Stormwater Management:
Making Sure Green Is Green
Cahill Associates
Environmental Consultants
West Chester, PA 19382
Cape May, NJ 08204
Critical Link between
Land and Water:
Two Sides of the Same Coin
What happens on the land….
Conventional
Jersey City Reservoir, Morris County
…has everything to do with what
happens in and to the water.
Components of Sustainability
Water-Related:
• Comprehensive Stormwater
Management
• Recycled Wastewater
• Water Conserving Water Use
• Just for Starters
The Problem - From Smart Growth…
“The only thing new in the world is the history
we’ve forgotten….”
Harry Truman
Sustainability…
• Relates to private residential subdivision
and retail and office and industrial
centers….
• Also relates to public facilities like schools
and parks and recreational facilities and
roads….
This could be a new park next to you!
Stormwater Impacts of Conventional
Development (including Parks and Rec!)
• Not just Increased Flooding!
• Increased Runoff Volume
• Decreased Evapotranspiration and
Groundwater Recharge
• Increased Frequency of Runoff Events
• Faster Conveyance of Water
• Erosion and Stream Channel Changes
• Decreased Baseflow
• Impacted Aquatic Life
• Pollutants and Temperature Impacts
…not to mention other impacts of
conventional development practices…
Habitat Loss/Biodiversity
Wetlands/Floodplains/Other Areas
Soils/Special Geologic Features
Air Quality/Microclimate
Noise
Historical/Archaeological
Aesthetics/Scenic
Quality of Life
Public Health
Balancing
the Water
Cycle
Annual Hydrologic Cycle
For an Average Year
Altered Hydrologic Cycle
Infiltration
Surface Runoff
Conventional Development
Water Cycle Impacts:
• Increased Peak Runoff Rate
• Increased Runoff Volumes
• Decreased Infiltration
• Decreased Groundwater Recharge
• Decreased Stream Baseflow
• Decreased Evapotranspiration
• Temperature
All of which translate into many more related hydrologic,
ecologic, other impacts.
Conventional (Detention)
Stormwater Management
• Controls Peak Rate of Runoff to
Predevelopment Conditions
• Fails to Control Volume of Runoff
• Fails to Control Nonpoint
Pollutant/Temperature Loadings
We all live downstream….
We haven’t understood the basic
hydrology of stream and river
systems.
Average Annual Rainfall Volume that Occurs by Storm
Magnitude for Harrisburg, PA
Average Annual Rainfall Volume that Occurs by Storm Magnitude for Harrisburg, PA
PA State Climatological Office, 1926 - 2003)
(PA( State
Climatological Office, 1926 – 2003)
65%
0.1” - 1”
4" +
3" - 4"
2" - 3"
1" - 2"
0.1" - 1"
1%
1%
6%
27%
Stormwater management has
focused only on the largest
storms…we haven’t paid attention
to annual water balance and the
reality of smaller storms.
WAT
ER T
SOIL
ABLE
(DEV
ELOP
ED C
OND
ITIO
NS)
WELL
STREAM
BEDROCK
AQUIFER
Cahill Associates
Environmental Consultants
Green Valleys Association
Manage Stormwater as a Precious
Resource… not a Disposal Problem
for Stream Baseflow/Low Flow
for Wells and Springs
for Wetlands
Nonpoint Source Pollution
•
•
•
•
•
•
•
Transported by and dissolved in runoff
Petroleum Hydrocarbons
Metals
Nutrients (Phosphorus and Nitrate)
Organic matter
Sediment
Synthetic Organics (pesticides,herbicides)
Impacts on:
Stream Morphology
Aquatic Habitat
Bank Erosion and Undercutting
Streambed Scouring
Dry Channels…
Eroded
Streambanks…
Land Development Impacts on
Stream Morphology:
• Channel widening, downcutting, scouring
• Stream bank erosion
• Imbedded substrate with benthic impacts
• Loss of pools, riffles
Land Development Impacts on
Stream Ecology:
• Reduced diversity of aquatic insects
• Reduced diversity of fish
• Decline of amphibians
• Degraded wetlands, riparian zones
Land Development Impacts on
Vegetation
Trees:
the Perfect
BMP
Land Development Impacts on Soil:
A Living Foundation
Soil Horizons
• Layer of Soil Parallel to
Surface
• Properties a function of
climate, landscape
setting, parent material,
biological activity, and
other soil forming
processes.
• Horizons (A, E, B, C, R,
etc)
Image Source: University of Texas,
2002
Dramatic increases
in soil compaction…
Common Bulk Density Measurements or
How compacted is this soil?
Undisturbed Lands:
Forests & Woodlands
Residential
Neighborhoods
1.03g/cc
1.69 to 1.97g/cc
Golf Courses, Parks, Athletic Fields
CONCRETE
1.69 to 1.97g/cc
2.2g/cc
David B. Friedman, District Director -- Ocean County Soil Conservation District
Bulk Density is defined as the weight of a unit volume of soil including its pore space (g/cc or grams/cubic centimeter). Water and air are
important components of soil and we must frame our soil concepts so that factors affecting water and air dynamics are included. Thus, we are
primarily interested in bulk density and pore space as they affect water and aeration status, and root penetration and development.
Effects of Soil Disturbance
Measurements of Sampled Soil within 20 inches of surface
SITE
Bulk Density (g/cm³)
Permeability (in/hr)
Woods
1.42
15
Pasture
1.47
9.9
Single House
1.67
7.1
Subdivision Lawn 1
1.79
0.14
Garage Lawn
1.82
0.04
Cleared Woods
1.83
0.13
Subdivision Lawn 2
2.03
0.03
Althletic Field
1.95
0.01
CONCRETE
2.2 - 2.4
0
Adapted from Impact of Soil Disturbance During Construction on Bulk Density
and Infiltration in Ocean County, New Jersey (2001) - www.ocscd.org/soil.pdf
Getting Stormwater Right:
Structural BMPs
Mitigative
Non-Structural BMPs
Preventive
Site Planning & Design Procedures
WATERSHED ANALYSIS
SITE ANALYSIS
NON-STRUCTURAL BMPs STRUCTURAL BMPs
Soil
Infiltrationbased BMPs
Lot Configuration &
Clustering
APPLICANT
SUBMISSION
Minimum Disturbance,
Minimum Maintenance
Background
Factors:
Environmental
Constraints
Site Factors
Inventory
Sensitive Areas
Background
Factors:
Environmental
Opportunities
PRESUBMISSION
MEETING
Site Analysis:
Constraints vs.
Opportunities
WATERSHED
ANALYSIS
SITE ANALYSIS
BUILDING
PROGRAM
ISSUES
Zoning
Guidance
Township
Comprehensive
Plan
Volume
Reduction
BMPs
Impervious Coverage
Runoff
Quality
BMPs
Disconnect, Distribute,
Decentralize
Restoration
BMPs
Source Control
Design Phase 1
PREVENTIVE
BMPs
Design Phase 2
MITIGATIVE
BMPs
STORMWATER
CALCULATIONS
SLDO
Guidance
STORMWATER
MANAGEMENT
PLAN
Structural Best Management Practices
Runoff Volume/Infiltration-Oriented
Vegetative and Soil-Based
1.
Rain/recharge gardens/Bioretention
2.
Vegetated filter strips
3.
Vegetated Swales (Bio-infiltration, Dry, Wet)
4.
Porous pavement with infiltration beds
5.
Infiltration basins
6.
Subsurface infiltration beds
7.
Infiltration trenches
8.
French drains/dry wells
9.
Outlet control (level spreaders, etc.)
10. Retentive grading techniques, berms
Runoff Volume/Non-Infiltration-Oriented
11. Vegetated roofs
12. Cisterns/Rain Barrels/Capture Reuse
Runoff Quality/Non-Infiltration
13. Constructed wetlands
14. Wet ponds/retention basins
15. Filters
16. Water quality inserts
17. Detention/Extended Detention
18. Special Storage: Parking Lot, Rooftop, etc.
Restoration BMPs
19. Riparian Corridor Restoration
20. Revegetation/Reforestation
21. Soils Amendment
One size no longer fits all…
Structural BMPs
Runoff Volume/Infiltration-Oriented
Vegetative and Soil-Based
•
•
•
•
•
•
•
•
•
•
Porous Pavement
Infiltration Basin
Infiltration Bed
Infiltration Trench
Rain Garden/Bioretention
Dry Well / Seepage Pit
Constructed Filter
Vegetated Swale
Vegetated Filter Strip
Berm
Pollutant Removal Effectiveness
POLLUTANT
INFILTRATION
PRACTICES
Stormwater
Wetlands
Stormwater
Ponds Wet
Filtering
Practices
Water
Quality
Swales
Stormwater
Dry Ponds
Total
Phosphorus
70
49
51
59
34
19
Soluble
Phosphorus
85
35
66
3
38
-6
Total Nitrogen
51
30
33
38
84
25
Nitrate
82
67
43
-14
31
4
Copper
N/A
40
57
49
51
26
Zinc
99
44
66
88
71
26
TSS
95
76
80
86
81
47
Water quality benefits of porous pavement with infiltration from
“National Pollutant Removal Performance Database for Stormwater
Treatment Practices” Center for Watershed Protection, June 2000 \
Porous
Pavement
Porous Paving w/ Infiltration
Rams Head Plaza at University of North Carolina
DuPont Barley Mills Office Complex
Cahill Associates
Environmental Consultants
West Chester, PA 19382
Cape May, NJ 08204
Cahill Associates
Environmental Consultants
West Chester, PA 19382
Cape May, NJ 08204
•
•
•
•
•
Precipitation is carried from roof by roof drains to storage beds.
Stormwater runoff from impervious and lawn areas is carried to storage
beds.
Precipitation that falls on porous paving enters storage beds directly
Stone beds with 40% void space store water. Continuously perforated pipes
distribute stormwater from impervious surfaces evenly throughout the beds.
Stormwater exfiltrates from storage beds into soil, recharging groundwater.
Costs of Porous Pavement
• Generally costs the same or less for the site
• Actual asphalt slightly more expensive
(special gradation and higher grade binder)
• Reduces Piping Infrastructure and Basins
• Penn State Berks Campus – 320 spaces 1999
- $3500 / space budgeted for standard pavement
- $2700 actual cost for porous
Swarthmore College
Permeable Patios, Terraces, Courtyards
Infiltration Basins
Infiltration Basin – Commerce Plaza 1983
Vegetated Infiltration Beds
Distributing
Water in SubSurface Bed
Penn New School
43rd and Locust Streets
• PaDEP Growing Greener & Philadelphia Water
Department
• Porous Pavement Play Yard
• Infiltration Bed Beneath Athletic Field
• Rain Gardens and Native Vegetation
• Environmental Education
Previous impervious parking lot at site
Completed Porous Pavement Playfield
Infiltration Trenches
Rain Gardens / Bioretention
Rainwater can support
the landscape and
soils, reducing pipes
and basins.
Dry Well / Seepage Pit
Vegetated Swales (simple & inexpensive)
Vegetated Swale (Enhanced)
Vegetated Filter
Strip
Infiltration Berms
Structural Best Management Practices
Runoff Volume/Infiltration-Oriented
Vegetative and Soil-Based
1.
Rain/recharge gardens/Bioretention
2.
Vegetated filter strips
3.
Vegetated Swales (Bio-infiltration, Dry, Wet)
4.
Porous pavement with infiltration beds
5.
Infiltration basins
6.
Subsurface infiltration beds
7.
Infiltration trenches
8.
French drains/dry wells
9.
Outlet control (level spreaders, etc.)
10. Retentive grading techniques, berms
Runoff Volume/Non-Infiltration-Oriented
11. Vegetated roofs
12. Cisterns/Rain Barrels/Capture Reuse
Runoff Quality/Non-Infiltration
13. Constructed wetlands
14. Wet ponds/retention basins
15. Filters
16. Water quality inserts
17. Detention/Extended Detention
18. Special Storage: Parking Lot, Rooftop, etc.
Restoration BMPs
19. Riparian Corridor Restoration
20. Revegetation/Reforestation
21. Soil Amendment
Vegetated Roof
Vegetated Rooftops
• Reduce the Volume of Stormwater Runoff
(typically 50% or more annually)
• Reduce the Rate of Stormwater Runoff
• Increase the Lifespan of a Conventional Roof
Surface by 2 to 3 times
• Reduce heating and cooling costs
• Enhance property values and Aesthetics
Fencing Academy of Philadelphia
RoofmeadowTM
After
Before
Stuttgart’s “Green Space”
Capture / Reuse
• Volume Control
• Reduced potable
water consumption
• Cost savings
UNC-Chapel
Hill
• $1.5 billion construction
program, largest in 211year history of UNC-CH
• Funded in part by
biggest higher
education bond in
U.S.
• Guided by awardwinning 2001
Campus Master Plan
• Included an
Environmental
component which set
rigorous goals
UNC-Chapel Hill Campus Master Plan
Ayers Saint Gross, Architects
Rams Head Stormwater System
•40,000 SF Green roof plaza
•Cistern
•Vegetated swale w/ check dams
Image Source:
Andropogon
Associates
•Reinforced-turf fire
lane
•Storage/infiltration bed
under artificial turf
athletic field
•Re-created ephemeral
stream
•Water quality inserts
•Manages runoff from
project area and
additional 17 acres
Vegetated
Roof Plaza
Unique, non-proprietary system design, including:
• 56,000-gallon cistern under pathways
• Additional 32,000-gallon water storage zone under soil
to support trees
• Visual stormwater connections and overflows
• 12 to 24 inches of soil for native trees and groundcovers
• Perforated pipe and Rainstore distribution system
Green Roof Plaza with Cisterns
• Cistern
constructed of
recycled plastic
“Rainstore”
• Overflow to
Storage Layer
under soil
•56,000 gallon cistern filled by
2.7 inches of rainfall (in one or
more storms)
•On average, it will fill and empty
9 times per irrigation season
•Provides 3 weeks irrigation
without replenishment
Flood test of cistern area
Bricks being placed above cistern
…And then into an Infiltration Bed beneath an
Artificial Turf Athletic Field
Returning
Springs and
Stormwater
Flow to
Daylight
Structural Best Management Practices
Runoff Volume/Infiltration-Oriented
Vegetative and Soil-Based
1.
Rain/recharge gardens/Bioretention
2.
Vegetated filter strips
3.
Vegetated Swales (Bio-infiltration, Dry, Wet)
4.
Porous pavement with infiltration beds
5.
Infiltration basins
6.
Subsurface infiltration beds
7.
Infiltration trenches
8.
French drains/dry wells
9.
Outlet control (level spreaders, etc.)
10. Retentive grading techniques, berms
Runoff Volume/Non-Infiltration-Oriented
11. Vegetated roofs
12. Cisterns/Rain Barrels/Capture Reuse
Runoff Quality/Non-Infiltration
13. Constructed wetlands
14. Wet ponds/retention basins
15. Filters
16. Water quality inserts
17. Detention/Extended Detention
18. Special Storage: Parking Lot, Rooftop, etc.
Restoration BMPs
19. Riparian Corridor Restoration
20. Revegetation/Reforestation
21. Soil Amendment
Constructed Wetlands
Wet Pond / Retention Basin
Water Quality Inserts/Filters
Structural Best Management Practices
Runoff Volume/Infiltration-Oriented
Vegetative and Soil-Based
1.
Rain/recharge gardens/Bioretention
2.
Vegetated filter strips
3.
Vegetated Swales (Bio-infiltration, Dry, Wet)
4.
Porous pavement with infiltration beds
5.
Infiltration basins
6.
Subsurface infiltration beds
7.
Infiltration trenches
8.
French drains/dry wells
9.
Outlet control (level spreaders, etc.)
10. Retentive grading techniques, berms
Runoff Volume/Non-Infiltration-Oriented
11. Vegetated roofs
12. Cisterns/Rain Barrels/Capture Reuse
Runoff Quality/Non-Infiltration
13. Constructed wetlands
14. Wet ponds/retention basins
15. Filters
16. Water quality inserts
17. Detention/Extended Detention
18. Special Storage: Parking Lot, Rooftop, etc.
Restoration BMPs
19. Riparian Corridor Restoration
20. Revegetation/Reforestation
21. Soil Amendment
Riparian Buffer Restoration and Reforestation
Landscape Restoration
Seeding
1st year
Lawn to Sustainable Meadows
2nd year
3rd year
Images courtesy of Rolf Sauer and Partners
Landscape Restoration (cont.)
Soil Amendment / Restoration
Non-Structural Strategies
aka Low Impact Development
aka Conservation Design
aka Green Infrastructure
Even for Community Parks!
Site Planning & Design Procedures
WATERSHED ANALYSIS
SITE ANALYSIS
NON-STRUCTURAL BMPs STRUCTURAL BMPs
Soil
Infiltrationbased BMPs
Lot Configuration &
Clustering
APPLICANT
SUBMISSION
Minimum Disturbance,
Minimum Maintenance
Background
Factors:
Environmental
Constraints
Site Factors
Inventory
Sensitive Areas
Background
Factors:
Environmental
Opportunities
PRESUBMISSION
MEETING
Site Analysis:
Constraints vs.
Opportunities
WATERSHED
ANALYSIS
SITE ANALYSIS
BUILDING
PROGRAM
ISSUES
Zoning
Guidance
Township
Comprehensive
Plan
Volume
Reduction
BMPs
Impervious Coverage
Runoff
Quality
BMPs
Disconnect, Distribute,
Decentralize
Restoration
BMPs
Source Control
Design Phase 1
PREVENTIVE
BMPs
Design Phase 2
MITIGATIVE
BMPs
STORMWATER
CALCULATIONS
SLDO
Guidance
STORMWATER
MANAGEMENT
PLAN
Non-Structural BMP Categories with Specific NonStructural BMPs
1.0 Protect Sensitive and Special Value Resources
BMP 1.1 Protect sensitive/special value features
BMP 1.2 Protect/conserve/enhance utilize riparian areas
BMP 1.3 Protect/utilize natural flow pathways in overall stormwater
planning and design
2.0 Cluster and Concentrate
BMP 2.1 Cluster uses at each site; Build on the smallest area possible
BMP 2.2 Concentrate uses areawide through Smart Growth practices
3.0 Minimize Disturbance and Minimize Maintenance
BMP 3.1 Minimize total disturbed area – grading
BMP 3.2 Minimize soil compaction in disturbed areas
BMP 3.3 Re-vegetate and re-forest disturbed areas, using native species
4.0 Reduce Impervious Cover
BMP 4.1 Reduce street imperviousness
BMP 4.2 Reduce parking imperviousness
5.0 Disconnect/Distribute/Decentralize
BMP 5.1 Rooftop disconnection
BMP 5.2 Disconnection from storm sewers
Non-Structural BMP Categories with Specific NonStructural BMP’s
1.0
Protect Sensitive and Special Value Resources
BMP 1.1
BMP 1.2
BMP 1.3
Protect sensitive/special value
features
Protect/conserve/enhance utilize
riparian areas
Protect/utilize natural flow
pathways in overall stormwater
planning and design
Non-Structural BMP Categories with Specific
Non-Structural BMPs
2.0 Cluster and Concentrate
BMP 2.1
BMP 2.2
Cluster uses at each site; build
on the smallest area possible
Concentrate uses areawide
through Smart Growth
practices
Cost Comparison:
Chapel Run
Conventional Development
Conservation Design-Parkway
$2,460,200
$ 888,735
Non-Structural BMP Categories with Specific NonStructural BMPs
3.0
Minimize Disturbance and Minimize
Maintenance
BMP 3.1
BMP 3.2
BMP 3.3
Minimize total disturbed area –
grading
Minimize soil compaction in
disturbed areas
Re-vegetate and re-forest
disturbed areas, using native
species
Non-Structural BMP Categories with Specific
Non-Structural BMPs
4.0 Reduce Impervious Cover
BMP 4.1
BMP 4.2
Reduce street imperviousness
Reduce parking imperviousness
Table 1: Narrow Residential Street Widths
Jurisdiction
State of New Jersey
Residential Street Pavement
Width
20 ft. (no parking)
28 ft. (parking on one side)
State of Delaware
Maximum Daily Traffic
(trips/day)
0-3,500
0-3,500
12 ft. (alley)
---
21 ft. (parking on one side)
---
Howard County, Maryland
24 ft. (parking not regulated)
1,000
Charles County, Maryland
24 ft. (parking not regulated)
---
Morgantown, West Virginia
22 ft. (parking on one side)
---
Boulder, Colorado
20 ft.
20 ft. (no parking)
350-1,000
22 ft. (parking on one side)
350
26 ft. (parking on both sides)
350
26 ft. (parking on one side)
Bucks County, Pennsylvania
150
12 ft (alley)
500-1,000
---
16-18 ft. (no parking)
200
20-22 ft. (no parking)
200-1,000
26 ft. (parking on one side)
200
28 ft. (parking on one side)
200-1,000
(Cohen, 1997; Bucks County Planning Commission, 1980; Center for Watershed Protection, 1998)
Non-Structural BMP Categories with Specific
Non-Structural BMPs:
5.0 Disconnect/Distribute/Decentralize
BMP 5.1
BMP 5.2
Rooftop disconnection
Disconnection from storm
sewers
Top Ten Stormwater
Management Principles:
-Prevent first,
-Mitigate second.
-Manage as a resource – not a waste!
-Maintain water cycle balance, pre- to post.
-Integrate early into site design process.
-Protect/utilize natural systems (soil, vegetation).
-Manage as close to the source as possible.
-Disconnect. Decentralize. Distribute.
-Slow it down – don’t speed it up.
-Achieve multiple objectives; do as much with as
little as possible.
System Balance….
“…everything is connected to
everything else….”
Stormwater Management:
Making Sure Green is Green
Cahill Associates
Environmental Consultants
West Chester, PA 19382
Cape May, NJ 08204