8. Bioinfiltration and Evapotranspiration Controls in WinSLAMM v 10

8. Bioinfiltration and Evapotranspiration Controls

in WinSLAMM v 10

Robert Pitt, John Voorhees, and Caroline BurgerPV & Associates LLC

Using WinSLAMM for Effective Stormwater ManagementPenn State Great Valley

March 13, 2012

Stormwater Constituents that may Adversely Affect Infiltration Device Life and

Performance Sediment (suspended solids) will clog device Major cations (K+, Mg+2, Na+, Ca+2, plus various heavy

metals in high abundance, such as Al and Fe) will consume soil CEC (cation exchange capacity) in competition with stormwater pollutants.

An excess of sodium, in relation to calcium and magnesium (such as in snowmelt), can increase the soil’s SAR (sodium adsorption ratio), which decreases the soil’s infiltration rate and hydraulic conductivity.

Ground Water Mounding“Rules of Thumb”

Mounding reduces infiltration rate to saturated permeability of soil, often 2 to 3 orders of magnitude lower than infiltration rate.

Long narrow system (i.e. trenches) don't mound as much as broad, square/round systems

Modeling Notes Biofilter routing is performed

using the Modified Puls Storage – Indication Method.

Time increments are established by the model, start at 6 minutes

Yield reductions due to runoff volume reduction through infiltration and filtering through engineered soil

• Inflow rate – Low•All runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level below ground rises

Control Practice Overview

Control Practice Overview

• Inflow rate – Moderate•All runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level below ground rises

•Water discharges through underdrain

Control Practice Overview

• Inflow rate – High•Some runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level above ground rises

•Water level below ground rises

•Water discharges through underdrain

Control Practice Overview

• Inflow rate – High•Some runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level above ground rises

•Water level below ground rises

•Water discharges through underdrain and above ground

Control Practice Overview

• Inflow rate – Moderate•Some runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level above ground falls

•Water level below ground falls

•Water discharges through underdrain

Control Practice Overview

• Inflow rate – Moderate•All runoff flows through engineered soil

•Native soil restricts below ground discharge

•Water level above ground zeros out

•Water level below ground falls

•Water discharges through underdrain

Control Practice Overview

• Inflow rate – Zero•No runoff•Native soil restricts below ground discharge

•Water level below ground falls

•Water discharges through underdrain, eventually only through native soil

Underdrain Effects on Water Balance

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 (3” perforated pipe) Underdrain

Restricted Underdrain

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

76% runoff volume reduction for complete 1999 LAX rain year

74% part. solids 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

Biofilter Geometry

Biofilter Datum is always zero ft.

Biofilter Data Entry Form

Biofilter Geometry

Outflow Structure

Information

Biofilter Data Entry Form

Biofilter Data Entry Form

Biofilter Data Entry Form

Additional Output

Other Output Options Time step detail Irreducible concentration Particulate reduction Stage outflow Stochastic seepage rates

Biofilter Water Balance

Biofilter Water Balance Performance Summary, by EventBioF Source Area Number

Rain Number

Rain Depth (in)

Time (Julian Date)

Maximum BioF Stage (ft)

Minimum BioF Stage (ft)

Event Inflow Volume (ac-ft)

Event Hydr Outflow (ac-ft)

Event Infil Outflow (ac-ft)

Event Evap Outflow (ac-ft)

Event Cistern Outflow (ac-ft)

Event Orifice Outflow (ac-ft)

Event Total Outflow (ac-ft)

Event Flow Balance (ac-ft)

Volume Reduction Fraction

Solids Reduction Fraction

7 1 0.01 0 0.12 0 0 0 0 0 0 0 0 0 1 07 2 0.05 31 0.57 0 0.007 0 0.001 0 0 0.006 0.007 0 0.183 07 3 0.1 59 0.71 0 0.015 0 0.002 0 0 0.013 0.015 0 0.095 07 4 0.25 90 1.2 0 0.042 0 0.002 0 0 0.041 0.042 0 0.043 07 5 0.5 120 2.03 0 0.084 0 0.002 0 0 0.082 0.084 0 0.024 07 6 0.75 151 2.46 0 0.125 0 0.002 0 0 0.122 0.125 0 0.018 07 7 1 181 2.5 0 0.165 0.007 0.002 0 0 0.156 0.165 0 0.014 07 8 1.5 212 2.52 0 0.249 0.034 0.003 0 0 0.213 0.249 0 0.01 07 9 2 243 2.52 0 0.335 0.066 0.003 0 0 0.266 0.335 0 0.008 07 10 2.5 273 2.53 0 0.416 0.087 0.003 0 0 0.326 0.416 0 0.008 07 11 3 304 2.52 0 0.497 0.097 0.004 0 0 0.396 0.497 0 0.008 07 12 4 334 2.53 0 0.661 0.149 0.004 0 0 0.507 0.661 0 0.007 0

Stochastic seepage rates Evapotranspiration

Kansas City’s CSO Challenge

Combined sewer area: 58 mi2

Fully developed Rainfall: 37 in./yr 36 sewer overflows/yr by rain > 0.6 in; reduce

frequency by 65%. 6.4 billion gal overflow/yr, reduce to 1.4 billion

gal/yr Aging wastewater infrastructure Sewer backups Poor receiving-water quality

20

744 acres Distributed storage

with “green infrastructure” vs. storage tanks

Need 3 Mgal storage Goal: < 6 CSOs/yr

Kansas City Middle Blue River Outfalls

1/26/2009

Kansas City’s Original

Middle Blue River Plan with CSO

Storage Tanks

Adjacent Test and Control Watersheds

Kansas City 1972 to 1999 Rain Series

Water Harvesting Potential of Roof Runoff

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0.000.200.400.600.801.001.201.401.601.802.00

Evapotranspiration per Month (typical turfgrass)

ET

(inc

hes/

wee

k)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

0.4

0.8

1.2

1.6

2

Monthly Rainfall

Rai

nfal

l (in

ches

/wee

k)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0.000.200.400.600.801.001.201.401.601.802.00

Supplemental Irrigation Needs per Month (typical turfgass)

Irri

gatio

n ne

eds (

inch

es/w

eek)

Irrigation needs for the landscaped areas surrounding the homes were calculated by

subtracting long-term monthly rainfall from the regional

evapotranspiration demands for turf grass.

0.1 1 10 1000

10

20

30

40

50

60

70

80

90

100

Percent of roof area as rain gardenPerc

ent r

educ

tion

in a

nnua

l roo

f run

off

Reductions in Annual Flow Quantity from Directly Connected Roofs with the use of Rain Gardens

(Kansas City CSO Study Area)

January 42 July 357February 172 August 408March 55 September 140April 104 October 0May 78 November 0June 177 December 0

Household water use (gallons/day/house) from rain barrels or water tanks for outside irrigation

to meet ET requirements:

0.001 0.01 0.1 10

10

20

30

40

50

60

70

80

90

100

Rain barrel/tank storage (ft3 per ft2 of roof area)

Perc

enta

ge r

educ

tion

in

annu

al r

oof r

unof

f

Reductions in Annual Flow Quantity from Directly Connected Roofs with the use of Rain Barrels and

Water Tanks (Kansas City CSO Study Area)

rain barrel storage per house (ft3)

# of 35 gallon rain barrels

tank height size required if 5 ft D (ft)

tank height size required if 10 ft D (ft)

0 0 0 04.7 1 0.24 0.060

9.4 2 0.45 0.1219 4 0.96 0.2447 10 2.4 0.60

118 25 6.0 1.5470 100 24 6.0

0.12 ft of storage is needed for use of 75% of the total annual runoff from these roofs for irrigation. With 945 ft2 roofs, the total storage is therefore

113 ft3, which would require 25 typical rain barrels, way too many! However, a relatively small water tank (5 ft D and 6 ft H) can also be used.

Examples from plans prepared by URS for project streets.

Construction will be completed in spring and summer of 2012.

0.1 1 10 1001

10

100

clay (0.02 in/hr)

silt loam (0.3 in/hr)

sandy loam (1 in/hr)

Rain Garden Size (% of drainage area)

Red

uctio

n in

Ann

ual I

mpe

rvio

us

Are

a R

unof

f (%

)Annual Runoff Reductions from Paved Areas or Roofs

for Different Sized Rain Gardens for Various Soils

0.1 1 10 10010

100

1000

10000

years to 10 kg/m2Linear (years to 10 kg/m2)

Rain Garden Size (% of roof area)

Yea

rs to

Clo

ggin

gClogging Potential for Different Sized Rain

Gardens Receiving Roof Runoff

Clogging not likely a problem with rain gardens from roofs

0.1 1 10 1001

10

100

1000

years to 10 kg/m2Linear (years to 10 kg/m2)years to 25 kg/m2

Rain Garden Size (% of paved parking area)

Yea

rs to

Clo

ggin

gClogging Potential for Different Sized Rain

Gardens Receiving Paved Parking Area Runoff

Rain gardens should be at least 10% of the paved drainage area, or receive significant pre-treatment (such as with long grass filters or swales, or media filters) to prevent premature

clogging.

Available at: http://pubs.usgs.gov/sir/2008/5008/pdf/sir_

2008-5008.pdf

The most comprehensive full-

scale study comparing advanced

stormwater controls available.

Parallel study areas, comparing test with control site

Reductions in Runoff Volume for Cedar Hills (calculated using WinSLAMM

and verified by site monitoring)Type of Control Runoff

Volume, inches

Expected Change (being monitored)

Pre-development 1.3

No Controls 6.7 515% increase

Swales + Pond/wetland + Infiltration Basin

1.5 78% decrease, compared to no

controls15% increase over pre-development

Water Year

ConstructionPhase

Rainfall(inches)

Volume Leaving

Basin (inches)

Percent of Volume

Retained (%)

1999 Pre-construction 33.3 0.46 99%

2000 Active construction 33.9 4.27 87%

2001 Active construction 38.3 3.68 90%

2002

Active construction (site is

approximately 75% built-out)

29.4 0.96 97%

Monitored Performance of Controls at Cross Plains Conservation Design

Development

WI DNR and USGS data