Permeable Surfaces with Concrete Paving
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Permeable Surfaces with Concrete Paving

Jul 10, 2020
Video Length:  1:05:19
Presented By:  Brad Swanson of Unilock

This presentation will inspire architects, engineers, landscape architects, developers, and municipal agencies to choose permeable interlocking concrete pavers for sustainable stormwater solutions. A Best Management Practice under the EPA's National Pollution Discharge Elimination System (NPDES) requirements, the use of permeable pavers is also a recommended construction practice under low-impact development and LEED guidelines.

Concrete pavers were originally designed for heavy-duty applications, making them ideal for streets, roads, parking lots, and even plazas and sidewalks. By allowing water infiltration between units rather than through the pavers themselves, permeable pavers offer a significant advantage over other porous materials because paver composite is not changed. Because they come in a variety of shapes, colors, and textures, these pavers also offer an aesthetic quality. Brad Swanson of Unilock will go over all these benefits and options.

Webinar Contents:

Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)

  • Intro/TOC
  • General Introduction
  • Case Studies
  • Benefits/Systematic Solutions
  • Design Considerations
  • LEED Information
  • Unilock Resources

0:00 – 6:17: Intro/TOC

Brad Swanson's background (3:25)


Unilock background (4:08)


Learning Objectives (5:15):

  • Identify Benefits and Opportunities for Permeable Pavers
  • Analyze the Goals and Criteria for Using a Permeable Paver System
  • List Permeable Paver Materials and Be Able to Design Different Solutions
  • Evaluate and Compare Permeable Pavers to Other Traditional Storm Systems
  • Understand Different Installation Procedures for Permeable Pavers

6:18 – 9:44: General Introduction

Permeable systems overview (6:18)


Permeable paving systems provide (6:45):

  • Water
  • Oxygen
  • Storage detention


Product versatility (7:19)


Design examples (8:32)

9:45 – 16:21: Case Studies

Case studies:

  • Decorative permeable campus spine: Loyola University St. Ignatius Plaza (10:17)
  • Large permeable parking: Guaranteed Rate Field Lot L (largest permeable lot in the U.S., at 265,000 square feet, when installed in 2008) (11:28)
  • Permeable pedestrian plaza: Buckingham Fountain (largest permeable plaza in the U.S. at 235,000 square feet) (14:28)

16:22 – 41:32: Benefits/Systematic Solutions

Permeable pavement facts (16:40):

  • Considered a structural best management practice (BMP) by the EPA's National Pollutant Elimination System (NPDES).
  • Reduction of runoff and runoff temperature, improved water quality, and detention storage in aggregate base.
  • Runoff coefficient will vary. Actual is zero. Typically 0.25 to 0.50. Depending on local jurisdictions, could be as high as 0.95. Infiltration rate varies depending on soil permeability.
  • Curve number (CN value) can also range from 45 to 80. Observed a CN of 91 for permeable paving.
  • Reduces surface runoff
    • Reduced downstream erosion
    • Volume control
  • On-site water use
    • Better quality plant material
    • Preservation of native ecosystems
  • Improves water quality
    • Decreased pollutants
    • Cooler runoff
  • Reduction or elimination of detention pond
    • Significant cost savings in urban areas
  • Intangibles
    • Ease of maintenance


Rapid surface infiltration (18:05)


Volume control (19:06)


Case study: Dominican University (19:06)


Plant material (20:05)

Pavement base allows for water and oxygen to reach the root zone.


Decreased pollutants (21:03)


Reduces detention pond size (22:30)

  • Less impervious coverage
  • Increases usable space
  • Slows first flush erosion efforts


Storage capacity (23:43)


Volume control example (25:35)


MWRD quality (27:00)


MWRD intensity chart (28:20)


Infiltration testing (28:57)


Paver performance and infiltration rates (29:16)

To calculate the minimum infiltration rate, divide the rainfall intensity by the void space ratio.


Historic rainfall data (31:00)


Climate change (31:34)


Winter performance (32:28)


Snow removal (33:41)


Preventative and restorative maintenance (35:04)

Clogging removal equipment:

  • Broom (general removal of surface debris)
  • Shop vacuum (localized problems)
  • Leaf backpack blower/vacuum (cleanup of landscape maintenance)
  • Rotary sweeper brush (general removal of surface crusting)
  • Industrial sweeper vacuum (entire site cleaning)
  • Power washing (severe clogging problem)
  • Remove and reinstall (worst-case scenario)


Street vacuums (37:22)

  • Ideal for large permeable areas
  • Adjustable suction


New equipment (vacuum truck) (38:06):

  • Creates a vortex of air and water equivalent to a category 4 cyclone.
  • Cleaning head features 2 high-pressure water nozzles and 8 turbine blades that rotate at high speed.
  • Swirling air and water scour the surface.
  • Multi-stage filtration system cleans and recycles the recovered wastewater.


Cleaning results (38:20)


Typhoon maintenance system (39:15)

  • Separate power washing and suction devices
  • Requires vacuum truck
  • Great for cleaning small, difficult areas


Maintenance solutions: example (39:39)

How maintenance relates to stormwater intensity:

  • Intersection of decreased performance and rainfall intensity
  • Benchmarks for restorative maintenance


Professional maintenance will provide additional longevity.

41:33 – 53:32: Design Considerations

Design planning (41:40):

  • Goals of the project
  • Site soils
  • Cost expectations
  • Environmental impact
  • Local regulatory requirements


Outlet design options:

  • Outlet at base (for very poor soil) (42:00)
  • Outlet at specified level (for decent soils) (42:27)
  • Outlet at surface (for soils with an extremely high infiltration rate) 42:53)


Structural capacity (43:03)


Granular base and subbase (43:30)


Base-reservoir aggregate (44:13)


Setting bed (and joint fill) (44:48)


Open-graded aggregate scale (45:00)


Common joint fill comparison (45:20)


No joint fill (not recommended) (45:30)


Material specifications (45:57)


Manufacturing: quality control (46:34)


Independent test results (46:59)


Permeable paver styles (47:12)


Texture and face mix technology (49:47)


Components of a successful system (50:24):


Chip setting bed (50:45)


Chip setting bed with DriveGrid (51:10)


Non-permeable system (51:40)


Specialized equipment (51:51)


Project examples in Chicagoland (52:45)


Probable installation cost: comparison (53:00)

53:33 – 54:03: LEED Information

Leed information overview (53:33)


Colors and reflectivity (53:30)

54:04 – end: Unilock Resources

How to secure the pavers from settling (55:05)


Interaction and drainage with clay soils (56:05)


Permeable pavers and heat reduction (permeable pavers or even light-colored pavers will achieve a15- to 20-degree temperature reduction compared with asphalt) (56:30)


Storage capacity (56:52)


Cleaning and prevention of oil buildup (57:19)


Frequency of preventative maintenance (at least once in the fall and once in the spring) (57:40)


Visual clues that preventative maintenance is needed (e.g., low spots that turn into puddles should only pool up for an hour at maximum (58:00)


Turning forces from vehicles – the importance of understanding how the pavers interlock (58:33)


Use of ground-up concrete as base (not recommended because of potential inconsistency) (59:20)


Striping: embedding white pavers into the surface to prevent the need to restripe or spraying a latex paint (59:50)


Issues with limestone-based aggregates (1:01:50)


Preventing efflorescence (1:02:50)

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