NATURAL

RESOU

RCE

TECHNOLOGY

WAmorefi

Leachate

Management

and Final Cover

Alternatives

Analysis Report

Hutsonville

Power

Station

Unlined Ash

Impoundment Pond

Closure

Hutsonville

IL

July

19

2005

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

NATURAL

RESOURCE

TECHNOLOGY

AMEREN

SERVICES

LEACHATE MANAGEMENT

AND FINAL COVER

ALTERNATIVES ANALYSIS REPORT

HUTSONVILLE POWER STATION

UNLINED ASH IMPOUNDMENT

POND

CLOSURE

HUTSONVILLE

IL

Project

No 1375

Prepared

For

Anieren Services

One Anieren Plaza

1901 Chouteau

Avenue

St

Louis

NIissouri

Prepared By

Natural Resource

Technology

Inc

23713

Paul

Road

Suite

Pewaukee

WI 53072

Final

Report

July

19

2005

Christopher

Robb

PE

i4ice

Hensel

PG

Project

Engineer

Senior

Hydrogeologis

23713

Paul

Rd

Ste

Pewaukee

WI 53072

Phone 262.523.9000

Fax 262.523.9001

www.naturalrt.com

Pewaukee

Madison

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

EXECUTIVE SUMMARY

The Hutsonville Power Station in Crawford

County

Illinois is located on the west bank of the Wabash

River

approximately

mile north of

Hutsonville

Illinois

Fly

ash from this coal-fired

power plant

is

collected

by

an electrostatic

precipitator

and has been sluiced

to two

ash

impoundments

Groundwater

quality

has been monitored

at this

facility

since 1984 Concentrations of boron and

sulfate

indicator

parameters

of coal ash

leachate

exceed the Section 811.320

applicable

background

concentrations and Illinois Class Groundwater

Quality

Standards at several shallow

monitoring

wells

near an unlined

impoundment

Pond

which is

no

longer

in service

Impacted groundwater

is

migrating

east towards the Wabash River

through

shallow

sediments

which

are

not utilized

as

source

of

groundwater

supply

Elevated

concentrations

were

also

noted in shallow

monitoring

wells

along

the

south

property

boundary suggesting potential

for off-site

migration

however

impacts

have not been

noted in

water

samples

collected south

of the

impoundment

There are five

groundwater

supply

wells within

mile of the

site

all finished in

deep

alluvial sand

and

gravel

in the Wabash River

valley

Two

wells

directly

east of the unlined

impoundment

are

used for

potable

and

process plant

water

and

one

well southwest and

two

wells

southeast

of the

impoundment

are

used

for

irrigation

water Concentrations of boron and sulfate in

samples

collected from

one on-site

monitoring

well

were

higher

than

811.320

background

concentrations

but lower

than Class

groundwater

quality

standards Six other

monitoring

wells screened in the

deep

alluvial

aquifer

on the Illinois side of

the river show

no

evidence of

impacts

The

primary objective

of this alternatives

analysis

was

to evaluate

and make

recommendations

on

leachate

management deep

alluvial

aquifer

containment

and final cover alternatives

for closure of the

unlined

ash

impoundment Pond

based on technical and

cost

considerations

Alternatives

analysis

objectives

herein referenced

as

Closure

Objectives

were identified to

protect

human health and the

environment for both the

parameters

of concern

POCs

identified in the

Hydrogeologic Assessment

and

to limit

exposure

pathways

in

accordance with

applicable

environmental standards

Site-specific

considerations

for

establishing

appropriate

Closure

Objectives

for Pond

include

proximity

of

the

Wabash

River to Pond

hydrogeology

and

groundwater

quality

in the

vicinity

of

Pond

and the

presence

or

absence of

exposure

pathways

for identified POCs

groundwater

soil

and surface

water

Based on review of the

regulations

promulgated

in 35 Illinois

Administrative Code

IAC

Part 811 and

814 and

site-specific

considerations

identified

above

the

following

Closure

Objectives

were

developed

Manage

groundwater

quality

to meet

the

requirements

of Section 811.320 and

Construct

final

cover

system

that meets the

requirements

of Part 811

or an

adjusted

standard

approved by

the Illinois Pollution

Control Board

PCB

Specific

parameters

for

performing

the alternatives

analysis

were

developed

on the basis of

the results

of the 1999

Hydro geologic Assessment

the Groundwater Model Evaluation

of Impoundment

Closure

Options

dated

January

2000

and

two

supplemental

investigations

performed

for this

analysis

groundwater

flow and

transport modeling

for selected

alternatives

and

considerations

for

pursuing

adjusted

standards

through

the Illinois PCB Four final

cover

alternatives

and four

combinations of final

cover and leachate

management

alternatives

were carried

through

the

groundwater

transport modeling

evaluation

Subsequent

to the model

analysis

four alternatives

were

selected for

detailed

analysis

1375 Alternatives

Analysis Report-Final

NATURAL

ES-i

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

EXECUTIVE SUMMARY

Closure Alternative

No

Geosynthetic

Final Cover with East and South

Interceptor

DrainiTrench and Groundwater

Extraction from the

Deep

Alluvial

Aquifer

This closure

alternative

adheres

to

the Section

811.314

requirements

for

final

cover

system

and

implements

leachate

collection

along

the

east

and south

boundaries of Pond

and

groundwater

extraction

in

the

deep

alluvial

aquifer

to meet the

requirements

for

meeting

applicable

groundwater

quality

standards

at

the

edge

of the

zone of attenuation

as

defined in

Section

811.320c

Closure Alternative

No

Earthen Final Cover with South

Interceptor

DrainlFrench

This

closure alternative

balances lower cost with leachate

collection

and is

designed

to

prevent

off-site

migration

of

groundwater

to the south

Adjusted

standards

would be

required

to

implement

this closure alternative

Closure Alternative

No

Earthen Final

Cover This closure alternative

represents

the

lowest

cost alternative

for closure of Pond

and would

require

adjusted

standards

to

seek relief from several sections of

Part 811 and Part 81

4.302b

Closure Alternative

No

Pozzolanic

Fly

Ash Final Cover This closure alternative

provides equivalent

effectiveness

to

Closure

Alternative

No

and has the added benefit

of

providing

renewed

capacity

for the active

Pond

fly

ash

impoundment

This

alternative

would

require adjusted

standards to seek relief from several sections of Part

811 and Part

814.302b1

utilizing technology

and

construction

techniques substantially

similar

to those

promulgated

in 35 IAC Part 816

Alternative

Standards for Coal

Combustion Power

Generating

Facilities Waste

Landfills

Surface water

management

was

considered

for each of the selected alternatives

The

optimal

alternative

routes surface water east toward the Wabash River and

west

toward

drainage

collection

pond

Costs for each of the closure alternatives

and the alternate final

cover are summarized

below

Closure Alternative

No

has the

highest

initial

capital

cost

$6.8

million

and

highest

operating

and maintenance

cost $3.1

million

over 30

years

based on 2003 dollars Ease

of

implementation

and

performance

are not

concerns as

the remedial

components

consisting

of

geosynthetic cover

leachate

collection

via an

interceptor

drain/trench

and

groundwater

extraction

in the

deep

alluvial

aquifer

are demonstrated

technologies

that are

widely

available

Closure Alternative

No

provides significant cost

savings

versus Alternative

No

in

up-front

capital

cost $4.7

million

and

lower

operating

and maintenance

cost

$1.1

million over 30

years

Predicted

performance

effectiveness

and

reliability

along

the

south

impoundment boundary

are

nearly equivalent

to Closure

Alternative

No

Closure Alternative

No

represents

the lowest cost alternative

with

significant savings

in

up-front

capital

$4.2

million

and low

operating

and maintenance cost

$0.2

million

over

30

years

Groundwater

transport

modeling suggests

that

an earthen cover

may

provide performance

and

long

term

effectiveness

along

the south

property boundary

similar to Closure Alternatives

No

and

Closure Alternative

No

provides performance

reliability

and effectiveness

equivalent

to the final covers

proposed

for each alternative

at

mid-range

capital

cost for final cover

1375 Alternatives

Analysis

Report-Final

NATURAL

ES-2

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

EXECUTIVE SUMMARY

$4.5 million

and with low

long

term

operating

and maintenance

costs

$0.2

million over

30

years

An

adjusted

standard would

be

required

to

gain regulatory

acceptance

for the

technology

for construction

of

pozzolanic fly

ash

cover

however

regulatory

precedent

exists for similar

construction

of

final

covers

35

IAC Part

816

Each of the four alternatives

is

potentially appropriate

for the site with similar

performance

and

effectiveness

and reflects

range

of

approaches contingent

on

capital expenditure

and

varying approval

of

adjusted

standards

with the Illinois PCB

However

Closure Alternative

No

the Pozzolanic

Fly

Ash

Cover

provides

the best

balance of

capital expenditure

and

pursuit

of

adjusted

standards

for the

following

reasons

Groundwater

transport modeling

indicates

that

pozzolanic fly

ash final cover

system

will have similar

performance

and effectiveness

as

cover

system

that meets the

requirements

of Section 811.314

e.g geosynthetic

final

cover

Groundwater

transport modeling

indicates that the

pozzolanic fly

ash final cover will

achieve the Class Groundwater

Quality

Standards

along

the south

property boundary

MW-I IR

within

approximately

16

years

which

compares

favorably

to the

ten-year

period predicted

for Alternative

No

This alternative should

satisfy long-term

regulatory

concerns with off-site

migration

No leachate

management

is

proposed along

the east

impoundment boundary

However

groundwater

impacted by

ash

leachate

discharges

to the Wabash River and does

not

threaten

any downgradient groundwater

receptors

Based

on

this

discussion

pursuit

of an

adjusted

standard for the

applicable

groundwater

quality

standards

along

the east

edge

of

the zone of attenuation is warranted

Regulatory precedent

exists

35

JAC

816

for construction

of

pozzolanic

fly

ash final

cover

system

using

substantially

similar

technology

and

construction

techniques

Significant

cost

savings

may

be realized

through

construction

of

pozzolanic fly

ash

final cover

by providing

additional

capacity

for

fly

ash in

Pond

Based

on this

discussion

pursuit

of

an

adjusted

standard

for construction

of

pozzolanic fly

ash final

cover is warranted

1375 Alternatives

Analysis Report-Final

NATURAL

ES-3

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

TABLE OF CONTENTS

INTRODUCTION

1-1

1.1

Background

1-1

1.2

Investigation

Time Line

1-2

1.3

Alternatives

Analysis

Objectives

and

Approach

1-3

SUMMARY OF SITE CONDITIONS

2-1

2.1

Supplemental

On-Site

Investigation

October 2001

2-1

2.1.1

Advancement of Soil

Borings

2-1

2.1.2

Installation

Abandonment of

Monitoring

Wells

2-2

2.1.3

Hydraulic Testing

2-3

2.2

Supplemental

Off-Site

Investigation

April

and

May

2004

2-3

2.2.1

Installation of

Monitoring

Wells

2-3

2.2.2

Hydraulic Testing

2-5

2.3

Groundwater

Sampling

and

Analysis

2-5

2.4

Summary

of

Hydrogeology

and Groundwater

Quality

2-6

2.4.1

Distribution

of Coal Ash Fill

2-6

2.4.2

Hydrogeology

2-6

2.4.3

Evaluation of

Daily

Groundwater and River Elevation Data

2-7

2.4.4

Groundwater

Quality

and Parameters of Concern

2-7

2.4.5

Background

Concentrations

2-7

2.4.6

Groundwater

Quality

2-9

2.5

Exposure Pathways Groundwater Soil

Surface

Water

2-10

IDENTIFICATION OF LEACHATE MANAGEMENT AND FINAL COVER ALTERNATIVES3-1

3.1

Identification

of

Alternatives Overview

3-1

3.2

Leachate

Management

and

Deep

Alluvial

Aquifer

Source Control Alternatives

3-2

3.2.1

Selection of Alternatives for Initial

Screening

3-2

3.2.2

Site

Monitoring

with No Leachate

Collection

3-2

3.2.3

Groundwater Extraction

Leachate Collection Alternatives

3-3

3.2.4

Source Control of

the

Deep

Alluvial

Aquifer

3-3

3.2.5

Ash Stabilization

3-4

3.2.6

Ash Removal and

Disposal Recycling

at an Off-Site

Facility

or

Beneficial

Reuse

3.4

3.2.7

Ash

Impoundment

Reconstruction

3-5

3.2.8

Containment

Using

Low-Permeability

Barrier Wall

3-5

3.3

Final Cover Alternatives

3-6

3.4

Surface Water

Management

Alternatives

3-7

3.5

Initial

Screening

Criteria and Results

3-8

1375 Alternatives

Analysis Report-Final

NATURAL

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

TABLE

OF CONTENTS

3.6

Treatability Study

for

Pozzolanic

Fly

Ash Final Cover

3-10

MODELING

AND

EVALUATION OF SELECTED ALTERNATIVES

4-1

4.1

Purpose

4-1

4.2

Model

Approach

4-2

4.2.1

HELP

Modeling

4-2

4.2.2

MODFLOW/MT3DMS

4-3

4.2.3

Criteria for Evaluation of

Modeling

Results

4-3

4.2.4

Simulation of Final Cover and Leachate

Management

Alternatives

4-3

4.2.5

Simulation of

Deep

Alluvial

Aquifer

Source Control Alternative

4-4

4.3

Modeling

Results and Recommendations for Alternative

Assembly

4-4

4.3.1

Modeling

Results Final Cover Alternatives

4-5

4.3.2

Modeling

Results Final Cover Alternatives

Combined with Leachate

Management

Alternatives

4-5

4.3.3

Recommendations for

Alternatives

Assembly

4-6

ASSEMBLY AND DETAILED

ANALYSIS OF CLOSURE ALTERNATIVES

5-1

5.1

Assembly

and Selection Rationale

5-1

5.2

Detailed

Analysis

of Closure Alternatives

5-2

5.3

Recommended

Closure

Strategy

5-3

5.4

Recommended

Pre-Design

Evaluation and Field

Testing

5-4

REFERENCES

6-1

FIGURES

Figure

1-1

Site Location

Map 1375-A03

Figure

1-2

Site Plan

1375-61-B30

Figure

2-1

Geologic

Cross

Sections

1375-61-BOl

Figure

2-2

Groundwater

Elevation

Contours

September

14

2004

1375-61-A04

Figure

2-3

Groundwater Elevation

Contours

October

26

2004

1375-61-A03

Figure

2-4

Groundwater

Elevation

Contours

November

16

2004

1375-61-A02

Figure

2-5

Comparison

of Groundwater

Elevation Data to Well

Pumpage

September-

November 2004

Figure

2-6

Boron Concentration

in

Background

Wells

Figure

2-7

Sulfate Concentration

in

Background

Wells

Figure

5-1

Alternative No

PVC Final Cover With East

and South

Interceptor

Drain/Trench

and

Deep

Groundwater Extraction

System 1375-61-BO3C

Figure

5-2

Alternative No

Earthen Final Cover With

South

Interceptor

Drain/Trench

1375-61 -BO4C

Figure

5-3

Alternative No

Earthen Final Cover or Pozzolanic

Fly

Ash

Final Cover

1375-61

-BO5C

1375

Alternatives

Analysis Report-Final

NA11JRAL

ii

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

TABLE OF CONTENTS

APPENDICES

Soil

Boring

and Discrete Groundwater

Sampling

Data

Monitoring

Well

Locations Elevations

Depth

to

Bedrock

and Screened

Formation

Monitoring

Well

Completion

Details

Monitoring

Well

Slug

Test Results

Background

Statistical

Summary

Groundwater

Concentration

Results from

Monitoring

Wells

Initial

Screening

of Leachate

Management

and Final Cover Alternatives

Areal Extent and Volumes of

Unsaturated and Saturated Ash in Pond

Final Cover Alternatives Material Balance

Analysis

Comparison

of Recommended

Mix

Designs

to Performance Goals and Cost

Sensitivity Analysis

Selected Alternatives for Groundwater Flow and

Transport

Modeling

Groundwater Flow

and

Transport

Model

Results

Closure Alternatives Cost

Summary

Detailed

Analysis

of Closure

Alternatives

Appendix

Appendix

Appendix

Appendix

Appendix

Appendix

Supplemental

Site

Investigation Appendices

A-i

Soil

Boring Logs

A-2

Monitoring

Well

Completion Reports

and Abandonment

Log

A-3

Slug

Test

Data

A-4

Groundwater

Sampling

SOP

AEG

Alternative Cost

Summary

Sheets

Treatability

Study

for

Pozzolanic Final

Cover

System

C-i

Conceptual Development

of Pozzolanic

Cap

for Closure of Basin

at

The

Hutsonville Power Station

C-2

VFL Cost Data

Groundwater

Transport Modeling

Results and

Supporting

Documentation

Statistical Calculations

Groundwater

Velocity

Calculation

1375 Alternatives

Analysis

Report-Final

111

NATuRAL

RESOURCE

TECHNOLOGY

TABLES

Table 2-1

Table 2-2

Table 2-3

Table 2-4

Table 2-5

Table 2-6

Table 3-1

Table 3-2

Table 3-3

Table 3-4

Table 4-1

Table 4-2

Table 5-1

Table 5-2

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

INTRODUCTION

1.1

Background

Ameren

Energy Generating operates

the Hutsonville Power

Station

in

Crawford

County

Illinois

Figure 1-1

The

power

station is located

on

the

west

bank

of the Wabash River

mile north of the

city

of Hutsonville SW

Section

17

Township

8N Range 11W

The coal fired

power plant

has been in

operation

since the

1940s There are

currently

two units

operating

at the

plant completed

in 1953

unit

and 1954

unit

with combined

generating capacity

of 164 MW

Fly

ash from the

operating

units

is collected

by

an

electrostatic

precipitator

and sluiced

to

12-acre lined ash

impoundment Pond

Figure

1-2

which

was

constructed in 1984 Bottom ash is

sluiced to

separate pond

and

eventually

recycled

Sluice

water

from

Pond

is routed

through

4.2-acre lined interim

pond Pond

constructed

in

2000

before

discharge

to the Wabash River via NPDES

permitted

outfall

002

IL0000 175

Sluice

water from the bottom ash

pond

is routed

through

1.7-acre

drainage

collection

pond Pond

constructed in

2000

and Pond

before

discharge

to the Wabash River via the

same

outfall

The site also has

22-acre unlined ash

impoundment Pond

which was constructed in 1968 This

impoundment

was the

primary

ash

management

unit

prior

to

construction

of Pond

in

1984

and was

used as

secondary settling pond

from 1984

through

construction

of Pond

in 2000

It has been inactive

since 2000

although precipitation

and flood backwater have accumulated

in the

impoundment

at

times

resulting

in

ponded

conditions

Groundwater

quality

has been monitored at this

facility

since 1984 Concentrations of boron and sulfate

at several

monitoring

wells exceed the 35 Illinois

Administrative Code

IAC

811.320

groundwater

quality

standards

Section

811.320

applicable

background

concentrations

and the Illinois Class

groundwater

quality

standards Boron and sulfate

are indicator

parameters

for coal ash leachate In

response

to

these

findings

Ameren Services contracted

Science

Technology

Management

Inc

STMI

and Natural Resource

Technology

Inc

NRT

to

perform

Hydrogeologic

Assessment that

was

completed

in

August

1999

The

Hydrogeologic

Assessment identified

correlation

between shallow

groundwater

quality

elevated

boron and sulfate concentrations

in

groundwater

and

potential

leachate

sources

namely

the former ash

laydown

area which was

excavated

prior

to

construction

of

Ponds

and

and the unlined ash

1375 Alternatives

Analysis Report-Final

NATURAL

1-1

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

INTRODUCTION

impoundment Pond

Boron and sulfate are

migrating

east

towards the

Wabash River

however

there

are no

groundwater

supply

wells in the shallow sediments between the unlined ash

impoundment

and the

Wabash River

There are four

groundwater

supply

wells within

mile of the

site

all

finished in

deep

alluvial sand and

gravel aquifer

in the Wabash River

valley

Two wells

are

directly

east

of the unlined

impoundment

and

are

used for

plant water

and two wells are southeast

of the

impoundment

and used for

irrigation

water

Groundwater

quality

data from

monitoring

well

MW-14

which is

directly

southeast

of the unlined ash

impoundment

and is screened in the

deep

alluvial sand and

gravel

indicates evidence of ash

impoundment impacts

in that

aquifer

based

on

comparison

to Section 811.320

applicable background

concentrations

However

concentrations

are

lower than

the Illinois Class

groundwater

quality

standards

1.2

Investigation

Time Line

NATURAL

RESOURCE

TECHNOLOGY

1999

The

Hydrogeologic

Assessment

report

characterizes

hydrogeology

at the site and identifies

Pond

and an ash

laydown

area as the sources

of shallow

groundwater

quality impacts

at the

site No evidence of

groundwater

impacts

are found in the

deep

alluvial

aquifer

2000

Groundwater

Model Evaluation

of

Impoundment

Closure

Options

concludes that

dewatering

of Pond

will reduce leachate

loading

to the Wabash river

by

more

than

80

percent

however no

capping option

will result in

attainment of Class

groundwater

quality

standards

due to

continuing groundwater

flow

through

ash

deposited

below the water

table

2000

Ash in the former ash

laydown

area is

removed

Ponds

and

are constructed

and

Pond

is

permanently

removed from service

2001

supplemental

site

investigation

is

performed

for this

alternatives

assessment

Additional

monitoring

wells are installed in the

deep

alluvial

aquifer

There is

no evidence of ash

impacts

in the

deep

alluvial

aquifer

2002

Research is

performed

for

an

innovative

approach

to

capping

Pond

2003

The first draft of this

Alternatives

Assessment

report

and

petition

for

adjusted

standards

is

completed

After

meeting

and discussion of

preliminary

results

IEPA determines that

Groundwater

Impact

Assessment is

required

for the

deep

alluvial

aquifer

Spring

After

delays

in

obtaining

site access on off-site

private

property

an

investigation

is

performed

2004

to characterize

hydrogeology

in the

deep

alluvial

aquifer

2005

During

data

review it is determined that MW-14 has elevated boron and

sulfate

concentrations

In

response

to this

finding

it is determined that the Groundwater

Impact

Assessment is no

longer necessary

and

plan

is

developed

to

sample

the off-site wells to

determine

whether or not

groundwater

impacts

in the

deep

alluvial

aquifer

extend to the

south

however

flood conditions

on

the

Wabash river

delay

data collection Work

commences on

completion

of this Alternatives

Analysis

1375 Alternatives

Analysis Report-Final

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

INTRODUCTiON

1.3 Alternatives

Analysis Objectives

and

Approach

The

primary objective

of the alternatives

analysis

is to evaluate

and make recommendations

on

leachate

management

and

final

cover alternatives

for closure of the unlined ash

impoundment

Pond

based

on

technical and

cost

considerations

Alternatives

analysis objectives

herein referenced

as

Closure

Objectives

were

identified for

protecting

human

health and the environment for both the

parameters

of

concern POCs

identified in the

Hydrogeologic Assessment

and

exposure

pathways

in accordance with

applicable

environmental standards

Site-specific

considerations

for

establishing

appropriate

Closure

Objectives

for Pond

include

proximity

of

the Wabash River

to

Pond

hydrogeology

and

groundwater

quality

in the

vicinity

of Pond

and the

presence

or

absence

of

exposure pathways

for identified POCs

groundwater

soil

and surface

water

Standards are

promulgated

for the

design

and

operation

of solid

waste landfills under 35 Illinois

Administrative Code

IAC

Parts 810

to

816 Based

on

review of

these

regulations

and on

site-specific

considerations

the

following

Closure

Objectives

were

developed

Manage groundwater

quality

to meet the

requirements

of Section

811.320 and

Construct

final

cover

system

that

meets

the

requirements

of Part 811 or an

adjusted

standard

approved by

the Illinois Pollution Control Board

PCB

Specific

parameters

for

performing

the alternatives

analysis

were

developed

on

the basis of

the results

of the 1999

Hydrogeologic

Assessment the Groundwater Model Evaluation

of impoundment

Closure

Options

dated

January 2000

and

supplemental investigations

performed

for this

analysis Section

additional

groundwater

flow

and

transport modeling

of alternatives

Section

and

considerations

for

pursuing adjusted

standards

through

the Illinois PCB The

range

of

technological

applications

considered

included conventional and innovative

alternatives

Tables

3-1 3-2 3-3 4-1 4-2 5-1

and 5-2 summarize the

findings

of this alternatives

analysis

which are

described in Sections

and

This alternatives

analysis

process

was

developed

to meet the

substantive

regulatory

requirements

of 35 IAC Part 811 and is divided into four

major

stages

as follows

Initial

Screening

This

stage

consisted of

three

steps

First site

specific

Closure

Objectives

were established

to address

parameters

of

concern

and

exposure pathways

Section

3.1

Second closure alternatives

to meet these

objectives

were

divided into

three

categories

leachate

management

alternatives

final

cover

alternatives

and

surface

water

management

alternatives

Third

these alternatives

were

initially

screened

on

the basis of construction

implementation feasibility effectiveness

and cost

Table

1375

Alternatives

Analysis Report-Final

NATURAL

1-3

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TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

INTRODUCTION

3-1

Alternative

specific rough

cost estimates were

developed

at this

stage Appendix

Groundwater

Transport Modeling

and Secondary Effectiveness

Evaluation The closure

alternatives

that met the initial

screening

criteria

were combined into model scenarios for

prediction

of their effects

on

groundwater

quality using

calibrated

groundwater

flow

and

transport

model

Table

4-1

These results

were

used

to reduce the number of

alternatives

that

would be

subject

to the next

step

of detailed

analysis

Table 4-2

Assemble

Alternatives

for Detailed

Analysis Specific

closure alternatives

that

met

the

secondary

effectiveness

screening

criteria

were

evaluated with

respect

to

meeting

the

Closure

Objectives

regulatory

acceptance

and relative cost

Section 5.1

From these

alternatives

four

were

selected that

represented

range

of

closure alternatives

on the

basis of the

following

criteria

an alternative

that

meets

the

requirements

of 35

IAC

Parts 811 and

814

an

alternative

that

meets

the

effectiveness criteria

Section 4.2.3

with

adjusted

standards

and includes leachate

collection

an alternative

that

represents

the lowest cost alternative and meets the effectiveness criteria

Section 4.2.3

with

adjusted

standards

and

no

leachate

collection and

an alternative

that meets the

effectiveness

criteria

Section 4.2.3

with

adjusted

standards

and

meets

the intent of

35 JAC Part 811 and 814

through

utilization

of

technology

and construction

techniques

substantially

similar to those

promulgated

in 35 IAC Part 816

Alternative

Standards for

Coal Combustion Power

Generating

Facilities Waste

Landfills

Detailed Analysis The four final closure alternatives

were

further evaluated in

terms of

total

cost Table

5-1

and in

general

accordance with the criteria listed in Table 5-2 to

develop

final recommendation

for the site These criteria include

the

degree

to which

the

proposed remedy

is

protective

of

human health and the

environment

short and

long

term

effectiveness

ease of

implementation

performance

reliability potential impacts

time-frame for

completion

cost

and

institutional

requirements

required

for

regulatory

acceptance

1375 Alternatives

Analysis Report-Final

NATURAL

1-4

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE CONDITIONS

Hydrogeology

and

groundwater

quality

were

thoroughly

characterized

in the

Hydrogeologic

Assessment

report

Additional

field

investigation

was

performed

for this

project

to

upgrade

the

monitoring

well

system surrounding

Pond

characterize

the

deep

alluvial

aquifer

and

to

collect detailed

information

specific

to

the alternatives

assessment

2.1

Supplemental

On-Site

Investigation

October 2001

The first

supplemental

site

investigation

was

performed

from

October

to

2001 The

scope

of work

included

advancement of

six soil

borings SB-101

through

SB-106

installation of

one additional

monitoring

well

MW-14

and one

temporary monitoring

well

TW

and

abandonment of

monitoring

well MW-Il and

replacement

with MW-I 1R In

addition hydraulic

conductivity

tests

were

performed

on

selected

new

and

existing monitoring

wells

2.1.1 Advancement of Soil

Borings

An all-terrain drill

rig equipped

with

-inch

hollow-stem

augers

was

used to

perform

all soil

borings

direct

push sampling

and

monitoring

well installations

at

the

site

total of nine soil

borings

were

advanced

at the

site

two of which

were

converted into

permanent monitoring

wells

MW-I

1R and

MW-14

and one that was converted into

temporary monitoring

well

TW

Soil

borings

SB-I01

through

SB-103 were advanced

to better characterize

the

type

and

extent

of

geologic

materials

surrounding

Pond

Soil

borings

SB-104

through

SB-106 were advanced

north of the

ash

impoundment

to find

suitable location for

background

monitoring

well within the

deep

alluvial sand and

gravel

The

latter

borings

were drilled in the

only

accessible locations that

were not

downgradient

of the ash

impoundments

However

shallow bedrock

was encountered at all three

locations

and

natural coal

seam was encountered

at

SB-106

indicating

that

the Wabash River was over the west side of the

valley

in

this area As

result an

upgradient

well could

not be installed within the

deep

sand and

gravel

of the

valley

Geologic

materials at all soil

borings were

logged every

feet

using

2-inch diameter

by

2-foot

long

split-barrel sampler

The soil

borings

were advanced

to

bedrock to

design depth

or

adjusted

in the field

as

necessary

ranging

from

feet to 39

feet below

ground

surface

Table

2-1 Upon completion

of

1375 Alternatives

Analysis

Report-Final

NATURAL

2-I

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE CONDITIONS

sampling

all soil

borings

were

backfilled

with

bentonite

chips

and

hydrated or

converted into

monitoring

wells

Appendix

A-I

During

advancement

of soil

borings

SB-102

MW-I

and

TW

hydro-punch

discrete water

sampler

was

used to collect

groundwater

samples

at

targeted depths Table 2-1

The

purpose

of the discrete water

sampling

was to determine the

geologic

formations

where ash leachate

was most

prevalent

and better

assess

the

feasibility

of

leachate

collection

surrounding

Pond

Discrete

samples

were

designed

to

target

groundwater

in the shallow

silty

alluvial sediments

immediately

below the silt interface

at

the

top

of

the

deep

alluvial

sand

and

at

depth

in the

deep

alluvial sand

minimum of

10 feet below the

silty

alluvium

This

analysis

showed

decreasing

concentrations

with

depth

however

interpretation

of results

was

uncertain due

to

potential

vertical

migration

within the borehole

2.1.2 Installation

Abandonment of

Monitoring

Wells

Monitoring

well MW-14

was

installed

to

support

the

creation of

groundwater

monitoring

network

surrounding

Pond

The

screen

of MW-14 is

designed

to monitor the

deep

alluvial sand and

gravel

aquifer immediately underlying

the shallow alluvial silt and

clay

unit The

temporary monitoring

well

TW

was installed to

provide

additional

data for characterization

of the

deep

alluvial

aquifer

The screen

of TW monitors the

deep

sand and

gravel aquifer

at

depth

of nine feet below

the silt and

clay

unit

Monitoring

well MW-hR

was

installed

to

replace monitoring

well

MW-Il

which was

yielding

anomalous results

Monitoring

well MW-I 1R

was

screened in

unlithified materials

atop

shallow

bedrock

All

of the wells were constructed with 2-inch inner diameter

I.D

schedule 40 Pvc

pipe

flush-threaded

to

foot

MW-

14 and

TW or

10 foot

MW-Il

long

section of

0.010-inch factory

slotted PVC well

screen

Tables

2-2 and

2-3

From bottom to

top

the

monitoring

wells

were

completed

with

filter

pack

consisting

of uniform

silica

sand to at least one foot above the well

screen

one-half to two feet of

fine

sand

and

minimum of

two feet of

hydrated

bentonite

chips

to

near

ground

surface

Appendix

A-2

All of the

monitoring

wells were finished with

stick-up style locking

steel

well

protective casings

surrounded

by

set of steel

bumper posts

Following

well

completion

all

wells were

developed

to

remove

sediment and

restore

groundwater

flow

surrounding

the well

1375 Alternatives

Analysis Report-Final

NATURAL

2-2

RESOuRCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY

OF SITE CONDITIONS

2.1.3

Hydraulic Testing

Single

well

recovery

tests were

performed

on

newly

installed wells and wells that

were not

previously

tested Wells

MW-I MW-14

MW-hR

and TW were tested Well MW-8 could

not be tested due to

slow

recovery

after

groundwater

sampling

Data

were

collected

using

an in-Situ HermitlM

datalogger

and

pressure

transducers

Pressure transducers and

disposable

bailers were

placed

in the

wells

and time

was

allowed for

groundwater

to reach

equilibrium

After

groundwater

had returned

to static water

level

the

transducers

were linked to the

datalogger

and set to

begin

slug

of

water was removed

using

disposable

bailer with

approximately

0.037

ft3

of

displacement

for wells MW-I

and MW-IIR

Two

disposable

bailers

0.074

ft3

of

displacement

were

joined

together

and used to

remove

the

slug

at

well

MW-I

and three bailers

0.11

ft3 of

displacement

were used at TW due to the static head of the

water

table and the screened formation

Test duration was about 25

minutes or

until water had returned

to

static level

Upon

test

completion

the data

were

downloaded

and

processed using

the

Aqtesolv

software

Data were

interpreted using

the Bower-Rice

1976

method

Table 2-4

Appendix A-3 Slug

test results

from

wells

MW-14

and MW-I JR could not be

interpreted

due to

an

equipment

malfunction

2.2

Supplemental

Off-Site

Investigation April

and

May

2004

The

supplemental

off-site

investigation

was

performed

from

April

26 to

May

13

2004

The

scope

of

work included

installation of seven

temporary monitoring

wells

TW-1

15S

through TW-120

deployment

of downhole

datahoggers

for continuous

groundwater

elevation

observations in TW-1

15S

TW- 11

SD

and TW-

118

performance

of

single

well

recovery slug

tests on new wells to characterize

aquifer

characteristics

near the

monitoring points

survey

of all

new wells

and

collection

of

groundwater

elevation data

at

all

new and

existing

wells In

addition

pumpage

data for the

two

plant

water wells

was

collected and

analyzed

to determine the effect of

pumpage

on

the

nearby monitoring

wells

TW-1

15S and TW-I

15D

2.2.1

Installation of

Monitoring

Wells

An all-terrain drill

rig

equipped

with -inch hollow-stem

augers

was used to

perform

all

monitoring

well installations

during

the 2004

supplemental investigation

Geologic

materials at all well locations

were

logged

continuously

to the extent

practicable

using

2-inch

diameter

by

2-foot

long split-barrel

sampler

Rock cores were collected from

borings

TW-115D

TW-1

16 and TW-1 19

utilizing

diamond

tipped

rock core barrel Each of the wells

was

constructed

with 2-inch inner diameter

I.D

schedule 40

1375 Alternatives

Analysis Report-Final

NATURAL

2-3

REsOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE CONDITIONS

PVC

pipe

flush-threaded

to

5-foot

long

section of 0.0

10-inch

factory

slotted PVC well screen

Tables

2-2

and

2-3

From bottom to

top

the

monitoring

wells

were

completed

with

filter

pack consisting

of

uniform silica

40

sand to at least

foot above the well

screen

foot of fine

sand and

minimumof feet of

hydrated

bentonite

chips

to near

ground

surface

Appendix A-2

All of the

monitoring

wells

were

finished with

stick-up style locking

steel

protective

casings

TW-1 15S and TW1I5D

were

drilled

directly

north of

EW2 as close to the river as

possible Figure

2-1

to be used in

conjunction

with

existing

well MW-7D and

pumpage

records from EWI and EW2 to

determine the effects of

plant

pumpage

on

groundwater

flow within the

deep

alluvial

aquifer

TW-l 15D

was

drilled

to

bedrock and

cored 15 feet into the

shale

to

total

depth

of 105 feet below

ground

surface

bgs

The borehole

was

then backfilled

with

bentonite to

approximately

88 feet

bgs

and the well

was

screened near the base of the

deep

alluvial

aquifer

to characterize

the vertical flow within the

aquifer

TW-l l5S was blind drilled to 36 feet and screened

near

the

top

of the

aquifer

TW-1

16 and TW-1 17 were drilled

approximately

one-half mile

south/southeast

of the

impoundment

on

the west side of the river

TW-116

farther from the

river was

drilled

to

depth

of 79.2 feet

bgs

cored

19 feet into

shale

backfilled

with bentonite

to 55 feet

bgs approximately

five

feet above the

bedrock

and then the

augers

were rotated backwards

out of the hole to allow the sand and

gravel

to

collapse

The

well screen

was

set at 30 feet

bgs

in

clayey

sand

to

gravel

at what was assumed to be the

top

of the

deep

alluvial

aquifer Subsequent

review of the

lithology

determined that TW- 116 is

actually

screened in the

fine-grained

alluvium above the

deep

alluvial

aquifer TW-117

closer

to

the

river was drilled to

total

depth

of 90.5 feet

bgs six

inches into

shale

the

augers

were

then rotated

backwards out of the borehole

and the borehole

was

allowed

to

collapse

to

depth

of 21 feet

bgs

The well

screen was set at

20

feet at

the same

approximate

elevation

as

TW-1 16

to allow the two wells to

serve as

downgradient groundwater

elevation

calibration

points

and

as

lithologic

controls

on

the

configuration

of the bedrock

valley

TW-118 TW-119 and TW-120 were drilled east of the river

Only

TW-119 was drilled to

bedrock as

bedrock

depth

at TW-118 was assumed to be similar

to

TW-115D

and TW-120 was assumed to be similar

to TW-119

TW-l 19 was cored 20 feet into

shale

to

total

depth

of 100 feet

bgs

The borehole

was

sealed with bentonite

to 75 feet

bgs

approximately

five feet above

bedrock The hole was then allowed to

collapse

as the

augers

were rotated out to

depth

of 21 feet

bgs

All three wells

were screened near the

top

of the

aquifer

1375 Alternatives

Analysis Report-Final

NATURAL

2-4

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE CONDITIONS

2.2.2

Hydraulic Testing

Single

well

recovery

tests were

performed

on

newly

installed wells Well

TW-120 could not be tested

because

the

depth

to

groundwater

was

greater

than the

length

of the

pressure

transducer

cord Data were

collected

using

laptop

and MiniTrollTM

pressure

transducers

Pressure transducers

were

placed

in

the

wells and the

tests started

0.061

ft3

steel

slug

was inserted

and time

was

allowed for

groundwater

to

reach

equilibrium slug-in

test

After

groundwater

had returned

to

static

water

level

the

slug

was

removed and the water column left to

equilibrate again slug-out test

Test duration was

to 10 minutes

Upon

test

completion

the data were downloaded and

interpreted

using

the Bower-Rice

1976

method as

coded

in

the

Aqtesolv software

with the

exception

of TW-1 15S and TW-1

18

which

were

interpreted

using

the Butler

1998

analysis

method

Table 2-4 Appendix

A-3

The MiniTrollTM

dataloggers

were

then

deployed

in

wells

TW-l

15S

TW-1

15D

and TW-1 18 for

continuous

groundwater

elevation observations

The

dataloggers

were set to take

pressure

head

readings

of the

height

of the water column above the transducers

every

hour

for six months

2.3 Groundwater

Sampling

and

Analysis

Groundwater

sampling

was

performed by

AEG

according

to their standard

operating

procedure

Appendix A-4 Analysis was

performed by

PDC laboratories

Analytical

methods are listed below

Analyte

Method

Alkalinity

Tot

SM

18

2320B

Boron

Tot

SW-846 6020B R0.0

Calcium

Tot

EPA 7140

prior

to

2002

SW-846 6020B

R0.0

since 2002

Hardness

total

SM

18

2340C

Manganese

Tot

243.1

prior to

2002

SW-846 6020B RO.O

since 2002

Sulfate

Tot

375.4

prior

to

2002

EPA 300.0 R2.1

since

2002

TDS

160.1

prior

to

2002

SM

18

2540C

since 2002

Only

one

of the

two in or

out

tests

is

reported

if the other test

yielded

non-linear

recovery

curve

1375 Alternatives

Analysis Report-Final

NAI1.JRAL

2-5

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE CONDITIONS

2.4

Summary

of

Hydrogeology

and

Groundwater

Quality

2.4.1 Distribution of Coal Ash Fill

Ash

at

the Hutsonville

Power Station has been

managed

in Ponds

and

In

addition

ash

was

placed

in

laydown

area between the southern

portions

of Ponds

and

The ash

laydown

area was

roughly

triangular

in

shape

and covered

an area

of about

acres

In

2000 all ash in the

laydown

area was

excavated

and the interim

pond Pond

and

drainage

collection

pond

Pond

were

constructed in that

general

location

Four

direct-push

probe

holes

GP-20 through GP-23

advanced

through

Pond

during

the 1999

Hydrogeologic

Assessment

indicated ash thickness

ranging

from

about 12 feet at the north end of the

impoundment

to 31 feet in the central

portion

of the

impoundment Section C-C

Figure

in the

Hydrogeologic

Assessment

report

Ash in the central and

southern

portions

of Pond

extended

as

much

as 16 feet below the normal water table elevation

2.4.2

Hydrogeology

The

upland portion

of the site is underlain

by

thin

less

than 20 feet

thick layer

of sand-rich

soil

which

is

underlain

by Pennsylvanian-age

sandstone

The lowland

portion

of the Site is in the

Wabash River

valley

and is underlain

by

90 feet of

alluvium

that coarsens downward The

upper

alluvium consists of

silt and

clay

with

thickness of

to

30 feet

Figure 2-1

The lower alluvium is sand and

gravel

which

extends to

Pennsylvanian-age

shale

at

60

to

90 feet

bgs

The water table

throughout

most of the

upland

area occurs within the surficial sand unit Groundwater

flow in this unit is

east

toward

the Wabash River

see Figures

and

in the 1999

Hydrogeologic

Assessment

report

Flow

velocity

in the

upper

sand

varies with

hydraulic

gradient

and

hydraulic

conductivity

and was

previously reported

at 150 to 240 feet

per year

The

water

table within the

Wabash River

valley

occurs in the surficial silt and

clay deposits

therefore

the

deep

alluvial

aquifer

is confined

Groundwater

flow in the

deep

alluvial

aquifer

on

the

Illinois side of the

river is east to

northeast

toward

the Wabash

River

Figures

2-2 2-3

and

2-4

typical

horizontal

gradient

in the

deep

alluvial

aquifer

south of the site

was

0.002 ft/ft

Appendix

Horizontal

groundwater

flow

velocity

was estimated to be

approximately

66

ft/yr

in the

deep

alluvial

aquifer

Appendix

The

relatively

low

velocity

is function of the fiat

gradients

in this formation

The

high

1375 Alternatives

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Report-Final

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---

SUMMARY OF SITE CONDITIONS

hydraulic conductivity

of

this formation

2.2

1O

to

1.6

10

cmls

combined with its thickness

indicates

highly

transmissive

formation

2.4.3

Evaluation of

Daily

Groundwater and River Elevation Data

Groundwater

elevation

in TW-l

5D

TW-1

15S and TW-1 18 were

continuously

measured2

and the

results

compared

to determine whether

or

not

power plant

pumpage

has

noticeable

effects on

groundwater

elevation in the

deep

alluvial

aquifer

There

was no

apparent relationship

between

plant

pumpage

and

groundwater

elevation

Figure

2-6

This

indicates that the

cone

of

depression

associated

with the

plant

wells is

small

as

might

be

expected given

the

high transmissivity

of the

deep

alluvial

aquifer

2.4.4 Groundwater

Quality

and Parameters of Concern

The

1999

Hydrogeologic

Assessment identified

boron sulfate

manganese

and TDS

as

parameters

of

concern

POCs

because their concentrations

in

groundwater

near Pond

exceeded Illinois Class

groundwater

quality standards

which were the

applicable

standards

for

this site at the time Boron and

sulfate are indicator

parameters

of coal ash

leachate

and

are

the

primary

POCs

Manganese

is

ubiquitous

in

soils

may

have

higher

concentrations

in soil than in coal

ash

and is

highly

sensitive

to

redox

conditions therefore

it is

not

reliable

indicator of coal ash leachate

High

TDS

may

be observed

at

sites where coal ash leachate

migration occurs

because

high

TDS concentrations

reflect elevated

concentrations of soluble ash constituents

such

as

calcium potassium sodium

and

sulfate however

other natural and

anthropogenic

sources

can cause

high

TDS concentrations

2.4.5

Background

Concentrations

Background

groundwater

quality

values

were calculated

in

anticipation

of site closure under Section 811

These calculations

were

performed using

data from

background

wells MW-I and

MW-b.3

Data

at these

wells

were

collected

beginning

in 1984

However review of these data found

anomalously high

results

for Boron in MW-

which

appear

to decrease over time

Figure 2-7

Sulfate concentrations

show

no

Due to an

equipment malfunction

continuous

data

were

only

available

for TW-1 15S after

September

2004

MW-10D

was not used because

it is finished in sandstone

1375 Alternatives

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---

SUMMARY OF SITE CONDITIONS

such

anomaly

and have

no

trend

Figure 2-8

As noted

previously

sulfate is also

an

indicator

parameter

for coal ash

leachate

and the absence of sulfate

suggests

that

the elevated

boron concentrations in MW-I

were not due to

migration

from the ash

ponds

Rather

these results

may

reflect

changes

in

agricultural

activity

in the

area.4

Trend

analysis

was

repeatedly performed using

the

Shapiro-Wilk test

retroactively

from 2005

i.e

based

on 2000 to 2005

data

then

based

on

data from 1999

to 2005 then based on 1998 to

2005 etc

This

analysis

indicated that there is

no

statistical

trend in boron

concentrations

in either

background

well since

1998

Appendix

Therefore

all

background

statistics for the

upper

aquifer

are calculated

using

data

collected after

January

1998

All statistical

calculations

were

performed using

the MANAGES software

EPRI 2002

Analyses

were

performed

for the

parameters currently

monitored

at Ponds

and

The data were first tested for

normality

and detection

frequency

There

were

few non-detects

in the

database

and

normality

varied

by

parameter

Based

on the

normality results

the

following background

tests were

performed

Tolerance interval at 99

percent

confidence

and 95

percent

coverage

for data with

normal distribution

TDS

Tolerance interval at 99

percent

confidence

and

95

percent

coverage

for data with

log-

normal distribution

boron

and

manganese

Non-parametric

tolerance interval

maximum concentration

for data that had

neither

normal

or log-normal

distribution

Background

statistical

analysis

results are summarized in Table

2-5

and the

adjusted

811.320

background

standards

are

compared

to

analytical

results in Table 2-6a

Background

data and statistical

print-outs

are

included in

Appendix

There are no locations

on

the

power

plant

property

where an

upgradient monitoring

well could be

screened in the

deep

alluvial

aquifer

The river

abuts the west side of the

valley

north of Pond

the

aquifer

does not extend west of Pond

and

Pond

extends to the southern

property boundary

As

discussed in Section

2.4

groundwater

flow in

this formation is

primarily

eastward toward the Wabash

River

Boron is

common constituent in

agricultural

fertilizers and

pesticides

which account for

percent

of the boron

consumed

in the United

States

Source USGS 2003

httpllminerals.usgs.gov/minerals/pubs/commodityIboronlboronmybo3

.pdf

1375 Alternatives

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

SUMMARY OF SITE

CONDITIONS

Nine

monitoring

wells

were

installed in the

deep

alluvial

aquifer

five on the

plant property

near Pond

MW-7D

MW-

14 TW

TW- 11

5S

and TW- 11

5D

one5

south of the

plant property

TW-

117

and three

east

of the

Wabash River

TW-118

TW-1 19 and

TW-120

Six

of these wells have been in

place

since

2004

TW-100

series

and do not have sufficient data for

statistical

analysis

and one

MW-14

shows

elevated

boron and

sulfate

concentrations

indicative

of ash

pond impacts

As

result

background

concentrations were calculated

using

two of the older

wells

MW-7D and

TW which are

hydraulically

downgradient

of the

impoundment

but

are not

impacted

by

power plant

activities

The

background

calculations

were

performed

using

the

same

approach

as for the shallow sand

Tolerance interval at 99

percent

confidence and

95

percent coverage

for data with

normal distribution

alkalinity

calcium

sulfate TDS

Tolerance interval at 99

percent

confidence

and 95

percent

coverage

for data with

log-

normal distribution

boron

Non-parametric

tolerance interval

maximum concentration

for data that had neither

normal

or

log-normal

distribution

Deep

alluvial

aquifer

background

statistical

analysis

results are summarized in Table

2-5

and

the

adjusted

811.320

background

standards

are

compared

to

analytical

results in Table 2-6b The

resulting

background

concentrations

were similar to those calculated for the

upper

sand

with the

exception

of

sulfate

which

was

considerably

lower

Table 2-5 Background

data and

statistical

print-outs

are

included in

Appendix

2.4.6 Groundwater

Quality

Boron concentrations

exceeded the

Section 811.320

applicable background

concentrations

and Class

groundwater

quality

standards

at

monitoring

wells

MW-6 MW-7 MW-8

and

MW-I

lR

which are

downgradient

of Pond

Table 2-6a

The

highest

boron concentrations

were

observed

along

the south

perimeter

of

Pond

MW-6

and

MW-1IR

and in the

shallow silt unit

downgradient

of Pond

MW-8

Sulfate concentrations exceeded the

applicable background

concentrations and Class

groundwater

quality

standards

at the same four wells

TW-1 16 is screened in

fine-grained

alluvium

just

above the

deep

alluvial

aquifer note

the

relatively

low

hydraulic

conductivity

value listed in Table

2-4

The sand

pack

for this

well extends into the

deep

alluvial

aquifer

and

it

is

valid

point

for

measuring groundwater

elevation in that

formation however

it will

not

yield samples

representative

of

groundwater

in the

deep

alluvial

aquifer

1375 Alternatives

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---

SUMMARY OF SITE CONDITIONS

Since

2002

sulfate and boron

were

detected

at concentrations

higher

than the 811.320

applicable

background

concentrations

at

monitoring

well MW-14

Table 2-6b

that is screened in the

deep

alluvial

aquifer although

these concentrations

are

lower than

Class

groundwater

quality

standards Ash

impacts

were not evident until 2004 when boron

concentrations

were

consistently

higher

than

mgfL

Sulfate and

boron concentrations are lower than 811.320

applicable

background

concentrations

at

well TW-

11 SS and

TW-1 15D

Boron

was

detected

at

concentration

higher

than

background

in off-site well TW-I

16

which is screened

in

clayey

sand to

gravel

near the base of the shallow

fine-grained

alluvium

However

sulfate

concentrations

in this well

are

low The lack of

sulfate

which is

more mobile than

boron

indicates that

the boron is from

different source than the ash

pond possibly

due to fertilizer

use

in

nearby agricultural

fields

similar

to the elevated

boron concentrations

noted in

Background

well MW-I

prior

to 1998

TW-l16 will be

replaced

with well nest screened in the

deep

alluvial

aquifer

TW-1 17 has low boron

and sulfate concentrations

The water

quality

results at TW-I 17 indicate that the ash

impacts

observed at MW-14 have not

migrated

to

the south

The

deep

alluvial

aquifer

does not extend west

or

north of the ash

impoundment therefore

the boron and sulfate observed in MW-14

are

migrating east

with the

general

direction of

groundwater

flow

and

discharging

with

groundwater

to the Wabash river

2.5

Exposure Pathways Groundwater Soil

Surface

Water

There

are no

groundwater

supply wells

other than the

plant

wells

between Pond

and the Wabash

River which is the ultimate

receptor

of

groundwater

impacted by

leachate

from

Pond

The

plant

wells

and two

irrigation

wells that

are

southeast

of

Pond

are

completed

in the

deep

alluvial

aquifer

in the

Wabash River

valley

which is

overlain

by

less

permeable

silt and

clay

sediments

As documented

previously groundwater

in the shallow

upland

sand and in the silt unit

downgradient

of

Pond

have elevated

boron and sulfate

concentrations

and therefore

represent

an

exposure

pathway

however

these formations

are

not utilized for

water

supply

The

deep

alluvial

aquifer

is utilized

as

drinking

water

supply

by

the

city

of

Hutsonville

approximately

mile to the south

However

groundwater

flow in

this

aquifer

is east toward the Wabash River

Figures

2-2 2-3 and

2-4

As

result

there are no

potable

water

supply

wells

other

than the two

plant

wells

situated

between Pond

and the

discharge point

for

groundwater

the

Wabash

River

The

plant

wells

1375 Alternatives

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---

SUMMARY OF SITE CONDITIONS

have low boron and sulfate concentrations and

do

not show evidence of

impacts

from

Pond

Table 2-6b

The

exposed

ash

in Pond

also

represents

direct

contact

exposure

pathway although access

to this

area

is

controlled

by

fence around

the

plant

so the

potential

risk is low As stated in Section

1.3

final

closure of Pond

will be in accordance with 35 TAC Part

811

and will include

final cover

system

that

meets

the

requirements

of Part 811 or an

adjusted

standard

approved by

the Illinois Pollution Control

Board

PCB

The

cover

will

eliminate the direct contact

pathway

1375 Alternatives

Analysis Report-Final

NATURAL

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TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF

LEACHATE

MANAGEMENT

AND

FINAL COVER ALTERNATIVES

3.1 Identification of Alternatives Overview

Consistent with the

requirements

of 35 IAC Sections 81 1.324 and

811.325

alternatives

designed

to

achieve

closure

for

Pond

were identified to

be

protective

of human health

and the

environment

address

identified

parameters

of concern and

exposure pathways

Section

2.5

and

achieve the

Closure

Objectives

stated in Section

.3 of this

report

as summarized

below

Manage groundwater

quality

to meet the

requirements

of Section

811.320

and

Construct

final cover

system

that meets the

requirements

of

Part 811 or an

adjusted

standard

approved by

the Illinois Pollution

Control Board

PCB

The Closure

Objectives

were selected to facilitate

an alternatives

analysis

that

meets

regulatory

requirements

and

adequately protects

human health and the environment

Alternatives

that

potentially

meet the Closure

Objectives

are divided into two distinct

categories

and

presented

in Table 3-1

Leachate

Management

and

Deep

Alluvial

Aquifer

Source Control

Alternatives

and

Final Cover Alternatives

Additionally

Surface Water

Management

Alternatives

have been

incorporated

with the alternatives

evaluation

as

they

will

be

critical

component

of

any

final

cover

alternative

selected for the

site General

surface water

management approaches

consist of

Routing

surface

water to the

existing

catch basin for collection

in the

drainage

collection

pond Pond

and eventual

discharge

to

the

Wabash River

Routing

surface water via overland flow to the Wabash

River or

combination of these

two

approaches

1375 Alternatives

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEA CHATE

MANAGEMENT AND FINAL COVER ALTERNATIVES

3.2

Leachate

Management

and

Deep

Alluvial

Aquifer

Source Control

Alternatives

3.2.1 Selection of Alternatives for Initial

Screening

Nine leachate

management

and

deep

alluvial

aquifer source

control alternatives

were selected for initial

evaluation

consisting

of the

following

Site

monitoring

with

no

leachate collection

Leachate

Management

Alternative

Three

variations

of

groundwater

extraction

leachate

collection

alternatives

Leachate

Management

Alternative

Source control for the

deep

alluvial

aquifer

via

groundwater

extraction

Source Control of

Deep

Alluvial

Aquifer

Ash stabilization

Leachate Management Alternative

Ash removal and

disposal recycling

at

an

off-site

facility

or beneficial reuse

Leachate

Management

Alternative

Ash

impoundment

reconstruction

Leachate Management Alternative

and

Containment

using

low-permeability

barrier wall

Leachate

Management

Alternative

and Source

Control of

Deep

Alluvial

Aquifer

These leachate

management

alternatives

were

initially

selected from

broad

range

of available

technologies

based on their use at similar sites and their

potential

to meet the Closure

Objectives

3.2.2 Site

Monitoring

with No Leachate Collection

This alternative consists of

groundwater

monitoring program

consistent

with the

requirements

of 35

IAC 811.319 No active leachate

collection

would be

performed as

part

of this

Leachate

Management

Alternative

Establishing

groundwater

monitoring

program

will be

required

as

component

of each

Leachate

Management

Alternative

discussed

below therefore costs for site

monitoring

have

not

been

separately

evaluated and will be included

as

part

of the

detailed

analysis

of leachate

management

and

final

cover alternatives

Section

1375 Alternatives

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEA CHA TE MANAGEMENT AND FINAL COVER ALTERNATIVES

3.2.3 Groundwater Extraction

Leachate Collection Alternatives

Groundwater extraction

alternatives

include wells or

drains

downgradient

of Pond

to

capture

groundwater

impacted by

ash leachate

Shallow

Groundwater

Extraction

Wells Combined with an Interceptor

Drain/Trench

This Leachate

Management

Alternative

would consist of network of vertical

groundwater

extraction

wells

designed

to

collect

impacted groundwater

from the shallow

silt and

clay

unit east of Pond

and

drain/trench

south of Pond

However this

alternative

would be difficult

to

effectively

and

efficiently

implement

because the

impacted

silt unit east of Pond

has low

hydraulic

conductivity

and the shallow sand

south of Pond

is

thin

and therefore

has low

transmissivity

Interceptor

DrainlTrench

This Leachate

Management

Alternative

would consist of

groundwater

interceptor

drain/trench

along

the entire east and south

perimeters

of

Pond

In the lowland

along

the east and south

perimeter

the

interceptor

drain/trench

would

extract

groundwater

within the silt and

clay

unit In the

upland

area

along

the south

perimeter

the

interceptor

drain/trench

would

capture

impacted

groundwater

above the

bedrock surface

Horizontal Groundwater

Extraction

Wells Combined with

Interceptor

Drain/Trench

This

Leachate

Management

Alternative

would consist of network of horizontal

groundwater

extraction

wells

designed

to

capture

impacted groundwater

along

the east

perimeter

of

Pond

The horizontal

wells could

be

designed

to

target groundwater

impacted by

leachate

in the

shallow silt and

clay Along

the south

perimeter an

interceptor

drain/trench

would be

designed

to

capture

impacted groundwater

in the lowland

silt/clay

and

upland

above the bedrock surface

For each of these Leachate

Management

Alternatives

collected

groundwater

would

be

directly

discharged

to the

drainage

collection

pond Pond

and/or the interim

pond Pond

for

management

through

the

plants

sluice water

system

and eventual

discharge

to the Wabash River via the

existing

NPDES

permit

3.2.4

Source Control of the

Deep

Alluvial

Aquifer

Containment

of

impacts

to

the

deep

alluvial

aquifer

would be achieved

by groundwater

extraction

through

vertical wells located

downgradient

of Pond

along

the southeast

corner As with the Leachate

Management

Alternatives

presented

above

groundwater

collected as

part

of this alternative

would be

directly discharged

to the

drainage

collection

pond Pond

and/or

the interim

pond

Pond

for

management through

the

plants

sluice

water

system

and eventual

discharge

to the Wabash River via the

existing

NPDES

permit

1375 Alternatives

Analysis Report-Final

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TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEACHATE MANAGEMENTAND

FINAL COVER ALTERNATIVES

Other in-situ alternatives

were

not considered for

source

control

of the

deep

alluvial

aquifer

because in-

situ

technologies

have not been identified for the

primary parameters

of concern

boron

and

sulfate

Containment

utilizing

low-permeability

barrier wall is

presented

below in Section

3.2.8

3.2.5 Ash Stabilization

Ash stabilization is

technology designed

to

micro-encapsulate

the ash in

cement-like matrix

monolith

to minimize the rate of

groundwater

infiltration and

leaching

of ash constituents

to

groundwater

Ash fill is

stabilized and solidified

using

one of several

reagents

delivered either via

soil

mixing

or

jet grouting technology

Once the ash is

stabilized

leachate

volume is

greatly

reduced

potentially eliminating

the need for active leachate

collection

Soil

mixing

utilizes

large

diameter

augers

to

12 feet in

diameter

that

mechanically

mix soils with

stabilizing

reagent

carried

by drilling

fluid Jet

grouting

utilizes small drill

rig

to advance

drill bit into

the

ash

through

which

grout

is

pumped

under

high pressure

As the drill steel is rotated

and

slowly

raised

cylindrical grout

column is created The

grout

injection

produces grout

columns

ranging

from

approximately

to

feet in diameter

key disadvantage

of this

technology

is

maintaining

the

continuity

and

integrity

of the

grout

column

Discontinuities

or

irregularities

in subsurface conditions

can

lead to

irregularity

in

grout

column diameter

Typically

conservative

overlapping

is

performed

to

achieve

uniform

coverage

3.2.6 Ash Removal and

Disposal Recycling

at an Off-Site

Facility

or

Beneficial

Reuse

Removal of ash from Pond

eliminates the

source

of ash leachate

impacting groundwater

at the site

Removal of ash

requires

excavation of considerable thickness

20

to 30

feet

of

ash Extensive site

dewatering

would be

required throughout

the

course

of the

project

For

purposes

of

evaluating

this

alternative

partial

removal

i.e

removal of saturated ash

only

was

compared

to removal of all ash from

the unlined

impoundment

Key design

and technical

considerations

for excavation

include

Excavated material

would be

disposed

off-site

For the

partial

removal

alternative

following

removal of

saturated

ash

capillary

break

would be created

by placing

relatively

free

draining

material such

as

self-compacting

gravel

at and above the

groundwater

interface

This

material

prevents

ash saturation due

to

capillary

rise from the

underlying

water table and also

provides

buffer to

prevent

resaturation

of the

ash

if

groundwater

elevation

increased

in the future Above the

capillary break

excavated ash would be

placed

as

backfill

to

grade

Above the ash

1375 Alternatives

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATiON OF LEA CHA TE MANAGEMENTAND

FINAL COVER ALTERNATIVES

backfill an

engineered

cover

would be

constructed to minimize surface water infiltration

through

the unsaturated ash

Extensive

engineering

controls that

could include water

misting

would be

required

for

managing fugitive

dust emissions

3.2.7 Ash

Impoundment

Reconstruction

Reconstruction of Pond

is identified as Leachate

Management

Alternative

since

the source of ash

leachate

would be

removed Reconstruction of this

impoundment

would

require

extensive excavation and

relocation

or off-site

disposal

of all ash The

impoundment

would then be reconstructed

as new

unit

designed

to

Separate

ash

from the water table

through

addition

of clean fill to raise the base of the

impoundment

above the

water table and

Reduce or eliminate

ash leachate

generation by retrofitting

the

impoundment

with

low

permeability

liner and

prevent downgradient migration

of

ash constituents

to

groundwater

Upon completion

of

impoundment reconstruction

removed ash could either be

replaced

or

the

unit could

be

operated

as

new

ash

impoundment

Final reconstruction

would be

completed

once the reconstructed

impoundment

reached

capacity

and

final

cover was

installed

as

discussed in Section

3.3

3.2.8 Containment

Using

Low-Permeability

Barrier Wall

Installation of

low-permeability

vertical

barrier wall is identified as Leachate

Management

and

Deep

Alluvial

Aquifer

Source Control Alternative The

Leachate

Management

Alternative

would be

designed

to

prevent

lateral

migration

of

ash leachate

via

groundwater

to the Wabash River The

Deep

Alluvial

Aquifer

Source

Control Alternative

would be

designed

to

contain

or

impede

the horizontal

flow of

impacted groundwater

within the

deep

alluvial

aquifer

Construction of vertical barrier

would

require

keying

into

low-permeability geologic

formation such

as

shale bedrock

or

clay

Two basic wall

configurations

were

considered

Partially

Encapsulating

Wall

typical

layout

for this

type

of

barrier consists of wall

along

the east and south

downgradient

sides of the

impoundment

The barrier

would be

completed

with an interior

hydraulic

gradient

control

system utilizing interceptor

trenches

or extraction

wells within the

impoundment

and

upgradient

of the wall

The

hydraulic

gradient

controls would

prevent hydraulic mounding by

maintaining

an

inward

gradient

1375 Alternatives

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Report-Final

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---

IDENTIFICATION OF LEACHATE

MANAGEMENTAND FINAL COVER ALTERNATIVES

Fully Encapsulating Wall This

type

of barrier consists of wall

surrounding

the entire

perimeter

of

the ash

impoundment

to

fully encapsulate

the saturated ash

zone

and deflect

upgradient

groundwater

flow around the

impoundment

Internal

hydraulic

controls

may

be

required

to

manage groundwater

fluctuations

that could

potentially

compromise

containment

integrity

Several vertical barrier wall

technologies

are

available

including

sealed sheet

piling

cement-bentonite

slurry

or soil-cement

slurry

and

jet grouting

Each of these

technologies

has the

capability

to create

barrier with

hydraulic conductivity approaching

cm/sec with

proper design

and

QA/QC during

installation

However

without

competent

low

permeability

formation in which to

key

the barrier

wall

proper

containment cannot be achieved

3.3 Final Cover

Alternatives

Four different final cover alternatives

were

selected for initial evaluation

Geosynthetic

final

cover

30

mil

PVC

Compacted clay

final

cover

Layered

earthen final

cover

and

Pozzolanic

fly

ash final

cover

The first two alternatives

are consistent with the

requirements

of 35 JAC Section

811.314 These cover

systems

consist of low

permeability

layer

either

geosynthetic

membrane

e.g

30-mil

PVC

or

feet

of

compacted

clay

followed

by

3-foot thick final

protective

layer designed

to

support

vegetation

and

protect

the low

permeability layer

The third

alternative

layered

earthen final

cover

reflects

simplified

approach

to

traditionally accepted

landfill

cover

design practices

and would

require

an

adjusted

standard

from the Illinois PCB

to

implement

as

the

cover

does

not meet the

requirements

of

Section 811.314 Earthen

cover

designs

have

been used

to

achieve closure

at

similar

fly

ash

management

facilities

in Illinois Instead of

relying

on

low

permeability clay

or

geosynthetic covers

such

as PVC

the

design

of

layered

earthen cover

incorporates

the use of

high permeability

sand and/or

gravel layers

to create

capillary

break that reduces downward

infiltration of water The

capillary

break

causes

retention

of water in the

rooting zone

which increases

transpiration

to the

atmosphere

relative to

covers

without

capillary

breaks

yet

minimizes saturation in the

rooting

zone If the

rooting

zone becomes

saturated

the

high permeability

sand

and/or

gravel layers

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

iDENTIFICATION OF LEA CHATE

MANAGEMENTAND FINAL COVER ALTERNATIVES

promote

rapid

lateral

drainage

and continue to limit infiltration

However

migration

of

water to this

drainage layer

would

only

occur

after the retention

capacity

of the

rooting

zone is reached

Given the humid climate in this

area

the earthen

cover

will

not

be

as

effective

as

compacted clay

or

PVC cover in

limiting

infiltration into the

ash however

net reduction in annual infiltration

can

be

achieved

Additionally

the earthen cover

may prove

an

acceptable

alternative

because it

provides

direct

contact barrier meets the

requirements

of final

protective

layer

and because infiltration

represents

small fraction of ash

constituents

that

leach to

groundwater

in Pond Dthe

majority

of ash constituents

present

in the

groundwater

leach from ash situated below the

water

table via

groundwater

throughflow

Construction

of an earthen

cover

is lower cost

approach

since

no

geosynthetic

materials

are used

and it

relies on

locally

available materials

The fourth and final

cover

alternative

reflects

an innovative

approach

to cover

design Fly

ash from an

on-site source

Pond

would be collected and blended with

stabilizing reagent e.g quick

lime

Portland

cement

class

fly ash

to create

cement-like monolithic cover to minimize the rate of

groundwater

infiltration and

leaching

of ash

constituents

to

groundwater

Consistent with the

requirements

of Section 811.3

14

3-foot thick low

permeability layer

would be constructed from the

pozzolanic fly

ash mixture followed

by

3-foot thick earthen

protective

layer

With

adequate

mixture

design

and

quality control

low-permeability

cover with

properties approaching

those of

geosynthetic

or

compacted

clay

cover can

be

achieved

Construction of

pozzolanic fly

ash

cover

would

require

an

adjusted

standard from the Illinois PCB to

implement

however

regulatory

precedent

exists for similar cover

technology

Part 816

provides

alternative

standards for final

cover

systems

at coal ash

management

facilities

using

similar

process

to

stabilize flue

gas

desulfurization

FGD

sludges

with

fly

ash

Poz-O-TecTM

process

It is

likely

that

construction

of

pozzolanic fly

ash final

cover

could meet

or

exceed the alternative

standards

for

strength

and

approach

the alternative

standards

for

permeability

outlined in Section

16.530

for

testing

of

the

final

cover constructed with the Poz-O-Tec

process

Construction

of

pozzolanic fly

ash

cover

would

likely

reflect the

highest

cost final cover

approach

however

the

high

cost

may

be offset

by

the creation of

additional

capacity

for

fly

ash in the lined ash

impoundment Pond

3.4 Surface Water

Management

Alternatives

Three surface

water

management

alternatives

were selected for initial evaluation

consisting

of the

following

1375 Alternatives

Analysis Report-Final

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RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEA CHA TE MANAGEMENTAND

FINAL CO VER ALTERNATIVES

Route surface

water east towards the Wabash

River

Route surface water west towards the

drainage

collection

pond Pond

and

Route surface

water east

and

west

toward the Wabash River and the

drainage

collection

pond Pond

Diverting

all surface water to the Wabash River would

require

the

most fill while

combining

surface

water

drainage

to either the Wabash River or Pond

would

require

the least fill

box culvert

has

already

been constructed

to route surface water from Pond

to Pond

For

purposes

of

estimating

fill

volumes

to construct

the surface

water

management

alternatives

minimum5%

slope

has been assumed

to

provide adequate drainage

and

prevent

standing

water from

accumulating

in

depressions

on

the final

impoundment

surface

fourth surface water

management

alternative

creation of

detention

pond

and

dewatering

sump

for

diversion

to Pond

was not considered for the

following

reasons

Section 811.322

prohibits

standing

water

anywhere

on

solid waste unitan

adjusted

standard from the Illinois PCB would be

required

to construct

detention

basin

on

the

unlined ash

impoundment

and

Use of detention

basin would

likely

negate

the

opportunity

to receive

an

adjusted

standard for use of an earthen

or

pozzolanic

final

cover

system

3.5 Initial

Screening

Criteria and Results

Initial

screening

criteria for

assessing

leachate

management

final

cover

and surface water

management

alternatives

consist of the

following

Construction

Implementation

Feasibility

Construction

feasibility

refers

to

the

ability

to

build the

system given site-specific

conditions

Implementation feasibility

refers to the

ability

of this alternative

to meet technical factors such

as

appropriateness

or

suitability

and

availability

of the

technology given

site

specific

constraints and

geographic

location

and administrative

factors such

as

local

and state

permitting

requirements

and

regulatory

reviews for

approval

Effectiveness

Effectiveness

refers to three criteria

consisting

of

the

extent to

which

the alternative

protects

human health and the

environment

reduction in contaminant

levels

to meet Section 811.320

groundwater

quality

standards

and

the extent

to

which

the alternative

has been demonstrated

at

other

sites

Cost Costs for the

purpose

of initial

screening

refer to relative cost

ranges

for each of

the

alternatives

and include utilization

of available

published

cost data from similar

projects

vendor

data

and

engineering judgment

As such costs are for

general

1375 Alternatives

Analysis Report-Final

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Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTiFICATION OF LEA CHATE

MANAGEMENTAND FINAL COVER ALTERNATIVES

comparative

purposes

and are not used

singly as

screening

tool unless substantial

cost

differentials would

immediately preclude

the

technology

from

further consideration

Of the three initial

screening

criteria identified

above the most crucial is construction

implementation

feasibility

If

technology

failed this

criterion then it was not considered for further evaluation

Therefore

the criteria of effectiveness

and cost

are

secondary

unless substantial

concerns in either of the

secondary

criteria were identified that would

clearly

eliminate the

alternative

i.e same

feasibility

and

effectiveness

with

significantly higher costs

The results and recommendations

of the initial

screening

are

listed in

the last column of Table 3-1 The

rough

cost summaries for each of the alternatives

are

provided

in

Appendix

Table 3-2

provides

summary

of the areal extent and volumes of ash in Pond

used for

quantity

estimation in

the

rough

cost

summaries Table 3-3

provides

material balance

analysis

for each of the final

cover alternatives

that

explains

how each source of fill available on site will be utilized within the final

cover alternative

The

alternatives

selected for further evaluation and

modeling

consist of the

following

Leachate

Management

Alternatives

Site

monitoring

with

no

leachate

collection

Groundwater

extraction

combined with

interceptor

drain/trench

Interceptor

drain/trench

Source Control in the

Deep

Alluvial

Muifer

via

Groundwater

Extraction

Final Cover Alternatives

Geosynthetic

final cover

Earthen final

cover

Pozzolanic

fly

ash final

cover

Surface Water

Management

Alternatives

Route surface

water east

and

west towards the Wabash River and the

drainage

collection

pond

Pond

1375 Alternatives

Analysis Report-Final

NATURAL

3-9

RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEACHATE MANAGEMENTAND

FINAL COVER ALTERNATIVES

3.6

Treatability Study

for Pozzolanic

Fly

Ash Final Cover

The results of the initial

screening

included

the

pozzolanic fly

ash final cover alternative

for further

evaluation and

modeling

If the

pozzolanic

cover can

provide

similar

performance

to traditional final

cover

designs e.g compacted clay

and/or

geosynthetic

the Hutsonville Power Station

may

have

the

opportunity

to

beneficially incorporate

fly

ash from Pond

with the added benefit of

renewing capacity

in Pond

The

treatability study

was

performed

to evaluate

the technical

feasibility

of

constructing

pozzolanic fly

ash

cover

from Pond

Specific objectives

included

The

ability

to

approach

or meet the alternative

standards

for

strength

and

permeability

as

outlined in Part

816 for

similar

regulatory

approved

final cover

technology

the Poz-O

Tec

process

The

range

of

admixtures that can be

successfully

mixed with Pond

fly

ash to

construct

pozzolanic fly

ash final

cover

and

The best mix

design

for

pozzolanic fly

ash

cover

that

provides

the best balance of

constructability

and

performance

with

respect

to the Part 816 standards

and cost

VFL

Technology

Corporation VFL

was selected to

perform

the

treatability study

The results

of

the

treatability study

are

included

as

Appendix

C-i

Conceptual

Development

of Pozzolanic

Cap

for

Closure of Basin

and the Hutsonville Power Station

Treatability

Study

Specific

details

regarding

the

study including

geotechnical

investigation

raw

materials

characterization

mix

design preparation

mix

design performance

testing

and

extrapolation

to full-scale

operations

are

included in the

Treatability Study

Reagents

that

were

evaluated

during

the

study

included Portland

Cement

Class

fly

ash fluidized bed residue ash

FBR

quicklime

fluidized

gas

desulfurization

scrubber

sludge

FGD

or

filter

cake

and native soils VFL evaluated 16 mix

designs

as

listed in

the

Treatability Study

Table

Specific

conclusions

provided

in the

study

Section 2.0

Treatability Study

indicate that construction

of

pozzolanic fly

ash final cover

system using

ash from Pond

is feasible

from

geotechnical

treatability

and

performance

based

stance

Specifically

VFL recommended five mix

designs

that

provide

the best

performance

and

applicability

for construction

under field conditions

that included

Mix

Designs

and

Pond

fly

ash and

cement

Mix

Designs

and 10

Pond

fly

ash on-site

soil

and

cement

and

Mix

Design

14

Pond

fly

ash

FGD filter

cake

and

cement

1375 Alternatives

Analysis Report-Final

NATURAL

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RESOURCE

TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF

LEACHATE MA NA GEMENTAND FINAL COVER

ALTERNATIVES

The

performance

of

each of these mix

designs

with

respect

to

performance

goals

listed above are

provided

in Table 3-4 The

following pertinent

observations were

developed

from

comparison

of each

recommended mix

design

to the

performance

goals

The

permeability

results for each mix

design

do

not meet or exceed the

performance

goal

of

cm/see

The

unconfined

compressive

strength

UCS at

84

days

for each mix

design

exceeds the

performance

goal

of 150

psi

Each mix

design

appears

to be constructable

in the

field

although

several

constructability

concerns were

noted

for Mix

Design

14

Specifically

the

rapid strength gain

and

ultimate UCS of Mix

Design

14

Figure

Treatability Study

could

present

construction

challenges

In

addition

VFL

specifically

noted

Section 4.4

Treatability Study

that

FGD

sludge

utilized in Mix

Design

14

can be

difficult to

accurately

feed into

portable

processing system

and

adequately

mix with the

fly

ash and other

reagents

as

the material

has

tendency

to adhere to the sides of the feed

hoppers

and

Three of the five recommended mix

designs Mix

Designs

and

14 were

tested for

leaching performance

Table

Treatability Study

The results of the TCLP

testing

of

RCRA metals for each mix

design

indicated that leachate

concentrations

did not exceed

the Groundwater

Quality

Standards for

Class

Potable Resource Groundwater

with the

exception

of

cadmium

detected

slightly

above the Class

standard at 0.01

mgfL

for Mix

Design

This

concentration

is well below the Groundwater

Quality

Standards for Class

II General

Resource Groundwater

for cadmium

at

0.05

rngfL

Furthermore

VFL

expressed

concern with the chemical and

physical variability

of FGD

sludge

that

could

significantly

alter the

performance

characteristics

of mix

designs

that utilize

this

reagent

Mix

Design

14

Based

on

the

results

of

the

study

and the

comparison

with the

performance

goals

the

following

considerations

have been

developed

for

possible

full-scale

implementation

of

pozzolanic fly

ash final

cover

system

for Pond

Low

permeability

conditions

can

be

achieved

that will minimize

concerns

for

continuing

impacts

to

groundwater

related

to

infiltration

of

surface water to the ash in Pond

The

range

of available

compressive

strengths

will

provide

suitable

conditions

for

construction

of

pozzolanic

final

cover

Leach

testing

indicates that the

processing

of ash from Pond

for

pozzolanic

final cover

materials for Pond

will

not result in leachate

concentrations

that exceed

Class

Groundwater

Quality Standards

range

of mix

designs

will

support

effective

construction

of

pozzolanic

final

cover

system

relative to

site-specific design requirements

and

1375 Alternatives

Analysis Report-Final

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TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

IDENTIFICATION OF LEACHATE

MANAGEMENTAND FINAL COVER ALTERNATIVES

Mix

Design

14 is

not recommended for the

pozzolanic

final

cover

system

due

to

field

constructability

concerns

and

potential

chemical and

physical variability

concerns noted

byVFL

1375 Alternatives

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Report-Final

NATuRAL

3-12

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TECHNOLOGY

Electronic Filing - Received, Clerks' Office, August 11, 2008--AS 09-1, Exhibit 3

---

MODELING AND EVALUATION OF

SELECTED

ALTERNATIVES

4.1

Purpose

The

purpose

of the

modeling

was to

predict

the effect of closure alternatives

selected for further

evaluation

in Section

The

modeling

was

performed using

the

calibrated

groundwater

flow and

transport

model

developed

for this

site

which

was documented

in

the NRT

report

Groundwater Model

Evaluation

of

Impoundment

Closure

Options

January 2000

The calibrated

model from the

January

2000

report

was utilized

as

the

starting point

for this

modeling6

which included

variation on five final

cover

options

and four

groundwater

extraction

variations as summarized in Table 4-1

The

prediction

modeling

was

performed

with the intent

to

represent

implementation

of the final cover and

leachate

management

alternative

in 2004 Due

to

subsequent findings

of low level ash

impacts

at

monitoring

well MW-14

Section

2.4

and

subsequent

installation

of off-site

monitoring

wells

Section

2.2

the assumed timeframe for

implementation

of the closure

alternatives

has

passed

The net effect

from the model

perspective

is that the time between

dewatering

of the

impoundment 2001

and estimated

implementation

of the final

cover

and leachate

management

alternative

2006

to

2007

will increase This

increase will have

no

effect

on

the

predictive

model

comparison

and

results therefore

for

purposes

of

modeling

and evaluation

of selected

alternatives

the

model

presented

in this

report

remains valid and has

not been redone

The alternatives were modeled in the

following

order

Final cover alternatives

Final cover alternatives

combined with leachate

management

alternatives

In other

words

the initial heads and concentrations used in this

model were the final calibrated heads and

concentrations for the

steady-state portion

of the model calibrated in 2000 That

steady

state

model

was

calibrated

to

represent

conditions

through

the end of

2000

and assumed that Pond

was

in

service until the end of 2000

Therefore

prediction modeling performed

here

begins

with

dewatering

beginning

in

2001

and

assumes

that the

final cover and leachate

management

alternatives

can

first be

applied

in

2004

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MODELING

AND EVALUATION OF SELECTED

ALTERNATIVES

4.2 Model

Approach

Transport

of boron

was modeled because it was the

parameter

calibrated in the 2000 model

Boron

was

modeled in 2000 because it is

an

indicator

parameter

for coal ash leachate

and it is mobile in

groundwater

Three model

codes were used to simulate

groundwater

flow and contaminant

transport

Post-closure

leachate

percolation

was modeled

using

the

Hydrologic

Evaluation

of

Landfill Performance

HELP

model

Groundwater

flow

was modeled in three dimensions

using

MODFLOW

The

HELP

model

provided

leachate

percolation

rates for

input

to

MODFLOW

and

Contaminant

transport

was

modeled in

three dimensions

using

MT3DMS

MODFLOW

calculated

the flow field that MT3DMS used in the

contaminant

transport

calculations

The

general background

and

use

of the

HELP MODFLOW

and MT3DMS codes

are described

in

detail

in the 2000 model

report

Specific

parameter changes

from the 2000

modeling

are discussed below

4.2.1 HELP

Modeling

HELP

Version 3.07 Schroeder et

al 1994

was used to estimate

percolation

from the

impoundment

for

five cover scenarios The

hydrologic

data

required by

and

entered into HELP are listed in

Appendix

Table D-1 and described in the

following paragraphs

disk

containing

model files is attached

to

the

back of the

report

CO-I

3-footEarth

CO-2 3-foot Earth

over

geosynthetic

layer

CO-3a 3-foot Earth

layer

over 3-foot

pozzolanic layer

with

lx10-7

cmlsec

CO-3b 3-foot Earth

layer

over 3-foot

pozzolanic layer

with

lx 10-6

cm/sec

and

CO-3c 3-foot Earth

layer

over 3-foot

pozzolanic layer

with

lx 10-5 cm/sec

Scenario CO-I is the native soil

cap

scenario from the 2000

modeling

The other scenarios

used in this

modeling were

developed

by

adding layers

to

represent

PVC

compacted clay

or

the

pozzolanic layer

Each cover scenario was simulated

assuming

the ash

was

uncapped

with

no runoff for three

years

2001-

2003

while the

impoundment

dewatered and the closure

alternative was enacted

Scenario-specific

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MODELING

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changes

were

simulated

beginning

the fourth

year

2004

and

through

the end of the simulation

2025

25-year

simulation

2001 through 2025

was sufficient for the

system

to reach

equilibrium

after

enactment of the closure scenario

4.2.2

MODFLOW/MT3DMS

Percolation rates obtained from HELP

were

utilized

as

recharge

rates for the Pond

ash cells in

MODFLOW Concentration values for the ash cells

were

the

same as

in

the 2000

model

except

for the

period

after the

cap

was installed

2004-2025

when concentration

for the

ponded portion

of Pond

was

increased

from

to 20

mgIL

This

change

is based

on

NRTs

experience

at other

impoundments

and

assumes

that

leachate

concentrations

will increase after the

pond

is removed The

reasons

for this

expected

increase are associated

with removal of the

pond

water

which has

typically

has lower

concentration than

the

porewater

in the

ash

and with removal of the

hydraulic

head

imparted

on

the

impoundment by

the

pond

water when slows

percolation

rates

through

the coal ash and increases contact

time

The 2000 model included

recharge

terms to simulate the former ash

laydown

area However this feature

was removed when Ponds

and

were constructed in 2001 This model

represented

removal

of the ash

laydown

area and

replacement

with Ponds

and

by changing recharge

rates

and

concentrations

in this

area to

the values used for Pond

the

lined ash

impoundment

4.2.3 Criteria for Evaluation of

Modeling

Results

Two

general

criteria were identified for evaluation

of

modeling

results

as measure

of the

scenarios

effectiveness

Effectiveness

Criteria

No

Compliance

with the health-based

Class Groundwater

Quality

Standard for boron

mgIL

at the

monitoring

wells

surrounding

Pond

and

Effectiveness

Criteria No

The time

frame

in

years

in

which the

modeling

scenario

achieves the Class Standard

for boron at the

monitoring

wells

4.2.4

Simulation

of Final Cover and Leachate

Management

Alternatives

The final

cover

alternatives

described in Section 4.2.1 were first modeled

individually

Then

two

representative

cover

scenarios

were

modeled with the

leachate

collection

alternatives

The leachate

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Alternatives

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MODELING

AND

EVALUATION OF SELECTED

ALTERNATIVES

collection

alternatives

were

simulated in

combination with final cover

alternatives

rather than

individually

because the no cover alternative

is not

being

considered

for this

facility

For

purposes

of the

modeling

evaluation

the leachate

collection

alternatives

were

assigned

the

following

designations

referred to as leachate

extraction

options

LEO

LEO-I Shallow

groundwater

extraction

wells

east

combined with an

interceptor

drain/trench

south

LEO-2

Interceptor

drain/trench

east

and

south

LEO-3

Interceptor

drain/trench

south

only

and

LEO-4

Interceptor

drain/trench

east

and

south

700 feet shorter than in LEO-2

along

the east

alignment

In

addition two

drain/trench

depths

were modeled as

designated by

or

for shallow and

deep

respectively

The difference

between the shallow and

deep

trench

designs

is

an

approximate

foot

increase in trench

depth

The trench

depth

was

varied

to

evaluate

the

design depth

necessary

to

effectively

collect

groundwater

affected

by

ash

leachate LEO-4

was

simulated

because tiebacks

associated

with

retaining

wall on the Wabash River would interfere with trench installation

along

the

northern

portion

of Pond

Groundwater