Water Quality in the Animas and San Juan Rivers Post Gold King Release Updated with 2017 Water Sampling

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1 Water Quality in the Animas and San Juan Rivers Post Gold King Release Updated with 2017 Water Sampling Kate Sullivan, Mike Cyterski Office of Research and Development National Exposure Research Laboratory US Environmental Protection Agency

2 Introduction The breach at the Gold King Mine released 3 million gallons of acidic water laden with 490,000 kg (444 tons) of heavy metals into the headwaters of the Animas and San Juan EPA s Fate and Transport study (2016) utilized thousands of water and sediment chemistry samples collected before, during and after the GKM release to estimate the concentrations and mass of metals released and their pathway through the Animas and San Juan Rivers

3 The challenge was to track the GKM release over the short and long-term against a backdrop of strong gradients of existing metals in water and sediment Map: USGS Mineral Resources On- Line Spatial Data tin.er.usgs.gov/soilgeochemistry Metals in stream sediments Metals in soils USGS Soil Chemistry Map--Lead

4 Metals in soils USGS Soil Chemistry Map--Lead Metals in Water Geology and historic mining govern metals in water in the upper Animas Sediments carried during high flows control metals in water in the lower Animas and San Juan

5 Introduction Tracking GKM release mass through the Animas and San Juan Rivers was assisted by Empirical analysis and physics-based computer modeling Signature technique that could identify GKM metals within background metals in samples The Fate and Transport study (EPA 2016) concluded that: 95% of the released metals were deposited in the rivers and remained for various lengths of time The lower Animas and San Juan were cleansed of deposits by fall 2015 monsoonal storms The upper Animas was cleansed during snowmelt 2016 Rivers were clear of GKM metals by June 2016 after the snowmelt season EPA repeated sampling during 2017 snowmelt to test that conclusion

6 Developed a signature technique that helped identify GKM release metals within background concentrations Concentration (ug/l) Aluminum Concentration (mg/l) 1, San Juan River--August 8-11, 2015 RK 196 to 421 Aluminum Dark circles closest to GKM plume y = 0.026x R² = ,000 4,000 6,000 8,000 10,000 Suspended Solids Concentration (mg/l) Lead in Relation to Aluminum in San Juan River Post Near GKM Peak Historic Example TOTAL LEAD Pb:Al Ratio Trace Metal Concentration Aluminum Concentration TTTTTTTTTT CCCCCCCCCCCCCCCCCCCCCCCCCC AAAAAAAAAAAAAAAA CCCCCCCCCCCCCCCCCCCCCCCCCC As sediment load increases, all metals increase in proportion to their concentration in soils The ratio of trace metals to aluminum is an index of sediment mass and should remain constant = Trace Metal Ratio San Juan at Bluff (RK 377 to 378) Pb:Al Ratio Expected level ,000 10, ,000 1,000,000 Aluminum Concentration (ug/l)

7 Signature Ratio Summarized Longitudinally During and After the GKM Plume The Pb:Al signal was present in water and sediments, diminishing with distance from GKM BACKGROUND A longitudinal gradient is present but smaller in background conditions, reaching minimums in the Animas near the CO/NM border The GKM plume ratio reflected the mine waste pile eroded outside the mine not the GKM effluent

8 Upper Animas River GKM Deposits from Silverton to Durango At the start of snowmelt in 2016, most of the GKM release mass remained in deposits distributed between Silverton and Durango ~ 80 km, 50 miles 90% of the original mass 411,000 kg 370 short tons This material would have to work its way through the entire river system

9 Snowmelt 2016: the Trace:Aluminum Ratio told us when GKM metals were on the move San Juan River Lead We could compute the mass of metals carried when the ratio was elevated to estimate GKM metals transported past location Copper Metals Mass (kg) 700, , , , , , ,000 0 Gold King Release Metals Mass 490,000 GKM Release 535,000 49,000 24,000 Total Deliery 608,000 kg Delivered to Lake Powell 2016 Snowmelt 40 days Fall Storm day GKM Plume 1-day Data are plotted sequentially in order PLOTS COMPRESS TIME During the snowmelt period, more than 13 million kg of metals moved past this location

10 EPA sampled during Snowmelt 2017 update status of WQ Examine snowmelt 2017 data in context of historic and post GKM data Any evidence of GKM release? Briefly review the annual cycle of metals from the Animas headwaters to downstream areas Update GKM Release findings

11 San Juan River Snowmelt Metal Concentrations 2017 San Juan at Four Corners RK 296 Copper Ratio Cu:Al Total Copper Concentration (mg/l) No Data Ratio Cu:Al Navajo Dam Release Peak from Animas Metals concentrations were low in 2017 Each year during snowmelt runoff metals concentrations peak twice San Juan at Four Corners RK 296 Lead Ratio Pb:Al Total Lead Concentration (mg/l) No Data Ratio Pb:Al

12 San Juan River 2017 Trace Metal : Aluminum Ratio The signature trace metal to Al ratios were low in 2017 indicating no GKM metals Trace:Al ratios increase in the San Juan each year as the Animas snowmelt peak travels through Peak snowmelt appears to be the primary time when the Animas headwaters influence the San Juan

13 Upper Animas River -- Long Term Water Quality Snowmelt only for 2016 and 2017 There is a long record of metals concentrations in the upper Animas Metals concentrations were significantly elevated during 2016 snowmelt in Durango Historically low concentrations of many metals in 2017

14 We estimate the mass of metals moving in the Animas each year 1) Build one estimate by interpolating between observed concentrations 2) Build one estimate based on flow and regressions: Concentration = f (flow) The mass moved each year is strongly related to peak snowmelt flow when most of mass is transported Most metal concentrations increase at high flow as particulates are mobilized Some regressions are strong, some are weak

15 Typical pattern of metals concentration during spring snowmelt Summed Metals Concentration (mg/l) Cement Creek During Snowmelt 50 Ave /1 3/15 3/29 4/12 4/26 5/10 5/24 6/7 6/21 7/5 Blue shaded area on each figure is the standard error of the estimated concentration on that day

16 More in-depth analysis of the historical data from the Upper Animas River improved estimates of GKM metals movement during snowmelt 2016 GKM metals movement in upper Animas confirmed by Pb:Al ratio An additional 102,000 kg of particulate metal mass from GKM release was delivered to the Animas from Cement Creek Transported with 300,000 kg of background metals from Cement Added this mass to the original deposit estimates

17 Revised Summary of GKM Release Mass and Delivery Gold King Release Metals Mass Metals Mass (kg) 700, , , , , , , ,000 GKM Release 2016 from Cement Cr (102,000) 535,000 49,000 24,000 Total Deliery 608,000 kg Delivered to Lake Powell 2016 Snowmelt 40 days Fall Storm day GKM Plume 1-day Total GKM Release delivery revised to 608,000 kg (550 short tons) with additional 102,000 kg (93 short tons) from Cement Creek Water quality indicators in 2017 confirm that there were no more GKM metals transported in the rivers in 2016

18 History of Dissolved Metals Animas below Silverton In 2017, most dissolved and total metals were at very low levels relative to the preceding 15 years 2016 and 2017 peak snowmelt flow were above average

19 History of Dissolved Metals Animas at Durango In 2017, most dissolved and total metals were at very low levels relative to the preceding 15 years 2016 and 2017 peak snowmelt flow were above average

20 Improvement can be at least partially explained by remediation efforts First 9 months of operation Photo by Grace Hood/CPR News Treatment plant started treating water from Gold King Mine adit in October 2015 Facility has achieved 85 to 95% removal efficiency Removed ~ 164,000 kg metals in the 1 st year of operation ~150 short tons

21 Remediation Effectiveness The treatment facility removes a surprisingly high portion of stream metals load On a daily basis: 10-60% from Cement Creek 3-30% at Animas below Silverton On a seasonal basis: Example AMD treatment pond

22 Summary The Gold King Mine Release impacted water and sediment concentrations primarily in the first month after the release. Most of the released metals were deposited, awaiting removal during subsequent high flow events. Our earlier report found that all remaining Gold King release deposits were flushed from the upper Animas and transported to Lake Powell during the 2016 snowmelt period from March to June. Follow-up monitoring in 2017 snowmelt confirmed that there were no indicators of GKM metals in the rivers Metals concentrations were exceptionally low in the upper Animas River through Durango in 2017 compared to the previous 15 years and were low in the San Juan Removal of metals from GKM effluent at the treatment facility in Cement Creek since Fall 2015 partially explains improvements in the upper Animas

23 In 2016, the U.S. Congress authorized appropriations for a long-term water quality monitoring program for the San Juan watershed States, Tribes and EPA will soon be launching a watershed-wide monitoring plan along with various related projects For more information, visit