Is the driveway so steep that pavement is necessary at all? Crushed stone would provide the porosity and infiltration enhancement without the expense of pavement. At some point, though, vehicle traction requirements will result in slippage of the stone. Crushed limestone packs well and would be most resistant. The geogrid pavement options mentioned by George have the same problem with traction. A grassy surface is slippery, especially when wet.
If you really need the pavement due to traction requirements, consider minimizing the paved area and putting in a french drain alongside. The stone in the drain will slow runoff, preventing erosion. Coupled with a retention pond or water garden, that may be your best option short of foregoing the drive in favor of steps and parking spot at road grade. Joel If you At 06:00 PM 8/10/08 -0700, you wrote: >Andrejs, > >I think you now have the steepest driveway on the street! > >The new parking lot down on Park Road off Cliff Street is paved with >porous asphalt and may be referenced in the Cornell University Dept. of >Horticulture report listed below. > >Tom Shelley is right about the slope limit of 6%. If the surface is any >steeper water will tend to run over the pavement instaed of soaking down >through the pores. > >The porosity of the subgrade and underlying soils also needs to be >considered. Generally parling lots have a sub-based of 8 inches to 12 >inches or more of crushed stone which can absord the rainwater coming >through the porpuse asphalt or concrete. Well-drained soils below the >sub-base also help. > >In this region there is a lot of concern over the long term ability of the >asphalt or concrete to remain porous, given the salt, sand and other stuff >dumped on our streets during the winter time. Of course in sub-freezing >weather and frozen ground pretty much shuts down the system during the >winter months. > >Given the relative newness of the technology in this region contractor >experience with successful applications is also a big question mark. > >There is a concept generically referred to as geogrid. Pre-fabricated >from either plastic or concrete, a geogrid consists of a series of 3 inch >by 3 inch openings created by a structural framework that supports the >weight of a vehicle. The geograid is placed in possition and the openings >are filled with soil and seeded to grass. > >These systems work well as temporary parking lots or for emergency vehicle >access roads across lawns where you do not want to see a roadway. I don't >know how steep you can go with them, however. A big question mark too is >the survivabilty of the grass in what would be a high-salt environment. > >What about going with conventional asphalt, but with some sort of bioswale >detention system at the bottom of the driveway or in another low spot on >your property. These "water gardens" are beginning to be used around this >region in order to meet new DEC regulations that mandate at least some >primitive treatment of stormwater runoff. They rely on a combination of >infiltration and plants to filter out runoff pollutants before the storm >water is discharged. > >Could you direct the runoff from the driveway into something like that? > >Good luck! > >George Frantz > > > > >--- On Sun, 8/10/08, Thomas Shelley <[EMAIL PROTECTED]> wrote: > >At 02:31 PM 8/9/2008 -0400, Andrejs Ozalins wrote: > >Does anyone have advice about permeable paving methods and/or local > >contractors who would know about and use such methods in driveway > >projects? > > > > >_______________________________________________ >For more information about sustainability in the Tompkins County area, >please visit: http://www.sustainabletompkins.org/ > >RSS, archives, subscription & listserv information for: >[email protected] >http://lists.mutualaid.org/mailman/listinfo/sustainabletompkins >free hosting by http://www.mutualaid.org _______________________________________________ For more information about sustainability in the Tompkins County area, please visit: http://www.sustainabletompkins.org/ RSS, archives, subscription & listserv information for: [email protected] http://lists.mutualaid.org/mailman/listinfo/sustainabletompkins free hosting by http://www.mutualaid.org
