Permeable Paving: A New Tool for Sustainable Site Development
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Permeable paving is a transformative approach to sustainable site development. Permeable hard surface construction is part of a continuing series of engineering solutions to water management that protects, restores, and mimics the natural water cycle. Permeable paving is an efficient solution for stormwater runoff. It will reduce flooding, increase water infiltration, recharge groundwater and improve water quality.
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Permeable Paving: A New Tool for Sustainable Site Development
- 1. Permeable Paving by Tom Barrett Green Water Infrastructure, Inc. www.ThinkGWI.com Follow on Twitter @TomBarrett_GWI (317) 674-3494 Copyright © Tom Barrett, 2011 All Rights Reserved
- 3. LOW IMPACT SITE DEVELOPMENT
- 5. How Much Rain Falls in Chicago? January - 1.86" Image of Rain Falling February - 1.58" March - 2.59" April - 3.28" May - 3.75" June - 4.08" July - 3.39" August - 3.38" September - 2.91" October - 2.65" November - 2.09" December - 1.88" Total 33.44"
- 6. Thirty Year Average Monthly Rain Fall Chicago (1971 - 2000) 5.00 3.75 Inches 2.50 1.25 0 January February March April May June July August September October November December Month Graph of Chicago Rain Fall
- 7. How Much Water Falls in Chicago? 2,500 sq. ft. Roof January - ,727 gallons 2 Image of Rain Falling February - ,540 2 March - ,130 4 April - 5,735 May - ,268 5 June - 5,657 July - ,470 5 August - ,200 7 September - ,096 5 October - ,223 4 November - 4,691 December - 3,787 Total 6,525 5
- 8. How Much Water Falls in Chicago? ¼ Acre Residential Property January - 1,880 gallons 1 Image of Rain Falling February - 1,065 1 March - 7,990 1 April - 24,982 May - 2,945 2 June - 24,642 July - 3,828 2 August - 1,363 3 September - 2,199 2 October - 8,397 1 November - 20,434 December - 16,496 Total 46,221 2
- 9. How Much Water Falls in Chicago? 3 Acre Commercial Property January - 42,560 gallons 1 Image of Rain Falling February - 32,784 1 March - 15,876 2 April - 299,783 May - 75,344 2 June - 295,710 July - 85,934 2 August - 76,358 3 September - 66,383 2 October - 20,764 2 November - 245,203 December - 197,954 Total 2,954,654
- 10. How Much Water Falls in Chicago? City Block (660’ x 660’ – 10 acres) January - 75,195 gallons 4 February - 42,610 4 March - 19,581 7 April - 999,267 May - 17,805 9 June - 985,690 July - 53,105 9 August - ,254,515 1 September - 87,936 8 October - 35,873 7 November - 817,335 December - 659,842 Total 9,848,756
- 11. How Much Water is in Rain Event? ¼” Rain ½” Rain 1” Rain 2,500 ft. sq. 390 gallons 779 gallons 1,558 gallons Roof ¼ Acre 1,697 3,994 67,789 Residential Property 3 Acre 20,366 40,731 135,770 Commercial Property Chicago City 67,885 135,770 271,540 Block
- 12. Landscape Ecology Size the landscape to the 80% of the average rain water production. – Roof Runoff – Hardscape Runoff Balancing rain water to landscape creates a functional landscape that utilizes the site’s water production.
- 13. Stormwater Mitigation Stormwater Mitigation Stormwater Mitigation Stormwater Mitigation Stormwater Mitigation
- 14. Stormwater Mitigation – Collection runoff near the source – Slow it down – Soak it in – Filter it – Apply it to the landscape – Create habitats
- 15. Peak Flow (1 Acre Site) Grass Field Roof 1 Year Storm 1.4 cfs 4.3 cfs 2 Year Storm 2.1 cfs 5.4 cfs 10 Year Storm 4.3 cfs 8.0 cfs 25 Year Storm 5.7 cfs 9.5 cfs 100 Year Storm 8.0 cfs 12.0 cfs cfs – cubic feet per second
- 16. Peak Flow (1 Acre Site) Grass Field Roof 1 Year Storm 10.5 gps 32.2 gps 2 Year Storm 15.7 gps 40.4 gps 10 Year Storm 32.2 gps 59.8 gps 25 Year Storm 42.6 gps 71.1 gps 100 Year Storm 59.8 gps 89.8 gps gps – gallons per second
- 17. Peak Flow (1 Acre Site) Grass Field Roof 1 Year Storm 630 gpm 1,932 gpm 2 Year Storm 942 gpm 2,424 gpm 10 Year Storm 1,932 gpm 3,588 gpm 25 Year Storm 2,556 gpm 4,266 gpm 100 Year Storm 3,588 gpm 5,388 gpm gpm – gallons per minute
- 18. Peak Flow (2,500 sq. ft. Roof) Grass Field Roof 1 Year Storm 0.08 cfs 0.25 cfs 2 Year Storm 0.12 cfs 0.31 cfs 10 Year Storm 0.25 cfs 0.46 cfs 25 Year Storm 0.33 cfs 0.55 cfs 100 Year Storm 0.46 cfs 0.69 cfs cfs – cubic feet per second
- 19. Peak Flow (2,500 sq. ft. Roof) Grass Field Roof 1 Year Storm 0.60 gps 1.85 gps 2 Year Storm 0.90 gps 2.32 gps 10 Year Storm 1.85 gps 3.43 gps 25 Year Storm 2.44 gps 4.08 gps 100 Year Storm 3.43 gps 5.15 gps gps – gallons per second
- 20. Peak Flow (2,500 ft. sq. Roof) Grass Field Roof 1 Year Storm 36 gpm 111 gpm 2 Year Storm 54 gpm 139 gpm 10 Year Storm 111 gpm 206 gpm 25 Year Storm 147 gpm 245 gpm 100 Year Storm 206 gpm 309 gpm gpm – gallons per minute
- 21. Change in Peak Runoff Flow Before and after Development 300% 225% 150% 75% 0% 1 Year Storm Year Storm Year Storm Year Storm Year Storm 2 10 25 100 Stormwater Effects of Urbanization
- 22. Detention and Volume Control Stormwater Mitigation Detention Underneath Elimination of Detention Ponds
- 23. How Much Water ? Rainfall Surface Area Water Volume 1/4” 43,560 ft2 6,800 gallons 1/2” 43,560 ft2 13,600 gallons 1” 43,560 ft2 27,200 gallons
- 24. Base Storage Capacity Storage Base Depth Surface Area Void Space Capacity 12” 43,560 ft2 40% 130,300 gallons 18” 43,560 ft2 40% 195,500 gallons 24” 43,560 ft2 40% 260,700 gallons
- 25. Infiltration Replenishes the Groundwater Supply Currently 50% of our Drinking Water In the Future 80% of our Drinking Water
- 26. Soil Infiltration Rates Soil Texture Infiltration (in/hour) Sand 8.30” Loamy Sand 2.41” Sandy Loam 1.02” Loam 0.52” Silt Loam 0.27” Sandy Clay Loam 0.17” Clay Loam 0.09” Silty Clay Loam 0.09” Clay 0.06”
- 27. Improved Water Quality Removes Suspended Solids Removes Phosphorus, Nitrogen, and Metals Removes Harmful Pollutants - Oil Water Polishing - the final step in cleaning
- 28. Pollutant Removal Pollutant Median Pollutant Removal* Suspended Solids 95% Phosphorus 70% Nitrogen 51% Metals 99% *Infiltration Trenches & Porous Pavement
- 31. Design Considerations Rainfall Intensity Rainfall Duration Runoff Coefficient is Zero Underdrain for Soil Infiltration Rates of less than 1/2” per Hour Release Rate
- 32. strength, no- units instead ver options, he Americans ents, and allows ration. 2 4 .8 ead of sand, 1 d additional ting bed 0” (12,700 mm ) 3 7 t be avoided as 4 9 5 6 8 r ASTM No. 2, 6 ness. Installation y on sites with m ) is required for ust be designed ature, the ASTM r runoff in the also has an
- 33. UNILOCK PERMEABLE INTERLOCKING Nine Components of a Highly Successful Components of Permeable 1 CONCRETE PAVER With various aesthetically pleasing colors and textures, creative choices are not compromised by function. Permeable Interlocking Concrete Pavers (PICPs) are the most durable of any porous pavement Permeable Pavement Pavement material. Unilock’s minimum 8,500 psi (57 MPa), high-strength, no- slump concrete allows water to infiltrate between paver units instead of through the material. The joint sizes vary between paver options, ranging from 0.25” (6 mm ) to 0.5” (13 mm ), which meet the Americans with Disabilities Act specifications for permeable pavements, and allows a minimum of 100” (2,540 mm ) per hour of surface infiltration. 2 1) Pavement 3 SETTING BED AGGREGATE – ASTM NO. 8 2) Joint Aggregate Using the 0.25” (6 mm ) crushed, angular, chip stone, instead of sand, provides a smooth leveling course for placing pavers and additional 1 structural interlocking of the PICPs. Unlike sand, the setting bed aggregate allows for rapid water infiltration with over 500” (12,700 mm ) 3 7 3) Setting Bed per hour through the 40 percent void-space. Sand must be avoided as a setting bed in a PICP application. 4 Aggregate 5 9 4) SUBBASE AGGREGATE – ASTM NO. 2 5 Base Aggregate Subsoil conditions will dictate the necessity of this larger ASTM No. 2, 8 6 crushed, angular, open-graded subbase aggregate thickness. Installation of such material will provide increased structural stability on sites with 5) Subbase poor soil conditions. A minimum thickness of 8” (203 mm ) is required for effective performance. Subbase aggregate thickness must be designed to sufficiently support anticipated loads. As an added feature, the ASTM Aggregate No. 2 subbase aggregate temporarily detains stormwater runoff in the 40 percent void-space of the material. The ASTM No. 2 also has an infiltration rate of over 500” (12,700 mm ) per hour. 7 EDGE RESTRAINT 8 UNDERDRAIN 9 GEOTEXTILE FABRIC
- 34. Pavement • Pavers • Concrete • Asphalt • Single-sized Aggregate • Resin Bound
- 35. Joint Aggregate • Pavers only • Initial Filter • 1/4” crushed, angular, chip stone • ASTM No. 8
- 36. Setting Bed Aggregate • Used in all systems • Smooth Leveling Course • No Sand • ASTM No. 8
- 37. Base Aggregate • Used when subsoil conditions allow • Minimum thickness 4” • ASTM No. 57
- 38. Subbase Aggregate • Not always necessary • Dictated by Subsoil Conditions • Used for additional structural stability • ASTM No. 2
- 39. Subgrade • Existing Soil • Percolation • California Bearing Ratio • Penetrometer
- 40. Edge Restraint • Vitally Important • Concrete Curb for Vehicular Traffic • Plastic may be Sufficient for Non- vehicular areas.
- 41. Underdrain Pipe • Subsoil Permeablity • Detention Requirements • Release Rates • Not Always Necessary
- 42. Geotextile Fabric • Based Upon Existing Soil Characteristics • Between Subsoil and Base Aggregate
- 43. UNILOCK PERMEABLE INTERLOCKING Nine Components of a Highly Successful Components of Permeable 1 CONCRETE PAVER With various aesthetically pleasing colors and textures, creative choices are not compromised by function. Permeable Interlocking Concrete Pavers (PICPs) are the most durable of any porous pavement Permeable Pavement Pavement material. Unilock’s minimum 8,500 psi (57 MPa), high-strength, no- slump concrete allows water to infiltrate between paver units instead of through the material. The joint sizes vary between paver options, ranging from 0.25” (6 mm ) to 0.5” (13 mm ), which meet the Americans with Disabilities Act specifications for permeable pavements, and allows a minimum of 100” (2,540 mm ) per hour of surface infiltration. 2 1) Pavement 3 SETTING BED AGGREGATE – ASTM NO. 8 2) Joint Aggregate Using the 0.25” (6 mm ) crushed, angular, chip stone, instead of sand, provides a smooth leveling course for placing pavers and additional 1 structural interlocking of the PICPs. Unlike sand, the setting bed aggregate allows for rapid water infiltration with over 500” (12,700 mm ) 3 7 3) Setting Bed per hour through the 40 percent void-space. Sand must be avoided as a setting bed in a PICP application. 4 Aggregate 5 9 4) SUBBASE AGGREGATE – ASTM NO. 2 5 Base Aggregate Subsoil conditions will dictate the necessity of this larger ASTM No. 2, 8 6 crushed, angular, open-graded subbase aggregate thickness. Installation of such material will provide increased structural stability on sites with 5) Subbase poor soil conditions. A minimum thickness of 8” (203 mm ) is required for effective performance. Subbase aggregate thickness must be designed to sufficiently support anticipated loads. As an added feature, the ASTM Aggregate No. 2 subbase aggregate temporarily detains stormwater runoff in the 40 percent void-space of the material. The ASTM No. 2 also has an infiltration rate of over 500” (12,700 mm ) per hour. 7 EDGE RESTRAINT 8 UNDERDRAIN 9 GEOTEXTILE FABRIC
- 44. strength, no- units instead ver options, he Americans ents, and allows ration. 2 4 .8 ead of sand, 1 d additional ting bed 0” (12,700 mm ) 3 7 t be avoided as 4 9 5 6 8 r ASTM No. 2, 6 ness. Installation y on sites with m ) is required for ust be designed ature, the ASTM r runoff in the also has an
- 47. POROUS PAVING • GREEN ROOFS • RAIN GARDENS • RAINWATER HARVESTING NEW TOOLS FOR SUSTAINABLE SITE DEVELOPMENT
- 49. Green • Water • Infrastructure Green • Water • Infrastructure Green • Water • Infrastructure Green • Water • Infrastructure Green • Water • Infrastructure
- 50. Special Thanks
- 51. Thank You P.O. BOX 124 WESTFIELD, INDIANA 46074 317-674-34949
Editor's Notes
- Tom Barrett is owner of Green Water Infrastructure. He has over thirty years of successful landscape industry experience and is known as an accomplished corporate growth and change agent.\n\nMr. Barrett has held various leadership positions at such industry leaders as Rain Bird, Kenney Machinery, Ewing, Netafim, and MacAllister Machinery. He has worked with such projects as Animal Kingdom at Walt Disney World in Florida. He has won numerous awards in Quality and Process Improvement, and is a frequent contributor of articles for numerous publications.\n\nMr. Barrett holds a Bachelor of Science in Agronomy and Plant Genetics from the University of Arizona. He furthered his studies in architecture at Syracuse Univ. He holds multiple certifications in irrigation and water conservation. Tom is a member of the Indiana Nursery and Landscape Association, as well as the International Irrigation Association, in which he chairs the Communications Committee. He is an approved instructor for the Irrigation Association.\n\nTom Barrett has been sharing his expertise and his ideas in energetic and dynamic presentations for over twenty years. He is a master trainer. His presentations empower people to become masters of change, rather than victims of circumstance by developing tools for transformative thinking. \n\nCurrently, Tom delivers over thirty presentations each year to organizations around the country. He is well-suited to talk to us today about Permeable Paving. Please join me in welcoming, TOM BARRETT!\n\n
- Green Infrastructure, Green Highways, and Green Streets will be the foundation for the rebuilding and expansion of our nations infrastructure and a key to our economic growth in the 21st Century. Green is the development of innovative approaches and strategies on how to integrate integrate grey and green infrastructure in order to protect water resources and promote sustainable design and community development. We have an opportunity to use a comprehensive approach that takes advantage of our experience on pilot projects, research, the development of standards and specifications, manuals of practice, training, and environmental management systems in order to integrate and institutionalize green approaches.\n\n
- At the largest scale, the preservation and restoration of natural landscape features (such as forests, floodplains and wetlands) are critical components of green stormwater infrastructure. By protecting these ecologically sensitive areas, communities can improve water quality while providing wildlife habitat and opportunities for outdoor recreation.\nOn a smaller scale, green infrastructure practices include rain gardens, porous pavements, green roofs, infiltration planters, trees and tree boxes, and rainwater harvesting for non-potable uses such as toilet flushing and landscape irrigation.\n\nPicture the grime of city streets -- oil, grease and soot from cars and trucks; pet waste; trash and litter; sediment and debris from construction sites; and a mix of toxic chemicals. Now picture the same streets after a rainstorm. They look cleaner, right? Sure, but the debris and contaminants haven't just disappeared -- they've been swept through street drains and underground pipes then washed directly into the nearby river, lake or bay.\nWherever humans have paved or built over the natural world, dirty rainwater tends to run straight into our waterways, contaminating the water, destroying habitat and damaging property. Known as urban runoff, this type of pollution can have serious consequences, from fouling drinking water to closing beaches and poisoning shellfish beds. Indeed, the U.S. Environmental Protection Agency now considers urban runoff and pollution from other diffuse sources the greatest contaminant threat to our nation's waters. The good news is that there are a number of proven solutions that towns and cities can use to reduce runoff pollution.\nOne new and exciting approach has emerged in recent years. Called "low-impact development," it uses both simple common sense and technology -- strategically placed beds of native plants, rain barrels, "green roofs," porous surfaces for parking lots and roads, and other tools -- to help rainfall evaporate back into the atmosphere or soak into the ground, rather than polluting the nearest water body. In effect, low-impact development mimics nature's own filtering systems. The result is less water pollution from dirty runoff, less flooding, replenished groundwater supplies -- and often, more natural-looking, aesthetically pleasing cityscapes.\n\n\n\n
- Floods. Droughts. Sewage overflows. Leaky pipes. Failing levees. Unsafe dams.  America’s water infrastructure is crumbling and outdated, and communities big and small across the country are feeling the impacts. \nIn its Report Card for America’s Infrastructure, the American Society of Civil Engineers gives the nation’s dams a D grade, and wastewater and drinking water systems a D-, the lowest grades of any infrastructure category. The U.S. Environmental Protection Agency states that the public health and environmental gains achieved since passage of the Clean Water Act are rapidly being reversed due to crumbling infrastructure. \nCommenting on the current state of the nation’s infrastructure, New York Mayor Bloomberg said, “We under-invest, and we invest badly.” Clearly, we need to invest more to upgrade and maintain our failing water infrastructure. But we need to invest more wisely, too. We will make a terrible mistake if we simply rebuild 19th and 20th century water systems that are costly and inflexible. \nInstead, we need a 21st century approach that integrates green solutions and helps ensure community safety and security. We need to invest in approaches that utilize “green infrastructure” as a first line of defense along with engineered structures that together can effectively meet multiple needs, at lower cost, and help communities and natural systems be better prepared for the impacts of climate change. \nWhat is Green Infrastructure?\nGreen infrastructure is a term that can encompass a wide array of specific practices, and a number of definitions exist (see the EPA’s definition here). In our view:\nGreen infrastructure is an approach to water management that protects, restores, or mimics the natural water cycle. Green infrastructure is effective, economical, and enhances community safety and quality of life.\nIt means planting trees and restoring wetlands, rather than building a costly new water treatment plant. It means choosing water efficiency instead of building a new water supply dam. It means restoring floodplains instead of building taller levees. \nGreen infrastructure incorporates both the natural environment and engineered systems to provide clean water, conserve ecosystem values and functions, and provide a wide array of benefits to people and wildlife. \nGreen infrastructure solutions can be applied on different scales, from the house or building level, to the broader landscape level. On the local level, green infrastructure practices include rain gardens, permeable pavements, green roofs, infiltration planters, trees and tree boxes, and rainwater harvesting systems. At the largest scale, the preservation and restoration of natural landscapes (such as forests, floodplains and wetlands) are critical components of green infrastructure.\nGreen infrastructure investments boost the economy, enhance community health and safety, and provide recreation, wildlife, and other benefits.Many forward-looking cities are already embracing green infrastructure, including New York, Indianapolis, Portland, Seattle, San Francisco, Minneapolis-St. Paul, Milwaukee, Kansas City, Toledo, Cincinnati, and Philadelphia, as well as many others.\n\n
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- Using permeable paving base for stormwater detention is a very efficient use of land. With this system, the surface is pervious, allowing detention to be contained underneath. Detention is under every square foot of permeable paving, as deep as necessary Traditional surface detention ponds which act as holding facilities for rainfall are a waste of space. For most land uses and all impervious areas, such as roof, roads, and parking lots, stormwater runoff flows through a system of pips that release it into detention or retention ponds. This valuable surface area can be utilized for more important uses.\n\nPermeable pavement systems used crushed, angular, open-grade aggregate base materials. These materials are entirely different than those used for traditional impervious roads and parking lots. These traditional systems use dense-graded aggregates containing fines, making them extremely slow draining. Conversely, the use of open-graded aggregates provide a void space or porosity of approximately 40 percent. This is utilize for detention and allows for a rapid infiltration rate of over 500” per hour.\n
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- Infiltration is extremely important to the groundwater supply. According to the U.S. Geological Survey, one of America’s mot important natural resource is groundwater. Half of the drinking water in the the U.S. comes from ground water, with the balance coming from lakes and rivers. Groundwater as a source of drinking water is projected to grow to 80 percent. Ground water is vital to agricultre and other industries, as well as essential for ensuring the health of rivers, streams, wetlands, and other bodies of water. Urban sprawl contributes to a decrease pervious area for rainwater infiltration and reduced groundwater levels. Soil infiltration is a simple method for ensuring future water availability.\n\nInstalling a permeable paving system above porous soils allows for stormwater infiltration, reducing runoff and flooding. Most soils, even clay, allow for infiltration.\n
- A soil with 1/4” per hour infiltration rate will have complete infiltration after about four hours of rainfall. However, most rain events generate only 1/2” of water.\n
- The EPA recognizes permeable paving as a Best Management Practice for non-point source pollution. Utilizing permeable paving ensures cleaner water. Many municipalities have begun to implement strategies to improve water quality by using Best Management Practices like permeable paving.\n
- The Interlocking Concrete Paving Institute has conducted test in which they examine water quality. Their findings indicate that cleaner, cooler water results from being filtered through a permeable paving system.\n
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- For traditional non-permeable paving surfaces, rainfall intensity and duration are normally analyzed together. However, with a permeable paving surface, intensity is less of a factor because the surface infiltration rate will exceed most rainfall events. A permeable paving surface are capable of capture more than 100” per hour. For larger rainfall events, duration is important to recognize. A heavy rainfall event could produce 6” of rain per hour but the duration may be only ten minutes. Longer duration rain events can be more demanding. Permeable paving system, when properly designed and installed, can usually contain most rainfall events.\n\nA runoff coefficient is used to measure the percentage of water that runs off different surfaces. Asphalt has a runoff coefficient of 85%. Turfgrass has a runoff coefficient of 15%.\nThe runoff coefficient of permeable paving is zero unless the rainfall intensity exceeds the surface infiltration rate or the entire open-graded base reaches capacity. With a properly designed and installed permeable surface, capacity will rarely be reached.\n\nDuring the site investigation phase, conducting a geotechnical or porosity test will determine the soil infiltration rate, which will establish the stormwater design requirements. Typical industry recommendations suggest an under-drain for soils with an infiltration rate of less than 1/2” per hour. It is possible to eliminate the under-drain system for soils with infiltration rates greater than 1/2” per hour.\n\nThe Release Rate refers to the volume of water that is allowed to be discharged into a municipal system or waterway. Many stormwater regulatory agencies require that post-development release rate does not exceed the pre-development conditions. Permeable paving slows and detains stormwater in the open-graded base so that it can be gradually released. Local jurisdiction should be contacted for required release rate.\n\n\n\n\n
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- There are three distinct materials used in permeable paving\nFirst, pavers are the most common. They come in a wide variety of textures and patterns. Interlocking pavers increases the structural performance of the paving system and reduces annual maintenance cost. Interlocking pavers prevent shifting or twisting due to vehicle braking and turning. L-shaped pavers can be mechanically installed, significantly reducing the initial installation cost when compared to manual installation.\n\nPorous concrete is the second most common material used in porous paving systems. The void space of porous concrete ranges between 15% and 22%, compared to a three to five percent void space in conventional concrete.\n\nAlthough not as common, porous asphalt has been successfully used as a permeable paving material. Porous asphalt consists of standard bituminous asphalt in which the fines have been screened and reduced, creating void space to make it highly permeable to water. The void space of porous asphalt is approximately 16%, as opposed to two to three percent for conventional asphalt.\n\nSingle-sized aggregate without any binder is the most permeable paving material in existence, and the least expensive. Although it can be used only in very low-traffic settings such as seldom-used parking stalls, its potential cumulative area is great.\nPorous turf, if properly constructed, can be used for occasional parking like that at churches and stadiums. Living turf transpires water, actively counteracting the "heat island" with what appears to be a green open lawn.\n\nResin Bound Paving is a mixture of resin binder and aggregate. Clear resin is used to fully coat each aggregate particle before laying. Enough resin is used to allow each aggregate particle to adhere to one another and to the base yet leave voids for water to permeate through. With resin bound paving you have a strong and durable surface that is suitable for pedestrian and vehicular traffic in applications such as pathways, driveways, car parks and access roads.\n\n\n
- Used primarily for paving systems. This material acts as the initial filtering layer, the 1/4” crushed, angular, chip stone captures 80% of the debris in the first 1” to 2”. The secondary function is to increase the interlock between the paver units to create the structural stability. The joint aggregate must always remain filled to the lip of the paver units to reduce clogging.\n
- Using the 1/4” crushed, angular chip stone, instead of sand, provides a smooth leveling course for setting the pavers. Unlike sand, the setting bed aggregate allows for rapid water infiltration with over 500” per hour through the 40% void-space. The use of sand must be avoided as a setting bed.\n
- When subsoil conditions are conducive to supporting the ASTM no. 57 crushed, angular, open-graded base material without migration, it can be used without ASTM No.2 subbase aggregate. Minimum thickness must be determined by sufficiently supporting anticipated loads, as well as accommodating stormwater detention in the 40 percent void space of the material. The ASTM No. 57 base aggregate, with a minimum thickness of 4”, serves as a transition material between the ASTM No. 2 subbase aggregate The infiltration rate of the ASTM no. 57 is over 500” per hour.\n
- Subsoil conditions will dictate the necessity of this larger ASTM No. 2, crushed, angular, open-graded subbase aggregate thickness. Installation of this material will provide increased structural stability on sites with poor soil conditions. A minimum thickness of 8” is required for effective performance. Subgrade aggregate thickness must be designed to sufficiently support anticipated loads. As an additional feature, the ASTM No. 2 subbase aggergate temporarily detains stormwater runoff in the 40 percent void-space of the material. The ASTM No. 2 has an infiltration rate over 500” per hour.\n
- Existing soil materials will determine the performance capabilities of the porous paving system. Pre-construction soil analysis , including percolation, California Bearing ratio, and penetrometer measurement (blow counts) are necessary for proper design. Subsoils with less than 1/2” per hour of infiltration may require underdrainage, scarification, and potentially, amendments. Subsoils with infiltration rates greater than 1/2” per hour are considered highly permeable. Subsoil compaction can cause a detrimental reduction in permeability and could be eliminated.\n\nThe California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses.\n\nThe CBR rating was developed for measuring the load-bearing capacity of soils used for building roads. The CBR can also be used for measuring the load-bearing capacity of unimproved airstrips or for soils under paved airstrips. The harder the surface, the higher the CBR rating. A CBR of 3 equates to tilled farmland, a CBR of 4.75 equates to turf or moist clay, while moist sand may have a CBR of 10. High quality crushed rock has a CBR over 80. The standard material for this test is crushed California limestone which has a value of 100.\n
- Edge restraint is vitally important to the success of a porous paving surface. This is especially true for interlocking pavers. The failure of the edge restraint will negatively impact the integrity of the paving surface. For all vehicular applications a concrete curb is required. For non vehicular and pedestrian areas, a plastic edging may be sufficient when properly anchored to the subbase.\n
- The underdrain pipe is based on several factors, such as the subsoil permeability, detention requirements and stormwater release rates. With highly permeable soils over 1/2” per hour, the underdrain pipe could be eliminated. Underdrain pipe size is inconsequential, provided the flow rate is greater than the release rate.\n
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- Why Choose Green Infrastructure?\nNature works best: Rivers, streams, wetlands, floodplains, and forests provide a suite of critical services like clean water and flood protection, and should be viewed as essential and effective components of our water infrastructure. New York City has great quality tap water because the city invested in water protection by purchasing land around its Catskills reservoirs to ensure that polluted runoff from roads and lawns doesn’t enter the water supply.The city’s $600 million investment in Catskills land protection and restoration did the job of $6 billion in capital costs to construct a water filtration plant as well as $200-300 million in annual operation and maintenance costs.\nWe can’t waste money: Spending money wisely means investing in multi-purpose solutions that lower costs and provide more benefits. Recently, the City of Indianapolis announced that by using wetlands, trees, and downspout disconnection to reduce stormwater flows into their combined sewer system, the City will be able to reduce the diameter of the planned new sewer pipe from 33’ to 26’, saving over $300 million. \nWe must enhance community safety and enjoyment: Traditional infrastructure isn’t designed to handle the increased floods and droughts that come with global warming, so we need a modern approach to protect public health, safety, and quality of life. Green solutions give communities the security and flexibility they need. Napa, CA solved flooding problems by choosing to restore the Napa River’s natural channel and wetlands, rather than lining the river with concrete. The effort has protected 2,700 homes and prevented $26 million in flood damage each year, and has created new parks and open space.\nReturn to Top\nGreen Infrastructure is Good for Jobs and the Economy\nThese green solutions create good jobs in many sectors, including plumbing, landscaping, engineering, building, and design. Green infrastructure also supports supply chains and the jobs connected with manufacturing of materials including roof membranes, rainwater harvesting systems, and permeable pavement. \nNew York City’s broad sustainability plan, PlaNYC, includes substantial investments in green infrastructure to reduce stormwater and sewage overflows and protect drinking water supplies. The City estimates that full implementation of PlaNYC will create 4,449 water infrastructure jobs of all types per year.\nOther countries are utilizing green water technologies at a much higher rate than the United States. We cannot afford to fall behind other nations in this vital area, it is a matter of economic competitiveness as well as quality of life and community security.A New Vision for Water\nWe are at a crossroads today in how we manage our water. Traditional water infrastructure will continue to play a role, but it is static, solves only a single problem, and requires a huge expense to build and maintain. We must use this transformational moment to move from old 19th Century infrastructure to a wiser combination of green and traditional infrastructure that will meet the needs of the 21st Century. \n
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