Steve Maakestad Project Engineer

g

Steve MaakestadProject Engineer

September 19, 2013

Green Stormwater Infrastructure Design: Lessons Learned in Philadelphia

g 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

Green Stormwater Infrastructure Tools

gImportance 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.

gPhiladelphia’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

gPhiladelphia 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)

Green Streets; 38%

Green Schools; 2%

Green Public Facil-ities; 3%Green Parking; 5%Green Open Space; 10%

Green Industry, Business, Com-

merce, and Insti-tutions; 16%

Green Alleys, Driveways and Walkways; 6%

Green Homes; 20%

gGreen 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

gTriple 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

gGSI Design Completion Process1. Planning Opportunities

Analysis/Site Selections 2. Stakeholder Coordination3. Survey/Base Plan

Development/Infiltration Testing

4. Conceptual System Sizing and Design Tree Locations reviewed by Parks and Recreation

5. Detailed Design of Systems (Plans, Profiles, Sections, Typical Details)

6. Utility Coordination7. Bid Tabulation and Specification

Completion8. Bidding & Construction

gLocation Selection

· 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

Key Factors in Location: Ideal Locations:

gGreen 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

gStandard Design and Contract Specification Development

· Dual Trap Inlet Example Detail

STEEL DIVERSION PLATE

TO STORMWATER SYSTEMFROM UNDERDRAIN

TO SEWER

CONCRETE WEIR WALL

6 FT. X 2 FT. GRATE INLET

DUAL TRAP INLET ATSUMP LOCATION

gUtility Conflicts and Groundwater Concerns

Cleanout

Anti-seep collar for break in trench

Utility Crossings

Tree Pit Box

40 Mil Impermeable Membrane

gCobbs 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

gBioretention – 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

gStormwater Tree Trench

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 depthPerforated HDPE with

Cleanouts

Optional Planter Boxes providing Pre-Treatment

Green Inlet

gStormwater Tree Trench

· Slow Release Orifice (½” to 1-1/2” in Diameter)· 24-72 Hour Drain Down Time

PROFILE VIEW

UNDERDRAIN CAP

gGreen 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

gBenefits 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

gKey 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

gOther 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

gHighlights of PWD’s GSI Monitoring Plan

· Stormwater Inflow· Soil Moisture Storage· System Storage· Evapotranspiration· Infiltration· Groundwater Monitoring· Bypass and Return Flow

gTypical 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

gIntegrated 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

gQuestions?

Stephen C. Maakestad, PE, LEED AP

215-399-1161

[email protected]

gPhiladelphia Green Streets Project ExperienceProject Name Construction Cost Green Acres Estimated Annual Volume Stormwater Controlled (Gallons) Linear Feet of City Street

Stormwater Control Measure Type

Northern Liberties Flood Relief Program – Phases IV, V and VI (3

Separate Contracts)(10 Systems)

Green Stormwater Infrastructure Costs

($800,000)Total Flood Relief Projects

Cost($30,000,000)

3.0 2.4 Million 4,020 Infiltration and Slow Release Stormwater Trenches

Green Streets Phase III in Northern Liberties

(6 Systems)$420,000 1.2 1.3 Million 1000

Planter BoxesVegetated Curb Extensions

Infiltration and Slow Release Stormwater Trenches Including

Modular Storage Systems

Green Streets Phase IV in West Philadelphia(12 Systems)

$1,090,000 3.9 4.4 Million 6,740 Infiltration and Slow Release Stormwater Trenches

Green Streets Phase V in West Philadelphia(10 Systems)

$1,170,000 4.8 5.4 Million 5,950Vegetated Stormwater Basins

Planter BoxesInfiltration and Slow Release

Stormwater Trenches

Green Streets FY 2013 in West Philadelphia

(Eastwick-Elmwood Package)14 Systems)

Est. $2,400,000 14.9 16.8Million 8,300 Infiltration and Slow Release Stormwater Trenches, Rain Gardens,

Stormwater Bumpouts

Ellsworth Street, Federal Street and Wharton Street Sewer

Reconstruction and Water Main Relay (3 Systems)

Est. $300,000 1.1 1.1 Million 4,500Rain Garden, Stormwater Infiltration

Trenches

Ontario Street and Glenwood Avenue Water Main Relay

(5 Systems)Est. $300,000 1.0 900,000 4,200 Stormwater Infiltration Trenches

Totals Est. $6,500,000 30 Acres 32.3 Million 35,000 LF 60 Systems Total

Planning Estimate of 400,000 gallons CSO prevented per Green Acre Range around $0.55 per average annual gallon of CSO prevented

gGreen 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.