8. Bioinfiltration and Evapotranspiration Controls in WinSLAMM v 10 Robert Pitt, John Voorhees, and Caroline Burger PV & Associates LLC Using WinSLAMM for Effective Stormwater Management Penn 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

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 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 33% runoff volume reduction 85% part. solids reduction 7% peak flow rate reduction 49% runoff volume reduction 91% part solids reduction 80% 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

Additional Output Other Output Options   Time step detail   Irreducible concentration   Particulate reduction   Stage outflow   Stochastic seepage rates Biofilter Water Balance  Stochastic seepage rates  Evapotranspiration

Kansas City’s CSO Challenge  Combined sewer area: 58 mi 2  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 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.

Reductions in Annual Flow Quantity from Directly Connected Roofs with the use of Rain Gardens (Kansas City CSO Study Area)

January42July357 February172August408 March55September140 April104October0 May78November0 June177December0 Household water use (gallons/day/house) from rain barrels or water tanks for outside irrigation to meet ET requirements:

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 (ft 3 ) # of 35 gallon rain barrels tank height size required if 5 ft D (ft) tank height size required if 10 ft D (ft) ft of storage is needed for use of 75% of the total annual runoff from these roofs for irrigation. With 945 ft 2 roofs, the total storage is therefore 113 ft 3, 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.

Annual Runoff Reductions from Paved Areas or Roofs for Different Sized Rain Gardens for Various Soils

Clogging Potential for Different Sized Rain Gardens Receiving Roof Runoff Clogging not likely a problem with rain gardens from roofs

Clogging 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: sir/2008/5008/pdf/sir_ 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 ControlRunoff Volume, inches Expected Change (being monitored) Pre-development1.3 No Controls6.7515% increase Swales + Pond/wetland + Infiltration Basin 1.578% decrease, compared to no controls 15% increase over pre-development

Water Year Construction Phase Rainfall (inches) Volume Leaving Basin (inches) Percent of Volume Retained (%) 1999Pre-construction % 2000Active construction % 2001Active construction % 2002 Active construction (site is approximately 75% built-out) % Monitored Performance of Controls at Cross Plains Conservation Design Development WI DNR and USGS data