1

Managing Wet Weather with 

Green Infrastructure

Municipal Handbook

Green Infrastructure 

Retrofit Policies
Managing Wet Weather with Green Infrastructure 

Municipal Handbook 

Green Infrastructure Retrofit Policies 

prepared by 

Jennifer Bitting 

Christopher Kloss 

Low Impact Development Center 

The Municipal Handbook is a series of documents 

to help local officials implement green infrastructure in their communities.

December 2008 

EPA-833-F-08-008 

Front Cover Photos 

Top: rain garden; permeable pavers; rain barrel; 

planter; tree boxes. 

Large photo: bioretention and permeable 

concrete, Olympia WA 
3

Green Infrastructure Retrofit Policies 

Introduction

Existing development, especially in urbanized and urbanizing areas, is responsible for currently degraded 

water quality and stream conditions. Changes in land cover and the increased imperviousness of the urban 

environment have resulted in larger volumes of runoff traveling at faster velocities. This has caused 

serious streambank erosion and has compromised aquatic habitat. Many of these areas were developed 

without adequate stormwater controls and must be addressed if urban streams are to be restored and water 

quality is to be improved nationwide. It should be noted that most stormwater regulations are intended to 

limit the increases in pollution associated with new development, or to curb flooding, but do not 

specifically address the hydrologic modifications associated with runoff from existing development. 

Nationally, 40% of assessed waters fail to meet water quality standards and urban streams have tended to 

fare worse than the national averages.1

 USGS studies of urban streams find that concentrations of total 

phosphorus exceed EPA’s goal for nuisance growth in 70% of streams, insecticides are usually at a higher 

concentration than in agricultural areas, and fecal coliform bacteria commonly exceed recommended 

standards for water recreation.2 In addition, combined sewer systems in nearly 750 municipalities deliver 

850 billion gallons of untreated overflows to urban waters each year.3

Retrofits to stormwater infrastructure will be necessary to reduce runoff and pollution, but the capital 

investment is daunting. Upgrades to stormwater and combined sewer systems, like other utilities, are 

capital intensive projects. EPA estimates current wastewater infrastructure needs an investment in excess 

of $200 billion, with $10 billion needed for stormwater management and $60 billion needed for combined

sewer overflow (CSO) correction.4

 While this needed investment presents a significant economic burden, 

it also presents an opportunity to re-evaluate the most efficient way to invest in infrastructure and 

environmental programs. 

Using green infrastructure for urban stormwater retrofits can reduce stormwater pollution while 

simultaneously reducing the burden and demand on existing infrastructure. However, water quality and 

quantity benefits are not the only advantages green infrastructure has to offer. Green infrastructure 

enhances communities by bringing aspects of the natural environment into inhabited space. Trees provide 

shade, act as wind breaks and noise barriers, and improve air quality. In many instances, green 

infrastructure has been found to be less costly than or cost competitive with traditional infrastructure. 

Green infrastructure provides additional environmental and economic benefits for the investment rather

than traditional stormwater management approaches that literally bury the investments out of sight. The 

additional benefits that green infrastructure provides include: 

• Green infrastructure effectively counteracts urban heat island by substituting soils and 

vegetation for hard, heat absorbing materials common in urban areas, creating shade, and 

emitting water vapor. 

• Green roofs and other vegetation incorporated on and around buildings, help shade and insulate 

buildings from wide temperature swings, decreasing the energy needed for heating and cooling. 

• Green infrastructure improves air quality as vegetation absorbs gaseous air pollutants and 

adsorbs particulates. 

• Research indicates that property values increase when street trees are planted and vacant lots are 

greened, providing private benefits to homeowners, increased property tax revenue, and more 

livable communities. 

The distributed green infrastructure network is designed to limit the conversion of precipitation to runoff 

by capturing rainwater where it falls, managing stormwater at the surface, and maximizing soil and 

vegetation contact during treatment. This combination allows green infrastructure to reduce stormwater

volumes, peak flow rates, and pollutant concentrations. 
4

Traditional stormwater controls have focused almost exclusively on reducing pollution without 

addressing the increased volume of stormwater discharged from urbanized areas. The benefits gained 

from removing pollutants are often overshadowed by the magnitude of the runoff volume. Even with 

stormwater controls and high rates of pollutant removal, absent volume reductions, urban areas will 

contribute more pollution than pre-development conditions making it difficult to achieve water quality

standards. Table 1 highlights this condition with the familiar example of the runoff from a one-acre 

meadow and one-acre parking lot after one-inch of rain. 

Table 1. Runoff Volume and Pollutant Load from One-Acre Parking Lot with Treatment and 

Meadow for a One-Inch Rain Event.5, 6

Land Use Pollutant Concentration 

(mg/L) 

% 

Removal 

Effluent 

Concentration 

(mg/L) 

Runoff 

Volume 

(gal) 

Pollutant 

Load 

(lbs) 

Paved Parking Lot 

with Treatment 130 80 26 25,800 5.6 

Meadow 

TSS 

25 0 25 1,600 0.34 

Table 1 demonstrates that even when treatment measures are able to achieve pollutant concentrations 

similar to pre-development conditions, the large difference in runoff volume produces a pronounced 

increase in pollutant load from urbanized areas. And with the lack of any controls in many urban areas, 

the pollutant loadings are much greater than displayed in Table 1. Green infrastructure’s ability to reduce 

both stormwater volumes and pollutant concentrations is critical to reducing pollutant loads from urban 

areas and improving water quality. 

This paper will explore the policies and incentives that municipalities have used to facilitate the use of 

green infrastructure within their stormwater programs. While the benefits of green infrastructure are 

increasingly understood, incorporating green retrofits into municipal infrastructure has presented 

institutional and regulatory challenges. The solutions to overcome these barriers are often dependent upon 

the water quality objectives and technologies employed. The policies are presented in this paper by 

technology type, but often approaches used for one green infrastructure practice are applicable to another 

or there is overlap among goals and outcomes. 

Green Roof Retrofit Policy

There are two types of public policy currently in place concerning the implementation of green roofs for 

retrofit applications: incentives and regulations. Although many jurisdictions are currently using 

incentives alone in the early stages of garnering widespread municipal support for green roofs, these two 

policy approaches work well in tandem. An incentive program can initiate a green roof regulation by 

introducing the technology and its application on private property before implementing a mandate. 

A combination of both incentives and regulation has been effective in Basel-City, Switzerland. Their 

incentive program had good publicity and raised awareness of green roof benefits such as energy savings 

and biodiversity protection, issues that were important to the community. Consequently, their green roof 

regulations did not meet resistance.7
5

Incentives

A green roof can have up to twice the lifespan of a conventional roof, making the long-term cost of the 

two comparable.8 However, since the initial cost of a green roof is significant, a policy that focuses on 

alleviating that initial cost burden appears to be most successful. 

Subsidy

The most common way to reduce the initial cost burden is through a subsidy program. Subsidies are 

usually provided per square foot of green roof area, up to an established maximum amount or percent of

the total cost. For example, the City of Toronto’s Green Roof Incentive Pilot Program will fund $50 per 

square meter of green roof up to a maximum of $10,000 for single family homes and $100,000 for other 

building types (Canadian dollar values).9

The funding for subsidy programs often comes from stormwater fees collected by the municipality to 

mitigate for post-construction levels of runoff quantity and pollutants. By investing in green roofs, the 

municipality is eliminating runoff before it enters the municipal stormwater system. The use of public

money on private land is validated because of the reduced municipal facility cost, size, and maintenance 

burden. 

After the first year of Toronto’s Green Roofs Pilot Program, the incentive offered for building green roofs 

was found to not be high enough to attract broad interest.10 Consequently, the financial incentive was 

raised from $10 (CAD) to the current $50 (CAD) per square meter. However, this amount is more than 

the cost of the stormwater benefit to the city and alternative funding sources have to be found in order to 

sustain the program. Since green roofs also reduce energy use in buildings making more energy available 

for other users and delaying the need for capacity upgrades, Toronto is considering funding the Green 

Roof Incentives Program with energy conservation funds as well as stormwater management funds.11

Excerpt from the City of Toronto Green Roofs Pilot Program

Green Roof Incentive Pilot Program 

Program goals 

The Green Roof Incentive Pilot Program supports the City's stormwater plan known as the Wet Weather Flow 

Master Plan. The overall goal of the Green Roof Pilot Program is to encourage green roof construction in the City. 

In addition, the program will: 

• Result in the construction of a variety of green roof types which could be used for education and 

promotional purposes. 

• Provide an opportunity to showcase various green roof technologies and planting styles. 

• Provide a grant of $50 per square meter of eligible green roof area up to a maximum of $10,000 for single 

family homes and a maximum of $100,000 for all other property owners in the City of Toronto. 

Who is eligible 

Any private property owner in the City of Toronto with a water account with the City is eligible, regardless of 

building size and type, so long as the building is capable of supporting a green roof that meets the specifications 

and requirements. Each green roof applicant must demonstrate that the proposed green roof: 

• Has a continuous coverage of growing media over at least 50% of the roof footprint (roof area) of the

building. 

• Has a vegetation mix as opposed to a monoculture and a sustainable organic growing medium that 

replenishes nutrients and retains moisture. 

• Has a maximum slope of 10 percent. 

• Has a depth of at least 150 mm (6 inches) for a new building. The depth will permit greater flexibility in 

terms of the type and variety of vegetation that can be incorporated and will help ensure greater survival 

of plants (existing buildings with a lesser growing medium thickness may be considered for the pilot 

program if the applicant (or manufacturer) submits test data indicating the performance of the system with 

respect to water runoff coefficient and plant survival ability. 

• Is installed over heated spaces (non-heated spaces, such as underground garages will not be considered 

for the pilot program). 
6

Local market development is an additional benefit 

of financial incentives. As more property owners 

elect to build green roofs, the demand for local 

green roof services will increase and the cost of 

the technology will eventually decrease as a result

of a competitive market. This may eventually 

reduce or eliminate the need for a financial 

incentives program. 

Consultation

Lack of information about the site-specific costs, 

maintenance needs, and benefits of a green roof 

can discourage property owners considering 

retrofitting an existing roof. Providing a free 

consultation with a green roof professional can 

allow property owners who are interested in green 

roof retrofits to overcome initial uncertainty. 

Stuttgart, Germany has a financial incentives 

program, and also provides free consultations and 

informative brochures that detail benefits, weight,

waterproofing issues, and maintenance 

considerations.12

 

Fee Reduction

An incentive that can be used to ensure the longterm effectiveness of a green roof is a stormwater 

fee reduction. In areas where stormwater utility 

fees are in place, credit for reducing impervious 

area, and thereby runoff volume, can be given to property owners who install and maintain green roofs. In 

Minneapolis, Minnesota, 50% of the stormwater fee can be waived if the property owner can demonstrate 

that the runoff from a 10-year, 24-hour storm event can be managed on site. If a property owner can 

demonstrate that the runoff from a 100-year, 24-hour storm event can be managed on site, the entire 

stormwater fee is waived.13

Regulation

There are very few cities in North America that directly mandate the use of green roofs. The City of 

Chicago has requirements in place to mitigate urban heat island effects by addressing the solar reflectance 

of roofs. These requirements set a minimum reflectance for low and medium sloped roofs. However, 

green roofs are exempt. By installing a green roof, the solar reflectance requirements are met. 

Excerpt from the City of Minneapolis

Stormwater Utility Fee 

Applying for Stormwater Quantity Credits 

Property owners can apply for either the “Standard 

Quantity Reduction Credit” or the “Additional Quantity 

Reduction Credit.” 

• Standard Quantity Reduction Credit. The 

Standard Quantity Reduction Credit is a 50 

percent credit on a property’s stormwater fee. 

The “Standard Quantity” credit is based on a 

property’s stormwater quantity management 

tools/practices being able to retain the 10-year, 

24-hour type II SCS storm event to predeveloped conditions. To qualify for this credit, 

the property owner must demonstrate that 

stormwater from the property is controlled with 

an on-site constructed stormwater quantity 

management tool/practice (BMP). 

• Additional Quantity Reduction Credit. The 

Additional Quantity Reduction Credit is a 100 

percent credit on a property’s stormwater fee. 

To be eligible for the “Additional Quantity” 

credit, a property’s stormwater quantity 

management tools/practices must be able to 

retain the 100-year, 24-hour type II SCS storm 

event to pre-developed conditions. To qualify 

for this credit, the property owner must 

demonstrate that stormwater from the property 

is controlled with an on-site constructed 

stormwater quantity management tool/practice 

(BMP). 
7

Downspout and Impervious Cover Disconnection Retrofit Policy

There are various reasons why municipalities pursue a downspout or impervious cover disconnection 

program. Disconnection refers to the practice of breaking the direct link between impervious areas such as 

roofs or paved surfaces and the storm or combined sewer system. Disconnection can reduce combined 

sewer system overflows; reduce potable water demand when the runoff from roofs is used for applications 

such as landscape irrigation and toilet flushing; recharge ground water, helping to restore the natural 

hydrologic cycle; reduce stormwater discharges to waterways; and reduce or eliminate the need for large, 

municipally owned stormwater management facilities. 

Using a combination of incentives, compliance assistance and regulations seems to be very effective at

obtaining a high rate of retrofit disconnection. The regulation sets the timeframe for compliance. 

Incentives and assistance programs make compliance easily attainable for the target audience. 

Incentives 

Fast-track Project Review 

Philadelphia has implemented a fast track review process for redevelopment projects with 95% or more of 

the impervious area disconnected from the combined or separate storm sewer. The Philadelphia Water 

Department will review the stormwater management portion of a project submittal within five business 

days for projects that qualify for the Green Project Review.14 This is a low or no cost program for the City 

and it provides the project with a time savings that usually also translates into a financial savings. Because 

of the low cost of implementing this program, it is not subject to budget cuts or lapses in grant funding, 

and is not likely to be met with tax payer opposition. 

Excerpt from the City of Chicago Energy Conservation Code Revised January 9, 2003.

303 URBAN HEAT ISLANDS 

18-13-303.1 Roof Reflectance. To minimize the undesirable “urban heat islands effect,” low and medium 

sloped roofs shall comply with the following requirements when tested in accordance with ASTM E408. The 

roof surface of low sloped roofs (2:12 or less) shall have an initial solar reflectance greater than or equal to 

0.65 and shall maintain a reflectance equal to greater than 0.50 for three years after installation. Mediumsloped roofs (greater than 2:12 and less than or equal to 5:12) shall have a solar reflectance equal to or greater 

than 0.15 initially and for three years after installation. Minimum emissivity shall be 0.9.

Exception: Roofs or portions of roofs that utilize photovoltaic, solar thermal or roof garden systems. 

Urban heat island provisions. The reflectance and emittance requirements of Sections 18-13-303.1 through 

18-13-303.2.1 are intended to minimize the urban heat island effect, as defined in Section 18-13-202, 

Definitions. 

1. The portion of the roof that is covered by a rooftop deck covering 1/3 or less of the aggregate area of the 

roof, or a rooftop garden, or a green roof, is exempted from the requirements of this section. 

2. An area including and adjacent to rooftop photovoltaic and solar thermal equipment, totaling not more than 

three times the area that is covered with such equipment, may be exempted from the requirements of this 

section. 

18-13-303.2 Solar Reflectance. All roof exterior surfaces shall have a minimum solar reflectance as specified 

in 18-13-303.2.1 when tested in accordance with ASTM E903, ASTM E1918 or by testing with a portable 

reflectometer at near ambient conditions. 

18-13-303.2.1 Roofing materials used in roofs with slopes of 0 in 12 to 2 in 12 shall meet the following 

requirements: 

1. Roofs installed prior to and including 12/31/08 shall have a minimum solar reflectance, both initial and 

weathered, of 0.25. 

2. Roofs installed after 12/31/08 shall utilize roofing products that meet or exceed the minimum criteria to 

qualify for an Energy Star label as designated by the USEPA Energy Star program. 
8

Stormwater Utility Fee Discount 

Portland, Oregon uses a stormwater utility fee discount as an incentive to encourage residential and 

commercial property owners to manage stormwater on site. Property owners with disconnected 

downspouts are able to apply for fee discounts. For example, residential property owners pay a monthly

stormwater charge of $17.33. A discount of $6.07 applies to properties with disconnected downspouts, 

reducing the monthly charge to $11.26. A Residential Discount Calculator and a Commercial Discount 

Calculator can be found on the Clean River Rewards website.15

Compliance Assistance 

The cities of Bremerton, Washington and Portland, Oregon elected to implement similar compliance 

assistance programs to achieve retrofit disconnection. 

Reimbursement 

Bremerton developed brochures and self-help videos describing how to separate roof drain leaders from 

the sewer system and offered free site assessments and technical assistance. In addition, Bremerton 

simplified their permit process and eliminated the fees for work done to disconnect downspouts. They 

also reimbursed residential property owners ($25 to $500) for materials used in the disconnection effort.16

 

As a result, 417,000 square feet of impervious area were disconnected. The program lasted 34 months and 

cost $270,000. The city obtained a grant for $150,000 from Washington Department of Ecology, and used 

$120,000 of its stormwater and wastewater utility funds. The use of wastewater utility funds was easily 

justified because the disconnection project reduced combined sewer overflows by 99%; the grant money 

was earmarked for public projects so the utility money was directed towards private property.17 The 

program also reduced, and in some situations eliminated, the need for large scale, municipally owned 

stormwater management facilities, further justifying the use of stormwater and wastewater utility funds. 

Bremerton estimates that the cost per gallon of stormwater removed was $1.04 for a one inch rain event, 

whereas the cost of municipally owned stormwater management facilities is $5-$10 per gallon.18

Free Disconnection 

Portland, Oregon implemented a similar compliance assistance program that offered reimbursement of 

$53 per disconnected downspout for property owners wanting to disconnect their own downspouts. 

Alternatively, property owners could apply to the City to do the disconnection work for free.19 This 

flexibility provides compensation for property owners who want to do the work themselves, and free 

disconnection service for those who can not or do not want to. Portland’s program is responsible for 

City of Philadelphia Stormwater Management Guidance Manual Version 2.0

4.2.1 Green Project Review 

PWD (Philadelphia Water Department) offers a Green Project Review for redevelopment projects that are able to 

disconnect 95% or more of the impervious area in the post construction condition. When performing a Green 

Project Review, PWD is committed to providing review of the stormwater management component within 5 

business days of receipt of a complete project submittal. A Green Project Review may not necessarily include 

review of additional elements outside stormwater management such as Private Cost or Act 537 review. To be 

eligible for a Green Project Review a project must meet the following criteria:

• Project is redevelopment; 

• 95% or more of the post construction impervious area is disconnected; 

• Project may not adversely impact or further exacerbate rates and quality of runoff contributing to public 

infrastructure; and 

• Public Health and Safety issues may preclude a project from a Green Project Review. 

The submittee MUST identify their project as eligible for a Green Project Review in the letter of transmittal sent 

with the technical submittal. PWD may not be able to provide review comments within 5 business days without 

this notification. 
9

successfully disconnecting over 50,000 downspouts and removing 1.5 billion gallons of stormwater a year 

from the combined sewer system.20

 

Regulation

Both the Bremerton and Portland programs were successful in part because they required that downspouts

be disconnected by a specified future date. Portland’s regulations require that downspouts be 

disconnected one year after notification from the City.21 This provides the incentive for property owners 

to participate in the compliance assistance program. In Bremerton, the regulations required that property 

owners disconnect their downspouts by 2005.22 Their compliance assistance program began around 2001 

giving property owners time to become informed about the issue, get involved in the compliance 

assistance program, and comply with the regulation before the disconnection requirement date. 

Portland City Code

Chapter 17.37.050 Disconnection Reimbursement in Voluntary and Mandatory Program Areas 

(Amended by Ordinance No. 170113, effective May 15, 1996.) Disconnection reimbursement will be paid in the 

following manner: 

A. Disconnection reimbursement will be made for the least expensive method of disconnection that will be 

effective, as determined by the Director. Reimbursements will not be processed until the new disposal 

system has been inspected and approved. Owners will not be reimbursed for downspouts disconnected prior 

to receiving official notification from the Downspout Disconnection Program that they are eligible for

downspout disconnection reimbursement. Reimbursement will only be provided within the target areas 

identified in section 17.37.030 B.1. and 2. 

B. Downspout disconnection to surface systems will be reimbursed as follows: 

1. Owners who complete the disconnection work themselves or use their own contractor and receive a 

satisfactory inspection will be compensated according to the following unit costs per downspout: 

a. $25 per downspout disconnected for supplies; 

b. $13 per downspout for time and effort; 

c. $15 per downspout for landscaping and miscellaneous; 

Owners who receive free supplies from the City for their disconnection work will not receive the $25 

amount for supplies. 

Portland City Code

Chapter 17.37.030 Establishment of Downspout Disconnection Program 

B.3. Owners of eligible property located in mandatory program areas are required to disconnect their 

downspouts within one year following written notice from the City. For purposes of this section, notice shall be 

deemed to have been received upon the mailing of said notice by first class mail or upon delivery of the notice 

in person. 

Chapter 17.37.090 Enforcement Charges 

(Added by Ordinance No. 170113, effective May 15, 1996.) In the event that the City needs to enforce the 

terms of the Code Hearings Officer’s order referred to in Section 17.37.080, an administration fee of $300 for 

each occurrence shall be made a lien on the property in accordance with the provisions of Chapter 22.06. 
10

Permeable Pavement Retrofit Policy

With so many paved surfaces in the urban environment, there are plenty of opportunities to retrofit 

sidewalks, driveways, parking lots, plazas, roads, and alleys with permeable materials. Paved surfaces fall 

into two categories from a retrofit policy perspective: paved surfaces on private property and publicly 

owned paved surfaces. 

Public Property Retrofit

Publicly owned paved surfaces account for a large portion of the impermeable cover in urban areas. The

City of Chicago, for example, has over 1,900 miles of alleys. Because many of these alleys were not built 

with connections to the combined or storm sewer system, stormwater pools on paved surfaces, often 

flooding nearby garages and basements.23 

Bremerton Municipal Code Title 15.04.130

ELIMINATION OF IMPROPER STORMWATER INFLOW TO THE WASTEWATER SYSTEM. 

(a) Purpose. 

The purpose of this section is to significantly reduce improper stormwater inflow to the wastewater 

system in order to eliminate or reduce instances of combined sewer overflow events and 

surcharged sanitary sewers due to the improper inflows, which are detrimental to public health and 

welfare; and to maximize efficient operation of the wastewater collection system and treatment 

plant. 

(b) Disconnection Required by 2005. 

Disconnection of all improper stormwater inflow to the wastewater system shall be made by January 

1, 2005, unless continued connection is authorized by the Director where no practicable alternative 

for elimination of the improper stormwater inflow is available. 

(c) Director’s Authority to Order Early Disconnection. 

(1) Purpose. The Director has the authority to order the disconnection of improper stormwater 

inflow to the wastewater system prior to January 1, 2005, where that disconnection is 

necessary to meet combined sewer overflow reduction plans and for elimination of sanitary 

sewer surcharging. The Order of Early Disconnection will generally be in target areas as 

defined elsewhere in this section. 

(2) Notice. Notice of a Director’s Order for Early Disconnection will be provided in writing. The 

notice will establish an effective date by which the improper stormwater inflow shall be 

discontinued. The effective date shall be no sooner than ninety (90) days from the date of the 

letter. The effective date may be extended in writing by the Director. 

(d) Target Areas. 

The Director may identify target areas within the wastewater service area (sewer or storm drainage 

basins or subbasins) which have the highest priority for reduction of improper stormwater inflow to 

the wastewater system based upon combined sewer overflow events and sanitary sewer surcharge 

problems. 

The Chicago Green Alley Handbook

About the Green Alley Program 

While one solution to this problem is to install expensive connections to the City sewer system, the Green Alley 

Program also looks at other more sustainable solutions. In particular, where soil conditions are appropriate, 

water is allowed to infiltrate into the soils through permeable pavement or infiltration basins, instead of being 

directed into the sewer system or onto adjacent property. This not only solves a persistent problem, but it also 

provides an environmental benefit by cleaning and recharging the ground water. Furthermore, by not sending 

additional water to the combined sewer system a green alley can help alleviate basement and other flooding 

issues. 
11

Philadelphia Code § 14-1603.2. Environmental Controls for the 

Wissahickon Watershed 

 (4) Special Environmental Controls. The following special 

environmental controls are imposed (in addition to any applicable 

provisions of Section 1603.1) to regulate: setbacks from water 

courses, construction and earth moving activity on slopes, 

impervious cover, and, earth moving plans. 

(a) Setbacks from Water Courses Within the Watershed. There 

shall be no new impervious ground cover constructed or 

erected within 200 feet of the bank of a surface water body or 

within 50 feet of the center line of a swale within the Watershed 

(b) .... 

(c) Impervious Coverage. 

(.1) Basic Impervious Coverage. No building, paving, street or 

other impervious ground cover shall be constructed or 

placed on any property within the Watershed in excess of 

the requirements of the following categories as designated 

on Map "B" cited in Paragraph (4)(c)(.4): 

Category 1: There shall be no impervious ground coverage 

in excess of twenty (20) percent of the lot area or

subdivision. 

Category 2: There shall be no impervious ground coverage 

in excess of twenty-seven (27) percent of the lot area or 

subdivision. 

Category 3: There shall be no impervious ground coverage 

in excess of thirty-five (35) percent of the lot area or 

subdivision. 

Category 4: There shall be no impervious ground coverage 

in excess of forty-five (45) percent of the lot area or 

subdivision. 

Category 5: There shall be no percentage limitation of 

impervious ground coverage on land deemed to be 

developed or otherwise disturbed from its natural state, 

provided that parcels in excess of one-half acre may be 

further developed only as follows: 

(.a) The increased surface water runoff leaving the site 

shall not adversely affect adjacent property. 

(.b) The method of handling runoff on the site shall be in 

accord with sound engineering practices and shall not 

significantly accelerate on-site erosion. 

(.c) Such development shall not significantly diminish the 

infiltration capacity of the site. 

In 2006, Chicago piloted the Green 

Alley Program using permeable 

pavers, permeable concrete, and 

permeable asphalt to manage 

stormwater and recharge 

groundwater. Approximately 20 

alleys are resurfaced each year. 

Costs vary depending on material 

use, soil type, and size of the paved 

area. The sometimes higher cost of 

construction is offset by the 

avoided costs of maintenance and 

sewer improvements that would 

have been needed if the alleys were 

redesigned and resurfaced with 

impermeable pavement. In 

addition, the cost of alternative 

paving materials is decreasing as 

they become more common. The 

2008 cost of permeable concrete in 

Chicago is about $100 less per 

cubic yard than it was when the 

program began in 2006.24

In addition to water quality and 

quantity benefits, the use of light 

colored pavers and concrete 

reduces both the urban heat island 

effect and smog levels, improving 

outdoor air quality. The program 

also uses recycled materials, 

reducing the burden on landfills 

and conserving natural resources. 

For these reasons, the Green Alley 

Program was given the Chicago 

Innovation Award in 2007, 

sponsored by the Chicago SunTimes and Kuczmarski & 

Associates.25 

Private Property Retrofit

As Chicago “greens” its alleys in 

the public right-of-way, it invites 

residents to participate in 

“greening” the City by retrofitting 

their properties through The 

Chicago Green Alley Handbook. 

The handbook describes the environmental benefits of recycling, composting, planting trees, and using 

native landscaping. It also explains the benefits, costs and uses of rain gardens, rain barrels, permeable 

pavement and green roofs. The American Society of Landscape Architects gave the handbook a 2007 

Communications Honor Award for its clear and user-friendly content and graphics. 
12

As residents experience environmental 

improvements in their neighborhood, 

awareness increases. In addition, exposure to 

stormwater management increases the 

likelihood that residents will consider the use 

of other complementary practices such as 

rain barrels and rain gardens on their 

property. 

While Chicago has taken a “lead by 

example” approach to private property 

retrofits, Philadelphia requires limited 

imperviousness by way of local code. 

Property owners in the Wissahickon 

Watershed are required to meet impervious 

ground cover percentage maximums based 

on location. Since impervious cover 

includes buildings and pavement, the 

requirement acts as an incentive to reduce impervious cover through whatever means work best for the 

site. For example, a property owner may install permeable pavement if new paved surfaces are desired, or 

retrofit impermeable paved surfaces with permeable pavement in order to increase building size. The code 

allows for additional impervious coverage if stormwater is managed such that the infiltration capacity of 

the site is not diminished and runoff leaving the property does not have negative impacts off site. Because 

Philadelphia’s impervious coverage regulation does not specify the manner of compliance, it leaves room 

for flexibility and creative solutions while achieving the desired environmental performance. 

Philadelphia Code § 14-1603.2.(4)

Environmental Controls for the Wissahickon Watershed 

 (.1) ... 

 (.2) Additional Impervious Coverage. Additional impervious coverage shall be permitted by the City 

Planning Commission, after review and comments by the Water Department and other appropriate City 

agencies according to the standards and regulations adopted by the Commission and the Water 

Department. Such standards and regulations shall assure that: 

(.a) Storm water leaving the property shall be substantially similar in effect to that under the basic

impervious coverage limitation. 

(.b) Countermeasures shall not require excessive or significant maintenance. 

(.c) Design of countermeasures shall take account of storm water runoff that enters the property from 

adjacent land. 

(.d) The method of handling runoff on the site shall be in accord with sound engineering practices 

and shall not significantly accelerate on-site erosion. 

(.e) Such development shall not significantly diminish the infiltration capacity of the site. 

(.3) ... 

(.4) The map designated as "Impervious Coverage Categories" shall define the areas where the 

restrictions imposed under this Section shall apply and is made part of this ordinance (Map "B"). Where a 

parcel crosses category lines, each portion of the parcel shall be governed by the controls applicable to 

that portion. 

Chicago Green Alley.

Photo: Chicago Department of Transportation 
13

Bioretention Retrofit Policy

Bioretention retrofit applications fit largely into two categories: those aimed at treating runoff from 

private property such as roofs and driveways, and those focused on treating runoff from the public rightof-way such as roadways. The policy approaches are different based on the constraints and opportunities 

of each. Policies governing public right-of-ways tend to be in the form of regulation and policies used for 

private property more often takes the form of incentives. 

When implementing bioretention in the right-of-way, the constraint is most often space. The advantages

are easy access and adequate authority. So while a narrow, linear space may be difficult to retrofit, a 

municipality usually has ample access, both physically and legally, to the property. Bioretention practices, 

such as rain gardens on private property usually have fewer space limitations. However, gaining access to 

build or maintain rain gardens on private property is a constraint. 

Public Property Runoff Retrofit 

Public Right-of-Way Retrofits 

The Green Street Policy adopted in Portland, Oregon defines a “Green Street” as one that manages 

stormwater on site through the use of vegetated practices that provide water quality benefit and 

infiltration capacity. The policy requires that infrastructure projects incorporate these practices or be 

subject to an off-site project or off-site management fee requirement.26 

Portland’s Green Streets have been successful in many respects. 

The SW 12th Avenue retrofit project that introduced bioretention 

planter boxes into the landscaping strip between the sidewalk and 

the street, manages 180,000 gallons of runoff annually. The 

planters reduce the peak flow of a 25-year storm event by 70%.27. 

And at a cost of only $30,000 for the construction of the SW 12th

Avenue bioretention planters, the project demonstrates a costeffective solution. For these reasons, the American Society of 

Landscape Architects awarded the project the General Design 

Award of Honor as part of the 2006 Professional Awards.28

 

Using Easements 

Burnsville, Minnesota solved a similar problem of managing road 

runoff in a slightly different way. Lacking space in the right-ofway to implement bioretention practices, Burnsville launched a 

one month long public outreach campaign in an effort to get 

residents involved in the solution. Eighty-five percent of the 

residents agreed to participate in the rain garden retrofit project 

and allow the city to build rain gardens on the edge of their 

property to treat road runoff. The city obtained an $117,000 grant 

from the Metropolitan Council and contributed $30,000 of the 

City’s funds to build the rain gardens. Each rain garden cost $7,500: $500 for plants, $8.00/square foot for 

construction, and $4.50/square foot for education, design and construction supervision. The City has 

easements to maintain the rain gardens, which have been successful at reducing runoff by 90%.29

Portland Streetside Infiltration Planters.

Photo: Martina Frey. 
14

Private Property Runoff Retrofit 

Grant Program 

In an effort to protect Lake Michigan and increase the number of rain gardens in Milwaukee County, the

Milwaukee Metropolitan Sewerage District launched the Lake Michigan Rain Gardens Initiative. Grants 

are offered to property owners who are interested in planting their own rain garden. Grantees receive 

appropriate plants at a “two for one” discounted price. Applicants apply in January and, if awarded the 

grant, pick up their plants in June. An additional incentive is available for those who provide the total 

square footage of their roof, number of downspouts, and number of downspouts to be redirected. Their 

application is fast-tracked and they may be awarded early grant approval.30

This program not only encourages the creation of more rain gardens by reducing the cost to homeowners,

but also provides a useful mechanism for tracking the size of rain gardens and the amount of impervious 

area that is disconnected within the watershed. 

City of Portland, Oregon

Green Streets Policy 

Goal: City of Portland will promote and incorporate the use of green street facilities in public and private

development. 

City elected officials and staff will: 

1. Infrastructure Projects in the Right of Way: 

a. Incorporate green street facilities into all City of Portland funded development, redevelopment or 

enhancement projects as required by the City’s September 2004 (or updated) Stormwater 

Management Manual. Maintain these facilities according to the May 2006 (or updated) Green 

Streets Maintenance Policy. 

 If a green street facility (infiltrating or flow through) is not incorporated into the Infrastructure 

Project, or only partial management is achieved, then an off site project or off site management 

fee will be required. 

b. Any City of Portland funded development, redevelopment, or enhancement project, that does not 

trigger the Stormwater Manual but requires a street opening permit or occurs in the right of way, 

shall pay into a “% for Green” Street fund. The amount shall be 1% of the construction costs for 

the project. 

c. ... 

d. ... 

e. Develop standards and incentives (such as financial and technical resources, or facilitated permit 

review) for Green Streets projects that can be permitted and implemented by the private sector. 

These standards and incentives should be designed to encourage incorporation of green street 

facilities into private development, redevelopment, and enhancement projects. 

Findings 

A “Green Street”: 

• Handles stormwater on site through use of vegetated facilities; 

• Provides water quality benefits and replenishes groundwater (if an infiltration facility); 

• Creates attractive streetscapes that enhance neighborhood livability by enhancing the pedestrian 

environment and introducing park-like elements into neighborhoods; 

• Serves as an urban greenway segment that connects neighborhoods, parks, recreation facilities, 

schools, mainstreets, and wildlife habitats; and 

• Meets broader community goals by providing pedestrian and where appropriate bicycle access. 
15

Voluntary Offset Program

The Mt. Airy Rain Catchers program is a pilot project administered by U.S. EPA as part of an effort to

better understand the effectiveness of incentive programs. The objective of this voluntary offset program 

is to provide the largest benefit to the environment for the least amount of money spent. Participation in 

this unique program is voluntary and the offset (monetary compensation) received is determined by the 

individual property owner. 

The pilot program is being conducted in the Shepherd Creek Watershed of Cincinnati, Ohio. Since 

residential roofs and driveways account for 50% to 72% of the total impervious area in the relevant 

subwatersheds, rain barrels and rain gardens are the desired solution.31 Using an auction-based method, 

property owners place a bid for a rain garden or rain barrels to be installed on their property for free, and a 

dollar value they would like to be compensated for accepting these practices on their property. The bids 

are weighted according to cost, soils, and percent imperviousness of the site. Then the bids are ranked 

according to least cost and largest environmental benefit, and projects are awarded until available money 

is expended. In the summer of 2007, 50 rain gardens and 101 rain barrels were installed. They will be 

maintained for the property owner until 2010. Homeowners received an owner’s manual and will 

continue to receive quarterly emails during the establishment phase explaining maintenance protocols. 

This helps the homeowners become familiar with the activities they will become responsible for in 

2010.32 The program also has a user-friendly web page that keeps residents up to date by providing 

seasonally appropriate information. 

The program held a second auction in May 2008 followed by installation of the second phase of rain 

barrels and rain gardens. Most applicants did not request monetary compensation in exchange for theses

practices being installed on their property.33 The program has been successful in implementing rain 

barrels and rain gardens on private property at a low cost. 

Excerpt from the Milwaukee Metropolitan Sewerage District

Rain Garden Grant Information 

WHAT DOES THE GRANT PROVIDE? 

Grants will be awarded in the form of plants for your rain garden. For every 2.5 inch plant purchased at $3.60, 

grantees will receive a second plant for free, about a 50% discount compared to retail prices. The number of 

plants required is typically one per square foot of rain garden installed. 

EXAMPLE: the application is for a 10 x 10 foot rain garden, or 100 square feet. The number of plants needed 

is 100. The applicant orders 50 plants from GMF at a price of $3.60 each. The grantee receives 100 plants 

and pays $180.00. 

There are no cash awards. 

Costs for planning, design and construction of the rain garden are not grant eligible. 
16

Green Lot Retrofit Policy

Part of the difficulty in implementing green infrastructure practices in dense urban environments is 

finding the space and having the influence to make changes in a static built environment. One way around 

this dilemma is the conversion of vacant lots into “Green Lots.” Green Lots are vacant or abandoned lots 

that have had debris and paved surfaces removed and vegetation and trees added to deliver economic, 

social, and environmental benefits. 

Vacant lots can attract dumping, harbor toxic chemicals, depress property values, and attract criminal

activity.34 In contrast, Green Lots can increase property values, reduce urban heat island effect, improve 

air quality, provide habitat for small wildlife, increase infiltration, and recharge groundwater. 

Vacant Lot Stabilization

Philadelphia began the process of vacant lot transformation in 1995 when the Pennsylvania Horticultural 

Society (PHS) partnered with the New Kensington Community Development Corporation to address the 

1,100 parcels of abandoned land in the New Kensington neighborhood. The strategies included stabilizing 

vacant lots with grass, trees, and wood fencing; creating community gardens; planting trees; renovating 

parks; and transferring vacant lots to adjacent homeowners for private use. Funded by the City’s Office of 

Housing and Community Development, with support from the Pew Charitable trusts and the William 

Penn Foundation, from 1995 through 2002, 480 new trees were planted, 145 side yards were settled, 217 

lots were stabilized, and 15 community 

gardens were created.35 

While the intangible benefits can often be 

hard to quantify, a study done by the 

Wharton School of the University of 

Pennsylvania evaluated the economic value 

of Philadelphia’s Green Lot pilot project in 

New Kensington. The Determinants of 

Neighborhood Transformation in 

Philadelphia: Identification and Analysis—

The New Kensington Pilot Study by 

Professor Susan Wachter found that Green 

Lots increased adjacent property values by as 

much as 30%. Tree plantings increased the 

collective value of property in the 

community by $4 million and lot 

improvements by $12 million. In addition, 

Excerpt from the Mt. Airy Rain Catchers Brochure 

U.S. EPA is offering Mt. Airy homeowners a free rain garden and rain barrel! 

U.S. EPA is sponsoring a limited number of rain gardens and rain barrels in the Mt. Airy neighborhood.

Interested households must bid in an auction to receive them. Houses will be chosen based on lowest bids 

coupled with some environmental factors. 

Bid forms will be coming in the mail next week. Send in bid-forms early! Put in a low bid to increase your 

chances of receiving a free rain garden and/or rain barrel. Winning households will receive their bid 

amount as a one-time payment after the installation is complete. U.S. EPA’s contractor Tetra Tech, Inc., and 

its partner Horticultural Management, Inc., will install and maintain the gardens and barrels for three years. 

This unique opportunity is a one-time offer only for Mt. Airy homeowners in the spring of 2007. During this 

summer and for the next three summers, U.S. EPA will monitor local streams for changes in runoff quantity 

and water quality resulting from the combined effects of individual rain gardens and rain barrels. 

Visit the model rain garden planted at the bottom

Excerpt from the Vacant Land Management Pennsylvania 

Horticultural Society 

There are two basic ways in which the City contracts with 

Philadelphia Green to revitalize vacant spaces. The first is 

known as the Vacant Land Stabilization Program. 

Philadelphia Green begins stabilization by cleaning and 

mowing the grounds, laying topsoil, planting seeds, and 

adorning the area with new trees and fencing. In the past six 

years, nearly 4 million square feet of land have undergone 

this treatment and continue to receive care. 

The second approach is a project called Community 

LandCare, in which vacant land receives routine cleaning and 

mowing, but isn’t refurbished with topsoil, trees, or fencing. 

Nine community groups oversee the maintenance of vacant 

land in 16 Philadelphia neighborhoods. Currently 4 million 

square feet are regularly cleaned through this program. 
17

the more desirable the neighborhood becomes, 

the more people will move in to the 

community, providing a higher tax base for 

the City.36

Concerns about how to keep the lots clean 

remained after the initial effort to transform 

vacant properties into Green Lots. A 

maintenance program was established by 

hiring and training community residents. This 

not only provides local jobs, but also provides 

informal community education as employees 

tell neighbors about their work. 

Before: Lot at 2300 North 3rd Street 

Green Lot, Philadelphia, PA. 

Photo: The Pennsylvania Horticultural Society 

After: Lot at 2300 North 3rd Street 

Green Lot, Philadelphia, PA. 

Photo: The Pennsylvania Horticultural Society

Before and after conditions of a lot in Philadelphia 

treated under the Vacant Land Stabilization program. 

Photo: Cooperative Conservation America. 

Excerpt from the article “Seeing Green: Study Finds 

Greening is a Good Investment” on the Pennsylvania 

Horticultural Society webpage (taken July 7, 2008) 

Key Findings of the Wharton School Study 

• Cleaning and greening of vacant lots can increase 

adjacent property values by as much as 30%. 

• Planting a tree within 50 feet of a house can 

increase its value by about 9%. 

• Location of a house within 1/4 mile from a park 

increased values by 10%. 

• Neighborhood blocks with higher concentrations of 

unmanaged vacant lots displayed lower house 

prices, about 18%. 
18

Stormwater Offsets

The Maryland Chesapeake and Atlantic Coastal Bays Critical Area 10% Rule Guidance Manual allows 

abandoned lots to be converted to Green Lots, and set aside in perpetuity as mitigation for development 

projects elsewhere in the watershed that can not treat their stormwater on site. The Manual defines an

offset as “structures or actions that compensate for undesirable impacts”37 and lists four options, one of 

which is reducing the imperviousness of an existing property. This means that as compensation for adding 

impervious area elsewhere in the watershed, an abandoned lot can be restored to a Green Lot by removing 

impermeable pavement and revegetating the site, returning it to its natural hydrologic function within the 

watershed. The Green Lot remains a permanent open space. Green Lots provide a creative way to use 

abandoned properties to restore infiltration rates in the watershed and address urban runoff quantity and 

quality. 

Conclusions and Recommendations

Regardless of whether a community expects high rates of growth in the future or very little growth, 

existing development and its impervious surfaces will continue to dominate water quality and quantity 

problems in urban areas. Just as green infrastructure approaches should be pivotal components of all new 

and redevelopment, policies that focus on retrofitting the built environment with green infrastructure

should be a major element in any community’s plans for addressing urban stormwater challenges. 

Because green infrastructure provides benefits in many arenas, such as climate change, air quality, water 

quality and quantity, urban heat island effect reduction, and energy conservation, creative solutions can be 

found through cross-disciplinary partnerships. As organizations with different focuses come together to 

resolve their concerns through a common solution, funding and other resources can be leveraged to 

accomplish multiple goals. 

Two common themes seem to arise from successful green infrastructure retrofit policy: removing 

obstacles and creating incentives. As demonstrated by the examples discussed in this paper, when 

selecting a retrofit policy option, the first step involves determining the most significant barriers to 

implementation and using an incentive program, a compliance assistance program, or regulation to target 

and overcome that obstacle. 

Excerpt from the Maryland Chesapeake and Atlantic Coastal Bays

Critical Area 10% Rule Guidance Manual 

Option 4: Reducing the Imperviousness of 

 an Existing Property 

Some older waterfront areas are so intensely developed that there is no available land for most offset options. 

As an alternative, these jurisdictions may consider the option of reducing or eliminating impervious cover on 

publicly or privately owned lands. Some jurisdictions have acquired tax-delinquent properties within the Critical 

Area. These abandon properties may be purchased by a developer seeking an offset and can be subsequently 

converted to vegetated open space and maintained in a perpetual easement. Developers also have the option 

of purchasing private land for this purpose. 
19

Retrofit policies can gain greater community support when they directly address local needs or concerns. 

For example, if water supply is a local concern, the infiltration capacity of green infrastructure practices 

to recharge groundwater and/or the benefits of rainwater harvesting in conserving potable water sources 

should be emphasized. If energy costs are a local concern, energy savings associated with green roofs 

should be clearly communicated. 

To date, green infrastructure retrofit policies have largely been driven by municipalities’ immediate 

regulatory concerns with CSOs and stormwater runoff. However, future programs to encourage retrofits 

should capitalize more fully on the multiple benefits provided by green infrastructure. Chicago’s Energy 

Conservation Code is a good example of this approach. By granting an exception for green roofs from the 

reflectance and urban heat island provisions, the City is simultaneously encouraging broader adoption of 

green roofs and recognizing the multiple benefits they provide. 

In addition to water quality problems, municipalities will be increasingly challenged by sustainably 

managing infrastructure and addressing potential impacts of climate change. More than 700 mayors have 

signed on to the Mayors Climate Protection Agreement with the goal of a local 7% reduction in carbon 

dioxide emissions compared to 1990 levels. That goal, coupled with multi-billion dollar infrastructure

Overcoming Green Infrastructure Retrofit Obstacles

1. Determine the actual, local obstacles to green infrastructure implementation. 

There can be perceived obstacles and/or real obstacles. Obstacles may be common to many locations or 

specific to a particular location. Consequently, taking the time to accurately identify the biggest local obstacle to 

implementation will give credibility to an incentive or compliance assistance program when seeking approval or 

funding since the likelihood of success will be greater. (See “Determining Green Infrastructure Retrofit Goals”) 

2. Determine what will bridge the gap. 

Once the biggest obstacle is known, a creative solution to fill the gap between the current rate of installation and 

the desired rate of installation can be invented. (See “Steps to Creating a Successful Green Infrastructure 

Retrofit Policy”) 

3. Establish funding sources for the incentive or compliance assistance program. 

Since Green Infrastructure helps achieve many environmental, social and economic objectives, there are

diverse funding options that may be possible. Some include: 

• Stormwater Utility Fees 

• Sanitary Sewer Fees (where the program addresses CSOs) 

• Flood Control District funds 

• Grants 

• Energy Companies (where the green infrastructure practice reduces energy demand) 

4. Conduct a pilot test. 

Obstacles can only be overcome by an incentive program if the program is targeting the right obstacle and to 

the right degree. For this reason, a short term pilot that implements the incentive in a limited area or to a limited 

audience for a limited amount of time, helps determine if the incentive program is worthy of more funding or if it 

needs to be modified to accomplish the environmental goals. 

5. Assess the success of the incentive or compliance assistance program. 

The use of the pilot program should be measured to determine if the rate of green infrastructure installation is 

increasing to the level necessary to meet the environmental or watershed goals. 

6. Modify, continue, or expand. 

After the pilot period, based on the results of the use of the implementation program, either the incentive 

program may need to be modified to better fill the implementation gap, continued because it is successful, or 

expanded to cover an even broader audience or wider area of application. 
20

needs, creates a challenging environment in which to craft policy. Future policies should look beyond the 

compartmentalization of traditional media and establish criteria for urban sustainability. 

Green infrastructure implementation can be encouraged by establishing codes and regulations that 

mandate reductions in both energy usage and discharges of stormwater. This integrated approach would 

lead to a more comprehensive system of environmental management but would also require coordination 

across departments to facilitate funding and compliance assurance. This approach would also more fully

establish a policy framework that recognizes the relationship between water conveyance and treatment, 

energy, and climate. 

Policies should also make use of the economic advantages that green infrastructure provides. 

Simultaneously addressing several environmental requirements with one program uses municipal 

resources more efficiently; reducing the burden on infrastructure can limit additional capital investments. 

These savings can be incorporated into incentive programs. Tax abatements have been used to encourage 

development in economically distressed urban areas. This concept could also be applied to green 

redevelopment efforts. A predetermined period of tax abatement could be provided to projects that meet

certain green infrastructure requirements. The reductions in tax revenue from this type of policy can be 

justified by the decreased demand on municipal services provided by green infrastructure. 

Setting Green Infrastructure Retrofit Goals

1. Identify watershed goals. 

Identifying the watershed goals that green infrastructure will be used to meet helps determine which practices to use 

and how many will need to be implemented in order to achieve the environmental goals. This ensures that the green 

infrastructure retrofit policy being created is focused on real environmental improvement, from the outset. Watershed 

goals can include obtaining a particular level of: 

• Volume reduction 

• Pollutant load reduction 

• Reduced flooding 

• Groundwater recharge 

• Water supply/ reduced energy demand 

2. Identify applicable green infrastructure practices. 

Land use is a critical criterion for selecting appropriate practices. Some green infrastructure practices are better 

suited for urban application, and some are more appropriate for rural use. Also, some are better at removing certain 

pollutants than others, and some allow for infiltration, whereas others don’t. A particular green infrastructure practice, 

or combination of practices, can be selected depending upon the goals and application conditions. 

3. Determine the level of implementation that will meet the watershed goals. 

Once the most applicable green infrastructure practices have been selected, the degree of implementation that will 

accomplish the environmental goals should be determined. For example, how many square feet of green roofs need 

to be installed to accomplish the volume reduction necessary to protect the receiving water? Or, how many square 

feet of bioretention practices are needed in order to maintain natural groundwater aquifer levels? 

4. Measure goal attainment. 

The most important measure of green infrastructure retrofit success is evidence of beneficial impacts in the 

environment (e.g., healthy groundwater aquifers, healthy stream habitat, or reduced pollutant levels in receiving 

waters). A method to measure environmental improvement should be a part of a green infrastructure retrofit effort. If 

a green infrastructure retrofit incentive program or regulation is not resulting in measurable environmental 

improvement, the program and/or regulation should be reevaluated and modified to better achieve the watershed 

goals. In addition, it is useful to compile the number of green infrastructure practices installed or number of square 

feet of functioning green infrastructure practices in order to determine the effectiveness of the retrofit incentive 

program or regulation at increasing the number. However, success in implementing green infrastructure practices 

should not be mistaken for the importance of confirming the achievement of watershed goals. 
21

Each jurisdiction has its own set of unique challenges and opportunities, and successful green 

infrastructure retrofit policies capitalize on those opportunities to develop creative and sustainable

solutions. 

Steps to Creating a Successful Green Infrastructure Retrofit Policy

1. Establish the local green infrastructure objectives. 

Determine which green infrastructure practices should be implemented, and to what extent, in order to meet local 

watershed goals for stream health. (See “Setting Green Infrastructure Retrofit Goals”) 

2. Identify the biggest implementation obstacle. 

There is often more than one obstacle to implementation. However, by targeting the most prevalent obstacle, the 

largest audience is reached. Taking the time to understand the real, local obstacle is important as each 

community has different perceptions about green infrastructure and different levels of available resources, such 

as funding, technical expertise, and local contractors. (See “Overcoming Green Infrastructure Retrofit Obstacles”) 

3. Target the biggest implementation obstacle with an incentive or compliance assistance program. 

Create an incentive program that targets the biggest obstacle to implementation. Where the biggest obstacle is 

initial investment, the incentive program should provide money for installation costs. Where the biggest obstacle 

is technical knowledge, providing technical expertise would be an appropriate incentive. Operating the incentive 

program Years 1 through 3 allows time for the program to be publicized, and modifications to be made if the 

incentives aren’t effective, and also provides enough time for people to take advantage of the incentives before 

the regulation takes effect. 

4. Check local regulations or ordinances for internal obstacles. 

Before launching an incentive program or a compliance assistance program, local regulations and ordinances 

may need to be modified to allow compliance. For example, if the incentive program involves disconnecting 

downspouts and under the current requirements a permit is needed to do the work, a solution such as creating a 

waiver and/or eliminating the permit fee may help the incentive program operate as intended. 

5. Create regulations that become effective at a future date. 

Creating regulations that go into effect in Year 5 provides the ultimate incentive to take advantage of the 

opportunities for early implementation. 

6. Publicize the incentive or compliance assistance program and regulation. 

Use targeted outreach, as well as press releases, to ensure that the regulations, and the incentive program that 

helps people meet the regulations, is known and utilized by a broad audience. Targeted outreach helps reach 

those most likely to utilize the incentive program. For example, giving a presentation about a rain garden incentive 

program to Garden Club members who are likely to be interested in utilizing gardens for rainwater treatment can 

help jump start the program so that it can spread by word of mouth. Other mechanisms, such a press releases 

that may result in newspaper articles, communicate the purpose and benefits of the program and regulations to a 

wider audience and increase awareness about program and future requirements. 

7. Monitor the success of the incentive or compliance assistance program, and modify if necessary. 

A true incentive program provides an actual “incentive” to implement the green infrastructure practice. If an 

incentive program is underutilized, either the “incentive” is not enough, or not enough people are aware of the 

program. After a year of implementing the incentive program, the success of the program should be evaluated. If 

the program goals have not been met, the incentive program should be modified to better meet the program goals 

in Year 2. 
22

 

1

 U.S. EPA, National Water Quality Inventory: Report to Congress, 2002 Reporting Cycle, Office of Water, EPA841-R-07-001, October 2007. 

2

 United States Geological Survey, Water Quality and Nonpoint Sources in Urban Watersheds: Key Findings from 

the First Decade of NAWQA Studies. National Water-Quality Assessment (NAWQA) Program, 2008, available at 

http://water.usgs.gov/nawqa.informing.urbanization.html (accessed January 2008). 

3

 U.S. EPA, Report to Congress: Impacts and Control of CSOs and SSOs, Office of Water, EPA-833-R-04-001, 

August 2004. 

4

 U.S. EPA, Clean Watersheds Needs Survey 2004 Report to Congress, Office of Wastewater Management, January 

2008. 

5

 Thomas R. Schueler and Heather K. Holland, The Importance of Imperviousness: Article 1 from The Practice of 

Watershed Protection, The Center for Watershed Protection, 2000. 

6

 Wisconsin Department of Natural Resources, Impact of Redevelopment on TSS Loads, Runoff Management, 

available at http://www.dnr.state.wi.us/runoff/pdf/rules/nr151/Impact_of_RedevTSSLoads_021308.pdf (accessed 

June 2008). 

7

 Green Roofs: A Resource Manual for Municipal Policy Makers, Canada Mortgage and Housing Corporation, May 

2006. 

8

 See note 7. 

9

 City of Toronto Green Roofs Pilot Program webpage, available at 

http://www.toronto.ca/greenroofs/incentiveprogram.htm, (accessed June 2008). 

10 Toronto Staff Report April 18, 2007 

Where to Start (or Starting on Public Property)

Starting green infrastructure retrofitting on public property such as community centers, public parking lots, 

plazas, schools, City Hall, public libraries, public roads and sidewalks can provide benefits, including: 

1. The public develops familiarity with green infrastructure practices. 

By implementing green infrastructure practices in the public realm, members of the community have an 

opportunity to come in contact with them, perhaps frequently, and even learn about the practices from 

educational signs. Public areas provide high visibility locations for green infrastructure applications. As the 

public is exposed to these practices and can witness them functioning through out the changing seasons, they 

become more familiar and more comfortable with the practices. 

2. The private sector can monitor success of green infrastructure applications. 

Individuals or organizations interested in installing green infrastructure practices on their property, but unsure 

of its level of effectiveness or maintenance needs can observe or inquire about applications they see installed 

on public space. 

3. Costs decrease as a local market for green infrastructure is created. 

As more and more green infrastructure practices are installed, efficiencies and improvements to the process 

bring cost savings and often a better product. For example, as Chicago DOT utilized more porous concrete, 

the price decreased making it a more viable alternative for private property owners to install. 

4. Growing local supplies and local business. 

As the public sector invests in green infrastructure, it is investing in local, green businesses. This allows those 

businesses to grow and provide an even better product with more experienced installers. 

5. Giving the municipality first hand experience with design, construction, and maintenance before 

requiring it of others. 

As municipalities begin to require green infrastructure practices in their jurisdictions, property owners will ask 

questions about design, construction, and maintenance related to local climate, soil types, local suppliers and 

labor, and other local or regional variables. If the municipality has green infrastructure applications that they 

own, operate, and maintain, they will be able to answer questions and help private property owners to 

successfully implement green infrastructure approaches. 

6. Easy access for monitoring and tours. 

Public property applications of green infrastructure practices are easily accessible to the public for monitoring 

by students or tours by those interested in implementing something similar in their community or on their 

property. 
23

 

11 Toronto City Council Decision, Planning and Growth Management Committee, Item 4.1, Considered by City

Council on May 23, 24 and 25, 2007 

12 See note 7. 

13 City of Minneapolis Stormwater Utility Fee webpage, available at 

http://www.ci.minneapolis.mn.us/stormwater/fee/StormwaterQuantityCredits.asp, (accessed June 2008). 

14 City of Philadelphia Stormwater Management Guidance Manual Version 2.0, available at 

http://www.phillyriverinfo.org/programs/SubProgramMain.aspx?Id=StormwaterManual, (accessed June 2008). 

15 Clean River Rewards website: www.cleanriverrewards.com. 

16 Centennial Clean Water Fund Grant #G0000127 “Cooperative Approach to CSO Reduction” Final Report July

2003, available at http://www.cityofbremerton.com/content/forms/FinalReport_CSOReduction.pdf, (accessed June 

2008). 

17 Milwaukee Metropolitan Sewerage District, The Application of Stormwater Runoff Reduction Best Management 

Practices in Metropolitan Milwaukee, December 29, 2005. 

18 See note 16. 

19 Portland Bureau of Environmental Services, Downspout Disconnection Program, available at 

http://www.portlandonline.com/bes/index.cfm?c=43081&, (accessed June 2008). 

20 See note 18. 

21 Portland City Code Title 17.37, available at http://www.portlandonline.com/auditor/index.cfm?c=28181, 

(accessed June 2008). 

22 Bremerton Municipal Code Title 15, available at: http://www.codepublishing.com/wa/bremerton.html, (accessed 

June 2008). 

23 Conscious Choice: Chicago’s Green Alley Program, March 2008, available at 

http://www.consciouschoice.com/2008/03/commish0803.html, (accessed June 2008). 

24 Center for American Progress, It’s Easy Being Green: Chicago’s Alleys Get a Makeover, April 23,2008, available 

at http://www.americanprogress.org/issues/2008/04/green_alleys.html, (accessed June 2008). 

25 See note 22. 

26 Portland Bureau of Environmental Services, Portland Green Street Program, available at 

http://www.portlandonline.com/BES/index.cfm?c=44407, (accessed June 2008). 

27 Portland Bureau of Environmental Services, SW 12th Avenue Green Street Project Report, available at 

http://www.portlandonline.com/shared/cfm/image.cfm?id=167503, (accessed August 2008). 

28 American Society of Landscape Architects 2006 Professional Awards, General Design Award of Honor, available 

at http://www.asla.org/awards/2006/06winners/341.html, (accessed June 2008). 

29 Public Funding Incentives for Private Residential and Commercial Watershed Protection Projects: Report on Key 

Case Studies and Community Workshop; Montgomery County, Maryland Department of Environmental Protection, 

Division of Environmental Policy and Compliance, June 2007. 

30 Milwaukee Metropolitan Sewerage District, Lake Michigan Rain Garden Initiative, available at 

http://v2.mmsd.com/lmrgi.aspx, (accessed June 2008). 

31 Decentralized Stormwater Management: Retrofitting Homes, Restring Watersheds, Allison Roy, Matthew Clagett, 

Theresa Hoagland, Matthew Morrison, William Shuster, Joshua Templeton, Hale Thurston, HeribertoCabezas

available at http://www.epa.gov/ord/scienceforum/2006/pdfs/the_built_environment_final_posters/BE-30_Roy.pdf, 

(accessed June 2008). 

32 Buranen, Margaret, Rain Gardens Reign, Stormwater, May 2008. 

33 See note 30. 

34 Cooperative Conservation America, Cooperative Conservation Case Study, available at 

http://www.cooperativeconservationamerica.org/viewproject.asp?pid=999, (accessed June 2008). 

35 Seeing Green: Study Finds Greening is a Good Investment, Pennsylvania Horticultural Society, available at 

http://www.pennsylvaniahorticulturalsociety.org/phlgreen/seeinggreen.htm, (accessed June 2008). 

36 See note 33. 

37 Maryland Chesapeake and Atlantic Coastal Bays Critical Area 10% Rule Guidance Manual, Critical Area 

Commission for the Chesapeake and Atlantic Coastal Bays available at 

http://www.dnr.state.md.us/criticalarea/guidancepubs/10percent_rule.html, (accessed June 2008).