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 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 Initially, infiltration
is over 50-75in/hr. Reduce by around
50% in the first 5 years. Over a 20-year
period, designed to achieve and maintain a consistent 3in/hr infiltration rate
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
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 Angular crushed stone, usually 3/8”, excluding
fines that normally fill voids Porous http://www.youtube.com/watch?v=ScsQYHMfabU
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 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
POROUS ASPHALT Asphalt version
originally developed for airport runways prevents dangerous
surface ponding Reservoir holds
water until it percolates into soil
Cool asphalt Increase pavement
reflectiveness Albedo
Asphalt can be lightened
Asphacolor Colored at plant
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
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