Reducing Stormwater Costs through
Low Impact Development (LID)
Strategies and Practices
This fact sheet provides additional information about EPA's report Reducing
Stormwater Costs through Low Impact Development (LID) Strategies and Practices,
EPA publication number 841-F-07-006, December 2007.
BACKGROUND
Stormwater has been identified as a major source of pollution for
all waterbody types in the United States, and the impacts of
stormwater pollution are not static; they usually increase with
land development and urbanization. The additi on of impervi ous
surfaces, soil compaction, and tree and vegetation removal result
in alterations to the movement of water through the environ-
ment. As interception, evapotranspiration, and infiltration are
reduced and precipitation is converted to overland flow, these
modifi cations affect not only the characteristics of the developed
site but also the watershed in which the development is located.
Low Impact Development (LID) is a stormwater management
strategy that seeks to mitigate the impacts of increased runoff
and stormwater pollution. LED comprises a set of site design
approaches and small-scale stormwater management practices
that promote the use of natural systems for infiltration,
evapotranspiration, and reuse of rainwater. These practices can
effectively remove nutrients, pathogens, and metals from
stormwater, and they reduce the volume and intensity of
stormwater flows.
COST ANALYSIS
This report is an effort to compare the projected or known costs of LID practices with those of
conventional development approaches. Traditional approaches to stormwater management typically
involve hard infrastructure, such as curbs, gutters, and piping. LID-based designs, in contrast, are
designed to use natural drainage features or engineered swales and vegetated contours for runoff
conveyance and treatment. In terms of costs, LID techniques can reduce the amount of materials needed
for paving roads and driveways and for installing curbs and gutters. Other LID techniques can eliminate
or reduce the need for curbs and gutters, thereby reducing infrastructure costs. Also, by infiltrating or
evaporating runoff, LID techniques can reduce the size and cost of flood-control structures. Note that in
some circumstances LID techniques might result in higher costs because of more expensive plant material,
site preparation, soil amendments, underdrains and connections to municipal stormwater systems, as well
as increased project management costs. Other considerations include land required to implement a
management practice and differences in maintenance requirements. Finally, in some circumstances LID
practices can offset the costs associated with regulatory requirements for stormwater control.
Parking lot runoff is allowed to infiltrate
through a vegetated bioretention area
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FINDINGS
Seventeen case
studies were
evaluated for this
report. In general,
the case studies
demonstrated that
LID practices can
reduce project costs
and improve
environmental
performance.
Although not all the
benefits of the
projects highlighted
in the case studies
were monetized,
with a few
exceptions, LID
practices were
shown to be both
fiscally and environ-
Table t. Cost Comparisons Between Conventional and L
D Approaches
Project3
Conventional
Development
Cost
LiD Cost
Cost
Differenceb
Percent
Difference11
2nd Avenue SEA Street
$868,803
$651,548
$217,255
25%
Auburn Hills
$2,360,385
$1,598,989
$761,396
32%
Bellingham City Hall
$27,600
$5,600
$22,000
80%
Bellingham Bloedel Donovan Park
$52,800
$12,800
$40,000
76%
Gap Creek
$4,620,600
$3,942,100
$678,500
15%
Garden Valley
$324,400
$260,700
$63,700
20%
Kensington Estates
$765,700
$1,502,900
-$737,200
-96%
Laurel Springs
$1,654,021
$1,149,552
$504,469
30%
Mill Creek0
$12,510
$9,099
$3,411
27%
Prairie Glen
$1,004,848
$599,536
$405,312
40%
Somerset
$2,456,843
$1,671,461
$785,382
32%
Tel labs Corporate Campus
$3,162,160
$2,700,650
$461,510
15%
a Some of the case study results do not lend themselves to display in the format of this table (Central Park
Commercial Redesigns, Crown Street, Poplar Street Apartments, Prairie Crossing, Portland Downspout
Disconnection, and Toronto Green Roofs). bNegative values denote increased cost for the LID design over
conventional development costs.c Mill Creek costs are reported on a per-lot basis.
mentally beneficial to communities. In a few case studies, initial project costs were higher than those
for conventional designs; in most cases, however, significant savings were realized due to reduced costs
for site grading and preparation, stormwater infrastructure, site paving, and landscaping. Total capital
cost savings ranged from 15 to 80 percent when LID methods were used, with a few exceptions in which
LID project costs were higher than conventional stormwater management costs. (Table 1)
A rain garden manages runoff from
impervious surfaces such as roofs and
paved areas.
In all cases, LID provided other benefits that were not monetized
and factored into the project bottom line. These benefits include
improved aesthetics, expanded recreational opportunities,
increased property values due to the desirability of the lots and
their proximity to open space, increased total number of units
developed, increased marketing potential, and faster sales. The
case studies also provided other environmental benefits such as
reduced runoff volumes and pollutant loadings to downstream
waters, and reduced incidences of combined sewer overflows.
CONCLUSIONS
This report summarizes 17 case studies of developments that
include LID practices and concludes that applying LID
techniques can reduce project costs and improve environmental
performance. In most cases, LID practices were shown to be
both fiscally and environmentally beneficial communities. In a
few cases, LID project costs were higher than those for
conventional stormwater management projects. However, in the
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vast majority of cases, significant savings were realized
due to reduced costs for site grading and preparation,
stormwater infrastructure, site paving, and landscaping.
Total capital cost savings ranged from 15 to 80 percent
when LID methods were used, with a few exceptions in
which LID project costs were higher than conventional
stormwater management costs.
Green roofs capture rainfall, promote
evapotransporation, and offer energy savings.
This is a photo of a green roof on the EPA
Region 8 building in Denver, CO.
EPA has identified several additional areas that will
require further study. First, in all cases, there were
benefits that this study did not monetize and did not
factor into the project's bottom line. These benefits
include improved aesthetics, expanded recreational
opportunities, increased property values due to the
desirability of the lots and their proximity to open
space, increased total number of units developed,
increased marketing potential, and faster sales.
Second, more research is also needed to quantify the environmental benefits that can be achieved
through the use of LID techniques and the costs that can be avoided. Examples of environmental
benefits include reduced runoff volumes and pollutant loadings to downstream waters, and reduced
incidences of combined sewer overflows. Finally, more research is needed to monetize the cost
reductions that can be achieved through improved environmental performance, reductions in long-term
operation and maintenance costs, and/or reductions in the life cycle costs of replacing or rehabilitating
infrastructure.
AVAILABILITY
The full report is available for download at www.epa.gov/nps/lid.
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