Variability of Coal Mine Drainage in Pennsylvania Resulting from Coal

Mining Practices and Geology

Terry W. Schmidt

• Presented at Pennsylvania Abandoned Mine Reclamation Conference, August 10, 2013.

• Terry W. Schmidt, P.E., Vice President, Engineering, Skelly And Loy, Inc., 2601 North Front Street, Harrisburg, PA 17110.

Presentation Promises

• No formulas

• Few technical terms

- (keep it simple)

• Lots of pictures

• Mostly generalizations

- (won’t dwell on exceptions)

AMD Formation

Pyrite (sulfur)+

Oxygen+

Water+

Bacteria=

AMD (Coal Mine Drainage)

Pennsylvania Coal Fields

Source: USGS

Anthracite Regional History

• Mid-1800’s – coal was extensively mined– fueled America’s industrial revolution– coal became the economic base of the region

• Post-1917– coke replaced anthracite in steel-making– demand for anthracite coal declined– coal-related employment declined

• 1950’s– many remaining active mines were flooded– major underground mining operations ceased– coal industry & regional economy collapsed within a short time

Typical Anthracite Geology

Typical Anthracite Cross Section

WhalebackWhaleback

ANTHRACITE MINING

• Underground Mining– Breast and Pillar– Room and Pillar– Retreat Mining

• Surface Mining– Contour Mining– Open Pit

Anthracite Breast and Pillar Mining

Anthracite Underground Mining

Anthracite Open Pit Mining

Contour Style Surface MiningContour Style Surface Mining

Actual Cross Section Through Porter and Tower City Tunnels

Geology - Pit Near Porter TunnelSchuylkill County

Porter Tunnel Characteristics

• Flow 700 – 7,000 gpm

• 3 pH

• 100 mg/L acidity

• 20 mg/l iron

• Low Al and Mn

Bear Creek, Lykens Tunnel, Dauphin County

Bear Creek, Lykens Tunnel, Dauphin County

Bear Creek, Lykens DriftDauphin County

RT 309 Tamaqua, Schuylkill County

RT 309 Tamaqua, Schuylkill County

Nanticoke Creek, Luzerne County

Nanticoke Creek, Askam Borehole, Luzerne County

Eastern Middle Anthracite Region

• 33 square-miles mining – 13 rock tunnels

• 120 square-mile surface drainage area

• Spans Carbon, Columbia, Luzerne, and Schuylkill Counties

Cross Section in the City of Hazleton

Jeddo Tunnel

Jeddo Tunnel

9 feet wide 7 feet high

30,000 GPM

Anthracite Summary

• Highly variable geologic structure

• Low levels of sulfur minerals (OB & coal)

• Tunnel/borehole control of water levels

• Vast interconnected mining complexes

• Higher discharge flows

• Lower acidity and metal concentrations

• Discharge locations often near stream

BITUMINOUS MINING OPERATIONS

• Underground Mining– Room and Pillar– Longwall

• Surface Mining– Contour Mining– Area Mining

Typical Bituminous Geology

Area Dragline Mining

Area Dragline Mining

Contour and Area Mining Reclamation

Bituminous Surface MiningSomerset County

Bituminous UndergroundBituminous Underground

PROJECT LOCATION MAP

Down Dip versus Up Dip, Clearfield County

Yorkshire #1 (down dip)

• Clarion “A” seam coal• 10 degree dip (S/SE)• Completed 1942• 540 acres• 50 % coal recovery• 3% sulfur in coal• 300’ maximum to surface• 2 discharges

Shoff Mine (up dip)

• Clarion “A” seam coal• 10 degree dip (S/SE)• Completed late 1930s• 428 acres• 35-100% coal recovery• 3% sulfur in coal• 300’ maximum to surface• 5 discharges

Down Dip versus Up Dip

Yorkshire #1 (down dip)

• 90% workings inundated• 129 mg/L acidity• 107 mg/L iron• 1,009 mg/L sulfate• 7.3 mg/L aluminum

Shoff Mine (up dip)

• <10% workings inundated• 1,408 mg/L acidity• 365 mg/L iron• 1,398 mg/L sulfate• 6.8 mg/L aluminum

Cold Stream

• Watershed Area of 21 Square Miles• Over 10 miles Length in Centre County• Extensive Mining in Lower 2.5 Miles• Over 30 Known Underground Mine

Openings along Cold Stream• Upper Reach Classified as High Quality

Cold Water Fishery (HQ-CWF)• Lower Reach Supports NO Fishery

Glass City, Cold Stream Centre County

FLOW RATE: 0 – 1400 gpmTOTAL IRON: 40 – 50 mg/LpH: 2.5 – 3.0NET ACIDITY: 400-500 mg/LMANGANESE: 1 – 7 mg/LSULFATES: 100 – 600 mg/LALUMINUM: 15 – 25 mg/L

Cold Stream, Mine Drift, Centre County

Cold Stream, Mine Drift, Centre County

Hubler Run Clearfield County

Raw water quality– Q AVG = 19 GPM– Q MAX = 45 GPM– Average Acidity = 115 mg/L– Average iron < 1 mg/L– Average Aluminum = 17 mg/L

Elk Creek, Elk County

Average Raw AMD:Flow = 10 gpmpH = 5.5Fe = 15 mg/LAcidity = 100 mg/L

St. Michael Discharge,Cambria County

• primary discharge emanates from the St. Michael Shaft located along Topper Run

• represents the largest pollutant loading to the Little Conemaugh River

• shaft extends 600 feet to the Lower Kittanning Coal Seam

• results from artesian pressure in the mine pool

DISCHARGE CHARACTERISTICS

• Flow rates range from 2,000 to 4,000 gallons per minute (GPM)

• Unites States Geologic Survey (U.S.G.S.) sample data indicated:- dissolved oxygen = 0.4 milligrams per liter (mg/L); - field pH = 5.4; - acidity = 380 mg/L; - aluminum = 0.6 mg/L; and - iron = 174 mg/L.

Cessna Run, Indiana County

• Average Raw AMD:

• Flow = 90 gpm

• pH = 5.5

• Al = 6 mg/L

• Fe < 2 mg/L

• Acidity = 120 mg/L

Blacklegs Creek #7Indiana County

Average Raw AMD:Flow = 800 gpmFe = 1 mg/LAl = 15 mg/LHot Acidity = 150 mg/L

Blacklegs Creek #8 Drainage Tunnel, Indiana County

Blacklegs Creek Kolb Indiana County

Kolb Site

• Located in Indiana County, Pennsylvania• Abandoned underground mine discharge• High flow (approximately 1,000 gallons per

minute)• DO concentration at the underground mine

was typically less than 1 mg/L• Elevation drop of 40 feet from the mine

discharge to treatment location

Boyce Park, Allegheny County

• BP 2• pH = 4.8 • Fe < 1.0 mg/L• Al = 24 mg/L• acidity = 77 mg/L

• BP 3• pH = 3.3• Fe = 4 mg/L• Al = 23 mg/L• acidity = 265 mg/L

• BP 4• pH = 4.8 • Fe = 17 mg/L• Mn < 1.0 mg/L• Al = 79 mg/L• acidity = 488 mg/L

Dunkard Creek – Greene County

Site 2A:Flow = 35 gpmpH = 3.7Fe = 25 mg/LAl = 23 mg/LHot Acidity = 220 mg/L

Dunkard Creek – Greene County

Site 2BFlow = 390 gpmpH = 3.1Fe = 41 mg/LAl = 33 mg/LHot Acidity = 380 mg/L

Dunkard Creek – Greene County

Sagamore Site

• Located in Fayette County, Pennsylvania• First documented use of a windmill aerator at

a passive treatment system• Two discharges treated with a flow rate of

100 gpm• Net-alkaline with iron concentrations of 15 to

20 mg/L• Little elevation drop

Broad Top Township, Bedford County

Broad Top Township, Bedford County Over 80 identified AMD discharges

Flows <1 - >500 GPM, highly variable chemistry

30 passive treatment systems (10% of PA systems)

Three 303(d)-listed watersheds (28 square miles):

-Longs Run, Six Mile Run, Sandy Run

Historic underground mining (approx. 184 mine entries) and surface coal mining legacy of isolated Broad Top coal field since the 1800’s

Abandoned underground mines filled with water and drainage from partially reclaimed surface mines have created AMD throughout the Township

Finleyville – Primarily Aluminum

LR0-D14: Primarily Iron

AMD Discharge

Longs Run

Aerobic Wetland (0.1

acre)

Net alkaline discharge with moderate flow and high Fe2+, but very limited space removes ~ 50% of iron; wetland was slightly enlarged &

Aero-Troff added to promote aeration in place of rock-lined channel

LR0-D10: VFW w/ Automatic Inline

Structures

LR0-D10 , flow = 30 gpmacidity = 440 mg/L,Fe = 145 mg/L, Al = 10 mg/L

System Constructed in 2006, Performed One Compost O&M Event Since 2006 on VFW

SX0-D8 Before Treatment

SX2-D5: Preliminary Construction

Exposed Mine Entry/Source of AMD

SX0-D6: Exposed Buried Mine Entries – Two?

SX0-D16 Exposed Mine Entry

Average Raw AMD:Flow = 50 gpmpH = 3.2Fe = 1.0 mg/LAl = 6.3 mg/LHot Acidity = 107 mg/L

SX0-D16 Passive AMD Treatment System Using FLBs & Settling Ponds

Final Outfall (Aug 2009):pH = 7.7Fe = <0.1 mg/LAl = 0.2 mg/LHot Acidity = -26 mg/LAlkalinity = 38 mg/L

SX8-D1

• flow = 120 gpm

• pH = 3.5

• Al = 2 mg/L

• Fe = 30 mg/L

• Acidity = 125 mg/L

SA0-D4 VFW-Based Passive Treatment

Average Raw AMD:Flow = 25 gpmpH = 3.0Fe = 99 mg/LAl = 38 mg/LHot Acidity = 476 mg/L

SA0-D5: Exposed Vertical Shaft

Average Raw AMD:Flow = 70 gpmpH = 3.1Fe = 15 mg/LAl = 16 mg/LHot Acidity = 195 mg/L

Bituminous Summary

• Flatter lying geologic structure

• Variable sulfur mineral levels (OB & coal)

• Groundwater control of water levels

• More smaller mining complexes

• Lower discharge flows

• Higher acidity and metal concentrations

• Variable discharge locations

PA Coal Mine Discharge Comparison

Bituminous

• Regular Geology• Variable Sulfur Content• GW/Entry Control• Isolated UG Complexes• Lower Discharge Flows• Higher Contaminant Levels• Discharge locations vary

Anthracite

• Complex Geology• Lower Sulfur Content• Tunnel/Borehole Control• Vast UG Complexes• Higher Discharge Flows• Lower Contaminant Levels• Discharges near streams

Factors Influencing Coal Mine Drainage

• Availability of sulfur bearing minerals

- coal, overburden, bottom rock

• Availability of water

- rainwater, groundwater

• Availability of oxygen

- inundation, fluctuation in water levels

• Availability of bacteria

AMD Formation

Pyrite (sulfur)+

Oxygen+

Water+

Bacteria=

AMD (Coal Mine Drainage)

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