2007 REMEDIAL PROGRESS KENNECOTT NORTH ZONE North Zone TRC March - - PowerPoint PPT Presentation

2007 REMEDIAL PROGRESS KENNECOTT NORTH ZONE

North Zone TRC March 5, 2008 Kelly Payne, P.G. Principal Advisor, Closure & Remediation

This Afternoon’s Discussion

• Demolition Activities
• Bingham Magna Ditch
• Groundwater Monitoring and Management
• Smelter Selenium Plume In Situ Treatment Pilot Testing
• Refinery Selenium Plume Remedy Modification
• Consent Decree between KUCC and US F&WS
• Wetlands Monitoring

29 June 2005 Presentation title 3

29 June 2005 Presentation title 4

Demolition

Groundwater Monitoring and Management

Refinery Selenium Plume Source Area

97 98 99 00 01 02 03 04 05 06 07 08

Se-D (µg/l)

5000 10000 15000 20000 25000 NER2546A NER2546B

Refinery Selenium Plume Garfield Townsite

97 98 99 00 01 02 03 04 05 06 07 08

Se-D (µg/l)

2500 3000 3500 4000 4500 5000 5500 6000 NER2554A

Refinery Selenium Plume Kessler Springs

97 98 99 00 01 02 03 04 05 06 07 08

Se-D (µg/l)

600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 WTS2577

Refinery Selenium Plume Garfield Well #5

97 98 99 00 01 02 03 04 05 06 07 08

Se-D (µg/l)

100 200 300 400 500 600 700 NEG485

Smelter Selenium Plume In Situ Pilot Testing

Engineered Metal Sequestration

• Approach: use microbes to transform selenium to a chemically

stable form as it is found in ore bodies, and then additionally deposit minerals that will maintain these conditions in situ to stabilize the selenium precipitates over geological timescales. Additionally, precipitation of accessory minerals create conditions which further sorb new selenium in flux by creating sorptive barriers.

• US Patents:

– 5,554,290 In situ reactive zones – 5,632,715 Immobilization of heavy metals in waste stacks and affected zones – 5,710,361 Immobilization of heavy metals in earth materials (CIP

• f `715)

– 5,833,855 In situ bioremediation of contaminated groundwater

Eh-pH Conditions In Plume Eh-pH Conditions After ARCADIS Treatment

Selenium Treatment: Diagrammed

Engineered Selenium Precipitation

Reductive Precipitation/In Situ Permeable Reactive Barrier

• Introduction of organic carbon to aquifer via upgradient injection to

create anaerobic/reducing conditions to electrochemically convert selenium from the soluble oxidized form (selenate/selenite) to the insoluble reduced form (elemental selenium).

• During creation of reducing conditions, existing and potentially added

iron and sulfate in the aquifer are converted to iron sulfide minerals which continue to “protect” the reduced selenium from oxidation by consuming oxygen after carbon injections stop.

• As iron sulfide minerals are oxidized to ferric iron minerals, a highly

sorptive permeable reactive barrier is formed in the aquifer which has an affinity for selenium, thus sequestering it in situ. As the iron

• xidizes, it passivates the surface of the grains acting as a physical

barrier to oxygen.

In Situ Pilot Testing

• May 21-June 9, 2007 – Injection and Monitor Well

Installation

• August 11, 2007 – First Nutrient and Tracer Injection

(Molasses, Fluorescein dye)

• October 18, 2007 – 2nd Nutrient and Tracer Injection

(Molasses, FeSO4, Fluorescein dye)

• November 29, 2007 – 3rd Nutrient and Tracer Injection

(Molasses, FeSO4, Fluorescein dye)

• January 9, 2008 – 4th Nutrient and Tracer Injection

(Molasses, FeSO4, Fluorescein dye)

• February 27, 2008 – 5th Nutrient and Tracer Injection

(Molasses, FeSO4, Fluorescein dye)

Monitor Well 1 (15 feet downgradient of injection line)

Monitor Well 2A (45 feet downgradient of injection line)

Monitor Well 3 (72 feet downgradient of injection line)

• Under oxidizing conditions, arsenic (As) is insoluble and

bound to iron (oxy)hydroxide minerals.

• Under iron-reducing conditions, ferric iron (Fe3+) is

reduced to ferrous iron (Fe2+) which dissolves the iron minerals and releases the bound arsenic into solution.

• If sulfate-reducing conditions are achieved, sulfate

(SO4

2+) is reduced to sulfide (HS-) which is very reactive

with ferrous iron (Fe2+) and quickly precipitates out as FeS (iron sulfide). FeS sequesters soluble arsenic into the structure.

What about Arsenic?

(Arsenic sequestration into iron sulfides)

H2O H2 O2 H2O NO3

• N2

MnO2 Mn2+ Fe(OH)3 Fe2+ SO4

2-

HS- CO2 CH4

Nitrate Reduction Manganese Reduction Sulfate Reduction Methanogenesis Iron Reduction

Selenium Reduction (Arsenic liberation from iron matrix)

Oxidizing Aerobic Metabolism Reducing

Organic carbon added to the system stimulates biologic growth, which drives the geochemistry to reducing conditions and depletes electron acceptors in a stepwise fashion. Aqueous arsenic concentrations typically increase when iron-reducing conditions are reached and decrease once sulfate- reducing conditions are reached. Once sulfate-reducing conditions are reached, the reduced iron (Fe2+) and reduced sulfate (sulfide, HS-) react and form insoluble iron sulfide minerals which encapsulate arsenic and sequester it.

Reduction/Oxidation Reactions

• Arsenic is only soluble between iron-reducing and

sulfate-reducing conditions.

• Continuing to provide carbon to maintain sulfate-reducing

conditions along with a stoichiometric excess of ferrous iron stabilizes the arsenic in the iron sulfide (FeS) matrix.

• Excess iron sulfide also stabilizes elemental selenium

(Se) by acting as a redox buffer over time.

Arsenic Control

Arsenic Beyond the IRZ

Iron-reducing conditions are reached prior to sulfate-reducing conditions so arsenic can be released and transported through the reactive zone. However, the distal end of the IRZ is oxidizing and dissolved iron and arsenic are re-oxidized in this zone.

Degradable carbon (electron donor) injection

100 200

O2-reducing Days Travel in Groundwater O2-reducing

NO3-reducing SO4-reducing CO2-reducing Mn-reducing Fe-reducing

Redox Recovery Zone

Refinery Selenium Plume Remedy Modification

• ROD-selected remedy includes in situ treatment for

selenium

• KUCC believes that in situ treatment is impracticable in

bedrock aquifer based on dye tracer test in 2003

• KUCC also perceives risks due to aquifer plugging and

arsenic mobilization

• Request submitted to EPA and DEQ in February 2008 to

modify remedy

• Modified remedy would rely on continued capture with ex

situ treatment and monitored natural attenuation

Consent Decree Between KUCC and US F&WS

• Settlement of natural resources damage claims by US

F&WS for alleged injury to migratory birds and habitat in North Zone Wetlands

• Settlement includes

– Transfer of 617 acres and water rights to The Nature Conservancy – Property Improvements – Endowment Fund – Government’s assessment costs

• CD lodged with US District Court 2/15/08

– Comments accepted 2/22/08 to 3/24/08

• Draft Restoration Plan released by US F&WS

– Comments accepted 3/3/08 to 4/2/08

Wetlands

2007 Monitoring Summary

• All ponds sampled for water, sediment, and macroinvertebrates,

except – Pond 6D2, filled in 2007 – Pond 6E, 12A, and 12C, dry – Pond 9c, no macroinvertebrates

• Water and sediment analyzed by KEL
• Macroinvertebrate tissue in sediment analyzed by LET, Columbia,

MO, a FWS approved lab

• For sediment sampling, separate samples collected from organic

flocculent and underlying mineral soil

2003 2004 2005 2006 2007

Tissue Se (mg/kg)

10 20 30 40 50 60

Recommendations

Meets Clean-up Criterion (<5 ppm) Improving (<10 ppm) Moderately Elevated, Possibly Increasing Moderately Elevated and Consistent (10-15 ppm) Elevated (>15 ppm) No Further Action Monitor Monitor 6A1 6A3 6C 10 11 Monitor and Re-evaluate Risk Drain or Fill 4C2 9C 12A 12B 12C 12D 6A2 6B 6D1 6E 9A 9D 5 7A 8 2 4A 4B 4C1 4C3

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

5 10 15 20 25 30 Bulk Sediment Flocculent Mineral Soil

Pond 4C2

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

1 2 3 4 5 6 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 9C

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

2 4 6 8 10 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 12A

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

2 4 6 8 10 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 12B

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

2 4 6 8 10 12

Water TDS (mg/l)

10000 20000 30000 40000 50000 Selenium Year vs TDS 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 12C

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

2 4 6 8 10 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 12D

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

2 4 6 8 10 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 6A1

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

5 10 15 20 25 30 35 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

5 10 15 20

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 12 Bulk Sediment Flocculent Mineral Soil

Pond 6C

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

5 10 15 20 25 30

Water TDS (mg/l)

0.0 2.0e+4 4.0e+4 6.0e+4 8.0e+4 1.0e+5 1.2e+5 Selenium TDS 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

2 4 6 8 10 12 14

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

2 4 6 8 10 Bulk Sediment Flocculent Mineral Soil

Pond 10

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

10 20 30 40 50 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

5 10 15 20

2003 2004 2005 2006 2007 2008

Sediment Se (mg/kg)

10 20 30 40 50 60 70 Bulk Sediment Flocculent Mineral Soil

Pond 4C1

2003 2004 2005 2006 2007 2008

Water Se (µg/l)

5 10 15 20 25 30 35 2003 2004 2005 2006 2007 2008

Tissue Se (mg/kg)

20 40 60 80 100