This is some interesting stuff. Apparently the surface water drains to an "attenuation layer" of rock subgrade. One article did address the drawbacks of freezing.
Could be the thing of the future...
[MEDIA=youtube]-iJP7DFt6AU[/MEDIA]
Heard of this from some loony LEED-crazy arkeetex. Reduces the need for redirection and containment of runoff. Well...that is... until...it gets choked with bits of matter much like a septic field eventually dies. Then you must solve the runoff problem.
I've seen it used a bit around here. There's a longish driveway at a commercial site a few blocks from me that's made of it. It looks a bit rough -- sort of like the concrete crew didn't know how to finish concrete -- but otherwise it seems fine.
We're beginning to design more and more of permeable concrete/asphalt parking lots. If, installed correctly, they work very well.
I'm a firm believer in this sort of application.
I was party to a 28 lot subdivision that had no underground stormwater pipework.
The road runoff was directed into underground storage beneath a grated kerb system that soaked into the beach shingle subsoil.
All house drainage was straight into the shingle.
Not quite same as this, but similar approach to water runoff.
Interestingly its previous life was a caravan park and a burst water main remained undetected for months until discovered through excess water usage.
Nothing showed on top as all water went straight into the shingle and onwards to the sea.
Thank you, Richard. I learned a new definition of the word 'shingle' today. Living about 700 miles from the nearest beach, I had never heard the term applied to anything but roofing material or the dreaded disease.
We are zero to 60 inches from bedrock anywhere close to where I live except for river bottom land. The project I mentioned above would be on a site with roughly 24-30 inches of clay above bedrock.
Actually HC has a point, and one that I wondered on.
Eventually with trucks and cars carting rubbish and worn rubber etc off tyres, I can envisage it getting clogged or impaired.
Not sure how maintenance would deal with that?
But like a lot of good technology, the negatives have been considered and answered.
Richard, post: 338224, member: 833 wrote: Actually HC has a point, and one that I wondered on.
Eventually with trucks and cars carting rubbish and worn rubber etc off tyres, I can envisage it getting clogged or impaired.
Not sure how maintenance would deal with that?
http://www.perviouspavement.org/downloads/pervious_maintenance_operations_guide.pdf
I believe that the way it's handled around here is that the permeable pavement is considered a part of the storm water management system and falls under the SWM management maintenance covenants that the owner/developer has to sign with the municipality. Just like any other BMP facility, if it fails then the municipality can force the owner to bring it into compliance...thus the incentive to keep up with the maintenance.
It appears to work in the same way as the equivalent surface in fast-drain asphalt. That's been used on several trial sections of motorway over here and seems to work very well without any signs of clogging. Shopping centres might be a tad different, given that the traffic is slow moving and lots of junks gets dropped. With fast drain asphalt the top surface seems to have very small pores, which only let in fine dust. I guess that the pores get bigger as you go down through the material, so effectively it will become self flushing.
Jim's right - the surface does seem a little less than smooth, but it's quiet enough at speed.
The video is very impressive.
chris mills, post: 338240, member: 6244 wrote: It appears to work in the same way as the equivalent surface in fast-drain asphalt....
I retired from the asphalt business over twenty years ago so my frame of reference may be somewhat dated..
We use to have a product we called "Open Graded Friction Surface" or OGFS. It was basically a shallow (>2") top dressing of specifically sized aggregate chips in an AC binder that allowed voids to form. We called it "popcorn" because it looked like a caramel popcorn ball.
Anyway, while it did allow surface moisture to drain a bit quicker (and provided a less than slick surface), it was hampered by its shallow depth in its ability to really "drain" a driving surface. Watching the video and seeing that pavement "drink" the water was really eye-opening for me.
If this continues to take off, the folks with a street sweeper with vacuum will become rich.
MA Stormwater Handbook recommends spraying and vacuuming up to 12 times a year. Last application I saw had a manufacturer recommendation of twice a year spraying and vacuuming. Ask any teenager: pores get clogged.
They used pervious asphalt in Provincetown. Looks like Binder and they do not appear to clean it enough... I have not been there during rain to see the immediate infiltration.
paden cash, post: 338242, member: 20 wrote: I retired from the asphalt business over twenty years ago so my frame of reference may be somewhat dated..
We use to have a product we called "Open Graded Friction Surface" or OGFS. It was basically a shallow (>2") top dressing of specifically sized aggregate chips in an AC binder that allowed voids to form. We called it "popcorn" because it looked like a caramel popcorn ball.
Anyway, while it did allow surface moisture to drain a bit quicker (and provided a less than slick surface), it was hampered by its shallow depth in its ability to really "drain" a driving surface. Watching the video and seeing that pavement "drink" the water was really eye-opening for me.
They used that on the last airport runway I worked on. Looked horrible, but drain the center of the runway OK, the water built up ear the edges when it tried to drain off the edge of the pavement. We called it rice-crispy treat pavement.
I can't see full depth stuff working in Northern climates, it would be a washboard from freeze-thaw in no time.
That vid is crazy though.
Looks like gap graded/open graded asphalt over a permeable base? Did somebody patent this combination?
I would question how well it would hold up with repeated heavy truck traffic. Seems like it would have the tendency to rut/shove since the underlying base lacks the fines to lock the coarse aggregate together.
imaudigger, post: 338259, member: 7286 wrote: ....Seems like it would have the tendency to rut/shove since the underlying base lacks the fines to lock the coarse aggregate together.
I was looking at that, too. In my mind they're probably using a polymer or epoxy binder rather than AC.
The relatively low compressive strength of an asphaltic mix design (that eventually ruts) is a 'give and take' to keep the asphaltic concrete from shearing under repeated loads. Hopefully this isn't an asphalt mix. What would happen to the road surface if there was an accidental solvent spill? The 'impervious' wearing surface of an asphalt road might be able to shed a bit of solvent or diesel (anything detrimental to it's existence), but to invite a solvent into its interior would be disaster.
paden cash, post: 338264, member: 20 wrote: I was looking at that, too. In my mind they're probably using a polymer or epoxy binder rather than AC.
The relatively low compressive strength of an asphaltic mix design (that eventually ruts) is a 'give and take' to keep the asphaltic concrete from shearing under repeated loads. Hopefully this isn't an asphalt mix. What would happen to the road surface if there was an accidental solvent spill? The 'impervious' wearing surface of an asphalt road might be able to shed a bit of solvent or diesel (anything detrimental to it's existence), but to invite a solvent into its interior would be disaster.
OK so it's not an asphalt product, rather a specialized concrete product.
In the video, the surface is black, which led me to believe it was an asphalt product.
imaudigger, post: 338269, member: 7286 wrote: OK so it's not an asphalt product, rather a specialized concrete product.
In the video, the surface is black, which led me to believe it was an asphalt product.
You know, the more I read, the less they tell me. Their website MDS (Material Data Sheet) is a generic P.C.C. sheet. Who knows what kind of junk they mix together??? Probably some "proprietary" industrial secret mix of goo-gunk...;-)
Here's a pdf brochure, but it doesn't really get into the materials.
paden cash, post: 338200, member: 20 wrote: This is some interesting stuff. Apparently the surface water drains to an "attenuation layer" of rock subgrade. One article did address the drawbacks of freezing.
Could be the thing of the future...
[MEDIA=youtube]-iJP7DFt6AU[/MEDIA]
We use a lot of permeable block paving in the UK instead of costly permeable asphalt as most councils prefer to have rainwater stay where is falls instead of traveling unnecessary miles in pipework. It makes sense when you think about it, if you make the attenuation tank large enough to compensate the rainfall in the chosen area then it reduces the cost of maintaining adoptable drainage. This also means the levels of the surface can be what ever you want within reason as the water doesn't have to run in to one destination like a gully.
spledeus, post: 338246, member: 3579 wrote: If this continues to take off, the folks with a street sweeper with vacuum will become rich.
MA Stormwater Handbook recommends spraying and vacuuming up to 12 times a year. Last application I saw had a manufacturer recommendation of twice a year spraying and vacuuming. Ask any teenager: pores get clogged.
They used previous asphalt in Provincetown. Looks like Binder and they do not appear to clean it enough... I have not been there during rain to see the immediate infiltration.
Exactly. Product is only as good as the maintenance and upkeep required to keep it functional. How many fancy storm drain systems have we all found that were way overdue for maintenance. I've mapped some high water flow / flooding events that our engineers found were ultimately caused by failing storm drain systems that were woefully under maintained.
Don't get me wrong I love the concept that we can create systems to allow water to permeate instead of run off, treat, and direct elsewhere but I foresee lots of Moss filled, sand filled, particle filled patches in the future for some of these projects. which I have seem a few here in the Pacific Northwest. My humble 0.02c
Jered McGrath PLS, post: 450516, member: 794 wrote: Exactly. Product is only as good as the maintenance and upkeep required to keep it functional. How many fancy storm drain systems have we all found that were way overdue for maintenance. I've mapped some high water flow / flooding events that our engineers found were ultimately caused by failing storm drain systems that were woefully under maintained.
Don't get me wrong I love the concept that we can create systems to allow water to permeate instead of run off, treat, and direct elsewhere but I foresee lots of Moss filled, sand filled, particle filled patches in the future for some of these projects. which I have seem a few here in the Pacific Northwest. My humble 0.02c
I would agree, we haven't been using it long enough to see the long term maintenance effects but I can imagine the tanks will be clogged with silt. We try using the cleanest aggregate possible to give the maximum drainage capability but give it 5,10,15 years down the line then surely the particles will work there way down eventually clogging the tank. I have only seen it used in light traffic areas however, industrial use for heavy plant really does take its toll on surface down to movement in the clean aggregate.
