shawn naylor greg a. olyphant tracy d. branam. pros: disposal of large volumes of byproducts...

Hydrochemical Effects of Using Coal Combustion Byproducts as

Structural Fill and Capping Material at an Abandoned Mine

Lands Reclamation Site, Southwestern Indiana

SHAWN NAYLOR GREG A. OLYPHANTTRACY D. BRANAM

Pros:

•Disposal of large volumesof byproducts associated with energy production

•Minimal disturbance of adjacent areas for fill materials

•Introduce alkalinity

•Low permeability of some engineered CCBsprevents recharge and movement of groundwater

Cons:

•Contains potentially toxic metals

•Poor understanding of leachate mobility in natural environments

•Subsequent removal of these materials would present difficulties if such measures were ever deemed necessary

Pros and Cons of Using CCBs in Reclamation

The Indiana Department of Natural Resources wanted to use CCBs to positively alter the hydrology of an AML site and improve chemistry of surface water exiting the site

Reclamation goal

Although several researchers have used laboratory experiments to examine the physical and chemical characteristics of CCBs, studies that comprehensively examine the impacts of CCBs in applied settings are few.

To determine the long-term physical and chemical effects of CCBs on a reclaimed AML site, baseline data are compared with post-reclamation data from several unique monitoring sites where CCBs were emplaced.

Purpose of study

•Surface and underground coal mining, 1895 to 1983

•Pyrite / associated weathering products were distributed among a large pyritic refuse pile in a central lowland area, underground mine workings, and highwall ponds (total area ~50 hectares)

History of Midwestern AML site

•AMD issued from a spring draining the underground mine workings and as baseflow from the central lowland aquifer

•In 1996, ~450,000 m3 of CCBs were used as cap and fill material during reclamation

Midwestern AML study area

CCBs Utilized at Midwestern Site

Structural fill: Ponded ash

3:2 ratio, fly ash : bottom ash

Cap: Fixated scrubber sludge (FSS)

1:1 ratio, fly ash : FGD sludgewith 1.5 - 2% quicklime

0

100

200

300

400

500

600

700

800

900

As Ba B Cd Cr Cu Pb Hg Mo Ni Se

Conc

entr

ation

(mg/

kg)

FSSBottom AshFly Ash

Trace element concentrations for FSS and component CCBs used to produce FSS and ponded ash (analyses conducted prior to CCBs being wet sluiced)

Central refuse area prior to reclamation

Midwestern site prior to and during reclamation

North highwall pond prior to reclamation

Emplacement of ash fill at south pond

Final grading and emplacement of soil cap (1m of reworked spoil and animal waste)

Final reclamation steps

Rip rap channels installed to divert runoff followed by revegetation

Final grading and emplacement of soil cap

Final grading and emplacement of soil cap (1m of reworked spoil and animal waste)

Final reclamation steps


Post-reclamation monitoring (November 1996 – November 2009)

Methods: Physical hydrology

Soil moisture profiles

•Measured using a neutron probe

Evapotranspiration

•Estimated using a weighing lysimeter

Discharge

•Measured using a v-notch weir at the site outlet (SW4 / SW8)

Water levels

•Continuous data recorded using pressure transducers

Chemical analyses

Field chemistry

•pH

•Eh

•SpC

•Temperature

•Acidity

•Alkalinity

Major cations

•Ca

•Mg

•K

•Na

•Fe2+

•Fe3+

Trace elements

•As

•Sb

•Ba

•B

•Cd

•Cr

•Cu

•Pb

•Se

•Ag

Minor cations

•Al

•Mn

•Ni

•Sr

•Zn

Major anions

•F

•Cl

•NO3

•HCO3

•SO4

oRSETPR R = groundwater recharge calculated as the residual

ET = evapotranspiration

P = precipitation

DS = change in unsaturated zone soil moisture storage

Ro = runoff

Water Balance Calculations

Period P (cm) ET (cm) DS (cm) Ro (cm) R (cm)

7/14/95 - 10/10/95 15.0 -8.8 (59%) NA2.5

(17%)3.7 (25%)

7/14/00 – 10/10/00

36.3 -24.5 (67%) -0.1 (0%)6.2

(17%)5.8 (16%)

7/14/00 - 7/18/01 94.1 -54 (57%) 1.9 (2%)19.9

(21%)18.3 (19%)

Water balance used to indicate relative pre- vs. post-reclamation rates of groundwater recharge

ttttt ePbBbbWL 210

Statistical analysis of refuse aquifer water level changes

Statistical Model:

DWLt = daily water level change in refuse aquifer (MW7)

b0 = regression constant

b1 = regression coefficient for barometric pressure (“barometric efficiency”)

DBt = daily barometric pressure change (cm H2O)

b2 = regression coefficient for precipitation

Pt = daily precipitation (cm)

ret = autocorrelated error term

ut = random error term

Pre-reclamation (1995) n=140, R=0.56, r =0.13

parameter estimate standard error t-ratiob1 (barometric press.) -0.21 0.05 -4.55

b2 (precipitation) 1.05 0.19 5.48

Post-reclamation (1998) n=235, R=0.89, r =0.00








b2 (precipitation) -0.04 0.18 -0.20

Statistical analysis of refuse aquifer water level changes

Fluctuations in perched water overlying FSS cap

Middle of cap

Edge of cap

0.30.6000000000

000010.9

1.2

1.5

1.8

2.1

2.4

2.7

3.1

3.4

3.7

4

4.3

0 0.1 0.2 0.3 0.4 0.5

MW 4 Soil Moisture

Volumetric Moisture Content

Dep

th (m

)

Top of FSS layer

Spoil

N = 28

0.3

0.600000000000001

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3

3.3

0 0.1 0.2 0.3 0.4 0.5

MW7 Soil Moisture

Volumetric Moisture ContentD

epth

(m)

Top of FSS layer

N = 27

Soil moisture data from former central lowland area

whiskers = min/max

bars = 25th/ 75th percentile

white line = median value

red squares = mean value

SO4

(mg/l)

Fe(mg/l)

Acidity(mg/l)

Alkalinity(mg/l)

pH SpC(μmhos/cm)

TDS(mg/l)

Pre-reclamation water chemistry (April through August 1995)

SP1n=3

13801220-1540

7665-82

369193-720

110-34

4.13.7-5.1

19581927-1988

20331900-2100

MW7n=3

129678200-17500

44332800-5700

117327507-15817

00-0

1.41.1-1.8

2209313700-32800

2333312000-35000

SW4n=4

23532280-2500

243190-330

714451-901

00-0

2.92.8-3.1

32153030-3350

36503300-3900

SW2n=4

550370-690

346-80

27892-523

00-0

2.72.6-3.1

1479930-1758

848600-970

SW1n=4

18694-240

61-18

10411-350

00-0

4.24.0-5.3

460392-508

338230-420

MW5n=4

26952520-2880

285250-320

885825-979

00-0

3.13.0-3.4

35553390-3790

42753700-4700

Post-reclamation water chemistry (November 1996 through June 2007)

SP2A1463

722-1680n=20

8664-120n=19

159122-217

n=20

267218-323

n=20

6.46.0-7.3n=20

25311836-2810

n=20

26322336-3000

n=17

MW78119

2192-15900n=20

2421785-5700

n=18

58391560-13413

n=20

00-0

n=20

2.31.6-4.0n=20

88904103-20800

n=20

151226405-29000

n=17

SW81579

625-2360n=20

282-83n=19

1390-350n=19

320-140n=20

3.52.7-7.0n=20

24481408-3389

n=20

24521600-3600

n=17

MW81794

1650-2270n=20

10-6

n=19

200-70n=20

5529-123n=20

7.06.2-8.7n=20

30142516-3269

n=20

41922686-6823

n=17

MW91687

1370-1972n=18

14516-197n=18

37243-578n=17

234104-460

n=18

6.05.6-7.1n=18

27401832-3172

n=18

30092400-3600

n=17

MW5S2745

2175-4740n=17

27546-482n=17

524110-913

n=17

1100-330n=16

5.24.3-6.8n=17

37262872-4950

n=17

50193500-9100

n=15

Summary of chemical analyses

Site outlet(pre-rec.)

Site outlet(post-rec.)

Changes in refuse aquifer (MW 7) supported by field chemistry data

Jun-9

4

Oct-9

5

Mar

-97

Jul-9

8

Dec-9

9

Apr-01

Sep-0

2

Jan-0

4

May

-05

Oct-0

6

Feb-0

80

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0

5

10

15

20

25

30

35

R² = 0.500221403032104

R² = 0.546433719999236

pHLinear (pH)

pH

Sp

C (m

S/cm

)

Jun-9

4

Oct-9

5

Mar

-97

Jul-9

8

Dec-9

9

Apr-01

Sep-0

2

Jan-0

4

May

-05

Oct-0

6

Feb-0

8

Jul-0

9

Nov-10

0

2000

4000

6000

8000

10000

12000

14000

16000

0

1000

2000

3000

4000

5000

6000

7000

8000

acidity arsenic

To

tal

acid

ity

(mg

/L)

Arsen

ic (µg/L

)Refuse aquifer (MW 7) acidity and arsenic concentrations

Jun-9

4

Oct-9

5

Mar

-97

Jul-9

8

Dec-9

9

Apr-01

Sep-0

2

Jan-0

4

May

-05

Oct-0

6

Feb-0

8

Jul-0

9

Nov-10

0

5

10

15

20

25

30

35

40

MW7 SW2/MW8 SW1/MW9

Bo

ron

(m

g/L

)

FSS over refuse

FSS over ash-filled pond

Ash-filled pond

Boron concentrations in refuse aquifer and ash-filled ponds

Jun-9

4

Oct-9

5

Mar

-97

Jul-9

8

Dec-9

9

Apr-01

Sep-0

2

Jan-0

4

May

-05

Oct-0

6

Feb-0

8

Jul-0

9

Nov-10

0

10

20

30

40

50

SW2/MW8 SW1/MW9

Ars

enic

(µg

/L)

Arsenic concentrations at ash-filled ponds (SW2/MW8 and SW1/MW9)

EPA max. cont. level (10 µg/L)

Conclusions – physical hydrology

•There has been a reduction in groundwater recharge that is attributed to:

1. Effectiveness of FSS cap that is distributed over 15% of the study area

2. Re-vegetation efforts have increased evapotranspiration

3. Increased barometric efficiency of the refuse aquifer indicates that it is now behaving as a confined aquifer

4. Perched water atop the FSS and little fluctuation in soil moisture content within the cap indicate that direct recharge of the refuse aquifer with oxygenated meteoric water is no longer taking place

Conclusions – hydrochemistry

•Long-term general improvements in water quality can be seen at each monitoring site

•Alkalinity is now intermittently present at the site outlet and most of the other sites now regularly contain alkalinity

•Improving trends in pH and SpC at the refuse aquifer (MW7) coincide with decreases in sulfate, total iron, lead, and total acidity

•Arsenic and Boron remain slightly elevated at ash-filled lakes although the most recent sampling event in November, 2009 resulted in non-detect results for Arsenic at these sites

Acknowledgements

•Much of this work was funded by grants from the Indiana Department on Natural Resources, Division of Reclamation

•Field work, including instrumentation and data collection, was coordinated by Jack Haddan with assistance from Curt Thomas, Kevin Spindler, Dana Cannon, Jeff Olyphant, and Jimmy Boswell. Lab analyses were conducted by Peg Ennis and Ron Smith. Denver Harper played a vital role in the design of the monitoring network, interpretation of pre-reclamation mine features and hydrology, as well as the development of a site GIS database.

Questions?

shawn naylor greg a. olyphant tracy d. branam. pros: disposal of large volumes of byproducts...

Documents

reclamation slide

site reclamation goal

revegetation slide

reclamation midwestern

reclamation emplacement

branam slide

south pond slide

emplacement of soil