Innovative Stormwater Management POROUS ASPHALT PAVEMENT by psb58920


									             Innovative Stormwater Management
                with Subsurface Recharge Bed

                                                                                     • Conserves water

                                                                                     • Reduces runoff

                                                                                     • Promotes infiltration

                                                                                     • Cleans stormwater

                                                                                     • Replenishes aquifers

                                                                                     • Protects streams

                                                                                     • Better Water Quality

                  Uncompacted Subgrade - Keeps permeability high to                  • Allows for better use
                                         allow as much infiltration as
                                                                                      of land
              Non-Woven Geotextile - Protects stone recharge bed above
                                     from contamination and allows
                                     water to flow through to the soil.
          Stone Recharge Bed -    Heart of system. Large, single size,
                                  crushed stone with 40% voids stores
                                  storm water for infiltration.
      Choker Coarse -    Single size crushed aggregate (1/2-inch) stabilizes
                         surface for paving.
  Open-Graded Asphalt Pavement - An open-graded asphalt mix that
                                 is porous, allowing storm water to
                                 flow through surface into stone
                                 recharge bed.
Unpaved Stone Edge - A backup system in case the pavement surface
                     should ever become sealed. Stormwater can
                     flow off pavement surface to stone edge and into
                     stone recharge bed. Other methods may be used.

                                                  Additional information can be found at these resources:
                 P.O. Box 668,           (Porous asphalt design guide)
             Brainerd, MN 56401
                                         (Leading environmental consultants with
                                                  porous asphalt)

Better Water Quality With Porous                                   Construction and performance                                   Economics                                                                               pavement have been used in
Asphalt                                                                                                                                                                                                                   California since the 1950s. Salmon
                                                                   The stone bed, often eighteen to thirty-six inches in depth,   Porous pavement is a sound                                                              hatcheries and fish rearing ponds
                                                                   provides a tremendous sub-base for the pavement. As a          choice on economics alone.                                                              in the Pacific Northwest use asphalt
In 2005 Anderson Brothers was proud to have been the
                                                                   result, porous asphalt pavements tend not to exhibit crack-    Because porous pavement is                                                              liners.
first contractor in the state in install porous pavements.
                                                                   ing and pothole formation problems. The surface wears          designed to “fit into” the topogra-
Now we’ve been honored to have the largest and the most
                                                                   well. Under the stone bed is a geotextile, which keeps fine    phy of a site, there is generally                                                       Variations on the theme
installations - paving the way for this environmental initia-
tive in central Minnesota.                                                                                                        less earthwork. The underlying
                                                                                                                                  stone bed is usually more expen-                                                         Porous asphalt can be used suc-
Porous asphalt offers a powerful tool in the toolbox for                                                                          sive than a conventional com-                                                            cessfully in parking lots, walkways,
storm-water management.                                                                                                           pacted sub-base, but eliminating                                                         and playgrounds. Several current
                                                                                                                                  the detention basin and other                                                            suburban projects are exploring its
                                                 In the natu-                                                                     components of stormwater manage-
                                                                                                                                                                             Cooler cities
                                                                                                                                                                                                                       use in subdivision roads. A few porous
                                                 ral environ-                                                                     ment systems offsets this cost differ-                                               highways and city streets have been
                                                 ment, rain-                                                                                                                 Porous asphalt pavements have been
                                                                                                                                  ence. On projects where unit costs                                                   constructed, both in the U.S. and in
                                                 fall sinks into                                                                                                             shown to mitigate the urban heat
                                                                                                                                  have been compared, the porous                                                       Europe, and have performed well. The
                                                 soil, filters                                                                                                               island effect. Open-graded asphalt
                                                                                                                                  pavement has been the less expensive                                                 open-graded asphalt surface used for
                                                 through it,                                                                                                                 roads and highways—which use the
                                                                                                                                  option. Porous pavements are there-                                                  porous pavements has been used
                                                 and eventu-                                                                                                                 same surface material as porous park-
                                                                                                                                  fore attractive on both environmental                                                extensively to surface high-volume
                                                 ally finds its                                                                                                              ing lots—have been shown to lower
                                                                   particles from moving into the stone bed from below and        and economic grounds. An installa-                                                   highways that carry heavy trucks. Its
                                                 way          to                                                                                                             nighttime surface temperatures as
                                                                   filling in the spaces. The recharge beds must be built cor-    tion at the University of North Carolina                                             benefits include noise reduction, a
                                                 streams,                                                                                                                    compared to impervious pavements. In
                                                                   rectly and over permeable soils in order to function prop-     in Chapel Hill included parking lots                                                 decrease in splash and spray kicked
                                                 p o n d s ,                                                                                                                 at least one city, the hottest heat
                                                                   erly. Porous asphalt has been proven to last for decades,      where some sections were constructed                                                 up by vehicles in heavy downpours,
                                                 lakes, and                                                                                                                  signature is at the airport, with its
                                                                   even in extreme climates, and even in areas with many          from porous asphalt and others used                                                  and mitigation of the urban heat island
underground aquifers. The built environment, by way of                                                                                                                       thick, dense, impervious runways.
                                                                   freeze-thaw cycles. The underlying stone bed can also          porous concrete. The cost differential                                               effect.
contrast, seals the surface. Rainwater and snowmelt
                                                                   provide stormwater management for adjacent impervious                                                     Comparisons to other asphalt pave-
become runoff, which may contribute to flooding.                                                                                  was approximately 4:1 – that is, the
                                                                   areas such as roofs and roads. To achieve this, stormwa-                                                  ments the surface of a porous asphalt
Contaminants are washed from surfaces directly into                                                                               porous concrete pavement cost four                                                   If you have an interest or questions
                                                                   ter is conveyed directly into the stone bed, where perforat-                                              pavement wears well. While slightly
waterways without undergoing the filtration that nature                                                                           times as much as the porous asphalt                                                  regarding porous pavements please
                                                                   ed pipes distribute the water evenly.                                                                     coarser than some pavements, it is
intended. For these reasons, managing stormwater is a                                                                             pavement.                                                                            contact us at Anderson Brothers. We’d
                                                                                                                                                                             attractive and acceptable. Most people
significant issue in land use planning and development.                                                                                                                                                                love an opportunity to show you how
                                                                   The long-term maintenance of porous asphalt is not diffi-                                                 driving or walking on the pavement
Stormwater management tools can serve to mitigate the                                                                             Impact on groundwater                                                                we can help your project.
                                                                   cult. Never apply sealant or sand to surfaces that would                                                  will not notice (or believe) that it is
impact of the built environment on natural hydrology.
                                                                   clog the pores in the pavement. For the same reasons                                                      porous. Like all asphalt pave-
Unfortunately, however, they also can lead to unsound                                                                             Asphalt pavements are compatible
                                                                   adjacent landscaping should be designed to ensure that                                                    ments, porous pavements meet
solutions such as cutting down stands of trees in order to                                                                        with clean water. Studies show that
                                                                   mud couldn’t be washed into the parking lot surface.                                                      the     requirements    of   the
build detention ponds. Porous asphalt pavements allow for                                                                         asphalt pavements and stockpiles of
land development plans that are more thoughtful, harmo-                                                                                                                      Americans with Disabilities Act
                                                                                                                                  reclaimed asphalt pavement do not
nious with natural processes, and sustainable. They con-                                                                                                                     (ADA).
                                                                                                                                  leach. Contaminants on the surface of
serve water, reduce runoff, promote infiltration, which
                                                                                                                                  pavements tend to become part of
cleanses stormwater, replenish aquifers, and protect                                                                                                                         Environmental applications
                                                                                                                                  runoff, but with a porous pavement,
streams. A typical porous pavement has an open graded
                                                                                                                                  they are washed into the stone bed.
surface over an underlying stone recharge bed. The water                                                                                                                     Asphalt pavements have been
                                                                                                                                  From there they flow down into the
drains through the porous asphalt and into the stone bed,                                                                                                                    used for many years to enhance
                                                                                                                                  soil, where beneficial bacteria and
then, slowly, infiltrates into the soil. If contaminants were                                                                                                                water quality. At landfills,
on the surface at the time of the rainfall, they are swept                                                                        other natural processes cleanse them.
                                                                                                                                                                             asphalt liners and caps keep
along with the rainwater through the porous asphalt. From                                                                         Data are limited, but indicate a very                                         Water is shown standing on regular pavement in the
                                                                                                                                                                             contaminants from leaking into
there they infiltrate into the recharge bed and sub-base                                                                          high removal rate for total suspended                                         lower right corner. While the water is percolating
                                                                                                                                                                             groundwater. Drinking water        through the porous asphalt as it leaves the garden
which filters out the non-point source pollutants through an                                                                      solids, metals, and oil and grease.
                                                                                                                                                                             reservoirs lined with asphalt      hose.
array of physical, chemical and biological mechanisms.

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