
concentrations were also observed in the upstream and tributary samples after the GKM deposits were
flushed through the river system during the spring snow melt in 2016 (EPA 2016c), suggesting something
other than the GKM release contributed to the high concentrations. Differences in field collection methods,
analytical methods and the benthic community composition likely contributed to the differences observed
between years (e.g., estimating percent solids vs. measuring percent solids, the removal of caddisflies from
their casings prior to analysis).
High intra- and inter-site variability and longitudinal patterns in the recent benthic macroinvertebrate tissue
data are consistent with the results presented by Besser el al. (2001). The authors characterized
concentrations of cadmium, copper, lead and zinc in specific macroinvertebrate taxa (Rhithrogena, mayfly;
Arctopsyche, caddisfly; Megarcys, stonefly; Zapada, stonefly) collected from the upper Animas and
tributaries in 1996. The Besser study showed significantly different metal concentrations in benthic
macroinvertebrates among taxa and among sampling locations. Metal concentration trends observed in their
data were partly explained by organism size and differences in feeding groups, with smaller taxa generally
accumulating more metals. Concentration differences between sampling location in the Besser study were
limited by the presence and/or absence of specific taxa at a given sampling location. Longitudinal changes
in the benthic macroinvertebrate community also confounded the post-release GKM benthic tissue data and
limited the inferences we could make from the analyses.
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EPA Gold King Mine Biological Response Report
CHAPTER 8 METALS IN FISH TISSUE
Numerous factors determine the likely uptake of metals in individual fish, including species, size of fish,
and the environmental conditions in which they live. Fish rapidly take-in metals through their gills or food
and expel them rapidly (on the order of hours to days), thus the internal body burden reflected in tissue
concentrations should reflect the ambient water or feeding (sediment) environmental concentrations close
to the time they are sampled. Chapter 8 explores the bioaccumulation of metals in individual fish and
populations, by location and time with respect to the passing of the GKM plume, the presence of GKM
deposits, and pre-release tissue concentrations. These analyses address questions relating to long-term
changes in biological communities observed a year after the GKM release. Pre-GKM release fish tissue
data were limited to a single sampling event on the Animas River by Southern Ute Indian Tribe, therefore
analyses primarily focus on the characteristics and differences in the post-release tissue concentrations. We
also summarize the state and tribal findings with respect to human health risk associated with consumption
of fish post-GKM.
Our analyses showed that some fish accumulated metals in the weeks after the GKM event in the lower
Animas River that received GKM metals deposits. Metals were significantly elevated in bluehead and
flannelmouth sucker liver and speckled dace muscle tissue. The degree of metal accumulation in liver
differed by species, sampling location, and among the metals, with aluminum, cadmium, lead and
manganese exhibiting the greatest concentrations. For the most part, elevated liver concentration did not
translate to high muscle concentrations. Metal concentrations in fish declined to background conditions
when samples were collected again the following spring and never triggered human health consumption
advisories.
8.1 Fish tissue data
Metals in fish tissue data collected prior to and after the GKM release were assembled to characterize the
body burden of metals in fish in the Animas and San Juan rivers affected by ongoing acid mine drainage in
the headwaters mining district and the GKM release. This analysis used pre-GKM fish tissue data collected
by the Southern Ute Indian Tribe (SUIT) and post-GKM event data collected by the New Mexico
Department of Game and Fish (NMDGF), the Colorado Department of Public Health and Environment
(CDPHE), Navajo Nation EPA (NNEPA) and the EPA. Differences in sampling methods limited the data
that could be combined for pre-and post-GKM event comparisons. See Chapter 3 for additional details
about pre- and post-GKM event fish sampling and analytical methods.
CDPHE and NMDGF collected fish tissue samples when the maximum effect of the GKM release was
observed (August 2015) and the following spring (March 2016). These datasets were used to assess the
short-term effect of the GKM deposits left as the plume migrated through the river system. The presence of
deposits and relative change in metal concentration (i.e., change from background) varied with sampling
date and river location. CDPHE's sampling focused on trout muscle samples in the Durango area. The
NMDGF sampled metal concentrations in fish muscle and livers in several species the lower Animas and
upper San Juan Rivers.
SUIT sampled fish in July 2015, prior to the GKM event. These data were compared to EPA, CDPHE and
NMDGF post event data collected near the same locations to assess whether tissue concentrations observed
at various times after the 2016 snowmelt period were similar to pre-event levels.
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EPA Gold King Mine Biological Response Report
8.2 Analysis of NMDGF post-GKM release fish tissue data
The most robust data available to directly assess the effects of the GKM release were collected in the New
Mexico portion of the Animas and San Juan rivers after the GKM release by the New Mexico Department
of Game and Fish (NMDGF).
8.2.1 About NMDGF fish data
NMDGF collected fish tissue samples for metal analyses twice after the GKM release at 2 locations in the
lower Animas River and at 3 locations in the upper San Juan River. (See Figure 3.2 for site locations.)
Approximately 60 km of river length within New Mexico is bracketed between the upper and lowermost
sampling locations near the Colorado/New Mexico border, including 40 km of the lower Animas from
Cedar Hill to the confluence with the San Juan River in Farmington and 20 km of the San Juan River near
Farmington. A reference site was sampled on the San Juan River above the confluence with the Animas.
NMDGF conducted the first sampling in the weeks following the GKM release in August and a second in
March 2016 prior to snowmelt runoff. The NMDFG sampling design provided a meaningful statistical
comparison of metal bioaccumulation in four species of fish when the maximum effect of the GKM release
was observed relative to background environmental concentrations of metals.
Table 8.1 summarizes the general status of metals in sediment and water in the Animas and San Juan rivers
during the two fish sampling events. During the August 2015 fish sampling, GKM sediment deposits were
present in significant amounts in the lower Animas, declined in the downstream direction, and were
negligible in the San Juan River. Sediment concentrations in the lower Animas returned to background
after the monsoonal storm at all locations and were low when fish tissue was sampled in March 2016.
Metal concentrations in the water were elevated in both segments of the river in the post-event period
(August 2015) and were at low background levels in both segments during the March 2016 sampling
(Chapter 2).
Table 8.1. Summary of general metals effects from the GKM release in the Animas and San Juan rivers during fish
sampling in August 2015 (post-release) and March 2016. March 2016 sample were used to estimate background
condition given the limited pre-release data tissue data from these sampling locations.
Sampling Date
Lower Animas
San Juan River
(2 locations)
(2 locations)
August 2015
• Significant GKM deposits in sediments
• Little, if any, GKM deposits
• Elevated water concentrations
• Elevated water concentrations
March 2016
• No GKM deposits in sediments
• No GKM deposits in sediments
• Low water concentrations
• Low water concentrations
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EPA Gold King Mine Biological Response Report
Characteristics of the Fish Community
Multiple species were present through the
60-km length of rivers, although not all
species were sampled at all sites. Up to 10
individuals from each species were
collected for analysis of metal
concentrations in their tissue (Table 8.2).
Skinless filets (muscle) and liver samples
were collected from bluehead sucker,
flannelmouth sucker, rainbow trout, brown
trout and channel catfish. Speckled dace
muscle samples represented a composite of
5 fish with the head and gut content
removed, and therefore include skin, scales
and fins. All tissue samples were
processed for 6 metals (Al, As, Cd, Cu,
Hg, Pb, Mn, Se, and Zn). Table 6.2
provides the count of sampled fish by
species at each site during each of the two
sampling events. Brown trout, bluehead
sucker, flannelmouth sucker, and speckled
dace were sampled from all 5 sampling
locations in both rivers. Rainbow trout
Sampled Fish Length-August 2015
600
500
~ 400
E.
.c
m 300
200
100
T
T
8
T
D Bluehead Sucker ~ Flannelmouth Sucker I Trout G Speckled Dace
Figure 8.1. Body size distribution of fish by species sampled at
all sites in August 2015. Boxplots show mean, median, and
quartiles.
were sampled the Animas River, and channel catfish were found in the San Juan River. The range of fish
size expressed as body length for each species grouping all sites is shown in Figure 8.1. Given the limited
number of sites where catfish were sampled, limited results are presented for this species.
Multiple factors contribute to the accumulation of metals in body tissue, including the specific
environmental concentrations at sampling locations, fish characteristics such as species and individual fish
size, and the type of tissue sampled. The individual factors are explored graphically in Figures 8.2 through
8.9 to develop a general understanding of the accumulation of metals in fish following the GKM release. A
general linear modeling (GLM) approach was applied to statistically evaluate the NDDFG dataset. Results
of the GLM are presented in Appendix E.
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EPA Gold King Mine Biological Response Report
Table 8.2. Count of fish by location, sampling event, tissue type and species during fish tissue sampling conducted
by the NMDGF after the GKM release (August 2015) and in March 2016. Livers were collected from the same fish
as muscle tissue and were not collected from speckled dace. If a species or tissue was not sampled at a location,
the count is indicated as **speckled dace muscle samples represent a composite of 5 fish with the head and gut
content removed.
Location
ADW-022
ADW-010
LVW-020
SJFP
SJAR
Total
River
Lower Animas
Lower
Animas
San Juan
San Juan
San Juan
Distance from GKM (RKM)
147
163
196
214
Upstream
Liver
53
35
41
44
27
200
August 2015
19
9
20
15
Not
Sampled
63
Bluehead sucker
10
8
9
0
--
27
Flannelmouth sucker
0
0
10
10
--
20
White sucker
0
1
-
0
-
1
Brown trout
7
0
1
0
--
8
Rainbow trout
2
0
0
0
-
2
Channel catfish
-
--
-
5
-
5
March 2016
34
26
21
29
27
137
Bluehead sucker
11
9
10
5
7
42
Flannelmouth sucker
10
10
10
10
9
49
White sucker
1
0
--
1
-
2
Brown trout
10
2
1
5
10
28
Rainbow trout
2
5
0
0
1
8
Channel catfish
-
--
-
8
-
8
Muscle (filet without skin)
74
56
61
62
63
316
August 2015
30
20
30
25
25
130
Bluehead sucker
10
8
9
0
5
32
Flannelmouth sucker
0
0
10
10
10
30
White sucker
0
1
-
0
-
1
Brown trout
8
0
1
0
0
9
Rainbow trout
2
1
0
0
0
3
Speckled dace**
10
10
10
10
10
50
Channel catfish
-
--
-
5
-
5
March 2016
44
36
31
37
38
186
Bluehead sucker
11
9
10
5
7
42
Flannelmouth sucker
10
10
10
10
10
50
White sucker
1
0
--
1
-
2
Brown trout
10
2
1
5
10
28
Rainbow trout
2
5
0
0
1
8
Speckled dace**
10
10
10
8
10
48
Channel catfish
—
—
—
8
—
8
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EPA Gold King Mine Biological Response Report
8.2.2 Individual fish, population and tissue-specific responses
The general bioaccumulation of metals in individual fish is illustrated for liver tissue in Figure 8.2 and
muscle tissue in Figure 8.3. The liver sequesters and regulates metals in fish and is an indicator of
exposure. Liver concentrations do not translate directly to muscle concentrations. Metal concentrations are
shown for individual fish, identified by species and plotted by body length grouping all sites and both
sampling events. These figures highlight several key characteristics of how metal bioaccumulation can vary
within a fish community and the complexity of the response.
Only some individuals within each species accumulated metals. Many liver and most muscle samples were
less than detection limits, indicated by the flat line that represents the non-detection limit of the laboratory
test for each metal. The effect of sample time will be assessed later in this section, but most of the high
tissue concentrations were observed in the August 2015 samples.
Metal concentrations in livers were generally greater than those in muscle, consistent with the scientific
literature that identifies sequestration of metals in liver tissue. Muscle samples with detected concentrations
were an order of magnitude lower than those in the liver (Figures 8.2 and 8.3). Concentrations in the liver
of some individuals were more than three orders of magnitude greater than the average of the population.
Bioaccumulation varied by species and metal. Most species and many individuals had detectable
concentrations of copper and manganese in liver tissue, while species reacted differently to the other metals
(Figure 8.2). Bluehead suckers had detectable liver concentrations for most of the six metals, while trout
and flannelmouth sucker livers primarily accumulated copper, lead, manganese and cadmium. Only the
muscle tissue of speckled dace was tested (Figure 8.3). More individuals in the speckled dace population
had high metal concentrations in muscle compared to other species.
Selenium and mercury concentrations in muscle and liver are shown in Figure 8.4. Unlike other metals,
concentrations of mercury in muscle were similar to or greater than in the liver. As with other metals,
speckled dace accumulated greater mercury and selenium concentrations in muscle than other species while
trout livers had greater selenium concentrations than other species.
Fish size played a small role in metal bioaccumulation within the species groups. There was a slight
positive trend in copper concentrations in trout liver with fish size. For the most part, however, the smaller
fish in each population tended to have higher concentrations than the larger fish. While species vary
physiologically in how they take up metals, this pattern could also result from the habitat niche that
individuals occupied. Gold King Mine release deposits varied laterally across the channel as well as
longitudinally along the rivers. Metal concentrations left by the GKM release were probably greater along
the channel edges than in the main current.
There was clear accumulation of metals in liver and to a lesser extent muscle in some individuals within the
population of fish, although there was high variability between species, metals, tissue type, and among
individuals within the population.
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EPA Gold King Mine Biological Response Report
Liver Tissue --Copper
O Blue head Sucker • Flannelmouth sucker A Brown Trout
¦5J10,000.0
i 1,000.0
£
O
'f 100.0
10.0
1.0
0.1
A
A
A A ^3
A AA
V
G» CE0EKBDO OCMXDDO
s
200 400
Fish Length (mm)
600
Liver Tissue --Lead
€ Bluehead Sucker • Flannelmouth sucker a Brown Trout
_100.00
10.00
c
o
h
c
1.00
^ 0.10
3
.£
*" 0.01
.O ©
• • •«
* • •• 4
200 400
Fish Length (mm)
600
Liver Tissue -Aluminum
© Bluehead Sucker • Flannelmouth sucker ABrownTrout
10,000
1,000
100
200 400
Fish Length (mm)
600
Liver Tissue -Arsenic
O Bluehead Sucker • Flannelmouth sucker ABrownTrout
200 400
Fish Length (mm)
600
Liver Tissue -Manganese
Bluehead Sucker • Flannelmouth sucker ABrownTrout
1,000.0
©
o%
©
©
100.0
©
o%
® ©
§
V
©
5 10.0
c
a»
o
8
A
•
-4
* • A
V
1
Ti
o
~—1
¦ ¦ ' ' i—g.frA- ¦ ,
.¦¦¦¦• 1# ... 1 ... »
100
200 300 400
Fish Length (mm)
500
600
OBluehead Sucker
1,000.00
Liver Tissue -Cadmium
Flannelmouth sucker A Brown Trout
o 10.00
200 400
Fish Length (mm)
600
Figure 8.2. Liver tissue concentration of copper, lead, aluminum, arsenic, manganese and cadmium (mg/kg
ww) in individual fish identified by species. Data collected at all sites in the two sampling events are grouped
in these figures.
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EPA Gold King Mine Biological Response Report
Muscle Tissue -Copper
G Bluehead Sucker
• Flannelmouth sucker
A Brown Trout
¦ Speckled Dace
100 200 300 400
Fish Length (mm)
1—i—i
500
600
0.8
"So
0.7
00
E
0.6
c
_o
0.5
%
0.4
c
QJ
u
0.3
O
u
0.2
QJ
3
CO
l/l
0.1
1=
Muscle Tissue --Lead
® Bluehead Sucker
• Flannelmouth sucker
~ Brown Trout
¦ Speckled Dace
100 200 300 400
Fish Length (mm)
500
600
Muscle Tissue --Aluminum
OBluehead Sucker
•
1
• Flannelmouth sucker
"S3
a Brown Trout
0.8
) Speckled Dace
E_
o 0.6
O
en
o
u
o
~
0
v 0.2
©
©
M
D ^ A
~—
H 1 t 1 1 T 1 t r t | i i i i
200 400
Fish Length (mm)
600
Muscle Tissue --Arsenic
8> Bluehead Sucker
• Flannelmouth sucker
A Brown Trout
~ Speckled Dace
100 200 300 400 500 600
Fish Length (mm)
Muscle Tissue --Manganese
Muscle Tissue --Cadmium
18
16
14
12
10
8
6
4
2
0
©Bluehead Sucker
• Flannelmouth sucker
~ Brown Trout
SI Speckled Dace
:
4
-------
EPA Gold King Mine Biological Response Report
O Bluehead Sucker
0.30
Liver Tissue -Mercury
Flannelmouth sucker A Brown Trout
0.15
0.05
~-m
200 300 400
Fish Length (mm)
Muscle Tissue -Mercury
0.3
0.25
0.2
0.15
0.1
0.05
0
O Bluehead Sucker
n
• Flannelmouth sucker
~
A Brown Trout
•
~
( Speckled Dace
*BD
•
. i
y:
• o<*
- *•>
A
~ . O, ET)«» ~ , ,
100
200 300 400
Fish Length (mm)
500
600
• Bluehead Sucker
100.0
Liver Tissue --Selenium
Flannelmouth sucker A Brown Trout
S
100 200 300 400
Fish Length (mm)
500
600
3
2.5
2
1.5
1
0.5
0
Muscle Tissue --Selenium
• Bluehead Sucker
• Flannelmouth sucker
A Brown Trout
¦ Speckled Dace
. 5
,v:
im 4A ao
A • • • ' -
c*» o'%°V v
100
200 300 400
Fish Length (mm)
500
600
Figure 8.4. Tissue concentrations of mercury and selenium (mg/kg ww) in liver and muscle samples of
individual fish identified by species. Data collected at all sites in the two sampling events are grouped.
A two-sample t-test was used to statistically compare the species-specific mean metal concentration in liver
and muscle by sampling date. Results showed that bluehead sucker liver tissue had statically greater
aluminum, lead, manganese and selenium concentrations in August when compared to the mean
concentration the following March (; p<0.0;5 Table 8.3). Statically significant differences were also
observed in the mean cadmium and lead concentrations measured in flannelmouth sucker liver tissue. Trout
liver concentrations, on the other hand, did not differ between sampling dates. Differences in the mean
concentration of metals in muscle in August and March were not generally significant for trout, bluehead
sucker and flannelmouth sucker, the exception being selenium. Mean cadmium, lead and selenium in
speckled dace muscle were significantly greater in August when compared to March. These results suggest
that many suckers and dace responded to the increased exposure and accumulated metals associated with
the GKM-deposits in the lower Animas and upper San Juan rivers; however, given the seasonal differences
in the sampling dates, it is challenging to identify how much of the difference in concentration was due to
the presence of the GKM deposits verses the expected seasonal variability in metal bioaccumulation that
has been shown to be temperature dependent. When compared to water temperatures in March, the greater
temperatures in August would be expected to increase fish metabolic rates, thus promote increased metal
uptake.
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EPA Gold King Mine Biological Response Report
Table 8.3. Mean metal concentration measured in liver and muscle tissue samples collected by NMDGF in
August 2016 and March 2017. Highlighted cells identify statistically significant differences in the species mean
concentration by sampling date (p<0.05).
Trout
Bluehead sucker
Flannelmouth sucker
Speckled dace
August
March
August
March
August
March
August
March
LIVER
Aluminum
5
5
438.30
18.91
6.55
5.00
No Data
Arsenic
0.05
0.05
0.53
0.35
0.05
0.08
Cadmium
0.12
0.10
3.47
0.02
47.41
0.02
Copper
169.63
211.19
2.55
3.15
16.43
14.12
Lead
0.04
0.03
3.58
0.05
0.29
0.06
Manganese
1.10
1.45
90.70
13.87
3.93
3.28
Selenium
18.33
15.44
0.86
0.43
1.457
1.390
MUSCLE
Aluminum
5.00
5.00
8.54
5.74
11.25
5.00
5.18
7.18
Arsenic
0.05
0.05
0.07
0.07
0.05
0.05
0.40
0.35
Cadmium
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.01
Copper
0.56
0.80
0.50
0.50
0.50
0.50
0.51
0.54
Lead
0.03
0.03
0.03
0.03
0.04
0.03
0.05
0.03
Manganese
0.94
0.46
1.62
0.86
0.26
0.37
5.42
4.39
Selenium
0.58
0.10
0.30
0.10
0.58
0.31 | 1.10 | 0.79
8.2.3 Multiple metals in fish tissue considerations
Did some individuals or species accumulate significant amounts of multiple metals? To evaluate multi-
metal accumulation, we summed the concentrations of 7 metals in each fish (Al, As, Cd, Cu, Mn, Pb, and
Se). Because the metals have large differences in concentration within the body, we first converted the
concentration by logio, and then normalized the distribution for each metal within the population using the
z-score formula:
z= (x-m/SD)
Where z is the scaled value of the observation x, m is the mean of x, and SD is the standard deviation of x.
The scaling put each metal on the same relative scale and gave it equal weight when the metals were
summed. This formulation centers the distribution mean at zero.
The summed metal values in liver and muscle for each species, combining both sampling periods, are
shown in Figure 8.5.A and B, respectively. The summed metal values in liver and muscle in the two
sampling periods, combining all species, are shown in Figure 8.5.C and D, respectively. Given the
normalization, each of the tissue groups had a minimum value of -4 to -6 when all seven metals were at
non-detect levels. Copper and manganese are generally detected in tissue, as they are regulated by the body,
and therefore the minimum values are not generally observed. The summed metal values spanned from a
minimum of -6 to values greater than 15 in each tissue type for a few individuals. We identified individuals
with high overall metal body burden as those with a value greater than +1 standard deviation of the mean
(liver> 3.76 and muscle > 3.497). Three or more metals had to be present in relatively high concentrations
in the individual to reach this value.
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EPA Gold King Mine Biological Response Report
Of 151 liver samples, 18 individual fish had high overall metal body burden. Flannelmouth (n=7) and
bluehead suckers (n=10) made up most of this group. It also included 1 trout. Most high values were
observed in August (89%) as opposed to March. The individual fish with high liver body burdens were
somewhat more likely to occur in the San Juan River (61%) than the Animas (39%). The majority of those
in the San Juan River were taken in Farmington at LVW020.
A)
OJ
5
20
15
10
-5
-10
Liver
B)
10
Muscle
t
.
I Trout n Bluehead sucker IH Flannelmouth sucker ¦ Speckled dace
I Trout ¦ Bluehead sucker ¦ Flannelmouth sucker
C)
25
20
15
10
t/i
o 0
E
3
<
T
i 1
1
1 1
1
e
25
JH 20
01
5
15
~ 10
O U
E
3
1/1 .5
-10 J
Muscle
~ Aug-15 ~ Mar-16
~ Aug-15 ~ Mar-16
Figure 8.5. Comparison of the cumulative metal values in A) liver by species, B) muscle by species, C) liver by
sampling date and D) muscle by sampling date. The concentration of each metal was transformed to logio and
standardized to the mean and standard deviation of the population prior summing.
98
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EPA Gold King Mine Biological Response Report
Of 268 muscle samples, 32 fish had significant concentrations of multiple metals. Most of these fish (78%)
were speckled dace (Figure 8.5.B). This was also apparent in the individual metal concentrations in Figures
8.3 and 8.4. Five bluehead suckers and 1 each of flannelmouth sucker and trout were also in this group.
Nearly half (16 fish) of the high summed values s in muscle occurred in the San Juan River, where they
were evenly distributed between the 3 sampling locations This included the reference reach located
upstream of the Animas, and were almost as likely to occur in March as in August. The other half (17 fish)
of the high summed values were observed in the Animas River, with the majority sampled in August
(88%).
The analysis of summed metals suggests that speckled dace accumulated relatively more metals in muscle
when compared to other species. Only a few individual trout, bluehead suckers and flannelmouth suckers
accumulated multiple metals at high concentrations in either liver or muscle tissue. High cumulative metal
burden was observed in some individuals in March, but generally it was greater in the August when metal
concentrations in sediment were greater than background.
8.2.4 Sampling location trends
The range of tissue metal concentrations observed at the individual sites varied, especially in August 2015.
Figures 8.6 and 8.7 show the average metal concentrations in liver and muscle tissue by site, grouping all
fish species. There was a longitudinal gradient in tissue concentrations of many of the metals during the
August sampling after the GKM release that generally corresponded to the increase in sediment metals
documented in the lower Animas River.
Livers had much higher average concentrations of lead, aluminum, arsenic, copper, and manganese in
August at the two Animas River locations than at the two San Juan River sites. Muscle samples also tended
to have a gradient from upstream to downstream in August, but differences in concentrations among sites
were much smaller. Lead was elevated at all locations in the August sampling, with the highest levels
observed at the San Juan River reference site. Lead in muscle tissue was low at all sites in March.
In the San Juan, August 2015 fish muscle samples collected from the San Juan sites had metal
concentrations that were generally similar to the March 2016 levels. Several metals, including selenium,
arsenic and manganese were also higher during August at the San Juan upstream site than other San Juan
sites. Tissue concentrations were significantly reduced at the Animas River sites in March relative to
August and were similar to the San Juan River sites.
These patterns suggest that fish tissue concentrations were generally elevated in response to the high
sediment concentrations in the Animas River that persisted for approximately 3 weeks after the GKM
release (see Chapter 2; Figure 2.11). Bioaccumulation of metals in fish collected from the San Juan River
was low, consistent with the low August sediment concentrations. Sediments returned to background
sediment conditions in the Animas and San Juan River after August 27, 2015, due to a monsoonal storm
that removed the deposited material (EPA 2016c). Tissue concentrations at all Animas and San Juan sites
were at background conditions in March 2016.
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EPA Gold King Mine Biological Response Report
Lead-Liver
Lead-Muscle
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
August
2015
March 2016
3.6
3.9
n 7 02
0.01 0.03 °;1 0.03
1 !¦ 1 l'l 1 11 1
148 162 196 214 148 162 196 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Aluminum-Liver
1000
900
800
700
600
500
400
300
200
100
0
August
March 2016
2015
5.1
242.6
890.8
6.1
2.5 2.5 25.5 3.0
148 162 196 214 148 162 196 214
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
March 2016
August
2015
v* -v* /¦ V* # V* f
IP
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Aluminum-Muscle
2
ao
E
August
2015
March 2016
f J /• S f /¦
A* if
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Arsenic—Liver
Arsenic—Muscle
0.9
.5?
0.8
0.7
fc
0.6
O
2
0.5
c
0)
0.4
c
o
o
0.3
a;
.13
0.2
0.1
0.0
0.36 0.77
August
2015
0.05 °-03
March 2016
0.07
0.12
llll
0.27
0.17
148 162 196 214 148 162 196 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
August
2015
March 2016
$1$
/
*
9? 9?
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Figure 8.6. Mean concentration of lead, aluminum, and arsenic in liver and muscle (mg/kg ww) of all fish
sampled at each location in each sampling period. Sites are organized by distance from GKM from left to right
with lower Animas sites identified by solid bars and San Juan sites identified by textured bars. Muscle
concentrations at the reference site on the San Juan River are shown as the darkest bar. Liver samples collected
at this location in March are not presented.
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EPA Gold King Mine Biological Response Report
Manganese-Liver
Manganese-Muscle
140
CU3
120
**«s
&Q
E
100
c
o
I
80
c
8
60
c
O
u
40
-3
20
0
74.15 124.78
August
2015
3.75
March 2016
3.35
2.82
148 162 196 214 148 162 196 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Copper—Liver
90
80
70
b
c
o
60
2
50
c
K
40
c
u
30
01
H
20
10
0
71.64
August
2015
March 2016
81.04 20.29
11.18
$gg|
3486
148 162 1% 214 148 162 196 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Selenium-Liver
00
E
c
o
2
10
9
8
7
6
5
4
3
2
1
0
August 2015
8.1
March 2016
5.6
1.3
1.4
3.5
148 162 196 214 148 162 196 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
i?
M
JE
c
o
Q
August
2015
March 2016
, , ,
¦v* ^ V* -V* /• f N* V ,
& I*
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Copper-Muscle
March 2016
^ 0 35
0 0.25
2
c 0.20
s
8 015
01
3 o.io
Ml
P
0.05
0.00
August
2015
V* f f ^ -v* •v>* /
~ ~
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Selenium-Muscle
1.0-
0.9 :
3
0.8
oo
0.7
c
1
0.6
2
c
0.5
o
c
3
0.4
3
0.3
i—
0.2 :
0.1
0.0
August
2015
March 2016
WM
0.3,
¦f v*
f
a#
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Figure 8.7. Mean concentration of manganese, copper, and selenium in liver and muscle (mg/kg ww) of all fish
sampled at each location in each sampling period. Sites are organized by distance from GGKM from left to right
with lower Animas sites identified by solid bars and San Juan sites identified by textured bars. Muscle
concentrations at the reference site on the San Juan River are shown as the darkest bar. Liver samples collected
at this location in March are not presented.
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EPA Gold King Mine Biological Response Report
80.0
8?
70.0
00
E
60.0
c
o
50.0
2
40.0
C
u
30.0
O
U
i-
20.0
o;
>
—i
10.0
0.0
Cadmium-Liver
70.60
I
Cadmium—Muscle
August 2015
41.95
0.17 0.14
March 2016
o.io o.oi o.oi o.oi
148 162 1% 214 148 162 1% 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Mercury-Liver
0.045
— 0.040
"m 0.035
_£
c 0.030
o
2 0.025
¦M
8 0.020
c
3 0.015
k.
0)
» 0.010
0.005
0.000
August
2015
0.003 0003
March 2016
No Data
148 162 1% 214 148 162 1% 214
Lowr Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
0.018
0.016
0.014
0.012
0.010
0.008
0.006 j
0.004 ]
0.002
0.000 -
August
2015
March 2016
Lower Animas San Juan Lower Animas San Juan
Site Distance from GKM (km)
Mercury-Muscle
March 2016
August
2015
o.o
esse
0.02 0.03 o.os a06
0.02 0.01
Son Juan
Lower Animas San Juan Lower Animas
Site Distance from GKM (km)
Figure 8.8. Mean concentration of selenium and mercury in liver and muscle (mg/kg ww) of all fish sampled at
each location in each sampling period. Sites are organized by distance from GKM from left to right with lower
Animas sites identified by solid bars and San Juan sites identified by textured bars. Muscle concentrations at
the reference site on the San Juan River are shown as the darkest bar. Liver samples or mercury samples
collected at this location in March are not presented
There were exceptions to the general patterns observed for many of the metals in that some tissue metals
were higher in the San Juan River than the Animas River. Notably, aluminum in muscle tissue, was highest
in the San Juan River at 196 RKM (Figure 8.6). Cadmium in liver tissue was much greater in the San Juan
River than the Animas River in August. Copper concentrations in liver and sediment followed a
longitudinal pattern through the river segments in both the August 2015 and March 2016 samplings and
were similar in both periods suggesting copper is more persistent in fish tissue that the other metals. Lead
was much higher at the reference site in the August 2015 sampling than any site directly impacted by the
GKM release (Figure 8.6).
Mercury and selenium concentrations tended to be greater in the San Juan River than the Animas River in
both sampling events and concentrations were comparable to the San Juan River reference site (Figures 8.7
and 8.8). Similar to cadmium liver concentrations, the greatest mercury in liver concentrations were
measured in flannelmouth suckers that were not sampled from the lower Animas (Figure 8.4).
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EPA Gold King Mine Biological Response Report
We note that spatial and temporal differences and trends observed in the NMDGF data were influenced by
differences in the species that were sampled during each event (Table 8.2), and expected seasonal changes
in fish use and bioaccumulation rates. For example, flannelmouth suckers were not sampled at either of the
Animas River sites during August 2015. This partly explains differences between sampling locations in
August 2015 (e.g. high Cd in liver in the San Juan River) since the greatest cadmium concentrations were
observed in the larger flannelmouth sucker and one bluehead sucker (> 380 mm; Figure 8.2). Brown trout
were not sampled at ADW-010 (163 RKM) during August although they were found there in low numbers
in March. It is not clear whether the GKM release may have played a role in the presence or absence of
species, however no clear changes in fish populations in response to the GKM release were observed
(Chapter 6).
To illustrate the complexity of the relationship between the body burden of metals in the fish community in
response to environmental conditions, the tissue concentration of brook trout grouped with rainbow trout
and bluenose sucker grouped with flannelmouth sucker are shown in relation to the range of sediment
concentration observed in the August and March samplings at all sites in Figure 8.9. Manganese and copper
are internally regulated metals required for life functions. These metals would be expected to be
accumulated by fish and should tend to reach a saturation point. Lead is not a regulated metal and its
concentration in the body is likely to reflect exposure through diet.
The concentration of manganese in tissue showed increasing trends with sediment concentrations especially
in the liver. However, sucker species accumulated greater concentrations of manganese than the brown and
rainbow trout. The greatest body burden of copper was observed in the brown and rainbow trout and
reached relatively high levels even at relatively low sediment concentrations. Trout did not accumulate
much lead but suckers appeared to accumulate larger amounts when sediment concentrations exceeded 50
mg/kg. Although there was some influence of environmental metal concentrations on fish body burden,
these complexities preclude any broad generalizations about fish response to the levels of metals observed
at the lower Animas and San Juan rivers after the GKM release.
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EPA Gold King Mine Biological Response Report
Manganese, Sediment Concentration
Manganese, Sediment Concentration
Manganese— Brown Trout, Rainbow Trout
• Muscle A Liver
Liver = 0.0017x + 0
R* = 0.55
202
A A
A A
A
A •
/Uiscle = 0.0007x +0.111
• R<-0.24
•
A
€"
AfW •
*
200 400 600 800
Sediment Concentration (mg/kg)
100.0 :
Manganese-- Sucker spp
C Muscle A Liver
AUve'
= 0.1421x-24.083
R' = 0.40
A
A
A
fi
&
&A
A
•
A
A
•
•
f
• ..
£
JR. f
•
Musde=0.
R'
•
D022x +0.057
0.35
0 100 200 300 400 500 600 700 800 900
Sediment Concentration (mg/kg)
Lead, Sediment Concentration
Lead, Sediment Concentration
Lead-- Brook Trout, Rainbow Trout
• Muscle A Liver
Liver = 0
0007x +0.0395
Muscle = 0.0129x+0.3497
-
R*
= 0.09
Sediment Concentration (mg/kg)
Copper, Water Concentration
Copper- Brown Trout, Rainbow Trout
• Musde A Liver
<
ao
E,
§
A
Live
r = 6.8679x +80.78
4
LVW020 (Aug)
A
L
A
A
A "
Musde=0.0122x +0.4941
»,R'=001 m
Lead- Sucker spp
• Musde A Liver
A
Liver
= 0.066x
R' = 0.5
0.5572
A
Musde =
0.0001X+-0.0142
' = 0.12
•
-•—
20 30 40 SO 60
Sediment Concentration (mg/kg)
Copper, Water Concentration
20
00
JC
18
00
E.
16
i
14
12
fc
C
4>
10
O
8
U
0>
6
£
4
p
-C
2
iZ
0
Copper-- Sucker spp
• Musde A Liver
Uver = 0.2714x + 5
.6142
R'= 0.04
A
A
A
£ ...
A
Musde = 0.2
R
= #N/A
A A
A
•«i .
-JU
4 6 8 10 12
Water Concentration (pig/L)
6 8 10 12
Water Concentration (|ig/L)
Figure 8.9. Relationship of fish tissue concentration to environmental metal concentrations for brook trout and
rainbow trout grouped and bluenose and flannelmouth suckers grouped for 3 metals. The best predictor of fish
tissue concentration is shown: sediment concentration for manganese and lead and water concentrations for
copper.
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EPA Gold King Mine Biological Response Report
8.2.5 Summary of NMDGF fish data
The fish tissue concentrations collected by the NMDGF in the Animas and San Juan rivers in August
immediately after the GKM release and again in March 2016 show general patterns of fish response as
illustrated in Figures 8.2 through 8.9. These figures explore the influence of specific environmental or
biological factors by averaging over the other possible influential factors. These generalized analyses
demonstrate that:
• Fish in the Animas River accumulated metals during the period after the GKM release when GKM
deposits were documented to be present in sediments and water (approximately 3 weeks);
• Fish in the San Juan River did not generally accumulate metals after the GKM release relative to
background;
• Some individuals in the population accumulated metals while many did not;
• Species varied in the amount and type of metals accumulated by individual cohorts;
• Liver tissue had greater concentrations of metals than muscle tissue;
• Some species accumulated more metals than others: the muscle of speckled dace and the livers of
bluehead sucker tended to have higher concentrations of metals than other species;
• Tissue concentrations of mercury and selenium were higher in the San Juan River than the Animas
8.3 Comparison of pre- and post-GKM fish tissue metal concentrations in
the Animas River among data providers
Fish filet data collected by multiple parties were compared to determine if fish tissue concentrations
measured in 2016 changed from the pre- release conditions. Pre-release data were limited to the Southern
Ute Indian Tribe fish tissue samples collected from the Animas River on their reservation between RKM
110 and RKM 130 in July 2015. EPA contractors sampled the same locations in Fall 2016 well after GKM
release deposits had been mobilized and removed from the river during the previous spring snowmelt (EPA
2016c). EPA contractor sampled filet + skin and SUIT sampled muscle plugs, so some differences due to
methods could occur. Fish tissue filets were also sampled from the Animas River in March 2016 at
relatively nearby locations soon after the GKM release in Colorado by CPW (see Table 6.1) and in New
Mexico by NMDGF, as discussed in section 8.2. The March 2016 sampling of muscle tissue by CPW in
Durango at RKM 94 and NMDGF at RKM 147 were added to this analysis to illustrate the general status of
metals in fish in March 2016 relative to pre-release conditions documented by the SUIT. Fish tissue
muscle concentrations averaging brown and rainbow trout in four datasets are shown in Figure 8.10.
The body burden of 8 metals in the SUIT and EPA trout data from the Animas River were low and within a
narrow range in March 2016, except for aluminum. CDPHE documented much higher concentrations of
aluminum in muscle than observed in other data sets in March. Metal concentrations were not assumed to
be at background conditions in Durango in March 2016 as GKM deposits were still in place in the middle
Animas, whereas they had been removed by monsoonal storms from the lower Animas by this time.
Aluminum was higher in Colorado while other metal concentrations were similar in CO and NM data given
detection limits. The similarity of SUIT and EPA data supports the conclusion that metal concentrations
were at background conditions in Fall 2016 after snowmelt in 2016. The NMDGF data at the downstream
location were also similar to the SUIT and EPA data.
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EPA Gold King Mine Biological Response Report
Aluminum
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
DL
SUIT CDPHE NMDGF EPA
Muscle Muscle Muscle Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
£, 0.006
SUIT
Muscle
Cadmium
DL
CDPHE
Muscle
NMDGF
Muscle
EPA
Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
Copper
5 1.0
2
1=
0.8
0.6 -
0.4
0.2
SUIT CDPHE NMDGF EPA
Muscle Muscle Muscle Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
3
9
Lead
1
vVi
¥V*
1
DL
IS! ra
1
i
SUIT
Muscle
CDPHE
Muscle
NMDGF
Muscle
EPA
Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
Manganese
5 0.6
u
0.5
I?
"I 0.4
c
0 0.3
re
1 °-2
5 o.i ¦
01
* 0.0
P
SUIT CDPHE NMDGF EPA
Muscle Muscle Muscle Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
Arsenic
»
E
SUIT CDPHE NMDGF EPA
Muscle Muscle Muscle Filet + Skin
July 2015 March 2016 March 2016 Fall 2016
Selenium
5 0.7
flj
2
DL
0.6
£
0.4
c
o
re
C
0.3
c
o
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EPA Gold King Mine Biological Response Report
8.4 Comparison of post-GKM fish tissue metals concentrations in the San
Juan River among data providers
Channel catfish (skinless filet) were sampled in two reaches of the San Juan River by the Navajo Nation
EPA (NNEPA) in June 2017. These data were compared to channel catfish collected by EPA contractors
(filet + skin) at several locations in the San Juan River in fall 2016 and by NMDGF in the upper San Juan
River near Fruitland and Farmington in March 2016 and August 2015 after the GKM event. No channel
catfish were collected at the San Juan upstream location at Archuleta or in Farmington at LVW 020
downstream of the Animas confluence. The concentrations of aluminum and trace metals are shown in
Figure 8.11 and selenium and mercury are shown in Figure 8.12.
Metals in tissue were generally very low and often less than detection limits. Results were similar among
datasets considering differences in detection limits. Metal concentrations in fish tissue were generally lower
in the San Juan than the Animas (more discussion on this in Chapter 9). Tissue concentrations collected by
NMDGF in the San Juan River in August 2015 after the GKM release were similar to those in fall 2016.
Levels of metals in fish tissue tend to increase slightly from upstream to downstream in the San Juan,
including copper, arsenic, selenium, mercury, manganese, and zinc. Other metals are similar along the
length of the San Juan River.
8.5 Fish tissue concentrations relative to fish consumption advisory levels
The primary purpose of the CPW, NMDGF, and NNEPA samplings was to report on the status of fish
tissue metal concentrations relative to consumption advisories in order to inform recreational and
subsistence fishers. Because there is a potential for fish to concentrate metals in their tissue over time,
Colorado and New Mexico collected fish again in the spring of 2016.
Colorado detected some metals in the muscles of brown and rainbow trout sampled from the middle
Animas River in August 2015 after the GKM release and in March 2016. CPW concluded that all tissue
samples fell below risk screening levels for all metals and fish could be consumed without risk. CPW
concluded that all tissue samples fell below risk screening levels for all metals and could be consumed
without risk. CPW also concluded that all tissue concentrations were within the range of concentrations
observed in other Colorado fish datasets and likely represented background levels (CPW 2016).
NNEPA (2017) reported that metals in the tissue of catfish in the San Juan River were below human health
consumption screening advisory levels.
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EPA Gold King Mine Biological Response Report
Channel Catfish-Aluminum
• EPA Contractor Filet+Skin A NNEPA--Musde filet
~ NMDGF-March 2016 NMDGF-lmmediate Post GKM
a a a
A A
NNEPA Detect Limit
•
•
•
•
•
250 300 350 400
River Distance from GKM (km)
Channel Catfish—Cadmium
• EPA Contractor Filet+Skin A NNEPA-Musde Filet
O NMDGF-March 2016 NMDGF-lmmediate Post GKM
9
E
§ 0.006
AAA
A
NNSPi
A A
Detect Limi
m •
•
• • •
EPA Contractor Detect Limit
250 300 350 400
River Distance from GKM (km)
Channel Catfish-Copper
• EPA Contractor Filet+Skin A NNEPA-Musde Filet
NMDGF-March 2016
NMDGF-lmmediate Post GKM
A
A
6 A
A
A
250 300 350 400
River Distance from GKM (km)
Channel Catfish-Lead
» EPA Contractor Filet+Skin A NNEPA-Musde Filet
NMDGF-March 2016
NMDGF-lmmediate Post GKM
AAA
A A
A NNEPA Detect Limit
NMDGF Detect Limit
•
•
•
EPA
• •
Contractor Detect Limit
250 300 350 400
River Distance from GKM (km)
Channel Catfish-Manganese
• EPA Contractor Filet+Skin A NNEPA-Musde Filet
~ NMDGF-March 2016 NMDGF-lmmediate Post GKM
Channel Catfish-Arsenic
•
•
AAA
w
•
A £
NNEPA Detect Umit
Detect Limit
NMDG
250 300 350 400
River Distance from GKM (km)
• EPA Contractor Filet+Skin
m NMDGF-March 2016
3
%
§
a0
£
A NNEPA-Musde Filet
NMDGF-lmmediate Post GKM
B
•
•
•
•
w
NMDGF Detect Limit
/v A A
A A
NNEPA Detect Limit
250 300 350 400
River Distance from GKM (km)
Figure 8.11. Tissue concentration of aluminum and trace metals in channel catfish at multiple locations in the
San Juan River. Data were collected by NNEPA and EPA contractors after 2016 snowmelt had returned
conditions to background. NMDGF data were collected in August 2015 immediately after the GKM release and
in March 2016. DL indicates samples were below the laboratory detection limit, which are shown as 50%
reported detection limit.
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EPA Gold King Mine Biological Response Report
Channel Catfish-Selenium
• EPA Contractor Filet+Skin
~ NMDGF-March 2016
A NNEPA—Muscle Filet
NMDGF-lmmediate Post GKM
•
•
•
•
•
A A A
NNEPA Detect Limit
A A
~ NMDGF Detect Limit
250 300 350 400
River Distance from GKM (km)
Channel Catfish--Mercury
ft EPA Contractor Filet+Skin A NNEPA—Musde Filet
NMDGF-March 2016 NMDGF-lmmediate Post GKM
•5 0.10
•
•
~ . A
A
A
•
~
a a
A
f
•
A
~
NMDGF Detect Limit
200 250 300 350 400
River Distance from GKM (km)
Figure 8.12. Tissue concentration of selenium and mercury in channel catfish at multiple locations in the San
Juan River. Data were collected by NNEPA and EPA contractors after 2016 snowmelt had returned conditions to
background. NMDGF data were collected in August 2015 immediately after the GKM release and in March
2016. DL indicates samples were below the laboratory detection limit, which are shown as 50% reported
detection limit.
8.6 Summary of metals in fish tissue
Fish take up metals from sediment and water through their diet and across their gills. Many metals are
essential for growth and survival and are non-toxic at low concentrations; however, some metals are
nonessential and toxic and even essential metals are toxic at high concentrations. Mining activities in the
headwaters of the Animas and ore processing facilities near population centers have left persistent
environmental contamination of metals in the upper Animas River. Watershed scale fish tissue sampling
has shown historic and ongoing elevated concentrations of many metals in fish that live in the upper
Animas River. Metals contamination affects fish survival and reproductive success in the most impacted
reaches within this area.
The GKM release caused a short-term spike in water concentrations and additional loading of metals into
the streambed within the already contaminated portions of the upper Animas River. The GKM-release also
elevated metals to levels not routinely observed in the lower Animas and San Juan rivers for some period of
time after the GKM plume passed through the system. Metals in sediment in the lower Animas River were
elevated for three weeks following the release; however, concentrations were much less than those
observed in the upper Animas.
Bioaccumulation of metals within the fish community was complex varying by species, metal, and
individual characteristics and exposure. Our analysis of fish tissue data collected from lower Animas and
upper San Juan rivers showed metals were significantly elevated in bluehead and flannelmouth sucker liver
and speckled dace muscle tissue within weeks after the GKM release in the section of the lower Animas
River that received GKM metals deposits. The degree of metal accumulation in liver differed by species,
sampling location, and among the metals, with aluminum, cadmium, lead and manganese exhibiting the
greatest concentrations. Cadmium and mercury in liver tissue and selenium in muscle were greater in the
San Juan than the Animas. Tissue samples collected after GKM deposits were cleared from the system the
following spring showed liver concentrations had declined to background levels. For the most part, the
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elevated liver concentrations in 2015 did not translate to elevated muscle concentrations. No fish mortality
is known to have occurred because of metals contamination in the Animas and San Juan rivers. There were
no fish population data available from the lower Animas River to help us understand if the metal
concentrations in fish tissue were sufficiently high to adversely affect the fish populations.
When fish were sampled the following spring and fall in 2016, the concentration of metals in muscle/filet
samples were similar to pre-release concentrations and were low throughout both rivers. Metal
concentrations in muscle tissue did not exceed human health consumption recommendations.
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CHAPTER 9 ONE-YEAR POST-GKM RELEASE: WATERSHED-SCALE
LONGITUDINAL TRENDS IN METAL BIOACCUMULATION
EPA benthic macroinvertebrate and fish tissue
(filet + skin) sampling produced the only
commonly collected and laboratory processed
data that characterized metal concentrations in
biota through the entire length of the Animas and
San Juan rivers. These data were collected by
EPA contractors in Fall 2016 and April 20176 as
part of the EPA's CMP (EPA 2016a). Sampling
occurred after June 2016 when GKM deposits
were mobilized from the rivers and transported to
Lake Powell during snowmelt runoff (EPA
2016c). Thus, the 2016 EPA results do not
characterize the full bioaccumulation potential
that may have occurred immediately after the
GKM release but rather are a better
characterization of background conditions.
Results from this sampling event can be used to
inform future tissue sampling study objectives.
Monitoring one-year post-GKM demonstrated a
continued strong longitudinal gradient of many
metals in sediment, water, and biota within the
Animas River, extending from the mining district
to the confluence with the San Juan River. Metals
measured in benthic macroinvertebrate composite
samples and fish filet from the EPA 2016/17
sampling are shown in Figures 9.1 and 9.2 with
sediment and water concentrations from samples
collected in 2016 (February through November
2016). These longitudinal trends are consistent
with the pre-release data presented in Chapter 2.
Sediment and water metal concentrations
generally decline from high values observed in
the impacted mining district by two to three orders of magnitude by the time the Animas joins the San Juan
River. In the Animas River, sediment metal concentrations were frequently greater than concentrations in
water. Metal concentrations in the San Juan River are typically less than the Animas and are similar
through the length of the river. In the San Juan River, metals in sediment were frequently equal to or less
than total water concentrations, which are strongly influenced by episodic stormflow and sediment loads
(EPA 2016c).
Like metals in sediment and water, EPA 2016/17 benthic macroinvertebrate and fish tissue data in the
Animas River showed a systematically declining pattern for many metals, including arsenic, lead, copper,
manganese, and zinc, as seen in earlier datasets (Figure 9.1; Chapter 2). Fish and benthic
macroinvertebrates living in the upper Animas River experience persistently higher metal concentrations in
0 EPA was unable to collect fish tissue samples from the lower Animas River and upper San Juan river sites during the fall
sampling (October and November 2016) and therefore collected remaining fish tissue samples the following spring in April 2017.
Table 9.1. Geometric mean metal concentration +/-1SD in
benthic macroinvertebrate composite samples collected in fall
2016 and fish filet samples (ppm dw) collected from the
Animas and San Juan rivers in fall 2016 and spring 2017.
Animas River
San Juan River
geometric mean
(± 1SD)
geometric mean
(± 1SD)
Benthic Macroinvertebrates
Aluminum
7,919
±4754
5,198
± 2,900
Arsenic
4.8
±5.1
3.2
± 1.7
Cadmium
2.1
±3.6
0.4
±0.4
Copper
60
±51.5
21.1
±3.9
Iron
10,997
± 14,369
4,058
± 2,366
Lead
49
± 184.9
3.6
±2.0
Mercury
0.021
±0.01
0.11
±0.05
Manganese
1,924
± 2,389
223
± 187
Nickle
6.6
±5.7
3.5
± 1.7
Selenium
1.4
±0.6
2.7
±0.7
Zinc
760
±822
112
±25
Fish Filet
Aluminum
2.1
±0.6
2.9
±5.1
Arsenic
2.1
± 1.0
2.0
±0.6
Cadmium
0.02
±0.04
0.02
±0.01
Copper
1.9
±0.8
1.8
± 1.0
Iron
21.4
±8.0
24.3
±20.0
Lead
0.03
±0.06
0.03
±0.02
Mercury
1.4
± 1.2
1.1
±0.9
Manganese
0.2
±0.3
0.7
±0.2
Nickle
0.05
±0.01
0.05
±0.03
Selenium
1.8
±0.4
1.8
±0.4
Zinc
36.0
±29.9
29.8
±5.7
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their environment and generally have higher metal body burdens (Figures 7.8 and 7.9). Metals in benthic
macroinvertebrate tissue had concentrations more similar to sediment than water. This trend is logical since
the benthic composite samples were analyzed with the gut content and casings, when applicable, and
therefore also contained some sediment. Metal concentrations in fish filet were consistently less than
benthic macroinvertebrate concentrations (Table 9.1). Measuring metals in fish filet provide a meaningful
measure of exposure to human consumption of fish, but do not reflect the total body burden given the
sequestration of metals to different organs that are not typically consumed (e.g., liver; see Chapter 8).
Metals that did not follow the general declining spatial gradient include aluminum, selenium, mercury, and
nickel (Figures 9.2). Aluminum in benthic macroinvertebrates and sediments was consistently high
throughout the Animas and San Juan rivers. Total aluminum in water was variable with the lowest total
aluminum concentrations in water measured near 100 RKM and the highest concentrations were measured
in the San Juan River. Selenium concentrations in benthic macroinvertebrates slightly increase with the
distance traveled downstream (Figure 9.2). The mean selenium concentration in benthic tissue collected
from the Animas River downstream of GKM was less than the San Juan (Table 9.1). The greatest nickel
concentrations in benthic macroinvertebrate tissue, on the other hand, were sampled from the middle
Animas locations, starting just upstream of Durango and into the Southern Ute reservation (71 through 123
RKM). Mercury in benthic macroinvertebrate and fish tissue clearly increased with distance downstream of
GKM, with greater concentrations observed in the San Juan than the Animas River (Table 9.1). Similar to
the middle Animas sampling locations 9426 (76.8 RKM) and Oxbow Park (90 RKM; see Chapter 7.2),
benthic macroinvertebrates collected from lower Animas site ADW-022 (148 RKM) had elevated
concentrations of many metals (As, Cu, Fe, Pb, Zn) when compared to the nearest upstream and
downstream sampling locations.
At a site scale, there was also wide variation in metal concentrations in fish tissue. This variation may be
partially due to annual variation in water and sediment concentrations or differences among species-
specific bioaccumulation rates. Fish tissue concentrations of the more soluble metals such as zinc, and
cadmium show affiliation with both sediment and water (Figure 9.1). The historic Bureau of Reclamation
La Plata Project reported fish tissue concentrations with the same general longitudinal pattern as the EPA
filet samples (Figures 2.5 - 2.8).
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Arsenic, As
oTotal Water Sediment •Invertebrates X Fish
1,000
Cadmium, Cd
oTotal Water Sediment •Invertebrates xFish
{» . .
•*' # *
_ o
i
> OOO °i
*
• ? *
<> A
0
10.00 #
k •
/ • •
100 o i
• t.
o * •
y 0° a 9 A
010 j * " V I I 8 f 0
3 *x. 00 * o *
J* m xk * x x x * xx x
0.01
ioo xk: 11oo
o ioo
Animas River
200 300 400 500
][ San Juan River
Distance from GKM (km)
Copper, Cu
o Total Water Sediment •Invertebrates % Fish
1,000
*
* •
* * J
: * x & w o y
«
X *
t
f
~
ioo
Animas River
200
][
300 400
Son Juan River
Animas River ] [ San Juan River
Distance from GKM (km)
Lead, Pb
o Total Water Sediment •Invertebrates xFish
10,000.00
1,000.00
i
j 100.00
i
: 10.00
• • * j
i* 1 i * i 4 o
, 2 * % * k ?
*=» jrs
rjist! s
•
0
r *
1 * *
i
100
Animas River
200
11
300
San Juan River
Distance from GKM (km)
Distance from GKM (km)
100,000
Manganese, Mn
o Total Water Sediment • Invertebrates x Fish
c 100
5
10
#
it •••
A 4 * ^ • — _
o
*
% of ^
0
ft
•
*
• 2
ft
A
•
; *
J X
X
x
x ' X
** X
X
X *
100 200 300 400
Animas River ][ San Juan River
Distance from GKM (km)
10,000
c 1,000
0
1
o Total Water
Zinc, Zn
Sediment •Invertebrates xFish
• »v .
* • •
[rTy.
li *A
•
•
•
#
X 0 'i *
° Og>
0 •
$ £
~
A
$
0
0
o ioo
Animas River
200 300 400
][ San Juan River
Distance from GKM (km)
Figure 9.1 Concentration of 2016 arsenic, lead cadmium, copper, lead, manganese and zinc in benthic
macroinvertebrate and fish filet (ppm dw), sediment (ppm dw), and dissolved water (ppb) with distance from
GKM (km). Fish filet data points are the average of the individual fish collected at the site.
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EPA Gold King Mine Biological Response Report
Aluminum, Al
OTotal Water Sediment •Invertebrates * Fish
100,000
2 1,000
• c
•# f
o
I i * • i
*
oo o
o
~
o
•
•
X
X*
X
X
* J!* X* * * X * * w x
X* * X *
0 100
Animas River
200 300 400
][ San Juan River
Distance from GKM (km)
100,000
Iron, Fe
o Total Water Sediment •Invertebrates x Fish
c 1,000 vo
100
10
% f4z 1
« 9
100 200 300 400
Animas River ] [ San Juan River
Distance from GKM (km)
o
Mercury, Hg
oTotal Water Sediment •Invertebrates XFish
c 1.50
o
1.00
0.50
0.00
X
\ * X
*
X
O *
X
| o *
X *
0 * \
3
o
r~*~* * 4°
ft
• •
f t % ft
•
0
1
0 100
Animas River
200 300
][ San Juan River
Distance from GKM (km)
Nickel, Ni
oTotal Water Sediment •Invertebrates XFish
A O
o c8 A °
~
0
o
A
•
•
o
~
•
ft
•
9
%
~
•
•
J _ x_
X
X^ X XX :KK XK X«x)^
X
X
X
X
X
0 100 200 300 400
Animas River ] [ San Juan River
Distance from GKM (km)
Selenium, Se
oTotal Water Sediment •Invertebrates XFish
L. f*/1"*
• X • *
X
•
6 fo ooo o
o o
o
0 100
Animas River
200 300 400
J [ San Juan River
Distance from GKM (km)
Figure 9.2 Concentration of 2016 aluminum, iron, mercury, nickel, and selenium in benthic macroinvertebrate
and fish filet (ppm dw), sediment (ppm dw), and dissolved water (ppb) with distance from GKM (km). Fish filet
data points are the average of the individual fish collected at the site.
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CHAPTER 10 SYNTHESIS AND DISCUSSION
In this report, EPA complied biological data from multiple sources to evaluate how the aquatic community,
populations, and metal sequestration in tissue responded to the GKM release. The sampling and analysis
approach were designed to address the following main questions:
• Were there changes in the abundance and diversity of macroinvertebrates and fish after the GKM
release?
• Did the biota take up metals associated with the release? If so, have concentrations returned to
background conditions?
Historic monitoring and assessment efforts have identified pre-existing adverse impacts to water quality,
sediment quality and biological communities in this watershed. New data collected post-GKM release were
compared to pre-release biological data and were evaluated with respect to the near-term biological
conditions (days to weeks following the release when GKM deposits were still present) and the long-term
biological conditions a year after the release (after deposits moved through the system).
10.1 Animas River aquatic community response
The Animas River is one of many rivers in the western US that is impacted by historic mining and ongoing
acid mine drainage. There is a longitudinal gradient in metal concentrations and biological condition from
the headwaters downriver reflecting the persistent contamination in the upper Animas River. The upper
Animas River (Silverton to Baker's Bridge) experienced the highest metal concentrations during the GKM
plume, the greatest number of water quality criteria excursions, and the greatest deposition of sediment
immediately following the plume. Although the majority of the release material was initially deposited in
the upper Animas, the deposits were present for a short duration (approximately 8 months), the quantity
was not large compared to legacy contamination, and concentrations were similar to what they had been
before the release (EPA 2016c, Rodriguez-Freire 2016).
For the upper Animas River, metal concentrations in benthic macroinvertebrate tissue were high in the pre-
release dataset and continue to be high following the GKM release (Chapter 7). A significant increase in
copper and decrease in manganese concentrations in benthic macroinvertebrate tissue were observed in post
release samples in 2015. A year later in fall 2016, most metals were elevated in benthic macroinvertebrate
tissue when compared to the 2014 pre-release and the 2015 post-release concentrations, yet the 2016
concentrations were similar to concentrations observed in 2012. The high concentrations in benthic
macroinvertebrate tissue in 2016 were also observed in the upstream and tributary samples suggesting that
something other than the GKM release contributed to the concentration change. Differences in field
collection methods, analytical methods, and the benthic community composition likely contributed to the
variability observed between the 2012/2016 and 2014/15 sampling years.
Historic biological monitoring conducted in this portion of the watershed over the last several decades has
established that the upper Animas downstream of the confluence with Cement Creek, Cement Creek and
several tributaries with historic mining impacts support limited benthic macroinvertebrate and fish
communities because of the poor water quality. Sensitive species that would be expected to respond to the
GKM release were historically extirpated from this section of the upper Animas leaving only some of the
most metal tolerant aquatic life and life stages present when the release occurred. Therefore, no clear
differences in the aquatic community structure were observed in the pre- and post-GKM release biological
data in the upper Animas River.
The benthic macroinvertebrate and fish populations in the Animas River generally improve in the middle
reach (below Baker's Bridge to the Southern Ute Indian Tribe-New Mexico border) and lower Animas
river (New Mexico reach). These reaches support more sensitive taxa that are not found in the upper
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EPA Gold King Mine Biological Response Report
Animas. As the GKM release moved through the river and approached the middle Animas river, both
dissolved and colloidal/particulate metal concentrations declined rapidly as chemical reactions and
hydraulic processes diluted, transformed, and deposited material. This resulted in fewer excursions of water
quality criteria and concentrations that are less likely to adversely affect aquatic biota. Therefore, we did
not observe a loss of or change in the more sensitive invertebrate and fish taxa at the downstream locations,
and for some metrics, a slight improvement was observed a year following the event. With regard to the
individual benthic macroinvertebrate metrics, %EPT was not significantly different between the pre- and
post-GKM release time periods; however, total taxa were significantly different, with the post-GKM
release time period showing greater overall total taxa compared to the pre-GKM release (Chapter 5).
Additionally, localized high metal concentrations in post-release benthic tissue were observed in the middle
Animas; however, these sites were not consistent among years (Oxbow Park in 2015 and 9426 in 2016) and
did not have pre-release data to be able to understand if the high concentrations were the result of the
GKM-release (Chapters 7 and 9).
Our analysis of the 2015 post-GKM release fish data collected by CPW from the Animas River near
Durango (Chapter 6) agrees with existing state analyses, reports, and press announcements that conclude
fish were not exposed to acutely toxic concentrations (CPW 2015, NMDGF 2015). Fish populations near
Durango, including stocked trout and native species, were at historic highs one month following the GKM
release. Trout biomass, density, quality and population demographics were similar or increased relative to
those in the previous year, a result that may have been influenced by weather and water conditions that year
as well as reduced angling after the GKM event (CPW 2015).
CDPHE and NMDGF collected fish tissue samples when the maximum effect of the GKM release was
observed (August 2015) and the following spring (March 2016). CDPHE's sampling focused on trout filet
samples in the Durango area. CDPHE (2016b) reported that tissue concentrations of Al, As, Cu, Mn, Ni,
and Zn were detected in brown and rainbow trout in August 2015, although levels were well below fish
consumption screening levels. GKM deposits remained in the middle Animas river through the winter. In
March 2016, most metals were less than the detection limit in both species, except for aluminum.
Aluminum concentrations were greater in March 2016 than August 2015 (immediately following the
release), yet continued to be well below consumption screening levels.
Questions have remained about the potential long-term impacts to fish reproduction and larval fish that
were exposed to the plume since larval fish are typically more sensitive to toxics, fish shocking techniques
do not assess larval life stages, and larval fish mortality may not be as visually apparent as an adult fish kill.
Our review of the 2016 fish abundance data for naturally reproducing species in the middle Animas River
(suckers and sculpin) shows that populations are within the normal range; however, it can be challenging to
determine if a specific life stage is impacted when the species has a long-life expectancy. The maximum
life expectancy for the bluehead and flannelmouth suckers is relatively long (25 years) compared to the
mottled sculpin (6 years; Page and Burr 2011). Additional monitoring would be needed to address
questions related to potential adverse effects to younger life stages and the reproductive output of the
naturally reproducing populations.
The lower Animas River (New Mexico segment) had limited historic biological data to support a pre- and
post-GKM release analysis. No fish population data were identified and the pre-release benthic
macroinvertebrate data was limited to one event in 2009 at ADW-010 (163 RKM). Furthermore, pre-
release concentrations of metals were well characterized in the water, sediment, and biota in this
downstream segment of the river. Due to these data limitations, we were unable to determine if the aquatic
community changed in response to the release.
Although the pre-release data were limited for this segment of the river, the NMDFG fish tissue sampling
design for the lower Animas and upper San Juan rivers provided meaningful statistical comparisons of
near-term release and long-term metal bioaccumulation following the release by including multiple species,
replicates, tissue types (muscle and liver) and sampling dates. Samples were collected in August 2015 and
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the following spring (March 2016) after the sediments deposited in the lower Animas were removed by a
monsoonal storm event. Monitoring showed that sediment concentrations declined to background levels
after this storm and remained generally low through the winter months. Metals were significantly elevated
in bluehead and flannelmouth sucker liver and to a lesser extent in muscle tissue during August 2015 in the
lower Animas River at locations with elevated GKM metals in water and sediment. For the most part,
however, high concentrations in the liver did not translate to high concentrations in the muscle. When fish
were sampled the following spring in March 2016, the concentration of metals were low throughout both
rivers. Additionally, the body burdens of 8 metals in the pre-release (SUIT) and post-release EPA fish data
taken at the same locations were similar despite differences in methods, supporting the conclusion that
biological conditions were at background conditions in fall 2016. The CDPHE and NMDGF and data at the
up and downstream locations were also very similar to the SUIT and EPA data.
NMDGF (2015) expressed particular concern about acute effects from copper, due to the importance of this
metal in contributing to toxicity in the upper Animas (Besser et al. 2001; Besser and Leib, 2007; EPA
2015). Copper concentrations in sediment were significantly elevated in the lower Animas immediately
after the GKM event, but were less than historic concentrations measured in the upper Animas. Copper and
cadmium fish tissue concentrations were similar between fall 2015 and spring 2016 in the lower Animas,
and always had higher concentrations in the liver than in the muscle. Copper concentrations in the livers of
brown trout were comparable to those reported for brook trout in the upper Animas River in Besser et al.
(2001) and Besser et al. (2007). Copper concentrations were also elevated in the livers of flannelmouth and
bluehead suckers (Chapter 8). Copper was not generally detected at high levels in macroinvertebrates
collected from the lower Animas in August following the release in 2015 and the following spring in 2016.
However, concentrations observed at two lower Animas locations in 2016 were similar to concentrations
measured in the upper Animas River (Chapter 9). The NMDGF data highlighted that metals are not
uniformly taken up within a fish population and the macroinvertebrate community when metal
concentrations increase over a short duration. There were no fish population data available from this
section of the Animas River to help us understand if the metal concentrations in fish tissue were sufficiently
high to adversely affect the fish populations.
10.2 San Juan River aquatic community response
The GKM release had the potential to affect the San Juan aquatic community through two different
avenues. There were potential direct toxic and physical effects resulting from the metals in the plume itself
(e.g., mortality and metal avoidance), as well as indirect physical changes due to the closure of the
irrigation canals and the additional water release from the Navajo Dam (e.g., increase in flow, temperature
changes, increased suspended sediment). With respect to direct effects, by the time the GKM plume
reached the confluence with the San Juan River, total metal concentrations had declined by three orders of
magnitude from what they were when the plume entered the Animas because of the combined effects of the
dilution, chemical reactions, and deposition. The excursions of aquatic life water quality criteria in the San
Juan River were limited to metals that are naturally high in the sediment and water based on monitoring
data upstream of the confluence, making direct GKM related toxic effects unlikely. With respect to indirect
effects, the dam release was intended to mitigate the impact of the GKM plume and contributed to the
lower metal concentrations. This release increased flow and suspended sediment for several days, yet
intermittent high flow events in response to precipitation are normal in the San Juan. The temperature
changes in the San Juan upstream of the Animas River confluence associated with the dam release was not
normal. USFWS (2016) suggested this may have contributed to fish movement downstream.
Metals in fish tissue samples collected from the San Juan River by all data sources (EPA, NMDGF and
NNEPA) were generally very low and often less than detection limits, consistent with the concentrations
observed in the water and sediment. Results were similar among datasets considering differences in
detection limits. Metal concentrations in fish tissue were generally lower in the San Juan than the Animas.
Tissue concentrations collected by NMDGF in the San Juan River immediately after the GKM release were
similar to those in fall 2016.
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The robust fish population dataset collected by the FWS in the San Juan River showed that fish abundance
in 2015 and 2016 was generally within pre-release norms. The exception to this was the abundance of
bluehead sucker, flannelmouth sucker and speckled dace in the middle reaches of the San Juan in both 2015
and 2016. There are many possible explanations for the suppressed abundance of these species. Their low
post-event abundance coincided with historically high populations of predator/competitor species (i.e.,
razorback sucker, Colorado pikeminnow and channel catfish). The San Juan River downstream of Navajo
reservoir is managed for the recovery of the razorback sucker and Colorado pikeminnow, including annual
stocking and removal of non-native fish.
We cannot say if the combined changes in the physical and chemical conditions that occurred as the plume
move through the San Juan River contributed to abundance changes in certain fish species; however, the
aquatic life water quality criteria excursions during the GKM event were limited and the sediment
suspended in the river due to the increased flow was similar to a moderate-sized storm event. It is more
plausible that a combination of ecological and physical interactions, and/or fisheries management actions
contributed to the observed changes, rather than a result of the GKM release.
10.3 Watershed scale bioaccumulation of metals
The EPA 2016 biological sampling was the first effort to obtain biological data that covered the entire
Animas and San Juan rivers in a single sampling event with consistent sampling methods, which allowed us
to evaluate watershed-scale longitudinal patterns in bioaccumulation. The wide range and systematic
declining pattern of background metals in the Animas River establishes an underlying stressor gradient on
biological communities. Metals measured in benthic macroinvertebrates and fish tissue samples generally
followed the systematic declining pattern observed in water and sediment collected after the GKM release.
These results suggest that tissue concentration of many of metals are in an equilibrium with their prevailing
environmental concentrations. The highest metal concentrations in tissue were observed in the upper
Animas and the lowest concentrations were observed in the San Juan. The exceptions to this pattern include
aluminum, selenium, mercury and nickel. Aluminum concentrations are elevated in sediment and benthic
macroinvertebrate tissue throughout the Animas and San Juan rivers and are consistent in fish tissue.
Greater selenium concentrations were measured in benthic macroinvertebrates sampled from the San Juan
River when compared to the Animas River. We were unable to determine whether metal concentrations in
tissue were predominately influenced by water concentrations, sediment concentrations, or dietary
exposure.
10.4 Future monitoring considerations
10.4.1 Sampling and analytical considerations
Our ability to conduct a watershed-scale analysis with data collected by all data providers was limited by
the different sampling and analytical methods and revealed the need for a consistent sampling approach.
This was especially true for studies focusing on bioaccumulation of metals. Different study objectives (e.g.,
human health vs. ecological risk) will define the parameters measured and type of tissue sample that were
collected, resulting in datasets that are challenging to compare. A fish tissue study evaluating human health
risks will target fish tissue samples that represent the portion of the fish that is typically consumed.
Although this sounds straight forward, sampling efforts to address this objective have included three
different types of tissue samples: filet, filet with skin and muscle plugs. There is limited literature that
address how the retention of the skin in the laboratory analysis will influence the result, but there is reason
to believe that the two samples are not directly comparable. The small amount of tissue collected with a
muscle plug can limit the analytes and types of analyses creating data gaps when compared to other dataset,
yet this sampling approach represents the only non-lethal technique available.
Measuring metals in the whole fish and/or liver provides meaningful data to evaluate ecological risk. Our
review of the fish liver data collected by NMDGF showed that liver samples provide more information on
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EPA Gold King Mine Biological Response Report
metal bioaccumulation than muscle samples since it is more responsive to environmental conditions
(Chapter 8); however, liver data are not directly comparable to or useful for studies that are focused on
human health concerns. Additionally, the bluehead and flannelmouth suckers were generally more
responsive to metals than trout and accumulated Pb and A1 in their livers. These fish species are not
typically targeted for tissue monitoring given the human consumption study objectives. If ecological risk,
either to the fish or wildlife continues to be a question of concern, researchers should consider expanding
the target species and the collection of additional tissue types (i.e., liver or the remaining carcass to
estimate whole body concentrations).
Benthic macroinvertebrate tissue studies have equally variable sampling techniques making it challenging
to compare data from different sources. The collection of sufficient benthic macroinvertebrate tissue
sample for metal analysis can be labor intensive, requiring several hours from the field crew members to
collect 2 or more grams of tissue typically required by the lab. This is especially true when the
macroinvertebrate community is limited to begin with or dominated by small individuals (e.g., early instars,
chironomids). Although laboratories are able to accommodate small tissue samples with micro digestion
techniques, this introduces method variability into results and can increase method detection limits.
When caddisflies are present at a site, the study objectives will determine if the field crew should remove
the external casings prior to sample shipment to the lab. There are reasons to support both sampling
methods. Fish will typically consume the caddisfly larvae with their casings, which support the retention of
the case in the analysis; however most of the casing materials are not biologically available and will pass
through the fish without accumulating in the tissue. The potential for the case to increase the exposure to
the fish is not well understood. The acid digestion techniques for a tissue sample are weaker than those
used to digest a sediment sample. If sediments are present, in the form of casings or the gut of the
organism, this will typically result in greater metal concentration because of partial digestion of the
sediments. If the concentration of metal in the tissue is a future area of focus, one would want to consider
incorporating a gut content purge prior to analysis so the measurement represents metal assimilation (Sola
and Prat 2006).
We received a mix of tissue metals data that were expressed as wet weight (ww), dry weight (dw) and "as
received", which was treated equivalent to a wet weight. It is common to report fish tissue results as a ww
concentration when evaluating human health concerns and dw when evaluating ecological risk. It is simple
to convert a sample from ww to dw or dw to ww if the sample moisture content is reported (Chapter 3.4.6).
Moisture content is measured by oven drying the sample at 60°C until constant weight is recorded. It
typically requires additional tissue sample for analysis and must be planned for when determining the total
mass of tissue needed for laboratory analyses. When the moisture content is not reported by the lab, it is
common to estimate the moisture content in fish filet samples since they typically range from 70-80%
moisture (30-20% solids), regardless of size and fish species (Lusk 2005, EPA 2016d).
The moisture content of benthic macroinvertebrate samples, on the other hand, is more variable and
challenging to estimate. This is especially true when significant differences in taxa are observed between
sampling locations. A benthic assemblage dominated by soft bodied organisms (e.g., tipulids, nematodes,
chironomids) will have a different moisture content than an EPT dominated assemblage. This change in
benthic assemblage composition likely contributed to the wide range of percent solid measurements
observed in the study area (Animas River mean percent solid = 23.4%, range = 15.9%-33.5%; San Juan
River mean percent solid = 14%, range = 8.5%-22.7%). We minimized the uncertainty in introduced into
our analysis by using the percent solids measured from a sample collected from the same location on a
different date, or the mean percent solids observed in the watershed, depending on data availability.
In summary, the accumulation of metals in benthic macroinvertebrates and fish is notoriously variable as
noted in this report, the many historic studies in the Animas River (Besser et al. 2001; Anderson 2007,
Besser et al. 2007, Besser and Leib 2007; EPA 2015) and in other mining impacted streams (Mebane et al.
2012, Cadmus et al. 2016, Mebane et al. 2017). Complexity results from many aspects of metals exposure
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EPA Gold King Mine Biological Response Report
and response, including spatial distribution of metals, differences among macroinvertebrate and fish species
in reacting to metals, and differences among individual uptake within a species. The NMDGF data
highlighted that metal bioaccumulation is not consistent within a fish population and a macroinvertebrate
community when metal concentrations increase over a short duration. Some individuals and taxa
accumulated metals while many did not.
10.4.2 Opportunities for future watershed-scale monitoring and analysis
The extensive post-GKM monitoring program conducted throughout the Animas and San Juan rivers by
EPA, states and tribes revealed patterns of metal concentrations that were not comprehensively studied.
EPA (2016c) highlighted the importance of seasonal monsoonal storms that typically occur in late summer
in the lower Animas and San Juan rivers. These storms can generate high concentrations of dissolved and
particulate metals. Relative metal concentrations are consistent with the local lithology of the contributing
watersheds and the mass of metal is consistent with sediment loads (EPA 2016c). Aquatic life water quality
criteria are exceeded at times during snowmelt and monsoonal rain events. The relative role of these events
on the condition of the aquatic community compared to other stressors in the watershed is not well
understood. Future monitoring of these segments may improve the understanding of the sources and
importance of metals to aquatic biota during these events.
Aluminum is one of the metals measured at high concentrations during snowmelt and storm events. It was
also a major component of the GKM release and contributed to the majority of aquatic life water quality
criteria excursions that were observed during the plume (EPA 2016c). Excursion frequency differed by
location in the river and by the state or tribal water quality criteria used in the analysis. EPA published draft
updated aluminum aquatic life ambient water quality criteria for freshwaters in July 2017 that takes into
account the latest scientific knowledge regarding aluminum toxicity to aquatic life (EPA-822-P-17-001).
The draft criteria are modified by the ambient water quality parameters that are known to influence metal
bioavailability. The more bioavailable the aluminum is, the more likely it is to cause a toxic effect. The
water quality parameters that have the greatest impact on aluminum's bioavailability are pH, DOC, and
hardness.
• pH: a low pH generally makes it easier for aluminum to be dissolved, and therefore more
bioavailable. At higher pH, aluminum speciation changes make it more bioavailable.
• DOC: higher dissolved organic carbon reduces the bioavailability of aluminum because it binds to
form aluminum complexes.
• Hardness: higher hardness values mean there are more ions present that compete with aluminum.
This makes aluminum less bioavailable.
Longitudinal analyses presented in Chapter 9 identify that aluminum is consistently high in the water,
sediment and benthic macroinvertebrate tissue throughout the Animas and San Juan rivers. States and tribes
may want to consider reviewing and updating their aluminum aquatic life criteria following the publication
of a final criteria recommendation to aid in the analysis of future aluminum data.
This report identified a number of metals and biological datasets relevant to the biological condition of
aquatic communities in the Animas and San Juan rivers. These data include extensive research and studies
on metals in the headwaters of the Animas River conducted by multiple organizations to establish resource
status and inform management decisions and the extensive water, sediment, and biological monitoring
conducted over the two years following the GKM release in August 2015. These studies have established a
general pattern of persistent metals impacts on biota in the rivers, especially in the upper Animas River, and
identified general response to the relatively short-term GKM release. The robustness of pre- and post-event
analyses of biological datasets collected by different organizations for different purposes was limited due to
documented and undocumented differences in methods.
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Jones, W.R. 2007. History of mining and milling practices and production in San Juan County, Colorado,
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Environmental Effects of Historical Mining in the Animas River Watershed, San Juan County, Colorado.
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for consistency in a national assessment: the challenges of applying a reference-condition approach at a
continental scale. Journal of the North American Benthological Society 27(4): 860-877.
Luoma, S.N. 1983. Bioavailability of trace metals to aquatic organisms—A review. The Science of the
Total Environment 28:1-22.
Luoma, S.N. and Rainbow, Philip S. 2005. Why is metal bioaccumulation so variable? Biodynamics as a
unifying concept. Environmental Science and Technology 39(7): 1921-1931.
Lusk, J.D. E. Rich and R. S. Bristol. 2005. Methyl mercury and other environmental contaminants in water
and fish collected from four recreational fishing lakes on the Navajo Nation, 2004. Prepared by U.S. Fish
and wildlife Service. Prepare for the Navajo Nation Environmental Protection Agency.
https://www.fws.gov/southwest/es/newmexico/documents/final nnlfwqi report.pdf
Mebane, C.A., F.S. Dillon, and D.P Hennessy. 2012. Acute toxicity of cadmium, lead, zinc, and their
mixtures to stream-resident fish and invertebrates. Environmental Toxicology and Chemistry 31(6): 1334-
1348.
Mebane, C.A. T.S. Schmidt, and L.S. Balistrieri. 2017. Larval aquatic insect responses to cadmium and
zinc in experimental streams. Environmental Toxicology and Chemistry 36 (3):749-762.
Mountain Studies Institute. 2016. Animas River 2015 benthic macroinvertebrate (BMI) report. Gold King
Mine release monitoring. June 2016. Prepared by Scott Roberts, Mountain Studies Institute, Durango, CO.
Prepared for U.S. EPA Region 8, Denver, CO.
Mountain Studies Institute. 2017. Animas River 2017 benthic macroinvertebrate assessment. Prepared by
Scott Roberts, Mountain Studies Institute, Durango, CO. Prepared for Trout Unlimted-5 Rivers Chapter,
Southwestern Conservation District, City of Durango, La Plata County, and Colorado Parks and Wildlife.
Navajo Nation Environmental Protection Agency. 2017. San Juan River Fish Tissue Contamination Study.
November 2017. Prepared by Tetra Tech, Inc, Center for Ecological Sciences, Owings Mills, MD.
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New Mexico Environment Department. 2013. Benthic Macroinvertebrate Sampling. Standard Operating
Procedure 11.1. Effective date 5/01/2013. https://www.env.nm.gov/surface-water-qualitv/sop/
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New Mexico Department of Game and Fish. 2015. New Mexico wildlife and fisheries resource potentially
affected by the Gold King Mine toxic liquid release. August 14, 2015.
Page, L. and B. Burr. 2011. Peterson field guide to freshwater fishes of North America. 2nd ed. Houghton
Mifflin Harcourt, Boston, MA.
Paquin P.R., J.W. Gorsuch, S. Apte, G.E. Batley, K.C. Bowles, P.G.C. Campbell, C.G. Delos, D.M. Di
Toro, R.L. Dwyer, F. Galvez, R.W. Gensemer, G.G Goss, C. Hogstrand, C.R. Janssen, J.C. McGeer, R.B.
Naddy, R.C. Playle, R.C Santore, U. Schneider, W.A. Stubblefield, C.M. Wood, and K.B Wu. 2002. The
biotic ligand: a historical overview. Comparative Biochemistry and Physiology, Part C. 133: 3-35.
Rodriguez-Freire, L., S. Avasarala, A.S. Ali, D. Agnew, J.H. Joover, K. Artyushkova, D.E. Latta, E.J.
Peterson, J. Lewis, L.J. Crossey, A.J. Brearley, and J.M. Cerrato. 2016. Post Gold King Mine spill
investigation of metal stability in water and sediments of the Animas River Watershed. Environmental
Science and Technology. 50: 11539-11548.
Stoddard, J.L, A.T. Herlihy, D.V. Peck, R.M. Hughes, T.R. Whittier, and E. Tarquinio. 2008. A process for
creating multimetric indices for large-scale aquatic surveys. Journal of the North American Benthological
Society 27(4): 878-891.
Sola, C. andN. Prat. 2006. Monitoring metal and metalloid bioaccumulation in Hydropsyche (Trichpera,
Hydrosychidae) to evaluate metal pollution in a mining river. Whole body versus tissue content. Science of
the Total Environment 359:221-231.
Southern Ute Indian Tribe SUIT. 2015. Collection of macroinvertebrates. Standard Operating Procedure
#8, Revision No. 3. Environmental Programs Division, Water Quality Program, Ignacio, CO. May 1, 2015.
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the Final Environmental Impact Statement. Appendix B. April 1996. United States Department of the
Interior, Bureau of Reclamation, Washington, DC.
U.S. EPA. 1979. Assessment of Energy Resource Development Impact on Water Quality: The San Juan
River Basin. EPA-600/7-79-235. Environmental Monitoring and Support Laboratory, Las Vegas, NV
89114.
U.S. EPA. 2013a. National Rivers and Streams Assessment 2013-2014: Field Operations Manual - Non-
Wadeable. EPA-841-B-12-009a. U.S. Environmental Protection Agency, Office of Water Washington, DC
U.S. EPA. 2013b. National Rivers and Streams Assessment 2013-2014: Field Operations Manual -
Wadeable. EPA-841-B-12-009b. U.S. Environmental Protection Agency, Office of Water Washington, DC.
U. S. EPA. 2015. EPA Region 8, Upper Animas Mining District: Draft Baseline Ecological Risk
Assessment. April 2015. http://www2.epa.gov/region8/upper-animas-mining-district-draft-baseline-
ecological-risk-assessment
U.S. EPA. 2016a. Post-Gold King Mine release incident: conceptual monitoring plan for surface water
sediments and biology. March 2016. https://www.epa.gov/sites/production/files/2016-03/documents/post-
gkm-final-conceptual-monitoring-plan 2016 03 24 16.pdf
U.S. EPA. 2016b. Office ofWater and Office of Research and Development. National Rivers and Streams
Assessment 2008-2009 Technical Report (EPA/841/R-16/008). Washington, DC. March 2016.
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U.S. EPA. 2016c. Analysis of the Transport and Fate of Metals Released from the Gold King Mine in the
Animas and San Juan Rivers (Final Report). U.S. Environmental Protection Agency, Washington, DC,
(EPA/600/R-16/296).
U.S. EPA. 2016d. Technical Support for Fish Tissue Monitoring for Implementation of EPA's 2016
Selenium Criterion. Draft. U.S. Environmental Protection Agency, Washington, DC (EPA 820-F-16-007).
U.S. EPA 2016e. National Rivers and Streams Assessment 2008-2009: A Collaborative Survey U.S.
Environmental Protection Agency. Office of Water and Office of Research and Development. Washington,
DC. March 2016. (EPA/841/R-16/007).
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Restore and Protect Impacted Communities. August 1, 2016.
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the San Juan River:2015. Interim Progress Report. Final Report 6/15/2016. Funded by U.S. Bureau of
Reclamation, Salt Lake City Projects Office Agreement #R13PG40052. U.S. Fish and Wildlife Service,
445 West Gunnison Ave. Suite 140, Grand Junction, CO 81501.
U.S. Fish and Wildlife Services. 2000. Long term monitoring of sub-adult and adult large-bodied fishes in
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USGS Professional Paper 1651.
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APPENDIX A: SAMPLING LOCATIONS AND ASSOICATED SAMPLING
IDENTIFICATIONS
Appendix A. Sampling Sites: the description, location and additional sampling locations sampled by other organizations that are identified under the
GKM_ID as sites that are similar for pre- and post-GKM release comparisons of biological data. * identifies sites that act as background/reference for
the release.
Location
(GKMJD)
Associated Location(s)
Site Organization
Latitude
Longitude
Descri ption/Location
USGS
gage
available?
CC48
CC48
09358550 (gage)
323
EPA - superfund
USGS
CORW
37.818115
37.819984
-107.661678
-107.663275
Cement Creek upstream from Animas at
gage
Y
CC49
CDPHE
37.80999
-107.66069
Cement Creek at confluence
N
CC0001
ARSG
A68*
A68
09358000 (gage)
103
EPA - superfund
USGS
CORW
37.810983
37.811202
-107.65936
-107.659167
Animas River updtream of Cement Creek:
14th Street Gauge @ 13th Street Bridge
Y
M34*
M34
EPA
37.802921
-107.672724
Mineral Creek just upstream of the Animas
Y
09359010 (gage)
USGS
37.8028
-107.6722
River
A72
EPA
37.790017
-107.667536
Animas River access from Road 31 in
Silverton, CO
A72
09359020 (gage)
82
3611
3517
USGS
CDPHE
CORW
CPW
37.79027
-107.667578
Animas River at gauge below Silverton
upstream end of Animas River #3
Y
A73
3442
EPA
CORW
37.72215833
-107.6548278
Animas River upstream of Elk Creek; access
from railcar B
N
A73
Animas River at Elk Park, approximately 200
3516
CPW
37.72643
A-l
-107.65517
m upstream of Elk Creek; middle of Animas
River #3
N
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EPA Gold King Mine Biological Monitoring Report
Location
(GKMJD)
Associated Location(s)
Site Organization
Latitude
Longitude
Descri ption/Location
USGS
gage
available?
A75D
A75D
3438
09359500 (gage)
EPA
CORW
USGS
37.59793424
-107.7753268
Animas River upstream of Cascade Creek;
access from railcar B
Animas upstream of Cascade Creek
Animas River at Tall Timbers
Y
3515
CPW
37.59996
-107.77032
Animas River, below Crazy Women Gulch
TeftSpur
CPW
downstream site on Animas River #3
Bakers Bridge
Bakers Bridge
GKM02
EPA
EPA
37.455731
37.454134
-107.801095
-107.801601
Animas River at Bakers Bridge 20 miles south
of Silverton
N
88
CORW
81
CDPHE
37.45871
-107.79915
James Ranch
James Ranch
MSI
37.417822
-107.814819
Animas River at James Ranch
EPA
37.385148
-107.836946
9426
9426
89
CDPHE
CORW
37.38506
-107.83686
Animas River near Trimble Bridge
downstream of Hermosa Creek
N
Oxbow Park
Oxbow Park sediment only
EPA
37.309037
-107.855714
Animas River at Oxbow Park
N
MSI
32nd St Bridge
32nd St Bridge
371759107520601
3577
EPA
USGS
CORW
37.294805
37.299991
-107.870469
-107.868199
Animas River near Bridge at 32nd Street in
Durango
N
Animas-Rotary Park
EPA
37.280534
-107.876622
Animas River at Rotary Park
Y
Animas-Rotary
Park
09361500 (gage)
91
3576
USGS
CORW
CORW
37.280718
-107.876927
CORIVWCH_WQX-91
RCWWN
37.27932
-107.87966
ANIDURCO
Above Lightner
Above Lightner
MSI
37.26892921
-107.8862952
Animas River upstream of Lightner Creek
Animas River at DHS pedestrian bridge to 9th
12150
CPW
37.274429
-107.88454
Street, approximately 350 m downstream of
Rotary Park (this could go with GKM05)
GKM05
GKM05
09361500 (gage)
9418
EPA
USGS
CDPHE
37.268704
-107.885857
Animas River under bridge at corner of US
550 and US 160
Y
9423A
CDPHE
37.2745
-107.8843
AR19-3
SUIT
Animas River at the Southern Ute Boundary
AR19-3
Purple Cliffs
EPA
37.2213842
A-2
-107.854161
Animas upstream of the Southern Ute
Boundary
Y
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EPA Gold King Mine Biological Monitoring Report
Location
(GKMJD)
Associated Location(s)
Site Organization
Latitude
Longitude
Descri ption/Location
USGS
gage
available?
09363500 (gage)
USGS
Animas River at Cedar Hill
GKM01
EPA
37.221297
-107.859598
Boat launch under River Rd. Bridge
3.71319E+14
USGS
Animas upstream of the Southern Ute
Boundary
3590
92
CORW
CDPHE
37.221542
-107.859455
Animas upstream of the Southern Ute
Boundary
Animas upstream of the Southern Ute
Boundary
NAR1
SUIT
Animas River at the Southern Ute Boundary
10245
CPW
Animas River at Purple Cliffs
AR16-0
AR16-0
Animas 1
Animas @ Basin Creek
37.187031
37.187051
37.185
-107.869928
-107.878685
-107.87833
AR7-2
AR7-2
NAR4
SUIT
SUIT
37.084992
-107.878383
Animas River upstream of Florida River
N
EPA
37.085161
-107.879233
Animas River south of Durango - access via
Road 213
AR2-7
SUIT
37.04431
-107.872392
Animas River downstream of Florida River
confluence
AR2-7
AR2-7a
EPA
37.032292
-107.875455
Animas River - access near Heaven on Earth
Rd
NAR6
SUIT
37.024806
-107.8738
N
AR0028
SUIT
37.025833
-107.872778
Animas @ Twin Crossings
Animas 2
SUIT
37.027275
-107.874365
ADW-022
ADW-022
AR-1
EPA
NMDGF
36.920559
36.933295
-107.909909
-107.909073
Animas River at the Aztec Domestic Water
System Intake, near Cedar Hill
N
ADW-021
ADW-021
EPA
36.872838
-107.960741
Animas River at Intake Sampling Location
N
ADW-010
EPA
36.838545
-107.992183
09364010 (gage)
USGS
36.837463
-107.991684
Y
ADW-010
66Animas028.1
66NM078.1 (NM0020168)
AR-2
NM
NM
NMDGF
Animas River at Hwy 550 Bridge below Aztec
FW-012
EPA
Animas River north of Farmington, NM
FW-012
66Animas017.4
4136
NM
CORW
36.783635
-108.102111
Animas River at Intake Sampling Location
N
FW-040
FW-040
EPA
Animas River upstream of the San Juan River
Y
A-3
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EPA Gold King Mine Biological Monitoring Report
Location
(GKMJD)
Associated Location(s)
Site Organization
Latitude
Longitude
Descri ption/Location
USGS
gage
available?
09364500 (gage)
USGS
36.719664
-108.207125
66Animas001.7
NM
SJAR
EPA
36.707467
-108.150813
San Juan River just upstream of the Animas
N
66SanJual01.6
NM
River
SJAR*
SJR-1
NMDGF
36.706709
-108.19835
San Juan River upstream of the Animas River
near Bloomfield
NMR9-0905
FW08NM022
EPA-NRSA
EPA-NRSA
36.70792574
-108.2114498
LVW-020
EPA
36.730556
-108.251046
San Juan River at Intake Sampling Location
LVW-020
09365000 (gage)
USGS
36.73588701
-108.2539868
San Juan River downstream of the
confluence with the Animas
N
66SanJual00.2
NM
36.7217
-108.224
SJR-2
San Juan River downstream of the
SJLP
EPA
confluence with the Animas near Northern
SJLP
09365000 (gage)
67SanJua096.3
USGS
NM
36.73588701
-108.2539868
Edge Casino
San Juan River in Farmington, NM
Y
SJFP
EPA
36.74815602
-108.4120157
SJFP
NMRM-1005
9367540
67SanJuan082.6
SJR-3
EPA-NRSA
USGS
NM
NMDGF
36.75051779
-108.4181808
San Juan River near Fruitland, NM
N
SJSR
SJSR
09368000 (gage)
EPA
USGS
36.78162422
-108.6927838
San Juan River near Shiprock, NM
Y
SJ4C
EPA
36.99621613
-109.0046838
San Juan River near Four Corners (CO/NM
border)
SJ4C
4954000
09371010 (gage)
Utah
USGS
37.002775
-109.03177
San Juan River near Four Corners (near Hwy
161 in CO/UteMtnUte)
San Juan River near Four Corners
Y
SJMC
EPA
37.25822644
-109.3106036
San Juan River upstream of Montezuma
N
SJMC
4953990
FW08UT014
Utah
EPA-NRSA
37.258226
37.22371769
-109.310604
-109.2086935
Creek
UTR9-0901
EPA-NRSA
37.22371769
-109.2086935
SJBB
SJBB
EPA
37.25737015
-109.6185856
San Juan River near Bluff
N
A-4
-------
EPA Gold King Mine Biological Monitoring Report
Location
(GKMJD)
Associated Location(s)
Site Organization
Latitude
Longitude
Descri ption/Location
USGS
gage
available?
4953250
Utah
37.260279
-109.613734
San Juan River near Bluff - San Island
UTRM-1009
EPA-NRSA
37.25537255
-109.6217678
San Juan River near Bluff
SJMH
EPA
SJMH
4953000
09379500 (gage)
Utah
USGS
37.146948
-109.853672
San Juan River in Mexican Hat
Y
SJCH
SJCH
4952942
3.71248E+14
EPA
Utah
USGS
37.293336
37.293008
-110.399293
-110.399621
San Juan River / Lake Powell at Clay Hills
boat ramp
N
*Background/reference sites - data to be used to characterize background loading to Animas and San Juan unrelated to Gold King Mine Influence.
A-5
-------
EPA Gold King Mine Biological Monitoring Report
APPENDIX B: DATA SOURCES
Links to access biological data collected from the Animas and San Juan rivers. BMI = benthic macroinvertebrate.
Data Source
Information Obtained
EPA follow-up sampling
BMI assemblage (2015, 2016)
https: //www .epa. sov/eoldkingminc
BMI tissue (2016)
Fish tissue (2016, 2017)
Physical habitat (2016)
WQX
BMI assemblage
https: //www .epa. go v/wate rdata/w ate r-
• NMED (2010)
aualitv-data-wqx
Stations:
https://www.wateraualitvdata.us/Station/search?oreanization=21NMEX WOX&sam
pleMedia=Bioloeical&startDateLo=01-01-
2010&mimeTvpe=csv&zip=ves&sorted=no
Results:
https ://www.wateraualitvdata. us/Result/search?oreanization=21NMEX WOX&sam
a
u
pleMedia=Bioloaical&startDateLo=01-01-
-o
2010&mimeTvpe=csv&zip=ves&sorted=no
• Southern Ute Indian Tribe (2013, 2014)
Stations:
https://www.wateraualitvdata.us/Station/search?oreanization=SOUTHUTE&sample
Media=Biolosical&startDateLo=01-01 -2013 &startDateHi= 12-31-
2014&mimeTvpe=csv&zip=ves&sorted=no
Results:
https://www.wateraualitvdata.us/Result/search?oraanization=SOUTHUTE&sample
Media=Bioloaical&startDateLo=01-01 -2013 &startDateHi= 12-31-
2014&mimeTvpe=csv&zip=ves&sorted=no&dataProfile=bioloaical
• The Rivers of Colorado Water Watch Network (RiverWatch) (2012)
B-l
-------
EPA Gold King Mine Biological Monitoring Report
Data Source
Information Obtained
Stations:
https://www.wateraualitvdata.us/Station/search?oreanization=CORIVWCH WOX&
sampleMedia=Biolosical&startDateLo=01-01-2012&startDateHi= 12-31-
2012&mimeTvpe=csv&zip=ves&sorted=no
Results:
https://www.wateraualitvdata.us/Result/search?oraanization=CORIVWCH WOX&s
ampleMedia=Bioloaical&startDateLo=01 -01-2012&startDateHi= 12-31-
2012&mimeTvpe=csv&zip=ves&sorted=no&dataProfile=bioloaical
EPA Superfund SCRIBE database
Data are available through site contacts
identified on the Bonita Peak Superfund
website:
https: //cumuli s .epa. aov/supercpad/ cursites
/csitinfo.cfm?id=0802497
EPA collected/funded
• BMI assemblage (2014; 2015 post-GKM release)
• Metals BMI tissue data
• (2012, 2014; 2015 post-release)
BMI assemblage data
• SUIT (2008, 2009)
• ARSG (2010)
• AWP (2010)
US Fish and Wildlife
https://www.fws. eov/southwest/sirip/
San Juan River fish population data
(1991-2016)
Data were acquired through a request.
EPA National River and Streams
2009 data:
https://www.eDa. eov/national-aauatic-
resource-survevs/data-national-aauatic-
resource-survevs
2013 data:
Data available through a request
BMI assemblage (2009,2013)
Physical habitat (2009, 2013)
U.S. Bureau of Reclamation
Data were obtained from the pdf:
Animas-La Plata Project. Final
Supplement to the Final EIS. Appendix B.
April 1996
Metals in fish tissue (1996)
B-2
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EPA Gold King Mine Biological Monitoring Report
Data Source
Information Obtained
State
NM Environment Department
NM Department of Game and Fish
https://www.env.nm.eov/river-water-
safetv/animas-river-data-documents-
Daae/#wildlife
Metals in fish and BMI tissue
(August 2015, March 2016)
Colorado Parks and Wildlife
www. cd w. state. co. us
Data were acquired through a request.
Animas River fish population data near Durango and Silverton
(1912-2016)
GKM response sampling including fish population surveys, sentinel caged fish data, and
field datasheets.
Beaver necropsy report.
Colorado Department of Public Health
and Environment
BMI assemblage data were acquired
through a request.
Metals in fish tissue:
https: //www .Colorado. aov/pacific/cdphe/a
nimas-river-water-aualitv-sampline-and-
data
BMI assemblage (2008, 2014, 2016)
Metals in fish tissue (August 2015, March 2016)
Tribal
Southern Ute Indian Tribe
Data were acquired through a request.
Metals in fish tissue data (July 2015)
BMI assemblage (2015 pre- and post-GKM release, 2016)
Navajo Nation Environmental
Protection Agency
Data were presented in the final report
dated November 2017.
Metals in fish tissue data (June 2017)
-------
EPA Gold King Mine Biological Monitoring Report
Data Source
Information Obtained
NGO
Animas River Stakeholder Group
httD://animasrivcrstakcholdcrserouD.ore/b
loe/indcx. oho/data/
BMI assemblage
B-4
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EPA Gold King Mine Biological Monitoring Report
APPENDIX C: BENTHIC MACRO INVERTEBRATE ASSEMBLAGE
SUPPORTING INFORMATION
Table C.l . Benthic macroinvertebrate metric descriptions.
Metric Code
Metric Description
Taxa Composition
pEPTnoB
NonlnPct
ColeoPct
Percentages of taxa groups
% EPT excluding Baetidae of all individuals
% Non-Insect individuals of all individuals
% Coleoptera individuals of all individuals
Habit
ClngrTax
SprwITax
Mode of locomotion or attachment
Number of Clinger Taxa
Number of Sprawler Taxa
Pollution Tolerance
IntolTax
ptjntol
pi_DecrMtnTrn
piJncrMidElev
piJncrPlains
Sensitivity to stressors
Number of Intolerant Taxa
Intolerant taxa as a percentage of all taxa
% decreaser indicator individuals in Biotypes 1 and 2
% increaser indicator individuals in Biotypes 1
% increaser indicator individuals in Biotypes 3
Taxa Richness
TotalTax
pt_noninsect
EPTTax
Counts of taxa, percentage of taxa
Total number of taxa in the sample
Non-insect taxa as a percentage of all taxa
Number of EPT taxa in the sample
Functional Feeding Group Mechanism for obtaining food
PredPctFAC % Facultative Predator individuals of all individuals
ScrapPctFAC % Facultative Scraper individuals of all individuals
PredShrTaxFAC Number of Facultative Predator or Shredder Taxa
C-l
-------
EPA Gold King Mine Biological Monitoring Report
Table C.2 NRSA MMI median values, with median difference per site and Wilcoxon signed-rank.
Site
Pre-event Period
Median
Post-event Period
Median
Difference
Signed Rank
All
29.98
32.58
-2.60
-7
A73
41.53
40.15
1.38
6
A75D
42.59
37.80
4.79
10
Bakers Bridge
39.45
39.90
-0.45
-1
James Ranch
39.64
38.85
0.79
3
9426
23.20
41.32
-18.12
-16
32nd Street
51.00
47.50
3.50
9
Rotary Park
53.92
52.78
1.14
5
AR16-0
46.58
47.17
-0.59
-2
AR7-2
48.07
66.10
-18.03
-15
ADW-010
67.65
55.05
12.60
14
FW-040
58.00
63.13
-5.13
-11
SJAR
41.44
44.86
-3.42
-8
SJFP
45.04
52.65
-7.62
-12
SJMC
57.13
58.20
-1.07
-4
SJBB
49.43
59.32
-9.89
-13
C-2
-------
EPA Gold King Mine Biological Monitoring Report
Table C.3 Colorado MMI median values, with median difference per site and Wilcoxon signed-rank.
Site
Pre-event Period
Median
Post-event Period
Median
Difference
Signed Rank
All
16.80
17.90
-1.10
-3
A73
30.70
36.90
-6.20
-7
A75D
47.45
54.75
-7.30
-8
Bakers Bridge
47.60
62.55
-14.95
-11
James Ranch
48.45
49.00
-0.55
-1
9426
20.60
39.70
-19.10
-15
32nd Street
41.80
31.05
10.75
9
Rotary Park
39.90
38.70
1.20
4
AR16-0
26.10
44.22
-18.10
-14
AR7-2
49.10
67.00
-17.90
-13
ADW-010
85.40
68.30
17.10
12
FW-040
71.50
70.80
0.70
2
SJAR
44.20
45.80
-1.60
-6
SJFP
58.90
60.45
-1.55
-5
SJMC
77.30
56.80
20.50
16
SJBB
59.00
48.20
10.80
10
C-3
-------
EPA Gold King Mine Biological Monitoring Report
Table C.4 % EPT median values, with median difference per site and Wilcoxon signed-rank.
Site
Pre-event Period
Median
Post-event Period
Median
Difference
Signed Rank
All
55.86
76.33
-20.47
-13
A73
96.12
91.33
4.79
4
A75D
70.71
78.75
-8.04
-7
Bakers Bridge
77.48
68.12
-9.36
-10
James Ranch
74.67
81.33
-6.66
-6
9426
32.17
72.69
-40.52
-15
32nd Street
77.41
67.17
10.24
11
Rotary Park
73.00
64.00
9.00
8
AR16-0
74.00
76.33
-2.33
-3
AR7-2
85.67
62.67
23.00
14
ADW-010
30.53
75.33
-44.80
-16
FW-040
67.45
68.18
-0.73
-1
SJAR
54.67
45.59
9.08
9
SJFP
54.88
65.75
-10.87
-12
SJMC
46.81
45.77
1.04
2
SJBB
42.02
36.84
5.18
5
C-4
-------
EPA Gold King Mine Biological Monitoring Report
Table C.5 Total Taxa median values, with median difference per site and Wilcoxon signed-rank.
Site
Pre-event Period
Median
Post-event Period
Median
Difference
Signed Rank
All
8.0
9.0
-1.0
-1
A73
11.0
13.0
-2.0
-4
A75D
17.0
18.0
-1.0
-1
Bakers Bridge
16.0
24.5
-8.5
-13
James Ranch
12.0
17.5
-5.5
-11
9426
8.0
12.0
-4.0
-8
32nd Street
10.0
12.5
-2.5
-6
Rotary Park
9.0
20.0
-11.0
-14
AR16-0
9.0
13.0
-4.0
-8
AR7-2
9.0
22.0
-13.0
-16
ADW-010
21.0
20.0
1.0
1
FW-040
19.0
27.0
-8.0
-12
SJAR
23.0
20.5
2.5
6
SJFP
19.5
23.5
-4.0
-8
SJMC
29.0
17.0
12
15
SJBB
16.0
18.0
-2.0
-4
C-5
-------
EPA Gold King Mine Biological Monitoring Report
Upper Animas
60
50
40
30
20
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-------
EPA Gold King Mine Biological Monitoring Report
Middle Animas
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Pre-release
Post-release
Figure C.2 Relative abundance of Baetis spp. within the Middle Animas from pre- and post-release sampling events.
C-7
-------
EPA Gold King Mine Biological Monitoring Report
Lower Amimas
60
50
40
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10
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10/28/2015 8/24/2016
9/30/2016
8/24/2016 10/1/2016
8/24/2016 10/1/2016
8/27/2016 10/2/2016
8/27/2016 10/2/2016
ADW-022
ADW-021
ADW-010
FW-012
FW-040
Pre-release ¦ Post-release
Figure C.3. Relative abundance of Baetis spp. within the Lower Animas from pre- and post-release sampling events.
C-8
-------
EPA Gold King Mine Biological Monitoring Report
San Juan
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Upper Animas
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C-10
-------
EPA Gold King Mine Biological Monitoring Report
Middle Animas
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Figure C.6. Relative abundance of Heptageniidae within the Middle Animas from pre- and post-release sampling events.
C-ll
-------
EPA Gold King Mine Biological Monitoring Report
Lower Animas
10/28/2015 8/24/2016 9/30/2016
ADW-022
8/24/2016 10/1/2016
ADW-021
¦ Pre-release ¦ Post-release
8/24/2016 10/1/2016
ADW-010
8/27/2016 10/2/2016
FW-012
Figure C.7. Relative abundance of Heptageniidae within the Lower Animas from pre- and post-release sampling events.
C-12
-------
EPA Gold King Mine Biological Monitoring Report
San Juan
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Upper Aminas
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EPA Gold King Mine Biological Monitoring Report
Lower Animas
10/28/2015 8/24/2016
ADW-022
9/30/2016
I
8/24/2016 10/1/2016
ADW-021
¦ Pre-release ¦ Post-release
8/24/2016 10/1/2016
ADW-010
8/27/2016 10/2/2016
FW-012
Figure C.ll. Relative abundance of Ephemerellidae within the Lower Animas from pre- and post-release sampling events.
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EPA Gold King Mine Biological Monitoring Report
San Juan
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EPA Gold King Mine Biological Monitoring Report
Upper Animas
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EPA Gold King Mine Biological Monitoring Report
APPENDIX D: COLORADO PARKS AND WILDLIFE SENTINEL FISH
STUDY NOTES AND FISH STOCKING RECORDS
Table D.l Records for 96-hour sentinel fish study.
Location
Number of fish
Dates times checked, notes
mortality
8/6 19:26, all look good
0
8/7 6:21, all look good
0
8/7 13:27, less turbid than this am
0
8/7 19:00, look good
0
Junction
Creek
(Control site,
not affected
by GKM)
8/8 7:28, fish look good
0
8/8 12:35, fish look good
0
60 (5 cages/12
fish per cage)
8/8 20:00
8/9 7:12
8/9 12:49
8/9 19:00
8/10 8:22, all good
8/10 14:07, fish look good
8/10 18:48, fish look good
8/1111:20
oooooooo
8/6 19:15, all look good
0
8/7 6:35, all look good
0
8/7 13:46, less turbid than this am
0
8/7 18:48, fish look good
0
8/8 6:53, fish look good
0
8/8 12:24, fish look good
0
Animas River
36 (3 cages/12
8/8 20:18
0
at 32nd Street
fish per cage)
8/9 7:26
8/9 12:32, water looking more muddy than orange
8/9 18:43, water looking more muddy than orange
8/10 7:55, all good
8/10 13:46, fish look good
8/10 18:22, fish look good
8/1110:50
0
0
0
0
0
0
0
8/6 19:58, all look good
0
8/7 6:53, could not find 3c
0
8/7 14:20, less turbid than this am
0
8/7 19:18, look good
0
8/8 7:45, fish look good
0
8/8 13:15, fish look good
0
Animas River
at Hatchery
36 (3 cages/12
fish per cage)
8/8 19:45,1 stressed in 2c
8/9 8:02
8/9 13:01, water looking more muddy than orange
8/9 19:17, water looking more muddy than orange
8/10 8:33, all good
8/10 14:30, fish look good
8/10 19:00, good fright response in cage
8/1112:00
OOOOOOOO
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EPA Gold King Mine Biological Monitoring Report
Table D.l Records for 96-hour sentinel fish study.
Location
Number offish
Dates times checked, notes
mortality
8/6 19:41, all look good
0
8/7 7:17, all but 1 look good
1
8/7 15:02, less turbid than this am
0
8/7 19:38, all but 1 look good
0
8/8 8:00, fish look good
0
8/8 12:53, fish look good
0
Animas River
36 (3 cages/12
8/8 19:18, look good
0
at High Bridge
fish per cage)
8/9 8:28
0
8/9 13:40, water looking more muddy than orange
0
8/9 19:38, all good!
0
8/10 9:00, fish look good
0
8/10 14:50, fish look good
0
8/10 19:24, good fright response in cage
0
8/1112:35
1
Table D.2 Fish stocking records for Animas Reaches 1 and 2.
Date stocked
Reach
Species
number
Length (in)
8/10/2016
1
Brown trout
9,997
4.49
8/10/2016
2
Hofer x Harrison rainbow trout
9,079
3.09
8/10/2016
2
Brown trout
10,088
4.61
Total 2016
1+2
Brown
20,085
Total 2016
2
Rainbow
9,079
9/3/2015
1
Brown trout
14,052
3.55
8/5/2015
GKM release
7/28/2015
2
Hofer x Harrison X Snake R rainbow
1,500
10.44
7/21/2015
2
Brown trout
793
3.62
7/20/2015
1
Brown trout
11,835
3.93
7/20/2015
2
Brown trout
11,835
3.93
7/7/2015
2
Hofer x Snake R rainbow trout
1,000
10.19
Total 2015
1+2
Brown
38,515
Total 2015
2
Rainbow
25,000
8/12/2014
1
Hofer X Colo R rainbow trout
10,000
2.6
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EPA Gold King Mine Biological Monitoring Report
Table D.2 Fish stocking records for Animas Reaches 1 and 2.
Date stocked
Reach
Species
number
Length (in)
8/12/2014
2
Hofer X Colo R rainbow trout
10,000
2.6
7/31/2014
2
Bel-aire rainbow trout
380
10.57
7/18/2014
2
Hofer x Harrison rainbow trout
760
10.61
7/3/2014
2
Bel-aire rainbow trout
760
10.6
6/23/2014
1
Brown trout
10,003
3.15
6/23/2014
2
Brown trout
10,002
3.15
6/23/2014
2
Rainbow trout
25,686
3.98
Total 2014
1+2
Brown
20,005
Total 2014
1+2
Rainbow
47,586
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EPA Gold King Mine Biological Monitoring Report
APPENDIX E: METAL IN FISH TISSUE SUPPORTING INFORMATION
NMDGF Generalized Linear Model
To examine the simultaneous influence of factors that influence metal bioaccumulation, we applied a
generalized linear model (GLM) to the NMDFG data. The GLM is a flexible generalization of ordinary
linear regression that allows for categorical or continuous response variables that have error distribution
models other than a normal distribution. Analysis was performed using a GLM routine in the base R
package (R-3/3/2, R Core Team 2016). The GLM evaluates the relationship between independent
parameters and the response variable without relying on limiting assumptions of model error distributions.
For this investigation, the response variable was tissue concentration. The covariates included categorical
variables of site, sampling date, fish species and tissue type. Table E.l lists the covariates and the levels of
categorical variables. To perform the test with categorical variables, one level within each categorical
covariate must be designated as the "reference," meaning the influence at other levels of that covariate are
relative to the influence of the reference level. Gray-shaded cells in Table 8.3 indicate the reference level of
each categorical factor. Body length was also included as a continuous independent variable. A separate
model was constructed for each metal. Tissue concentrations were first logio transformed to reduce the
influence of large outliers in the data, especially in the liver (see Chapter 8).
Table E.l. Independent variables examined in the generalized linear model for metal concentrations in fish tissues
in the lower Animas and San Juan rivers collected in 2015 and 2016. The generalized linear model specifies a
reference within each parameter. The selected reference is highlighted by shading.
Site
Tissue
Collection Date
Species
Fish Length (mm)
Animas: ADW-022
(148 RKM)
Muscle
August 2015
Bluehead sucker
Continuous
Animas: ADW-010
(163 RKM)
Liver
March 2016
Brown trout
San Juan: SJLP
(196 RKM)
Flannelmouth sucker
San Juan: SJFP
(214 RKM)
Speckled dace
San Juan: SJAR
(Reference)
GLM model results are presented in Table E.2, which provides the model intercept, the coefficients for
each level of the categorical covariates, and the statistical significance (via cell color coding) of each factor
in contributing to tissue concentration. In this analysis, the importance of each factor is measured
independent of confounding relationships to other factors, so that the model coefficients truly represent the
isolated influence of that single factor on tissue concentrations. The units of the coefficients in Table 8.6
are logio (mg/kg), and cell shading denotes the significance of each term in the model. Blue-shaded cells
indicate significantly lower metal concentrations than the reference level of the factor, and yellow-shaded
cells indicate significantly higher metal concentrations than the reference level. The significance level for
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EPA Gold King Mine Biological Monitoring Report
shaded cells is p<0.05, but the raw output from R indicates various levels of significance to p<0.0001.
Many of the significance values were at p<0.001.
The coefficients in the table provide the independent contribution of each of the covariates to tissue
concentration. The GLM found that the aluminum concentration in fish collected in August 2015 (averaged
across sites, species, tissues, fish size) was 0.09 logio units greater than fish collected in March 2016 (Table
E.2). This difference was statistically significant. Brown trout had, on average, 0.934 logio units higher
copper concentrations than bluehead sucker. This value was statistically significant. The coefficients in the
table can be used to calculate an estimate of tissue concentration at any combination of site, date, tissue,
species and fish size. Starting with the intercept for a specific metal, add the coefficient of the selected level
(if that level is significantly different from the reference level) for each of the categorical covariates, and
then multiply fish length (mm) by its coefficient (if significant) and add that to the sum to attain the model
estimate of tissue concentration for that metal after converting to standard units from logio.
Generally, the GLM results suggest the same interpretations of the NMDFG data as indicated in the
analyses as discussed in Section 8.2. However, when accounting for multiple influential factors at once, the
statistical significance of some comparisons was lessened (e.g. the effect of location) while the significance
of others was enhanced (e.g. the effect of species for individual metals). GLM results presented in Table
E.2 are briefly summarized by factor.
Location. Fish collected at the two Animas River sites had significantly higher manganese concentrations
than the San Juan reference site. Fish collected on the Animas River at ADW-010 (163 RKM near Aztec,
NM) had statistically higher aluminum concentrations than the reference site. Other metals cadmium,
copper and lead also tended to be higher at this site (positive coefficient) but were not statistically
significant.
The two San Juan sampling sites below the confluence with the Animas River generally showed no
difference in metal concentrations relative to the San Juan reference site with the exception of mercury and
aluminum. Significantly higher mercury concentrations were found in fish collected at the San Juan
reference site relative to the other four sites (i.e., the entire mercury column within the Location factor is
blue). Significantly higher aluminum concentrations were found at kilometer 196, just downstream of the
confluence with the Animas River.
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EPA Gold King Mine Biological Monitoring Report
Table E.2. Generalized linear model results for metal concentrations in fish. Cell values are estimated model coefficients in logio concentrations in mg/kg.
Blue-shaded cells indicate a statistically significant model coefficient that is less than the reference level of the factor (given in parentheses in the gray
"Factor" heading). Yellow-shaded cells indicate a statistically significant model coefficient that is greater than the reference level of the factor. For the
continuous variate Total Length, blue-shaded cells indicate a significant negative relationship between body length and metal concentration, while yellow-
shaded cells represents a significant positive relationship between those variables.
Factor
Aluminum
Arsenic
Log10
Cadmium
Metal Concentrations (mg/kg)
Copper Lead Mercury
Manganese
Selenium
Intercept
1.12
-0.714
-2.29
0.09
-1.38
-1.26
1.29
-0.673
Location (SJ Reference)
River KM 148
0.091
-0.014
0.117
0.118
0.039
-0.786
0.315
-0.001
River KM 163
0.181
-0.008
0.128
0.069
0.076
-0.743
0.382
-0.042
River KM 196
0.108
-0.042
0.078
0.011
-0.038
-0.553
-0.041
-0.034
River KM 214
0.088
0.005
-0.122
0.106
-0.019
-0.557
0.006
0.142
Collection Date (March 2016)
August 2015
0.09
-0.022
0.314
0.014
0.309
-0.476
0.107
0.447
Tissue (Liver)
Muscle
-0.162
-0.238
-0.405
-1.07
-0.272
0.267
-1.023
-0.707
Species (Bluehead Sucker)
Brown Trout
-0.193
-0.387
0.271
0.934
-0.095
-0.228
-0.802
0.764
Flannel mouth Sucker
-0.102
-0.298
0.196
0.34
0.114
0.189
-0.209
0.28
Speckled Dace
-0.304
-0.246
0.476
0.549
0.081
0.583
0.248
0.911
Fish Size
Total Length (mm)
-0.0009
-0.0003
0.0013
0.001
-0.0002
0.0011
-0.0018
0.0007
Significantly less than reference parameter at pr < .05
Significantly more than reference parameter at pr < .05
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EPA Gold King Mine Biological Monitoring Report
Table E.3. Generalized linear model results for metal concentrations in fish evaluating species and environmental concentrations of metals. Cell values
are estimated model coefficients in logio concentrations in mg/kg. Blue-shaded cells indicate a statistically significant model coefficient that is less than
the reference level of the factor (given in parentheses in the gray "Factor" heading). Yellow-shaded cells indicate a statistically significant model
coefficient that is greater than the reference level of the factor. For the continuous variates of Total Length, and environmental concentrations, the blue-
shaded cells indicate a significant negative relationship between the variable and metal concentration, while yellow-shaded cells represent a significant
positive relationship between those variables.
Log10 Metal Concentrations (mg/kg)
Factor
Aluminum
Arsenic
Cadmium
Copper
Lead
Manganese
Selenium
Intercept
1.21
-0.856
-2.7
-1.15
-1.55
-0.4
-1.865
Tissue (Muscle)
Liver
0.146
0.247
0.411
1.097
0.256
1.043
0.748
Species (Bluehead Sucker)
Brown Trout
-0.26
-0.4
0.22
0.991
-0.121
-0.722
0.835
Flannel mouth Sucker
-0.104
-0.277
0.181
0.316
0.158
-0.228
0.29
Speckled Dace
-0.39
-0.195
0.439
0.712
-0.032
0.425
1.029
Fish Size
Total Length (mm)
-0.0011
-0.00016
0.001
0.0016
-0.0005
-0.0012
0.00094
Environmental Concentration
Water Concentration (ug/l)
0.00000114
-0.058
2.36
-0.0014
0.0067
-0.00054
0.736
Sediment Concentration (mg/kg)
0.000001
0.0033
0.0424
0.0011
0.0025
0.0019
0.179
Macrolnvert Concentration (ug/g)
-0.00066
-0.46
-0.269
0.009
-0.052
0.0038
-0.0087
Significantly less than reference parameter at p < .05
Significantly more than reference parameter at p < .05
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EPA Gold King Mine Biological Monitoring Report
Collection Date. For most metals tested, August 2015 concentrations after the GKM release were
significantly greater than observed in March 2016. Mercury, however, was lower in August than March.
Tissue. For all metals except mercury, significantly greater metal concentrations were found in liver
samples relative to muscle tissue. Most metals bind readily to compounds found in the liver
(metallothioneins), while mercury also binds to thiols/sulfhydryls commonly found in muscle tissue.
Higher concentrations of metals in liver than muscle tissues are well supported in scientific literature.
Species: A mixture of results were seen for this factor, as would be expected based on the variability in
tissue concentrations displayed by species in Figures 8.7, 8.8 and 8.9. The bluehead suckers had
significantly higher concentrations of aluminum and arsenic than the other species, but significantly lower
concentrations of cadmium, copper and selenium. Speckled dace showed the highest concentrations of
manganese, selenium, mercury and cadmium; Brown trout had the highest concentrations of copper;
Flannelmouth sucker had the highest concentrations of lead.
Fish Size. Metal concentrations increased with fish size for cadmium, copper, mercury and selenium, and
decreased with fish size for aluminum and manganese.
We ran a second GLM model on the NMDGF data to evaluate the direct relationship of environmental
variables and eliminated the categorical variables of location and date that reflected the sampling design.
Across the sampling dates and locations, there was a range of water and sediment concentrations reflected
in the sampling that allowed direct analysis of the effect of environmental metal concentrations on fish
tissue concentrations (e.g. e.g. Figures 8.4 and 8.5). The range of environmental metal concentrations
within the NMDGF data was much narrower than the Animas River as a whole, but concentrations varied
sufficiently to detect their influence on fish tissue concentrations. The concentration of metals averaged for
all macroinvertebrates at each sampling location was included as an indicator of potential dietary exposure.
The environmental conditions at the sites are provided in Figure 8.5 and macroinvertebrate concentrations
are discussed in Chapter 7. Tissue type and species were included as variables in the environmental
concentration oriented model because of their importance in determining response to metals within the
entire fish community.
The regression coefficients and their statistical significance are provided in Table 8.5. There were some
statistically strong relationships between fish tissue concentrations and environmental concentrations of
some metals, but there were no general relationships between the accumulation of metals in fish and the
concentrations of metals in sediment, water, or macroinvertebrates. The variability in metal accumulation
between species and among individual fish within these populations was a stronger influence than the
pervasive environmental concentrations.
E-5
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