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Since industrial revolution, demands andcosts for construction-grade sand and

A STATISTICAL APPROACH FOR RESTORATION OF DISTURBED LAND WITH COAL COMBUSTION BYPRODUCT AGGREGATES

Isomar Latorre, Daniel Roman, and Sangchul HwangDepartment of Civil Engineering and Surveying, University of Puerto Rico, Mayagüez, PR

Introduction Statistical Experiment

Experiment Purpose:

Conclusions

Statistical design showed a neutral impactof the CAAs on gro nd ater q alit incosts for construction grade sand and

gravel has subsequently increased.Open pit quarries potentially representphysical risks to safety of people andstock due to dangerous vertical pit wallsor deep water. Also, they can be apossible source of environmentalpollution from water accumulation unlessproperly drained. Therefore, a needexists to develop an economical andenvironmentally sound restoration. Forthi l b ti b d t

Current Studies

3-Factor, 2-Level Statistical Reactor Set-up

of the CAAs on ground water quality interms of pH, turbidity, and hardness.

CAAs amendment for restoration ofdisturbed lands such as open pit seems tobe a viable engineering practice, not onlyachieving resource recovery but alsoconserving environmental quality.

Determine impact of possible refillingmethods by a statistical design andanalysis on the quality of waterinfiltrated from each setting.

High and Low Rainfall Intensity

Vmax=60mL Vmin= 30mL

CAAs size

A: 4.75 ~9.53 mm, B: 2.36~4.75 mm

Volumetric ratio of the CAAs to top soil

Statistical Design Optimization

Variable Parameters

this reason, coal combustion byproductaggregates (CAAs) were proposed as apotential backfilling amendment material.

Test the feasibility of coal combustionash aggregates (CAAs)-amended refillfor the open pit restoration.

Assess the potential risks in relation tocontamination of soil and groundwater

Reactors Top Soil (in) CCPs (in) Bottom Soil (in) Site Soil (in) CAAs SizeRain

IntensityR1 8 4 4 10 A HighR2 8 4 4 10 A HighR3 8 4 4 10 A LowR4 8 4 4 10 A LowR5 8 4 4 10 B HighR6 8 4 4 10 B HighR7 8 4 4 10 B LowR8 8 4 4 10 B LowR9 4 8 4 10 A HighR10 4 8 4 10 A HighR11 4 8 4 10 A LowR12 4 8 4 10 A LowR13 4 8 4 10 B HighR14 4 8 4 10 B HighR15 4 8 4 10 B LowR 4 8 4 10 B L

Worst Case Scenario Best Case ScenarioLow Rainfall Intensity

(10 mL/min)High Rainfall Intensity

(20 mL/min)

bigger size(4.75 - 9.53 mm) small size(2.36 - 4.75 mm)

more aggregate less aggregateObjectives

co ta at o o so a d g ou d ateassociated with the use of an industrialbyproduct CAA.

Weekly measurements: amount of water percolated to the system, water pH, water Turbidity, nitrate concentrations, conductivity, lead and cadmium concentrations

Project Location

Santa Isabel Open Pit Q arr

R16 4 8 4 10 B Low

Statistical Analysis

3-Factor, 2-Level Statistical AnalysisHardness Example

A (CAAs size) B (Rainfall Intensity) C (CAAs /top soil ratio)

System 1, 2, and 4

Preliminary Results

System 1: WCS (10 C) System 2: WCS System 3: BCSSystem 4: Individual Soil and CCPs Evaluation (WCS)System 5: Individual Soil and CCPs Evaluation (BCS)

System 3 and 5

0

200

400

600

800

1000

R1 R2 R3 R4 R5 R6 R7 R8

Day 0

Day 14Hardness (System 1)

Coamo Lake(Top Soil)

Soils

Santa Isabel Open Pit Quarry

Results

Open Pit Restoration

3 m

Organic Top Soil

Coal Ash Aggregates 500

1000

1500

2000

2500

Top soil : CAA = 2 : 1

Top soil : CAA = 1 : 2

Calculations Example for Hardness Parameter

400600800

100012001400160018002000

High rain intensity

Low rain intensity

Also, cadmium concentrations, lead

0

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700

R1 R2 R3 R4 R5 R6 R7 R8

Day 0

Day 14

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500

600

Day 0

Day 14

Hardness (System 2)

Hardness (System 3)

Guayama Bay(Bottom Soil)

Santa Isabel (Site Soil)

CCPs

Bottom Soil

Top Soil

0.3 m

Santa Isabel

Site Soil

20 ~ 60 m

GWT

Sandy Bottom Soil

0

7 9 14 18 25 30 35 39 44 49 53 60 63

Days

0200

7 9 14 18 25 30 35 39 44 49 53 60 63

Days

0200400600800

100012001400160018002000

7 9 14 18 25 30 35 39 44 49 53 60 63

Days

Big CAA size

Small CAA size

A AA A

A AAB B B B B

BB

BB

C C CAC ACAC AC ACBC BC BC BCABC

0

5

10

15

20

25

7 9 14 18 25 30 35 39 44 49 53 60 63

Ha

rdn

ess

Sta

nd

ard

ize

d e

ffe

cts

Days

A B

C AC

BC AB

ABC

Future StudiesIncreasing top soil, CCPs, bottom soil, and site soil length,

measure water quality independently, when comes out of eachmaterial. This will be at different temperatures and different soilsfor site specific cases evaluation.

Sandy aquifer materials will be collected and packed on-siteand groundwater flow will be simulated by pumping the localgroundwater at an average linear velocity.

concentrations, pH, conductivity, alkalinity and total heterotrophic bacteria

were measured.0

100

R1 R2 R3 R4 R5 R6 R7 R8

This research has been supported by AES Puerto Rico and US Geological Survey Water Resource Grant State Program. Assistance and help provided by the members

of environmental engineering laboratory are greatly appreciated, especially Daniel Roman for his sincere

contribution to the project.

Dr. Sangchul Hwang

Department of Civil Engineering, UPRM

787-832-4040 ext. 3454; shwang@uprm.edu

CAAs

Solidified mixture of fly and bottom ashes with waterMain chemical components:

SiO2 + Al2O3 + Fe2O3 (51 %)Lime (CaO (30 %), SO3 (15%))

Obtained from a local coal burning power plant

Site Soil

Acknowledgments Contact

Aquifer Sand

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CR R1

R2

R3

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R10 R11

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Ha

rdn

ess

(m

g/L

as

Ca

CO

3)

Reactors

Hardness

day 0

day 7

day 9

day 14

day 18

day 25

day 30

day 35

day 39

day 44

day 49

day 53

day 60

day 63

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rdn

ess

(m

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as

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CO

3)

Days

CR

R1

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Days

Worst and best case scenario configuration with nitrate-containing water percolating the restoration matrix.