Permeable Paving

1. Permeable Paving

2. Low Impact Development (LID) • Low impact development (LID) is an approach to managing stormwater runoff to protect water quality

3. Permeable Pavements • Permeable pavements are recognized as a Best Management Practice (BMP) by the U.S. Environmental Protection Agency • A cornerstone of low impact development (LID) design

4. Non-Permeable Pavements • Increased runoff • Deprives groundwater • Pollutants • Non-point source

5. Non-Permeable Pavements • 1990s average was about 30,000 miles of paving per year • Parking lots affect microclimates of city climates

6. Non-Permeable Pavements • U.S. federal law mandates that states control water pollution in runoff through the National Pollutant Discharge Elimination System (NPDES)

7. Advantages of Permeable Pavers • Increases the water quality • Increases groundwater • Reduces installation costs of drainage system • Reduces storm water runoff • Reduces flooding • Reduces erosion

8. Permeable pavers • PICP (also called permeable segmental pavers) are non-porous, solid blocks made of brick, stone, clay or concrete

9. Permeable pavers • Initially, infiltration is over 50-75in/hr. • Reduce by around 50% in the first 5 years. • Over a 20-year period, PICP’s are designed to achieve and maintain a consistent 3in/hr infiltration rate

10. Permeable pavers • No sand used in joints • Clog pores

11. Permeable pavers • http://www.youtube.com/watch?v=xBTYFo2z9HY&feature=related

29. Permeable pavers • Cleaning should be done at least once a year • Removed by a vacuum-sweeping street cleaning machine

30. Permeable interlocking concrete pavements • A North Carolina State University study has shown that the initial surface infiltration rate of PICPs can be as high as 2,000 in./hour. Other research has shown that near initial surface infiltration rates can be restored through cleaning and replacement of the initial 3/4 to 1 in. depth of small stones in the openings of PICPs.

31. Permeable interlocking concrete pavements • Ice and snow can melt into the pavement • Water does not collect on the surface and re-freeze • Reduces slipping hazards

32. Permeable interlocking concrete pavements • Sand should not be used for traction • Deicing salts can • Adequate space for the ice to expand within the open-graded base • Minimizing the risk of heaving.

33. Pervious Asphalt and Concrete • Stone aggregate is held together with either asphalt or cement • Angular crushed stone, usually 3/8”, excluding fines that normally fill voids • Porous • http://www.youtube.com/watch?v=ScsQYHMfabU

34. Pervious Asphalt and Concrete Ice doesn’t normally form in the paving or on the surface

35. Pervious Asphalt and Concrete • Pervious paving may cost 10% more than conventional asphalt • Doubling as a stormwater system and eliminating storm drains, save 12% to 38% • Reduces retention ponds • Land area saved that would be used for basins

36. Pervious Asphalt and Concrete Snow melts quickly and drains Soil around any porous installation must percolate minimum rate ½” per hour Contain no more than 30% clay

37. Pervious Asphalt and Concrete • Most researchers found that proper design, installation and maintenance can prevent loss of porosity over time • Minor loss of porosity occurs in all porous materials over the first four to six years • One test, an inch of loose fine was applied • Full porosity was easily restore by a cleaning with a HydroVac

38. POROUS ASPHALT • Formulated with larger aggregate and less fine particles • “Open-graded” surface drains and supports traffic • Single-sized aggregate particles leave open voids (typically between 25-35%) that give the material its porosity and permeability.

39. POROUS ASPHALT • Beneath its surface, underlying stone reservoir that then filters water directly into the underlying soil, or storm-drain system

40. POROUS ASPHALT • Asphalt version originally developed for airport runways • prevents dangerous surface ponding • Reservoir supports the porous surface and hold precipitation until it can percolate into the soil • Shallow as nine inches on some well-drained soils

41. POROUS ASPHALT • Using crushed rock open graded to about two inches in size, almost 40% of the reservoir’s total volume will be waterholding voids • Choker course of half inch gravel is laid on top

42. Cool asphalt • Increase pavements reflectiveness • Albedo • Asphalt can be lightened • Asphacolor • Colored at plant

43. PERVIOUS CONCRETE • Grainier and less smooth than traditional concrete • Controlled amounts of water and cement materials bound with large aggregate particles • Contains little or no fines • Substantial void space between 25-35% • Runoff coefficient close to zero • Underlying stone reservoir

44. PERVIOUS CONCRETE • Porous concrete withstands heavier and more repeated loads than porous asphalt • Does not soften under heat

45. Grass Pave Grass will not survive daily traffic Grass for parking stays healthy if used not more than about one day a week, less in dry climates http://www.youtube.com/watch?v=wx-CNC7f5xY

46. GRASS PAVERS • Open-cell unit paver in which the cells are filled with soil and filled with turf or gravel • Comprised of a grid system, which is made of concrete or synthetic to distribute the weight of traffic • Appropriate for • Foot traffic • Overflow parking • Driveway

47. Grass Pave • Overflow parking

48. Grass Pave • Fine gravel, oyster shells, or other permeable material can substitute for grass for more frequent parking

49. Grass Pave • Use mix of sand and water polymers

50. COST COMPARISON • Asphalt: $0.50 to $1 per square foot • Grass/Gravel Pavers: $1.50 to $5.75 per square foot • Porous Concrete: $2.00 to $6.50 per square foot • Interlocking Concrete Paver Blocks: $5.00 to $10.00 per square foot