Biological Response to the Gold King Mine Release in the Animas and San Juan Rivers

Transcription

1 Biological Response to the Gold King Mine Release in the and San Juan Rivers Lareina Guenzel 1, Richard Mitchell, PhD 1, Kate Sullivan, PhD 2, and Michael Cyterski, PhD 2 1 U.S. Environmental Protection Agency, Office of Wetlands, Oceans and Watersheds 2 U.S. Environmental Protection Agency, Office of Research and Development 3rd Annual Conference on Environmental Conditions of the and San Juan Watersheds 6/21/2018 1

2 Presentation Overview Background Study objectives and methods Benthic macroinvertebrate response Sentinel studies Metal concentrations in benthic tissue Population assessment Fish response Sentinel studies Metal concentrations in fish tissue Population assessment Questions 2

3 Background The Gold King Mine (GKM) release deposited metals along the and San Juan rivers for varying periods of time until the system was cleared by stormflow and snowmelt runoff by May 2016 Aquatic biota take up and excrete metals Heavy metals can be toxic to aquatic biota and terrestrial wildlife and humans which consume them - Acute and chronic effects Legacy mining impacts: highly contaminated surface water and sediment, and known biological impairments in Upper (USGS 2007, EPA 2015) Lower and San Juan Rivers were not known to be contaminated by historic mining in the headwaters before the GKM release. San Juan River is managed for the recovery of listed fish species due to basin-wide water development projects. Upper Historic Conditions: Extremely low trout populations upstream of Baker s Bridge Limited Benthic Macroinvertebrates No aquatic life use protection in the mainstem through Silverton 3

4 Study Questions and Methods Study Questions Did the GKM add to biological impairment in the already-contaminated upper River? Did the GKM release cause biological impairment in other segments of the and San Juan rivers that had not been known to have metal impacts? Methods Collected and reviewed all available biological data in the San Juan and rivers to assess how aquatic biota responded to the GKM release Compared pre-event and post-event measures of four key characteristics Organism body burden to indicate uptake of GKM metals Community structure and population estimates to indicate mortality from exposure to GKM metals Benthic Macroinvertebrates X X Fish X X 4

5 Study Area Longitudinal Patterns in Aquatic Habitat Upper High gradient Cold water aquatic life Large particle substrate size Lower Gradient transition from high to low Transition from cold water to warm water fishery Substrate particle size becomes smaller San Juan River Low gradient Warm water fishery Small particle substrate size Lower San Juan Upper Mid Lower Upper San Juan 5

6 Longitudinal Gradient of Metals Contamination Metals persistently exceed water quality criteria to support aquatic life in the headwaters Metals contamination from the mining district is known to impair fish and macroinvertebrate communities 6

7 Biological Data Sources Primary Data Sources Source EPA: START Contractors EPA: Superfund/ Mountain Studies Institute (MSI) CO Parks and Wildlife (CPW) US Fish and Wildlife Service (USFWS) NM Department of Game &Fish (NMDGF) Southern Ute Indian Tribe (SUIT) CO Department of Environmental Quality (CDEQ) Post Pre&Post Pre&Post Pre&Post Post Benthic Macro Assemblage & San Juan (upper & mid) Benthic Macro Tissue & San Juan (upper & mid) (lower) San Juan (upper) Fish Population (Upper and Mid) San Juan Fish Tissue & San Juan (lower) San Juan (upper) Pre&Post (Mid) (Mid) Pre&Post (Mid) Physical Habitat & San Juan EPA: NRSA Pre San Juan San Juan Navajo Nation EPA (NNEPA) Post San Juan NM Environment Department (NMED) Pre San Juan Bureau of Reclamation Pre San Juan (1996) 7

8 Aquatic Life Exposure to Metals During the GKM plume Aquatic Acute Below Silverton (RK 16.4) Bakers Bridge (RK 64) River Durango (RK 94) Hours At or Above Criteria During Passage of GKM Plume NAR06 (RK 132) Aztec (RK 164) Farmington (RK 190) Farmington (RK 196) Shiprock (RK 246) San Juan River Four Corners (RK 296) Bluff (RK 377) Mexican Hat (RK 421) Aluminum Antimony Arsenic Barium Beryllium Cadmium Chromium Cobalt Copper Iron Lead Manganese Molybdenum Nickel Selenium Silver Thallium Vanadium Zinc Criteria Used: CO CO CO CO NM NM NM NM UT UT UT Navajo Nation Ute Mountain Ute Tribe A few metals approached acute WQ criteria briefly in Durango ZINC Short-duration exposure exceeded water quality criteria for some metals, primarily in the upper (hours) Aluminum exceeded more widely No evidence of wide-spread fish kills 8

9 Sentinel CPW Fish Studies Toxicity: caged trout fry (8/6-10/2015) 1.5 inch rainbow trout fry placed in cages at three sites in the River for four-days Of the 108 deployed fish, 2 mortalities were attributed to handling Small fish survey (9/2015) Mottled sculpin are sensitive to metals, especially zinc Young trout are more sensitive than adults N = number of surveys 9

10 Sentinel Macroinvertebrates EPA/MSI Benthic Macroinvertebrates Mountain Studies Institute sampled macroinvertebrate communities before and after the GKM plume Found no decline in species or relative abundance 10

11 Months After the GKM Event Aquatic studies were conducted in the weeks following the GKM release to determine whether fish consumption advisories were needed - Colorado Parks and Wildlife; Durango area - New Mexico Game and Fish; lower and upper San Juan Sampled in August 2015 and again before the onset of snowmelt runoff in 2016 Sampled tissue for metals body burden Fish (muscle and liver) Macroinvertebrates (NM) sites had significant deposits of GKM release material in the river channel during the August sampling Deposits resulted in measurably elevated metals in sediment during August sampling, at background in March 11

12 Benthic Macroinvertebrate Tissue Metals in benthic macroinvertebrate tissue track the longitudinal patterns in sediment and water concentrations In the Lower, elevated concentrations of some metals were observed immediately post-release Concentrations returned to background by spring 2016 Differences in field collection and analytical methods by various entities limit comparative data analyses 12

13 Metals in Fish: New Mexico Fish Data Fish took up metals in the weeks immediately after the GKM event Note log scale Uptake was very complex at the individual level Liver tissue had higher concentrations than muscle Some individuals had very high concentrations while most were at non-detect levels Some species were more responsive to individual metals than others Unknown whether there was any fish mortality due to this exposure 13

14 Metals in Fish: New Mexico Fish Data Average metals concentrations in fish followed the longitudinal pattern of GKM deposition in the River Metals in fish were at background in the during March 2016 sampling There was little change in water and sediments in the San Juan River after the release and this was reflected in the low metals concentrations in both samplings of macroinvertebrate and fish communities Muscle concentration did not exceed advisory consumption concentrations. 14

15 Return to Background Conditions After GKM Body burdens of 8 metals from SUIT and EPA data taken at the same locations in Fall 2016 were very similar to pre-event samples EPA s monitoring data supports the conclusion that biological conditions were at background by Fall 2016 The NMDGF spring data taken 30 km downstream were also very similar to the SUIT and EPA data for most details 15

16 Benthic Macroinvertebrate Assemblage Multi-metric index scores based on macroinvertebrate communities Upper River Substantial pre-existing degradation pre-gkm release No difference in community indices immediately after the event No difference in indices a year+ after the event Lower and San Juan Rivers Moderate to no degradation pre-gkm release No difference in community indices a year+ after the event 16

17 River Fish Populations Durango-Area CPW Adult Fish Survey Results Much year-to-year variability in numbers caught Native, naturally reproducing fish abundance (sculpin, suckers) in 2015/2016 falls within historic data ranges Stocked trout populations (rainbow, brown) showed above-average population abundance in post-gkm 2015 survey Bluehead Sucker length-frequency data from 2016 show absence of fish < 200mm; however, these are typically < 5% of total fish caught 17

18 San Juan River Fish Populations: US Fish and Wildlife Survey Results Primary Findings Abundance of Speckled Dace, Bluehead Sucker and Flannelmouth Sucker in 2015/2016 generally falls within historic ranges, except in the mid-san Juan Rising abundance of native endangered species under managed recovery plans (Razorback Sucker and Colorado Pikeminnow) 18

19 Summary by Location Upper River Historic mining activities in the headwaters have contaminated water and sediments with high concentrations of heavy metals and impacted aquatic life for decades Although the upper River experienced the most exceedances of aquatic life criteria and the GKM release left behind deposits that persisted for 8 months after the release, this did not have significant effects on the already-impacted aquatic community that has not historically supported fish Middle and Lower River Moving away from the historic mining operations, macroinvertebrate and fish assemblages expand in the middle River Some fish accumulated metals immediately after the GKM event, however fish survey data for naturally reproducing populations in the middle show that longer-term chronic effects have not been observed Changes in the aquatic community structure were not observed The Colorado Parks and Wildlife determined that the spill did not cause short term acute effects (fish mortality) as the plume passed through the Durango, CO section of the river San Juan River Concentrations of metals are generally much lower and showed little response to the GKM release Metals that could be attributed to the GKM Release were not observed in fish or macroinvertebrates in the San Juan River No effect on fish or macroinvertebrate community composition or populations within the San Juan River were detected due to the GKM release. 19