CASE STUDY :
Comparing Apples and Supercomputers: Evaluating Environmental
Risk in Silicon Valley
LENNY SIEGEL
Pacific Studies Center, Mountain View, California
Silicon Valley, California, is recognized globally as the
number one address in high technology. It is not only the world's
most significant concentration of high-tech industry and talent,
but the term "Silicon Valley" itself has become synonymous with a
new way of doing business, based upon constant innovation and
industrial flexibility. President Clinton and Vice-President Gore,
among others, have embraced the Silicon Valley experience as the
model for U.S. industrial growth in the new millennium.
Unfortunately, the Silicon Valley success story has been
blemished by serious environmental degradation. It contains the
greatest concentration of "Superfund" National Priorities List
sites in the country. Industrial e ffluent from high-tech firms has
contaminated the San Francisco Bay. Air pollution, principally from
motor vehicles, masks the view of the mountain ranges that frame
the Santa Clara Valley--the historic name of the region.
Silicon Valley is an excellent place to pioneer and test new
mechanisms for community-based risk evaluation because its diverse
population is aware and concerned about environmental
contamination. The highly educated engineers, scientists, and
health professionals that make Silicon Valley unique are in a
position to choose where they live. Attracted to a climate that
encourages year-round outdoor living, they feel threatened by
anything, including industrial pollution, that threatens their
qualify of life. The largely immigrant production and service
workforce, including many who have labored on California's farms,
are sensitive to environmental threats for another reason. They
have no choice but to labor in workplaces where they are daily
exposed to harmful chemicals.
For statistical purposes, Silicon Valley is often defined as
Santa Clara County, but in reality it corresponds to the northern
urban section of the County, located at the southern end of the San
Francisco Bay, as well as adjacent sections of San Mateo, Alameda,
and Santa Cruz Counties. The County's 1994 population totaled
nearly 1.6 million people. County residents live in 15 cities, as
well as unincorporated areas such as Stanford University. San Jose,
with 836,000 residents, is today the largest city in the entire Bay
Area.
Local jurisdiction over environmental issues is diffuse.
Cities, private water companies, and a Valley-wide water district
re all responsible for supplying water. Three of the County's four
sewage treatment plants serve multicity districts. Land use
planning lies principally with the cities but the County operates
bus and light rail systems.
Furthermore, Silicon Valley is inseparable from the wider Bay
Area. Air pollution and water quality are regulated by regional
agencies. A regional board has principal responsibility for
transportation planning. Daily, some 151,000 people commute into
the County. Nearly 77,000 residents commute out.
The population of Silicon Valley is, on the average, unusually
well educated and wealthy. More than 12 percent of the white adults
have graduate degrees and over 21 percent more have bachelor's
degrees; among Asians the rates are even higher: 16 and 24 percent,
respectively. The median household income in Santa Clara
County is higher than any other California metropolitan area. In
fact, according to 1990 Census data, it ranked seventh in the
nation, with an average annual family income approaching
$54,000.
Table 1. High-Tech Industry in Silicon Valley--Mean Annual
Earned Income by Gender and National Origin, 1989
(These data come from my own analysis of Public Use Microdata
Sample files from the 1990 U.S. Census. I averaged the annual
earned income of individual workers, not family or household
income. Differences therefore could be due to three factors: 1)
different pay rates (wage or salary), 2) varying lengths of
workweek (hours), and 3) duration of employment during the year.
The analysis does not determine whether pay differentials are due
to varying educational back-grounds, differing skill levels,
discriminatory employment practices, or other factors. The Census
does not ask whether workers chose part-time work or voluntarily
worked only a portion of the year, so one cannot determine whether
any group's low income was by choice.)
The averages conceal a sharply polarized society, however. In
1989, 31 percent of the Valley workforce, nearly 362,000 people,
had annual earned incomes under $15,000. With average rents nearly
$800 a month in 1990, a household earning $30,000 annually before
taxes--that is, two of the $15,000 income earners--would have to
devote a third of its gross income just for shelter. In practice,
the working poor pool their incomes so they can stay in the Valley.
The Latino, Southeast Asian, African-American, and other working
poor may work on the same products or even in the same buildings as
the male white and North Asian professionals who embody the
Valley's success, but they lack the income, power, and opportunity
that have drawn engineers, scientists, and managers to the Valley
from around the country and the world. For example, only 19.4
percent of the white men in the Valley earned less than $15,000 in
1989, while 55.6 percent of the Mexican women and 45.3 percent of
Filipina women, for example, reported earnings at that level.
A SENSITIVE ENVIRONMENT
Silicon Valley's sensitivity to industrial contamination is
perhaps an accident of history. It moved from agriculture directly
to high-tech, as sprawling apricot orchards were uprooted to make
way for tilt-up electronics industry offices, laboratories, and
factories. It is one of the nation's leading manufacturing areas,
but it never had many traditional, heavy "smokestack"
industries.
Prior to the 1980s, only a handful of activists warned of the
toxic threat of high tech, and we were ignored. Based upon reports
from high-tech factory workers, we formed what is now the Santa
Clara Center on Occupational Safety and Health (SCCOSH) in 1977.
However, most political leaders, high- tech executives, the press,
and the public at large all believed that high-tech was a clean
industry, and they considered worker health and safety efforts to
be an opportunistic attempt to unionize the nonunion electronics
labor force.
Then, in January 1982, officials disclosed that six weeks
earlier they had closed down a drinking water well near Fairchild
Semiconductor's south San Jose plant. Nearby residents had been
drinking water contaminated with toxic solvents, including
trichloroethane and dichloroethene, from a Fairchild underground
storage tank.
Upon hearing the news, neighbors concluded that the company
was to blame for what they believed to be an alarmingly high
incidence of birth defects and miscarriages. Eventually, in 1984,
the State Department of Health Services released an epidemiological
study confirming that the neighborhood did indeed suffer a cluster
of birth defects and miscarriages and that a somewhat larger area
surrounding the plant experienced a cluster of congenital heart
defects (1). In 1986, the company agreed, in an out-of-court
settlement, to pay an undisclosed "multimillion-dollar" sum to more
than 500 claimants from the neighborhood. Fairchild and its owner
at the time, Schlumberger, have spent more than $30 million on
cleanup at that facility alone.
More importantly, the Bay Area Regional Water Quality Control
Board ordered that manufacturers throughout the Valley check for
leaks, and most found them. There are literally hundreds of
contamination sites in Silicon Valley, 29 of which are considered
significant enough to be on the Superfund list. Public concern
mounted. Most public water supplies in the area do not contain
industrial pollution--many, however, have toxic byproducts of water
purification--but large numbers of people started buying bottled
water or filtering their own. Newspapers and television news
programs have discovered that toxic releases in the Valley are
nearly as sensational as kidnaping and murders.
When the Fairchild story hit the front page, community, labor,
and environmental activists created the Silicon Valley Toxics
Coalition (SVTC), which today has nearly fifteen thousand members.
Originally formed as a spin- off of SCCOSH, the Toxics Coalition
has from the start had strong participation from organized labor,
as well as traditional conservationists in the Valley. As a result,
the Coalition has consistently sought to simultaneously promote the
Valley's economic and environmental health. The Toxics Coalition
not only pressed for cleanup of contaminated areas, it spearheaded
a series of Valley initiatives, which continue today, to prevent
future contamination.
Whereas leaders of the electronics industry have at times
resisted particular regulatory proposals, they have accepted
restrictions, not only because they were "caught in the act" of
pollution but because their ability to recruit professionals from
a global labor market depends upon the perceived quality of life in
Silicon Valley. While the petroleum industry fought against local
laws to control underground storage, the electronics industry
lobbied to make them easier to comply with. Stung by
environmentalist reports based on the Toxics Release Inventory of
the U.S. Environmental Protection Agency (EPA), the Santa Clara
County Manufacturing Group, the organization of the Valley's
largest manufacturers, now issues its own annual report, touting
its members' success in reducing emissions and discharges.
In 1983, a task force led by fire chiefs from the County's
cities developed a model ordinance for the storage and handling of
liquid and solid hazardous materials. Adopted by all of the
County's industrial communities, the ordinance pioneered the
requirement for double-containment for underground tanks and
piping.
On Earth Day 1989, demonstrators demanded that IBM's San Jose
plant, the nation's number one emitter of ozone-depleting Freon
113, cut its releases. IBM reports that it was already developing
alternatives before the demonstration, but I'm convinced that
public pressure helped make commercial electronics/computers one of
the first industries to phase out ozone- depleting solvents.
In 1990, Santa Clara County governments developed a model
ordinance for controlling lethal and other toxic gases, substances
essential to semiconductor and other electronics production.
In 1992, the Air Quality district ordered United Technologies
Corporation (UTC), a rocket producer with a test facility in the
hills above San Jose, to phase out the open burning of waste solid
rocket fuel. The principal products of rocket fuel combustion are
aluminum oxide and hydrogen chloride, but long after the district
had outlawed the open burning of waste agricultural products, UTC
had been permitted to openly burn its toxic mixture.
In 1992, SVTC and its allies from other high-tech regions
successfully urged Congress to order Sematech, the Semiconductor
Manufacturing Technology Consortium, to spend one tenth of its
Federal funding on pollution prevention research.
Also in 1993, local sewage treatment plants agreed to
environmentalist demands for technical assistance and financing for
small electronics shops--in printed circuit board fabrication and
other electroplating businesses--to cut discharges of heavy metals
into the San Francisco Bay.
In 1990, SVTC joined the newly formed Technical Review
Committee at the Moffett Naval Air Station Superfund site, and in
1993 it received a Technical Assistance Grant covering both Moffett
and the adjacent electronics industry Superfund sites. The Navy,
EPA, Cal-EPA, and the electronics companies have all considered the
Toxic Coalition's participation to be constructive. In fact, the
Federal Facilities Environmental Restoration Dialogue Committee--an
official EPA advisory group, of which I am a member--used the
Moffett experience as a model for public participation in the
oversight of cleanup. That model is not only being implemented at
Energy, Defense, and other federal agencies, but it has been
adapted and written into the Superfund Reauthorization legislation
section on public participation.
Local concern about environmental contamination has not been
confi ned to releases by the electronics industry, however. In
1981, large numbers of people opposed, unsuccessfully, government
plans to spray Malathion bait from helicopters to combat an
infestation by the Mediterranean Fruit Fly. Most of the local
governments in the area have passed stringent ordinances
restricting public smoking. The Bay Area Air Quality Management
District has instituted voluntary no-burn days to discourage the
use of wood-burning fireplaces and stoves. Storm drains in the area
are identified by "No Dumping, Empties into Bay" signs. Prompted by
Valley cities, the State Department of Pesticide Regulation
recently proposed rules to outlaw the sale of root-killers and
cooling system biocides, the use of which causes discharges of
heavy metals into the San Francisco Bay.
ASK THE COMMUNITY
Silicon Valley is probably in the forefront of local
initiatives to reduce the public health threat caused by
environmental contamination. Would decision- makers--private, as
well as all levels of government--make better decisions if the
relative risk of each form of contamination were better understood?
Silicon Valley activists are skeptical. They believe that the
national trend toward comparative risk assessment threatens to
weaken regulation and divert resources away from environmental
protection. However, I believe that trend is irreversible, so
communities such as Silicon Valley must figure out how to influence
the way that bureaucracies analyze risk or face a future in which
their concerns are ignored.
Therefore, I propose the creation of a community task force,
representing an ethnically and socially diverse cross-section of
educational, economic, political, and religious leaders, to
evaluate the full range of environmental threats to public health
in Silicon Valley. The task force would build on past studies, as
well as a wide range of medical and scientific expertise, but it
would be directed by representatives of the impacted population,
not by experts.
In addition to the Fairchild studies, a handful of other major
studies have looked directly at the public health impact of toxic
releases on Silicon Valley. In 1985, the EPA conducted an
integrated environmental study of public health in Silicon Valley,
and it found that smog, produced primarily by automobiles
throughout the Bay Area, and treated, imported drinking water posed
greater threats to public health than the risk posed by
industry-contaminated groundwater (2). Considering that tens of
millions of dollars had been spent confining toxic groundwater
plumes, I never found that controversial result surprising.
In 1988, a state study found no statistical link between
Valley birth defects and the aerial spraying of malathion (3). The
Semiconductor Industry Association investigated miscarriage rates
among its production workers, and in late 1992 it found a
substantially increased incidence among those exposed to ethylene
glycol ethers, even at legally acceptable levels (4).
I believe that a community-based environmental risk evaluation
in Silicon Valley would show that an informed community has done a
reasonable ad hoc job of characterizing and combatting
environmental risks. A more formal process, however, would not only
fine tune activities in Silicon Valley, but would help other areas
identify, rate, and respond to similar threats in a comprehensive
fashion. It would also help determine the different views of risk
held by educationally, economically, and culturally diverse
populations within the same geographic area.
It is conceivable, of course, that a formal risk evaluation
process in Silicon Valley would surprise me--that is, the process
might find that activists and policy-makers have been barking up
the wrong tree. If so, the process must be robust enough that the
result is respected and not viewed as the private tool of polluters
attempting to avoid paying for their crimes. Finally, the results
of the task force study could be used by decision-makers, at many
levels, to develop public policy. Because the Valley's cleanup
strategy and regulatory framework have been in place for many
years, it is unlikely that a new risk evaluation would make a major
difference in those areas.
In the field of pollution prevention, however, a great deal
remains to be done. The concept of pollution prevention is widely
understood and supported within the Valley, so if funds were
available--in the form of a federal grant, for example--the task
force could help officials channel resources to solve problems
currently identified by the community as a serious threat to
environmental and public health.
STRUCTURING A STUDY
The recognized success of the Moffett Technical Review
Committee, in which polluters, their public antagonists, and
regulators work constructively at the same table, should help
participants work together without the history of conflict and
mistrust significantly delaying the process. Because the task force
would be fact-finding and advisory, it would not be stealing
authority away from elected officials or appointed regulators.
Each constituency should be represented by a person focused on
these issues, but members need not be technical, medical, or legal
experts. The task force should be informed by two sets of
"experts." First, a quasi-neutral group of scientists would act as
staff to the task force. Second, representatives of advocacy groups
would be invited to explain their concerns and priorities.
Furthermore, other members of the public could put forward their
points of view, initially and in response to interim reports from
the task force, at a series of public forums.
I suggest that the task force attempt to reach consensus on a
descriptive matrix, evaluating each risk against a list of criteria
such as the fifteen I list below. Once the task force is
established, it would be free to revise the matrix in the
furtherance of its assigned task.
I have considered, and rejected, the creation of any type of
overall numerical ranking system. Any formula that tries to compare
diverse types of risks numerically will be unreliable and laden
with hidden values--it's like comparing Apples and supercomputers.
How does one compare one cancer against 10 miscarriages or a
thousand respiratory diseases? What if a response action designed
to protect one species destroys the habitat for another? Is it fair
to measure the risks from groundwater contamination, released
without the permission or knowledge of the local community, against
the risks voluntarily accepted by cleanup workers. Formulas
designed to make such broad comparisons quantitatively are
analogous to electoral reapportionment: everyone judges the tool
against his/her preconceived preferred results.
The goal is to provide a tool to make it easier for
decision-makers to consider specific courses of action based upon
their jurisdiction and values. From such a matrix, a single
agency--such as a regulatory body or a department with a unified
budget--might effectively develop and utilize a numerical ranking
system for risks or priorities, but the premature ordering of
actions is counterproductive.
For example, when the city of Seattle ranked its environmental
priorities, it excluded problems beyond its jurisdiction, such as
worker safety and health (5). A project designed broadly to protect
public health in Silicon Valley, however, would be an environmental
justice debacle. Declaring the subject off limits would undermine
working conditions for immigrants and other people of color at the
bottom of the Valley's industrial hierarchy. Furthermore, declaring
worker issues irrelevant or unimportant would reduce the value of
pollution prevention--reduced use of chemicals in high-tech
production--as a solution to off-site environmental problems.
The scope of such an evaluation is somewhat arbitrary. One
could consider a number of significant public health and safety
threats that are not principally environmental, such as auto
accidents, poor nutrition, earthquakes, family violence, or
infectious disease. But that would enlarge the magnitude of the
task enormously, with the results probably having little impact on
what today we call environmental policy.
I suggest a focus on environmental hazards that pose a threat
to public health or the survival of the remaining natural
ecosystems in the area. The following is not a complete list. In
fact, the task force may choose to divide the problems in a
different way. But it is exemplary of the types of environmental
problems that have been addressed, or at least considered, by local
policy-makers.
- Agriculture chemicals (pesticides, fertilizer, etc.)
- Automotive air pollution
- Fireplace smoke
- Fish/game consumption
- Friable asbestos in buildings
- Greenhouse gas generation
- Groundwater contamination (fuel)
- Groundwater contamination (industrial)
- Industrial air pollution
- Industrial gases/accidents
- Habitat encroachment
- Lead from plumbing in drinking water
- Lead paint in residences
- Release of ozone-depleting chemicals
- Soil contamination (industrial)
- Surface water contamination
- Tobacco smoke
- Treated water
Perhaps the greatest tension in risk assessment, as
traditionally practiced, is geographic. People who are directly
exposed to toxic substances in their workplace or drinking water
don't like being told, by experts or bureaucrats, that their
problem is minuscule in relation to environmental risks that
threaten the general population, such as global warming or
automotive air pollution.
Therefore, I propose an initial screening to divide the risks
into two lists. One list would deal with environmental risks to the
bulk of the population of the region or beyond; the other list
would identify problems or sites where the receptor population is
localized. On the localized impact list, each source site would be
identified and evaluated individually.
Each risk would be rated according to the following criteria.
If certain criteria prove confusing or impractical to apply, then
the task force could make modifications.
EVALUATION CRITERIA
1. Health--Toxicity Level. How hazardous is the
substance (or other hazards)? The U.S. Defense Department (DOD) has
proposed a risk evaluation methodology that helps communities to
transfer numerical, research-based tables into three categories:
significant, moderate, and minimal. DOD defines a Contaminant
Hazard Factor (CHF) that compares maximum site contaminant
concentrations in each media to risk-based standards. It presents
formulas that allow the evaluator to combine carcinogenic and
noncarcinogenic risks from more than one substance at the same site
(6). I don't think DOD always uses the right numbers, but I find
the process helpful.
2. Health--Type of risk. Although cancer risks are
often used to rate the seriousness of exposures, other types of
risks do not necessarily track cancer risks. It is often useful to
describe the potential impact of the substance: lethal, acute,
chronic, carcinogenic, mutagenic, etc. I don't even know the term
for substances, such as lead, that retard mental development.
3. Ecology--Toxicity. The Defense Department
methodology calls for a separate calculation of its CHF for
ecological receptors.
4. Ecology--Persistence. It isn't only important to
know the immediate impact of a contaminant. How long will it remain
in the environment? Is it bioaccumulative?
5. Migration. DOD's evaluation methodology provides
simple, comprehensible definitions for three levels of pathway:
evident, potential, and confined.
6. Human Receptors--Type and Quantity. Sometimes it
makes sense to lump together the entire affected population, but
often it is important to break it down by age (i.e., infants,
elderly, etc.) ethnicity, gender, or other factors appropriate to
the risk. For example, in evaluating the risk of chemical releases
in semiconductor manufacturing, it is important to know how many
women of childbearing age are involved. The DOD methodology, one
should note, does not attempt a quantitative measure. Instead, it
gives three possible Receptor Factors: identified, potential, or
limited.
7. Ecological Receptors--Type and Quantity. Here,
it may be more important to know what share of the population of a
species or other defined group is affected. A threat to a small
number of clapper rail, an endangered bird species found in Silicon
Valley baylands, would be considered serious, because so few
remain. The particular risks to migrating species may need to be
identified.
8. Range of source. In this category, each risk is
described by its breadth, not of exposure, but by where it comes
from. Recall that I have proposed that two matrixes be prepared,
one for risks that have a local impact, another for those of
general impact. That screening would be completed before any of
these criteria are applied.
Global: ozone-depletion is a good example;
Regional: such as automotive air pollution;
Multiple: underground storage tank leaks;
Unique: burning of solid rocket fuel at United
Technologies;
Combined: Are there other types sources in the same
area?
(This has been a concern in many poor communities, outside of
Silicon Valley, where polluting industries are concentrated.).
9. Timing. When do exposures occur? Are they
constant, frequent, occasional, or rare? Do they only occur during
work hours? Or perhaps only during the summer? Heavy metal
discharges from the electronics industry through the sewage system
pose the greatest threat during the dry season (most of the time
during the drought), when Bay flushing is minimal.
10. Economic Impact. Does the health threat or the
activity proposed to reduce it pose a threat to jobs, taxes, or
other economic objectives? Contamination of the southern San
Francisco Bay has destroyed commercial shrimp harvesting. On the
other side, some small electronics plants have been closed because
of their toxic releases.
11. Quality of Life. Many health threats also
undermine the quality of life. Visible air pollution is an obvious
example. Noise pollution may have a minor impact on health, but it
can be a major irritant. Some health risks themselves both
contribute and detract
from the quality of life, depending upon who is making the
judgement. Cigarette smokers claim to enjoy smoking, although I
would consider the smell of tobacco smoke a major irritant, even if
it were not a threat to my health. On the other hand, I love the
sight, smell, and sounds of a wood fire, even though it too may
pose a health risk. In some areas--particularly recognized native
lands--environmental hazards pose a threat to an entire way of
life. I don't know of any such major cultural impacts in Silicon
Valley, but it's worth exploring.
12. Jurisdiction. In deciding whether to take action
to reduce a risk, decision-makers must establish both legal and
practical jurisdiction. Does the body considering action have legal
responsibility? Is it in a position to take action? Is it owner or
responsible party or does it merely play a regulatory/oversight
role? Levels of jurisdiction include local, regional, state/tribal,
and federal. In some instances, international law, such as trade
agreements, may also come to bear. And even if a problem is local,
it may belong to or be better addressed by another local
jurisdiction.
13. Causality. Can the problem be prevented, is it
reversible, or is it irreversible? Is it already largely under
control, or is there little hope of controlling it? (EPA does not
consider groundwater contamination to be as serious as air
pollution in Silicon Valley but that is largely because protective
action, such as closing down wells, has already been taken.) Are we
at a turning point that would magnify any action?
14. Responsibility. We tend to support action based
upon our ability to assign responsibility. Can we identify the
perpetrators or is the blame generic or assignable only to the
taxpayer for remediation? Which of the following factors are
responsible for the problem: ignorance, negligence, malevolence, or
bad luck? Or is the problem natural or unavoidable? Are those
people principally at risk volunteering to take known risks (such
as smokers)? Are addicts volunteers?
15. Cost. Theoretically, decisions to reduce risk
are supposed to be based upon the cost per unit of reduced risk.
But it's more complicated. Requiring an electronics company to
clean up its groundwater may represent a slight cost for the
regulatory agency, but it may represent an enormous cost for the
polluter or its insurers. On the other hand, it's easier to ask
Intel or IBM to spend millions of dollars on cleanup than a small,
independent factory owner.
Some cleanup activities, such as source removal or
containment, make sense because they reduce long-term costs. And in
some instances, pollution prevention can actually save money by
saving energy, water, or other materials. That is, risk reduction
can actually be profitable. (More broadly, the high-tech
electronics industry would benefit from the perception of a clean
local environment because their chief factor in competition is the
ability to attract brainpower.)
My proposed risk evaluation matrix is not simple, because I
believe that simplistic analysis has been used to justify pollution
or, at least, continued exposure to pollution. It is my hope,
however, that the method is transparent or at least comprehensible.
I have attempted to include factors that most of us use in setting
environmental priorities, but which we do not always list,
particularly in the context of risk evaluation.
Our political system, imperfect as it is, takes into account
these external factors but not necessarily in a conscious way. By
channeling input through a representative task force of people
focused on these issues--not just leaders elected or appointed
based on other issues--it is possible either to reach consensus on
evaluated risks or at least to narrow the differences. If such a
body is given access to and control over its own expert
consultants, its conclusions would be more "correct," in a Platonic
sense, than if it were poorly informed.
Figure 1. San Jose Metropolitan Statistical Area Santa Clara
County
Risk-Based Site Evaluation Concept Summary
1. Susan Yoachum, "How Researchers Hunted Down Birth-Defect
Cluster," San Jose Mercury News, January 21, 1985. A later
state study argued that the contaminated drinking water was
not the cause, however. (Mitch Benson and
Rebecca Salner, "State Writes Off Tainted
Water," San Jose Mercury News, May 24,
1988.
2. Mitchel Benson and David Kutzmann, "EPA Calls Valley Water
Treatment, Air Pollution the Chief Cancer Risks," San Jose
Mercury News, October 12, 1985
3. Associated Press, "Birth-Defect Tie to Medfly Spray Weak,
Study Says," San Jose Mercury News, June 8, 1988.
4. Rebecca Smith, "Chip-Making Health Risks Found," San Jose
Mercury News, December 3, 1992.
5. "Environmental Risks in Seattle: A Comparative Assessment,"
City of Seattle Office for Long-Range Planning, October, 1992.
6. Risk-Based Site Evaluation Primer, Office of the Deputy
Under Secretary of Defense (Environmental Security), Summer,
1994 (Draft No. 2).
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