permeable pavement

August 2, 2004 8:00 PM

New permeable pavement systems allow water to seep into and through the roadway surface, reducing run-off and recharging aquifers.
posted by stbalbach (22 comments total)

Many years ago, Phillips petroleum invented what was essentially a long roll of kevlar that could be rolled out on a road prior to asphalting. It would cost a lot, but the road surface would be far more durable, last many times longer, and be very resistant to harsh weather conditions.

Paving contractors across the US opposed the idea, as it would cost them billions of dollars in lost revenue. So it was never implemented, even though it would have been a godsend to everyone who uses the highways.

I mention this only to put perspective on the new idea. If it either cuts down on road maintenance, or if it requires additional capital outlays by paving contractors, they will vigorously oppose it. They like things just the way they are.
posted by kablam at 8:21 PM on August 2, 2004

My condo community is planning a massive drainage & paving project over the next year. We have very serious flooding whenever it rains, not only inside our community but also in the surrounding streets. This might be worth looking into, since the city's storm drains probably can't handle the runoff.
posted by mike3k at 8:36 PM on August 2, 2004

This is very cool... thanks, stbalbach!
posted by silusGROK at 8:36 PM on August 2, 2004

where does the extra water go? wouldn't flood-prone places still flood?

also, whatever happened to blacktop? i never see it anywhere anymore. it causes cancer or something?
posted by amberglow at 8:38 PM on August 2, 2004

where does the extra water go?

Into the ground below, with any excess heading toward the drainage ditches on the shoulder and from there into storm drains. Of course the point is that "extra" should become uncommon event because most normal rainfalls can be absorbed into the ground as nature intended.

wouldn't flood-prone places still flood?

Yeah, but less often, less severely, and less swiftly. So even if the ground right under the asphalt can't absorb it all, nearby ground and existing storm drains should be better able to take up the excess. Slower moving water is good because it's less likely to block up storm drains and cause backups, plus there's more time for emergency services to kick in to prevent property damage and injuries.
posted by nakedcodemonkey at 8:56 PM on August 2, 2004

ahh...thanks, ncm.
posted by amberglow at 9:06 PM on August 2, 2004

i second both kablam and nakedcodemonkey...not only would this be a godsend (and friendly to the environment and civilization - and thus, not expected soon) but it would create less of the problems water creates now amongst inhabited areas.

we can always hope, of course. oooh, or vote!
posted by NationalKato at 9:49 PM on August 2, 2004

on an additional read of the original link, it appears it would be at least $.50 - $1.00 more expensive than asphalt, per square foot.

oh well...
posted by NationalKato at 9:51 PM on August 2, 2004

NationalKato... I wonder what percentage .50¢ – $1 would be? And couldn't that be off-set, somehow, by grants from the good folks at FEMA or some other similarly-oriented governmental body?
posted by silusGROK at 11:21 PM on August 2, 2004

One dept surrender its funds to another dept? Hahahahahahahaha. Good one.
posted by nakedcodemonkey at 11:32 PM on August 2, 2004

If you want to see this technology happen, one had best inform his local politicians and city yard staff. A couple of form letters and a few pennies in postage ought to do it.
posted by five fresh fish at 12:31 AM on August 3, 2004

Good point. It doesn't has to start with the highways. Towns are covered in miles of pavement. For that matter, asking HomeDept/Lowes/et al to stock it and local contractors to use it can help jumpstart local use among homeowners. There are a lot of sidewalks, driveways, and walkways where pooling/running water is a problem too.
posted by nakedcodemonkey at 3:36 AM on August 3, 2004

Funny how 'new' stuff is. In Duesseldorf, Germany, at the convention center ('messe'), they have a huge parkinglot. It is covered with a revolutionary scientific material that allows water to seep into the ground below. Oh, wait, its covered in bricks with holes. Grass grows through, probably gets mowed occasionally. But its solid for all cars to drive upon.
posted by Goofyy at 3:39 AM on August 3, 2004

Thanks, this is great.
posted by sudama at 6:36 AM on August 3, 2004

this link seems to be to (mainly) gravel + bricks with holes, as gooyy says. but there have been attempts to make black-top permeable too (similar to teh permeable concrete). the aim was to reduce standing water on roads and so make them safer (less aquaplaning). the problem was that it tended to clog up, so it wasn't permeable after a while yet cost more (they don't address that problem here, as far as i can see).

(i don't see the advantage to "replenishing water levels" etc unless this is in an area that is otherwise solid concrete - if the water can run off onto dirt then it can replenish the aquifier just as easily. and in the case of this link, the surfaces are intended for low traffic/suburban/country use - this wouldn't be used through a city centre. so the environmental advantages seem like bull to me).
posted by andrew cooke at 6:42 AM on August 3, 2004

In 1996 dollars, the Federal Highway Administration has calculated the "weighted rural and urban combined" costs per mile of interstate highway to be $20.6 million. Assuming that the average interstate is 80 feet wide, that's an average cost of $49/square foot.

An additional fifty cents to dollar per square foot would be relatively negligible.

The cost per mile is significantly higher in the urban areas that most need this technology ($127 million for LA Freeways, $333 million in New York), thus the extra cost would be even more negligible in those areas.
posted by mosch at 8:40 AM on August 3, 2004

Am I crazy to think that if there's water running off blacktop, or percolating down through blacktop, then it would be smart to send that to a treatment plant to get the oily goodness removed instead of just letting it fall into the ground?
posted by ROU_Xenophobe at 8:46 AM on August 3, 2004

Rou - I think the idea is that the water percolating through would be somewhat filtered by the process, as opposed to the completely unfiltered runoff we currently have. We already filter water through sand.

As for highways, I didn't think these would be the primary concern. They tend to run through countryside where there is plenty of soil to take the water. The areas that most need permeable pavements are builtup urban and suburban areas. But I hope it will never become an excuse to pave over the Oak Ridges moraine, or areas like it.
posted by jb at 9:42 AM on August 3, 2004

Am I crazy to think that if there's water running off blacktop, or percolating down through blacktop, then it would be smart to send that to a treatment plant to get the oily goodness removed instead of just letting it fall into the ground?

You are crazy, ROU. All that petrochemical goodness mixes with the coolant, transmission fluid and all other foreign matter expelled by the automotive process should go RIGHT INTO THE SOIL so that later generations might enjoy it.

Not to say that runoff + current drainage is altogether better, but one can at least pretend that someting might be done at some centralized facility at some point in the distant future when we start looking at the ecological blight zones roadsides become.
posted by Ogre Lawless at 12:41 PM on August 3, 2004

Not to say that runoff + current drainage is altogether better...

as someone who once had the misfortune (and/or overwhelming lack of planning) to shoot the 'Hooch (v., to float down the Chattahoochee River in Atlanta in an innertube) right after a rainstorm, right past the drainage outlet for the Interstate 75 bridge over the river (which at the time seemed to be shooting runoff about six feet into the air), I must say that it seems far better to mostly filter the road goo out right at the roadway and leave it there than just to dump it directly into the river. Ick.

As for treating runoff, I'd like to hear if any municipality actually does this. Sure, systems with combined sanitary and storm sewers will end up treating some of the runoff, but I was under the impression that most such systems are at or over capacity, and a far more common occurrence is for storm drainage to overwhelm the system into dumping partially diluted sanitary sewage directly into rivers or creeks ahead of the treatment plant.
posted by Vetinari at 1:25 PM on August 3, 2004

Andrew Cooke:
i don't see the advantage to "replenishing water levels" etc unless this is in an area that is otherwise solid concrete - if the water can run off onto dirt then it can replenish the aquifier just as easily.

I do this kind of aquifer replenishment analysis for a living, usually as part of the environmental impact evaluation process for new housing developments. Typically, we assume that putting a residential area on top of previously undeveloped land will reduce ground water recharge by about 50% (this varies depending on residential density), with further adjustments for transportation corridors, schools, parks, etc.

Some of this can be made up later, as you say, if the water runs off onto dirt and recharges the aquifer there. However, this is heavily dependent on the design and maintenance of the storm water system. We usually recommend, as a sort of generic mitigation measure, that runoff systems be designed and maintained to maximize infiltration - but my company specializes in ground water, not surface water, so I don't have much opportunity for follow-up on those recommendations and I'm not familiar with all the design problems involved. But maximizing infiltration is hardly top priority in storm drain design, finding land for recharge/retention basins can be a problem (you can't just pour it onto any old dirt - rapid recharge of large volumes of water, which you need if you're trying to get a whole area's storm water into the aquifer via one or two basins, will only take place under favorable geologic conditions, i.e. sandy gravelly soils all the way down to the water table), and it's too easy for cash-strapped local governments to let basins go unmaintained (their effectiveness is severely limited by siltation). In any case, you're not going to recapture everything.

In some sense, I think you're right - in most areas, the benefit from increased aquifer recharge will be just piddly compared to the benefits from better flood control. But it's still a real benefit. Out here in Southern California, even suburbs are scrutinized for their impacts on water resources, so whether or not permeable paving is ultimately a cost-effective means of increasing recharge the idea is nothing to sniff at.

On preview: Vetinari: a few cities (Dana Point is one) are experimenting with stormwater treatment systems, dunno if it's standard practice anywhere.
posted by yami_mcmoots at 2:16 PM on August 3, 2004

thanks (just found this reply via the front page sidebar). i guess i was reading about this back in the uk, where there's a lot more concern about flooding than water levels.
posted by andrew cooke at 6:39 PM on August 5, 2004