Eco-friendly concrete will make local history


The Mirror

While the kind of high-tech concrete that will be poured for the parking lot at Historic Cabins Park in Federal Way isn’t new to environmentally sensitive areas in other parts of the country, it will be new here.

In response to concerns the wetlands near the cabins would limit the amount of land available for the type of stormwater drainage system normally associated with parking lots, city officials decided to try porous concrete for the 15-car parking lot as well as the sidewalk. They said it will reduce the amount and speed of water that flows from the lot into the wetland areas of the property.

It’ll be the first time the special concrete, which looks similar to a Rice Krispies treat, has ever been used in Federal Way.

Paul Bucich, the city’s surface-water manager, said the product has been used to good effect in other places he’s worked.

Impervious surfaces — roads, parking lots and rooftops — have long been associated with flooding and water pollution. Because the surfaces don’t absorb rainwater, the rainfall flows off in sheets, inundating surrounding areas with more water than can be absorbed. Runoff also has been blamed for introducing pollution, mostly from cars, into the ground and streams.

Bucich said it isn’t the quantity of water city officials are worried about at Historic Cabins Park, it’s the quality.

The cabins, a project of Historical Society of Federal Way, are located near the West Hylebos Park wetlands, and there’s little room to install treatment facilities to purify water leaving the parking lot before it gets into the environmentally sensitive wetland.

In addition to allowing rainwater to slowly filter through the lot, the pervious concrete planned for the cabins parking will help treat the runoff. Bucich said chemicals in the mix will react with some of the pollutants, neutralizing them. And healthy bacteria growing on the surface of the lot will eat other pollutants, he explained.

Pervious concrete is made with coarse gravel and rock particles that won’t clump together in the cement and become impassable. The concrete allows water to flow through the spaces between the larger chunks of rock. As polluted water filters through the pores, certain pollutants will bind to the oxygen in the concrete and in the soil.

While Historic Cabins Park is the first place in the city where the porous concrete is being used, Bucich said a similar composition of asphalt may be used in the widening of the South 373rd Street bridge.

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