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Green Parking Lot Resource Guide by fdh56iuoui


									Green Parking Lot Resource Guide


INTRODUCTION ............................................................................... 1

CHAPTER 1: IMPACTS OF PARKING LOTS ........................................... 2

Environmental Impacts of Parking Lots .....................................................................................................2 

Costs of Parking Lots.......................................................................................................................................5

CHAPTER 2: “GREEN” PARKING LOT TECHNIQUES............................. 7

Planning Aspects .............................................................................................................................................7

On-Site Stormwater Management ..............................................................................................................8

Parking Surface Material Selection .............................................................................................................9 

Landscaping and Irrigation ...........................................................................................................................9 

CHAPTER 3: PLANNING ASPECTS ..................................................... 10

Municipal Parking Requirements ............................................................................................................. 10

Parking Lot Placement and Aesthetics.................................................................................................... 12

Linking Parking to Smart Growth ............................................................................................................. 13

CHAPTER 4: STORMWATER MANAGEMENT....................................... 14

Green Parking Lot Stormwater Management Techniques ................................................................. 14

BMP Pollutant Removal and Effectiveness ............................................................................................. 17

BMP Cost Considerations............................................................................................................................ 18

        Case Study 1: Stormwater Best Management (BMP)

        —Bloedel Donovan Park, Bellingham, Washington .................................................................. 20


Porous Pavement .......................................................................................................................................... 22

Alternative Pavers ......................................................................................................................................... 23

Design and Installation Considerations .................................................................................................. 24

Maintenance of Permeable Pavement .................................................................................................... 25

Infiltration & Pollutant Removal Effectiveness of Permeable Pavements ...................................... 27

Cost Considerations ..................................................................................................................................... 29

        Case Study 2: Parking Surface Alternatives—Heifer International, Little Rock, Arkansas 31

        Case Study 3: Parking Surface Alternatives—University of Rhode Island, Kingston,
        Rhode Island ........................................................................................................................................ 33

                                                      Green Parking Lot Resource Guide—February 2008                                                                i
CHAPTER 6: LANDSCAPING                                            AND IRRIGATION .................................... 35

Overview of Natural Landscaping and Irrigation ................................................................................. 35 

Environmental Benefits of Using Natural Landscaping and Associated Irrigation ...................... 38

Cost Effectiveness of Using Natural Landscaping ................................................................................ 40

        Case Study 4: Landscaping and Irrigation—Heifer International, Little Rock, Arkansas .. 42

CHAPTER 7: REDUCED INFRASTRUCTURE BURDEN ............................. 44

Regional Stormwater and Wastewater Impacts.................................................................................... 45

Cost Effectiveness ......................................................................................................................................... 45

        Case Study 5: Reduced Infrastructure Burden

        —Green Streets Program, Portland, Oregon ............................................................................... 47

KEY RESOURCES .................................................................................... 49

United States
Environmental Protection Agency
Office of Solid Waste and Emergenc Response (5101T)
February 2008

Recycled/Recyclable—Printed with vegetable oil based inks on 100% postconsumer,
process chlorine free recycled paper.

                                                                                                                          Table of Contents                       ii

“           reen” parking lot is a term increas­        Chapter 2 provides an overview of the
            ingly used to describe parking lots         benefits of green parking lot development
            that may incorporate a variety of           techniques, briefly describing major plan­
environmentally preferable features, includ­            ning, design, and material considerations.
ing a minimized footprint and/or impervi­
                                                   ■	   Chapters 3 through 6 provide detailed
ous surfaces, stormwater best management
                                                        information on specific elements of sus­
practices (BMPs), and alternative parking
                                                        tainable parking lot approaches including
surface materials. To date, however, informa­
                                                        planning and design approaches (Chapter
tion on green parking lots has been scattered
                                                        3), sustainable stormwater management
across planning, construction, stormwater,
                                                        techniques (Chapter 4), alternatives to
engineering, and landscaping resources. The
                                                        asphalt parking surfaces (Chapter 5), and
goal of this resource guide is to present the
                                                        water efficient landscaping and irrigation
fundamental planning and design concepts
                                                        (Chapter 6).
of a green parking lot and connect readers to
existing resources on the environmental ben­       ■	   Chapter 7 discusses how green parking
efits and cost effectiveness of green parking             lots can help municipalities reduce future
approaches. This document is expected to be             stormwater infrastructure and utility
particularly useful for local government of­            maintenance costs.
ficials involved in planning and development
                                                   Case studies are included throughout the
activities, as well as construction industry
                                                   guide to provide real world examples of
professionals (developers, project managers,
                                                   green parking lot techniques.
facility managers and other decision makers)
interested in green parking lot technologies.      Key resources consulted in developing this
                                                   guide are listed in the back of the document.
The guide is organized into seven chapters:
■	   Chapter 1 describes the environmental
     and cost impacts associated with conven­
     tional parking lots.

                                 Green Parking Lot Resource Guide—February 2008                      1

        arking lots are a ubiquitous feature        high rate and volume, negatively impacting
        of the American landscape. Perhaps          the surrounding ecosystem. Hence, parking
        because they are so commonplace,            lots degrade water quality, strain stormwa­
the significant environmental and cost im­           ter management systems, consume large
pacts associated with parking lots are often        amounts of land and resources, and enable
overlooked. In this chapter, we provide an          urban sprawl. Furthermore, materials used
overview of these impacts.                          to construct parking lots have a variety
                                                    of impacts on air, water, and biodiversity
ENVIRONMENTAL IMPACTS               OF              throughout their life cycle. Some of the major
PARKING LOTS                                        environmental impacts of traditional parking
The prevailing low-density American devel­          lots are described below.
opment pattern (i.e., urban sprawl) necessi­
                                                    Water Quality Impacts
tates reliance on automobiles, along with the
construction of parking lots to accommodate,        Parking lot runoff is a major contributor to
and many times overaccomodate, demand               non-point source pollution of our waterways.
for parking. As parking lots have become a          Conventional parking lots quickly move
dominant feature of urban and suburban              stormwater into receiving water bodies. As
landscapes, their environmental impacts             it flows across pavement, the water picks up
have also become increasingly apparent.             pollutants from the surface. This results in
                                                    large volumes of polluted runoff entering
Most parking lots are made of pavement—a
                                                    surface water and groundwater resources,
combination of asphalt concrete, the most
                                                    negatively affecting water quality.
widely used paving material in the United
States, and aggregates such as sand, gravel,        Contaminants in parking lot runoff can
or crushed stone. Pavement is an impervi­           originate from a variety of sources, includ­
ous, heat absorbing material that collects          ing the paving materials used to build them.
stormwater on its surface and does not allow        Recently, the U.S. Geological Survey (USGS)
it to filter into the soil, inhibiting the natural   pinpointed parking lot sealants as a signifi­
water cycle. With this in mind, parking lots        cant source of non-point source pollution,
have traditionally been built with the primary      specifically polycyclic aromatic hydrocarbons
goal of channeling stormwater into receiving        (PAHs), a known carcinogen that can be toxic
water bodies as quickly as possible, via means      to fish and wildlife.1 Automobiles are also a
such as gutters, drains, and pipes. As a result,    major source of pollutants in parking lot run­
runoff that is contaminated with many types          off, including antifreeze, oil, hydrocarbons,
of petroleum residues, fertilizers, pesticides,     metals from wearing brake linings, rubber
and other pollutants from parking surfaces          particles from tires, nitrous oxide from car
enters receiving waters at an unnaturally           exhausts, and grease.

                                                    CHAPTER 1—Impacts of Parking Lots                2
Water Supply Impacts                             ide (CO), volatile organic compound (VOCs),
                                                 polycyclic aromatic hydrocarbons (PAHs), and
Conventional parking lots consist of large ar­
                                                 carbon dioxide (CO2) during the manufactur­
eas of impervious surfaces that do not permit
                                                 ing process. The activities associated with
the infiltration of water into the soil. Unlike
                                                 the construction and maintenance of park­
natural conditions where rainwater filters
                                                 ing lots also generate emissions, typically in
into the ground, impervious surfaces halt
                                                 the form of dust, fumes, and equipment and
this process, inhibiting a watershed’s natural
                                                 vehicle exhaust. For example, the use of hot
hydrological cycle and preventing ground­
                                                 mix asphalt, a common process where the
water recharge. As a result, water tables are
                                                 asphalt is heated to extremely high tempera­
lowered, reducing streamflow during dry
                                                 tures prior to application, can cause health
periods, depleting water supplies, and exac­
                                                 problems for workers including headache,
erbating the negative impacts of droughts.
                                                 skin rash, fatigue, throat and eye irritation,
Stormwater Management                            breathing problems, and coughing. Diesel
Impacts                                          emissions from on-site equipment can also
                                                 cause similar health effects.2 In addition, the
According to the USGS, an impervious,            typical after effects of parking lot construc­
man-made surface will generate two to six        tion, such as fewer trees and less vegetation
times more runoff than a natural surface. In      due to clearing, as well as heat island effect
addition to the direct impact of paving, con­    (see below), also lead to higher amounts of
ventional parking lots also typically include    CO2 in the air.
pipes, curbing, gutters, and drains to help
speed water off of parking surfaces. These        Heat Island Effect
systems cause runoff to move even faster
                                                 Heat island effect (HIE) occurs in urban areas
downstream, increasing the risk of stream
                                                 where materials that have heat-absorbing
flooding. Sewer systems often become over­
                                                 properties, such as asphalt, are prevalent.
whelmed by the rapid runoff of stormwater,
                                                 In urban areas, the combined effect of such
causing them to overflow and, in the case of
                                                 surfaces can cause a change in the energy
combined sewer and stormwater systems,
                                                 (temperature) balance, leading to hotter air
discharge raw sewage into receiving water­
                                                 and surface temperatures. Recent research
ways. In addition to the human health risks
                                                 indicates that urban areas are 2 to 8ºF hotter
related to combined sewer overflows, these
                                                 in summer due to this increased absorbed
discharges can cause algal blooms to form,
depleting aquatic oxygen levels and altering
a waterbody’s habitat.                           Parking lots contribute significantly to HIE.
                                                 Asphalt, one of the most common paving
Air Emission Impacts                             materials used in parking lots, is a dark, heat
Pollutant air emissions occur throughout         absorbing material.4 When asphalt cools at
the lifecycle of a parking lot. Asphalt cement   night, all the heat it has absorbed during
plants emit particulate matter, nitrogen ox­     the day is released into the air, slowing the
ides (NOX), sulfur oxides (SOX), carbon monox­   rate of nighttime cooling. This hot surface,

                                Green Parking Lot Resource Guide—February 2008                     3
combined with stormwater runoff from the             fauna. The velocity and volume of runoff from
parking lot also affects surrounding water-          parking lots can damage plant, fish and inver­
bodies. When water is forced to flow quickly         tebrate habitat. During storm events, runoff
off the lot’s surface, not enough time is al­        can erode stream banks and alter the natural
lowed for evaporation to occur, again limiting      shape of a waterway. Stream edge habitat
natural cooling of the air. In addition, the land   and stream channel protection removed
clearing needed to create space for parking         during the construction of the parking lot
lots diminishes tree cover and other natural        increases the potential for erosion. Sediments
vegetation that can help shade land and             entering the waterway as a result of erosion
moderate temperatures.                              can smother habitat and stress aquatic organ­
                                                    isms. The turbidity created from the sedi­
The environmental impacts of the HIE are
                                                    mentation can disrupt an aquatic ecosystem
varied. Hotter temperatures can lead to
                                                    by diminishing light transmission, reducing
more CO2 emissions due to increased energy
                                                    plant growth, altering food supplies, interfer­
demand to cool neighboring buildings.5 HIE
                                                    ing with navigation, decreasing spawning
can also increase smog, and subsequently
                                                    habitat, and reducing shelter.
exacerbate pulmonary and cardiovascular
health problems. During rain events, paved          The contaminants in parking lot runoff also
surfaces can transfer heat to runoff, increas­       pose a risk to wildlife. Toxic substances from
ing the temperature of receiving waters. This       contaminated ground and surface water sup­
warmer water can be detrimental to the natu­        plies have the potential to bioaccumulate in
ral habitats of fish and other aquatic life.         the tissue of fish and other organisms in the
                                                    wildlife food chain. They can also accumulate
Waste Impacts                                       in sediments, posing risks to bottom feeding
The traditional production and application          organisms and their predators.
of asphalt relies heavily on the use of virgin      The impact of parking lots on water supplies
stone and aggregate and non-renewable,              affects local ecology. Unnaturally low stream
petroleum-based materials. Use of fresh             flows as a result of decreased infiltration
asphalt in parking lot construction creates a       can negatively impact deep water and swift
lost opportunity for reusing waste products,        flowing habitats. Impaired water quality, and
such as recycled asphalt, which would reduce        increased volume and velocity of runoff, can
the amount of material sent to landfills             lead to habitat loss, stress aquatic species,
and increase the amount of virgin materi­           and have an overall negative effect on bio­
als conserved. The use of recycled asphalt is       logical diversity in abutting areas.
common in the construction of roads, but
has yet to become prevalent in parking lot          Decrease In Greenspace
                                                    Greenspace is a finite resource with a wide
Disturbance of Habitat and Local                    range of intrinsic values, including conserva­
Ecology                                             tion, recreation, and agricultural purposes, as
                                                    well as its scenic qualities and contribution to
Traditional parking lots can have a host of         the overall character of a city or town. Proper
negative impacts on adjacent habitat and

                                                    CHAPTER 1—Impacts of Parking Lots                  4
management of greenspace is essential to            ing walking and bicycling, and encourages
achieving and maintaining sustainable com­          automobile travel, disconnecting communi­
munities. Nevertheless, greenspace areas are        ties and decreasing the habitability of cities
commonly paved to accommodate demand                and towns. The resulting increase in vehicle
for parking. For example, it is estimated that      miles traveled and the associated high levels
30 to 40 percent of a typical American down­        of mobile source air emissions exacerbate
town is used for parking spaces.6                   air quality issues, and contribute to global
                                                    climate change.
Ineffective local government zoning restric­
tions also result in the creation of larger areas   COSTS    OF   PARKING LOTS
of paved surface than necessary to meet the
parking demand. Many municipalities require         Beyond their environmental impacts, parking
a minimum number of parking spaces per              lots have economic and social costs related
development project, often forcing devel­           to their construction—costs that are often
opers to build more spaces than needed              much higher than consumers realize. More­
to meet actual demand. For instance, com­           over, parking costs are shouldered by many
mercial parking lots frequently have 60 to          stakeholders, including developers, local
70 percent vacancy rates.7 Parking stall sizes      governments, parking users, and community
required by zoning can also be larger than          members. Below we describe the types of
necessary, eliminating opportunities to alter       costs related to parking lot construction, as
parking lot configuration designs to achieve         well as who pays.
higher car capacity and minimize impervious
                                                    On-site Costs
surface area.
                                                    On-site costs include the construction, opera­
Conventional parking lots are often viewed as
                                                    tion, maintenance, and disposal of materials
unattractive, hostile, and sometimes unsafe
                                                    needed to develop and maintain parking lots,
areas. In contrast, green parking lots with
                                                    including paving materials and infrastructure
urban greenscaping provide aesthetic ben­
                                                    such as gutters and curb cuts. In addition,
efits, including privacy and noise reduction,
                                                    on-site costs include the cost of parking lot
to landowners and to communities. These
                                                    landscaping that, depending on the shrubs,
benefits are lost when conventional parking
                                                    trees, and turf chosen, vary in their need for
lot construction and paving techniques are
                                                    mowing, pruning, and irrigation. These costs
                                                    are typically paid by developers, although
Urban Sprawl                                        local governments sometimes subsidize
                                                    infrastructure costs. HIE can add to parking
Urban sprawl and prevailing low-density             lot user costs, by decreasing an automobile’s
development patterns characterized by free,         value by quickening the deterioration of the
plentiful parking reinforce dependence on           vehicle’s paint, plastics, and tires while on
automobiles for commuting to work, shop­            the lot. HIE can also shorten the life of the
ping, and social activities. Thus, conven­          pavement, causing it to become brittle and
tionally designed parking is an enabler of          weak (a cost to parking lot owners); and can
urban sprawl. Conventional parking creates          increase the energy costs of adjacent build-
barriers to alternative transportation, includ­
                                  Green Parking Lot Resource Guide—February 2008                     5
ings due to the hotter air temperatures (a          Distributional Issues
cost to the building owner and potentially to
                                                    Parking lots provide a value to consumers
third parties).
                                                    who use them, but result in negative im­
Infrastructure Costs                                pacts for neighbors and other community
                                                    members who do not use them. Community
Local governments bear the brunt of infra­          members would be better served by almost
structure costs related to parking. The high        any other land use, particularly in cases of
volume and velocity of polluted run-off from         excessive sizing of paved areas, which can
parking lots can stress stormwater man­             reduce adjacent property values.
agement systems and hasten the need for
repairs, upgrades, and expansions to handle         Community Development Costs
water flow and treat runoff. Flooding caused
                                                    Parking lots and associated sprawl decrease a
by runoff can also degrade bridges, roads,
                                                    community’s habitability, livability, and sense
and other parts of a city’s infrastructure.
                                                    of identity, a cost to all community members.
Additionally, groundwater shortages due to
                                                    Unattractive expanses of pavement placed
disruption of the water cycle can increase
                                                    in front of buildings create voids and discon­
the frequency, and thus cost, of pumping
                                                    nectedness, discouraging pedestrian-friendly
                                                    communities and alternative methods of
Opportunity Costs                                   transport. The presence of multiple conven­
                                                    tional parking lots can also signal develop­
Parking lots consume large areas of open            ers that a community accepts urban sprawl
space that could otherwise be used for              development. This signal can create a cyclical
alternative, higher value purposes, such as         effect on a community’s future development
parks, wildlife habitat, recreation, agriculture,   patterns. Subsequent developments in these
housing or other businesses. Building park­         areas are far more likely to have a similar pat­
ing instead of other types of development           tern of urban sprawl, further disconnecting
could reduce the property tax base, a cost          the link with any older non-sprawl develop­
to local governments and local taxpayers.           ment, and eroding or precluding unique
Enforced minimum parking requirements               characteristics that establish a community’s
do not benefit developers either. They limit         sense of place.
the development potential of land; the more
parking spaces that are required, the less land
available for more profitable uses. This can be
costly because parking is relatively expensive
to construct and yields little return, or no
return where parking is free.

                                                    CHAPTER 1—Impacts of Parking Lots                  6

    nnovative approaches to planning and           of transport, through company support or
    design can greatly mitigate many of the        subsidies. Another alternative is for mu­
    negative impacts of parking lots, includ­      nicipalities to institute an optional fee that
ing diminished recharge of groundwater,            developers can pay towards an appropriate
high rates of stormwater runoff, and non-           municipal fund, such as a traffic mitigation
point source pollution, by decreasing imper­       fund, in lieu of meeting minimum parking
vious surface area, protecting water quality,      requirements.8
reducing stormwater management and
                                                   Depending on the site, developers may not
maintenance costs, and increasing aesthetic
                                                   opt for constructing less parking because it
value. Below, we introduce green parking lot
                                                   may make a site less marketable. A technique
techniques, many of which are described in
                                                   applicable in this case would be to set park­
detail in subsequent chapters.
                                                   ing maximums and/or area wide parking
PLANNING ASPECTS                                   restrictions, which would limit the number
                                                   of spaces allowed across a larger area, eve­
Local planners regularly reinforce car depen­      ning the playing field for the marketability of
dence through zoning bylaws that, although         sites in the area.
meant to meet a community’s parking needs,
can result in an oversupply of parking. As a       Beyond reducing the number of parking
result, cities and towns are increasingly trying   spaces required, municipalities and develop­
new approaches to parking management               ers can also encourage practices that reduce
that allow for greater flexibility and adapt­       stall dimensions by creating more compact
ability by determining parking space num­          car spaces and realistic stall size require­
bers on a project-specific basis, rather than       ments. Some local zoning laws currently
through a one-size-fits-all regulation.             require unnecessarily large stall dimensions
                                                   that are bigger than even the largest SUV.9
One such technique is to reduce minimum            In many cases smaller, more realistic, stall
parking requirements based on project              sizes would be sufficient while reducing the
location or demographics. For example, local       amount of disturbed land and impervious
governments can encourage projects that are        surface associated with a project.
located near public transportation to reduce
the demand for parking spaces. Adaptations         Improving the aesthetic of the parking lot is
of this technique include municipalities           also a central technique in green parking lots.
allowing a reduction in the minimum park­          For instance, placing a parking lot behind a
ing requirements in return for a developer/        building rather than in front of it creates a
employer agreeing to implement a transpor­         more inviting and pedestrian-friendly envi­
tation demand management program to en­            ronment. Reducing the number of curb cuts
courage employees to use alternative modes         also decreases the frequency of pedestrian/

                                 Green Parking Lot Resource Guide—February 2008                      7
traffic interaction, thus making for a more
pedestrian-accessible area. These practices
aim to improve the character of the develop­
ment while maintaining accessibility to the
lot. Additionally, parking lots can be divided
into two or more parking areas, again project­
ing a more visually welcoming appearance.        Strategically sloped vegetated strips are a better option
                                                 than conventional grassy parking islands for collecting and
                                                 filtering runoff.
The impact of locating a parking lot at the
front of a building can be mitigated by          by 25-30 percent compared to conventional
providing ample space between the lot and        approaches.10
the road, and then creating a buffer with
                                                 Stormwater BMPs include structural controls
landscaping, fencing, or a wall. Landscaping
                                                 and bioengineering techniques designed to
inside the parking lot is also an important
                                                 facilitate natural water cycling processes (i.e.
technique. Beyond making the parking lot
                                                 evaporation, transpiration, and groundwater
more visually pleasing, vegetation and land­
                                                 recharge) by capturing, filtering, infiltrating,
scaping (including trees) around and inside
                                                 and/or storing stormwater. Components
the parking lot reduce HIE and help to absorb
                                                 of these soil- and plant-based systems can
CO2 emissions. Landscaping is discussed
                                                 carry out one or more of the aforementioned
                                                 functions, including some that store water for
Chapter 3 provides detailed information on       various durations (from 24 hours to perma­
green parking planning.                          nent storage). Examples of BMPs include
                                                 swales, vegetated buffer strips, and bioreten­
ON-SITE STORMWATER                               tion areas.
                                                 Unlike traditional stormwater management
Innovative stormwater management strate­         systems designed only for efficiency in storm-
gies are increasingly being incorporated into    water removal, which can lead to negative
parking lot design as part of the overarching    downstream effects, BMPs represent a shift
concept of Low Impact Development (LID).         towards a sustainable approach to storm-
LID stormwater techniques (also known as         water management. Thus, in the context of
Best Management Practices, or BMPs) man­         parking lots, BMPs add value by minimizing
age stormwater on-site, reducing negative        environmental impacts of runoff, and often
impacts on receiving waters and municipal        lower site development costs while improv­
stormwater management systems, and               ing aesthetics.
decreasing the need for costly infrastruc­
ture such as pipes, gutters, and curbs. Done     Chapter 4 provides detailed information on
on a small-scale, these controls attempt to      greener stormwater management and BMPs.
mimic the pre-development ecological and
hydrological processes of an area and can
reduce stormwater and site development
design, construction, and maintenance costs

                                       CHAPTER 2—”Green” Parking Lot Techniques                                8
PARKING SURFACE MATERIAL                            economical for developers than incurring
SELECTION                                           the rising costs in some states for disposal of
                                                    construction, demolition, and clearing debris
The negative impacts associated with large
                                                    in landfills.
impervious surface areas in parking lots can
be reduced through the use of new perme­            Chapter 5 provides detailed information on
able materials as substitutes for pavement.         greener choices for parking surface materials.
A number of paving substitutions have been
developed to reduce the range of environ­           LANDSCAPING        AND IRRIGATION

mental impacts associated with the use of           Green parking lot techniques work to mini­
pavement. Types of permeable and semi­              mize the amount of land cleared for construc­
permeable alternative pavers include gravel,        tion, conserving as much of a site’s natural
cobble, concrete, wood mulch, brick, open           vegetation and open space as possible,
jointed pavers filled with turf or aggregate,        and retaining habit for local wildlife. When
turf blocks, natural stone, and pervious            designing a parking lot area, landscapers
concrete.                                           can use native trees and shrubs rather than
Based on a site’s characteristics (i.e. traffic       non-indigenous species, which are more suit­
volume, soil type, climate etc.), alternative       able to local climates and, therefore, require
pavers may not be an option for the entire          less irrigation. The benefits of increasing the
surface of primary parking areas.11 However,        amount of greenscape in and around park­
in many cases, the aisles and driveways can         ing areas include reduction of CO2 in the air;
be constructed using conventional pave­             improved stormwater runoff management
ment, while alternative pavers can be used in       including water storage; increases aquifer
parking stalls, crosswalks, and overflow lots.       recharge and flood protection; and increased
Alternative pavers slow the flow of runoff,           human comfort through mitigation of HIEs.
allowing it to filter into the soil, sustaining an   Wetlands preservation or creation is particu­
area’s natural hydrological cycle, and in some      larly beneficial, as they can act as natural
cases, allowing microbes to break down con­         bioretention basins, providing water quality
taminants before entering the soil layer.           improvements, flood protection, and ero­
                                                    sion control. Wetlands also provide excellent
Opportunities for materials recycling ex­           habitat for local avian and fish species, and
ist in the management and construction of           are invaluable for water storage; one acre of
parking lots. For example, the use of recycled      wetlands can store over million gallons of
asphalt in parking lot construction is not only     water.12
environmentally beneficial, but can make
economic sense. Other environmentally pref­         Chapter 6 provides detailed information on
erable materials, such as recycled rubberized       green parking lot landscaping and irrigation.
asphalt, may also be used in parking lot con­
struction. Recycling materials can be more

                                  Green Parking Lot Resource Guide—February 2008                      9

          arking lot design and parking avail­      quantity of spaces in a parking lot. It is these
          ability are vital to transportation       regulations that manage a community’s park­
          management throughout the United          ing capacity, and thus a large amount of its
States. Parking availability may determine a        impervious surface area.
customer’s willingness to visit a business, and
                                                    Zoning requirements for developers to
it is often a sought after feature in urban resi­
                                                    provide off-street parking first began in the
dential areas. However, parking lots should
                                                    1930s as a solution to an on-street parking
be designed efficiently so that spaces are
                                                    shortage. Over the years, off-street parking
used frequently and not left empty a majority
                                                    requirements expanded in response to the
of the time. When developing a parking lot, a
                                                    population’s dependence on automobiles.
number of factors combine to determine the
                                                    Today, according to the U.S. Department of
lot’s size, layout, and design. These decisions,
                                                    Transportation, 87 percent of trips of less
made during the planning stages of a devel­
                                                    than 50 miles are made by personal motor
opment, can transform a parking lot from a
                                                    vehicles.13 Americans have become accus­
sparsely landscaped expanse of impervious
                                                    tomed to the availability of free parking and
paving to a space that is more aesthetically
                                                    automobile travel, rather than public transit
pleasing, land efficient, and community and
                                                    or other alternative methods, even for very
environmentally friendly.
                                                    short distance trips. Increased parking avail­
Local governments can use better park­              ability encourages more driving, more driving
ing planning as a tool to promote infill and         requires more parking, and so on.
smart growth developments while reducing
                                                    One of the most important local parking
the direct environmental impact of park­
                                                    ordinances addresses minimum space re­
ing. In many cases, revisions to zoning and
                                                    quirements, or parking ratios. Typically, local
other parking ordinances may be needed to
                                                    governments require developers to construct
achieve better parking planning. This chap­
                                                    the minimum number of parking spaces
ter provides a summary of parking planning
                                                    needed to satisfy peak demand. These mini­
considerations that have environmental
                                                    mum parking regulations often result in an
implications, including municipal parking
                                                    oversupply of parking. One study found that
lot regulations, parking lot aesthetics and
                                                    the average parking supply at worksites is 30
design, and the connection between parking
                                                    percent greater than peak parking demand.14
and smart growth.
                                                    In many instances, minimum parking require­
MUNICIPAL PARKING                                   ments are inflexible to adaptation or vari­
REQUIREMENTS                                        ances. Also, the methods to determine these
                                                    minimum parking requirements are often
In most urban and suburban areas, a num­            excessive and over-generalized, leading to an
ber of zoning laws govern the layout and            oversupply of parking.15 In addition, although

                                                            CHAPTER 3—Planning Aspects                 10
municipalities regulate the minimum number           City of San Francisco, where city planners
of parking spaces, they typically do not put         eliminated minimum parking require­
a cap on the maximum. Thus, developers               ments for development within a half mile
can frequently construct even more than the          of train stations and one-quarter mile of
required minimum, which is often the case            major public transit routes.17
at large retail developments, leading to a
                                                     Municipalities can also consider the land
further surplus in supply.
                                                     uses in the surrounding area. For instance,
In addition to requirements for the number           it is possible that existing nearby develop­
of spaces in a parking lot, regulations for the      ment and parking may already provide
size of each space are also common. Some             some of the parking necessary to sup­
local zoning laws require unnecessarily large        port a new development. Mixed used
stall dimensions that are bigger than even           developments often have natural parking
the largest SUV.16 In many cases, smaller            flexibility; an office where peak parking
stall sizes would satisfy parking needs while        demand occurs during the day can share
reducing impervious surface, and the entire          the same parking spaces with restaurants,
footprint, of the parking lot.                       entertainment venues, or residential units
                                                     that have peak parking demands at night
Re-thinking Municipal Parking                        and on weekends. Shared parking is also
Requirements                                         an option for single use developments in
There are a number of planning alternatives          mixed-use areas.18
to minimum parking requirements that lead­        • 	 Maximum Limits on Parking—The
ing local governments throughout the United           opposite of parking minimums, parking
States are implementing to minimize land              maximums limit the number of spaces
dedicated to parking. These include reducing          that a developer can construct, which is
minimum parking requirements; assessing               often determined by the development’s
parking needs on an individual project basis          square footage. Portland, Oregon is one
rather than using a generic formula; en­              city that has successfully implemented
couraging shared parking; and establishing            the use of parking maximums. Benefits
parking maximums, area wide parking caps,             of such a policy include open space
in-lieu parking fees, and reduced parking             preservation, reduction in impervious
space dimensions.                                     surface area, traffic congestion reduction,
• 	 Reduced minimum parking require­                  promotion of alternative transport, and
    ments—Parking requirements should                 the development of pedestrian-friendly
    be determined on a project-by-project             urban design. For developers, such limits
    basis instead of by formula, taking into          mean lower parking lot construction
    consideration how a project’s location can        costs.19 Similar policies include setting
    shape parking needs. This approach may            both a parking minimum and maximum,
    decrease the required parking capac­              or determining a median parking ratio.
    ity where there is accessibility to public    • 	 Area wide parking caps—Municipalities
    transportation and/or a high level of foot        can control the amount of parking by
    and bike traffic. Such was the case for the
                                 Green Parking Lot Resource Guide—February 2008                     11
   setting limits on the total amount of park­        stalls to achieve the greatest car capacity,
   ing spaces allowed in a certain area. This         again reducing the amount of land neces­
   strategy is being used in major U.S. cities        sary for the lot.
   including Boston and San Francisco. Such
   regulations require greater research and        PARKING LOT PLACEMENT              AND
   planning efforts by the city or town to          AESTHETICS
   ensure that the parking cap is appropriate      Parking lots have been described as “sterile,
   and reasonable, but if done properly, it        unattractive environments that deaden city
   can be very successful in minimizing the        and suburban streets alike, further isolate
   land area used for parking and encourag­        users and preclude lively pedestrian-friendly
   ing use of public transportation. This op­      streets.”24 Although all parking lots do not
   tion is appropriate for areas with adequate     match this description, many are eyesores
   access to public and alternative transpor­      that inhibit the usability and walkability of
   tation, as well as desirable location that      an area. Several techniques can be incorpo­
   would outweigh the perceived drawbacks          rated into the design and layout of a parking
   of more limited parking.20                      lot to improve aesthetics and help connect
• 	 In-Lieu Parking Fees—Towns such as             parking lots to community design. This not
    Berkeley, California, Lake Forest, Illinois    only benefits the user, but also the organi­
    and Orlando, Florida incorporated systems      zation or business adjacent to the lot, as a
    of in-lieu parking fees. This optional fee     more pleasing atmosphere will help draw in
    is offered to developers by municipalities      the public. Plantings around the perimeter,
    in-lieu of meeting minimum parking re­         especially trees and shrubs, can screen the lot
    quirements. This fee is typically allocated    from passer-bys and break-up the otherwise
    to an appropriate municipal fund, such as      continuous strip of asphalt and cars from
    a traffic mitigation fund.21 An alternative      the street to the parking lot. This can also be
    under the in-lieu system is that in return     achieved through the use of fencing or a wall.
    for the developer’s fee, the city provides     Vegetation can also be used to divide one
    existing centralized, off-site parking to the   large lot into two or more smaller lots, again
    new development’s tenants and visitors.22      increasing the site’s visual appeal. Equally
                                                   important, landscaping within the lot pro­
• 	 Reduced stall size requirements—               vides an environmental benefit by decreasing
    Adjusting a local government’s stall size      dust, wind, noise, glare and air pollution; and
    requirements may reduce impervious sur­        minimizing heat island effect.25
    face coverage as well. Alternatives include
    creating a certain number of compact           The placement of a parking lot is a simple,
    car spaces and/or limiting stall dimen­        yet fundamental feature that can improve a
    sions to feasible sizes. For example, in the   development’s attractiveness. A majority of
    town of Needham, Massachusetts, up to          parking lots are placed in the front of build­
    50 percent of off-street parking can be         ings, between buildings and streets, requiring
    reduced dimension spaces designed for          pedestrians and bicyclists to cross expanses
    compact cars.23 If possible, developers can    of parking in order to enter a building. Alter­
    also adapt the layout and angle of parking     natively, parking lots could be placed at the

                                                           CHAPTER 3—Planning Aspects                12
rear of a building, increasing the intercon-      States, and promoting sustainable land use 

nectedness between pedestrians and the            patterns. With many cities designed around
built environment. This simple zoning change      use of the automobile, planners are often
is incredibly effective in shifting the orienta­   presented with the conflicting challenge of
tion of a streetscape from cars to pedestrians.   promoting smart growth development while
This also helps give the community a greater      supporting the parking needs of a popula­
sense of place and interconnectedness. In         tion. Green parking planning approaches
recognition of such benefits, the City of Fort     support smart growth by creating more
Collins, Colorado requires that no more than      sustainable land use patterns and decreasing
50 percent of the parking for a retail devel­     the environmental impacts of conventional
opment be located between the principle           parking lot development. By promoting and
building and the primary abutting street.26       supporting alternative transport and com­
Limiting the number of curb cuts also makes       muting, local governments may reduce the
a parking lot more pedestrian friendly and        parking needs.
inviting. Furthermore, by minimizing the
                                                  A concept linked to smart growth is “transit­
number of vehicular entries to parking areas,
                                                  oriented development,” defined as develop­
pedestrian mobility is improved, and pedes­
                                                  ment placed within close proximity of public
trian/traffic is minimized.
                                                  transportation, designed to create walkable
LINKING PARKING         TO                        communities and alleviate traffic conges­
SMART GROWTH                                      tion and environmental impacts caused by
                                                  urban sprawl. When building parking lots,
Smart Growth is a state and local government      local governments can encourage or require
planning movement aimed at improving the          developers to incorporate features that help
long-term habitability and sustainability of      reduce automobile reliance, such as bicycle
cities and towns by minimizing environmen­        racks. Employers can support use of alterna­
tal impacts, improving human health, build­       tive transport options by subsidizing the cost
ing a sense of community, creating walkable       of public transit, encouraging participation
neighborhoods, promoting traditional and          in a commuting program, and/or providing
alternative transport, and preserving open        shower facilities on-site so that staff can bike
space. Most fundamentally, smart growth           to work.
entails moving away from the urban sprawl
development pattern common in the United

                                Green Parking Lot Resource Guide—February 2008                      13

          pivotal component of green park­         project alone can be minimal, but multiplied
          ing lots is the inclusion of innova­     by the current, and growing, number of
          tive stormwater management               commercial and residential parking lots, the
techniques, often referred to as stormwater        combined effect of stormwater runoff has be­
“best management practices” (BMPs). BMPs           come the leading cause of non-point source
are practices, techniques, and measures            pollution to our waterbodies.29
that prevent or reduce water pollution from
                                                   As discussed in Chapter 2, the environmen­
non-point sources (i.e. runoff ) using the most
                                                   tal effects of increased volume and velocity
effective and practicable means available.27
                                                   of stormwater include not only diminished
Stormwater management BMPs often include
                                                   water quality in surrounding waterbodies,
engineered, on-site systems that, when
                                                   but also:
coupled with reduction of impervious surface
area, can help significantly reduce detrimen­       • 	 Degradation of stream channels resulting
tal environmental effects and infrastructure            erosion and sedimentation;
burden from stormwater runoff.
                                                   • 	 Minimized groundwater recharge, which
Increased development and conventional                 can diminish water flow in the dry weath­
stormwater systems have significantly                   er, and lead to poorer water quality during
changed the characteristics of stormwater              low flows;
flow from land into receiving waters. Accord­
                                                   • 	 Higher water temperatures, which
ing to the Natural Resources Defense Council,
                                                       negatively impact aquatic organisms and
the amount of rain converted to runoff under
                                                       plants; and
natural conditions is less than ten percent of
the rainfall volume.28 However as more devel­      • 	 More frequent and severe flooding.30
opment occurs, rainwater or snow melt that
                                                   This chapter provides an overview of green
would have infiltrated into the soil, evapo­
                                                   parking lot stormwater management BMPs
rated into the air, or been absorbed by plants,
                                                   that can help mitigate these impacts, in­
instead flows quickly off of the pavement as
                                                   cluding information on pollutant removal
stormwater runoff. Moreover, conventional
                                                   efficiency and cost considerations.
stormwater management exacerbates this
problem. Conventional parking lot stormwa­         GREEN PARKING LOT STORMWATER
ter management typically consists of costly        MANAGEMENT TECHNIQUES
systems of man-made drains, pipes, gutters,
storm ponds, and paved channels that direct        Green parking lots offset environmental im­
runoff from impervious lots into storm drains       pacts of parking by using on-site stormwater
and neighboring waterbodies. The environ­          infrastructure that more closely mimics the
mental ramifications of one development             natural water cycle, and manages stormwater

                                                  CHAPTER 4—Stormwater Management                    14
through effective rainfall retention, pollutant     ter runoff, and often are incorporated to
removal, and water infiltration. Although still     pre-treat and remove sediment before
in the early stages of wide-spread implemen­       water enters infiltration devices such as
tation, cities and towns are recognizing the       bioretention areas.34 Other benefits in­
benefits of stormwater BMPs, and many have          clude protection of riparian areas, habitat
introduced both voluntary and mandatory            creation, and streambank stability.
policies for their inclusion in development
                                                   Vegetated filter strips are frequently used
                                                   in combination with riparian buffers, an­
Some of the most commonly used structural          other common BMP, to increase pollutant
BMPs are described below. It also should be        removal effectiveness. Riparian buffers
noted that incorporating BMPs is not lim­          are vegetated strips along waterways that
ited to new development. As illustrated by         trap and filter contaminants, encourage
the case study of building a rain garden at        infiltration, and slow stormwater flow.
Bloedel Donovan Park in this chapter, exist­       They also help to preserve streambank
ing parking lots can be retrofitted to include      stability.
                                                 • 	 Bioretention Areas (Rain Gardens)
• 	 Swales
                                                   One of the more well-know BMPs, biore­
   Swales are open channels or depressions         tention treatment areas (a.k.a., rain
   with dense vegetation used to transport,        gardens) consist of a grass buffer strip,
   decelerate, and treat runoff. In parking         shallow ponding area, organic layer, plant­
   lots, they are designed to help direct          ing soil, and vegetation. These areas are
   water into bioretention areas. Swales can       typically used in parking lot islands. Unlike
   come in the form of a grassed channel, dry      swales, bioretention areas are well-suited
   swale, or wet swale. They can be used in        for parking lots in denser, urban areas
   most climatic regions of the United States,     with less available open space.
   but may be unsuitable for densely urban
                                                 • 	 Dry Detention Basins
   areas as they require a large amount of
   pervious surface area.32                        A dry detention basin is a vegetated
                                                   basin with controlled outlets, designed to
• 	 Vegetated Filter Strips/Riparian
                                                   detain runoff (lowering flows and reduc­
                                                   ing velocity) for a short amount of time
   Vegetated filter strips are flat pieces of        (e.g. 24 hours or less), partially removing
   land with low slopes, which are designed        pollutants before the water is discharged.
   to encourage natural sheet flow of storm-        This helps limit flooding and other storm-
   water as opposed to channeled runoff.            water impacts, such as stream channel
   Vegetated filter strips are well suited for      erosion and wildlife habitat destruction.
   low-density development or areas with           Dry extended detention basins are better
   less concentrated amounts of runoff.33           suited for pollutant removal than standard
   They function by using soil and vegeta­         dry detention basins because they retain
   tion to remove pollutants from stormwa­         the water for an “extended” period of time

                                Green Parking Lot Resource Guide—February 2008                     15
  (i.e., up to 48 hours). They are effective           and filled with stone to form a subsurface
  at treating certain runoff contaminants,             basin, where water is stored until it infil­
  particularly those contained in spring              trates into the soil. This system greatly re­
  and winter runoff in colder climate areas.           duces the volume of runoff, and is particu­
  However, because water temperature                  larly good for groundwater recharge as it
  increases while in this type of system, dry         allows a significant amount of rainwater to
  detention basins discharge warmer than              infiltrate. Both of these BMPs are consid­
  natural water into waterbodies, which               ered effective for pollutant removal when
  should be taking into consideration. Both           used in conjunction with a pre-treatment
  dry detention and dry extended detention            BMP such as a swale. However, potential
  basins are normally dry between storm               drawbacks include higher failure rates
  events, thus giving them their name.35              due to improper design and maintenance,
                                                      limited site applicability, and increased
• Wet Retention Basins
                                                      sediment clogging.38
  Wet retention basins are designed to cap­
                                                      Porous pavement is another type of infil­
  ture, filter, store, and infiltrate storwmater,
                                                      tration technique used in green parking
  and have storage capacity adequate for
                                                      lots; as it is also an asphalt alternative, it
  flood volumes of water. Because they have
                                                      is discussed in Chapter 5: Parking Surface
  the capacity to store a permanent pool of
  water, wet basins can be very effective for
  water control, and can provide the bene­         • Constructed Wetlands
  fits of aesthetic value and wildlife habitat,
                                                      Constructed wetlands are designed to
  both terrestrial and aquatic. Although not
                                                      capture, filter, and store stormwater simi­
  suitable for smaller areas because of their
                                                      lar to a wet retention basin. However, they
  size, when applicable, retention basins are
                                                      also contain a large quantity of wetland
  a very effective BMP.36
                                                      vegetation and have wetland channels.
• Infiltration Systems                                 Although they are not built to replicate all
                                                      of the ecological functions of wetlands,
  Infiltration systems are designed to
                                                      constructed wetlands help simulate the
  capture and retain stormwater runoff,
                                                      natural water cycle, recharge groundwa­
  allowing water to gradually infiltrate into
                                                      ter, remove pollutants, reduce erosion,
  the ground over a period of hours or days,
                                                      and provide wildlife habitat. They are
  depending on the design.37 Two common
                                                      considered to be a very effective pollutant
  infiltration systems used in green parking
                                                      removal option.39 Constructed wetlands
  lots are infiltration basins and infiltration
                                                      have a few limitations; they are not ap­
  trenches. An infiltration basin is an open
                                                      plicable in arid climates and, due to their
  depression that covers a relatively large
                                                      large size, they are not suitable for dense
  area. It is constructed to work in conjunc­
                                                      urban areas.
  tion with filter strips or swales, which help
  direct runoff from a parking surface into         It is not necessary for developers to in­
  the basin. Infiltration trenches are shallow      corporate all available green stormwater
  excavated ditches lined with filter strips        techniques into a project; rather, they should

                                                  CHAPTER 4—Stormwater Management                      16
determine those useful for specific site condi­    source of pollutants in parking lot runoff, in­
tions. Considerations should include all fac­     cluding antifreeze, oil, hydrocarbons, metals
tors that affect the amount, speed, and pol­       from wearing break linings, rubber particles
lutant loadings of runoff: soil type, the slope    from tires, nitrous oxide from car exhausts,
and landscape of the site, amount of impervi­     and grease. Other polluting materials include
ous surface, local precipitation patterns, and    pesticides, fertilizers, litter, pet waste, dirt,
rainfall surface retention.40 Carefully choos­    and sand.45
ing the appropriate BMP(s) is important to
                                                  One of the main goals of a green parking lot
avoid any secondary environmental impacts
                                                  is to decrease pollutant levels in stormwater
caused by the use of an inappropriate BMP.
                                                  runoff as much as possible before it enters a
BMPs should address peak discharge, runoff
                                                  waterbody. Exhibit 1 shows a range of pol­
volume, infiltration capacity, base flow levels,
                                                  lutant removal efficiencies for selected BMPs.
ground water recharge, and maintenance of
                                                  Understanding the effectiveness of each BMP
water quality, so that they are ideally man­
                                                  for pollutant removal is a complex undertak­
aged in the pre-development stormwater
                                                  ing because pollutant removal is affected by
filtration conditions of the site.41
                                                  a large number of variables. Fundamentally,
It should be noted that BMPs are helping to       removal effectiveness depends on: 1) BMP
meet the Clean Water Act’s mandate to “re­        type, 2) the quantity of runoff treated, and
store and maintain the chemical, physical and     3) the type of pollutant being removed.46
biological integrity of the Nation’s waters”.42   Variation in one of these factors can affect
By 2025 the U.S. population is predicted to       a BMP’s efficiency. For example, infiltration
grow 22 percent, which could mean an ad­          trenches show a high pollutant removal ef­
ditional 68 million acres of development, a       ficiency for pathogens, but much lower for
good fraction of which will be dedicated to       phosphorus. However, these effectiveness
parking.43 Thus, BMPs may play a larger role      ranges can vary based on the climate, soil,
in the future to mitigate non-point water         and land type of a particular site. Infiltra­
pollution.                                        tion trenches may be less effective in colder
                                                  climates when surface waters freeze and can­
BMP POLLUTANT REMOVAL                 AND         not allow runoff to flow into them, a limita­
EFFECTIVENESS                                     tion that can be partially remedied through
Stormwater can carry a number of harmful          proper design and maintenance, but may still
pollutants, and is the prime contributor to       reduce pollutant removal effectiveness.47
non-point source pollution. Runoff contami­        As seen in Exhibit 1, not all BMPs have a high
nants can originate from a variety of sources,    level of pollutant removal effectiveness.
including the paving materials used to build      Instead, they serve other roles in control­
the parking lots. Recently, the USGS pin­         ling the impacts of runoff. This is the case for
pointed parking lot sealants as a large source    dry detention basins, which serve to reduce
of non-point source pollution, specifically        peak discharges of stormwater to neighbor­
polycyclic aromatic hydrocarbons (PAHs), a        ing waterbodies, as well as limit erosion and
known carcinogen that can be toxic to fish         downstream flooding.
and wildlife.44 Automobiles are also a major

                                Green Parking Lot Resource Guide—February 2008                        17
                                       Typical Pollutant Removal Efficiency (percentage)
         BMP Type                     Suspended
                                                        Nitrogen         Phosphorus          Pathogens         Metals

 Dry Detention Basins                30-65            13-45           15-45               <30                15-45
 Retention Basins                    50-80            30-65           30-65               <30                50-80
 Constructed Wetlands                50-80            <30             15-45               <30                50-80
 Infiltration Basins                  50-80            50-80           50-80               65-100             50-80
 Infiltration Trenches/
                                     50-80            50-80           15-45               65-100             50-80
 Dry Wells
 Grassed Swales                      30-65            15-45           15-45               <30                15-45
 Vegetated Filter Strips             50-80            50-80           50-80               <30                30-65

 Source: U.S. EPA, 1993, Handbook Urban Runoff and Pollution Prevention Planning, EPA-625-R-93-004, taken from Purdue Uni­
 versity Engineering Department’s Long-Term Hydrologic Impact Assessment (L-THIA):

BMP COST CONSIDERATIONS                                       constructing a BMP considerably because of
                                                              excavation costs.
Innovative structural stormwater BMPs are
more effective than conventional storm-                        Another significant variable in the compara­
water management in removing pollutants                       tive cost of BMPs is the value of land; in areas
and maintaining the environmental quality                     where real estate prices are high, construct­
of a site. However, because some of these                     ing a BMP may take up too much space to be
techniques are relatively new and have not                    cost effective.49 BMPs operation and mainte­
achieved market penetration, it is not clear                  nance costs can also be significant. The long-
their costs compare to conventional storm-                    term cost to maintain certain, more complex,
water management approaches.48 Calculating                    stormwater BMPs over a 20-25 year period
the cost-effectiveness of a stormwater BMP                     can be close to its initial construction cost.50
is a very site-specific endeavor, and current                  However, some BMPs, such as swales and
cost information is limited and inconsistent.                 bioretention areas, are less expensive to build
The main factors affecting the relative costs                  than their conventional counterparts of pipe
of BMPs include the cost of land, engineering                 and gutter systems. These BMPs can decrease
and design, permitting, construction, and                     development costs by reducing or eliminat­
operation and maintenance. These costs can                    ing the high cost of conventional stormwater
vary greatly due to individual site characteris­              infrastructure such as piping, gutters, and
tics such as climate, topography, government                  drains, as well as reduced long-term mainte­
regulations, soil type, time of year of con­                  nance costs for such systems. Furthermore,
struction, drainage, accessibility of equip­                  some BMPs, such as constructed wetlands,
ment, and economics of scale. For instance,                   may increase the property value by creat­
very rocky soils may increase the cost of                     ing a water feature and vegetation that has

                                                           CHAPTER 4—Stormwater Management                                  18
high aesthetic value. Developers may also       protect the health of waterbodies, but also
gain from local government incentives that      because they can avoid long-term costs.
encourage incorporating structural stormwa­     Without stormwater BMPs, many waterbod­
ter BMPs. For instance, the City of Portland,   ies and water infrastructure may deteriorate.
Oregon will give up to a 35 percent discount    Taxpayers bear the cost burden to slow
off its stormwater utility fee to properties     or repair damage caused by downstream
with on-site stormwater management.51 In        flooding, stream and aquatic habitat dete­
addition, some costs are tax deductible, and    rioration, and repairs and upgrades to worn
operating costs may be fully deductible as      town stormwater infrastructure systems, all
expenses in the year they are incurred.52       of which are very expensive and time-con­
                                                suming.53 Infrastructure costs associated with
Although the costs of BMPs vary by site and
                                                stormwater management and how green
type, they are almost always a good invest­
                                                parking can help mitigate these costs are
ment from the perspective of local govern­
                                                discussed further in Chapter 7.
ments and taxpayers, not only because they

                               Green Parking Lot Resource Guide—February 2008                    19

Stormwater runoff in Bellingham, Washing­
ton, like much of the U.S., is a foremost water
quality issue. The Washington Department of
Ecology estimates that roughly one-third of
the state water bodies with pollution related
problems are impaired because of stormwa­
ter runoff impacts. In an effort to protect the
receiving waters of nearby Lake Whitcom
from such impacts, City of Bellingham of­
ficials chose to retrofit stormwater manage­
ment at the heavily used Bloedel Donovan
Park parking lot. Rather than choosing a
conventional technique, they elected to build
an innovative rain garden to manage storm-          The raingarden in Bloedel Donovan Park helps protect the water quality in nearby
                                                    Lake Whatcom, and recharge groundwater supplies.
water on-site.
                                                        of drain rock, and topped with a layer of
DESIGN    AND    CONSTRUCTION                           fabric to constrain the sand and restrict
Designed on a 550 square-foot section of the            any plants from growing through. An
parking lot near the catch basin, the park’s            18- to 24-inch layer of sand composed of
rain garden supports runoff from 80 parking              twenty percent organic materials is the
spaces and two parking lanes. To meet water             top layer .
quality guidelines, the rain garden was also        • Landscaping—For landscaping, the city
designed to treat 91 percent of the runoff             chose native plants that could survive the
from a 50-year storm event. Aspects of its            year-round climatic conditions of the site.
construction included:                                This included plants that prefer wet soil,
• Site excavation—From site topography
  	                                                   but could also tolerate drought.
  and soils logs, the city determined the
  maximum allowable depth for water to              EXHIBIT 2: CASE STUDY INITIAL
  pond in the rain garden. Under a 50-year          COST COMPARISON
  storm event, the depth should be no more
                                                     Conventional stormwater
  than six-feet. Thus, the site was excavated        technique                                      $52,800
  three to four feet.                                (4,400 ft3 wet vault)
• 	 Layering of materials—The rain garden            Rain Garden                                    $12,820
    is composed of three layers of non-woven         Cost Savings                                  $39,980
    geotextile fabric alternated with six inches

                                                   CHAPTER 4—Stormwater Management                                               20
COST AND POLLUTANTS REMOVAL                         in-ground storage and treatment stormwa­
EFFECTIVENESS                                       ter system (see Exhibits 2 and 3). This was
                                                    achieved through reduced construction and
The benefits from incorporating this rain
                                                    equipment costs, as well as reduced labor
garden are numerous. It adds aesthetic value
                                                    costs from the relative ease of installation,
to the site, increases wildlife habitat, and is a
                                                    some of which was accomplished by volun­
highly effective BMP for treating stormwater
                                                    teer landscaping help. These costs savings do
runoff. According to officials at the Belling­
                                                    not include future regular maintenance costs.
ham Public Works Department’s, monitoring
shows that approximately 80 percent of total        A more detailed case study of the city of
runoff is captured by the rain garden, with          Bellingham’s rain garden can be found
overflows running through media filtration            on the Puget Sound Action Team’s Web
and then another infiltration bed. Further­          site at
more, Bellingham saved 70 percent in initial        Rain_Garden_book.pdf.
costs compared to installing a conventional


           Labor                                                          $3,600
           Vehicle use                                                     1,900
           Amended soil                                                    1,650
           Concrete                                                        1,200
           Asphalt                                                         1,200
           PVC/grates/catch basins/fabric/other misc.                      1,000
           Washed rock                                                       805
           Excavator rental (1.5 days)                                       500
           Plants                                                            400
           Debris Removal                                                    300
           WCC crew planting time                                            265
           Total Cost                                                   $12,820

                                  Green Parking Lot Resource Guide—February 2008                    21

        he majority of parking lots are made         Permeable pavements provide a sustainable
        of a combination of asphalt concrete,        alternative to the conventional asphalt and
        the most widely used paving material         concrete parking materials widely used today.
in the United States, and aggregates such as         Permeable pavements are a broadly defined
sand, gravel, or crushed stone. Conventional         group of pervious paving options that allow
pavement is an impervious, heat absorb­              natural infiltration rates of stormwater into
ing material that collects stormwater on its         the soil through certain design techniques
surface, and does not allow it to filter into the     and material substitutions.58 For this reason,
soil, inhibiting the natural water cycle. As a re­   like many of the techniques mentioned in
sult, parking lots must be designed to quickly       Chapter 4, permeable pavements are consid­
remove the water that gathers during storms          ered a best management practice (BMP) for
by channeling it off the lot via means such           stormwater management. However, perme­
as gutters, drains, and pipes. The stormwater        able pavement should be used in combina­
is directed into receiving water bodies at           tion with other BMP techniques to magnify
unnaturally high rates, causing a number of          benefits and provide back-up systems in case
adverse impacts including increased down­            of BMP failure.59 Two basic types of perme­
stream flooding, combined sewer overflow               able paving designs exist: 1) porous pave­
events, diminished groundwater supplies,             ment and 2) alternative pavers. This chapter
streambank erosion, and non-point source             describes these permeable pavement alterna­
water pollution from runoff contaminated by           tives, considering their functionality, infiltra­
vehicular residues and other pollutants.             tion and pollutant removal effectiveness, and
                                                     cost implications.
To combat several of the negative impacts
of conventional parking lot paving, develop­         POROUS PAVEMENT
ers are increasingly incorporating modest
changes, such as using light colored concrete        Porous pavement is a permeable pavement
instead of asphalt to reduce heat-island             surface, often built with an underlying stone
effect, or using recycled rather than virgin          reservoir, which temporarily stores storm-
asphalt to reduce emissions and natural re­          water before it infiltrates into the underlying
source consumption. For example, 80 percent          soil.60 Porous pavement works by eliminating
of asphalt pavement removed each year                the finer aggregates typically used in con­
during widening and resurfacing projects is          ventional paving, and binding the remain­
reused, with contractors typically incorpo­          ing aggregates together with an asphalt or
rating up to 20 percent recycled material in         Portland cement binder. By eliminating finer
concrete mixes.55, 56 However, these changes         aggregates, a less dense material is created
do not address the fundamental problem of            that allows stormwater to seep through. The
parking lot impermeability.57                        underlying stone bed is designed with an
                                                     overflow control structure, helping to ensure
                                   CHAPTER 5—Alternative Parking Surface Materials                      22
that water does not rise to the pavement          significant downstream benefits.66 Although
level. Stormwater settles in the empty spaces     porous pavement looks very similar to con­
of the storage bed, infiltrating over time into    ventional pavement, it is a far more sustain­
the subgrade soils—a process similar to an        able alternative, considered by experts to be
infiltration basin.61                              the most effective and affordable technique
                                                  for addressing stormwater management
The most common types of porous pavement
                                                  from development.67
are porous asphalt and pervious concrete,
which are very similar in their design and        Porous pavements typically have a greater
applicability.                                    spectrum of uses than alternative pavers
                                                  (discussed below), as porous pavement
• Porous Asphalt—Developed by the
                                                  can be applied to both low vehicular traffic
  Franklin Institute in the 1970s, porous
                                                  areas and some medium traffic areas. Porous
  asphalt consists of an open-grade coarse
                                                  pavements also have been used in a few high
  aggregate, bonded together by a typical
                                                  traffic areas, including some highway applica­
  asphalt cement in which fine aggregates
                                                  tions, because the product can provide better
  have been reduced or eliminated, allow­
                                                  traction than conventional pavement and
  ing water to move through the small voids
                                                  reduce hydroplaning.68 Ongoing research is
  created.62 Porous asphalt can be used in
                                                  working to improve its highway applicability
  all climates where conventional asphalt is
                                                  through the use of additives and binders.69
                                                  In addition, porous asphalt may help reduce
•	 Pervious Concrete—Pervious concrete            noise levels from tires on pavement. In a
   was developed by the Florida Concrete          study measuring acoustical properties of
   Association. It typically contains a mixture   pavement types, porous asphalt was shown
   of Portland cement; uniform, open-graded       to have lower noise levels than conventional
   coarse aggregate; and water. There is at       hot mix asphalt.70
   least 15 percent more void space in pervi­
   ous concrete compared to conventional          ALTERNATIVE PAVERS
   pavements.64 Pervious concrete can be          Alternative pavers, also known as perme­
   more durable than porous asphalt, par­         able pavers or unit pavers, are interlocking
   ticularly in hot weather. However, the State   concrete blocks or synthetic fibrous grids
   of Pennsylvania’s Department of Environ­       with open areas filled with grass, sand, or
   mental Protection has noted that in colder     gravel. Unlike concrete or asphalt poured-in­
   northern and mid-Atlantic climates, porous     place paving surfaces, alternative pavers are
   concrete parking lots should always be         separate units laid out on a prepared base.71
   designed with a stone subbase for storm-       When built with a storage bed infiltration
   water management, and should not be            system, alternative pavers function similarly
   placed directly onto a soil subbase.65         to porous paving systems. The voids between
The manufacturing process for porous pave­        the interlocked pavers allow stormwater from
ment has the same environmental and health        a parking lot’s surface to collect and then
impacts as the process for conventional pav­      seep into the storage bed, which is made of
ing materials, but porous pavement exhibits       sand or crushed stone. The water then gradu-

                                 Green Parking Lot Resource Guide—February 2008                   23
ally infiltrates over time into the subgrade        last 15 to 20 years, a length similar to con­
soils. In addition to stormwater management,       ventional asphalt concrete pavement, which
the storage bed also provides added struc­         requires resurfacing after 20 years on aver­
tural support to the pavers.72 As with porous      age.78 However, a number of factors need to
pavements, the most beneficial element of           be assessed when determining whether a site
alternative pavers is the reduction or elimina­    is suitable for a permeable paving system, in­
tion of stormwater impacts.73                      cluding: slope, traffic volume, subgrade, land
                                                   use, soil, infiltration and drainage characteris­
A number of alternative paver options are on
                                                   tics, and groundwater conditions.79
the market, including but not limited to: Turf-
stone®, UNI Eco-Stone®, Checkerbox®, Grass­        Compared to conventional asphalt surface
pave2®, and Gravelpave2®. Of the alternative       installation and design, features such as sub-
paver options, grass paving systems are the        grade, soil type, and installation requirements
most permeable. However, they have more            are more complicated for permeable paving
limited applicability because grass cannot         systems.80 For example, soil, including its
survive daily traffic; thus, grass-based systems     type, porosity, and stability, is considered one
are typically used for emergency fire lanes or      of the most important factors to determine
temporary overflow parking areas.74 Pavers          site suitability. According to the New York
should be filled with fine gravel or other per­      State Stormwater Design Manual, developers
meable materials when more frequent park­          must ensure that soils are permeable enough
ing is expected.75 It should also be noted that    to carry out adequate infiltration by consider­
certain types of alternative pavers, including     ing the natural qualities of a soil type as well
block, grid pavers, and gravel, are not always     as past land uses, because previous grading,
suitable for handicap accessible areas.76          filling, compaction, and other disturbances
                                                   of the land can alter soil infiltration qualities.
DESIGN AND INSTALLATION                            Underlying soils should have a minimum infil­
CONSIDERATIONS                                     tration rate of 0.5 inches per hour to accom­
A number of uses for permeable pavement            modate stormwater volumes, and knowledge
exist beyond new, whole parking lot con­           of the organic matter content of the soil is
struction projects. One option for high traffic      also important in determining its pollutant
parking lots is to design a hybrid parking lot     removal capabilities.81
combining permeable pavement parking               Permeable pavement is meant to treat small
spots with more conventional paving in the         storm events, which can range from 0.5 to 1.5
aisles.77 In addition, permeable pavements         inches. A site must be designed with an ad­
can be used during parking lot retrofits and        equate ratio of infiltration area to impervious
replacements.                                      area, and the soil should have a permeability
According to the U.S. Department of Trans­         of between 0.5 and 3.0 inches per hour in
portation, permeable pavements must be             order to adequately handle stormwater.82 Oc­
properly sited, designed, and installed in         casionally, exceptions can be made to allow
order to function fully over their life span. If   for permeable paving when sites do not meet
planned correctly, permeable pavements can         certain criteria. For instance, permeable pave-

                                  CHAPTER 5—Alternative Parking Surface Materials                      24
ment can be used in soils with low porosity       that if properly installed, success rates for a
if a discharge pipe is installed to run from a    permeable paving system, particularly po­
storage area to a conventional stormwater         rous asphalt, can be much higher than earlier
system. This modified system will still treat      installations using these materials.88
stormwater from small and medium storms,
but also will prevent flooding during large        MAINTENANCE         OF   PERMEABLE
storm events.83                                   PAVEMENT
Porous pavement and alternative pavers            In the past, studies indicated that permeable
alone are not an appropriate BMP to combat        pavement applications had a high failure
extreme flooding events in channels and            rate, due not only to improper siting, but
riverbanks. It is recommended that a BMP de­      also poor maintenance. Failure of a perme­
signed specifically to control high waterflows,     able paving system means that the surface
such as a dry detention pond, should be used      becomes impervious and behaves like con­
in conjunction with porous pavement. This         ventional asphalt, yet typically without the
approach is required by some local govern­        fully developed system of piping and gutters
ments as part of flood protection design           used to manage runoff on conventional park­
criteria.84                                       ing surfaces. However, with correct mainte­
                                                  nance, permeable pavement can retain its
Permeable pavement should not be used             permeability, and be a successful stormwater
in parking lot areas with high volumes of         management option.89
sediment-laden runoff, high traffic volume,
high dust areas, and/or heavy equipment           The level of maintenance necessary to
traffic.85 Clogging is the main cause of a          maintain permeable pavement lots varies.
system malfunction that can result from poor      Alternative pavers such as concrete grid pav­
siting of the permeable pavement system.          ers and plastic modular blocks will require
During construction, developers can prepare       less maintenance because they do not clog
for possible clogging by installing a perim­      as easily as porous asphalt and permeable
eter trench connected to the stone reservoir      concrete. Location also impacts the amount
to treat overflow should the surface clog.86       of maintenance, as areas receiving more
Other common problems to avoid include:           sediment will require more maintenance. For
                                                  example, a parking lot with higher traffic vol­
• 	 Compaction of underlying soil, such as        umes will tend to require more maintenance
    through the use of heavy equipment.           because of the resulting increased quantities
• 	 Contamination of stone sub-base with          of soil and particulates brought onto the lot.
    sediment.                                     Although the new soil alone will not neces­
                                                  sarily clog the pavement’s voids, if ground in
• 	 Tracking of sediment onto pavement.87         repeatedly by tires, clogging can occur.90,91
Like other best management practices, when        Regular maintenance can avoid clogging of
permeable paving systems fail, it is frequently   permeable paving systems. Facilities manag­
due to mistakes made during the design and        ers are generally advised to high pressure
construction process. Recent studies note         hose and then vacuum porous pavement a

                                 Green Parking Lot Resource Guide—February 2008                     25
minimum of two to four times a year, de-                      may lead to contamination of the ground-
pending on the system. This should remove                     water. This includes prohibiting construction
any dislodged sediment and particulate                        vehicles or hazardous material carriers from
matter from the site.92 Exhibit 4 provides an                 using the lot.95 Finally, because these types of
example of typical permeable pavement                         parking lots have unique maintenance needs,
maintenance activities.                                       land owners must ensure that individuals

                          Maintenance Activity                                                 Scheduling
 Ensure paved area is clear of sediments                                                As needed
 Mow upland and adjacent areas, and seed bare areas                                     Monthly
 Ensure paved area is clear of debris                                                   Monthly
                                                                                        Monthly and after
 Monitor that paved area dewaters between storms
                                                                                        storms >0.5 inches
 Vacuum sweep routinely to keep surface free of sediments                               3 to 4 times a year
 Clean inlets draining to the subsurface bed                                            Biannually
 Inspect the paved surface for deterioration                                            Annually
 Source: Adapted from New York State Department of Environmental Conservation, (2007), New York State Stormwater Design
 Manual—Chapter 9, :

Clogging can also be avoided through
                                                              responsible for parking lot maintenance, such
monitoring activities on and around the lot,
                                                              as the facilities manager, are properly trained
                                                              and prepared to handle the lot’s maintenance
• 	 Never using sand or gravel to address                     needs.
    icy conditions on porous pavements,
    although salt may be used on porous                       Cold Climate Considerations
    asphalt, and commercial deicers may be                    In cold weather regions, specific activities
    used on porous concrete.93                                are necessary to properly maintain a perme­
• 	 Ensuring that the surface is not sealed or                able pavement parking lot. The underlying
    repaved with a non-porous material.                       stone bed of permeable paving systems often
                                                              absorbs and retains heat, causing faster snow
• 	 Maintaining planted areas adjacent to                     melt which leads to less snow accumulation.
    porous pavement to prevent soil washout                   However, snow may still accumulate, espe­
    onto the pavement.94                                      cially during heavier storms. When treating
Signs should also be posted around the lot to                 it, abrasive materials such as sand should not
prevent harmful activities such as resurfacing,               be used on or near the pavement, as it will
the use of abrasives, and any activities that                 quickly clog the surface. As noted above, salt

                                         CHAPTER 5—Alternative Parking Surface Materials                                  26
can be used as a deicer on the porous pave­       INFILTRATION & POLLUTANT
ment, though nontoxic, organic deicers are        REMOVAL EFFECTIVENESS OF
preferable because the chlorides in salt can      PERMEABLE PAVEMENTS
migrate into the groundwater.96 With porous
pavement, some sites have found that light        Permeable paving coupled with a subsurface
plowing reduces the need for salt, as the         storage bed can capture and manage storm-
remaining snow quickly drains into the mate­      water from small, frequent rainfall events,
rial.97 When plowing snow, operators should       which accounts for between 30 and 50
set the blade slightly higher than usual (i.e.,   percent of annual precipitation on average.102
one inch), as to not damage the material. This    In addition, this combination can be very ef­
will avoid the blade catching the edge of a       fective at removing stormwater pollutants.
block or paving and damaging its surface.
                                                  Infiltration Effectiveness
Signs should be posted to reinforce plowing
requirements.98 Finally, frost heave can occur    Permeable pavement, when properly de­
if infiltrating runoff freezes below the surface,   signed and maintained, can eliminate almost
however porous pavement can be designed           all surface runoff from low intensity storms.103
to avoid this issue.99                            As mentioned before, proper siting and
                                                  maintenance of permeable parking areas are
Repairs                                           critical to maintaining high surface infiltra­
According to Cahill Associates, a leading         tion rates.104 Data on infiltration rates vary
sustainable stormwater management design          widely according to design characteristics
firm, potholes in porous pavement are very         and underlying soils, however, research indi­
rare. However, settling might occur if any soft   cates that an average of 50 percent of annual
spots in the subgrade are not addressed dur­      rainfall on porous pavement infiltrates, with
ing construction. Even after 20 years, a well-    reported infiltration rates reaching as high as
maintained porous surface can show little if      80 percent.105 Infiltration rates can decline to
any cracking or potholes.100 Many alternatives    a certain extent over time, again depending
are available for repairing damaged porous        on design, installation, maintenance, and site
pavement and alternative pavers. In general,      characteristics such as sediment loads.106
areas less than 50 square feet can be patched
                                                  Pollutant Removal Effectiveness
by using either a porous mix or standard
pavement because the loss of porosity to          Limited data indicate that permeable pave­
a small spot is insignificant to the overall       ment systems have high removal rates for
stormwater management function. If an area        many pollutants, including total suspended
greater than 50 square feet is damaged, an        solids, metals, oils, and grease.107 However,
engineer should be consulted to design an         pollutant removal is not effective for larger
appropriate patch.101                             storms with rainfall greater than one-inch, or
                                                  with high rainfall intensity.108

                                Green Parking Lot Resource Guide—February 2008                      27
Porous Pavement                                               lower. Also, motor oil was detected in 89 per­
Studies of porous pavement performance                        cent of the runoff samples from conventional
show that they can effectively trap soluble                    asphalt, while no motor oil was detected in
pollutants, which are then absorbed or                        any samples that infiltrated through sections
broken down in the underlying soil layers. Ex­                of alternative pavers.111
hibit 5 depicts the range of pollutant removal
                                                              Another study researched driveways con­
effectiveness for porous pavement, showing
                                                              structed of conventional asphalt versus
a removal effectiveness of at least 65 percent
                                                              permeable pavers to compare their runoff
for suspended solids, nitrogen, pathogens,
                                                              depths, infiltration rates, and pollutant con­
and metals; and at least 30 percent of phos­
                                                              centrations over two years. The study found
                                                              that the mean weekly runoff rate for conven-

                                               Typical Pollutant Removal (percentage)
         BMP Type                     Suspended
                                                        Nitrogen         Phosphorus          Pathogens         Metals

 Porous Pavement                        65-100          65-100             30-65             65-100           65-100

 Source: U.S. EPA, 1993, Handbook Urban Runoff and Pollution Prevention Planning, EPA-625-R-93-004, taken from Purdue Uni­
 versity Engineering Department’s Long-Term Hydrologic Impact Assessment (L-THIA):

Alternative Pavers
Alternative paver systems have been shown                     tional asphalt was over three times that of
to be just as effective as porous pavement                     the permeable pavers. In addition, they found
in removing pollutants. A study from the                      that pollutant concentrations in runoff from
University of Washington conducted to                         the permeable pavers were substantially less
determine the long-term effectiveness of                       than from the conventional asphalt, as shown
permeable pavements as a stormwater                           in Exhibit 6.112
management strategy showed significant                         As with other stormwater infiltration BMPs,
pollutant removal rates. Researchers com­                     developers must take measures to mitigate
pared the effectiveness of four permeable                      any possible groundwater contamination at
pavement types and conventional asphalt                       a permeable pavement site. Permeable pav­
over six-years.110 They found that runoff from                 ing should not be used to treat stormwater
the conventional asphalt had significantly                     “hotspots,” areas where land uses or activities
higher concentrations of measured pollutants                  have the potential to generate highly con­
(i.e. motor oil, copper, zinc) compared to the                taminated runoff. These areas include: com­
alternative paver surfaces. Concentrations of                 mercial nurseries, auto recycling and repair
copper in runoff from alternative pavers were                  facilities, vehicle service and maintenance
roughly 80 percent lower than those found                     areas, fueling stations, high-use commercial
in the runoff from conventional asphalt, and                   parking lots, and marinas.113
zinc concentrations were at least 40 percent

                                         CHAPTER 5—Alternative Parking Surface Materials                                    28
EXHIBIT 6: STUDY EXAMPLE: STORMWATER RUNOFF COMPARISON                                                        IN
                                            Conventional Asphalt                     Permeable Pavement
                                                  (mg/l)                                   (mg/l)
 TSS                                                       47.8                                    15.8
 NO2-N                                                     0.6

 NH3-N                                                     0.18

 TP                                                       0.244

 Cu                                                         18

 Pb                                                         6

 Zn                                                         87

 Source: Hinman, C., (2005), Low Impact Development Technical Guidance Manual for Puget Sound, Puget Sound Action Team,
 publication number PSAT 05-03:

COST CONSIDERATIONS                                           percent more than conventional asphalt pav­
                                                              ing.114 Finally, Cahill Associates maintains that
The costs for permeable pavement systems                      the cost of a porous pavement installation is
vary depending on site specifications and the                  roughly the same as the cost of a convention-
type of system being used. In general, the                    al asphalt parking lot.115 The costs for alterna­
cost to install alternative pavers or porous                  tive pavers are more difficult to estimate, as
pavements alone are higher than conven­                       they fluctuate widely depending on type and
tional asphalt paving, which costs between                    manufacturer.116 In general, larger parking
$0.50 to $1.00 per square-foot. Sources dis-                  lots utilizing alternative pavers will incur a
agree on the average initial costs for perme­                 lower overall unit cost per space.
able pavement. Exhibit 7 provides an initial
cost comparison of pavement options from                      The overall cost-effectiveness of perme­
the NY State Stormwater Design Manual.                        able pavement can only be fully assessed by
However, another source notes that porous                     considering its typical use in concert with
asphalt, with additives, costs from 10 to 20                  other stormwater BMPs. Specifically, the cost-
                Pavement Type                                           Cost per Ft2 (Installed)
 Conventional Asphalt                                                           $0.50 to $1.00
 Permeable Concrete                                                             $1.50 to $5.75
 Grass/Gravel Pavers                                                            $2.00 to $6.50
 Interlocking Concrete Blocks                                                   $5.00 to $10.00

 Source adapted from New York State, New York State Stormwater Design Manual:

                                        Green Parking Lot Resource Guide—February 2008                                    29
competitive nature of permeable pavement          the need for land-intensive BMPs such as dry
systems lies in their success when combined       extended detention or wet retention ponds.
with other BMPs or subsurface drainage            This fact produces additional cost advantages
to create a well-designed and sustainable         for permeable pavement over conventional
stormwater management system. Prop­               asphalt in locations with high land prices.118
erly designing and installing such a system
                                                  Maintenance costs should also be factored in
requires a high level of labor and expertise,
                                                  when considering the costs of a permeable
as well as material costs, including excavation
                                                  paving system. If not designed and main­
for deep underlying stone bed and the use of
                                                  tained properly, porous pavement’s effective
geotextile fabric. However, these higher ini­
                                                  lifespan may be shortened due to potentially
tial costs are offset by reductions in the need
                                                  high risks of clogging.119 Some studies sug­
for expensive traditional “hard” stormwater
                                                  gest that the cost of vacuum sweeping on a
management of pipes, gutters, and drains
                                                  new permeable lot may be considerable if the
relative to parking lots made of conventional
                                                  landowner does not already perform vacuum
asphalt pavement. When these savings are
                                                  sweeping operations. However, one study
incorporated, overall project costs are often
                                                  estimates the annual maintenance cost for a
reduced.117 Also, when used in combination
                                                  porous pavement parking lot at $200 per acre
with other smaller techniques, such as biore­
                                                  annually, which includes regular inspections,
tention cells, vegetated swales, or vegetated
                                                  as well as jet hosing and vacuum sweeping.120
filter strips, permeable pavement reduces

                                 CHAPTER 5—Alternative Parking Surface Materials                   30

In 2006, Heifer International, a non-profit sus­
tainable community development organiza­
tion located in Little Rock, Arkansas, designed
an environmentally-friendly parking plaza to
complement their new green building head­
quarters. A first of its kind in Arkansas, this
project serves as a model for other organiza­
tions considering a green parking lot. Heifer’s
parking plaza encompasses numerous green
parking lot techniques including the use of
more sustainable materials to minimize im­
pervious surface, reduce runoff, reduce virgin
                                                  Heifer International’s World Headquarters: a green building with a green
water use, and incorporate recycled content.      parking lot.

Heifer evaluated a variety of paving options      • Gravel Pave system—Used for the park­
when selecting materials for their green            ing stalls, thirty thousand square feet of
parking lot. Unlike a conventional lot, which       Heifer’s parking plaza are covered by a
most likely would be constructed primarily          gravel pave system. The stalls are construct-
of asphalt, Heifer chose three types of paving      ed using 100 percent recycled material
materials that provide environmental ben­           (90 percent post-industrial and 10 percent
efits over asphalt.                                  post-consumer). At a unit cost of $4.75 per
                                                    square foot, this gravel pave portion of the
• Concrete—The high traffic aisles and                lot cost a total of $142,500. Maintenance
  driveway of the Heifer lot are paved with         is minimal, requiring roughly eight hours a
  concrete rather than asphalt. Overall, it         month at a cost of $160 per month.
  covers an 86,000 square-foot area, at a
  cost of $5.75 per square foot, or $494,500.     • Brick pavers—Recycled brick pavers
  The concrete base contains 90 percent             were used to form a decorative driveway
  recycled cement and its top layer is made         centerpiece, and cover the smallest part of
  of locally produced concrete.121 Because it       the lot (2,500 ft2) at a total cost of $34,418.
  is a light colored and highly reflective sur-      Heifer minimized the cost for the pav­
  face, concrete helps minimize heat island         ers by reusing bricks from buildings that
  effect (HIE) at the Heifer site. Coupled with      previously occupied the site. Heifer em-
  the extreme humidity in the Little Rock           ployees also volunteered to help clean a
  region where Heifer is located, this HIE can      number of the bricks so they could be re-
  be stifling. However the use of concrete           used. The total cost for the pavers includes
  for paving has been shown to produce a            additional labor, beyond the volunteer
  20ºF reduction in surface temperatures            hours, to clean bricks and construct the
  compared to asphalt.122                           centerpiece. Heifer has yet to incur any
                                                    maintenance costs for this area.
                                Green Parking Lot Resource Guide—February 2008                                               31
All of the parking lot materials used in the        net increase in emissions or resource use. For
Heifer lot were purchased from local deal­          instance, Heifer’s green parking lot used more
ers within 500 miles of the site, supporting        water than an asphalt parking lot would have
the local economy and reducing emissions            because of the greater water inputs required
associated with transportation of purchased         in the recycling of concrete pavement com­
materials.                                          pared to the production of asphalt pavement.

UPSTREAM BENEFITS                                   By applying estimates of the economic value
                                                    of reduced human health and ecological
Upstream environmental benefits were real­           impacts from avoiding emissions, these
ized through Heifer’s use of recycled concrete      upstream benefits were then monetized.
and other recycled materials, instead of using      Reliable estimates of economic value are not
virgin asphalt, in the construction of their lot.   available for carbon dioxide (CO2) emissions.
These benefits include reduced air emissions         However, by applying estimates for the value
(associated with the production of asphalt),        of reducing sulfur dioxide (SO2) and particu­
reduced transportation emissions (from pur-         late matter (PM10) emissions, a range of mon-

     Energy            Water Use                                  Tons
                                                                                    Hazardous Waste
    (MMBtu)            (gallons)           CO2       NOX      PM10       SO2

       668.3               -116           20.9      -0.89     0.72       25.3             20.7

chasing locally produced materials), reduced        etary values related to Heifer’s reductions can
energy use, and reduced hazardous waste             be shown (see Exhibit 9).125
generation related to the production of virgin
materials.                                          Heifer’s goal in building its parking plaza
                                                    was to minimize impacts to the environment
Modeling was used to estimate any upstream          while handling a large volume of site traffic.
benefits from the construction of Heifer’s
lot.123 The resulting analysis (see Exhibit 8)      A more detailed case study of Heifer Inter­
shows a clear overall positive net benefit           national’s green parking lot can be found
from the construction of Heifer’s lot, although     on the U.S. EPA’s Web site at
results for some individual metrics indicate a      earth1r6/6sf/bfpages/bfheifer.html.

                                              Monetized Upstream Benefit
     Air Emission
                                            Low                                  High

            SO2                           $43,044                              $455,760
           PM10                           $7,170                                $71,700

                                   CHAPTER 5—Alternative Parking Surface Materials                    32

              In 2002 and 2003, the University of Rhode
              (URI) constructed two parking lots at their
              Kingston, Rhode Island campus to meet
              parking demands from new University
              development and commuting students. The
              parking lots were located within the town’s
              groundwater protection overlay district, the
              University’s wellhead protection area, and
              also within the Pawcatuck sole source aquifer.
              These lots would increase parking capacity
              by 1,000 spaces, spread over seven acres of
              land (see areas highlighted in red in Photo 1).                  Rainwater infiltrates the porous asphalt (left), but accumulates on adjacent
                                                                               road paved with conventional material (right).
              However, because the lots were located in an
              ecologically sensitive area already covered by                   In addition, project managers were also
              an estimated thirty percent impervious sur­                      interested in avoiding any potential impacts
              face, the University desired an environmen­                      to groundwater supplies.127 The University
              tally protective option than would combat                        determined that a permeable asphalt surface
              stormwater issues more effectively than con­                      would help control runoff quantities as well
              ventional paving surfaces. The University’s                      as potentially limit pollutants entering sur­
              main stormwater concern was to decrease                          face and groundwater supplies.
              runoff quantities to protect a nearby stream
                                                                               In addition to using permeable asphalt,
              considered impaired due to low water flows.
                                                                               landscaped islands were designed as biofil­
                                                                               tration areas to provide a secondary route
                                                                               of infiltration during large storm events or
                                                                               pavement clogging. Also, the University took
                                                                               precautions to avoid clogging the permeable
                                                                               pavement by planting trees and grass around
                                                                               the parking lot perimeter, which limits wind­
                                                                               blown dust from nearby agricultural areas
                                                                               and controls soil erosion. An emergency spill­
                                                                               way was also constructed to direct overflow
                                                                               to recharge beds in the extremely unlikely
                                                                               event that the permeable asphalt and biofil­
                                                                               tration areas both clog.

URI’s permeable parking lots - The two original permeable asphalt parking
lots built in 2002 and 2003 are outlined in red. The 2005 parking lot exten­
sion is outlined in green.

                                                          Green Parking Lot Resource Guide—February 2008                                                     33
COST CONSIDERATIONS                                   meable asphalt layer was not infiltrating
                                                      properly because the binder had become
The total construction costs for the two park­
                                                      separated from the asphalt. Project
ing lots was just over $3 million, or $3,000 per
                                                      consultants recommended an improved
parking space, which is considered compara­
                                                      polymer mixture, new to the market, that
ble to conventional parking lots of equal size.
                                                      would prevent the separation and elimi­
Costs included site preparation, barn demoli­
                                                      nate the infiltration problem.
tion, materials, lighting, drainage, landscap­
ing, monitoring wells, post-construction in­       • Pollutant removal
spections, and design fees that were roughly
                                                      The University is currently monitoring the
ten percent of the total cost. URI’s costs
                                                      pollutant removal and runoff level from
included non-typical items such as removal
                                                      the lots. They found a 90 percent retention
of stone masonry walls, and installation of
                                                      of zinc and copper. However, the perme­
security cameras and emergency telephones.
                                                      able asphalt was not as effective in captur­
Without these additions, installation would
                                                      ing other pollutants, including organic
have been cheaper. On average, installation
                                                      pollutant such as PAHs, and inorganic
runs between $2,200 and $2,750 for porous
                                                      pollutant such as nitrate and phosphate.
pavements such as permeable asphalt.
                                                      This is due to clogging, as well as the type
                                                      of geotextile fabric used in the project,
                                                      which was found to prevent an even flow
In the few year since they constructed the            of water into the subsurface.
two permeable asphalt parking lots, URI has
                                                   In the summer of 2005, the larger of the two
been monitoring their success in managing
                                                   permeable asphalt parking lots was expand­
and filtering stormwater. As a new technolo­
                                                   ed by another 800 spaces. When planning
gy, they noted several areas for improvement.
                                                   this expansion, the University was able to
• Clogging                                         incorporate improvements to their design
                                                   based on lessons learned from the original
   Overall, these parking lots were successful
                                                   two parking lots. Design changes included
   from a hydrological perspective. However,
                                                   use of the polymer mixture to prevent sepa­
   some clogging was observed in the higher
                                                   ration of the binder, fewer and wider biofiltra­
   traffic areas of the lot. Clogging also
                                                   tion islands, and curb cuts for water entry to
   occurred in one corner of the lot where
                                                   the biofiltration islands. Maintenance issues
   plowed snow was stockpiled during the
                                                   regarding snow removal were also addressed.
   winter, which reduced infiltration due to
   sediment build-up. This is an indication        Further information on the University of
   that plow blades were not raised to the         Rhode Island’s permeable asphalt parking
   required height, an issue that also caused      lots can be found at
   surface defects to the lot.                     NEMO/Publications.
   Excavation of the lot during construction
   of a sidewalk also revealed that the per-

                                  CHAPTER 5—Alternative Parking Surface Materials                    34

     n the majority of parking lots across       • 	 Reduce damage from stormwater, and
     the country, landscaping does not vary
                                                 • 	 Improve habitat and increase
     according to geographic location. It is
typically designed using conventional turf
grass, such as Kentucky Bluegrass, and com­      This chapter provides an overview of natural
mon popular ornamental plantings. However,       landscaping and irrigation techniques suitable
because these plants are often not native        for green parking lots. It describes the differ­
to areas where they are being used, regu­        ence in irrigation and maintenance require­
lar maintenance is required to keep them         ments for natural landscaping compared to
healthy. Sustaining this greenery requires       conventional landscaping, the benefits of
irrigation systems and potable water use to      natural landscaping, and cost considerations.
supplement rainfall, chemical applications of
pesticides and fertilizers, and ongoing lawn     OVERVIEW OF NATURAL
maintenance (e.g., mowing).128 Irrigation and    LANDSCAPING AND IRRIGATION
chemical use contribute to degradation of
                                                 Natural Landscaping
water quality and aquatic habitat in receiving
                                                 Considerations and Vegetation
waters, decreased water supplies, increased
stormwater runoff, declining biodiversity, and
air pollution. Mowing and other maintenance      Natural landscape design, sometimes
activities are a significant air pollution con­   referred to as native or sustainable landscap­
cern; for example, in one hour a lawn mower      ing, uses plant species indigenous to a region
emits as much pollution as a car driving 350     pre-European settlement. Because these
miles.129 With proper planning, landowners       native plant species have evolved in the local
can avoid these impacts by utilizing “natural    environment, maintaining them is relatively
landscaping” approaches.                         easy—they are more resistant to local pests,
                                                 they are better suited to survive on natural
Natural landscaping involves creating a low-
                                                 rainfall, and they are adapted to live in local
maintenance landscape in and around a park­
                                                 soil types. These heartier plants also provide
ing lot using native plants and water-efficient
                                                 habitat for local native wildlife species that
irrigation techniques. A vital component of
                                                 they co-evolved with—a symbiotic relation­
green parking lots, natural landscaping can:
                                                 ship that is the foundation for our native
• 	 Reduce landscape installation and main­      ecosystems and biodiversity.131
    tenance costs,
                                                 A feasible and intelligent approach for most
• 	 Limit harmful chemical pollution (i.e.       development sites, natural landscaping also
    pesticides, fertilizers),                    supports sustainable development strategies
                                                 such as Low Impact Development (LID) and
• 	 Reduce potable water use and pollutant
                                                 Smart Growth, and is a vital component to
    air emissions,
                                 Green Parking Lot Resource Guide—February 2008                    35
many stormwater Best Management Practic­             amount of turf to only those areas necessary
es (BMPs). For example, some of the bioreten­        for practical purposes.
tion approaches described in Chapter 4, such
as vegetated swales and rain gardens, are            Irrigation Requirements for
based on natural systems and intended to             Natural Landscaping
function as they would have in absence of de­        As mentioned above, a key difference be­
velopment.132 BMPs rely on native plants for         tween conventional and natural landscaping
added efficiency in retention, infiltration and         is water use requirements. Conventional land­
transpiration, and cleansing.133 See Chapter 4       scaping consumes large quantities of water
for more information on BMPs.                        to sustain non-native species, which typically
Developers must take a number of factors             cannot withstand local conditions as well as
into consideration when planning and de­             native varieties. For instance, the popular turf
signing natural landscaping. Natural land­           species Kentucky Bluegrass typically requires
scaping involves more than new plantings of          in excess of 40 inches a year of precipitation
native species; an important step to consider        to thrive.136 This is above annual rainfall levels
before construction even begins is retaining         for many states, particularly in Western parts
as much of the existing native landscaping as        of the country. According to the U.S. Depart­
possible at a site. By preserving existing vege­     ment of Energy, native and other climate
tation, developers can minimize the need for         appropriate landscaping can reduce irriga­
new landscaping, and limit site disturbance.         tion water use by at least 50 percent.137 This
If the location of existing vegetation is not        was the case for Heifer International’s green
suitable, it is preferable to relocate it on-site    parking lot (see case study at the end of the
rather than dispose of it during construction.       chapter), where the landscaping requires no
Another option is to remove native plants            additional irrigation under normal conditions.
from sites scheduled for construction; some          Typically, native plants require irrigation only
volunteer organizations will retrieve plants         when they first take root.138
from construction sites to later replant at          In most cases the water source for conven­
other locations.134                                  tional irrigation is the same potable drinking
Landscaping choices should be compatible             water used inside buildings, applied gener­
with individual site characteristics including       ously by inefficient spray irrigation systems.
topography, soil, drainage patterns, and sun         In many developments, these irrigation
exposure.135 It is important to select site-         systems are programmed to turn on auto­
appropriate plants when bringing native              matically, and do not take fluctuating rainfall
landscaping in from off-site; as such, consult­       amounts or soil moisture into account. In
ing a local landscape designer with native           contrast, natural landscaping fosters smarter
plant knowledge is recommended.                      irrigation practices, through water-efficient
                                                     planting, mulching, rainwater harvesting, and
Although native landscaping is feasible for          water-efficient irrigation technology.
most sites, in cases where it is not feasible or
is otherwise not utilized, developers should         Efficient Irrigation Technology139
choose low-water use plants and limit the
                                                     Efficient irrigation technology is essential to

                                                   CHAPTER 6—Landscaping and Irrigation                   36
conserving water, and a number of options          properly schedule sprinkler use; and zoning
are available to help landowners save money        systems that focus on the water needs of
through less wasteful practices. A fundamental     each plant grouping.143
problem of conventional irrigation is over-
watering. Not only does over-watering reduce       Efficient Irrigation Procedures
water supplies and increase runoff amounts,         The basic practices of landscaping, including
but it also can result in plant diseases such as   plant layout and irrigation scheduling, are
fungus, and in the excessive growth of weeds       also vital to natural landscaping.
and pests. Over-watering also results in weak
plant growth that in turn precipitates the need      	
                                                   • Seasonal influences—When scheduling
for additional maintenance.140                       irrigation, it is important to understand
                                                     the seasonal variations and changing
If landscaping is watered at a less frequent         weather conditions. In some regions of
and more appropriate rate, plants will               the country, water requirements can vary
develop deeper roots and become healthier            considerably depending on the season.
overall.141 Recommended alternatives to the
traditional sprinkler method, which often          • 	 Time of day—It is also important to
over-waters landscaping, include soaker                consider the time of day when irrigation
hose, drip, or subsurface irrigation.                  is taking place. Watering is more effective
                                                       during early morning hours or early in
Drip irrigation in particular is a water conser­       the evening, when temperature and wind
vation technology that is gaining popularity.          speeds are typically lower, thus reducing
Used in the past to conserve water in arid             evaporation water loss.144
areas, its use has expanded with heightened
awareness of resource conservation and               	
                                                   • Weather conditions—Weather condi­
environmental sustainability. Drip irrigation        tions and weather forecasts should be
is a system of tubing with small holes that          incorporated into irrigation planning. Use
allows water to drip out onto the root zone of       system override devices when it is raining,
plants, providing more targeted and uniform          and try to program irrigation to avoid days
irrigation. Such systems can run on recycled         when rain is forecast. In addition, watering
water, and can be an option for temporary            on windy days means that the water may
use to establish native plants. Should a sprin­      not reach targeted areas or may be blown
kler system be selected, low-flow sprinkler           onto paved areas.
systems that release water slowly and close        Mulching helps keep moisture in the soil and
to the ground are preferable to sprinklers         allows rainfall and irrigation water to better
that emit mist, which easily evaporates.142        penetrate the root system. Landscapers rec­
Other examples of efficient irrigation tech­         ommend that roughly three inches of organic
nology include soil tensiometers, which de­        mulch be applied over trees and shrubs roots,
termine when the soil is dry and gauge water       and in plant beds. This also helps moderate
needs; rain or moisture sensors that can shut      soil temperature, minimize evaporation, and
off automated irrigation systems during rain;       reduce erosion and weeds. In addition, when
irrigation timers with manual overrides to         mulch decomposes, it increases the organic

                                 Green Parking Lot Resource Guide—February 2008                     37
content of the soil.145 Lastly, the layout of       are established. The primary environmental
natural landscaping is important to efficient         benefits of incorporating natural landscaping
irrigation. By grouping plants with similar wa­     into parking lots are described below.
ter needs together, a dedicated irrigation line
or valve can be used to apply the appropriate       Decreased Non-Point Source
amount of water at the correct frequency.146        Pollution
                                                    The U.S. EPA’s 2004 Conference on Landscap­
Rainwater Harvesting and
                                                    ing with Native Plants found that landscaping
Recycled Water147
                                                    with native plants may help reduce non-point
To conserve water, natural landscaping also         source pollution reduction in the following
includes the use of collected rainwater or          ways:
recycled wastewater for irrigation. These are
                                                    • 	 The need for fertilizers and pesticides to
both preferred alternatives to using potable
                                                        maintain conventional landscapes (i.e. turf
water, which is a finite natural resource.
                                                        grass) can often be eliminated with native
Moreover, potable water treatment man­
agement requires energy use for desalting,
pumping, pressurizing, groundwater extrac­          • 	 Through direct uptake of nutrients, native
tion, conveyance, and treatment.148                     plants may reduce the impact of fertilizer
                                                        elements (i.e. nitrogen and phosphorous)
Reuse of rainwater is a good option because it
                                                        that would otherwise contaminate water
is “not chlorinated and is mildly acidic, which
                                                        sources.152 Fertilizer contributes to ap­
helps plants take up important minerals.”149
                                                        proximately 80 percent of nutrient loads
Containers, such as cisterns or rain barrels, can
                                                        in the springtime.153
be used to collect and store water from roof
catchment areas. Rainwater can also be har­         • 	 Native plants may create sub-soil condi­
vested from an underground storage system,              tions that help reduce levels of nitrate
which is then pumped to the irrigation system.          entering water supplies via facilitation.154
In addition to rainwater harvesting, certain
                                                    • 	 Native plants are capable of filtering other
types of non-potable water, if treated properly,
                                                        impurities from stormwater runoff, such as
can be used as well for irrigation. For instance,
                                                        salt and automobile deposits (i.e., oil).
water recycled from wastewater, also known
as irrigation quality or reclaimed water, can be    The over-application of fertilizers and
treated and, although not suitable for drinking,    pesticides can lead to other detrimental
is very useful for irrigation.                      environmental impacts beyond non-point
                                                    source pollution. Less than 10 percent of
ENVIRONMENTAL BENEFITS OF                           insects actually harm plants, yet inappropri­
USING NATURAL LANDSCAPING                  AND      ate pesticide use harms non-target insects
ASSOCIATED IRRIGATION                               that are beneficial to the environment, it can
Compared to conventional landscaping de­            also harm wildlife.155 Overuse of fertilizers can
sign, natural landscaping can offer substan­         exacerbate insect diseases as well as promote
tial environmental benefits by minimizing ir­        unnecessary plant growth, which in turn
rigation and maintenance needs once plants          increases maintenance needs.156

                                                CHAPTER 6—Landscaping and Irrigation                    38
An innovative natural landscaping approach        industrial developments. Xeriscaping is a
to pest management, called “integrated pest       collection of sustainable landscaping design
management,” is a low chemical approach           principles incorporating the use of native
to landscape maintenance. Rather than             or other water efficient plants.160 Another
emphasizing the use of harsh chemicals, it        example is Las Vegas, Nevada, where a city
incorporates materials composed of natu­          ordinance limits the amount of turf on new
rally occurring compounds, and promotes           landscapes to no more than 50 percent.161
natural landscaping design and maintenance
practices. According to the U.S. Department       Reduced Air Pollution
of Energy, integrated past management             Reduced maintenance from native landscap­
“demonstrably creates a better environment        ing can improve air quality:
for plants as time passes.”157
                                                  • 	 Locally, through reduced smog and air
Water Conservation                                    toxics;

Water conservation is one of the primary          • 	 Regionally, through the reduction of acid
benefits of a natural landscaping approach.            rain caused by nitrogen oxide (NOX) and
Using native plants in landscaping helps con­         sulfur dioxide (SO2) emissions; and
serve water because once established, native
                                                  • 	 Globally, by combating greenhouse gas
plants often do not need supplemental wa­
tering beyond local rainfall amounts.158 This
is not the case for conventional landscaping      It is estimated that for every 10 days of
where, for instance, the watering schedule        maintenance required for a traditional turf
for turf landscaping is estimated at 1 inch of    landscape area, a natural designed area only
water over the entire area, for 30 applications   requires one day.163 This greatly minimizes
per year.159 The water conservation ben­          the need to run maintenance equipment
efits become even greater when harvested           such as lawn mowers, leaf blowers, and weed
rainwater or recycled wastewater are used for     wackers, which typically run on gasoline and
irrigation rather than potable water.             emit carbon dioxide (CO2) and other air pol­
                                                  lutants. For example, the use of lawn equip­
With water shortages seen in many commu­
                                                  ment in just the Chicago region produces 50
nities throughout the country, native land­
                                                  tons of volatile organic compounds (VOCs)
scaping is a sensible approach to preserving
                                                  every day in the summertime.164
water. Local governments in states such as
North Carolina, Texas, and California have        Reduced Erosion and
adopted natural landscaping ordinances,           Sedimentation
innovative rate structures, and wastewater
reuse plans to address water shortages. For       Natural landscaping in parking lots also helps
example, Santa Monica, California requires        minimize the erosion and sedimentation
the use of a particular water-efficient land­       impacts of development. The deep root sys­
scaping strategy called “xeriscaping” for all     tems of native plants stabilize soils and help
landscapes installed in new commercial and        prevent wind and water erosion along deten-

                                 Green Parking Lot Resource Guide—February 2008                    39
tion basin edges and streambanks.165 This is            the variety of life. Defined as “the variability
particularly true of plants that were on-site           among living organisms from all sources in­
pre-construction and preserved. Native plant­           cluding…terrestrial, marine and other aquat­
ings can also help remove sediments from                ic ecosystems, and the ecological complexes
runoff through filtration, again helping to               of which they are part,” biodiversity is the
preserve water quality and aquatic habitat.166          diversity within species, between species and
                                                        of ecosystems.170 Conventional landscaping
Reduced Heat Island Effect                              can negatively affect biodiversity of species at
As discussed in Chapter 1, heat island effect            various levels when native plants species are
(HIE) occurs in urban areas when the com­               replaced with homogenous, exotic, ornamen­
bined effect of heat-absorbing surfaces, such            tal species. This “monoculture” limits genetic,
as asphalt, leads to higher air and surface             species, and ecosystem diversity.
temperatures. HIE can increase temperatures             The diversity of our flora and fauna is an in­
between 2 to 8ºF on average during the sum­             valuable resource from an environmental and
mer.167 The greatest temperature increases are          human health perspective. Ecosystems that
typically seen in areas with less vegetation            contain a diversity of native plant and animal
and high amounts of urban development.                  species better provide “ecosystem services”
Vegetation, especially trees, can help reduce           to humans, such as water and air purifica­
HIE, by providing shading to paved areas. For           tion.171 Native plants also support a healthier
example, a NASA study on the Madison Square             environment by providing food and shelter
Mall in Huntsville, Alabama found that the              for wildlife. In addition, some exotic plants
temperature in the middle of the parking lot            can become invasive species, smothering na­
on a summer day was 120ºF, while the temper­            tive plants or overrunning their habitat, again
ature at a small tree island in the parking lot         affecting the plant population and the chain
was only 89ºF. For every additional tree canopy         of species dependent upon it.
cover temperatures can often be reduced by
1º F. Vegetation can also indirectly cool parking       COST EFFECTIVENESS OF USING
areas though transpiration, and soil also cools         NATURAL LANDSCAPING
through water evaporation.168
                                                        A common perception is that natural land­
Because of its cooling capabilities, landscap­          scaping is more costly than conventional
ing also plays a role in reducing building              landscaping. However, cost/benefit modeling
energy use and associated CO2 air emissions.            and case studies have shown that natural
Hotter temperatures from HIE can lead to                landscaping can be more cost-effective in the
increased energy demand to cool buildings               long term—for both communities and land
located near heat absorbing surfaces such as            owners.172 Reduced costs result from de­
parking lots. By reducing HIE, it is estimated          creased energy use, forestalled infrastructure
that plantings close to buildings can reduce            upgrades, and lower land maintenance costs.
air conditioning costs by 5 to 20 percent.169           For example, one study found that landown­
                                                        ers can save between $270 and $640 dollars
Enhanced Biodiversity                                   per acre by preserving the native landscape
Biological diversity, or biodiversity, is literally     of their open land instead of creating a

                                                      CHAPTER 6—Landscaping and Irrigation                40
conventional, tuft-based, landscape. Savings                      sustainable landscaping versus conventional 

can also be realized during the installation                      landscaping.
of natural landscaping. It can be between
                                                                  By using a simple payback calculation, the
$4,400 and $8,850 less expensive per acre for
                                                                  above example demonstrates that the costs
the installation of natural landscaping than
                                                                  for the native landscaping are recovered
for turf grass.173
                                                                  within the first year because of significantly
Of all the potential sources of costs savings                     lower maintenance costs.174 As a general
from natural landscaping, reduced main­                           rule, annual maintenance costs for natural
tenance leads to the greatest savings. As                         landscaping are approximately 10 percent of
discussed throughout this chapter, natural                        conventional landscaping.175
landscaping requires less maintenance and
                                                                  Other economic benefits of natural landscap­
labor expenditures, such as less irrigation,
                                                                  ing include local government and commu­
mowing, weeding, and fertilizer/pesticide ap­
                                                                  nity cost-savings from avoided infrastructure
plication. Decreased irrigation is a major part
                                                                  and/or water supply upgrades associated
of these savings, as is seen in the case of Heifer
                                                                  with stormwater runoff, which can lead to
International (see following case study).
                                                                  flooding, pollution, groundwater recharge

(LANDSCAPE        AREA     = 8,000         SQUARE FEET)

                                        Site Design and                                        Total Maintenance
                                       Implementation                                                ($/year)
 Native Planting                                          $3,673                     $184                               $272
 Traditional Turf                                         $1,224                       $61                            $3,318
 Cost Difference (Native
                                                          $2,449                     $123                            -$3,046
 minus Traditional)
 Estimate of landscape area includes 1-acre (43,560 ft2) lot with 25,200 square foot parking area and 10,082 ft2 building
 footprint. For more information see U.S. Department of Energy, (2003), The Business Case for Sustainable Design in Federal
 Facilities—Appendix D,

An example of the overall maintenance sav-                        deficits, and damage to stream ecology.176
ings, including water savings, is presented in                    Reduced infrastructure burden is discussed
the following comparison produced by the                          in Chapter 7. In addition, communities often
U.S. Department of Energy. In this example,                       pay to eradicate algae blooms caused by ex-
costs are compared for a one-acre site (in-                       cess fertilizing, a cost avoided by widespread
cluding a 50 to 75 space parking area) using                      use of native landscaping.177

                                           Green Parking Lot Resource Guide—February 2008                                      41

In 2006, Heifer International, a non-profit sus­
tainable community development organiza­
tion located in Little Rock, Arkansas, designed
an environmentally-friendly parking plaza to
complement their new green building head­
quarters. A first of its kind in Arkansas, this
project serves as a model for other organiza­
tions considering utilizing green parking lot
techniques. One highlight is Heifer’s use of
native landscaping and irrigation methods,
which reduce potable water use and provide
habitat for local species.
                                                   By using native landscaping around its parking lot, Heifer International supports
The innovative landscaping and irrigation          the local ecosystem and conserves water.

surrounding Heifer International’s parking lot     thirds reduction in water demand compared
provides a variety of environmental benefits.       to a conventional parking lot scenario with
The grasses, plants, trees, and wildflowers         standard landscaping. By using recycled wa­
used throughout much of the site are indig­        ter, native plants, and water conserving irriga­
enous, and do not require pesticides. They         tion, Heifer is conserving 520,000 gallons of
also offer food and shelter to native wildlife,     potable water, and saving $65,343, annually.
and help create a more visually pleasing
aesthetic. Under natural rainfall events, the      Currently Heifer has six irrigation zones, four
species planted in the lot should be able to       that use drip irrigation and two that use con-
sustain themselves with little irrigation. In      ventional sprinkler irrigation.
fact, in a normal rainfall year, the landscape     • Drip Irrigation—Heifer has four drip-
will require irrigation only once a week.            zones for irrigating native trees and shrubs
Because Heifer used a combination of native          on the site. Each releases 0.9 gallons per
seeding and sod, their parking lot requires          hour, using a total of approximately 2,000
less irrigation than a conventional lot using        gallons of water per week. The total cost
all sod and non-native landscaping. In a typi­       for the drip irrigation system was $79,000.
cal, non-drought year, Heifer’s closed loop        • Sprinkler Irrigation—Heifer has two
stormwater system will provide 100 percent           spray-zones for irrigating the sod portions
of the water necessary to irrigate vegeta­           of the lot. These conventional pop-up
tion throughout the lot, eliminating use of          spray heads produce approximately 25
municipal water for this purpose. Heifer uses        gallons of water per minute per zone, us-
approximately 5,000 gallons of irrigation            ing a total of approximately 3,000 gallons
water per week, or 260,000 gallons annually,         of water per week. The total cost for the
to irrigate its grounds. According to their          sprinkler irrigation system was $42,000.
landscape architect, this represents a two-
                                                 CHAPTER 6—Landscaping and Irrigation                                            42
Heifer supported this sustainable landscap-      aesthetics of the parking lot, reduced heat 

ing by amending the soil with compost,           island effect, and supported wildlife habitat.
which helps increase nutrient retention,
                                                 For more information on Heifer Internation­
decrease irrigation needs, and improve soil
                                                 al’s green parking lot, including their sustain­
and plant health. They went beyond the City
                                                 able landscaping techniques, please vist the
of Little Rock’s parking ordinance by planting
                                                 U.S. EPA’s green building Web site at: www.
80 trees (63 more than the city requires) and
landscaped a far larger area within the lot
than required. These actions improved the

                                Green Parking Lot Resource Guide—February 2008                      43

         his resource guide has explored         • 	 The Environmental Council of States
         how components of a green park­             (ECOS)
         ing lot, including stormwater best
                                                    In 2007, ECOS’ Green Infrastructure
management practices, innovative planning
                                                    Resolution (07-10) encouraged the use
policies, and native landscaping, can be
                                                    of green infrastructure to mitigate sewer
used in combination to sustainably manage
                                                    overflows and protect public health and
stormwater at individual sites. The ultimate
                                                    the environment.179
potential of these practices, however, lies in
scaling them up to the neighborhood, town,       • 	 The U.S. Conference of Mayors
or regional level, to reduce burden on the
                                                    A 2006 Green Infrastructure Resolution
current stormwater management infrastruc­
                                                    from the U.S. Conference of Mayors recog­
ture, and plan for sustainable future growth.
                                                    nized that “green infrastructure naturally
This “green infrastructure” approach encom­
                                                    manages stormwater, reduces flooding
passes planning for parking lots, housing
                                                    risk and improves air and water quality,
developments, roads, and other stormwater
                                                    thus performing many of the same func­
related infrastructure. Defined by the EPA
                                                    tions as traditional building infrastructure,
as techniques that “utilize natural systems,
                                                    often at a fraction of the cost.”180
or engineered systems that mimic natural
landscapes, to capture, cleanse, and reduce      The need for scaling up green infrastructure
stormwater runoff using plants, soils, and        is pressing. It is estimated that nearly 25
microbes,” green infrastructure is an approach   million acres of impervious surface cover the
that is being endorsed by U.S. federal, state    continental United States, and that approxi­
and local government entities, including:        mately 70 million acres of land will be newly
                                                 developed in the United States by the year
•	 The U.S. Environmental Protection
                                                 2025. By 2030, 50 percent of the built envi­
   Agency (EPA) and national stakeholders
                                                 ronment will have been constructed since
   In 2007, EPA and four major national          2000.181 Such growth will increase strain on
   groups (National Association of Clean Wa­     existing municipal stormwater management
   ter Agencies, Natural Resources Defense       systems by adding more impervious surface
   Council, Low Impact Development Center,       area and higher volumes of runoff. In many
   and Association of State and Interstate       areas of the country, these systems are al­
   Water Pollution Control Administrators)       ready critically strained and are saddled with
   signed an agreement to promote the use        a backlog of deferred maintenance. A green
   of green infrastructure to reduce stormwa­    infrastructure approach can minimize runoff
   ter runoff and sewer overflows.178              volumes, and reduce the combined burden
                                                 on municipal stormwater and wastewater

                                        CHAPTER 7—Reduced Infrastructure Burden                     44
REGIONAL STORMWATER              AND              major component.186 For example, Portland,
WASTEWATER IMPACTS                                Oregon is a leader in integrating innovative
                                                  environmental technology into its city plan­
As outlined in previous chapters, stormwater      ning and policies. The city’s building codes
runoff can cause a number of serious prob­         require on-site stormwater management
lems including water pollution, flooding,          for all new construction projects, and their
groundwater recharge deficits, and damage          stormwater manual encourages the use of
to stream ecology.183 These impacts translate     best management practices.187 A number of
into high costs to municipalities, and using      smaller cities and towns have also started
conventional methods alone to control them        to embrace green infrastructure planning.
can be an expensive use of public funds. This     In Kansas City, Missouri, planners are imple­
is particularly true in regions of the country    menting the 10,000 Rain Garden Initiative,
with older infrastructure, including the Pacific   which will create 10,000 such gardens to
Northwest, Northeast, and Great Lakes. In         help the city achieve its 20-year Wet Weather
these regions, stormwater is often channeled      Solutions Program. This is one of the largest
into the same pipes as sewage (i.e., combined     infrastructure projects in the city’s history.188
sewers). With large areas of impervious sur­
face and development, heavy rain events can       COST EFFECTIVENESS
push these combined pipes beyond capacity,
causing them to overflow. These “combined          Looking at stormwater management from
sewer overflows,” or CSOs, result in large         a regional or watershed scale is important
amounts of untreated waste overflowing into        when considering costs. The piping, channels,
waterways, making them a primary source of        and treatment plants of a traditional storm-
pollution for many water bodies. The Clean        water infrastructure are expensive to build,
Water Act requires that combined sewer sys­       operate, and maintain, and are not the most
tems be updated to prevent CSOs, however,         effective way of controlling stormwater.189
these upgrades are cost prohibitive for many      The EPA’s Assistant Administrator for Water
cities and towns.184 The EPA’s 2000 Clean         has stated that:
Watersheds Needs Survey estimates that $56          “Green infrastructure may save capital
billion in capital investment nationally was        costs associated with digging big tun­
needed for CSO controls.185                         nels and centralized stormwater ponds,
The regional impact of stormwater runoff             operations and maintenance expenses for
and CSOs cannot be properly controlled by           treatment plants, pipes, and other hard
sporadic site-by-site controls, or large end­       infrastructure; energy costs for pumping
of-pipe conventional stormwater treatment           water; and costs of wet weather treatment
alone. A coordinated, area-wide planning            and repairing of stormwater and sewage
effort is required. Major cities throughout the      pollution impacts, such as stream bank
country, including Portland (Oregon), Seattle,      restoration.”190
Chicago, and Philadelphia, have started to        Potential cost savings are important to com­
invest in land use planning and infrastructure    munities throughout the United States that
development with green infrastructure as a        are working to comply with federal storm-

                                Green Parking Lot Resource Guide—February 2008                        45
water management regulations. According           the water body, rather than piping it directly 

to an 2007 report evaluating the potential        into the river. They found that, at a cost of
of a major storm water minimization pro­          less than $50,000 per year, the wetlands not
gram, “the use of green infrastructure can        only diminished stormwater flows, but also
help communities meet their overall water         successfully removed pollutants from runoff,
resource management goals and reduce the          including 80 percent of suspended solids,
costs (or free up funding for other uses such     70 percent of phosphorus, and 60 percent
as land purchases) of constructing and main­      of oxygen depleting compounds and heavy
taining engineered infrastructure including       metals. The high efficacy of the wetlands
pipes and treatment systems.”191 For example,     made them a cost-effective strategy for
in Kane County, Illinois, researchers estimated   improving the river’s water quality.194 In Port­
economic benefits of downstream stormwa­           land, Oregon, the City has found that adopt­
ter management through green infrastruc­          ing a variety of green infrastructure tech­
ture practices implemented upstream would         niques over the course of a 10 year period has
save approximately $4 million, money that         avoided over 1.2 billion gallons of runoff and
would otherwise have been spent on culvert        has reduced CSO events by 10 percent.195
replacement or upgrades for stormwater
                                                  It is clear that stormwater management must
diversion. When both flood reduction and in­
                                                  be elevated to a key urban planning and
frastructure savings are considered, the green
                                                  policy issue as local governments seek to
infrastructure practices were found to be ap­
                                                  reduce stormwater impacts cost-effectively.
proximately $300-$700 less expensive per de­
                                                  Promoting green infrastructure regionally or
veloped acre.192 Portland, Oregon estimates
                                                  watershed-wide will help control the cumula­
its Green Streets stormwater infrastructure
                                                  tive impact that stormwater from multiple
design saves 40 percent in costs compared to
                                                  sources has on stormwater infrastructure.
conventional stormwater infrastructure (also
                                                  Even in cases where green infrastructure
see Green Streets case study at the end of this
                                                  investments are not more cost-effective in
                                                  the short-term, the long-term environmental
Green infrastructure can be a cost effective       and social benefits can be quite significant
replacement or complement for other water         to livability and sustainability on a regional
quality improvement strategies. For example,      scale. These benefits have been explored
for 10 years, a demonstration project in the      throughout this guide, and include enhanced
Rouge River area of Michigan has been utiliz­     groundwater recharge, pollution prevention,
ing 14 acres of wetlands (two thirds of which     increased carbon sequestration, HIE mitiga­
are constructed) along the river’s banks to       tion, improved air quality, and increased
naturally treat stormwater before it enters       green space and wildlife habitat.196

                                         CHAPTER 7—Reduced Infrastructure Burden                     46

For over a decade, the City of Portland,
Oregon has been pursuing new approaches
to stormwater management. Known for its
wet weather with the third highest number
of rainy days annually in the U.S., Portland
typically averages 37 inches of rain a year.197
Approximately 66 percent of the resulting
stormwater runoff comes from streets and
rights of way.198 For this reason, the City
created “Green Streets,” a city-wide land use
planning effort for stormwater management
focused on transportation-related develop­
ment (i.e. parking lots, streets). Defining a
Green Street as “one that uses vegetated
                                                   One of many rain gardens being built throughout Portland as part of the city’s
facilities to manage stormwater runoff as its       Green Streets program.
source,” this program is part of a concert of
initiatives that the city is undertaking to help   surface runoff through the use of infiltration
them reach their goal of removing 60 million       basins. In 2006, this project was recognized
gallons of stormwater annually by 2011.199, 200    with the national American Society of Land-
                                                   scape Architects Design Award.201 By starting
Although city officials have been promoting          with demonstration projects, the City was
a green streets theme for a number of years,       able to monitor results and incorporate les­
in 2005 an interdisciplinary team of area          sons learned into more effective stormwater
experts, including government officials, en-         designs that could be replicated on a city­
gineers, planners, landscape architects, and       wide scale.202
watershed managers refocused the program
by taking a fresh look at opportunities for its    In April 2007, the Portland City Council of-
implementation. This multi-disciplinary ap­        ficially endorsed the enhanced Green Streets
proach provided the breadth of knowledge           program by approving an innovative storm­
necessary to properly address comprehensive        water management plan comprised of a reso­
stormwater management, and was invalu­             lution, report, and policy. The overarching
able to successfully implementing the Green        goal of this program is to “comprehensively
Streets program.                                   address numerous city goals for neighbor-
                                                   hood livability, sustainable development,
In revamping the Green Streets program,            increased green spaces, stormwater manage-
Portland focused on learning through dem­          ment, and groundwater protection.”203 The
onstration projects. This includes a project on    city council articulated several objectives for
the Portland State University campus built         achieving this goal, including a neighbor-
in 2005 to treat 8,000 square-feet of street       hood planning initiative, further stakeholder

                                  Green Parking Lot Resource Guide—February 2008                                                    47
outreach, the pursuit of more funding mecha-    For more information on the Portland, 

nisms, and ultimately the establishment of      Oregon Green Streets program, please visit 

even more Green Streets. As a short term        the Green Streets Web site at: 

objective, the City is planning on developing

500 additional Green Street projects to ad-     cfm?c=44407&.

dress combined sewer overflow issues.204

                                       CHAPTER 7—Reduced Infrastructure Burden                 48

PLANNING RESOURCES                                  U.S. EPA, (2006), Parking Spaces/Community
                                                       Places: Finding the Balance through Smart
American Rivers and SmartGrowth America,
                                                       Growth Solutions, EPA 231-K-06-001:
  (2002), Paving Our Way to Water Short­
                                                    U.S. EPA, (2005), Using Smart Growth Tech­
Boston Metropolitan Area Planning Council,
                                                       niques as Stormwater Best Management
   (2006), Sustainable Transportation Toolkit:
                                                       Practices, EPA 231-B-05-002:
Center for Neighborhood Technology, (2006),            sg_stormwater_BMP.pdf
   Paved Over: Surface Parking Lots or Op­
                                                    U.S. EPA, (1999), Parking Alternatives: Mak­
   portunities for Tax—Generating Sustain­
                                                       ing Way for Urban Infill and Brownfield
   able Development, November 2006:
                                                       Redevelopment, EPA231-K-99-001.

Gibbons, J. (1999), Parking Lots—Technical          STORMWATER MANAGEMENT BMP
   Paper #5, University of Connecticut              RESOURCES
   Nonpoint Education for Municipal Officials         Chester County, Pennsylvania Water
   (NEMO) program:             Resources Compendium, (2005), Water­
   tools/publications/tech_papers/                    shed Primer:
   tech_paper_5.pdf.                                  cwp/view.asp?a=3&q=607722.
Litman, T., (2006), Parking Management:             Community Design and Architecture, (2005),
   Strategies, Evaluation and Planning,               Stormwater Guidelines for Green Dense
   Victoria Transport Policy Institute, April 25,     Redevelopment, U.S. EPA:
   2006:                   dced/pdf/Stormwater_Guidelines.pdf.
Maryland Governor’s Office of Smart Growth,           Kloss, C. and Calarusse, C. (2006), Rooftops
  (2005), Driving Urban Environments:                  to Rivers: Green Strategies for Controlling
  Smart Growth Parking Best Practices:                 Stormwater and Combined Sewer Over­                         flows, Natural Resources Defense Council:
Shoup, D., (2005), The High Cost of Free Park­
   ing, APA Planners Press.                            contents.asp.

Shoup, D., (1999), The Trouble with Minimum         Minnesota Pollution Control Agency, (2000),
   Parking Requirements, Transportation                Protecting Water Quality in Urban Areas:
   Research Part A, Vol. 33, pgs. 549-574:                                sw-bmpmanual.html.

                                  Green Parking Lot Resource Guide—February 2008                     49
Muthukrishnan, S. and Selvakumar, A., (2004),        Wossink, A. and Hunt, B., (2003), An Evalua­
  The Use of Best Management Practices                 tion of the Costs and Benefits of Structural
  (BMPs) in Urban Watersheds, U.S. En­                 Stormwater Best Management Practices
  vironmental Protection Agency, EPA­                  in North Carolina, North Carolina State
  600-R-04-184.                                        University:
NAHB Research Center, Inc., (2003), The
  Practice of Low Impact Development, U.S.
  Department of Housing and Urban Devel­             NATURAL LANDSCAPING            AND
  opment:              IRRIGATION
                                                     City of Chicago, (2003), A Guide to Storm-
U.S. EPA, (2007), National Pollutant Discharge          water Best Management Practices: www.
   Elimination (NPDES) Fact Sheets:                                     GuideTo%20Stormwater%20BMP.pdf.
   index.cfm?action=factsheet_                       Florida Department of Environmental Protec­
   results&view=specific&bmp=75.                         tion, (2006), Water Best Management
                                                        Practices, Florida Green Lodging Program:
U.S. EPA, (2007), Polluted Runoff (Nonpoint    
   Source Pollution) Web site:                          gr_h2o.htm.
                                                     Illinois Conservation Foundation and Chi­
U.S. EPA, (1999), Preliminary Data Summary                cago Wilderness, (2005), Changing Cost
   of Urban Stormwater Best Management                    Perceptions: An Analysis of Conserva­
   Practices, EPA-821-R-99-012, August 1999:              tion Development:                        CDF_Resources/Cost%20Analysis%20
   stormwater.                                            -%20Part%201%20-%20Report%20-%20
U.S. EPA, (1999), Storm Water Municipal Tech­             with%20Exec%20
   nologies, EPA-832-F-99-019:                            Summary.pdf.                  North Carolina Department of Environment
Washington State Department of Ecology,                and Natural Resources, (2005), Water
  (2004), Stormwater and Economic Devel­               Efficiency: Water Management Options,
  opment, 04-10-001:                   Division of Pollution Prevention and Envi­
  pubs/0410001.pdf.                                    ronmental Assistance:
Weiss, P., Gulliver, J., and Erickson, A., (2007),
  Cost and Pollutant Removal of Storm-Wa­            Pennsylvania Department of Environmental
  ter Treatment Practices, Journal of Water             Protection, (2006), Pennsylvania Stormwa­
  Resources Planning and Management,                    ter Best Management Practices Manual:
  Volume 133, Issue 3, pp. 218-229, May/                Chapter 5, 363-0300-002: www.dep.state.
  June 2007.                                  
                                                                                 Key Resources       50
State of California Energy Commission, (2005),   Cahill, T. et al, (2005), Stormwater Manage­
   California’s Water-Energy Relationship,          ment with Porous Pavements, Govern­
   CEC-700-2005-011-SF:                 ment Engineering, March-April 2005, pp.        14-19:
   CEC-700-2005-011-SF.PDF.                         porous.pdf.

U.S. Department of Energy, (2006), Federal       Diyagama, T., et al., (2004), Permeable Pave­
   Energy Management Program—Water                  ment Design Guidelines - Draft, prepared
   Efficiency:           for North Shore City, EcoWater Solutions,
   femp/water/water_bmp3.html.                      and Rodney District: www.northshorecity.
U.S. Department of Energy, (2001), Greening
   Federal Facilities, second edition:
                                                 Hinman, C., (2005), Low Impact Development
U.S. EPA, (2004), Conference Summary,
                                                    Technical Guidance Manual for Puget
   Landscaping with Native Plants: Exploring
                                                    Sound, Puget Sound Action Team, publi­
   the Environmental, Social and Economic
                                                    cation number PSAT 05-03, p. 121:
   Benefits Conference December 6 - 7, 2004:
                                                 Idaho Department of Environmental Quality,
U.S. EPA, GreenScapes Web site Resource:
                                                    (2005), Storm Water Best Management
                                                    Practices Catalog:
U.S. EPA, Landscaping with Native Plants—           water/data_reports/storm_water/catalog/
   Greenacres Web site Resource: www.epa.           sec_3/bmps/11.pdf.
                                                 Knox County, Tennessee, (2007), Stormwater
U.S. EPA, (2003), Water-Efficient Landscaping:       Management Ordinance, Volume 1 and 2:               
                                                 New Jersey Department of Environmental
Wolf, K., (2004), Trees, Parking, and Green        Protection, (2004), New Jersey Stormwa­
  Law: Strategies for Sustainability: www.ur­      ter Best Management Practices Manual:
  Citation.2004-07-14.1757/file_name.               NJ_SWBMP_9.7.pdf.

ALTERNATIVE PARKING SURFACE                      New York State Department of Environmen­
MATERIALS                                          tal Conservation, (2003), New York State
                                                   Stormwater Management Design Manual,
Brattebo, B. and Booth, D., (2003), Long-term      with updated sections from 2007:
   stormwater quantity and quality perfor­
   mance of permeable pavement systems,
   Water Research, 37, 4368-4376, November       Pennsylvania Department of Environmental
   2003.                                            Protection, (2005), Draft Pennsylvania

                                Green Parking Lot Resource Guide—February 2008                   51
   Stormwater Best Management Manual:                Administrator on Water, to USEPA Regional                 Administrators regarding Using Green
   watermgt/wc/subjects/                             Infrastructure to Protect Water Quality in
   stormwatermanagement/BMP%20                       Storm Water, CSO, Non-point Source and
   Manual/BMP%20Manual.htm.                          Other Water Programs, March 5, 2007.

U.S. Department of Transportation, (2007),        Kloss, C. and Calarusse, C., (2006), Rooftops
   Stormwater Best Management Practices              to Rivers: Green Strategies for Controlling
   in an Ultra Urban Setting:          Stormwater and Combined Sewer Over­
   gov/environment/ultraurb/uubmp3p6.htm.            flows, Natural Resources Defense Council:
U.S. EPA, National Pollutant Discharge Elimi­
   nation System (NPDES)—National Menu
   of Stormwater Best Management Practices        U.S. EPA, (2007), Green Infrastructure Pro­
   (i.e. Porous Pavement Fact Sheet, Alterna­        gram—A report evaluating the concept of
   tive Pavers Fact Sheet): http://cfpub.epa.        a major storm water minimization pro­
   gov/npdes/stormwater/menuofbmps/.                 gram, utilizing green infrastructure and
                                                     related methods, prepared by Prepared
REDUCED INFRASTRUCTURE BURDEN                        by Metropolitan Sewer District of Greater
Center for Neighborhood Technology, (2007),          Cincinnati et al:
   Green Infrastructure Performance: www.            downloads/wetweather/greenreport/           Files/Green_Report.pdf.

City of Portland, Oregon Green Streets Program:   U.S. EPA, (2007), National Pollutant Discharge
                                                     Elimination System (NPDES): Environmen­
   Green Streets Program Web site accessed           tal Benefits of Green Infrastructure:
   cfm?c=eeeah                                       greeninfrastructure/information.
   Green Street Cross-Bureau Team Report –           cfm#enviroben.
   Phase I, March 2006: www.portlandonline.       U.S. EPA, (2007), National Pollutant Discharge
   com/shared/cfm/image.cfm?id=123793                Elimination Systems (NPDES): Green In­
   Green Street Cross-Bureau Team Report—            frastructure:
   Phase 2:                  home.cfm?program_id=298.
   shared/cfm/image.cfm?id=153974.                U.S. EPA, Report to Congress: Impacts and
Dunn, A. and Stoner, N., (2007), Green Light         Control of CSOs and SSOs, Office of Water,
  for Green Infrastructure, The Environ­             EPA-833-R-04-001, August 2004.
  mental Forum, May/June 2007, reprinted          Water Environment Research Foundation,
  by the Environmental Law Institute and            (2007), Portland Oregon: Building a
  accessed at:              Nationally Recognized Program Through
  green_light_gi.pdf.                               Innovation and Research, accessed as:
Grumbles, B.H., (2007), Memorandum from   ­
   Benjamin H. Grumbles, USEPA Assistant            ies_port_or.html.

                                                                               Key Resources       52
ENDNOTES                                                                      Requirements, Transportation Research Part A, Vol. 33, pgs.
      Van Metre, P. et al, (2006), Parking Lot Sealcoat: A Major        16	
      Source of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban        17	
      and Suburban Environments, USGS Fact Sheet 2005-3147,                   Halifax Regional Municipality, (2003), Parking Supply Man­
      January 2006.                                                           agement Strategies, accessed at:­
      N.Y. State Department of Transportation, (2003), Safety           18	
      Bulletin: Paving with Hot Mix Asphalt, SB-03-3, accessed                U.S. EPA, (1999), Parking Alternatives: Making Way for Urban
      at:                    Infill and Brownfield Redevelopment, EPA231-K-99-001.
      pdf#search=%22fumes%20from%20hot%20mix%20as­                      19	
      phalt%22.                                                         20	
                                                                              Maryland Governor’s Office of Smart Growth, (2005),
      U.S. EPA, (1992), Cooling Our Communities,                              Driving Urban Environments: Smart Growth Parking Best
      GPO#055-000-00371-8, January 1992, accessed at: www.                    Practices, page 4, accessed at: www.smartgrowth.state., as cited in Pavement Busters Guide (2002), page      
      10, Victoria Transport Policy Institute.                          21	
      Gibbons, J., (1999), Pavements and Surface Materials, Tech­       22	
      nical Paper #8, pg. 2, University of Connecticut Nonpoint               U.S. EPA, (1999,) Parking Alternatives: Making Way for Urban
      Education for Municipal Officials (NEMO) program, accessed                Infill and Brownfield Redevelopment, EPA231-K-99-001.
      at:         23	
                                                                              Boston Metropolitan Area Planning Council, (2006), Sustain­
      tech_paper_8.pdf.                                                       able Transportation Toolkit: Parking, accessed at:
      Pomeranz, Melvin, Lawrence Berkeley National Laboratory,       in June 2007.
      Benefits of Cooler Pavements,­          24	
                                                                              Maryland Governor’s Office of Smart Growth, (2005),
      land/Pavements/Overview/index.html,                                     Driving Urban Environments: Smart Growth Parking Best
      Miramontes, E.M. University of California at Berkeley, (1997),          Practices, page 4, accessed at: www.smartgrowth.state.
      The Bay Area’s Love-Hate Relationship With The Motorcar,      
      San Francisco Examiner, October 20, 1997, as cited in Gib­        25	
                                                                              Gibbons, J., (1999), Parking Lots, Technical Paper #5,
      bons, J. (1999), Parking Lots, Technical Paper #5, page 2,              University of Connecticut Nonpoint Education for Municipal
      University of Connecticut Nonpoint Education for Municipal              Officials (NEMO) program, accessed at: http://nemo.uconn.
      Officials (NEMO) program, accessed at: http://nemo.uconn.                 edu/tools/publications/tech_papers/tech_paper_5.pdf.
      edu/tools/publications/tech_papers/tech_paper_5.pdf.              26	
                                                                              University of Connecticut Nonpoint Education for Municipal
      Benfield, F.K. et al, (1999), Once There Were Greenfields:                Officials (NEMO) program, (1999), Parking Lots - Technical
      How Urban Sprawl is Undermining America’s Environment,                  Paper #5, accessed at:­
      Economy, and Social Fabric, Natural Resources Defense                   cations/tech_papers/tech_paper_5.pdf.
      Council (NRDC), as cited in Paving Our Way to Water Short­        27	
      ages, NRDC, American Rivers, Smart Growth America, 2002,                Minnesota Pollution Control Agency, (2000), Protecting
      page 6.                                                                 Water Quality in Urban Areas, accessed at: www.pca.state.
      Maryland Governor’s Office of Smart Growth (2005) Driving           28	
      Urban Environments: Smart Growth Parking Best Practices,                Kloss, C. and Calarusse, C., (2006), Rooftops to Rivers: Green
      page 4, accessed at:                       Strategies for Controlling Stormwater and Combined Sewer
                                                                              Overflows, Natural Resources Defense Council, accessed at:
      Maryland Governor’s Office of Smart Growth, (2005),                 29	
                                                                              Muthukrishnan, S. and Selvakumar, A., (2004), The Use of
      Driving Urban Environments: Smart Growth Parking Best                   Best Management Practices (BMPs) in Urban Watersheds,
      Practices, page 23, accessed at: www.smartgrowth.state.                 U.S. Environmental Protection Agency, EPA-600-R-04-184.                                                            30	
      Permeable pavers should not be used for the aisles and            31	
      main (primary) vehicle travel areas in high traffic lots                  Ibid.
      because they are not strong enough to withstand constant          32	
                                                                              U.S. EPA, (2007), National Pollutant Discharge Elimination
      weight and use, however in most cases they would be ideal               (NPDES)—Grassed Swales Fact Sheet, accessed at: http://
      for use in parking stalls, crosswalks, or overflow (i.e. second­
      ary) parking areas.                                                     cfm?action=factsheet_results&view=specific&bmp=75.
      U.S. EPA, (2001), Functions and Values of Wetlands, EPA           33	
                                                                              Muthukrishnan, S. and Selvakumar, A., (2004), The Use of
      843-F-01-002c, September 2001, accessed at: www.epa.                    Best Management Practices (BMPs) in Urban Watersheds,
      gov/owow/wetlands/pdf/fun_val.pdf.                                      U.S. Environmental Protection Agency, EPA-600-R-04-184.
      Shoup, D., (2005), The High Cost of Free Parking, APA Plan­       34	
                                                                              NAHB Research Center, Inc., (2003), The Practice of Low Im­
      ners Press, pages 2-3.                                                  pact Development, U.S. Department of Housing and Urban
      Litman, T., (2002), Pavement Busters guide, Victoria Trans­             Development, accessed at:
      port Policy Institute, accessed at:            PDF/practlowimpctdevel.pdf.
      in June 2007.                                                     35	
                                                                              Muthukrishnan, S. and Selvakumar, A., (2004), The Use of
      Standards are typically determined by referring to the                  Best Management Practices (BMPs) in Urban Watersheds,
      Institute of Transportation Engineers guidance documents                U.S. Environmental Protection Agency, EPA-600-R-04-184.
      or by researching the requirements of surrounding towns.          36	
      Shoup, D., (1999), The Trouble with Minimum Parking

                                                 Green Parking Lot Resource Guide—February 2008                                                53
37	                                                                    54	
      ibid.                                                                  Information for this case study was obtained from: LaCroix,
38	                                                                          R., et al, (2004), Reining in the Rain: A case study of the city
      U.S. EPA, (2007), National Pollutant Discharge Elimination
                                                                             of Bellingham’s use of rain gardens to manage stormwater,
      (NPDES) - Grassed Swales Fact Sheet, accessed at: http://
                                                                             accessed at:
                                                                             book.pdf and personal communication with Bill Reilly, City
                                                                             of Bellingham Public Works Department.
      Muthukrishnan, S. and Selvakumar, A., (2004), The Use of         55	
                                                                             King County Environmental Purchasing Program, (2007),
      Best Management Practices (BMPs) in Urban Watersheds,
                                                                             Recycled Asphalt Fact Sheet, King County, Washington, ac­
      U.S. Environmental Protection Agency, EPA-600-R-04-184.
                                                                             cessed at:
      Community Design and Architecture, (2005), Stormwater            56	
                                                                             U.S. EPA, (2005), EPA Lessons Learned Paper – Heifer Inter­
      Guidelines for Green Dense Redevelopment, U.S. EPA, ac­
                                                                             national, page 5.
      cessed at:
      pdf.                                                                   Similarly, the new paving product RESINPAVE™ is manu­
41	                                                                          factured from renewable resources, contains no petroleum
      Minnesota Pollution Control Agency, (2000), Protection
                                                                             ingredients, and is highly reflective. However, it too is
      Water Quality in Urban Areas, March 1, 2000, accessed at:
                                                                             impervious, and is also still in experimental stages.
42	                                                                          New York State Department of Environmental Conservation,
      Washington State Department of Ecology, (2004), Storm-
                                                                             (2007), New York State Stormwater Design Manual - Chapter
      water and Economic Development, 04-10-001, accessed at:
                                                                             9, accessed at:
43	                                                                          U.S. EPA, (2007), National Pollutant Discharge Elimination
      Kloss, C. and Calarusse, C., (2006), Rooftops to Rivers: Green
                                                                             System (NPDES) – Porous Pavement Fact Sheet, accessed at:
      Strategies for Controlling Stormwater and Combined Sewer
      Overflows, Natural Resources Defense Council, accessed at:
44	                                                                          Ibid.
      Van Metre, P. et al, (2006), Parking Lot Sealcoat: A Major
      Source of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban             New Jersey Department of Environmental Protection,
      and Suburban Environments, USGS Fact Sheet 2005-3147,                  (2004), New Jersey Stormwater Best Management Practices
      January 2006.                                                          Manual, accessed at:
45	                                                                          NJ_SWBMP_9.7.pdf.
      U.S. EPA, (2007), Polluted Runoff (Nonpoint Source Pollu­
      tion) website, accessed at:               U.S. EPA, (2007), National Pollutant Discharge Elimination
      html.                                                                  System (NPDES) – Porous Pavement Fact Sheet, accessed at:
46	                                                                ­
      Muthukrishnan, S. and Selvakumar, A., (2004), The Use of
      Best Management Practices (BMPs) in Urban Watersheds,
      U.S. Environmental Protection Agency, EPA-600-R-04-184.                Pennsylvania Department of Environmental Protection,
47	                                                                          (2005), Draft Pennsylvania Stormwater Best Management
      U.S. EPA, (1999), Storm Water Technology Fact Sheet Infiltra­
                                                                             Manual, Section 6 - Comprehensive Stormwater Manage­
      tion Trench, EPA-832-F-99-019, accessed at:
                                                                             ment: Structural BMPs, accessed at:
      Wossink, A. and Hunt, B., (2003), An Evaluation of the Costs           Section06-StructuralBMPs-part1.pdf
      and Benefits of Structural Stormwater Best Management             64	
                                                                             Knox County, Tennessee, (2007), Stormwater Management
      Practices in North Carolina, North Carolina State University,
                                                                             Ordinance, Volume 2 (technical guidance), accessed at:
      accessed at:
49	                                                                          Pennsylvania Department of Environmental Protection,
      U.S. EPA, (1999), Preliminary Data Summary of Urban
                                                                             (2005), Draft Pennsylvania Stormwater Best Management
      Stormwater Best Management Practices, EPA-821-R-99-012,
                                                                             Manual, Section 6 - Comprehensive Stormwater Manage­
      August 1999, accessed at:
                                                                             ment: Structural BMPs, accessed at:
      Muthukrishnan, S. and Selvakumar, A., (2004), The Use of               Section06-StructuralBMPs-part1.pdf
      Best Management Practices (BMPs) in Urban Watersheds,            66	
                                                                             Frazer, L., (2006), Paving Paradise: The Peril of Impervious
      U.S. Environmental Protection Agency, EPA-600-R-04-184.
                                                                             Surfaces, Environ Health Perspect. 2006 Jan;114(1):A21.
      Kloss, C. and Calarusse, C., (2006), Rooftops to Rivers: Green   67	
                                                                             Cahill, T. et al, (2005), Stormwater Management with Porous
      Strategies for Controlling Stormwater and Combined Sewer
                                                                             Pavements, Government Engineering, March-April 2005,
      Overflows, Natural Resources Defense Council, accessed at:
                                                                             pp. 14-19, accessed at:
      Wossink, A. and Hunt, B., (2003), An Evaluation of the Costs     68	
                                                                             U.S. EPA, (2007), National Pollutant Discharge Elimination
      and Benefits of Structural Stormwater Best Management
                                                                             System (NPDES) – Porous Pavement Fact Sheet, accessed at:
      Practices in North Carolina, North Carolina State University,
      accessed at:
53	                                                                          Pennsylvania Department of Environmental Protection,
      Chester County, Pennsylvania Water Resources Compen­
                                                                             (2005), Draft Pennsylvania Stormwater Best Management
      dium, (2005), Watershed Primer Part 4: Land Use impacts
                                                                             Manual, Section 6 - Comprehensive Stormwater Manage­
      and Watershed Economics, accessed at: http://dsf.chesco.
                                                                             ment: Structural BMPs, accessed at:

                                                                                                                    Key Resources               54
      McDaniel, R., (2004), Field Evaluation of Porous Asphalt            dex.cfm?action=factsheet_results&view=specific&bmp=71.
      Pavement – Research Summary, Purdue University,               84	
                                                                          Knox County, Tennessee, (2007), Stormwater Management
      accessed at:
                                                                          Ordinance, Volume 2 (technical guidance), accessed at:
      Idaho Department of Environmental Quality, (2005), Storm      85	
                                                                          New York State Department of Environmental Conservation,
      Water Best Management Practices Catalog, accessed at:
                                                                          (2007), New York State Stormwater Design Manual - Chap­
                                                                          ter 9, accessed at:
72	                                                                       Ibid.
      New Jersey Department of Environmental Protection,
      (2004), New Jersey Stormwater Best Management Practices             Pennsylvania Department of Environmental Protection,
      Manual, accessed at:               (2005), Draft Pennsylvania Stormwater Best Management
      NJ_SWBMP_9.7.pdf.                                                   Manual, Section 6 - Comprehensive Stormwater Manage­
73	                                                                       ment: Structural BMPs, accessed at:
      U.S. EPA, (2007), National Pollutant Discharge Elimina­
      tion System (NPDES) – Alternative Pavers Fact Sheet,
      accessed at:­
      water/menuofbmps/index.cfm?action=factsheet_                        Cahill, T. et al, (2005), Stormwater Management with Porous
      results&view=specific&bmp=134.                                       Pavements, Government Engineering, March-April 2005,
74	                                                                       pp. 14-19, accessed at:
      Idaho Department of Environmental Quality, (2005), Storm
      Water Best Management Practices Catalog, accessed at:
                                                                    88                   U.S. EPA, (2007), National Pollutant Discharge Elimination
      catalog/sec_3/bmps/11.pdf.                                          System (NPDES) – Porous Pavement Fact Sheet, accessed at:
75	                                                             ­
      Idaho Department of Environmental Quality, (2005), Storm
      Water Best Management Practices Catalog, accessed at:
                                                                    89                   Ibid.
      catalog/sec_3/bmps/11.pdf.                                    90	
                                                                          New York State Department of Environmental Conservation,
      New York State Department of Environmental Conservation,            (2007), New York State Stormwater Design Manual - Chap­
      (2007), New York State Stormwater Design Manual - Chap­             ter 9, accessed at:
      ter 9, accessed at:       91	
                                                                          Pennsylvania Department of Environmental Protection,
      Idaho Department of Environmental Quality, (2005), Storm            (2005), Draft Pennsylvania Stormwater Best Management
      Water Best Management Practices Catalog, accessed at:               Manual, Section 6 - Comprehensive Stormwater Manage­                   ment: Structural BMPs, accessed at:
      catalog/sec_3/bmps/11.pdf.                                          dep/subject/advcoun/stormwater/Manual_DraftJan05/
78	                                                                       Section06-StructuralBMPs-part1.pdf.
      US Department of Transportation, (2007), Stormwater Best
      Management Practices in an Ultra Urban Setting, accessed            New Jersey Department of Environmental Protection,
      at:                 (2004), New Jersey Stormwater Best Management Practices
      htm.                                                                Manual, accessed at:
79	                                                                       NJ_SWBMP_9.7.pdf.
      Diyagama, T., et al. ,(2004), Permeable Pavement Design
      Guidelines - Draft, prepared for North Shore City, EcoWater         Pennsylvania Department of Environmental Protection,
      Solutions, and Rodney District, accessed at: www.northsho­          (2005), Draft Pennsylvania Stormwater Best Management­                  Manual, Section 6 - Comprehensive Stormwater Manage­
      able_Pavement_Design_Guidelines_Draft_092004.pdf.                   ment: Structural BMPs, accessed at:
80	                                                                       dep/subject/advcoun/stormwater/Manual_DraftJan05/
      US Department of Transportation, (2007), Stormwater Best
      Management Practices in an Ultra Urban Setting, accessed
      at:                 Ibid.
      htm.                                                          95	
      New York State Department of Environmental Conservation,      96	
                                                                          Pennsylvania Department of Environmental Protection,
      (2007), New York State Stormwater Design Manual - Chap­
                                                                          (2005), Draft Pennsylvania Stormwater Best Management
      ter 9, accessed at:
                                                                          Manual, Section 6 - Comprehensive Stormwater Manage­
      Cahill, T. et al, (2005), Stormwater Management with Porous         ment: Structural BMPs, accessed at:
      Pavements, Government Engineering, March-April 2005,                dep/subject/advcoun/stormwater/Manual_DraftJan05/
      pp. 14-19, accessed at:              Section06-StructuralBMPs-part1.pdf.
                                                                          New York State Department of Environmental Conservation,
      U.S. EPA, (2007), National Pollutant Discharge Elimination          (2007), New York State Stormwater Design Manual - Chap­
      System (NPDES) – Porous Pavement Fact Sheet, accessed at:           ter 9, accessed at:­          97	
                                                                          Cahill, T. et al, (2005), Stormwater Management with Porous
                                                                          Pavements, Government Engineering, March-April 2005,
      New York State Department of Environmental Conservation,            pp. 14-19, accessed at:
      (2007), New York State Stormwater Design Manual - Chap­             porous.pdf.
      ter 9, accessed at:       98	
                                                                          New York State Department of Environmental Conservation,
      U.S. EPA, (2007), National Pollutant Discharge Elimination          (2007), New York State Stormwater Design Manual - Chap­
      System (NPDES) – Porous Pavement Fact Sheet, accessed at:           ter 9, accessed at:­

                                               Green Parking Lot Resource Guide—February 2008                                           55
       U.S. EPA, (2007), National Pollutant Discharge Elimination              dex.cfm?action=factsheet_results&view=specific&bmp=71.
       System (NPDES) – Porous Pavement Fact Sheet, accessed at:        114	
                                                                               Pennsylvania Department of Environmental Protection,­
                                                                               (2005), Draft Pennsylvania Stormwater Best Management
                                                                               Manual, Section 6 - Comprehensive Stormwater Manage­
       Cahill, T. et al, (2005), Stormwater Management with Porous             ment: Structural BMPs, accessed at:
       Pavements, Government Engineering, March-April 2005,                    dep/subject/advcoun/stormwater/Manual_DraftJan05/
       pp. 14-19, accessed at:                  Section06-StructuralBMPs-part1.pdf.
       porous.pdf.                                                      115	
                                                                               Cahill, T. et al, (2005), Stormwater Management with Porous
       Pennsylvania Department of Environmental Protection,                    Pavements, Government Engineering, March-April 2005,
       (2005), Draft Pennsylvania Stormwater Best Management                   pp. 14-19, accessed at:
       Manual, Section 6 - Comprehensive Stormwater Manage­                    porous.pdf.
       ment: Structural BMPs, accessed at:         116	
                                                                               Pennsylvania Department of Environmental Protection,
                                                                               (2005), Draft Pennsylvania Stormwater Best Management
                                                                               Manual, Section 6 - Comprehensive Stormwater Manage­
       New York State Department of Environmental Conservation,                ment: Structural BMPs, accessed at:
       (2007), New York State Stormwater Design Manual - Chapter               dep/subject/advcoun/stormwater/Manual_DraftJan05/
       9, accessed at:                     Section06-StructuralBMPs-part1.pdf.
103	                                                                    117	
       Hinman, C., (2005), Low Impact Development Technical                    New York State Department of Environmental Conservation,
       Guidance Manual for Puget Sound, Puget Sound Action                     (2007), New York State Stormwater Design Manual - Chapter
       Team, publication number PSAT 05-03, accessed at: www.                  9, accessed at:            118	
                                                                               Pennsylvania Department of Environmental Protection,
                                                                               (2005), Draft Pennsylvania Stormwater Best Management
       Bean, E., et al, (2007), Field Survey of Permeable Pavement             Manual, Section 6 - Comprehensive Stormwater Manage­
       Surface Infiltration Rates, J. Irrig. and Drain. Engrg., Volume          ment: Structural BMPs, accessed at:
       133, Issue 3, pp. 249-255, May/June 2007.                               dep/subject/advcoun/stormwater/Manual_DraftJan05/
105	                                                                           Section06-StructuralBMPs-part1.pdf.
       U.S. EPA, (2007), National Pollutant Discharge Elimination
       System (NPDES) – Porous Pavement Fact Sheet, accessed at:               U.S. EPA, (2007), National Pollutant Discharge Elimina­­                    tion System (NPDES) – Alternative Pavers Fact Sheet,
       dex.cfm?action=factsheet_results&view=specific&bmp=71                    accessed at:­
       Hinman, C., (2005), Low Impact Development Technical
       Guidance Manual for Puget Sound, Puget Sound Action
       Team, publication number PSAT 05-03, p. 121, accessed at:               New York State Department of Environmental Conservation,­                  (2007), New York State Stormwater Design Manual - Chapter
       dex.htm.                                                                9, accessed at:
106	                                                                    121	
       Hinman, C., (2005), Low Impact Development Technical                    Another option is to also include coal ash in the concrete,
       Guidance Manual for Puget Sound, Puget Sound Action                     which improve its strength and durability while using a
       Team, publication number PSAT 05-03, accessed at: www.                  recycled material. Heifer explored this, but chose other                   sustainable options for their lot based on preference and
       htm.                                                                    budget.
107	                                                                    122	
       Cahill, T. et al, (2005), Stormwater Management with Porous             Wade, B., (2000), Putting the freeze on heat islands, Ameri­
       Pavements, Government Engineering, March-April 2005,                    can City & County, 115, 2, 30, page 2, Feb 2000.
       pp. 14-19, accessed at:           123	
                                                                               Calculated using the PaLATE model, a lifecycle assessment
                                                                               tool created to derive the environmental and economic
       New York State Department of Environmental Conservation,                effects of paved surfaces. Information on the PaLATE model
       (2007), New York State Stormwater Design Manual - Chapter               can be found at:
       9, accessed at:                     html.
109	                                                                    124	
       Knox County, Tennessee, (2007), Stormwater Management                   Mercury (Hg) emissions were modeled by PaLATE, but were
       Ordinance, Volume 2 (technical guidance), accessed at:                  not mentioned here because the emissions difference was                           negligible.
110                                                                     125
       Turfstone®, UNI Eco-Stone®, Grasspave2®, and Gravelpave2®               U.S. Office of Management and Budget, (2005), Draft 2005
111	                                                                           Report to Congress on the Costs and Benefits of Federal
       Brattebo, B. and Booth, D., (2003), Long-term stormwater
                                                                               Regulations, Appendix B and U.S. Office of Management
       quantity and quality performance of permeable pavement
                                                                               and Budget, Circular A-94: Guidelines and Discount Rates
       systems, Water Research, 37, 4368-4376, November 2003.
                                                                               for Benefit-Cost Analysis of Federal Programs, accessed at:
       Hinman, C., (2005), Low Impact Development Technical           on
       Guidance Manual for Puget Sound, Puget Sound Action                     January 10, 2007.
       Team, publication number PSAT 05-03, accessed at: www.
                                                                               It should be noted that the values shown here are based on
                                                                               national averages.
113	                                                                           The high end of this range represents values associated
       U.S. EPA, (2007), National Pollutant Discharge Elimination
                                                                               with avoided emissions in areas with severe air quality
       System (NPDES) – Porous Pavement Fact Sheet, accessed at:
                                                                               impairment, and are likely too high to apply to the Little­
                                                                               Rock area, which is in attainment with federal PM10 and SO2

                                                                                                                    Key Resources             56
       standards, as well as all other air quality standards. Query          Building Sciences, (2007), Whole Building Design Guide,
       of EPA Air Data, January 21, 2006:              accessed at:
       nonat.html?st~AR~Arkansas.                                     140	
                                                                             Florida Department of Environmental Protection, (2006),
       Sources for this case study include: McNally, C., et al,              Water Best Management Practices, Florida Green Lodging
       (2003), The University of Rhode Island’s Permeable Parking            Program, accessed at:
       Lots: A case Study of Alternative Pavement Materials, ac­             content/gr_h2o.htm.
       cessed at:           141
       PP.URICaseStudy.pdf; and the 2005 update to this docu­
       ment located at                  U.S. Department of Energy, (2006), Federal Energy Manage­
       index.htm.                                                            ment Program – Water Efficiency, accessed at: http://www1.
       URI also does not permit commercial and industrial vehicles
       on this lot because of groundwater contamination con­                 Ibid.
       cerns, and to avoid compaction of the pourous bituminous       144	
                                                                             Florida Department of Environmental Protection, (2006),
                                                                             Water Best Management Practices, Florida Green Lodging
       Potable water is defined by the US EPA as water suit­                  Program, accessed at:
       able for drinking or cooking purposes from both health                content/gr_h2o.htm.
       and aesthetic considerations. (Office of Environmental           145
       Information, (2007), Ecoview Glossary, accessed at: http://
                                                                      146                 San Mateo County, (2007), Recycle Works – Landscape
       id=291323&p_term_cd=TERMDIS).                                         Plantings, accessed at:­
129	                                                                         ing/sus_plantings.html.
       Romero, M. and Hostetler, M., (2007), Policies that Address
       Sustainable Landscaping Practices, Circular 1519, University          As with high-efficiency irrigation technology, developers
       of Florida, accessed at:               can also acquire LEED WE Credit-1.1 by recycling rainwater
130	                                                                         or using recycled wastewater to reduce potable water
       U.S. EPA, (2005), The Natural Landscaping Alternative:
                                                                             consumption by fifty percent over conventional means;
       An Annotated Slide Collection, from Green Landscaping:
                                                                             or through LEED WE Credit-1.2 by using only captured
       Greenacres Natural Landscaping Tool Kit, accessed at: www.
                                                                             rainwater or recycled water to eliminate all potable water
                                                                             use for site irrigation (except for initial watering of plants).
       San Mateo County, (2007), Recycle Works – Landscape                   National Institute of Building Sciences, (2007), Whole Build­
       Plantings, accessed at:­              ing Design Guide, accessed at
       ing/sus_plantings.html.                                        148	
                                                                             State of California Energy Commission, (2005), Califor­
       Pennsylvania Department of Environmental Protection,                  nia’s Water-Energy Relationship, CEC-700-2005-011-SF,
       (2006), Pennsylvania Stormwater Best Management                       accessed at:
       Practices Manual: Chapter 5 - Non Structural BMPs,                    CEC-700-2005-011/CEC-700-2005-011-SF.PDF.
       363-0300-002, accessed at:            149	
                                                                             Milwaukee Metropolitan Sewerage District, (2007), State
                                                                             of the Art Report Draft, accessed at:
       Illinois Conservation Foundation and Chicago Wilderness,       150	
                                                                             U.S. EPA, (2004), Conference Summary, Landscaping with
       (2005), Change Cost Perceptions: An Analysis of Conserva­
                                                                             Native Plants: Exploring the Environmental, Social and Eco­
       tion Development, accessed at:­
                                                                             nomic Benefits Conference December 6 - 7, 2004, accessed
       King County Department of Natural Resources (2007) Na­         151
       tive Plant Salvage Program, accessed at: http://dnr.metrokc.
       gov/wlr/pi/salopps.htm.                                               Ibid.
135	                                                                  153	
       City of Chicago, (2003), A Guide to Stormwater Best Man­              Muthukrishnan, S. et al, (2004), The Use of Best Manage­
       agement Practices, accessed at:                 ment Practices (BMPs) in Urban Watersheds, U.S. EPA,
       sources/Chicago%20GuideTo%20Stormwater%20BMPs.pdf.                    EPA/600/R-04/184, accessed at:
136	                                                                         NRMRL/pubs/600r04184/600r04184.pdf.
       U.S. Department of Energy, (2006), Federal Energy Manage­
       ment Program – Water Efficiency, accessed at: http://www1.              Ibid.                    155	
                                                                             U.S. EPA, (2004), Conference Summary, Landscaping with
       Ibid.                                                                 Native Plants: Exploring the Environmental, Social and Eco­
138	                                                                         nomic Benefits Conference December 6 - 7, 2004, accessed
       San Mateo County, (2007), Recycle Works – Landscape
       Plantings, accessed at:­
139	                                                                         Florida Department of Environmental Protection, (2006),
       By using high efficiency irrigation technology, developers
                                                                             Water Best Management Practices, Florida Green Lodging
       can acquire LEED Water-Efficiency (WE) Credit 1.1 if they
                                                                             Program, accessed at:
       reduce potable water consumption for irrigation by fifty
       percent over conventional means. In addition, they can also
       achieve LEED WE Credit 1.2 by not installing a permanent              U.S. Department of Energy, (2001), Greening Federal
       landscape irrigation system, which is the highest goal of             Facilities, second edition, accessed at:
       water efficient natural landscaping. National Institute of              fy01osti/29267.pdf.

                                                 Green Parking Lot Resource Guide—February 2008                                                 57
158	                                                                     176	
       U.S. EPA, (2004), Conference Summary, Landscaping with                   U.S. EPA, (2004), Conference Summary, Landscaping with
       Native Plants: Exploring the Environmental, Social and Eco­              Native Plants: Exploring the Environmental, Social and Eco­
       nomic Benefits Conference December 6 - 7, 2004, accessed                  nomic Benefits Conference December 6 - 7, 2004, accessed
       at:                       at:
       html.                                                                    html.
159	                                                                     177
       U.S. Department of Energy, (2001), Greening Federal                      Ibid.
       Facilities, second edition, accessed at:       178	
                                                                                Dunn, A. and Stoner, N., (2007), Green Light for Green
                                                                                Infrastructure, The Environmental Forum, May/June 2007,
       North Carolina Department of Environment and Natural                     reprinted by the Environmental Law Institute and accessed
       Resources, (2005), Water Efficiency: Water Management                      at: www.
       Options, Division of Pollution Prevention and Environmental       179	
                                                                                U.S. EPA, (2007), National Pollutant Discharge Elimination
       Assistance, accessed at:
                                                                                Systems (NPDES): Green Infrastructure, accessed at: http://
       U.S. EPA, (2003), Water-Efficient Landscaping, accessed at:                               180	
                                                                                U.S. EPA, (2007), National Pollutant Discharge Elimination
       U.S. EPA, (2007), Landscaping with Native Plants, accessed               System (NPDES): Green Infrastructure – General Informa­
       at:                          tion, accessed at:­
163	                                                                            structure/information.cfm
       U.S. Department of Energy, (2003), The Business Case for
       Sustainable Design in Federal Facilities – Appendix D, ac­               Ibid.
       cessed at:          182	
                                                                                Kloss, C. and Calarusse, C., (2006), Rooftops to Rivers: Green
                                                                                Strategies for Controlling Stormwater and Combined Sewer
       U.S. EPA, (2004), Conference Summary, Landscaping with                   Overflows, Natural Resources Defense Council, accessed at:
       Native Plants: Exploring the Environmental, Social and Eco­    
       nomic Benefits Conference December 6 - 7, 2004, accessed           183	
                                                                                U.S. EPA, (2004), Conference Summary, Landscaping with
                                                                                Native Plants: Exploring the Environmental, Social and Eco­
                                                                                nomic Benefits Conference December 6 - 7, 2004, accessed
       City of Chicago, (2003), A Guide to Stormwater Best Man­                 at:
       agement Practices, accessed at:                    html.
       sources/Chicago%20GuideTo%20Stormwater%20BMPs.pdf.                184	
                                                                                Kloss, C. and Calarusse, C., (2006), Rooftops to Rivers: Green
       U.S. EPA, (2004), Conference Summary, Landscaping with                   Strategies for Controlling Stormwater and Combined Sewer
       Native Plants: Exploring the Environmental, Social and Eco­              Overflows, Natural Resources Defense Council, accessed at:
       nomic Benefits Conference December 6 - 7, 2004, accessed        
       at:                185	
                                                                                U.S. EPA, Report to Congress: Impacts and Control of CSOs
                                                                                and SSOs, Office of Water, EPA-833-R-04-001, August 2004
       U.S. EPA, (1992), Cooling Our Communities,                               as cited in Kloss, C. and Calarusse, C., (2006), Rooftops to
       GPO#055-000-00371-8, January 1992, accessed at: www.                     Rivers: Green Strategies for Controlling Stormwater and, as cited in Pavement Busters Guide (2002), page                 Combined Sewer Overflows, Natural Resources Defense
       10, Victoria Transport Policy Institute.                                 Council, accessed at:
168	                                                                            rooftops/contents.asp.
       Wolf, K., (2004), Trees, Parking, and Green Law: Strategies for
       Sustainability, accessed at:                 U.S. EPA, (2007), Green Infrastructure Program - A report
       Resources/Library/Citation.2004-07-14.1757/file_name.                     evaluating the concept of a major storm water minimiza­
169	                                                                            tion program, utilizing green infrastructure and related
       U.S. Department of Energy, (2001), Greening Federal
                                                                                methods, prepared by Prepared by Metropolitan Sewer
       Facilities, second edition, accessed at:
                                                                                District of Greater Cincinnati et al, accessed at: www.msdgc.
       United Nations, (1993), Text of the Convention on Biological             Green_Report.pdf.
       Diversity, Article 2: Use of Terms, accessed at:     187	
                                                                                U.S. EPA, (2007), National Pollutant Discharge Elimination
                                                                                System: Green infrastructure—Case Studies, accessed at:
       U.S. EPA, (2004), Conference Summary, Landscaping with         
       Native Plants: Exploring the Environmental, Social and Eco­              casestudies.cfm#portland.
       nomic Benefits Conference December 6 - 7, 2004, accessed           188	
                                                                                Dunn, A. and Stoner, N., (2007), Green Light for Green
                                                                                Infrastructure, The Environmental Forum, May/June 2007,
                                                                                reprinted by the Environmental Law Institute and accessed
       Ibid.                                                                    at: www.
173	                                                                     189	
       Illinois Conservation Foundation and Chicago Wilderness,                 U.S. EPA, et al, (2007), Green Infrastructure Statement of
       (2005), Change Cost Perceptions: An Analysis of Conserva­                Intent, Stakeholder Statement of Support for Green Infra­
       tion Development, accessed at:­                     structure, accessed at:
       sources/Cost%20Analysis%20-%20Part%201%20-%20                            gi_supportstatement.pdf.
       Report%20-%20with%20Exec%20Summary.pdf.                           190	
                                                                                Grumbles, B.H., (2007), Memorandum from Benjamin H.
       Ibid.                                                                    Grumbles, USEPA Assistant Administrator on Water, to
175                                                                             USEPA Regional Administrators regarding Using Green
                                                                                Infrastructure to Protect Water Quality in Storm Water, CSO,
                                                                                Non-point Source and Other Water Programs, March 5,

                                                                                                                     Key Resources               58
191	                                                                 197	
       U.S. EPA, (2007), Green Infrastructure Program—A report              Arvidson, A.R., (2006), A Green Demonstration, Landscape
       evaluating the concept of a major storm water minimiza­              Architecture Magazine, September 2006.
       tion program, utilizing green infrastructure and related      198	
                                                                            City of Portland, Oregon, (2006), Green Streets Cross-Bureau
       methods, prepared by Metropolitan Sewer District of
                                                                            Team Report – Phase I, March 2006, accessed at: www.
       Greater Cincinnati et al, accessed at:
       pdf.                                                                 City of Portland, Oregon, (2006), Green Streets Resolution,
192	                                                                        accessed at:
       U.S. EPA, (2004), Conference Summary, Landscaping with
       Native Plants: Exploring the Environmental, Social and Eco­
       nomic Benefits Conference December 6–7, 2004, accessed                City of Portland, Oregon, (2006), Green Streets Cross-Bureau
       at:                   Team Report—Phase I, March 2006, accessed at: www.
193	                                                                 201	
       Center for Neighborhood Technology, (2007), Green Infra­             Water Environment Research Foundation, (2007), Portland
       structure Performance, accessed at:                     Oregon: Building a Nationally Recognized Program Through
       repository/BMP-Performance.pdf.                                      Innovation and Research, accessed as:
194	                                                                        livablecommunitires/studies_port_or.html.
       Dunn, A. and Stoner, N., (2007), Green Light for Green
       Infrastructure, The Environmental Forum, May/June 2007,              Ibid.
       reprinted by the Environmental Law Institute and accessed     203	
                                                                            City of Portland, Oregon, (2006), Green Streets Cross-Bureau
       at: www.
                                                                            Team Report—Phase I, March 2006, accessed at: www.
       Center for Neighborhood Technology, (2007), Green Infra­   
       structure Performance, accessed at:              204	
                                                                            Water Environment Research Foundation, (2007), Portland
                                                                            Oregon: Building a Nationally Recognized Program Through
       U.S. EPA, (2007), National Pollutant Discharge Elimina­              Innovation and Research, accessed as:
       tion System (NPDES): Environmental Benefits of Green                  livablecommunitires/studies_port_or.html.
       Infrastructure, accessed at:

                                                Green Parking Lot Resource Guide—February 2008                                             59

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