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 1
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 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 Hydrodynamic Device Street Cleaning Porous Pavement Biofiltration Rain Barrels/ Tanks Beneficial Uses of Stormwater Grass Swales Drainage Disconnections Catchbasin Cleaning 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 2
Conducted a preliminary evaluation of the downtown Tuscaloosa area that contains the redevelopment sites. Land Use Commercial Residential Institutional Other Area (ac) 72.9 15.7 11.0 10.8 Area (%) 66.0 14.2 10.0 9.77 Separated area into six subareas of several blocks each and conducted detailed field surveys and modeling for each land use. This is one subarea. TOTAL 110 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. 80 60 Directly connected roofs Landscaping Driveways Calculated Benefits of Various Roof Runoff Controls (compared to typical directly connected residential pitched roofs) Annual roof runoff volume reductions Birmingham, Alabama (55.5 in.) Seattle, Wash. (33.4 in.) Phoenix, Arizona (9.6 in.) 40 20 Streets Directly connected paved parking areas 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 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. Flat roofs instead of pitched roofs Cistern for reuse of runoff for toilet flushing and irrigation (10 ft. diameter x 5 ft. high) Planted green roof (but will need to irrigate during dry periods) Disconnect roof drains to loam soils Rain garden with amended soils (10 ft. x 6.5 ft.) 13 66 75 84 87 21 67 77 87 25% 88% 84% 91% 96% 3
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 Green(ish) Roof for Evapotranspiration of Rain Falling on Building (Portland, OR) Recent Bioretention Retrofit Projects in Commercial and Residential Areas in Madison, WI Rain water tanks to capture roof runoff for reuse (Heathcote, Australia) 4
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 4 5
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) 6
116 ft 75 ft TSS: 10 mg/l Date: 10/11/2004 Large parking areas, convenience stores, and vehicle maintenance facilities are usually considered critical source areas and require runoff treatment before infiltration or surface discharge. TSS: 20 mg/l 25 ft TSS: 30 mg/l 6 ft 3 ft 2 ft TSS: 63 mg/l TSS: 35 mg/l Head (0ft) TSS: 102 mg/l TSS: 84 mg/l Example grass filter monitoring results, Tuscaloosa, AL Flow Rate (gpm per acre pavement) Percent of Annual Flow Treated (Atlanta 1999) 450 400 350 300 250 200 150 50 0 90 80 70 60 50 40 30 20 10 0 Flow distribution for typical Atlanta rain year 0 20 40 60 80 Percent of Annual Flow Less than Flow Rate (Atlanta 1999) 10 0 Treatment Flow Rate (gpm per acre of pavement) 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 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 7
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 Treatment Flow Rate Changes during 10 Month Monitoring Period of Prototype UpFlo TM Filter Test site drainage area, Tuscaloosa, AL (anodized aluminum roof, concrete and asphalt parking areas; total of 0.9 acres) 8
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, mg/l and 50 mg/l Flow (gpm) HydroInternational, Ltd. 25 20 15 10 5 0 Pelletized Peat, Activated Carbon, and Fine 300 Sand y = 2.0238x 0.8516 R 2 = 0.9714 200 0 5 10 15 20 Headloss (inches) Suspended Soilds (mg/l) 600 500 400 0 Influent Conc. Effluent Conc. High Flow 500 Mid Flow 500 Low Flow 500 High Flow 250 Mid Flow 250 Low Flow 250 High Flow Mid Flow Low Flow High Flow 50 Mid Flow 50 Low Flow 50 Currently being installed for full-scale testing in Tuscaloosa, AL) Installation of fullsized UpFlow Filter at Tuscaloosa for long-term monitoring Constituent and units Particulate solids (mg/l) Phosphorus (mg/l) TKN (mg/l) Cadmium (µg/l) Copper (µg/l) Lead (µg/l) Zinc (µg/l) Filtration Performance Reported irreducible concentrations (conventional highlevel stormwater treatment) 10 to 45 0.2 to 0.3 0.9 to 1.3 3 15 12 37 Effluent concentrations with treatment trains using sedimentation along with sorption/ion exchange <5 to 10 0.02 to 0.1 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 9
% Runoff Reduction 40% 35% 30% 25% 20% 15% 10% 5% Street cleaning and bioretention only in $8,947, 3.6% Bioretention in commercial and institutional $29,497, 20.1% Street cleaning and bioretention in all land uses $55,251, 23.8% Green roofs in commercial and institutional $55,551, 13.6% Street cleaning, bioretention and green roofs in all land uses $107,528, 35.4% Street cleaning and bioretention in all land uses plus wet pond at outlet $92,155, 25.7% $144,432, 37.3% 0% $0 $20,000 $40,000 $60,000 $80,000 $,000 $120,000 $140,000 $160,000 Annualized Values of all Costs ($) 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) % TSS Mass Reduction % 90% 80% 70% 60% 50% Calculated annualized total life cycle costs and TSS reductions for different stormwater controls (110 acre downtown Tuscaloosa, AL, example) $92,155, 90.7% Street cleaning and bioretention in all land uses plus wet pond at outlet Annualized Values of all Costs ($) $144,432, 91.8% Street cleaning, bioretention and green roofs in all land uses plus wet pond at outlet 40% Street cleaning, Street cleaning bioretention and and bioretention green roofs in all 30% in all land uses Bioretention in commercial $55,251, 27.2% $107,528, 30.3% and institutional 20% Street cleaning and $29,497, 16.8% bioretention 10% only in residential Green roofs in commercial and $8,947, 6.1% $55,551, 1.6% 0% $0 $20,000 $40,000 $60,000 $80,000 $,000 $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) 10