Pervious driveways

[Planning Fool]

Does anyone out there know of pervious surfaces that could be used in driveways? I'm reviewing an application where the applicant wants to amend a plan to change the previously approved pervious driveways to asphalt driveways. The applicant states that the only pervious surface they know of is grasscrete and similar grass surfaces, but feels that would devalue the single family dwellings to be constructed on the property. Are they other asphalt like or any type of pervious surfaces that could be used that would not devalue the proposed dwellings?

[Richmond Jake]

You could try this one.

http://www.concretenetwork.com/pervious/being_used.html

I think I have a brochure at work with a reference, too. I'll look for it tomorrow morning.

[noottamevas]

They do make pervious concrete and pervious asphalt, but its specialized and not always readily available.
Maybe something in this thread will help
http://www.cyburbia.org/forums/showthread.php?t=22597

[Jeff]

I spec Charger Asphalt all the time.

I've found what you spec is generally up to the local Conservation District, Charger is acceptable to everyone I've ever run it by.

[luckless pedestrian]

be careful of using pervious paving for automobile parking - it can do the opposite of what you are thinking with stormwater management and aquifer protection (if that's your goal, that is) -

when the car leaks oil and other fluids while parked in a pervious driveway, then all that crap goes into the aquifer untreated -

so if they use it, make sure there is treatment for what seeps into it

[Jeff]

^most places require (or should) the area to be underdrained and routed to a basin nowadays.

[jordanb]

^most places require (or should) the area to be underdrained and routed to a basin nowadays.

How does that do any good at all? I thought the whole point of pervious surfaces was to keep the water out of the runoff management system.

[ssnyderjr]

How does that do any good at all? I thought the whole point of pervious surfaces was to keep the water out of the runoff management system.

Yeah, why not just require a catch basin in the driveway right under where your engine block is parked.....???

[noottamevas]

be careful of using pervious paving for automobile parking - it can do the opposite of what you are thinking with stormwater management and aquifer protection (if that's your goal, that is) -

when the car leaks oil and other fluids while parked in a pervious driveway, then all that crap goes into the aquifer untreated -

so if they use it, make sure there is treatment for what seeps into it

I've been told just the opposite. The sand base filters the pollutants before the runoff reaches the ground water. On traditional lots, the pollutants are concentrated to one discharge point and do more harm. So I'm told.
This site lists some environmental benifits of pervious pavements.

[Jeff]

How does that do any good at all? I thought the whole point of pervious surfaces was to keep the water out of the runoff management system.

The technology to filter out all the pollutants isnt quite there yet. Yes, that is the intent. Most of this still bypasses the basin. A common problem with these (so I've been told) is they either infiltrate too quick, and pollutants arent filtered, or the pavement becomes "clogged" and water gets routed to an "unclogged" area, saturating the ground, an underdrain will help move water away from the area.

I think there is a "trust factor" that just isnt there yet.

[solarstar]

We used to allow pervious concrete, pavers, turfblocks, etc. as a way to get under impervious surface requirements. However, we found that homeowners would eventually want to paint or otherwise "maintain" them and they would turn out to act just like impervious after a year or so. Most of the pervious concrete driveways I've seen look pretty bad after a few months in the Florida weather, so I understood why they are painted, paved over, etc.

[Planning Fool]

In this case, the goal is to reduce the amount of impervious area on the site and to provide and additional Low Impact Development (LID) measure on the site. The runoff form the driveway would be directed to a BMP facility (infiltration trench) proposed for the site.

Thanks for all your feedback, it is greatly appreciated.

[geobandito]

Does anyone know what the costs are compared to traditional paving?

[Jeff]

Pricey....I've seen more than double. Of course, this is always justified by the fact that the cost is offset b/c you can take alot of the volume out of your basin, reducing land requirements.

[Rem]

How does that do any good at all? I thought the whole point of pervious surfaces was to keep the water out of the runoff management system.

An alternative is to design first flush systems where the 'first flush' of runoff is directed to a treatment train and the later, more voluminous flows run into a more natural system. This generally requires a capture system rather than a dispersed infiltration system. Direct infiltration isn't viable in highly urbanised environments over here yet, though groundwater recharging following water quality polishing is gaining a lot of favour where geological conditions support the approach.