[Greenbuilding] Green Streets

Mon Oct 1 22:27:30 EDT 2007

Here are the resources I compiled for the question I got on the 
sustainability implications of using pavers instead of concrete or 
asphalt on the street of a small Oklahoma town.  Someone asked that I 
post my response here in case someone else might benefit.  If the 
formatting messes up (as I suspect it will), I can send the document as 
an attachment to anyone who requests it privately.**

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*Resources: Green Streets*

[City Councilman],

I was able to come up with several "categories" of sustainability 
implications of pavers and the resources I've included no doubt include 
others. Those on my radar include:

Stormwater management

Integration with living plantscaping & with the natural environment

Carbon generated with manufacture, maintenance, & transportation

Heat island effect

Durability (including repair vs. replacement) and longevity

Aesthetics can affect pedestrian safety & participation

Reflectivity & lighting

Reclaimed, recycled content & future re-use or recyclability

Briefly, a few considerations within those categories include:

*Stormwater management:  *

    * Pervious paving alternatives exist that allow rainwater to drain
      through them, to be absorbed into the ground instead of routing it
      (along with its pollutants) to streams.
    * Pervious paving involves a maintenance cost, as well as the
      initial higher installation costs.
    * Pavers (not including pervious pavers) may or may not facilitate
      rainwater absorption---it depends upon the material used.

*Integration with living plantscaping & with the natural environment:*

    * Pervious/porous paving and/or pavers, if they allow rainwater
      penetration, would also give water and air access to tree roots,
      allowing a natural (living) environment to flourish along with the
      built environment.
    * Trees and shrubs provide habitat and food for many living
      organisms and may increase human satisfaction as well (see
      Biophilia: http://en.wikipedia.org/wiki/Biophilia ).

*Carbon generated with manufacture, maintenance, & transportation:*

    * The manufacture of cement and asphalt carries them a significant
      carbon cost (known as "embodied energy"), contributing to global
      climate change. Clay or stone pavers also carry a carbon cost.
      These costs should be weighed and compared. There are concrete
      additives that can reduce its embodied energy.
    * Concrete and asphalt streets must be repaired with
      newly-manufactured concrete or asphalt when street repair is
      necessary.  Pavers may allow the street to be repaired without
      destroying the pavers, therefore allowing the same pavers that
      were pulled up to be replaced when the repair is completed. 
    * Minimally-processed materials often have lower embodied costs than
      manufactured materials.  (Ex: raw stone pavers vs. asphalt)
    * Transportation costs are also part of embodied energy.
      Locally-sourced materials should be considered.
    * The lowest-carbon choice may be to leave the existing paving
      there, if a usable pavement already exists.

*Heat island effect:*

    * Dark, high-mass paving materials (such as asphalt) absorb more
      heat and retain it into the night, increasing the ambient
      temperature in urban areas. Solid concrete is usually lighter in
      color than asphalt, but still high mass.  Pavers may or may not
      have less mass and, therefore, less capacity for heat storage. The
      color of pavers also influences heat storage.
    * Porous paving, when used along with trees, can both decrease the
      thermal mass (heat-storing capacity) and also increase shading,
      decreasing the temperature of the city.

*Durability (including repair vs. replacement) and longevity:*

    * Durability, longevity, repair & replacement requirements are all
      part of life-cycle costs and must be included in the environmental
      equation.

*Aesthetics can affect pedestrian safety & participation:*

    * Part of sustainable development is creating an environment that
      encourages human interaction within the urban landscape.
    * Pavers utilizing different colors can contribute to pedestrian
      safety (visually marking pedestrian crossings, for example)
    * An attractive streetscape may draw human activity to the urban
      environment.

*Reflectivity & lighting*

    * There is some evidence to suggest that light-colored pavements
      reflect more light, decreasing the amount of energy required to
      illuminate streets/sidewalks/parking lots and/or increasing
      nighttime safety.

*Reclaimed, recycled content & future re-use or recyclability *

    * Paving materials that contain some recycled content may be
      "greener" than pavements that use all-new materials.
    * Re-using pavers that have been reclaimed from another use may be
      the "greenest" choice (though transportation costs should also be
      considered).
    * Using materials that can, themselves, be reclaimed (best) or
      recycled offer a "green" benefit as well.

Here are some resources you may find helpful for answers to some of the 
questions raised above:

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Wikipedia on permeable paving:
http://en.wikipedia.org/wiki/Permeable_paving

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A resource from the Portland Cement Association that details a lot of 
sustainability issues as it pertains to the use of cement.  Includes 
several resources on "pavers".

http://www.concretethinker.com <http://www.concretethinker.com/>

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Green streets: Innovative solutions for stormwater and stream crossings
http://www.metro-region.org/article.cfm?articleID=262

This is a new resource for designing environmentally sound streets that 
can help protect streams and wildlife habitat. The handbook describes 
basic stormwater management strategies and illustrates street designs 
with features such as street trees, landscaped swales and special paving 
materials that allow infiltration and limit runoff. The handbook also 
provides guidance on balancing the needs of protecting stream corridors 
and providing access across those streams.

What is a green street?

A green street can be defined as a street designed to:

    * integrate a system of stormwater management within its right of way
    * reduce the amount of water that is piped directly to streams and
      rivers
    * be a visible component of a system of "green infrastructure" that
      is incorporated into the aesthetics of the community
    * make the best use of the street tree canopy for stormwater
      interception as well as temperature mitigation and air quality
      improvement
    * ensure the street has the least impact on its surroundings,
      particularly at locations where it crosses a stream or other
      sensitive area.

The design and construction of green streets is one component of a 
larger watershed approach to improving the region's water quality, and 
requires a more broad-based alliance for its planning, funding, 
maintenance and monitoring.

3 Workbooks available:

    * Creating livable streets: Street design guidelines for 2040 ($14.95)
    * Green streets: Innovative solutions for stormwater and stream
      crossings ($14.95)
    * Trees for green streets: An illustrated guide ($9.95)

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Article about Salem, Oregon "Green Streets":
http://archive.mailtribune.com/archive/2006/0724/biz/stories/green_streets.htm

And here are a lot of specific details about that program:
http://www.portlandonline.com/bes/index.cfm?c=44213& 
<http://www.portlandonline.com/bes/index.cfm?c=44213&>

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5-page .pdf file from U.C. Davis that quotes one of the above workbooks:
http://extension.ucdavis.edu/unit/green_building_and_sustainable_design/pdf/resources/green_streets.pdf

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Portland City Commissioner (who may be willing to consult):
http://www.commissionersam.com/node/2395

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Porous Pavement:
http://www.greenworks.tv/stormwater/porouspavement.htm

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Several helpful things available here, including finding a consultant 
for environmental impact studies:
http://www.planning.org/

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Green Values Stormwater Toolbox:
http://greenvalues.cnt.org/

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This may be outside the realm of you're looking for, but I like the 
wide-angle view it provides:
http://www.serconline.org/grInfrastructure/talking.html

It introduces the idea of "green infrastructure" which means 
comprehensively planning as much for the environmental integrity of a 
place (biodiversity, watershed, greenspace) as you do the things you 
impose upon it (streets, houses, utilities, etc.)

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One advantage of clay bricks is their longevity. The intersections of 
the new bus mall in downtown Portland, Oregon features clay bricks set 
in sand. I can't think of a more punishing set of circumstances. 
Beautiful, made of something other than concrete or petroleum products, 
and long lasting. Even better, you can get to the utilities, tree roots, 
etc. beneath without destroying the surface.
http://www.oldlouisville.com/circa1900/brick-sidewalk.htm

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Sept issue of Environmental Design & Construction.  Beginning on page 
35, there is a long section called "Concrete's Contribution"  See 
specifically pages 46 and 47 on "pervious concrete."  
http://www.edcmag.com/digitalmagazine/index.html?pub=EDC&iss=0907 
<http://www.edcmag.com/digitalmagazine/index.html?pub=EDC&iss=0907>

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City of Seattle Greenhouse Gas Emissions considerations (including some 
things about paving)

http://www.seattle.gov/climate/PDF/Our_Carbon_Footprint.pdf

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I hope that something here can be helpful to you.  I'd like to know if 
you were able to use anything here and/or any feedback you might like to 
give.

Sincerely,

Leslie Moyer

Vice President

Sustainable Green Country

http://www.SustainableGreenCountryl.org 
<http://www.sustainablegreencountryl.org/>