Historical Mining and Water Quality in the Upper Animas Basin Peter Butler, Ph.D. August 23, 2017

Silverton and the Volcano

Early Mining Mining Began around Silverton in 1870’s Downstream Towns Founded as Supply Towns Narrow Gauge Railway 1882 Mining Heyday – late 1890’s thru 1910

Downstream Impacts Pollution Generated in Durango Mill Tailings Dumped in the River Durango Switched to Florida River For Water Supply in 1902.

Early 1930’s Many Mines Shut Down Permanently Although Some Reopened During WWII Mining Companies began Use of Tailings Ponds

Mining in 1950’s and Beyond Very Little Mining through Most of the 1950’s. The Old Gold King Tunnel (aka the American Tunnel) Was Extended Over a Mile Underneath Lake Emma and the Sunnyside Mine in late 1950’s, early 1960’s. Sunnyside Mine Shut Down in 1991 and Mining Ceased.

Water Quality Issues – 1970’s and 1980’s. Clean Water Act Passed in 1972. Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) Passed in 1980. Colo. Starts to Require Reclamation Plans and Bonds in Mid 1970’s. Sunnyside Installs Treatment at American Tunnel in Late 1970’s, Upgraded in Early 1980’s.

Water Quality Issues – 1970’s and 1980’s. Tailings Pond Failure in 1974. Lake Emma Collapse in 1978.

1990’s – Remediation Begins Animas River Stakeholders Group (ARSG) Started by CDPHE in 1994. WQCC Holds Hearing in Silverton in 1994. Dept. of Interior Begins Abandoned Mine Land Initiative in 1997 Sunnyside Gold Corp. and CDPHE Sign Consent Decree in 1995

Study and Evaluation Almost 200 Draining Mines Are Sampled and Prioritized for Remediation. Almost 200 Mine Waste Piles Are Sampled and Prioritized for Remediation. 33 Draining Mines and 32 Waste Piles Account for 90% of the Mining-Related Metal Loading ARSG Proposes (and WQCC Adopts) Water Quality Standards Based on Remediating Top Sites

Acid Mine Drainage

Mine Waste Acid Rock Drainage (Prospect Gulch)

Remediation and Water Quality About 60 Mine Remediation Projects Have Been Completed Ranging from $10,000 - $2 Million. Water Quality in Early 2000’s Was Probably the Best in 100 Years. Fish and Macroinvertebrate Studies Support Water Quality Data.

Koehler Tunnel Before After

Infiltration Control Project Before Pride of West Stope Infiltration Control Project Stream Avalanche Path Constructing Finished

Koehler Bulkhead

Water Quality Worsens By Mid 2000’s, Water Quality and Correspondingly Fish and Macros Became Much Worse Directly Below Silverton. All Water Quality Stds. Continue to Be Met at Trimble Lane. Issues Arise with Previously Permitted Sites.

Other Important Points After Bulkheads but before the Gold King Release, Four Portals (Gold King, American Tunnel, Red & Bonita and Mogul) Had the Approximate Metal Load (lbs/Day) of all the Other Draining Mines (~180) in the Basin. Before the Release, the Gold King Flow Was around 60 -250 gpm. Afterwards about 500-600 gpm which is being treated.

Other Important Points Water Quality Meets All Quality Standards for the past 25 Years (Except for the Secondary Manganese Drinking Water Standard) at Trimble Lane. Water Quality Has Improved over the Last Five Years Compared to Five Years to Ten Years Ago.

Superfund Designation Many of the 46 Sites Identified in the Superfund District Came From ARSG’s List Plus the Main Gladstone Mines. There are Two Study Areas – The Sunnyside Mine Pool and Prospect Gulch. Only 19 Sites Were Given a Hazardous Ranking Score.