Click here to read the report. Here’s the 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 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).
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.
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 contributed to the concentration change. Likely explanations include differences in sample collection methodologies between years and taxonomic 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.
From The Durango Herald (Jonathan Romeo):
The EPA last week released a “Biological Response Report” that shows the agency’s analysis of the Gold King Mine spill…
Based on data from before and after the spill, the EPA “concluded there was no measurable changes to fish populations and bottom-dwelling organisms” after the Gold King Mine blowout.
The EPA said aquatic life in the river near Silverton had already been killed off from decades of legacy contamination from historic mine ore processing and ongoing acid mine drainage contamination.
In Durango, where aquatic life does exist, populations were not affected because the spill had been diluted, the metals were not toxic and the time of exposure was relatively short, the EPA said.
The EPA said that while some fish accumulated metals after the mine release, water quality returned to normal when samples were taken the next spring.
The study highlights what many researchers in the watershed have known for some time: The Gold King Mine spill’s tangible effect on the environment has been relatively small.
Just days after the Aug. 5, 2015, spill, Colorado Parks and Wildlife placed more than 100 hatchery fish along the Animas River. None of the fish died.
In August, San Juan Basin Public Health released the results of a three-year water-quality study, also finding the Gold King Mine spill had no lasting impacts.
Mountain Studies Institute, which has extensively monitored the river since the spill, has long maintained aquatic life had not been seriously affected. Recently, the group released a study that showed the 416 Fire runoff was by far more impactful.