Permeable Paving

Low Impact Development (LID) Low impact development (LID) is an

approach to managing stormwater runoff to protect water quality

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

Non-Permeable Pavements Increased runoff Deprives groundwater Pollutants

Non-point source

Non-Permeable Pavements 1990s average was about 30,000 miles of

paving per year Parking lots affect microclimates of city

climates

Non-Permeable Pavements U.S. federal law mandates that states control

water pollution in runoff through the National Pollutant Discharge Elimination System (NPDES)

Increases the water quality Increases groundwater Reduces installation costs of drainage system Reduces storm water runoff Reduces flooding Reduces erosion

Advantages of Permeable Pavers

Permeable pavers PICP (also called permeable segmental

pavers) are non-porous, solid blocks made of brick, stone, clay or concrete

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

Permeable pavers No sand used in joints

Clog pores

Permeable pavers http://www.youtube.com/watch?v=xBTYFo2z9

HY&feature=related

Permeable pavers Cleaning should be done at least once a year Removed by a vacuum-sweeping street

cleaning machine

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.

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

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.

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

Pervious Asphalt and Concrete Ice doesn’t normally

form in the paving or on the surface

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

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

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

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.

POROUS ASPHALT Beneath its surface, underlying stone

reservoir that then filters water directly into the underlying soil, or storm-drain system

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

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

Cool asphalt Increase

pavements reflectiveness Albedo

Asphalt can be lightened

Asphacolor Colored at plant

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

PERVIOUS CONCRETE Porous concrete withstands heavier and more

repeated loads than porous asphalt Does not soften under heat

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

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

Grass Pave Overflow parking

Grass Pave Fine gravel, oyster shells, or other permeable

material can substitute for grass for more frequent parking

Grass Pave Use mix of sand and water polymers

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

Green Streets Manage water at source Infiltrate water where it hits the ground Reduce downstream flows by at least 80%

Manage water at the surface Allow for evapotranspiration

Assets Aesthetically pleasing