Low Impact
Development and
Green Strategies
for Regulatory
Compliance and
Resource
Protection
Low Impact Development Center 2007

CHAPTER 26 CFR - WATER POLLUTION
PREVENTION AND CONTROL
SUBCHAPTER I - RESEARCH AND RELATED
PROGRAMS
•§ 1251. Congressional declaration of goals and policy.
(a) Restoration and maintenance of chemical, physical and
biological integrity of Nation's waters; national goals for
achievement of objective.
• Ecosystems Based
• Technology-forcing
• Comprehensive Research
• Total Maximum Daily Load
Low Impact Development Center 2007

Low Impact Development Center 2007

Regulations and Resource Protection
Low Impact Development Center 2007

Environmental Environmental
Interests Interests
$
$
Development Development
Interests Interests
$
New Rules!
Low Impact Development Center 2007

Low Impact Development
Major Components
1. Conservation (Watershed and Site Level )
2. Minimization (Site Level)
3. Strategic Timing (Watershed and Site Level)
4. Integrated Management Practices (Site Level)
Retain / Detain / Filter / Recharge / Use
5. Pollution Prevention
Traditional Approaches
Low Impact Development Center 2007

Key LID Principles “Volume”
and Water Balance
to Achieve Objectives
Unique Watershed Design

Match Initial Abstraction Volume

Mimic Water Balance

Uniform Distribution of Small-scale Controls

Cumulative Impacts of Multiple Systems

filter / detain / retain / use / recharge / evaporate

Decentralized / Disconnection

Multifunctional Multipurpose Landscape & Architecture

Pollution Prevention

Low Impact Development Center 2007

1. Conservation Plans / Regulations
Local Watershed and Conservation Plans

Forest (Contiguous and Interior Habitat)

Large and Small Scale
Streams (Corridors)

Wetlands

Habitats

Step Slopes

Buffers

Critical Areas

Parks

Scenic Areas

Trails

Shorelines

Difficult Soils

Ag Lands

Minerals

Low Impact Development Center 2007

2. Minimize Impacts
Low Im pact Design
Multifunctional Use
of Landscape and
Infrastructure
Minimize clearing

Minimize grading

Save A and B soils

Limit lot disturbance Decentralized

Controls
* Soil Amendments
 Roofs
Parking Lots
Alternative Surfaces
 Open Drainage
Rain Barrels
Open Space
Reforestation
 Turf
Educational
Disconnect
 components
Reduce pipes, curb and gutters

Reduce impervious surfaces

Low Impact Development Center 2007

3. Maintain Time of Concentration
and Watershed Patterns
Open Drainage

Use green space

Flatten slopes

Disperse drainage

Lengthen flow paths

Save headwater areas

Vegetative swales

Maintain natural flow paths

Increase distance from streams

Maximize sheet flow

Low Impact Development Center 2007

4. Storage, Detention & Filtration
“LID IMP’s”
 Uniform Distribution at the Source
Open drainage swales

Rain Gardens / Bioretention

Smaller pipes and culverts

Small inlets

Depression storage

Infiltration

Rooftop storage

Pipe storage

Street storage

Rain Water Use

Soil Management**

Low Impact Development Center 2007
Emeryville and UCD

Low Impact Development Center 2007

5. Pollution Prevention
30 - 40% Reduction in N&P
Kettering Demonstration Project
Maintenance

Proper use, handling and disposal

Individuals

Lawn / car / hazardous wastes / reporting / recycling

Industry

Good house keeping / proper disposal / reuse / spills

Business

Alternative products / Product liability

Low Impact Development Center 2007

LID is Not
A land use or zoning control

An either this or that approach

Independent of watershed planning

“The” Answer

LID is
A Water Balance Approach to Hydrology

A science and unit process based approach

Decentralized and Integrated

Technology Driven

“The” Answer

Low Impact Development Center 2007

Stormwater
Drinking Water
LID is a Holistic
Integrated
Approach
Wastewater
Low Impact Development Center 2007

N2 AIR NH3
Where did it all start?
DENITRIFICATION
RAINFALL EVAPOTRANSPIRATION
ADSORPTION
PARTICULATES
LID
BIOLOGICAL FIXATION
PLANT MATERIALS
RUNOFF RUNOFF
Manual
VOLITILIZATION METALS,
NUTRIENTS
MULCH
SANDY SOIL MEDIUM AMMONIFICATION
Stormwater
NO3 NITROGEN FIXATION
Hydrology
NH4
Standards
DENITRIFICATION NO2
Manual
Manual
DRAIN
INFILTRATION RECHAR
GE
Landscaping Water
DPW Land
NITROGEN CYCLE FOR BIORETENTION
Conservation
Development
Manual
Manual
San Diego LID Manual
Village Homes
Low Impact Development Center 2007

High Rate
Bio-filtration
Low Impact Development Center 2007

AIR
N2 NH3
DENITRIFICATION RAINFALL EVAPOTRANSPIRATION
ADSORPTION
PARTICULATES
BIOLOGICAL FIXATION
PLANT MATERIALS
RUNOFF RUNOFF
VOLITILIZATION METALS,
NUTRIENTS
MULCH
SANDY SOIL MEDIUM AMMONIFICATION
NO3 NITROGEN FIXATION
NH4
DENITRIFICATION NO2
DRAIN
INFILTRATION RECHARGE
NITROGEN CYCLE FOR BIORETENTION
Low Impact Development Center 2007

Low Impact Development Center 2007

Bioretention
California
Low Impact Development Center 2007

“Traditional” Stormwater Issues
Non-Point Runoff
Volume
Trash & Debris
Low Impact Development Center 2007

Low Impact Development Center 2007

Traditional Urban Sustainable Urban
Drainage Drainage
Water
Quality
Capacity
Capacity
Amenity
The Good Old Days!
Low Impact Development Center 2007
Stahre, 2006

Conventional - 70’s
70’s Flood Control

Approach Single Event
Risk based storms (2-

year, 10-year, 100-year)
Site Design and

Watershed use same
approach (HEC,
NRCS) for Common
Platform
Low Impact Development Center 2007

Predictable “Simple” Processes
β
K= 2/3
AR
n
Low Impact Development Center 2007

80’s/90’s
70’s Flood Control Approach

Single event
Risk based storms (2-year,

10-year, 100-year)
Site Design and Watershed

use same approach (HEC,
NRCS) for Common
Platform
Bring in Efficiency and

P × Pj × × Rv
Loadings with %.
L= × C × A × 2.72
12
L = Load, P=Precipitation
Low Impact Development Center 2007

Today
Moving towards Tributary

Strategies
Loadings and Limits (303d)

Site Design Models don’t link

to Watershed Models
Rapid Assessments that may

have significant data or
science gaps
Costs and Predictability

unknown
Low Impact Development Center 2007

THE Difference
Q = CIA
∫ C (t )Q(t )dt
C=
∫ Q(t )dt
Is this state-of-the-art?
Low Impact Development Center 2007

Courtesy Geoanalysis
Low Impact Development Center 2007

Low Impact Development Center 2007
Courtesy Wong, 2001

Effective Work Index (W)
Range of
Geomorphically
Significant flows
Stream Flow
τc τbi
Characteristics of
Bed and Bank
Materials
τc 1.5
n
∑ (τ − τ c) ⋅ ∆ t
W= bi
Normal Dry
i= 1
Weather Flow
Level
Low Impact Development Center 2007
Geosyntec

Smart Growth/LID Hydrology
Are the Metrics and Protocols Right?

Control Runoff at Microwatershed Level

Consider Hydrologic Process in Microwatershed

Layout
Maintain First Order Receiving Streams

Maintain Vegetated Buffer Zones

Control Spatial Pattern of Hydrologic Storage

Control Upland Flow Velocities

Control Temporal Characteristics of Runoff

McQuen, 2004 Low Impact Development Center 2007

Incorporated into Master Plan
Low Impact Development Center 2007

Metro West
Illustrative
Plan
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Low Impact Development Center 2007
Emeryville

Land Use Change is a
better indicator!
Low Impact Development Center 2007

Issues
Where is a watershed with less than 10%

imperviousness?
Methods

Scale and location in watershed (avoid

headwaters)
Cumulative effects

Moglen, 2007
Low Impact Development Center 2007

Compacted
Dysfunctional
Soils
Low Impact Development Center 2007

Lawn Soil Compaction
Compaction (Mpa)
0.00 1.00 2.00 3.00 4.00 5.00
0
10
20
30
Depth (cm)
40
50
60
No
Uninhibited Impaired
Root
Root Root
Growth
Growth Growth
70
Low Impact Development Center 2007

Reston Watershed
Management Planning
Low Impact Development Center 2007

Low Impact Development Center 2007

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Low Impact Development Center 2007

Buttermilk off North Shore Buttermilk off Ring Road
Low Impact Development Center 2007

Low Impact Development Center 2007

Low Impact Development Center 2007

Stormwater Ponds:
Valuable Wildlife Habitat?
Low Impact Development Center 2007

TMDL Goose
Low Impact Development Center 2007

B-IBI w/BMPs B-IBI w/o BMPs
45
40
35
30
B-IBI Score
25
20
15
10
5
0
0 10 20 30 40 50 60 70
Watershed Urbanization (%TIA)
Figure 2: Showing the lack of mitigating influence of structural
BMPs on biologic conditions in Puget Sound lowland streams
(Horner and May, 2000). Note, “w/BMPs” refers to structural
facilities only. [Honer / May 2001]
Low Impact Development Center 2007

Figure 1. Comparison of Habitat Condition and
Montgomery County,
Biological Condition for Sites With and Without SWM
MD
Habitat Condition vs Biological Condition
Both of the datasets
Test Sites (With Stormwater Controls)
y=20.896*exp( 0.011*x)+eps
100
plot mainly below the
90
T08
line (Figure 1). Almost
80
(As % of Best Possible Score)
T01
Biological Condition
70
T06
RE2
all test sites do, and
60
DS3
T05 T07
DS2 T12DS1 RE4
T02
RE1
T04
T15
50
T10
while 6-7 of the
T14 T18
T03 T13
40
T16 T17 T09
T19 T11 T20
30
control sites plot
20
0 10 20 30 40 50 60 70 80 90 100
Habitat Condition (as per cent of Best Possible Score)
along the line, the
remainder plot below
Habitat Condition vs Biological Condition
Control Sites (Without Stormwater Controls)
y=17.126*exp( 0.016*x)+eps
the line.
100
90
Stream embedding
C04
C01
80
(As % of Best Possible Score)
C02
70
Biological Condition
Riffle areas
C05 C03
C07
60
C13
C06 C09
Flow regime
50
C18
C15
C14 C11
C12 C16 C20 C08
C17
40
C19
30
20
WMI
0 10 20 30 40 50 60 70 80 90 100
Low Impact Development Center 2007
Habitat Condition(as per cent of Best Possible Score)

Low Impact Development Center 2007

Where are the watershed
functions?Low Impact Development Center 2007

Low Impact Development Center 2007

The Future of the Urban America
Low Impact Development Center 2007

Low Impact Development Center 2007

Maintenance and Inspection
• Safety
• Inspection
• Access
• Special Equipment
• Costs
Low Impact Development Center 2007

Maintenance
Pond Liabilities
Limitations Safety
• Safety / Health
• Inspection / Maintenance
• Inefficient Pollutant Removal
• Temp / Sediment / Frequency /
Volume Low Impact Development Center 2007

Low Impact Development Center 2007

Cost/Effectiveness
A bioretention pond costs
$2,000 to construct for a ½ site.
So it costs $4,000 per acre.
MC = c IJ + mIJ Q
* RJ
2
Low Impact Development Center 2007

Low Impact Development Center 2007

BMP Removal Efficiency?
Low Impact Development Center 2007

Ecological Integrity
New Objectives
Protection
Species – Fauna / Flora
Structure – Spatial / Temp / Distribution
Processes – Cycling (Energy / Materials /
Nutrients)
Ecological Factors
• Hydrology / Hydraulics
• Habitat Structure
• Water Quality
• Energy Sources
Small Stream and Living
• Biotic Interactions
Resource Protection Impact Development Center 2007
Low

General Assumptions!
For the foreseeable future, urbanization will continue

mostly in the same patterns as today.
We don’t know exactly how much stress aquatic

ecosystems can sustain before they crash.
Where aquatic ecosystems are stressed terrestrial

ecosystems are dysfunctional.
Impact reduction strategies will most likely ensure

ongoing degradation of the ecological health due to
cumulative impacts.
There are no thresholds for acceptable levels of

stressors. Impacts to the ecological integrity occur
whenever ecological functions are altered or stressors
are added. Low Impact Development Center 2007

General Assumptions!
Our environmental technological challenge is

to integrate development into the ecosystem
as best we can in a manner that developed
areas remain a vital part of the ecosystem
instead of apart from it.
If growth and development continue

unabated, at best, technology can only delay
the onset of negative consequences.
Low Impact Development Center 2007

Paradigm Shifts
Watersheds to Ecosystems

Flow Centric to Volume Centric

Centralized Control to Decentralized Control

Uni-functional to Multifunctional

Impact Reduction to Functional Restoration

Good Drainage to Functional Drainage

One Size Fits All to Unique Design

Unsustainable to Sustainable

Low Impact Development Center 2007

Important Concepts
Terrestrial / aquatic ecosystem linkages

Ecosystem functions

Using nature to mitigate its own forces

Mimic the water balance

Hydrology as an organizing principle

Multiple systems

Volume / Frequency / Timing

Ecological functions of the built environment

Low Impact Development Center 2007

Conventional
Development
Centralized
Pipe and Pond
Control
Low Impact Development Center 2007

Multiple Systems
LID Development
Conservation
Minimization
Soil Amendments
Open Drainage
Rain Gardens
Rain Barrels
Pollution Prevention
Disconnected
Decentralized
Distributed
Multi-functional
Water Use
Low Impact Development Center 2007

Summerset Subdivision
Low Impact Development Center 2007

Monitoring Results
Discharge Comparision
0.04
LID Q
0.02 Conv. Q
Discharge,
cfs/acre
0.00
13:55 14:24 14:52 15:21 15:50 16:19
-0.02
Time, April 6, 2001
Low Impact Development Center 2007

Low Impact Development Center 2007

Quantifiable Costs and Benefits
$4
1.5
$2
1.5 1.5
$0 -0.1 -0.2
-0.4
(in $ millions)
Project Cost
-$2
-4.6 O&M
Savings from Loan
-$4
Increase Home Value
-8.9
-$6
-$8
-$10
Do Nothing Option 2 & 3 Traditional
Low Impact Development Center 2007

Green Highways
Watershed Driven Stormwater

Recyclables and Reuse

Ecosystems and Conservation

Low Impact Development Center 2007

Context Sensitive Solution?
Low Impact Development Center 2007

Green Highway Network
Development
Low Impact Development Center 2007

EMS/Performance Based Approach
Protect Environmental Legacy

Save Costs/Reduce Consumption

Ease Regulatory Burden

Improve Review Cycles

Low Impact Development Center 2007

GHP/Stormwater EMS Roadmap
1. Identify environmental
issue(s) and/or
opportunity(ies) to be 11. Managers/senior
management. Review
addressed by EMS.
progress, identify
adjustments, and confirm
2. Identify desired commitments.
environmental and
business results and
APPROVAL – benefits. 10B. PERIODIC 10A. PROJECT
Management
REVIEW REVIEW
provides
Brief management on Assess EMS
feedback to 3. Establish objectives, status in meeting project
finalize issues, quantifiable measures and objectives and targets. performance.
opportunities, targets, and associated
and expected milestones.
results. 9. Identify EMS-related
training needs,
responsibilities and
4. Obtain management
schedule. Conduct the
commitment to EMS,
training.
characterize EMS resource
needs, and identify EMS
leaders.
8. Identify personnel (by
title) affected by EMS,
define responsibilities, and
5. Identify existing
communicate
initiatives, programs,
responsibilities.
procedures, processes,
and tools relevant to the
EMS.
7. Assign responsibility for
developing enhanced or
6. Identify improvements to new procedures,
achieve EMS objectives processes, and tools.
PLAN DO CHECK ACT
LEGEND:
Low Impact Development Center 2007

Green Infrastructure
rs
opportunitiesive
are
R
everywhere
to s
p
to
f
o
LID tools facilitate the development of

o
green infrastructure
R
Transportation corridors provide linking

elements in a green infrastructure network
Low Impact Development Center 2007

It is a system of hubs and links
that provides measurable
benefits
..The term green infrastructure

emphasizes interconnected systems of
natural areas and other open spaces that
are protected and managed for the
ecological benefits that they provide to the
people and the environment.”
Low Impact Development Center 2007

Links and Hubs
An organizing form idea for planning green

infrastructure
Creates an interdependent network of

green
Fits a watershed model of planning

Can be implemented and maintained in

sections
Is an opportunity for public-private

partnerships
Low Impact Development Center 2007

Low Impact Development Center 2007

Historic Construct of
Stormwater Regulations
The majority regulate the peak flow rate of stormwater

discharges.
Do not sufficiently address hydrologic modifications

and the impacts on receiving water quality – do not
address increased volume of stormwater generated by
development.
Perpetuate the use of conventional end-of-pipe BMPs –

the use of which have not demonstrated significant
water quality improvements.
Fail to consider watershed criteria.

Low Impact Development Center 2007

Examples of robust LID Programs
Portland, Oregon
Photos courtesy of the Portland Bureau of Environmental Services.
Low Impact Development Center 2007

Portland, Oregon (cont.)
Photos courtesy of the Portland Bureau of Environmental Services.
Low Impact Development Center 2007

Seattle, Washington
Photos courtesy of Seattle Public Utilities.
Low Impact Development Center 2007

Vancouver, British Columbia
Photos courtesy of City of Vancouver Greenways Program.
Low Impact Development Center 2007

Vancouver, British Columbia (cont.)
Photos courtesy of City of Vancouver Greenways Program.
Low Impact Development Center 2007

What Motivated the Use of
New Approaches?
Portland’s innovative approaches to stormwater

management are necessitated by the need to satisfy a
CSO consent decree, SDWA requirements, impending
TMDL limitations, and Superfund cleanup measures.
Stormwater runoff from Seattle and Vancouver

discharges to receiving waters with salmon populations.
Low Impact Development Center 2007

Conclusions
Regulatory and environmental drivers create an

incentive for using new stormwater management
approaches.
When faced with certain and defined performance

criteria, source control and biological treatment of
stormwater emerges as a preferred treatment option.
How are jurisdictions developing regulations that spur

more wide-spread use of innovative stormwater
management?
Low Impact Development Center 2007

How are jurisdictions
developing regulations that
spur more wide-spread use
of innovative stormwater
management?
Low Impact Development Center 2007

Anne Arundel County, MD
Counties are permitted to establish more stringent

requirements than those required by the Maryland
Stormwater Manual.
AA County stipulates “The use of nonstructural

stormwater management practices shall be implemented
to the maximum extent practicable for satisfying the
recharge volume requirement prior to the use of
structural stormwater management practices to more
closely mimic the predevelopment hydrology and to
discourage the reliance on structural BMPs.”
Low Impact Development Center 2007

Effects of AA County Standard
Low Impact Development Center 2007

Maryland Stormwater Management
Act of 2007
Passed by the General Assembly in April and

signed into law by the Governor.
Requires the implementation of environmental

site design to the maximum extent practicable
and review and modification of ordinances to
remove impediments to ESD.
Developers must demonstrate that ESD has

been optimized on new development sites
before using conventional BMPs.
Low Impact Development Center 2007

New Jersey Stormwater Regulations
Groundwater recharge requirement:

Require that 100% of pre-development average annual

groundwater recharge volume for the site is maintained post-
development, OR
That the post-development increase in stormwater runoff for

the 2-year storm is infiltrated.
Water quality requirement:

80% removal of TSS and reduction of nutrients to the

maximum extent feasible, with an emphasis on non-structural
practices.
Low Impact Development Center 2007

New Jersey Stormwater
Regulations (cont.)
Runoff quantity requirement:

 Require that post-development runoff hydrographs for
the 2, 10, and 100-year storm do not exceed, at any point
in time, the predevelopment hydrographs, OR
 Demonstrate that there is no increase in peak runoff
rates for the 2, 10, and 100-year storm events and that
the increased volume and change of timing does not
have downstream impacts, OR
 Demonstrate that post-development peak runoff rates
for the 2, 10, and 100-year storm events are 50, 75, and
80%, respectively, of pre-development runoff rates.
Low Impact Development Center 2007

Portland Stormwater Regulations
City code requires on-site stormwater management for

new development and redevelopment (i.e., retention
and infiltration).
For other properties, stormwater must be retained or

infiltrated to the maximum extent practicable before
off-site discharge is allowed.
Required 70% removal of TSS and treatment for

pollutants with TMDL limitations in receiving stream.
Low Impact Development Center 2007

Washington, DC
Anacostia River Redevelopment
The AWC is responsible for

revitalization of lands along
the river and coordinating
environmental and
programming initiatives that
promote river clean up.
One-inch, on-site retention

standard and water quality
treatment for up to the 2-year
storm for new development
and re-development.
Stated preference for

vegetated controls.
Adopted by AWC board June

1st.
Low Impact Development Center 2007

Seattle Green Factor
Requires 30% of a parcel in the Neighborhood Commercial

Zone to be vegetated or the functional equivalent as
determined by the Green Factor.
For example, the Green Factor for green roofs is 0.7,

permeable paving is 0.6, and lawn is 0.2. Bonuses provided
for rainwater harvesting or planting low water-use
vegetation.
Encourages the planting of layers of vegetation on the

property and in public right-of-ways adjacent to the
property.
In effect as of January 2007.

Low Impact Development Center 2007

Recommendations for Regulations
Incorporate volume and hydrologic performance

requirements into regulations.
Create regulatory certainty.

Provide incentives for developers that use LID (e.g.,

streamline review process or move stormwater plans to
the top of the stack).
Maryland offers six different stormwater credits for

green practices.
Low Impact Development Center 2007

Incentives for LID Outside of
Regulatory Structure
Chicago and Portland offer density and building square

footage bonuses, respectively, for buildings with green
roofs.
Offer discounts for stormwater or other utility fees for

on-site or LID management practices – full-cost pricing
is critical.
Subsidized downspout disconnection programs.

In January 2006, Chicago provided 20 $5,000 grants for

residential and small-scale commercial green roofs and
received 123 applications.
Low Impact Development Center 2007

Coyote Creek Watershed
Courtesy E. Takata
Low Impact Development Center 2007

Coyote Creek Green
Infrastructure Principles
Start upstream

Connect the Dots

Use Nature as a Guide

All Fronts/No backs

Manage for the Long Term

Multiple Objectives

Low Impact Development Center 2007