Design, Construction and Maintenance of Permeable Pavements Case Studies and Technical Resources Robert Bowers, P. Eng.

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1 Design, Construction and Maintenance of Permeable Pavements Case Studies and Technical Resources Robert Bowers, P. Eng. Source: CH2M Hill The Presenter Robert Bowers, P.Eng., LEED GA Director of Engineering at Interlocking Concrete Pavement Institute (ICPI) Chantilly, VA Thanks to David Smith, ICPI and Bethany Eisenberg, VHB 2014 VBH & ICPI. All rights reserved. 1

2 Presentation Outline Introduction to Permeable Pavements Types Why Permeable Pavement? Map 21 Case studies Design System Components Concerns Clogging, cleaning, cold climates, structural ASCE Permeable Pavements Report Other Resources Source CH2MHill Porous Asphalt (PA) Reduced fines over an open-graded aggregate base Sister to asphalt-treated permeable base & open-graded friction course Source: NAPA 2014 VBH & ICPI. All rights reserved. 2

4 MAP-21 October 2012 SEC RESEARCH AND TECHNOLOGY DEVELOPMENT AND DEPLOYMENT. (a) IN GENERAL. Section 503 of title 23, United States Code, is amended to read as follows: 503. Research and technology development and deployment (C) CONTENTS Research and technology activities carried out under this paragraph may include (XIX) technology transfer and adoption of permeable, pervious, or porous paving materials, practices, and systems that are designed to minimize environmental impacts, stormwater runoff, and flooding and to treat or remove pollutants by allowing stormwater to infiltrate through the pavement in a manner similar to predevelopment hydrologic conditions. Why Permeable Pavement? Road infrastructure now reduces drainage upsizing costs, helps relieve sewer capacities & local flooding Supports NPDES permit compliance for state & local road agencies Supports emerging TS4 permits for road agencies Mitigates CSOs in older urban areas 772 cities under court consent decrees to implement green infrastructure e.g., green alley & streets Creates consistent technical framework for DOTs & locals Decision paths for design guidelines, construction & maintenance Assures performance for projects 2014 VBH & ICPI. All rights reserved. 4

5 NACE /14/2014 Before After Source: City of Warrenville, IL Case Studies Main Street Warrenville, IL miles 125,000 sf 3 in. concrete pavers 24 in. base/subbase Manages 10-yr storm Eliminated flooding $4.7 million Machine installed paving units Perforated storm pipe for infiltration & drainage in road center Source all photos: City of Warrenville, IL 2014 VBH & ICPI. All rights reserved. 5

6 18 24 in. thick open-graded aggregate for water storage & vehicular support City of Shoreview, MN 7 in. pervious concrete ¾ mile (79,000 sf) road Reduce pollutants to nearby Lake Owassa $1.4 million Source all photos: City of Shoreview, MN Source: Oregon Asphalt Pavement Association Strong Rd Salem, OR 2006 New 180 home subdivision 1.7 mi. streets & alleys (~200,000 sf) 1½ in. OGFC + 3 in. ATPB 19 in. base/subbase 90% runoff reduction Saved $250,000! 2014 VBH & ICPI. All rights reserved. 6

7 Design System Components Uses: walkways, parking lots, green alleys, low-speed/low-volume roads, road shoulders Key Hydrologic Design Factors Subgrade Infiltration Double ring infiltrometer test Use avg. infiltration rate Apply safety factor for clogging & construction compaction Source all photos: CH2M Hill Test pits Source all photos: CH2MHill Test pit Portable soil infiltration device 2014 VBH & ICPI. All rights reserved. 7

8 Key Structural Design Factors Uncompacted or compacted soil subgrade Strength characterization of saturated soils via California Bearing Ratio (96 hr soaked) Resilient Modulus M r R-value Modulus of subgrade reaction, k Pavement surface layer strengths Base/subbase aggregate strengths Source: R. Roseen Structural Capacity Design Permeable pavements must be adequately designed to support anticipated structural loads Traffic load bearing capacity can be increased by: Thicker base/subbase Stiffened base/subbase w/ cement or asphalt stabilization Thicker PA or PC surface or paver thickness Using fibers & additives in PC and PA mixtures to increase strength Subgrade stabilization with cement or lime (typ. in low infiltration soils) Impermeable liner 2014 VBH & ICPI. All rights reserved. 8

9 Site Design Considerations Underlying soils Permeability Stability Contamination Slope Groundwater Contributing area run-on and surrounding land use Other constraints Utilities Foundations Private wells Septic systems Designing for Permeable Pavement Goals Stormwater quantity control Stormwater quality control Groundwater recharge Land preservation Reduced surface ponding, spray Reduced runoff thermal impact Reduced ice build-up/salt use Source: CH2M Hill Source: John Kevern, UMKC 2014 VBH & ICPI. All rights reserved. 9

10 Permeable Pavement Surfaces Porous asphalt (PA) Permeable interlocking concrete pavement (PICP) Pervious concrete (PC) Grid pavement (plastic or concrete) Permeable Pavement System Choker Course Level out surface material PICP & Grid, required PA ATPB or choker course PC, optional Reservoir Course Temporary storage of infiltrated water Structural support to surface layers Underdrains (optional) Drainage of the reservoir 2014 VBH & ICPI. All rights reserved. 10

11 Typical Permeable System Configurations 1. Full-infiltration 2. Partial-infiltration 3. No-infiltration Full-infiltration System Generally used with highly permeable soils All captured water infiltrates into the soils 2014 VBH & ICPI. All rights reserved. 11

12 Partial-infiltration System Used with less permeable soils i.e., cannot infiltrate captured water within hrs Some water infiltrates into underlying soils Underdrains used to drain excess filtered water No-infiltration System Impermeable liner (geomembrane) to prevent infiltration into soils Filtered water exits system via underdrain Discharge control & water quality benefits Little volume reduction 2014 VBH & ICPI. All rights reserved. 12

13 Common Concerns Despite increasing use, all applications are often met with resistance Concerns over Clogging/Failure Maintenance Use in cold climates Durability and surface failures Clogging Sources Wind Deposition Adjacent Land Use Source: Eban Bean, ECU Vehicular Traffic Source: Eban Bean, ECU Construction Activities Source: Eban Bean, ECU 2014 VBH & ICPI. All rights reserved. 13

14 Clogging Impacts Initial rates >500 in./hr Pavement surface traps sediment/fines Some surface clogging occurs over time Factors: Traffic load Proximity to sediment Surrounding land use Pavement age Clogged surface infiltration rates remain high May be partially if not fully rehabilitated Clog Prevention Siting/construction staging to reduce run-on Preventive maintenance annually or biannually No winter sanding Even with no maintenance infiltration continues (>5 in./hr) Can restore rates Properly installed/maintained systems should not clog to failure Source: R. Roseen 2014 VBH & ICPI. All rights reserved. 14

15 Maintenance Routine maintenance typ. 1 to 2 times/yr Site inspections or infiltration testing at surface recommended to determine need for increase or decrease frequency of maintenance Source: Bill Hunt, NCSU Source: Bill Hunt, NCSU Maintenance Vacuum Sweeping Regenerative air vacuum sweeper Routine surface cleaning Removes loose sediment, leaves, etc. Most common ~$1000/acre True vacuum sweeper 2X more powerful Restorative cleaning for highly clogged surfaces Narrower suction Source: Elgin Sweeper 2014 VBH & ICPI. All rights reserved. 15

16 Cold Climates Success stories in cold climates Porosity of base materials allow expansion of water without cracking/ frost heaves Infiltration of snowmelt during warm days No ponding and refreezing on surface Cold climate recommendations No sanding Limit use of deicers on pervious concrete (particularly during first year) Limit placement of PC/PA during cold or hot weather Source: John Kevern Durability Examples of Surface Failures Lack of Edge Restraints Improper Mix/Curing Source: Eban Bean, ECU Design Loads Exceeded Source: Eban Bean, ECU Excessive Turning Source: Kevin Earley, Nicolock Paving Source: UNH Stormwater Center 2014 VBH & ICPI. All rights reserved. 16

17 Coming Soon Permeable Pavements ASCE Committee Report Fact sheets Checklists Permeable pavement design information Porous asphalt Pervious concrete Permeable interlocking concrete pavers Grids Maintenance Standards, guide specifications, and modeling methods Research needs Source: VHB Design and Use of the Manual Digital format only Hyperlink between chapters & Tables of Contents Multi-level functionality Easy navigation Graphics & figures explain design concepts simply Source: VHB 2014 VBH & ICPI. All rights reserved. 17

18 Chapter 1: Introduction and Design Considerations Common to All Permeable Pavements Regulatory requirements Site conditions Hydrologic & structural design Sustainable design credits Installation & maintenance overview Summary checklist Chapter 1: Site Design Checklists 2014 VBH & ICPI. All rights reserved. 18

19 Pavements Chapter 2: Porous asphalt Chapter 3: Pervious concrete Chapter 4: PICP Chapter 5: Grid pavers Chapter 6: Other All have: Fact sheets Unique design considerations Recommended outline for specifications Chapters 2 to 6: Fact Sheets 2014 VBH & ICPI. All rights reserved. 19

20 Chapter 7: Achieving Success and Avoiding Failures with Permeable Pavements Planning and site selection Design Construction Operation & maintenance Source: CH2M Hill Chapter 8: Maintenance Annual inspection Annual maintenance Checklists 2014 VBH & ICPI. All rights reserved. 20

21 Chapter 9: Hydrological and Hydraulic Design Method Resources Hydrology & hydraulics Water quality Modeling tools Agency modeling requirements Chapter 10 Research Needs Improved specifications Validated hydrologic/hydraulic performance data & modeling techniques Validated, reliable structural design procedures Refined pollutant removal performance data & modeling techniques Installation & maintenance requirements Initial cost, life cycle costs & life cycle assessment data Long-term evaluation studies Proven cold climate specs for pervious concrete Clogging/hydraulic failure & rehabilitation information 2014 VBH & ICPI. All rights reserved. 21

22 Appendix A: Common Concerns Regarding Permeable Pavements Fact Sheet Clogging Costs Maintenance Cold climate Durability Soil constraints Groundwater constraints Spills Slopes Appendix B: Design and Performance Summary Tables Overview Summary tables Pavement applications General pavement properties Installation and material specifications Permeable pavements surface cost comparison Water quality performance summary Hydrologic performance summary 2014 VBH & ICPI. All rights reserved. 22

23 Appendix C: Standards, Testing Methods and Resources Standards testing methods Pervious concrete Porous asphalt Permeable pavers Appendix D: Glossary Source: Eban Bean, ECU Acronyms Key words, terms, phrases Other Resources Design Manuals & Software NCHRP Task 82 Report: Road Shoulders with Stone Reservoirs ICPI ACPA/NRMCA NAPA 2014 VBH & ICPI. All rights reserved. 23