TDS Reduction from Valley Fills Terry Potter, P.E. Engineering - - PowerPoint PPT Presentation

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Coal-Mac, Inc. TDS Reduction from Valley Fills Terry Potter, P.E. Engineering Manager 2013 West Virginia Mine Drainage Task Force Symposium March 26 - 27, 2013 Coal Mac, Inc. Subsidiary of Arch Coal, Inc. Employees - 306 Annual

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Coal-Mac, Inc. TDS Reduction from Valley Fills

2013 West Virginia Mine Drainage Task Force Symposium March 26 - 27, 2013 Terry Potter, P.E. Engineering Manager

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PROJECT LOCATION

VICINITY MAP Coal Mac, Inc.

Subsidiary of Arch Coal, Inc.
Employees - 306
Annual sales - 3 MM tons
Excavator/Loader mine

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Pine Creek 1 permit area

Valley fill 1 approved by

USCOE, in conjunction with USEPA

Future fills contingent on

Conductivity below Fill 1 remaining below 500 μS/cm during construction

Stream Mitigation required

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Sulfates contribute the greatest increase to TDS – from 16 mg/l to 700 mg/l Bicarbonates are next – from 21 mg/l to 186 mg/l

Identify Source of TDS increase

Pond et al. 2008 Mined Sites (13) Mean SC: 1023 μS/cm Mean ion sum - 1165 mg/L Pond et al. 2008 Un-mined Sites (7) Mean SC: 62 μS/cm Mean ion sum - 56 mg/L

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Material Type Sulfur content Sandstone 100 – 500 ppm Shale 300 – 10,700 ppm Fireclay 400 – 60,600 ppm Coal 6,000 – 60,400 ppm

Design and Construction techniques to reduce sulfates

Construct underdrain of durable, low-sulfur material to reduce

sulfate reaction

Internal and surface drainage to prevent infiltration
Limited initial brushing (5th bench level)

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Check dams and wrapped underdrain

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Nine (9) check dams
Wrap 4,200’ of underdrain with

filter fabric

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Fifth Bench Level Elev. - 1375’

Compact and slope 5% to west side
1,900’ underdrain daylights on 5th

bench

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Coalburg level - 1595’

6,500’ pavement underdrain daylights into sediment ditch

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Valley Fill #1 and Backfill Configuration

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Dissolved Solids Composition at Sample Site BF1&2 Concentration – 195 mg/l

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How do results compare to fills without special BMPs?

Nearby Valley Fill 4

– Approx. 9 MM cu yds

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Dissolved Solids Composition below VF 4 Concentration – 1,229 mg/l

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Sulfates, 640, 52% BiCarbonates, 251, 20% Calcium, 143, 12% Manganese, 135, 11% Sodium, 32, 3% Potassium, 21, 2% Chlorides, 7, 0%

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TDS Comparison

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TDS Constituent Comparison - VF1 vs. VF4

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Compensatory Mitigation

Stream Restoration –

3,800’

Construct three (3)

stream crossings

Install five (5) sand bio-

filters

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Existing Gas well access road through stream

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Road construction and stream crossing

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Mitigated Stream – Left Fork of Pine Creek

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Benthic Locations

CMDLFPC – mouth of

Left Fork

BF 1&2 – directly below

Valley Fill 1 pond.

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Benthic Monitoring Sites

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Site BF 1&2 Site CMDLFPC TDS range 32 mg/l – 211 mg/l WVSCI range 66.92 – 89.639.63 TDS range 244 mg/l – 587 mg/l WVSCI range 55.95 – 83.10

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Site BF 1&2 Graph of TDS vs. WVSCI

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50 55 60 65 70 75 80 85 90 95 100 50 100 150 200 250 300 Winter 2011 Spring 2011 Summer 2011 Winter 2012 Spring 2012 Summer 2012 Winter 2013 TDS WVSCI

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Site WVDLFPC Graph of TDS vs. WVSCI

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50 55 60 65 70 75 80 85 90 95 100 100 200 300 400 500 600 700 800 900 1000 Winter 2011 Spring 2011 Summer 2011 Winter 2012 Spring 2012 Summer 2012 Winter 2013 TDS WVSCI

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Summary

Conductivity has remained below required levels

during construction of Fill 1 for past two (2) years.

Based on this success, US COE, in co-operation

with US EPA, has authorized construction of second valley fill.

The work performed in this watershed has not

resulted in a change in the WVSCI. No real correlation between Conductivity and WVSCI can be determined.

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