PERMEABLE INTERLOCKING CONCRETE PAVEMENT (PICP)

DESIGN PROFESSIONALS FACT SHEET

PICP Storm water Benefits• Infiltrates, filters and decreases stormwaterrunoff rate and reduces Total MaximumDaily Load (TMDL)

• LEED®point eligible for Sustainable Sites,Water Efficiency, Materials & Resourcesand lor Innovative Design; Contributes toGreen Globe points

• Meets U.S.Environmental Protection Agency(EPA) stormwater performance criteria asa structural best management practice(BMP) while providing parking, road andpedestrian surfaces

• Helps meet local, state and provincialstormwater drainage design criteria andprovides compliance with the U.S. NationalPollutant Discharge Elimination System(NPDES) regulations

• Provides 100% pervious surface by runoffpassing through small, aggregate-filledopenings between solid high-strengthdurable concrete pavers

• Reduces or eliminates stormwaterdetention and retention ponds, stormsewers, drainage appurtenances andrelated costs

• May be used on sloped sites with properdesign

• The modular concrete units allow forproject phasing; open-graded base andsubbase materials are typically availablelocally.

• Rain water harvesting: capable of storingwater for on-site irrigation or building greywater use

• May be designed with undergroundstormwater storage systems, over manyslower-draining clay soils and in coldclimates

• Processes and reduces pollutants fromvehicular oil drippings

Pollutant removal efficiencies(Compared to impervious pavement runoff)Zinc: 62-88%Copper: 50-89%Total Suspended Solids: 60-90%Total Phosphorous: 65%

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Attractive Durable Environmentally Compliant

•..•• 3 1/8 in. (80 mm) thickpavers with permeablejoints

•..•• Open-graded beddingcourse

Open-graded base course(OGB)

Open-graded subbaseon non-compacted soilsubgrade

Permeable interlocking concrete pavement(PICP) with open-graded base and subbase forinfiltration and storage.

PICP is a costeffective LI Dstormwatermanagementtool

PICP and bioswales work together as LID toolsto increase infiltration at Morton Arboretum inLisle,IL

APPLICATION OPPORTUNITIES• Urban: Office plazas, sidewalk replacement,street tree planting areas, parking lots, parks andoutdoor seating areas

• Suburban: Parking lots, parks, driveways, park-ing bays on roadways, subdivision roads andsidewalks

• Redevelopment Sites: Parking areas, plazasand public spaces, sidewalks and brownfields

LID DESIGN ApPLICATION

350,000 sf (3.2 ha) of PICP at a Burnaby,BCshopping center infiltrates runofffrom roofs.

Permeable Interlocking ConcretePavement Meets Low Impact

Development Goals

• Conserves on-site space: roads, parking,stormwater infi Itration and retentionall combined into the same spacecreating more green space or buildingopportunities

• Preserves wooded areas that wouldotherwise be cleared for stormwaterdetention or retention ponds

• Increases site infiltration that helpsmaintain pre-development runoffvolumes, peak flows and time ofconcentration

• Promotes tree survival and growth

• Contributes to urban heat island reductionthrough evaporation and reflective, lightcolored pavers

• Highly visible, cost effective exemplarydemonstration of cornerstone LIDtechnique for public and privatedevelopment

Design Software Available

New software from ICPI for permeable pavementincorporates research from a range of universityresearch studies.

2 Contact ICPI for further information.

Permeable Interlocking ConcretePavement:A Low Impact Development Tool

PICP supports LID Principles

1. Conserve vital ecological and natural resources:trees, streams, wetlands and drainage courses

2. Minimize hydrologic impacts by reducingimperviousness, conserving natural drainage courses,reducing clearing, grading and pipes

3. Maintain pre-development time of concentration forrunoff by routing flows to maintain travel times anddischarge control

4. Provide runoff storage and infiltration uniformlythroughout the landscape with small, on-sitedecentralized infiltration, detention and retentionpractices such as permeable pavement, bioretention,rain gardens, open swales and roof gardens

5. Educate the public and property owners on runoffand pollution prevention measures and benefits

Concrete Pavers

Permeable Joint MaterialOpen-gradedBedding Course

Underdrain(as required)

Optional GeotextileUnder Subbase

Uncompacted Subgrade Soil

Typical PICP cross section

By eliminating detention pond, the subdivision lay-out conserves trees while 15,000 sf (1500 m+) PICPin the cul-de-sac returns rainfall to the water tablein Glen Brook Green subdivision in Waterford, CT.

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Technical Guidelines

• Pavers conform to ASTM C936 in the U.S. orCSA A231.2 in Canada

• Open-graded crushed stone recommended forall aggregates

• Joint filling stone gradation:ASTM No.8, 87, 89 or 9

• Base gradation: ASTM No. 57• Subbase gradation: ASTM No.2, 3 or 4(railroad ballast)

• Optional geotextile: consult manufacturers forselection

• Soil subgrade: classified per ASTM D2487;tested for permeability per ASTM D3385

• Structural design: ICPI design chart determinesminimum base thickness to support pedestrianand vehicular traffic (see references)

Construction Guidelines

Pavers are deliveredready to place, jointsfilled, compacted andthen are ready for traffic.

Construction Checklist

• No compaction of native soil subgrade -excavate and trim native soil

• Geotextile, drainage pipes and overflow varywith design

• Ensure no sediment from equipment-bornemud on aggregates

• Install and compact aggregate subbase andbase with standard paving equipment

• Specialty equipment used for screedingbedding layer and for mechanical paverinstallation

• Mechanical installation equipment acceleratesconstruction; minimum 5,000 sf (500 m2)/machine/day

• Pavers, non-frozen bedding material & baselsubbase installable in freezing temperaturesover non-frozen soil subgrade

• Paver joints filled with aggregate andcompacted

• No curing time - ready to use uponinstallation; modular construction allows forproject phasing

• Specify experienced ICPI contractors withPICP construction, inspection and detailingskills

Base construction uses locallyavailable materials.

Aggregate base and subbase arespread and compacted; pavers aredelivered ready to install. Afterplacement, joints and/or openingsare filled with small aggregate.Then pavers are compacted.

F - - - ~, ,-,

Mechanical sweeping of fineaggregate into paver joints

Curve Number and Rational MethodRunoff Coefficients

NRCSCurve Numbers (CN) and Rational Methodrunoff coefficients ('C' value) used depend on the soilinfiltration rate, base storage and design storm. Inevery case, PICPyields Significantly lower CN and Cvalues than impervious pavement per the table below:

Land Cover Infilatration Curve RunoffRates Number Co-in./hr (rnrn/hr) CN efficient,

C

Permeable Up to 50 in./ hr 45 - 80 0.00Interlocking (1270 mm/tir) - 0.30Concrete with maintenancePavement 3-4 in.rhr (75-

100 mm/hr) withno maintenance

Impervious o in./hr (0 mm/ 95 - 98 0_90Asphalt or hr) - 0.95ConcretePavement

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PERFORMANCEVolume Reduction

Research has demonstrated that PICPcanreduce runoff as much as 100% from a 3 in.(75 mm) rain event with sandy soil and aminimum 12 in. (300 mm) thick open-gradedaggregate base.

Given regional variations in annual rainstormsand PICP base storage capacities, PICPcanreduce annual runoff between 30% and 80%.Well-maintained PICP can reduce flows by70% to 90% from intense rain events andup to 100% for many storms. This yields acorresponding reduction in runoff pollution.

Peak Flow Reduction and Delay

PICP can reduce peak flow by as much as89%, producing a hydrograph nearer to pre-development conditions. Peak flow is generallyproportional to rainfall intensity. Permeablepavers delay the timing of peak flow runofffrom several hours to several days.

Additional Benefits

• ADA compliant for slip resistance

• Concrete pavers available in variousshapes and colors from local ICPImembers; colored pavers mark lanes andparking spaces

• Simplifies surface and subsurface repairsby reinstating the same paving units; nounsightly patches or weakened pavementcuts

Water Quality Improvement

PICPtreats stormwater by slowing runoff velocities toallow for sedimentation and filtering by aggregates inthe surface openings and base. Oils adhere to smallsoil particles and aggregates and then are digested bybacteria.

FAQSCan PICP be used on clay soils? Yes. Even in claysoils, PICP reduces runoff and helps to capture "firstflush" runoff and reduce pollution.

Can PICP be used to replace convential stormwatermanagement tools such as detention basins? Yes.In both colder and warmer climates, PICPhas been usedto reduce or eliminate the need for conventional stormwa-ter pipe infrastructure, detention basins and drop inlets.

Is Maintaining PICP difficult? No. PICP can be main-tained through street sweeping and vacuuming based ona periodic inspection.

Can PICP be used in cold climates? Yes, PICP hasbeen very successful in many Canadian and northernUnited States applications. It remains stable throughfreezing and thawing cycles.

REFERENCESFerguson, B. K. Porous Pavements. Boca Raton, FL:CRCPress, 2005.

Smith, David R. Permeable Interlocking ConcretePavements: Selection. Design. Construction. Mainte-nance, Washington,DC:ICPI 3rd ed., 2006. www.icpi.org.

For more information pertaining to permeable interlockingconcrete pavement, please visit the Interlocking ConcretePavement Institute (icpi.org) or the Low ImpactDevelopment Center (Iowimpactdevelopment.org).

Other Fact Sheets available for Developers,Municpal Officials and Schools/Universities

Disclaimer: The content of this brochure is intended for use only as a guideline. It is not intendedfor use or reliance upon as an industry standard, certification or specification. ICPI & LIDC makeno promises, representations or warranties of any kind, express or implied, as to the content of thisbrochure. Professional assistance should be sought with respect to the design, specifications andconstruction of each permeable interlocking concrete pavement project.

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INTERLaEKING CONCRETE Email: icpi@icpi.orgPAVEMENT INSnTIJTE ® Web: www.icpi.org

Copyright © 2008 Interlocking Concrete Pavement Institute. All Rights Reserved.

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