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Permeable Interlocking Concrete Pavement A sustainable approach to stormwater management. A Q&A interview with the Interlocking Concrete Pavement Institute Chairman, Ed Fioroni

Controlling the quantity and quality of on-site runoff is a major concern across the country. Design professionals and engineers are constantly searching for sustainable approaches to site development. Permeable Interlocking Concrete Pavement (PICP) is a fast growing sustainable design approach to stormwater management.

Q. What do you see as factors moving sustainable design ahead in the future? A. Sustainable approaches to site development come from the confluence of three societal streams—legislative, economic and social. A substantial flow from within the United States comes as sweeping national laws to reduce water runoff and pollution. Known as NPDES or National Pollutant Discharge Elimination System regulations, these mandate the use of post-construction best management practices (BMPs) such as PICP as part of states and localities receiving permits for stormwater runoff emissions into public streams, lakes, rivers, estuaries and bays. Such regulations are being implemented via state BMP manuals, with the same guiding principles being adopted in many Canadian provinces. They are founded on stormwater drainage design criteria, as well as in local municipal regulations. A parallel legislative stream, particularly at the municipal level, is the implementation of low impact development or LID principles in site design and community scale design. LID relies on natural means for managing stormwater in new and redevelopment projects. LID principles are merging with sustainable stormwater management. LID principles and techniques will likely transform and eventually supersede best management practice manuals. Specifically, LID principles include: 1. Conserve vital ecological and natural resources: trees, streams, wetlands and drainage courses. 2. Minimize hydrologic impacts by reducing imperviousness, conserving natural drainage courses, reducing clearing, grading and pipes. 3. Maintain pre-development time of concentration for runoff by routing flows to maintain travel times and discharge control. 4. Provide runoff storage and infiltration uniformly throughout the landscape with small, on-site decentralized infiltration, detention and retention practices such as permeable pavement, bio-retention, rain gardens, open swales and roof gardens. 5. Educate the public and property owners on runoff and pollution prevention measures and benefits.

This article was modified and originally published in the February 2009 issue of Landscape Architect and Specifier News

A second stream—an economic one—is from rapidly rising energy and material costs, much due to rising economies in China and India that seek the same limited petroleum and mineral resources as the developed world. Higher prices remind all of limits to available resources that sustain and grow civilizations and cultures. Hence, life-cycle costs for best return on investment as well as life-cycle assessment for understanding environmental impacts are becoming key factors in building and site design decisions. The third stream is social and professionally oriented, i.e., the development of evaluation systems for selecting building and site technologies. The design professions have embraced evaluation systems such as LEED® and Green Globes because their clients (public or private sector) are seeking more economical solutions to building and site design. Such evaluation systems feed legislative, LID and owner/bank financing streams.

Q. How does Permeable Interlocking Concrete Pavement (PICP) support Low Impact Development (LID) principles? A. LID principles are merging with sustainable stormwater management. Permemeable Interlocking Concrete Pavement conserves on-site space including roads, parking, stormwater infiltration and retention all combined into the same space creating more green space or building opportunities. It preserves wooded areas that would otherwise be cleared for stormwater detention or retention ponds. PICP increases site infiltration that helps maintain pre-development runoff volumes, peak flows and time of concentration. It not only promotes tree survival and growth it can contribute to urban heat island reduction through evaporation and reflective, light colored pavers.

Q. How does Permeable Interlocking Concrete Pavement work? A. Permeable Interlocking Concrete Pavement uses solid concrete pavers which are placed on top of an open aggregate base and sub-base. The joints or openings are filled with a small open-graded aggregate. It is this small aggregate which makes the system 100% permeable. The open-graded base and sub-base become the reservoir for stormwater management.

Permeable Interlocking Concrete Pavement Q. Within the North American design and construction community, LEED® has emerged as a project evaluation method for defining sustainable design. What is LEED® and how does PICP fit in?

This article was modified and originally published in the February 2009 issue of Landscape Architect and Specifier News

A. Developed by the U.S. Green Building Council (USGBC) in 1998, and adopted by the Canadian Green Building Council in 2003, LEED® provides voluntary guidelines for reducing energy and wasted resources from building and site design. LEED® is a consensus-based means for measuring building and site performance. It promotes designs that integrate energy and resource conservation. A primary objective of LEED® is to help facility owners reduce maintenance and life-cycle costs. This is accomplished by including all players in an integrated development process during the design stages of a project. LEED® rating systems have been developed for new commercial construction and major renovation projects (commonly used), existing building operations and maintenance, commercial interior projects, core and shell development projects, homes, neighborhoods, multiple buildings and on-campus building projects and schools. Permeable Interlocking Concrete Pavement alone can earn a total of 3 LEED® points. 1 point under SS 6.1 Sustainable Sites Stormwater Design: Quantity Control: requirement - (less than 50% site imperviousness: reduce to pre-development peak discharge and quantity for a 2 year, 24-hour storm; greater than 50% site imperviousness: 25% volume decrease from 2 year, 24-hour storm.), 1 point under SS 6.2 Sustainable Sites Stormwater Design: Quality Control: requirement - (capture and treat 90% of average annual rainfall (0.5 to 1 in. or 13 to 25 mm depending on region). Remove 80% of total suspended solids (TSS) and 1 point under WE 1.1 Water-efficient Landscaping: requirement - reduce potable water use for irrigation by 50%. All together, the family of segmental concrete pavements (this family includes interlocking concrete pavements, permeable interlocking concrete pavements, concrete grid pavements and precast concrete paving slabs) can earn a total of 17 LEED® points.

Q. What other benefits are there from using Permeable Interlocking Concrete Pavement? A. The modular concrete units allow for project phasing and the open-graded base and subbase materials are typically available locally. Another benefit would be rain water harvesting, PICP is capable of storing water for on-site irrigation or building grey water use. It can be designed with underground stormwater storage systems, over many slower-draining clay soils and in cold climates. It even processes and reduces pollutants from vehicular oil drippings!

Q. Can PICP reduce runoff? A. Given regional variations in annual rainstorms and PICP base storage capacities, PICP can reduce annual runoff between 30% and 80%. Well-maintained PICP can reduce flows by 70% to 90% from intense rain events and up to 100% for many storms. This yields a corresponding reduction in runoff pollution.

Q. Can PICP be used on clay soils? A. Yes. Even in clay soils, PICP reduces runoff and helps to capture “first flush” runoff and reduce pollution.

This article was modified and originally published in the February 2009 issue of Landscape Architect and Specifier News

Q. Can PICP be used to replace conventional stormwater management tools such as detention basins? A. Yes, as a matter of fact, in both colder and warmer climates, PICP has been used to reduce or eliminate the need for conventional stormwater pipe infrastructure, detention basins and drop inlets.

Q. Is Maintaining PICP difficult? A. No. PICP can be maintained through street sweeping and vacuuming based on a periodic inspection.

Q. Can PICP be used in cold climates? A. Yes, PICP has been very successful in many Canadian and northern United States applications. It remains stable through freezing and thawing cycles.

In summary, sustainable design evaluation methods are seeing wider use as a means to protect public health, safety and welfare when required by public agencies. There are likely many private sector projects using LEED速 to evaluate design decisions without seeking certification. Segmental concrete pavement is an integral part of meeting LEED速criteria. Permeable Interlocking Concrete Pavement holds a unique advantage in that its use can earn at least three points returns while returning water resources for continued use by people and nature. Ed Fioroni is a Vice President of Sales & Marketing for Pavestone Company and the Chairman of the Interlocking Concrete Pavement Institute (ICPI) which represents producers, suppliers, contractors, design professionals and consultants. ICPI promotes the highest product standards through ICPI product certification and installation guidelines through ICPI concrete paver installer certification. In addition, ICPI publishes the Interlocking Concrete Pavement Magazine, along with marketing and technical resources for design professionals, contractors and homeowners. For more information PICP visit

This article was modified and originally published in the February 2009 issue of Landscape Architect and Specifier News

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