Steve Maakestad Project Engineer

1. Green Stormwater Infrastructure Design: Lessons Learned in Philadelphia Steve Maakestad Project Engineer September 19, 2013

2. Green Stormwater Infrastructure Tools • Bioretention Basins • Rain Gardens • Bioswales • Stormwater Wetlands • Green Streets – Urban Landscaping • Stormwater Tree Trenches • Planter Boxes • Curb Extensions • Downspout Disconnection • Porous Pavement • Green Roofs • Rain Barrels • Flow-Through Planters • Disconnection of Impervious

3. Importance of GSI • Means of meeting CSO abatement/surface water quality goals • Flood Relief, Adapting to Climate Change • Social, Environmental and Economic Benefits • EPA issued an Integrated Municipal Stormwater and Wastewater and Planning Approach Framework on June 5th. • GSI is considered one of the four overarching principles to be used in development of integrated plans for Clean Water Act obligations including MS4 permits and Consent Orders.

4. Philadelphia’s Sewer System • Streams were enclosed starting in mid-19th Century • 118 Miles of the original 283 miles remain • 60% Combined Sewer • 54% of Philadelphia is impervious • Average of 65 Rain Events Annually • 3 Wastewater Treatment Plants • 175 Regulating Chambers and 164 CSO Outfalls

5. Philadelphia Green Cities, Clean Waters Program • 25-Year Budget • GSI: $1.67B • WWTP Upgrades: $345M • Adaptive Management: $420M • 9,564 Green Acres • Green Acre = 1” Capture on 1 Acre of Impervious Surface = IC (Impervious Cover) x WP (1” to 1.5” rainfall)

6. Green Cities, Clean Waters Program • Philadelphia currently has about 13.5 to 16 Billion Gallons of CSO in average year • Green Cities, Clean Waters Program is estimated to reduce that by about 8 Billion Gallons • Alternative: Storage Tunnels or Storm Sewer Separation • In addition to infrastructure program, Parcel-Based Billing Program implemented 2-years ago • For every $1 invested – they get a $2 return on their investment based on the Triple Bottom Line Analysis • Program aligns with several other planning policies for the City

7. Triple Bottom Line Analysis • TBL = Additional benefits, outside of control of CSOs & associated water quality improvements gained from the investment • TBL accounting = Environmental & Social Performance in addition to Cost - Total Benefits Evaluated Against Financial Investment: • Carbon Footprint Reduction • Energy Savings/Offset Climate Change • Green Job Creation Reduces Social Cost of Poverty • Air Quality Improvement from Mature Trees (Avoided Asthma • Attacks) • Ecosystem & Habitat Restoration • Property Value Added • Recreation - creates sense of community • Heat Stress Mortality Reduction • Flooding Reduction After 40 Years, the Philly Green City, Clean Waters Program Estimated to Create More Than $2.2 Billion of Social Benefits

8. GSI Design Completion Process • Planning  Opportunities Analysis/Site Selections • Stakeholder Coordination • Survey/Base Plan Development/Infiltration Testing • Conceptual System Sizing and Design  Tree Locations reviewed by Parks and Recreation • Detailed Design of Systems (Plans, Profiles, Sections, Typical Details) • Utility Coordination • Bid Tabulation and Specification Completion • Bidding & Construction

9. Location Selection Key Factors in Location: Ideal Locations: • Schools • Parks • Public Property • Churches • Recreation Centers • Redevelopment • Minimal Utility Conflicts • Public/Local Interest • Optimal CSO Reduction Benefit (CSO Sewershed) • Lack of Existing Trees • Visibility

10. Green Streets Phase III (Northern Liberties) • Pilot Project started in 2009 included: • Stormwater Tree Trenches • Planter Boxes built into Stormwater Trenches • Modular Storage Stormwater Trenches • Planted Curb Extension/Bumpout with Overflow into Stormwater Tree Trenches • Subsurface Stone Trenches • ADA Curb Ramps • Curb Cuts • Traffic Turning Analysis • Crosswalk Safety

11. Standard Design and Contract Specification Development TO STORMWATER SYSTEM FROM UNDERDRAIN • Dual Trap InletExample Detail TO SEWER STEEL DIVERSION PLATE 6 FT. X 2 FT. GRATE INLET DUAL TRAP INLET AT SUMP LOCATION CONCRETE WEIR WALL

12. 40 Mil Impermeable Membrane Utility Conflicts and Groundwater Concerns Utility Crossings Tree Pit Box Cleanout Anti-seep collar for break in trench

13. Cobbs Creek Parkway Traffic IslandCascading Rain Gardens • Cascading Rain Gardens with Short Decorative Weir Wall Collects ~¾ acre Impervious Surface. • 24” Stone Storage Beneath 18” of Planting Soil with Micropools • Use of Trench Drains and Inlets for Drainage Across the Street • Native, Low Maintenance Plantings • Overflow Control Structure redirects portion of drainage currently directed CSS to local storm sewer

14. Bioretention – Planter Boxes and Curb Extensions • Cast Iron Trench Drains and Fencing are Expensive • Concrete Aprons for more Efficient Drainage Collection • Tire Guards • Splash Blocks Needed • Filters for Dome Risers

15. Stormwater Tree Trench Optional Planter Boxes providing Pre-Treatment Green Inlet Benefits: • Low Cost per Square Foot • Relatively Low Maintenance – observation well inspection, emptying debris filters /inlet cleaning, and occasional jetting of piping • Reduced Heat Island Effect • Water Quality Benefit and Transpiration • Achieves 1” to 1.5” Storage Goal and Loading Ratio Requirement (~1:10) • Fits within the sidewalk (saves surface real estate) Tree Pit Stone Storage up to 4+ feet in depth Perforated HDPE with Cleanouts

16. Stormwater Tree Trench • Slow Release Orifice (½” to 1-1/2” in Diameter) • 24-72 Hour Drain Down Time UNDERDRAIN CAP PROFILE VIEW

17. Green Inlets/Pretreatment • Modified Inlet Grate • Inlet Insert – Manufactured devices • Inlet Sump – Outlet pipe is about 32” above bottom of inlet • Inlet Trap – Prevents Floatables from entering the pipe • 8” Pipe or greater is typically used to facilitate Vactor Hose

18. Benefits of Incorporating Green Streets Into Water and Sewer Projects • One-Time Impact on Community • Minimize Additional Street Restoration Costs • Potentially Reduce Required Capacity of Proposed Sewers • Flooding • CSO Reduction • Once the Survey/Base Plan is Completed – Watersheds Reviews for GSI Opportunities

19. Key Challenges of Green Streets Program • Utility conflicts (Cross-Street Inlet Pipes) • Adjacent Buildings (Basements) • Cost per Acre Managed • Interdepartmental Standardization • Design Parameters • Release Rate • Loading Ratio • Volume

20. Other Lessons Learned • Inspector’s Trained to Ensure E&S Controls are adequate • ADA Ramp Locations Factored into Design • Payment Methods (Lump Sum per system vs. Unit Cost) • Drawing standardization • Efficiency in design • Ease of review • Used for As-Builts • Used for GIS

21. Highlights of PWD’s GSI Monitoring Plan • Stormwater Inflow • Soil Moisture Storage • System Storage • Evapotranspiration • Infiltration • Groundwater Monitoring • Bypass and Return Flow

22. Typical Maintenance Needs • Trash and Debris Removal • Sediment Removal • Weeding and Pruning • Product Testing • Structural Repairs (Inlets, Cleanouts) • Erosion and Sediment Control • Reseeding and Watering • CCTV Underground Pipe and Vactor Cleaning

23. Integrated Watershed Management • Green Stormwater Infrastructure • Wet Weather Treatment Improvements • I and I Removal – Lining Program/Lateral repair and Replacement • Stream Habitat Restoration and Fish Passage Program • Storm Sewer Separation; MS4 • Conveyance/Storage Tunnels, Gray Features • Flood Relief Projects • Water and Sewer Asset Management

24. Questions? Stephen C. Maakestad, PE, LEED AP 215-399-1161 stephen.maakestad@hatchmott.com

25. Philadelphia Green Streets Project Experience • Planning Estimate of 400,000 gallons CSO prevented per Green Acre • Range around $0.55 per average annual gallon of CSO prevented

26. Green Streets in West Philadelphia at Longstreth School • 4 Planter Boxes Collect Drainage through Trench Drains • Ornamental Black Iron Fencing Surrounds Planter Boxes • Each Planter Box contains an Overflow Grate to Direct Stormwater into Subsurface Storage Trenches • Native Plantings to be Maintained by Elementary School • Underdrain Will Slowly Drain Entire System and Discharge to Existing Sewer.