GROUNDWATER LEVEL MONITORING along the Animas River, New Mexico, after the Gold King Mine 2015 mine-water release

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1 GROUNDWATER LEVEL MONITORING along the Animas River, New Mexico, after the Gold King Mine 2015 mine-water release Ethan Mamer Talon Newton Stacy Timmons NM Bureau of Geology and Mineral Resources A Division of NM Tech With funding from NM Environment Department

2 August 5, 2015 ~3 million gallons of minewaste water, and 540 tons of mine-waste sediment were released into the Animas near Silverton, CO Gold King Mine Spill Figure from EPA, 2017

3 Gold King Mine Spill Dissolved contaminants flowed past Farmington within a week of the spill Contaminated sediments were deposited and left behind Figure from EPA, 2017

4 EPA findings (2017) Gold King Mine Spill 90% of sediments were deposited along the Animas River upstream of Farmington after spill Remaining sediments were transported out of the system during 2015 fall storms and 2016 snow melt Figure from EPA, 2017

5 Study Area Goals: Evaluate groundwater-surface water interaction Describe annual and seasonal fluctuations Determine any at risk locations along the river

6 Groundwater Monitoring Network: Between 59 and 74 wells measured during each seasonal transition. USGS WL steel tape protocol 8 measurement periods August 15 June 17 ~ 640 WL measurements Manual measurements

7 Animas River stage: Manual measurement periods Network measured 4 times a year Measurement timing intended to capture hydraulically significant periods in the groundwater/ surface water system Winter Baseflow in river (late January) Pre-irrigation season (late March) Peak river flow (early June) End of irrigation season (October)

8 Groundwater Monitoring Network: Continuous data loggers 24 wells instrumented with pressure transducers 2 installed September 15 2 installed January 16 1 installed in June installed late 16/ early 17 Monitor water levels and temperature every hour 13 also monitor the specific conductance 5 barometer loggers installed along Animas reach for barometric corrections

9 Summer Low June High Winter High October High Little can be determined from manual measurements alone

10 Summer Low June High Winter High October High Combining pressure transducer record with manual measurements we can extrapolate trends to wells without complete records

11 River Stage Controlled (22 of 70) Very close to river: median 320 ft Median water table is 9.4 ft bgs Small seasonal fluctuation: median 3.5 ft Water levels are hydraulically linked to the river and closely follow the fluctuations in stage

12 Irrigation controlled (38 of 70) Much farther from river: median 1,810 ft Deeper water table: median 14.7 ft Large seasonal fluctuation: median 5.7 ft Aquifer is recharged during the irrigation season, during which water levels recover, before dropping when ditches are shut off

13 Winter-recharge/ Summer evapotranspiration (10 of 70) Farther from river: median 1,160 ft Small seasonal fluctuation: median 2.1 ft Very shallow WT: median 2.5ft Summer decline is related to vegetation drawing from the aquifer

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15 Gaining stream Water table is HIGHER than the river, and water flows into the river from the surrounding aquifer. Losing stream Water table is LOWER than the river, and water infiltrates into the aquifer from the river.

16 Reaches where water table gradient has been found to be flat or slightly losing during winter.

17 Water table in October

18 Water table in March

19 How close is too close? Using the water table maps to calculate the gradient in losing reaches Approximating the conductivity of the alluvial aquifer and its porosity We can calculate the distance river water can travel during the winter. ~2 feet/day ~130ft in 9 weeks

20 Still a GAINING RIVER overall During Winter, when no water is being diverted into the Ditches, water is moving from the alluvial aquifer into the river.

21 Most of Animas River has gaining conditions. Seasonal fluctuations in river stage and water levels are enough to reverse groundwater/ surface water flow direction. Potential for future contamination from lingering sediments, and reversals in groundwater flow The river and the groundwater in the valley are hydrologically connected. The irrigation ditch water is feeding the shallow water table, recharging groundwater during the irrigation season. Potential pathway for contamination to enter aquifer

22 Acknowledgments Very kind landowners NM Environment Department - Dennis McQuillan, Diane Agnew, Patrick Longmire, Kris Pintado U.S. EPA Funding to NMED USGS - Jesse Driscoll, Lauren Sherson, Nicole Thomas, Amy Gallanter NMOSE Doug Rappuhn, Rob Pine, Shawn Williams NMBGMR/NMT - Trevor Kludt, Scott Christenson, Kitty Pokorny, Brigitte Felix, Sara Chudnoff, Bonnie Frey, Dustin Baca, Geoff Rawling, Mark Mansell, Kylian Robinson NM Bureau of Geology and Mineral Resources NM Bureau of Geology and Mineral Resources