City Lets It Rain Underground

Lots of rocks underlie the new sidewalks going in around Alice Keck Park Memorial Gardens and the new service road alongside Plaza Vera Cruz. In an award-winning program first introduced in the summer of 2011, the city’s Creeks Division has been removing asphalt and concrete and replacing them with concrete paving bricks that allow rainwater to soak into the layers below.

The rocks hold the key to eliminating organic matter that might fall from trees or drip from cars and trucks overhead. As water resources specialist Tim Burgess explains in a video you can see here, microbes that populate the layers of different-sized rock below the pavers consume pollutants that would otherwise run off into the ocean. The result so far has been complete absorption of rain into the ground, he said. The permeable pavers — which are laid with slight gaps between them to let water through — are rated to take one inch of rain per 24 hours, though the 2014 spring storms that dropped 5.5 inches over three days caused no runoff at the 2013 project sites at Oak and Stevens parks and the Westside Neighborhood Center.

The Creeks Division believes the higher installation cost of pavers compared to asphalt is more than set off by the longer lifespan of the concrete brick and the water infiltration. The new surfaces have been paid for, in part, with the additional 2 percent hotel bed tax approved by voters in 2000 to go to creek and water improvements. The test spot was MacKenzie Park’s parking lot, which had its asphalt removed and replaced with permeable pavers in 2011, as well as tree planting and other improvements. That project won a design award from the state, and the success encouraged the Creeks Division to expand its efforts.

The 2015 set of projects, Vera Cruz and Alice Keck, cost $1.05 million, 80 percent of which came from Prop. 84 money for public water systems. Also in process is the repaving of two parking lots at the city’s Public Works and Parks & Rec yards on Laguna Street, expected to be completed by December. For 2016, Creeks is looking to permeably pave the Quarantina Street area between the junior high and high schools.