and Water Pollution
While air pollution
is the most visible and studied environmental consequence of transportation
system, water pollution and wetlands issues are also of crucial
importance in the transportation and environment nexus. Fuel, particle,
and salt-laden runoff from streets, highways, and storage facilities
results in damage to public water supplies, ponds, lakes and surface
streams, roadside soil, vegetation and trees, and infrastructure
and vehicles. The role of wetlands in water purification, the management
of surface water runoff, and wetlands as habitat preserves for numerous
species are all being closely studied.
Roadways tend to bisect watersheds. Water quality impacts attributed
to erosion, sedimentation, and polluted runoff associated with highway
construction, operation, and maintenance may be limited to the adjacent
streams. But in the watershed downstream, the impact from the road
may also contribute to other forms of water pollution. Watersheds
are therefore both directly and indirectly impacted by transportation.
It is for this reason that a watershed approach has become the most
widely accepted direction of study of most water and transportation
The main federal
legislation concerning water quality is the Federal Water Pollution
Control Act of 1972, as amended by the Clean Water Act (CWA) of
1977. This act along with its amendments regulates discharges of
pollutants from both point and non-point sources. The Environmental
Protection Agency (EPA) and many States have issued regulations
implementing the CWA goal of achieving and maintaining a high standard
of water quality in surface and ground waters. The CWA also recognized
the importance of wetlands.
The Clean Water
Act gives states the responsibility to monitor and assess their
waters and report the results to the EPA. Monitoring is also done
to fulfill specific regulatory requirements, such as those of the
National Pollutant Discharge Elimination System (NPDES) permitting
process. The Federal Highway Adminstration (FHWA) and the Environmental
Protection Agency (EPA) are intended to be proactive leaders working
in partnership with the states and local governments and resource
agencies to develop joint training sessions, research, and information
progress has been made in the last two decades in reducing some
of the most obvious water-related impacts of transportation, including
leaking fuel, petroleum from underground storage tanks, and solid
waste. Yet serious and new challenges remain.
sector's role in water pollution is neither well defined nor well
understood by scientists. Traditional water quality concerns have
focused on bacterial contaminants, oxygen depleting wastes and sediment
loads from human activities. As concerns transportation issues,
the source of water pollution originate from both non-point as well
as point sources.
The evaluation of ground water quality is complex and assessing
the quality of ground water resources has many elements. An accurate
and representative assessment of ambient ground water conditions
ideally requires a well planned and carefully executed monitoring
plan. Such plans are expensive and may not be compatible with state
administrative, technical, and programmatic initiatives.
often is discovered long after it has occurred. This means that
the practices of today may have effects on water quality well into
the future, well before we understand the full ramifications of
transportation and water issues.
The challenges of scientific evaluation
One reason for
the difficulty of studying water pollution due to transportation
is the slow movement of ground water through aquifers. Contaminants
in the ground water do not mix or spread quickly, but remain concentrated
in slow-moving, localized plumes that may persist for many years.
In some cases, contaminants introduced into the subsurface may be
detected several years later.
quality assessments are performed using comparable data groupings.
Data most closely approximating actual ground water quality conditions
(e.g., untreated ground water) are given special consideration in
these assessments. Scientists focus on organic compounds and metals
as most indicative of ground water degradation from transportation.
are usually cited as among the top contaminants. VOCs can be released
to the environment through a number of different ways. Generally,
organic compounds are released to ground water via disposal practices,
and fuel and oil spills. As reported in their 1996 State Water Quality
Reports, it was disposal practices that generated the most concern
among states concerning water and transportation.
compounds that pose the greatest threat to ground water quality
are those that are relatively soluble, not easily converted to the
vapor state, and not subject to chemical or biological degradation.
Their presence in ground water is becoming increasingly pervasive
and a cause for national concern due to the carcinogenic effects
of many of the organic compounds.
also ply an important role. The top five toxic pollutants (by volume)
generated by the transportation industry include xylene, glycol
ethers, toluene, methyl isobutyl ketone, and N-butyl alcohol. The
final phase of motor vehicle manufacture is painting. Various solid
and liquid wastes may be generated throughout painting operations.
The wastes are usually the result of paint application and drying,
cleanup operations, and disposal of leftover and unused paint as
well as containers used to hold paints. There are solvents used
to clean equipment and metal parts, and are used in many coatings
have been developed at the state level for evaluating the expected
impact from road construction. A prioritization system, which compares
the impacts of one outfall to another and makes a determination
of their overall impacts, was developed in the Prioritization Method
for Retrofitting Highway, prepared by the Water Quality Unit of
WSDOT in 1993. The prioritization system seeks to examine the type
and size of the water body to which stormwater will be discharged.
The system determines and assigns a value of expected impact on
water resources based upon a wide range of characteristics of the
the EPA, transportation affects water quality directly in four ways:
1) road construction and maintenance, including the creation of
impervious surfaces can adversely affect water quality due to faster
rates of runoff, lower groundwater recharge rates, and increased
erosion; 2) pollutants such as vehicle exhaust, oil, and dirt, and
deicing chemicals, are deposited to roadways and other impervious
surfaces; 3) leaking underground storage tanks release petroleum
to groundwater; and 4) oil spills, especially in the marine sector
affect the water quality of inland waterways and coastal areas.
and maintenance activities can have both direct impacts to both
supply and water quality characteristics of the project area. Dredging
is undertaken to improve navigation for water-borne transportation.
Damage to habitat can occur because of disturbance and removal of
bottom material and disposal of dredged material. The U.S. Army
Corps of Engineers dredges and disposes of about 200 to 300 million
cubic yards of material annually from congressionally-authorized
navigation improvement and maintenance projects.
permit applicants (e.g., port authorities, terminal owners, industries,
and private individuals) dredge an additional 100 million cubic
yards annually from navigation projects (i.e., ports, berths, and
marinas). Dredged material can be disposed of in open water or on
land. Open water disposal can alter bottom habitats, decrease water
quality, and adversely affect marine organisms. Each year approximately
60 million cubic yards of dredged material is disposed of in the
ocean at designated sites.
A variety of
impacts are possible, ranging from the erosion of disturbed soils
to the chemical pollutants associated with highway maintenance practices.
The operation of highways causes other potential pollution sources
created by the chemical and biological contaminants present in roadway
of surface transportation facilities creates impervious surfaces
which can harm water quality in a number of ways including:
roadways, runways, and parking lots can produce increased pollutant
loadings to wetlands and streams unless the runoff is treated.
An increase in the amount of impervious surfaces results in lower
recharge rates for groundwater.
Construction of surface transportation facilities contributes to
increased erosion, which also occurs as a result of increased runoff
from impervious surfaces.
Impervious surfaces are associated with all modes of transportation,
but are most extensive for the highway system and airports. The
growth in road mileage in the United States has been relatively
slow, increasing by 19 percent from 1945 to 1997. Lane mileage in
the United States has grown faster, from an estimated 2,693,604
miles in 1984 to 3,968,813 miles in 1997: a 47 percent increase.
Operation and maintenance of highways involves various activities.
Highway operations and maintenance also involves activities such
as painting of bridges, re-striping of highways, de-icing of roadway
facilities during winter weather conditions, and application of
pesticides to roadside vegetation.
and support facilities include motor freight terminals, bus yards,
fuel storage tanks, and auto fueling and service stations, all of
which have environmental impacts. Each of these activities is associated
with potentially harmful environmental impacts.
Since most highway
sections lie within or cross a watershed, all phases of project
development have the potential for impacting both surface and underground
water resources. Highway project planning, location, and design
activities can greatly influence future uses of water resources
in localities by determining patterns of growth, secondary development,
and water supply distribution.
water from transportation take two different forms. The pollutants
are either directly leaked into the natural water system, or pollutants
are air-borne and then deposited. Runoff pollutants from vehicles
include particulates and heavy metals from exhaust fumes, copper
from brake pads, tire and asphalt wear deposits, and drips of oil,
grease, antifreeze, hydraulic fluids, and cleaning agents. Indirectly,
vehicles also contribute to polluted runoff by carrying solids from
parking lots, urban roadways, construction sites, farms, and dirt
Use of deicing
chemicals facilitates travel during winter weather conditions, and
is particularly important for highways and airports. Rock salt is
the principal deicing agent used in winter road maintenance throughout
the nation. Environmental impacts of road salt include adverse effects
to roadside vegetation, harm to soil structure, and potential impacts
on drinking water and aquatic life. The actual amount of salt applied
to roads nationally is not known, but statistics on road salt sales
are available. Approximately 16 million tons of highway salt were
sold in 1997.
and anti-icers used in North America are based on glycols such as
ethylene glycol, diethylene glycol, and propylene glycol, while
runway and taxiway deicers are typically formulated with a combination
of urea, glycols, sodium formate, and/or potassium acetate. Glycols
are biodegradable but can reduce the oxygen available to aquatic
life in waters to which deicing and anti-icing fluids are released.
Urea degrades to ammonia and nitrate, which are toxic and can contaminate
drinking water. It is estimated that 11.5 million gallons of deicing
products are used annually in aviation.
another water quality issue associated with transportation. Facilities
such as gas stations, maintenance shops, service stations, and freight
terminals impact water quality through runoff of gas, oil, and dirt;
spills during refueling; waste releases to sewer systems; and cleaning
of freight tank interiors. Truck, railcar, and ship cargo interiors
that carry fluids must be washed, resulting in the output of spent
cleaning fluids, water treatment system sludge, and tank residues.
Deicing is a
significant contributor to highway runoff problems, particularly
in northern states where cold weather necessitates greater use of
de-icing chemicals. Rock salt is a common deicing agent used in
winter road maintenance throughout the nation. The use of road salt
allows highway travel during snow conditions and is important for
delivery of vital goods and services (including emergency support
vehicles which save lives) to large segments of the country. Although
salt is cheap and effective, it can cause rather serious adverse
environmental effects. The environmental impacts of road salt include
effects on roadside vegetation, harm to soil structure, and impacts
on drinking water and aquatic life.
The effect of
deicing runoff is not limited to roadside vegetation. In some cases,
90% of the salt applied to the streets enters the city the city
sewerage system and then local aquifers and watersheds in general.
Aquatic life in those water systems subsequently suffers.
facilities result in as much as 20 million gallons of oil leaking
into water sources each year. Underground storage tanks (USTs) are
used to store fuel at gas stations and other facilities, as well
as other chemicals, and can be a major source of groundwater contamination.
Releases from tanks and piping occur from corrosion of older, unprotected
steel tanks and piping, or from cracks in tanks made from other
and spillage during refueling are also responsible for accidental
releases. The UST regulations that EPA issued in 1988 established
action requirements for UST owners and operators, including the
requirement to clean up soil and groundwater as needed to protect
human health and the environment. EPA regulations required that
by 1998 all existing USTs have spill protection through catchment
basins, automatic shutoff devices, overfill alarms, and mandatory
corrosion protection for steel tanks and piping.
A number of
factors affect the probability of water pollution due to leaking.
Number of leaking underground storage tanks (USTs), type and quantity
of materials released from leaking USTs, spill protection mechanisms,
cleanup efforts initiated and completed, location of groundwater
table, sensitivity of local ecosystems, and treatment of drinking
water. There has been a decrease in the number of active petroleum
USTs in the U.S. as petroleum UST systems have been closed and environmental
standards have become stricter.
Office of Water)
can contribute directly to water pollution. Average daily traffic
also has a strong influence on the quality of runoff
in urban areas. Contaminants are deposited on roadway surfaces,
median areas, and rights-of-way from atmospheric fallout and vehicle
exhaust. During storm events, rainwater washes out atmospheric pollutants
and upon surface impact (or snowmelt) and picks up roadway deposits
and runs off into receiving water bodies. Because average daily
traffic levels are higher in urban areas than rural locations, pollutant
levels of water due to traffic are significantly higher in urban
patterns associated with continued road building spread pollution
over a larger area and reduce the ability of natural systems to
absorb polluted runoff. This generates a great deal of water contamination
through the filling and draining of wetlands, the removal of vegetative
buffers and trees and shrubs which contributed to water cleansing,
and increased use of lawn fertilizers. Suburban sprawl creates the
need for more driving which results in increased water pollution
The U.S. transportation
system is leading to the paving over of up to one-half of the land
area of our cities and suburbs in the form of roads, parking and
driveways. Paved areas and vehicle storage already account for more
developed space in the U.S. than does housing. Although comprehensive
studies of parking are rare, a commonly used planning rule is that
each motor vehicle registered in a region will occupy six parking
spaces: one at home, one or more for guests, one at the worksite,
one at one's place of worship or favorite weekend haunt, and one
at the mall.
The site below
contains one of the most comprehensive list of links to a wide range
of transportation-related environmental issues.
The Office of
Water of the US Environmental Protection Agency is responsible for
transportation and water issues. The graphic above links directly
to "The Quality of Our Nation's Water: Water Quality Report."
The Water Transportation and the Maritime Industries is directly
involved in water.
Office of Oceanic
and Atmospheric Research of NOAA
The Office of Oceanic and Atmospheric Research, the primary research
arm of NOAA, conducts and directs research in atmospheric, coastal,
marine, and space sciences through its own laboratories and programs,
and through networks of university-based programs.
III. Government Agencies and Sources
1. Federal Highway
Highway Administration (FHWA) provides policies, technical and research
assistance that incorporate water quality and transportation issues
together into a coordinated management approach. The FHWAs
environmental work is handled by several different offices.
Office of Intermodal and Statewide Programs is responsible for intermodal
and statewide planning, geographic information systems, the national
highway system, scenic byways, and bicycle and pedestrian programs.
The FHWAs Office of Highway Information Management maintains
data on motor fuel, vehicles, highway finance and road performance,
and other transportatation related data.
An important program run by the FHWA is the Transportation Environmental
Research Program (TERP). The purpose of TERP is to fund research
in transportation and environmental issues at universities and colleges.
TERPs research is designed to provide insight on the policy
decisions taken by the FHWA.
2. The United States Environmental Protection Agency
The EPA has a wide range of sources on water pollution related to
Branch of WSDOT
Branch is organized as part of the Design Office of the Washington
State Department of Transportation (WSDOT). The Branch is part of
the Environmental and Engineering Service Center. The purpose of
the Hydraulics Branch is to provide technical support in the disciplines
of hydrology and hydraulics. Technical support is provided to regional
2. Water Quality
Unit of WSDOT
The Water Quality
Unit of WSDOT's Environmental Affairs Office has the dual responsibility
of providing adequate mitigation for the water and sediment impacts
resulting from transportation projects while allowing WSDOT to conduct
its core business of constructing and maintaining transportation
The action plan
of the Water Quality Unit includes the following goals:
that provide water quality benefits (e.g., wetlands, aquatic ecosystems,
riparian areas, wellhead sites, etc.), and protect areas that are
susceptible to erosion (e.g., unstable soils, karst materials, landslide
areas, fragile stream banks).
develop erosion and sediment control strategies at the planning
and design state to be implemented during construction, and operation,
ensure the proper use, storage, and disposal of toxic substances
at construction sites and maintenance facilities; develop oil spill
contingency plans and clean up procedures.
identify watershed pollution reduction opportunities to reduce pollutant
concentrations and volumes entering surface waters.
promote the use of vegetative methods to control erosion and other
feasible methods to reduce pollutant loadings and total suspended
solids from reaching surface waters.
perform water quality monitoring to assess pollution load reduction
and changes in water quality.
State Department of Ecology
agreement has been reached between the Washington State Department
of Ecology and WSDOT. It can be viewed directly.
Agreement between The Washington State Department of Ecology and
the Washington State Department of Transportation Regarding the
Use of Water Quality Modification General Order (PDF file)
and Natural Resources Library specializes on the topic of transportation
issues in King County. Library hours are 9 a.m. - 5 p.m., Monday
through Friday. The librarys reference desks telephone
number is (206) 684-1129 and e-mail is email@example.com.
The library can be visited at 821 Second Avenue, Seattle, WA 98104-1598.
for Transportation and the Environment
The Center for
Transportation and the Environment (CTE) is a US Department of Transportation
University Transportation Center (UTC) and is located at North Carolina
State University. Through programs of research, education, and technology
transfer, CTE seeks to mitigate the impacts of surface transportation
on the environment.
Center for Transportation
and the Environment
at Institute for Transportation Research and Education (ITRE)
North Carolina State University
Centennial Campus Box 8601
Raleigh, NC 27695-8601
Main phone: 919-515-8899
Action Network website is one of the largest non-government collection
of website links to environment and transportation issues.
by Nathaniel Trumbull and Professor Christine Bae. Last updated