Hot Mix Asphalt Technology - March/April 2008 - (Page 47)

San Diego Uses Porous Asphalt Lots for Stormwater Management By Chuck MacDonald Photos courtesy of Cahill Associates S an Diego County is known for attractive beaches, an idyllic climate, and numerous recreational pursuits. Local and state government officials are interested in preserving these attributes and protecting another precious Southern California resource –its water supply. One tool that they are using in that process is porous asphalt pavements. Recently the county completed its third porous asphalt pavement project as part of an experiment in keeping the water clean. Working with the California State Water Resources Board, the county completed a 40,000-square-foot parking lot in 2005, a 42,000-square-foot lot in October 2007, and a 27,000-squarefoot lot in November 2007. Each of the lots had a slightly different mix design with the October project consisting of two different mixes designed for greater permeability and the November project using a rubberized polymer mixture. In each instance, a pervious concrete lot was constructed nearby to provide an additional means of stormwater control. Based on the results of these lots, speciﬁcations could be proposed in the future by various government entities. The most recent project was done for a parking area with 64 parking spaces for Flinn Springs County Park. The parking area is located next to Los Coches Creek. “Water quality for the creek had been a concern,” said Brett Kawakami, a project engineer who works with the regional water management program. “The state found that the creek had a high level of contaminants in it and wanted to use the porous pavement as a way to keep impurities out of the water.” The design of porous pavements promotes water quality. The porous asphalt parking area creates a stormwater management system that promotes inﬁltration and eliminates the need for a detention basin. The stone is emptied on top of a geotextile fabric to begin building the foundation of the porous asphalt lot. This porous asphalt lot, built in 2007, used two different mixes designed for greater permeability. The porous lot has an asphalt surface with interconnected voids, allowing rainwater to quickly drain through the pavement and into the open-graded stone bed below. The stone bed retains the water brieﬂy, allowing it to percolate slowly into the soil below. The stone bed is of a size and depth that prevents the water from rising to the level of the asphalt. Statistics collected by Cahill Associates and universities are indicating that stormwater passing through Hot Mix Asphalt Technology – MARCH/APRIL 2008 • 47

Table of Contents Feed for the Digital Edition of Hot Mix Asphalt Technology - March/April 2008

Hot Mix Asphalt Technology - March/April 2008 Contents Chairman’s Commentary Industry News Top-notch Teams Overcome Obstacles to Build the Nation’s Finest Roads Ecological Award Winners: Environmentally Sound, Neighbor Friendly Safety Award Winners: Rewards, Reminders and Technology Roadway Safety Program Trains Workers Preventing Back-overs Is Serious Business Driving Through Work Zones: Be Careful! San Diego Uses Porous Asphalt Lots for Stormwater Management Legislative Messages Tools for the Trade Calendar of Events Index of Advertisers Advertiser.com NAPA Roadmap to CONEXPO-CON/AGG

Hot Mix Asphalt Technology - March/April 2008

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