Interview with Heather Murphy below!

Tire marks, dirt...all that stuff is going to leave darker patches and affect the results. Do you still feel like the test patches are performing as planned?

The Street Transportation Department applied the Cool Pavement material to eight quarter sections worth of roads and at one city park. The areas were selected based on the diversity of activity and landscaping types to test this very notion. Tire marks, dirt and other stains generally wash away after a good rain. Part of the pilot program is to see how the material holds up over time and how it ages. These factors will help determine how and where Cool Pavement might be most effective.

Any idea about how many miles of asphalt we would cover if we applied cool pavement to all roads in phoenix? the whole valley? Phoenix has about 5,000 square miles of roads and, generally speaking, we apply preservation treatments to our roads about every 10 years or so. Cool Pavement is a type of seal coat that is appropriate for a road in decent structural condition but one that needs a surface preservation treatment. Cool Pavement would not be used on major arterial roads like Thomas, McDowell, Camelback, Central Avenue, 7th Street, etc. because these roads carry a large volume of vehicles, generally at higher speeds. A seal coat treatment is more appropriate for lower speed, lower friction roads.

Would big shopping center parking lots be expected to pay for this treatment themselves? Are there any businesses that have asked you about it already?

The City of Phoenix paves, treats and preserves the roads it owns. Shopping center, mall, church and retail parking lots are private property and are maintained by the property owners. After launching the Cool Pavement Pilot Project, we did receive several inquiries about what the product was called and who made it (GuardTop). If it proves effective, schools, churches, arenas, shopping centers and others may want to consider this type of treatment when their parking areas are due for rehabilitation.

Is there a more efficient way than applying the coating by hand? If we were to do the highways, that would seem like it could take forever.

The material was initially applied through a cart (I called it the Road Zamboni like the Zamboni vehicles that smooth out ice rinks) and hand squeegeed. Working with one of our contractors, the Street Transportation Department devised a spray application method that basically covered one half of a neighborhood street at a time. Then they loop back and apply a second coat. In the attached photo, you can see the truck moving along and spraying the material down. (It goes on shiny and dries to a matte finish.) The Cool Pavement product is specially formulated to bond to asphalt. It could not be used for highways, which are mostly concrete. And, as mentioned above, this current product would not be a viable product for a high-speed, high friction application with heavy vehicles like tractor trailers hauling freight.

I see on the website there's an increased cost, but it might be offset by the coating lasting longer....any estimate for the projected costs to the city if we tried to cover a real significant portion?

You’ve done your homework again! Cool Pavement is about 2.5 to 3 times the cost of other seal coats. Could there be savings if the product lasts 2-3 times longer AND has an environmental benefit, absolutely! That’s all part of what the pilot program is designed to sleuth out! If the product performs well and provides the heat island mitigation we hope it does, it may be worth the city’s investment to use it even if it only lasts as long as a traditional seal coat. These are things that Council and Mayor will be able to weigh once the scientific study is complete.

Phoenix has the distinction of having applied the most Cool Pavement of any location in the world. Los Angeles had a fairly small pilot program and our experts were able to visit some areas in LA where Cool Pavement was applied. Weather conditions in LA are quite different from Phoenix. Where they have fog, rain and salt air, we have monsoon storms, punishing heat and longer, hotter summers. Wear, durability and overall effectiveness are all part of the equation to find out if Cool Pavement is a worthwhile investment for the City of Phoenix.

After observing LA’s test locations, our team then selected the eight quarter sections and city park (with the help of the Mayor and City Council) where there were streets that were due for a surface treatment. We selected areas that had a diversity of conditions across the city so we could see how it holds up.

Any idea what a day and night in July might feel like in our heat island if we had cool pavement vs. now?

The answer to this question is something we hope the scientific testing underway now might be able to tell us. However, experiences differ greatly across the city. For example, downtown areas with paved streets, lots of concrete and high-rise buildings with less green space, parks or air movement – these areas cool very slowly because of the retained heat in the building materials. Conversely, when you get out to the suburbs where there is irrigated farmland, open space, houses spread farther apart, etc. it generally leads to lower night time temperatures. So a nighttime July temperature at my house might be very different from downtown, uptown, Anthem or Ahwatukee.

A question you didn’t ask is how much the Cool Pavement Pilot Project is costing the city. We estimate that the application and study will total about $3.3 million BUT, remember, money was going to be spent on all those roads to rehabilitate these roads anyway.

Contact Us!

Heather.Murphy@phoenix.gov

Zahrahasghar40@gmail.com

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