The storm water management for our property was designed by a civil engineer to met what our city calls Tier 3 storm water management. The tiers are just dependent on the size of the project, and ours was a large one, so we got the highest tier.
The idea of storm water management is that you collect and filter all the water runoff on a property and / or create facilities that allow it to percolate into the ground. In our property, we have both.
The bio-filtration basin does al the filtering of the collected water. The permeable paver driveway allows water to flow through and soak into the ground.
Bio-filtration basin
Our city doesn’t have someone that is “qualified” to sign-off on tier 3 projects, so we had to bring in another civil engineer for the sign-off, and supervision of the bio-filtration basin completion. We had to wait to finish that part until the special inspector could observe.
The completion involved adding the plumbing (French drain at the bottom and overflow) and the materials inside. Here is the basin design.
First came 6 inches of large gravel, then filter fabric.
Finally, 24 inches of the special soil mixture, and this is what it looks like done.
We’ll probably build a lattice like structure out of some of the old redwood flood joists we pulled out of the house we tore down, as that 24″ drop is a little more than I like having in our front yard where our kids play. Add that to the list of pick-up projects that remain.
The theory is that the soil mixture harbors bacteria that can consume anything impure in any water runoff, so that only clean water will be put into the city’s storm water system (i.e., the street, which leads to storm drains).
In reality, we are collecting water runoff from the roof gutters and surface drains around the property. There really isn’t anything harmful in any water that comes from those; it just rain water. But rules are rules. Sigh.
Permeable paver driveway
I posted some entries on the development of the driveway (here, here, and here). The driveway, for the most part, seems like a normal driveway, despite being of the permeable paver variety. The gravel in the larger spacing between pavers does seem to come out from time to time, but I presume that will eventually settle down after what is going to come out, has come out. We’ll probably help it out a bit in a couple of weeks when we get the house power washed and windows cleaned; we’ll probably have them wash the driveway as well to get rid of the fine dust that remains from cutting pavers, and any dirt that got on them. I’m sure that will loosen up some more gravel.
Now both of these features are done, and signed off on.