Effective Best Management Practices in
Urban Areas
Chad Christian
City of Tuscaloosa, AL
Robert Pitt
University of Alabama
Tuscaloosa, AL
“Energy Independence and Security Act of
2007” signed into Law on Dec. 19, 2007
• Title IV (“Energy Savings in Building and Industry”), Subtitle C
(“High Performance Federal Buildings”) Sec. 438 (“Storm
Water Runoff Requirements For Federal Development
Projects”):
• “The sponsor of any development or redevelopment project
involving a Federal facility with a footprint that exceeds 5,000
square feet shall use site planning, design, construction, and
maintenance strategies for the property to maintain or restore,
to the maximum extent technically feasible, the predevelopment
hydrology of the property with regard to the temperature, rate,
volume, and duration of flow.”
• This new provision requires much more attention to controlling
runoff volume, in addition to other hydrologic features.
Conservation Design Approach for
New Development
• Better site planning to maximize resources of site
• Emphasize water conservation and water reuse on
site
• Encourage infiltration of runoff at site but prevent
groundwater contamination
• Treat water at critical source areas and encourage
pollution prevention (no zinc coatings and copper,
for example)
• Treat runoff that cannot be infiltrated at site
A lot of stormwater flow and quality data has
been collected during the past several decades
It is important to compare these observations with model
assumptions and to use this data for calibration and verification
Many types of runoff monitoring have been used to calibrate
and verify WinSLAMM, from small source areas to outfalls.
WinSLAMM Source Area, Land Use, Drainage System, and Outfall Controls
Hydrodynamic
Device
Roof
Paved Parking/Storage
Unpaved Parking/Storage
Playgrounds
Driveways
Sidewalks/Walks
Streets/Alleys
Undeveloped Areas
Small Landscaped Areas
Other Pervious Areas
Other Impervious Areas
Freeway Lanes/Shoulders
Large Landscaped Areas
Land Uses (multiple source
areas)
Drainage System
Outfall
Wet
Detention
Street
Cleaning
Biofiltration
Porous
Pavement
Rain
Barrels/
Tanks
Beneficial
Uses of
Stormwater
Grass
Swales
Catchbasin
Cleaning
Drainage
Disconnections
Probability
distribution of rains
(by count) and
runoff (by depth).
Central Alabama Rain
Condition:
<0.5”: 65% of rains
(10% of runoff)
0.5 to 3”: 30% of rains
(75% of runoff) We
therefore need to focus on
these rains!
3 to 8”: 4% of rains
(13% of runoff)
>8”: <0.1% of rains
(2% of runoff)
0.5”
3”
8”
Conducted a preliminary
evaluation of the
downtown Tuscaloosa
area that contains the
redevelopment sites.
Land Use
Area (ac)
Area (%)
Commercial
72.9
66.0
Residential
15.7
14.2
Institutional
11.0
10.0
Other
10.8
9.77
TOTAL
110
100
Soils are mostly hydrologic group B which is classified as silt, loam, and
silt-loam, having typical infiltration rates of about 0.5 in/hr, although most
of the soils are highly disturbed and will need to be restored.
Separated area into six
subareas of several
blocks each and
conducted detailed field
surveys and modeling for
each land use. This is
one subarea.
100
Directly connected roofs
80
Landscaping
60
Driveways
40
Streets
20
Directly connected paved parking areas
0
0.0
0.5
Paking Paved Con.
1.0
1.5
2.0
Paved Playground
2.5
3.0
3.5
Pitch Roofs Drained to Imp.
Streets
Sidewalks
Paveddrainage
Con.
Driveways
Paved Con.sized
Major sources
of suspended solids
in the
area for
different
Flat Roofs Drained to Imp.
Large Turf
Flat Roofs Drained to Perv.
Pitch Roofs Drained to Perv.
Back Landscape
Front Landscape
Undeveloped
Unpaved Paking
Sidewalks
Discon.
rains. Fairly
consistent pattern because
of the large amount
of Paved
impervious
surfaces in the drainage basin and the highly efficient drainage system.
4.0
Calculated Benefits of Various Roof Runoff
Controls (compared to typical directly
connected residential pitched roofs)
Annual roof runoff volume
reductions
Birmingham, Seattle, Phoenix,
Alabama
Wash.
Arizona
(33.4 in.) (9.6 in.)
(55.5 in.)
Flat roofs instead of pitched roofs
13
21
25%
Cistern for reuse of runoff for toilet
flushing and irrigation (10 ft.
diameter x 5 ft. high)
66
67
88%
Planted green roof (but will need to
irrigate during dry periods)
75
77
84%
Disconnect roof drains to loam soils
84
87
91%
Rain garden with amended soils (10
ft. x 6.5 ft.)
87
100
96%
Green(ish) Roof for Evapotranspiration of Rain Falling on
Building (Portland, OR)
Recent results showing green roof runoff
benefits compared to conventional
roofing (data from Shirley Clark, Penn
State – Harrisburg)
Greater than 65% volume reductions
due to ET
Rain water tanks to capture
roof runoff for reuse
(Heathcote, Australia)
Recent Bioretention
Retrofit Projects in
Commercial and
Residential Areas in
Madison, WI
Runoff
volume
benefits of
many rain
gardens
capturing
roof runoff in
neighborhood
97% Runoff Volume Reduction
Land and
Water,
Sept/Oct.
2004
Stormwater filters
adjacent to buildings
treating roof runoff
(Melbourne, Australia
and Portland, Oregon)
Neenah Foundry Employee Parking Lot Biofilter, Neenah, WI
Typical Biofiltration Facility
WDNR, 2004 infiltration standard 1004
Example Biofilter Performance
and Design using WinSLAMM
0.75 inch rain with complex inflow
hydrograph from 1 acre of pavement.
2.2% of paved area is biofilter surface,
with natural loam soil (0.5 in/hr infilt. rate)
and 2 ft. of modified fill soil for water
treatment and to protect groundwater.
Conventional Underdrain
33% runoff volume reduction
85% part. solids reduction
7% peak flow rate reduction
No Underdrain
78% runoff volume reduction
77% part. solids reduction
31% peak flow rate reduction
76% runoff volume reduction for complete
1999 LAX rain year
74% part. solids reduction for complete 1999
LAX rain year
Restricted Underdrain
49% runoff volume reduction
91% part solids reduction
80% peak flow rate reduction
Small grass filters/biofilters for commercial area runoff (Melbourne,
Australia)
Tree planter biofilters along sidewalk (Melbourne, Australia)
Date: 10/11/2004
116 ft
TSS: 10 mg/L
75 ft
TSS: 20 mg/L
25 ft
TSS: 30 mg/L
6 ft
3 ft
2 ft
TSS: 35 mg/L
TSS: 63 mg/L
Head (0ft)
TSS: 84 mg/L
TSS: 102 mg/L
Example grass filter
monitoring results,
Tuscaloosa, AL
Large parking areas, convenience stores, and vehicle maintenance
facilities are usually considered critical source areas and require runoff
treatment before infiltration or surface discharge.
Continuous Simulation
can be used to
Determine Needed
Treatment Flow Rates:
Flow Rate (gpm per acre pavement)
450
Flow distribution for
typical Atlanta rain
year
400
350
300
250
200
150
100
- 90% of the annual flow for
50
0
0
20
40
60
80
100
Percent of Annual Flow Less than Flow Rate (Atlanta 1999)
Percent of Annual Flow Treated (Atlanta 1999)
100
SE US conditions is about
170 gpm/acre pavement
(max about 450).
90
80
70
60
50
40
30
20
10
0
10
100
Treatment Flow Rate (gpm per acre of pavement)
1000
- treatment of 90% of
annual runoff volume would
require treatment rate of
about 100 gpm/acre of
pavement. More than three
times the treatment flow rate
needed for NW US.
Hydrodynamic Separator
Chamber Filtering
Systems
Commonly used underground treatment units
for critical source areas
Multi-Chambered Treatment Train (MCTT) for
stormwater control at large critical source areas
Milwaukee, WI, Ruby Garage Maintenance Yard MCTT
EPA-funded SBIR2 Field Monitoring
Equipment for UpFlow Filter, Tuscaloosa,
AL
Test site drainage area,
Tuscaloosa, AL
(anodized aluminum
roof, concrete and
asphalt parking areas;
total of 0.9 acres)
Treatment Flow Rate Changes during 10 Month
Monitoring Period of Prototype UpFloTM Filter
Upflow filter insert for
catchbasins
Able to remove particulates and
targeted pollutants at small
critical source areas. Also traps
coarse material and floatables in
sump and away from flow path.
Performance Plot for Mixed Media on Suspended Soilds for Influent
Concentrations of 500 mg/L, 250mg/L, 100 mg/L and 50 mg/L
600
Mid Flow 500
Pelletized Peat, Activated Carbon, and Fine
Sand
Suspended Soilds (mg/L)
500
HydroInternational, Ltd.
Low Flow 500
High Flow 250
400
Mid Flow 250
Low Flow 250
300
High Flow 100
y = 2.0238x 0.8516
R2 = 0.9714 200
25
Flow (gpm)
High Flow 500
20
Mid Flow 100
Low Flow 100
High Flow 50
100
15
Mid Flow 50
10
Low Flow 50
0
5
Influent Conc.
0
0
5
10
Headloss (inches)
15
20
Effluent Conc.
Currently being installed for full-scale
testing in Tuscaloosa, AL)
Installation of fullsized UpFlow Filter
at Tuscaloosa for
long-term monitoring
Filtration Performance
Constituent and
units
Reported irreducible
concentrations
(conventional highlevel stormwater
treatment)
Particulate solids
(mg/L)
Phosphorus
(mg/L)
TKN (mg/L)
Cadmium (g/L)
Copper (g/L)
Lead (g/L)
Zinc (g/L)
10 to 45
Effluent
concentrations with
treatment trains using
sedimentation along
with sorption/ion
exchange
<5 to 10
0.2 to 0.3
0.02 to 0.1
0.9 to 1.3
3
15
12
37
0.8
0.1
3 to 15
3 to 15
<20
CFD Modeling to Calculate Scour/Design Variations
We are using CFD (Fluent 6.2 and Flow 3D) to determine
scour from stormwater controls; results being used to expand
WinSLAMM analyses after verification with full-scale physical
model
This is an example of the effects of the way that water enters
a sump on the depth of the water jet and resulting scour
40%
$144,432, 37.3%
Street cleaning,
bioretention and green
roofs in all land uses
35%
Street cleaning, bioretention
and green roofs in all land uses
plus wet pond at outlet
$107,528, 35.4%
% Runoff Reduction
30%
25%
Bioretention in
commercial
and institutional
Street cleaning
and bioretention
in all land uses
Street cleaning
and bioretention in all land uses
plus wet pond at outlet
$92,155, 25.7%
$55,251, 23.8%
20%
$29,497, 20.1%
15%
Green roofs in
commercial
and institutional
$55,551, 13.6%
10%
Street cleaning
and bioretention
only in
residential
$8,947, 3.6%
5%
Calculated annualized total life
cycle costs and runoff reductions
for different stormwater controls
(110 acre downtown Tuscaloosa,
AL, example)
0%
$0
$20,000
$40,000
$60,000
$80,000
$100,000
Annualized Values of all Costs ($)
$120,000
$140,000
$160,000
100%
Calculated annualized
total life cycle costs and
TSS reductions for
different stormwater
controls (110 acre
downtown Tuscaloosa,
AL, example)
90%
80%
% TSS Mass Reduction
70%
60%
50%
40%
Bioretention in
commercial
and institutional
20%
Street cleaning and
bioretention
only in residential
10%
Street cleaning, bioretention
and green roofs in all land uses
plus wet pond at outlet
Street cleaning
and bioretention in all land
uses plus wet pond at outlet
Street cleaning,
bioretention and
green roofs in all
Street cleaning
and bioretention
in all land uses
30%
$144,432, 91.8%
$92,155, 90.7%
$55,251, 27.2%
$107,528, 30.3%
$29,497, 16.8%
Green roofs in
commercial and
$55,551, 1.6%
$8,947, 6.1%
0%
$0
$20,000
$40,000
$60,000
$80,000
$100,000
Annualized Values of all Costs ($)
$120,000
$140,000
$160,000
Appropriate Combinations of Controls
• No single control is adequate for all problems
• Only infiltration reduces water flows, along with soluble
and particulate pollutants. Only applicable in conditions
having minimal groundwater contamination potential.
• Wet detention ponds reduce particulate pollutants and
may help control dry weather flows. They do not
consistently reduce concentrations of soluble pollutants,
nor do they generally solve regional drainage and
flooding problems.
• A combination of bioretention and sedimentation
practices is usually needed, at both critical source areas
and at critical outfalls.
Combinations of Controls Needed to Meet Many
Stormwater Management Objectives
• Smallest storms should
be captured on-site for
reuse, or infiltrated
• Design controls to treat
runoff that cannot be
infiltrated on site
• Provide controls to
reduce energy of large
events that would
otherwise affect habitat
• Provide conventional
flooding and drainage
controls
Pitt, et al. (2000)