Volume-Based Design and
VolumeG
Green
Infrastructure
f
Andy Reese
PE, LEEDLEED-AP
AMEC Earth & Environmental, Inc.
http://www stormh2o com/september 2009/volume based hydrology aspx
http://www.stormh2o.com/september-2009/volume-based-hydrology.aspx
Google it !!
Urban Stormwater Paradigm Shifts
1. “Run it in ditches”
2. “Run it pipes”
3. “Run it in
stormwater pipes”
4. “Keep it from
stormwater p
pipes”
p
5. “Just don’t cause a
flood”
6. “Oh… and don’t
pollute either”
7. “It’s the ecology
stupid!”
stupid!
8. “Water
W e iss water
w e iss
water...shed”
9 “Green
9.
“G
& bear
b
it”
10 “Back
10.
Back to the Future
Future”
Various Approaches

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
Low Impact
Development
p
Multi-objective
Corridors
Integrated Site Design
Better Site Design
Green Infrastructure
Conservation Design
Green Building
Green Technology
Context sensitive
i i design
d i

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
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Sustainable
Development
p
Smart Growth
Eco-Friendly Design
Zero Discharge
Smart Site Development
New Urbanism
LEED designs
Water sensitive urban
design
New EPA Direction – Numeric
Standard
d d
Retain all runoff up to a specified percentile
rainfall event – 85% to 95%
 On
On--site practices must either infiltrate,
evapotranspire or reuse required volume of
evapotranspire,
stormwater
 Might require impervious area treatment
numbers
 Currently being implemented through:

• Section 438 of EISA, Washington DC MS4 permit,
Chesapeake Guidance document
A rational framework for understanding…
biggest flows
to consider
Bankfull
most
destructive
flows
Floodplain Mgmt.
Flooding Protection
most
erosive
flows
Erosion Control
most
polluted
flows
Water Quality
Q critical
Retained
flows
Retention
Floodplain
Extreme
Flood
Protection
Management
Overbank Flood
This looks like Protection
the use of Green Infrastructure
Channel
Protection
Channel Protection
Water Quality
Water Quality
Retention
For the regulator community,
community and thus
for us, this sort of boils down to:

“For
For our program the


right volume must be retained
on site”
site
Or treated… ok, or on another site… ok, or pay up
Whyy should I Retain ?
“…our program…”
What is your primary
driver to retain water?






CSO reduction – as much as feasible given cost/benefit
Reuse - Depends on water/alternative pricing for reuse
Water Supply – little or much depending on water
source and fate of infiltrated water
Groundwater Replenishment – mimic “nature”, replace
withdrawal, control water table
P ll i removall – enoughh to meet pollution
Pollution
ll i targets
Regulatory mandate – what they tell you to do (of
course))
Why should I retain ?
How much should I retain ?
“…the
the right volume…
volume ”
What kind of volumes are we
talking
lki about?
b
1.
2
2.
3.
4.
Federal Facilities & Ches. Bay – 95% storm
Washington DC – 90% storm
W. Virginia – 85% storm (≈
(≈1”)
Then
h a mishmash
ih
h off first
fi flush,
fl h first
fi “X”
“ ”
from DCIA, flow duration, etc.
95% Storm Event
City Atlanta GA
Atlanta, GA Baltimore, MD Boston, MA 95th Percentile Event Rainfall Total (in) 18
1.8
1.6
1.5
City Kansas City MO
Kansas City, MO Knoxville, TN Louisville, KY 95th PercentileEvent
Rainfall Total (in) 17
1.7
1.5
1.5
Buffalo NY
Buffalo, NY Burlington, VT 11
1.1
1.1
Minneapolis MN
Minneapolis, MN New York, NY 14
1.4
1.7
Charleston, WV 1.2
Salt Lake City, UT 0.8
C
Coeur D’Alene, ID D’Al
ID
Cincinnati, OH Columbus, OH Concord, NH
Concord, NH Denver, CO 07
0.7
1.5
1.3
1.3
1.1
Ph
Phoenix, AZ i AZ
Portland, OR Seattle, WA Washington, DC
Washington, DC 10
1.0
1.0
1.6
1.7
Example: Nashville, TN
95% Storm = 1.74”
1 74”
So is that the
So…
“right volume”?
Nature (we think)
159 storms 1.74” ± 20%
(95% storm)
For example for B soil:
87% of storms no runoff
10% had 11-10% volume runoff
2.5% had 1010-20% runoff
0 5% had 20
0.5%
20--30% runoff
Shift
The goal can be stated as
hydrologic
y
g mimicryy
H much
How
h rainfall
i f ll did nature
keep from running off?
OK, do that.
Alternative Criterion: Mimic Annual Capture
50% Tree Canopy Annual Volume Capture Requirement
87% capture
vs. 58% capture
Nature + Man
Big Shift
Why should I Retain ?
How much should I retain ?
What does “retain” mean and how do I do it?
“…must retain …”
Steps to “retain” water?
1.
The very best way is to develop in such a
way that little water runs off – “Better Site
Design”
99% capture
vs. 66% capture
66% capture
t
vs. 96% capture
Steps to “retain” water?
1.
2.
3
3.
The very best way is to develop in such a
way that little water runs off – “Better Site
Design”
After that has been done (or if it is too
late)) then look to other kinds of Green
Infrastructure controls…
If not possible then look for (1) flow
through treatment, (2) off site mitigation,
or (3) payment in lieu of controls
“retain” means…
Evapotranspiration (“up”)
Alternate Use
(“out”)
Infiltration (“down”)
Steps to “Mimic Nature”
0.42” vs. 1.2” Green Infrastructure capture
This means you get
better mimicry at
35% of the G.I.
volume
l
Real World Analysis
“good
good science
science, sound
testing, effective criteria,
proper construction
construction,
periodic maintenance”
Generic Green Infrastructure
Infiltration-based BMPs
1.
•
•
Bioretention
Porous Surfaces
Rainwater Harvesting
and Use
2.
•
•
Cisterns
Ci
Rain Barrels
Evapotranspiration
3
3.
•
•
Trees
Green roofs
Initial
Storage
Volume
Reduction Rate
Infiltration--Based BMPs
Infiltration
It can change the way we look at stormwater controls…
Infiltration
0 mg/l
Treatment
Volume
100 mg/l
BMP
Treatment
40 mg/l
60% removal
½ @ 0mg/l + ½ @ 40mg/l = 20 mg/l
= “80% removal”
It can change our local design criteria…
Nashville, TN
Bioinfiltration
Combination with Flow Through
Rainwater Harvesting and Use
Capture
p
and Use ((re(re-use))

Key
y factors for success of capture
p
and use:
• Having a use for the water
• Being able to use the water
water…fast
fast enough
• Understanding how important not having enough
water
ater is – and ma
maybe
be designing for dr
dry years
ears or
having an alternative source
A 1,000 sf roof will deliver 65.5
gal/day
l/d on average
Farmer’s
Farmer s Market Nashville

58,400 or 74,674 sf roof
area could supply
pp y 145,000
gal/mo based on rulerule-ofofthumb

190,000 g/mo median
demand for irrigation –
but irregular

Supplemented by potable
water
Do Rain Barrels Work?
Evapotranspiration
CSS Area of Nashville




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Can hold about 1.4”
starting dry
4” media
59% annual capture
25 1” Captured
25.1”
C t d or
15,700 gal/yr/1,000sf
112 million ggallons/year
y
removed
Tree Canopy
Nashville Green Infrastructure Tree Canopy Assessment
Tree Canopy Classification
Current Tree Canopy
Potential Tree Canopy
Statistics on Tree Canopy

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Trees intercept or evapotranspire about
60% of annual rainfall
Existing tree canopy = 1,535 acres
Potential tree canopy = 51,773 new
trees, 811 acres
Potential volume removal 13,000
gallons per tree or 660 MG total
But in a drought… (!)
In closing:
1.
2.
3.
There is a rapid change in thinking toward
capt re of storm
capture
stormwater
ater & Green
Infrastructure
Regulations
l i
are written
i
Should blanket regulations be used for
“simplicity” or is there a simple way to
attain simplicity at less “technical cost?”
“continuous
continuous simulation is now nonnon-optional
BUT you can get its power without everyone doing it for every site.”
Actually right now Nashville could
care less about Green Infrastructure