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Paving a road into the future
t Pervious paving gains acceptance.
SILVERDALE — Northwest winters are often highlighted by rain-drenched streets and highways. Motorists are forced to avoid hydroplaning into oncoming traffic or sliding across “black ice” when the moisture freezes on the pavement’s surface.
Not only are drivers impacted, but the environment is harmed as the oils and other chemicals run off the non-porous asphalt into ditches before making their way into the waters of Puget Sound, creating what at times can be an ecological nightmare.
However, times are changing as pervious pavement, which unlike its impermeable counterpart, allows runoff and rain water to filter its way into the ground, before entering the stormwater management system, if it does at all.
The technology has been used on the East Coast for the past 30 years. Kitsap County is beginning to embrace it as the future for the county’s streets and sidewalks.
The Kitsap Homebuilders Association (HBA) is one of the leading advocates of the technology as it used pervious materials for a sidewalk at its headquarters in Bremerton.
“Pervious pavement is becoming one of the most used, low-impact development techniques to help manage stormwater,” Kitsap HBA Executive Director Art Castle said. “It helps recharge our aquifers and provides a very high level of natural treatment to a wide range of stormwater pollutants of concern including hydrocarbons and dissolved metals.”
The science clearly shows that pervious pavement is an effective means of protecting and improving water quality, Castle said.
While cities including Poulsbo have done projects using pervious pavement for sidewalks, the city of Bremerton has emerged as a leader in exploring new uses for the technology beyond sidewalks and parking lots.
“We’re looking to use it wherever we can,” Bremerton Public Works Director Phil Williams said. “Instead of spending millions of dollars researching it, we’re going to see where we can use it.”
The material was used in downtown Bremerton on Pacific Avenue between Fifth and Sixth streets as part of the city’s streetscape project, and it has been used for a parking lot at the public works headquarters facility on Oyster Bay Drive. There also is a 600-foot test area in East Park near Homer Jones Drive and Schley Boulevard.
The East Park developer and his contractor were apprehensive about using pervious pavement, so the city assumed all of the liability for the application as well as the responsibility for any cost difference, Williams said.
“It turned out wonderful and it requires less labor (than standard asphalt),” city streets supervisor Bob Tulp said, adding so far the city hasn’t received any complaints from motorists about the new surface.
One important aspect of the East Park application is that it has some slope to it, which is one of the questions that remains unanswered about the material’s applicability in different environments, Tulp said
Although his crews weren’t exactly keen on the use of the pervious pavement, once they poured it for the first time and saw first-hand how easy it was, Tulp said they have bought into the new paving effort.
Currently, the environmentally friendly paving material is mainly used for new streets, because it requires a different subgrade or road foundation to allow water to filter through the road bed into the ground, Williams said.
Otherwise the water could become trapped beneath the new road surface and cause the asphalt to crack when it freezes.
That doesn’t mean the city isn’t exploring ways to find ways to make that possible, he said. It just means the answer hasn’t yet been discovered.
With all of the application and research conducted on the East Coast, Williams said there are 20 to 30 years of research which have answered all of the major questions about the material, so it should be the preferred paving material of the future.
When it comes to the dollars and cents of pervious asphalt over the standard impervious asphalt used for the majority of paving projects, the cost per ton of material is slightly more for pervious than the standard material, Williams said.
But it requires less pervious asphalt by volume to pave a street or sidewalk than standard asphalt, so the cost by volume is about the same, he said.
“Right now it’s kind of a speciality product,” Wiliams said. “If everyone starts to use it, then the cost should go down.”
Currently, asphalt plants have to cease production of standard asphalt and adjust their machines to make the pervious asphalt, so the cost of the inconvenience gets passed on to the customer, he said.