Presented by

Tom Rutkowski

Golder Associates, Inc.

Passive Treatment of Mining Influenced Wastewater at the Standard Mine Superfund Site, Crested Butte, Colorado, USA

Project Overview

Test Methods

Results

Discussion

Conclusions

Presentation Overview

US Environmental Protection Agency (EPA) Standard Mine Superfund Site • Approximately three miles west of Crested Butte, Colorado • Elevation of 3,350 meters (11,000 feet) • Annual snowfall 10.2 – 17.8 meters (400 – 700 inches)

Inactive Hard Rock Mine • Lead, zinc, silver, gold mined from 1874 – 1966

Adit Level 1 Discharges to Elk Creek • Influences Coal Creek, Crested Butte water supply • COC’s cadmium, copper, iron, lead, and zinc

Project Overview

Passive Treatment Pilot Study : • Pilot Biochemical Reactor (BCR) constructed in 2007 (1 gallon per minute, 30 hour HRT) • Aerobic polishing cell (APC) constructed in 2008 • System decommissioned in 2012

Project Goals: Achieve stringent effluent standards • Test passive treatment performance at high alpine remote site • Monitor the system year-round with remote monitoring equipment

Project Overview

Standard Mine Passive System Profile

Project Overview

Standard Mine Passive System Plan

Project Overview

Project Overview

Level 1 adit

Sampling shed BCR APC

Project Overview

BCR media includes: hay wood chips sawdust limestone

BCR Microbial Community

Seyler et al. 2003

Passive Treatment Chemistry 101 SO4

-2 + 2 CH2O HS- + 2HCO3- + H+

(Sulfate reduction by bacteria) Zn+2 + HS- ZnS (s) + H+

(Sulfide precipitation)

Fe+3 + 3 H2O Fe(OH)3 (s) + 3 H+ (Hydroxide precipitation)

H+ + CaCO3 Ca+2

+ HCO3-

(Limestone dissolution)

REDUCING/ ANAEROBIC CONDITIONS

OXIDIZING CONDITIONS

ALL CONDITIONS

• Metal loading rate • Acidity loading rate

• Hydraulic retention time

Design Criteria

Remote Monitoring • Autosamplers • Sondes (pH, temperature, ORP) • Daily Satellite data transmission • Site power provided by photovoltaic array system

Sampling Events • Weekly to monthly analytical grab samples (BCR influent, effluent) • Metals/dissolved metals, calcium, sulfate/sulfide, nitrate-nitrite and ammonia

Test Methods

Data Presented Taken August 2008 – October 2011

Results

Autosampler and pump control panels

Autosamplers

Satellite transmission equipment

pH

Results

pH (su) All Data April - June

BCR Influent 6.2 3.9

BCR Effluent 6.7 -

2009 Freshet 2010 Freshet 2011 Freshet

Temperature • Average winter air temperature -9°C

Results

Temperature °C (°F) All Data Summer Winter

BCR Influent 3.4 (38.1) 4.0 (39.2) 2.9 (37.2)

BCR Effluent 3.2 (37.8) 4.0 (39.2) 2.6 (36.7)

ORP and DO

Results

BCR Influent BCR Effluent APC Effluent

Average ORP (mV) 117 -252 17.7

Average DO (mg/L) 9.2 2.0 6.1

Metals • COC results compared to estimated Colorado in-stream hardness based aquatic

standards for Elk Creek

Results

Parameter Acute Standard Chronic Standard Adit Discharge

Cd, dissolved (µg/L) 1.2 0.31 0.13

Cu, dissolved (µg/L) 9.0 6.2 0.21

Fe, total (µg/L) (water supply) NL 300 9,100 Fe, total (µg/L)

NL 1,000 (TREC) 9,100 Pb, dissolved (µg/L)

40 1.6 310 Zn, dissolved (µg/L)

99 86 24,700

LMPs

50

500

2,000

2,000

200

1,500

Sulfate and Sulfide

Results

BCR

Influent 1/

BCR

Effluent 1/

Percent Removal

BCR Influent to

BCR Effluent

APC

Effluent 2/

Sulfate (mg/L) 281 119 57.2% 122

Sulfide (mg/L as S) 3/ 0.12 12.5 - 0.16

Cadmium, Dissolved • BCR influent average: 130 µg/L • BCR effluent average: 0.19 µg/L • BCR average removal: 99.8%

Results

Copper, Dissolved • BCR influent average: 240 µg/L • BCR effluent average: 1.4 µg/L • BCR average removal: 98.6%

Results

Iron, Total • BCR influent average: 7,100 µg/L • BCR effluent average: 560 µg/L • BCR average removal: 95.0%

Results

Lead, Dissolved • BCR influent average: 280 µg/L • BCR effluent average: 2.2 µg/L • BCR average removal: 98.4%

Results

Zinc, Dissolved • BCR influent average: 24,400 µg/L • BCR effluent average: 73 µg/L • BCR average removal: 99.6%

Results

Results

BCR Performance • Consistently meeting acute stream standards: • Cadmium, copper, iron, lead, zinc

• Consistently meeting chronic stream standards: • Copper, lead, zinc

• Effluent concentrations well below LMPs

APC Performance • Necessary for polishing of BOD and sulfide in BCR effluent

Conclusions

Applicability to meet Peruvian LMP standards: • Passive treatment is occurring in Peru • Passive treatment methods can achieve LMPs • Method is suitable for mountain climate of Peru • Passive treatment ideally suited for: Lower flow sites Sites with significant land availability Sites without electricity

• Types of sites Active mines Mine closures Legacy sites

Conclusions

Co-authors: • Tom Rutkowski • Eric Blumenstein • Neal Gallagher • John DeAngelis (PWT) • David Reisman (EPA) • Christina Progress (EPA)

Tom Rutkowski

Trutkowski@golder.com

Thank You!