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Effective Best Management Practices in Effective Best Management Practices in Urban AreasUrban Areas

Chad ChristianCity of Tuscaloosa, AL

Robert PittUniversity 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 5,000square feet shall use site planning, design, construction, andmaintenance strategies for the property to maintain or restore,to the maximum extent technically feasible, the predevelopmenthydrology 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

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Many types of runoff monitoring have been used to calibrate and verify WinSLAMM, from small source areas to outfalls.

Outfall

Drainage System

Land Uses (multiple source areas)

Large Landscaped Areas

Freeway Lanes/Shoulders

Other Impervious Areas

Other Pervious Areas

Small Landscaped Areas

Undeveloped Areas

Streets/Alleys

Sidewalks/Walks

Driveways

Playgrounds

Unpaved Parking/Storage

Paved Parking/Storage

Roof

Drainage Dis-

connect-ions

Catch-basin

Clean-ing

Grass Swales

Beneficial Uses of Storm-water

Rain Barrels/ Tanks

Porous Pave-ment

Biofilt-ration

Street Clean-

ing

Wet Detent-

ion

Hydro-dynamic Device

WinSLAMM Source Area, Land Use, Drainage System, and Outfall Controls 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”

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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.

100110TOTAL

9.7710.8Other

10.011.0Institutional14.215.7Residential66.072.9Commercial

Area (%)Area (ac)Land Use

Conducted a preliminary evaluation of the downtown Tuscaloosa area that contains the redevelopment sites.

Separated area into six subareas of several blocks each and conducted detailed field surveys and modeling for each land use. This is one subarea.

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20

40

60

80

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Streets

Directly connected paved parking areas

Driveways

Landscaping

Directly connected roofs

Major sources of suspended solids in the drainage area for different sized rains. Fairly consistent pattern because of the large amount of impervious surfaces in the drainage basin and the highly efficient drainage system.

Calculated Benefits of Various Roof Runoff Controls (compared to typical directly connected residential pitched roofs)

100

87

77

67

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Seattle, Wash. (33.4 in.)

87

84

75

66

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Birmingham, Alabama (55.5 in.)

96%Rain garden with amended soils (10 ft. x 6.5 ft.)

91%Disconnect roof drains to loam soils

84%Planted green roof (but will need to irrigate during dry periods)

88%Cistern for reuse of runoff for toilet flushing and irrigation (10 ft. diameter x 5 ft. high)

25%Flat roofs instead of pitched roofs

Phoenix, Arizona (9.6 in.)

Annual roof runoff volume reductions

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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

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Land and Water, Sept/Oct. 2004

97% Runoff Volume Reduction

Runoff volume benefits of many rain gardens capturing roof runoff in neighborhood

Stormwater filters adjacent to buildings treating roof runoff (Melbourne, Australia and Portland, Oregon)

Neenah Foundry Employee Parking Lot Biofilter, Neenah, WI

WDNR, 2004 infiltration standard 1004

Typical Biofiltration Facility

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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.

No Underdrain

Conventional Underdrain Restricted Underdrain

78% runoff volume reduction77% part. solids reduction31% peak flow rate reduction

74% part. solids reduction for complete 1999 LAX rain year

76% runoff volume reduction for complete 1999 LAX rain year

33% runoff volume reduction85% part. solids reduction7% peak flow rate reduction

49% runoff volume reduction91% part solids reduction80% peak flow rate reduction

Small grass filters/biofilters for commercial area runoff (Melbourne, Australia) Tree planter biofilters along sidewalk (Melbourne, Australia)

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Head (0ft)

Date: 10/11/2004

2 ft

25 ft

6 ft

3 ft

116 ft75 ft

TSS: 10 mg/L

TSS: 20 mg/L

TSS: 30 mg/L

TSS: 35 mg/L

TSS: 63 mg/L

TSS: 84 mg/L

TSS: 102 mg/L

Example grass filter monitoring results, Tuscaloosa, AL

Large parking areas, convenience stores, and vehicle maintenancefacilities are usually considered critical source areas and require runoff treatment before infiltration or surface discharge.

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250

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350

400

450

0 20 40 60 80 100

Percent of Annual Flow Less than Flow Rate (Atlanta 1999)

Flow

Rat

e (g

pm p

er a

cre

pave

men

t)

0

10

20

30

40

50

60

70

80

90

100

10 100 1000

Treatment Flow Rate (gpm per acre of pavement)

Perc

ent o

f Ann

ual F

low

Tre

ated

(Atla

nta

1999

)

Continuous Simulation can be used to Determine Needed Treatment Flow Rates:- 90% of the annual flow for SE US conditions is about 170 gpm/acre pavement (max about 450).

- 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.

Flow distribution for typical Atlanta rain year

Chamber Filtering Systems

Hydrodynamic Separator

Commonly used underground treatment units for critical source areas

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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

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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.

Pelletized Peat, Activated Carbon, and Fine Sand

y = 2.0238x0.8516

R2 = 0.9714

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5

10

15

20

25

0 5 10 15 20

Headloss (inches)

Flow

(gpm

)

Performance Plot for Mixed Media on Suspended Soilds for Influent Concentrations of 500 mg/L, 250mg/L, 100 mg/L and 50 mg/L

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100

200

300

400

500

600

Influent Conc. Effluent Conc.

Susp

ende

d So

ilds

(mg/

L)High Flow 500Mid Flow 500

Low Flow 500

High Flow 250Mid Flow 250

Low Flow 250

High Flow 100Mid Flow 100

Low Flow 100High Flow 50

Mid Flow 50Low Flow 50

HydroInternational, Ltd.

Currently being installed for full-scale testing in Tuscaloosa, AL)

Installation of full-sized UpFlow Filter at Tuscaloosa for long-term monitoring

Filtration Performance

<2037Zinc (µg/L)3 to 1512Lead (µg/L)3 to 1515Copper (µg/L)0.13Cadmium (µg/L)0.80.9 to 1.3TKN (mg/L)

0.02 to 0.10.2 to 0.3Phosphorus (mg/L)

<5 to 1010 to 45Particulate solids (mg/L)

Effluent concentrations with treatment trains using sedimentation along with sorption/ion exchange

Reported irreducible concentrations (conventional high-level stormwater treatment)

Constituent and units

CFD Modeling to Calculate Scour/Design VariationsWe 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

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$8,947, 3.6%

$55,551, 13.6%

$55,251, 23.8%

$29,497, 20.1%

$92,155, 25.7%

$107,528, 35.4%

$144,432, 37.3%

0%

5%

10%

15%

20%

25%

30%

35%

40%

$0 $20,000 $40,000 $60,000 $80,000 $100,000 $120,000 $140,000 $160,000

Annualized Values of all Costs ($)

% R

unof

f Red

uctio

n

Street cleaning and bioretention only in

Green roofs incommercialand institutional

Bioretention incommercialand institutional

Street cleaning and bioretention in all land uses

Street cleaning and bioretention in all land uses plus wet pond at outlet

Street cleaning, bioretention and green roofs in all land uses Street cleaning, bioretention

and green roofs in all land uses plus wet pond at outlet

Calculated annualized total life cycle costs and runoff reductions for different stormwater controls (110 acre downtown Tuscaloosa, AL, example)

$55,551, 1.6%$8,947, 6.1%

$29,497, 16.8%

$92,155, 90.7%

$55,251, 27.2% $107,528, 30.3%

$144,432, 91.8%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $20,000 $40,000 $60,000 $80,000 $100,000 $120,000 $140,000 $160,000

Annualized Values of all Costs ($)

% T

SS M

ass

Red

uctio

n

Street cleaning andbioretentiononly in residential Green roofs in

commercial and

Bioretention incommercialand institutional

Street cleaning and bioretention in all land uses

Street cleaning and bioretention in all land uses plus wet pond at outlet

Street cleaning, bioretention and green roofs in all

Street cleaning, bioretention and green roofs in all land uses plus wet pond at outlet

Calculated annualized total life cycle costs and TSS reductions for different stormwater controls (110 acre downtown Tuscaloosa, AL, example)

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.

Pitt, et al. (2000)

• 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

Combinations of Controls Needed to Meet Many Stormwater Management Objectives