Porous Paving
Porous Paving
(OP)
Does anyone know the CN used for porous paving.
Since the material is made of asphalt but behaves similarly to sandy soil, the determination of its CN is difficult to calculate.
Are there any formulas...
..or whats your best approach when designing porous paving systems under state regs for runoff and recharge?
Since the material is made of asphalt but behaves similarly to sandy soil, the determination of its CN is difficult to calculate.
Are there any formulas...
..or whats your best approach when designing porous paving systems under state regs for runoff and recharge?





RE: Porous Paving
Try these oldies:
http://ww
and
"Investigation of Porous Pavements For Urban Runoff Control" 11034 DUY 03/72 google it, I found a place that will sell you a copy for $10
If you hurry catch a seminar:
http://www.hotmix.org/view_article.php?ID=423
An article "Porous Asphalt The Right Choice For Porous Pavements" from the September/October 2003 Hot Mix Asphalt Technology magazine---see the link above for the NAPA
I ain't never seen a hearse with a luggage rack.-GS
RE: Porous Paving
and im sure DEP will accept a CN that high!LOL
.. but whats the point of using porous asphalt if your CN is similar to that of regular asphalt!!
..from the actual performance of porous asphalt and its ability to infiltrate water, its look more in the range of sandy soils..30-40..but thats all speculation. TR-55 wont accept CNs below 40 which makes modelling even more difficult.
RE: Porous Paving
I ain't never seen a hearse with a luggage rack.-GS
RE: Porous Paving
RE: Porous Paving
All that said, for a porous pavement or paver system you can compute a CN by using the old SCS formula where S = 1000/CN - 10, with S as the potential moisture storage in inches.
So, for example, if you have 12 inches of gravel to store water that percolates through the asphalt, at 30% porosity (typ. for gravel) the equivalent CN would be 73.5. At 6-inches of gravel it works out to 84.7 This doesn't account for underlying soils, which should improve the performance/lower the CN, but it is easiest to demonstrate the CN attributable to the gravel layer alone.
For comparison, the City of Portland BES drainage manual (page C-5) treats it as gravel and allows CN= 76/85/89 for porous pavement over hydrologic soils group A/B/C respectively.
I would go with one of these CNs and also make the case of at least doubling the Tc compared to conventional pavement.