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Environmentally Friendly Asphalt Wins Sustainability Award

By Matt Rogers, Century West Engineering and Mike Faha, Greenworks






In order to deal with the large volume of stormwater runoff that would be generated from this large area of impervious surface, the design team utilized a porous asphalt pavement system and a series of vegetated swales to infiltrate 100 percent of the stormwater on site.
Photos courtesy of Century West Engineering and GreenWorks


Parking lots are a fact of life these days, and a large part of most large projects (including parks) as well. If you're going to be specifying a parking lot anywhere at all, however, you owe it to the planet to make it environmentally friendly--a not impossible task. This parking lot captures 100 percent of the run off. The planet along with the ocean is exceptionally thankful.

Winner of the Oregon APWA 2006 Julian Prize for Sustainability, this environmentally friendly parking lot uses vegetated swales and porous asphalt to infiltrate all the runoff, and cool that run off before it enters the Columbia River.






Above & Belowt: In addition to the cost and time savings, the porous asphalt and infiltration swales provide filtering of the stormwater and mimic the predevelopment hydrologic cycle which provide improvements to the overall water quality in the vicinity of the site.







The Auto Warehousing Corporation leases facilities from the Port of Portland to offload and process import cars arriving from overseas ports. Due to increases in volume, the facility at Terminal 6 (T6) was in need of expansion to resurface approximately 50 acres for auto storage. The Port hired Century West Engineering to help with the design of the improvements. During the pre-design, several design approaches were considered and the "sustainable" option made its way to the top. A preliminary site investigation was performed and confirmed that the site was suitable for a porous pavement stormwater management system.

With new methods and technologies it is always necessary to make a comparison to "the way it's always been done" to ensure that the public is not being asked to pay more to innovate. The two leading approaches that were analyzed were 1) a traditional pavement with catch basin collection system, pretreatment, and disposal into the Columbia River and to the City of Portland stormwater system and 2) a porous pavement and swale system to infiltrate 100 percent of the stormwater on site.

The critical issues that were considered through the analysis were the construction cost, impact on the environment, the desire of the Port's lessee to have the project constructed during the 2006 construction season, ongoing maintenance requirements and costs, and the City of Portland stormwater fees. Through the analysis it became apparent that the porous pavement and onsite infiltration option was the preferred alternative based on every criteria.

The improvements included surfacing of the entire 45-acre auto storage area plus an additional 6 acres of perimeter area for a total of 51 acres including fencing, landscaping, and lighting. In order to deal with the large volume of stormwater runoff that would be generated from this large area of impervious surface, the design team utilized a porous pavement system and a series of vegetated swales to infiltrate 100 percent of the stormwater on site.






The use of porous asphalt pavement also allowed the Port to avoid City of Portland stormwater fees that are calculated by the area of impervious surface on a site.


Century West Engineering partnered with GreenWorks, a Portland-based landscape architecture firm with a sustainable design focus, and Cahill Associates, a nationally recognized stormwater management expert specializing in porous pavement, to design the project. Amenities such as the project's rain garden and richly planted bioswales demonstrate successful collaboration between functional engineering and landscape aesthetics to manage complex stormwater issues.






The improvements included surfacing of the entire 45-acre auto storage area plus an additional 6 acres of perimeter area for a total of 51 acres which would generate a large volume of stormwater runoff.


Benefits from incorporating porous asphalt include:

  • Provides 100 percent onsite stormwater management
  • Shortened design, construction and permitting process
  • Lower annual operating costs, maintenance costs, and reduced stormwater fees
  • Improved stormwater quality, with groundwater recharge
  • Reduced impact on "storm surge" in adjacent waterways
  • In warm weather, allows stormwater to cool before entering the river.
  • $250,000 in cost savings from reduced permitting requirements and the fact that no stormwater system was necessary

Traditional impervious pavement was used in some areas to balance the cut and fill on the site and in areas where additional structural capacity was required. The runoff from the traditional pavements is infiltrated through the porous pavement section or on site swales that are incorporated into the landscaping for the site.

The use of onsite infiltration methods allowed for a significantly shortened design and permitting process that made possible construction during the 2006 construction season by avoiding the need for US Army Corps of Engineers or Oregon Division of State Lands permits for an outfall to the Columbia River. The use of porous pavement also allowed the Port to avoid City of Portland stormwater fees that are calculated by the area of impervious surface on a site. In addition to the cost and time savings, the porous pavement and infiltration swales provide filtering of the stormwater and mimic the predevelopment hydrologic cycle which provide improvements to the overall water quality in the vicinity of the site.






Traditional impervious pavement was used in some areas to balance the cut and fill on the site and in areas where additional structural capacity was required. The runoff from the traditional pavements is infiltrated through the porous asphalt pavement section or on site swales that are incorporated into the landscaping for the site.


Project Team

The importance of municipal leadership in sustainable design cannot be overemphasized and is the reason this project became a reality.

From conception, the Port of Portland staff encouraged sustainable design techniques and Century West Engineering, a leading NW consulting firm in sustainable design, worked to implement them.

Century West partnered with GreenWorks, a Portland based landscape architecture firm with a sustainable design focus and Cahill Associates, a nationally recognized stormwater management expert, for the design. The team worked to ensure that the design met all of the needs of the client at a competitive price and had the least impact on the environment.

For more information, please visit www.centurywest.com and www.greenworkspc.com







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December 6, 2019, 12:47 pm PDT

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