Pervious Concrete, Inc.
Michael Bledsoe (President)
Pervious Concrete, Inc.
P.O. Box 1579
Snohomish, WA 98291-1579
The Smart Stormwater Solution
You know the stuff: impervious to water, channels runoff. But what happens when – without sacrificing strength or durability – water drains right through it? Consider if roads and driveways, sidewalks and parking lots could let rain wash directly into the ground, where it’s naturally filtered on its way to our aquifers. No runoff, no drains, no catch basins, detention vaults or piping systems. No kidding.
It’s called pervious concrete. And I think that it’s about to change how we build things in Washington.
That wasn’t the case just 7-8 years ago when the product first emerged in the Northwest. Land was less expensive then, and stormwater issues less at the forefront. When my engineer, Noel Higa of Higa Burkholder Associates, brought pervious to my attention in 1999, only a few forward-thinking scientists, engineers, mixing plants and governmental planners were looking into its viability – and no jurisdiction in Washington State had approved its use. That was then.
Pervious concrete is a two-part on-site stormwater management system consisting of the concrete pavement and a coarse gravel retention layer for stormwater storage. The system retains all water, including all pollutants, on site. And because the layers are porous, air is present and micro-organisms flourish, eating away pollutants and other non-desirable elements in the water.
Today, this system has been used successfully throughout most of the rest of the country, but it seems that a major test case was needed to demonstrate its advantages to our region. I never intended to be a pioneer, but I’m excited about what we’ve learned.
If the pervious is too wet or overworked during placement, the voids between the stone are reduced or eliminated, and it won’t drain. If the concrete is too dry, it’s impossible to get proper compaction for cross section strength and it will ravel or chip off. If curing procedures aren’t tightly followed immediately after placement and for up to 7-21 days thereafter, pervious concrete can fail. Problems will begin to show after the initial 7-day cure and will be evident within a month, and the only solution is to remove and re-install a corrected mix.
On the other hand, when the site is properly prepared, the mix is right and your installers are knowledgeable and certified, your potential for costly errors is significantly reduced.
Care should be taken to keep the surface free from silty or clay-like material, and to avoid clogging it with sand, topsoil, beauty bark and other debris. Chemical cleansers are not recommended; plan to use plain water to flush the pervious pavement voids. While the cleaning interval will depend upon the specifics of your location you can expect to sweep or vacuum 1-2 times a year to remove soil and debris.
- catch basins
- interior plat curbing
- oily asphalt