United States National Risk Management

Environmental Protection Research Laboratory

Agency Cincinnati, OH 45268

Research and Development EPA/600/SR-97/081 October 1997

Life Cycle Design of Amorphous

Silicon Photovoltaic Modules

Geoffrey M. Lewis and Gregory A. Keoleian

Project Summary

The life cycle design framework was

applied to photovoltaic (PV) module design. The primary objective of this

project was to develop and evaluate

design metrics for assessing and guiding the improvement of PV product systems. Two metrics were used to assess

life cycle energy performance of a PV

module: energy payback time and electricity production efficiency. These

metrics are based on material production, manufacturing, and transportation

energies, and were evaluated for several geographic locations. An aluminum frame is responsible for a

significant fraction of the total energy

invested in the module studied. Design

options to reduce the energy impact of

this and other components are discussed.

This Project Summary was developed

by EPA’s National Risk Management

Research Laboratory, Cincinnati, OH,

to announce key findings of the research

project that is fully documented in a

separate report of the same title (see

Project Report ordering information at

back).

Introduction

Interest in sustainable energy technologies that are both practical and affordable

has increased with growing awareness of

the environmental and political consequences of fossil fuel and nuclear electricity generation. PV modules, one variety of

which is the subject of this report, offer a

promising alternative to our current dependence on nonrenewable energy technologies. Photovoltaic modules convert

some of the energy contained in sunlight

directly into electricity without producing

waste or emissions.

This life cycle design project was a collaborative effort between the University of

Michigan and United Solar Systems Corporation (United Solar). United Solar is a

joint venture between Energy Conversion

Devices (ECD) of Troy, Michigan, and

Canon, Inc. of Japan. ECD is a leader in

the research and development of thin film

amorphous silicon photovoltaic modules.

Canon is known worldwide as a manufacturer of electronic, office, and photographic

equipment.

The United Solar UPM-880 tandem junction commercial power generation module

was the product chosen for this demonstration project. The UPM-880 is currently

United Solar’s standard power generation

module and is the most directly comparable with other manufacturers’ products.

It employs thin film amorphous silicon as

the photovoltaic material and contains two

identical semiconductor junctions (hence,

tandem). This module has a rated output

power of 22 watts, is 119.4 x 34.3 x 3.8

centimeters in size, weighs 3.6 kilograms,

and has a stabilized conversion efficiency

of 5%.

The UPM-880 represents a point in the

development of thin film PV technology

which has since been surpassed. The opportunity to influence this technology improvement made the UPM-880 product

system a good candidate for study. United

Solar is exploring innovative applications

of thin film PV technology including incorporation of PV into building materials such

as standing seam metal roofing systems

and roofing shingles that have the ap-
2

pearance of common asphalt shingles.

Roofs, glazings, and facades all become

producers of electricity in addition to performing their traditional structural or architectural functions when thin film PV

materials are used to coat building surfaces. These building-integrated PV applications are made possible in part by thin

film characteristics such as ruggedness,

flexibility, and low cost.

Life cycle design was developed to more

effectively integrate environmental considerations into product system design. The

product system encompasses material production, parts fabrication and assembly,

use, and retirement. Systems analysis

based on the product life cycle offers a

comprehensive approach for guiding improvement of photovoltaics and other products.

Objectives

The primary objective of this demonstration project was to develop and apply

design metrics for assessing the energy

performance of photovoltaic technologies.

This study was a partial application of the

life cycle design methodology which also

includes the assessment of waste and

emissions throughout the product life cycle.

The scope of this study was limited by the

availability of life cycle inventory data. The

two metrics discussed here are energy

payback time and electricity production

efficiency.

The length of time required for a module to generate energy equal to the amount

required to produce it from raw materials

is called the energy payback time. Energy

payback time is frequently used as a performance benchmark for renewable energy technologies, particularly PV. Fossil

fuel and nuclear electricity generating

plants are not evaluated by energy payback time because they effectively never

pay back. Generating losses and the ongoing need for input energy (as fuel) conspire to ensure that fossil fuel plants cannot

generate as much energy as they consume on a primary energy basis.

Electricity production efficiency is defined as the ratio of the total energy produced by a generating system over its

lifetime to the sum of energy inputs required for the system’s manufacture, operation and maintenance (including fuel),

and end-of-life management. This ratio can

be used to compare all types of renewable or fossil fuel based generating technologies.

Product Description

Over 26 different materials are used in

the production of the UPM-880, 20 of which

are actually incorporated into the finished

product. Module production begins with a

stainless steel substrate which is processed in the following steps: washing,

back reflector deposition, amorphous silicon alloy deposition, transparent conductive oxide (TCO) deposition and scribing,

short passivation, grid pattern printing, and

cell cutting. All steps through TCO deposition are continuous processes.

The processed substrate is laminated

inside encapsulation materials which provide environmental protection while allowing the maximum amount of light

transmission to the active photovoltaic

material. A sandwich of materials is assembled in the following order (from front

to back): Tefzel (a Teflon based polymer),

EVA, the processed substrate, an EVA/

polymer composite layer, and finally a galvanized steel backing plate (Figure 1).

The steel backing plate is laminated to

the material in the rest of the module by

EVA, making its separation during disassembly nearly impossible. The steel backing plate and aluminum frame serve as

structural components only, providing rigidity and mounting points for the module.

Methodology

Scope and Boundaries

Clearly defined boundaries that constrain

data gathering and analysis are critically

important in comparative product system

studies. Results depend directly on boundary definition, which also determines

whether the results may be compared with

those of other studies. This study included

data for raw material extraction and processing (for both product and process

materials), transporting processed materials to manufacturing facilities, manufacturing, transporting modules to the use

site, and module use. All data were determined on a per module basis. Not included were data on installation or

balance-of-system (BOS) components.

BOS components include mounting and

support structures, tracking hardware (unless the array is fixed), wiring and terminals for interconnection of modules in the

array, power inverters to convert the DC

output of the PV module into utility-grade

AC and to interface with the utility electricity grid, energy storage (if the array is not

grid-connected), and labor for installation,

operation and maintenance. Energy used

for the manufacturing facility physical plant

(lighting and space conditioning) and energy involved in packaging and packaging

materials were also not included.

Data on the end-of-life phase were not

collected since there is no infrastructure

to deal specifically with PV modules. Energy required for or credited from reuse or

recycling options was not considered in

this study, except as discussed in the

Design Implications section below.

Data Collection and Analysis

All energy data were considered on a

per module basis and were converted to

equivalent primary energy (EPE) to account for losses in conversion and generation. EPE makes all energy data

functionally equivalent, allowing direct comparison. For example, electric energy from

the grid cannot accurately be compared

to natural gas energy without taking into

account production efficiencies for both

electricity generation and natural gas production. Ignoring the fuel required to produce electricity significantly distorts

analysis. To avoid this, the United States

average electricity generating efficiency

ratio of 0.32 was used to convert electricity to EPE for this study.

Materials

Published data for extracting and processing raw materials (material production energy) were not available for all

materials used to produce the UPM-880.

Estimates were made for some materials

based on discussions with industry

sources. For materials manufactured by a

small number of firms, energy data are

usually considered proprietary. In these

cases, we substituted data for similar materials or processes.

United Solar provided a bill of materials

for the UPM-880 with all data items on a

per module basis. United Solar provided

data on supplier location and utilization

Figure 1. Laminated module, edge cross section.

Tefzel

EVA

Processed substrate

EVA / polymer composite

Steel backing plate
3

efficiency for each material as well, allowing a calculation of the actual amount of

material incorporated into a module and

the amount of waste material per module.

The amount of energy expended to

transport materials to United Solar facilities was calculated using distances determined from the location data, information

on transportation energy requirements in

units of energy per weight-distance (Btu

per ton-mile), and material weight data

from the bill of materials. It was assumed

that a diesel tractor trailer was used for all

overland transportation and an ocean

freighter was used for all overseas transportation.

Manufacturing

There are three components of manufacturing energy: processing energy, energy in process materials, and energy for

transportation to the use site. Manufacturing process energy data were provided,

on a per module basis, by United Solar.

Process materials were handled by the

same method discussed above for product materials. In most cases, however,

data on material production energy for

process materials were not readily available from the literature. The amounts of

process materials used per module were

low relative to most product material inputs, so process materials were assumed

to contribute a negligible amount to total

module energy requirements.

Use

Use phase data for the energy payback

time calculation consist only of insolation

at the module location and the module’s

conversion efficiency (module size is a

constant, equal to 0.372m2). Insolation

data, as direct normal solar radiation in

watt-hours per square meter per day, were

taken from the National Renewable Energy Laboratory’s (NREL) online computer

database and converted to units of kilowatt-hours per square meter per year. Data

were taken for three cities of interest: Detroit, Michigan, near United Solar and the

University of Michigan; Boulder, Colorado,

near NREL; and Phoenix, Arizona, a location generally considered to be an excellent site for PV use. These three cities

approximately span the range of insolation available in the continental United

States, from a low of around 1200 kWh/

m2/yr in Detroit to around 2000 kWh/m2/yr

in Boulder to a high of around 2500 kWh/

m2/yr in Phoenix.

Life Cycle Metrics

Material production energy includes energy for raw material extraction, processing, and transportation. These data were

gathered in megajoules per kilogram. Because material production energy data vary

over a wide range, low and high values

were used in separate calculations, resulting in two values for each energy metric. The energy used to transport one

module worth of materials to manufacturing facilities was then calculated and added

to the material energy.

Energy data for each module manufacturing process step were gathered on a

per module basis. This energy was all in

the form of electricity and was converted

to equivalent primary energy as discussed

above. Transport to the use site was assumed to be by diesel tractor trailer.

Calculating energy generated by a module in use requires data for its stabilized

conversion efficiency and area, along with

average insolation where it will be installed.

Once the energy generated by a module

was known, all data necessary to calculate energy payback time and electricity

production efficiency metrics were available.

Two other metrics, life cycle conversion

efficiency and life cycle cost, are discussed

in the full report from this project.

Energy Payback Time

Payback time in years was calculated

by dividing the total amount of energy

used to manufacture a module from raw

materials, install and operate it over its

lifetime, and deal with end of life disposition by the amount of energy a module

generates in a year using Equation 1. The

variables in this equation are defined as

follows: Emat = energy to extract, process,

and transport raw materials to the manufacturing facility; Efab = energy to fabricate

a module from raw materials and transport it to the use site; Einst = energy required for module installation (assumed to

be 0); Eelm = energy required for any endof-life management activity (assumed to

be 0); Egen/yr = energy generated by a

module in one year; and Eo&m/yr = energy

used annually for operation and maintenance (assumed to be 0).

Payback time

=

E EEE

E /yr E /yr

mat fab inst elm

gen o&m

+++

− (1)

Electricity Production Efficiency

Electricity production efficiency is calculated by summing the energy produced by a generating system over its

lifetime (Egen (lifetime)), and dividing it

by the sum of the energy inputs required to manufacture (Emat + Efab), install, operate and maintain (Eiom, which =

Einst + (module lifetime) (Eo&m/yr)), and dispose of or reclaim it at the end of its

lifetime (Eelm), using Equation 2. Eiom and

Eelm were assumed to be zero for this

analysis; in actuality both are likely to be

small numbers.

Electricity production efficiency

= E (lifetime)

E EEE

gen

mat +++ fab iom elm

(2)

Electricity production efficiency was calculated for the same geographic locations

as payback time. Two possible module

lifetimes, 10 and 25 years, were chosen

to demonstrate how this variable effects

the metric (the UPM-880 is currently

warrantied for 10 years).

Electricity production efficiency is presented as a ratio. A system that generates more energy than is required to

produce it would have an electricity production efficiency greater than unity and

could be considered to be a sustainable

system.

Results and Discussion

Life Cycle Data

Energy data for production and transport of product materials are shown on a

per module basis in Table 1, sorted from

highest energy at the top to lowest at the

bottom. When more than one material is

required for a function, it is noted as “various” in the material column. Notice also

that there are two totals at the bottom of

the table, one for a standard module and

one for a frameless module. This classification highlights the impact of the aluminum frame on the energy requirements

for the UPM-880.

Energy required for manufacturing, converted to equivalent primary energy (EPE),

is shown in Table 2. These data were

gathered at United Solar by measuring

electrical consumption of the respective

machines for the amount of time necessary to process one module. The bulk of

this energy is invested in processes that

require elevated temperatures for a long

period of time (encapsulation) or at greatly

reduced pressure (all of the deposition

steps).

Life Cycle Metrics

Energy Payback Time

Energy payback time results are presented in Table 3. Module production energy summarizes the material, transport,

and manufacturing energy discussed in

Tables 1 and 2 for both the standard and

frameless cases. Table 3 presents energy

payback times in years for various locations and module conversion efficiencies.

Energy generated per year is calculated

as the product of insolation, conversion
4

efficiency, and module size. Energy payback time in years is calculated as module production energy (in kWh) divided by

energy generated per year. The conversion efficiency of the UPM-880 is currently around 5%, but energy payback

times were also calculated for a conversion efficiency of 8% to illustrate the effect

of efficiency improvements on payback

time. United Solar has produced a prototype module with a 10% conversion efficiency and is currently translating this

technology into production.

Our methodology results in payback

times higher than previously reported.

Srinivas reports payback times for 5% efficient amorphous silicon modules produced in batch production facilities outside

North America. His results ranged from

2.18 years for a frameless module to 2.6

years for a module framed with plastic

and glass using an insolation level roughly

equivalent to our Detroit case. Hagedorn

estimates a payback time of 3.5 years for

a 5% efficient module framed with plastic

and glass produced in a proposed facility.

Construction and material factors in both

of these studies seem to indicate modules

with shorter lifetimes than the UPM-880.

Payback times calculated in this study

should be compared with others published

in the literature only if differences in the

assumptions, data, and methodologies are

carefully considered.

Electricity Production Efficiency

Electricity production efficiency results

are presented in Table 4. Module production energy is identical to that noted in

Table 3 and the same three locations are

used, although the number under the location now represents the amount of electricity generated per year by a module at

5% conversion efficiency. Energy generated over a module’s lifetime is the product of electricity generated per year and

module lifetime. Electricity production efficiencies were calculated with Equation 2.

Note that the high electricity production

efficiency value for each case results from

the low module production energy value,

and vice versa, and also that values less

than unity result from module production

energy being greater than energy generated. For comparative purposes, the United

States electricity grid has an average electricity production efficiency of 0.32.

Design Implications

Two components of the UPM-880 photovoltaic module offer major opportunities

for improved design: the aluminum frame

and EVA encapsulant.

Energy invested in the aluminum frame

consists of material production energy and

energy required to extrude and anodize

the frame parts. Material production energy can be reduced by using a higher

proportion of secondary (scrap) aluminum

to primary material, or by using a different, less energy intensive material. A

higher proportion of secondary material

might cause a decrease in the frame’s

surface quality, but as long as its structural properties and lifetime remain unaffected, cosmetic imperfections should be

tolerable. Use of the module in applications not requiring a frame obviates the

material selection process for this component and also eliminates significant energy investments.

Reusing the aluminum frame is another

method of reducing energy investment. In

the current design, the frame is easily

separable and can be used on another

module with minimal processing besides

transportation to the production facility. The

impact of reusing the frame on energy

metrics is dramatic, because the frame

represents between 34 and 53 percent of

the total module production energy (between 55 and 68 percent of total material

production energy). Reusing the frame

once halves its energy contribution and

reusing it twice drops the energy cost to

Table 1. Product Constituent Material Production Energy, in MJ

% Module

Function Material Low Case High Case Transport Mass

Frame aluminum 196.0 566.1 7.8 38.0

Encapsulation various 84.0 114.8 7.7 25.2

Substrate stainless steel 58.7 73.0 3.9 11.4

Backing plate steel 9.7 65.4 6.1 24.8

Deposition materials various 7.7 7.7 0.1 *

Busbar various 0.8 3.6 0.1 *

Back reflector various 0.2 0.7 * *

Grid various * * * *

TCO various * * * *

Standard, total material energy 357.1 831.4 25.5

Frameless, total material energy 161.1 265.4 17.7

* Negligible amount, <0.05.

Standard - low energy case uses lowest reported data and assumes 70% primary / 30% secondary frame material;

high uses the highest available data and assumes frame is 100% primary aluminum .

Frameless - low and high cases reflect the range of values reported in the literature.

Source: Appendix B in [7].

Table 2. Manufacturing Equivalent Primary Energy (EPE)

Process Step EPE (MJ) % of Total

Encapsulation 56.2 28.0

Amorphous SI alloy deposition 37.9 18.8

TCO deposition 32.7 16.3

Back reflector deposition 30.3 15.0

Substrate wash 23.1 11.4

TCO etch 7.0 3.5

Short passivation 7.0 3.5

Grid pattern screen print 7.0 3.5

Testing and packaging * *

Total process energy 201.2 100.0

* Negligible amount.
5

one third of the single-use value. Table 5

contains energy metrics calculated for various levels of frame reuse. These results

assume a module with 5% conversion efficiency and include energy to transport

the module back to the manufacturing facility for each frame reuse. Transportation

energy was assumed to be the same for

each use of the frame; distance from the

module disassembly facility to United Solar was the same as the distance from the

frame manufacturer to United Solar.

The useful life of a photovoltaic module

is a primary design parameter, as indicated in Table 4. EVA encapsulant frequently determines a module’s useful life

as it either degrades in optical quality or

moisture permeability. Formulations of EVA

have evolved to the point where browning

is no longer the concern it once was, but

moisture permeability remains a main determinant of module lifetime. In addition,

the current formulation of EVA requires

relatively high energy for lamination. A

formulation with a quicker cure time and/

or a lower cure temperature would reduce

this process energy requirement.

The one other likely candidate for component reuse is the steel backing plate. In

the current design, the backing plate is

bonded to the module in the laminating

press by a layer of EVA. If this layer of

EVA could be deleted from the module, it

would greatly facilitate disassembly and

reuse or recycling of the backing plate

while reducing material energy requirements. However, our calculations revealed

that eliminating one layer of EVA and reusing the steel backing plate had only an

incremental effect on values of the metrics,

especially compared to the effect of reusing the frame. Even so, deleting a layer of

EVA does facilitate manufacturing and end

of life management and can reduce cost.

Conclusions

The application of the life cycle design

framework offered many useful insights

for enhancing the energy performance of

photovoltaic technology. Life cycle energy

analysis highlighted the energy contribution of individual life cycle stages, process

steps, parts and components, and specific materials. The project team developed metrics to guide improvement of

photovoltaic devices and to assess how

sustainably these devices generate electricity. One of these metrics, electricity production efficiency, was discussed.

The metrics presented in Tables 3 and

4 demonstrate the relative significance of

geographic locations with higher insolation and the aluminum frame. The best

results are obtained with frameless applications in areas of high insolation, but

Table 3. Energy Payback Time Calculations

Payback Times

Frame- FrameLocation and Conver. Energy Gen/ Standard Standard less less

Insolation Eff., % Year (kWh) low high low high

Detroit, MI 5 22.3 7.5 13.4 5.0 6.3

1202 kWh/m2/yr 8 35.7 4.7 8.4 3.1 3.9

Boulder, CO 5 36.7 4.5 8.1 3.0 3.7

1974 kWh/m2/yr 8 58.7 2.8 5.1 1.8 2.3

Phoenix, AZ 5 46.1 3.5 6.4 2.3 2.9

2480 kWh/m2/yr 8 73.7 2.2 4.0 1.4 1.8

Standard: module production energy is: material production + manufacture + transport = 162.2 kWh (583.8 MJ) low

case; = 293.9 kWh (1058.1 MJ) high case.

Frameless: module production calculated as above = 105.6 kWh (380.0 MJ) low case; = 134.5 kWh (484.3 MJ) high

case.

Table 4. Electricity Production Efficiency Calculations*

Electricity Production Efficiencies

Location and Module Standard Standard Frameless Frameless

Generation Life (yr) low high low high

Detroit, MI 10 0.75 1.33 1.60 2.01

22.3 kWh/yr 25 1.87 3.33 3.99 5.03

Boulder, CO 10 1.24 2.23 2.68 3.39

36.7 kWh/yr 25 3.09 5.57 6.69 8.49

Phoenix, AZ 10 1.56 2.83 3.40 4.33

46.1 kWh/yr 25 3.91 7.07 8.51 10.83

*Assumes 5% module conversion efficiency, includes module transport energy: Detroit, 19.31 MJ; Boulder, 8.97 MJ;

Phoenix, 3.01 MJ.

Standard: module production energy is: material production + manufacture + transport = 162.2 kWh (583.8 MJ) low

case; = 293.9 kWh (1058.1 MJ) high case.

Frameless: module production calculated as above = 105.6 kWh (380.0 MJ) low case; = 134.5 kWh.

Table 5. Energy Metrics for Frame Reuse

Number of Uses

Location and Metric 1 2 3

Detroit, MI

low energy payback time (yr) 7.5 6.8 6.8

high energy payback time (yr) 13.4 10.4 9.7

low electricity production efficiency 0.8 1.0 1.0

high electricity production efficiency 1.3 1.5 1.5

Boulder, CO

low energy payback time (yr) 4.5 3.9 3.8

high energy payback time (yr) 8.1 6.1 5.5

low electricity production efficiency 1.2 1.7 1.8

high electricity production efficiency 2.2 2.6 2.7

Phoenix, AZ

low energy payback time (yr) 3.5 3.0 2.8

high energy payback time (yr) 6.4 4.7 4.2

low electricity production efficiency 1.6 2.1 2.4

high electricity production efficiency 2.8 3.4 3.5

Assumes 5% module conversion efficiency; 10 year lifetime; includes transportation energy.
6

either increased insolation or reduced module production energy are beneficial individually. For example, comparisons of

standard and frameless modules indicate

that the frame approximately doubles energy payback time and reduces electricity

production efficiency by about half. The

beneficial effect of increased module lifetime is also clearly demonstrated in Table

4.

Electricity production efficiency is a powerful metric for comparing photovoltaic

technology with other systems for generating electricity because it puts all systems on an equivalent basis. To meet a

definition of sustainability, an electricity

production efficiency greater than unity is

necessary: this enables the device to produce sufficient energy over its lifetime to

at least reproduce itself (the current United

States electricity grid efficiency is 0.32).

All but one of the cases presented in

Table 4 show efficiencies greater than

unity; most are substantially higher.

The energy investment in a conventional power plant is generally neglected

in life cycle energy analysis because it is

assumed to be small relative to fuel energy inputs. This study shows that energy

investment in the “power plant” for photovoltaic devices is substantial relative to

their energy generating capacity and cannot be neglected. A comprehensive and

fair comparison of PV and conventional

generating systems would involve enumerating all terms in (2) (including any

storage necessary for the PV system) and

other environmental impacts such as air

emissions and waste for both systems.

A simple but important conclusion from

Table 5 is that increasing the number of

module components that can be reused

and the number of times they are reused

significantly improves energy metrics. Reusing the aluminum frame will yield by far

the greatest improvement in energy

metrics; reusing other components affects

the metrics only incrementally and may

not be worth additional effort from an energy standpoint.

Energy payback time should be a critical factor in deciding whether or where to

deploy photovoltaic modules, although cost

is usually the sole criterion for these decisions. Accurate comparison between our

values of this metric and other studies

requires careful consideration of differences in methodology or data. This study

is based on actual data from an operating

production facility; many other studies use

theoretical calculations which tend to improve metrics.

Photovoltaic technology development

focuses primarily on increasing conversion efficiency and reducing cost. However, energy payback time and electricity

production efficiency add valuable perspectives for guiding photovoltaic technology

development. Energy payback time can

be used for strategic planning and decision making when all assumptions are

considered. Electricity production efficiency

is a more comprehensive metric because

it assesses the performance of a generating system over its entire lifetime. This

metric should also be used by designers

for product material selection and process

design. In addition, PV manufacturers, utility companies, policymakers, and the public should use this metric to make accurate

comparisons between generating technologies.

The properties of amorphous silicon thin

film technology seems to make it a natural fit in building-integrated PV applications such as glazing and sheathing

materials and standing seam metal roofing.

The full report was submitted in partial

fulfillment of Cooperative Agreement number CR-822998-01-0 by the National Pollution Prevention Center at the University

of Michigan under the sponsorship of the

United States Environmental Protection

Agency.
7

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

Official Business

Penalty for Private Use

$300

EPA/600/SR-97/081

Geoffrey M. Lewis and Gregory A. Keoleian are with the University of Michigan,

Ann Arbor, MI 48109-1115.

Kenneth R. Stone is the EPA Project Officer (see below).

The complete report, entitled “Life Cycle Design of Amorphous Silicon Photovoltaic Modules,” (Order No. PB97-193106; Cost: $21.50, subject to change) will

be available only from

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at

National Risk Management Research Laboratory

U.S. Environmental Protection Agency

Cincinnati, OH 45268