1
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
100
200
300
400
500
600
700
R1 R2 R3 R4 R5 R6 R7 R8
Day 0
Day 14
200
300
400
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; [email protected]
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
0
1000
2000
3000
4000
5000
6000
CR R1
R2
R3
R4
R5
R6
R7
R8
R10 R11
R12
R13
R14
R15
R16
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
0
500
1000
1500
2000
2500
3000
0 10 20 30 40 50 60 70
Ha
rdn
ess
(m
g/L
as
Ca
CO
3)
Days
CR
R1
R2
R3
R4
R5
R6
R7
R8
R10
R11
R12
R13
R14
R15
R16
Days
Worst and best case scenario configuration with nitrate-containing water percolating the restoration matrix.
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